The previous section had just the bare basics of spacecraft design. This section has some of the fine details, as well as a few far-out science fictional concepts.


(ed note: this is science fiction, but some of the principles are sound. The most glaring fiction is the "traction drive" which is some kind of handwaving reactionless thruster forbidden by the laws of physics. It is described as "non-Newtonian", which is a dead giveaway that it is bogus science. Anyway that is why the described ship has no propellant tanks, which in a real spacecraft would dominate the design.

In the story, Starling and her parents owns the largest momentum tether in space, and make a good living at slinging cargo all over the solar system. Unfortunately the advent of traction drive ships is going to put them out of business. So Starling's foster father Gampy wants to invest in an unconventional new type of spacecraft as a business move.)

      “So, kiddo,” Gampy poked again. “Is a spaceship cost-effective?”

     “Yes and no. I mean, a traction drive isn’t that hard to fabricate. We could even print a couple dozen ourselves. There’s enough open-source matrices on the web, we’d only have to choose one, maybe adapt it for our needs, so it’s mostly a problem of raw materials and energy. And we wouldn’t have any problem fabbing new solar panels, three or four racks and probably a dozen new capacitor farms, so it’s only a problem of raw materials and we can cannibalize most of that from the junkyard. I’m guessing we could do it in 24 months or less. Worst-case scenario is 48 months. If we double up on the fabbers, I bet we could cut the production time to 16 months.”

     Ganny looked annoyed. Gampy covered his smile with his napkin. “What’s the no part, punkin?”

     “The life support system. We don’t have a hull. Unless you’re planning to cannibalize modules from the whirligig. But you’d never do that because the 'gig has to maintain a viability score of 350 or more for a crew of 20 and you won’t risk the numbers. I don’t know how big a crew you’re planning for the spaceship, but even a yacht needs a lot of hull space to be self-sufficient.”

     “Why do we need to build a self-sufficient ship?” Gampy asked.
     I gave him the look. The one that says “Why are you even bothering to ask?” It almost worked. He still gave me the “Come on, answer the question” gesture with his hand.
     I took a deep breath, my way of showing him how annoyed I was that I even had to explain. “Because,” I said. And folded my arms.
     Gampy laughed. Ganny smiled and said to him, “She’s got you there.”

     Over the next few weeks, Gampy had us all working on the question of life support modules. Not just me and Ganny, but folks on the Blue Team as well. They were the real crew and he said their input was the most important, because they were the guys who had to make it all work. How big a module would we need? Could we afford to construct one? Or would we have to buy a hull from the Martian Electric Boat Company? What would our requirements be? How big a crew would we carry? And what about passengers? Will our payload include cash-carrying customers? How many? And what level of service will we provide?

     The problem with that equation was that every time you added a warm body, you also had to expand the life-support systems to accommodate. Above a certain point—twelve is the magic number—there’s a certain economy that kicks in (I am unsure how realistic that is). But when you start adding passengers, you also have to add stewards, at least one for every twelve bodies. It adds up.

     There’s a lot to think about in spaceship design. No matter how good all your software might be, you still have to make hard decisions about how far you want to go, how much you want to carry, who and how many you want to bring along, how you’re going to keep everyone alive and comfortable and productive, and most important, how you intend to pay for it all. The irony of ship design is that there’s a corresponding relationship between size and comfort and profitability. The more comfort you want, the bigger the ship has to be. The bigger it gets, the more people and cargo you can carry. The more you carry, the more profit you make. So the ultimate question is how big a ship can you afford to build? It’s all about the life support module. The traction drive doesn’t care. It’s null-N, non-Newtonian (which is why this ship design has zero propellant tanks, while conventional ships are mostly propellant).

     So you can build a starter ship for five and later on add a second ring of cargo pods and maybe a couple passenger payload systems and you only have to add one or two or three traction cores to your basic unit. If you’ve designed for expansion.

     So Gampy’s real question wasn’t about whether or not we should build a spaceship. It was about what kind of spaceship we were going to build. And that meant he wanted us to think about what we were going to do with it after we built it. Where do we want to go? And what are we going to do when we get there? And after that, then what?

     We spent a lot of time on that question. We needed a keel—that was the easy part. But how long? We needed traction drives. But how many? We were already fabbing the fabbers that would let us fab the drives. We needed a ring to hold cargo and supply pods. But we still hadn’t decided on the life-support modules. How big? How many people are we schlepping? That was why Gampy started the discussion in the first place. He’d probably figured most of it out for himself, but he wanted to see if the rest of us would come to the same conclusions. It took us a while, but we did.

     The most cost-effective way to complete the ship was to buy a hull from the Martian Electric Boat company. It wasn’t the cheapest solution, but it was the fastest. It would save us at least 8 months of construction and testing, and that would get us to the return-on-investment point that much sooner. MEBC was popping out certified hulls two a month, whether they had buyers or not, it was cheaper to keep the assembly lines running, but they never seemed to have an overstock problem, they sold everything they produced. Besides MEBC had over a hundred years of quality control, their hulls had already logged several quadrillion kilometers without a fatality, while we’d be starting from scratch, learning as we went and probably making a lot of mistakes along the way. But, as Gampy pointed out, if we did build the hull ourselves, we’d know every inch of it intimately. Maintenance and repairs would be a lot easier. And faster. Because we’d have a much more personal relationship with vehicle integrity.

     Gampy said to think big, think outrageous. Imagine everything you think should be in the most perfect spaceship you can think of. Then he added, “You can have anything you want, but you can’t have everything you want, so start out thinking of everything and then decide what you want most.”

     At first, I started out thinking I’d like a bigger personal cabin. But then I had to laugh at myself because personals are always high on the list for dirtsiders. A starsider always thinks of the crew first, what makes the community space better for everyone. So I started thinking about a garden-lounge, a bigger recreation area, and a more luxurious galley—things that felt both luxurious and comfortable. Expansive but homey too. I was afraid to want too much because I knew that we had to be practical. I didn’t need anyone to tell me that.

     Every night, after we finished dinner, we sat around the table and presented our latest follies. That’s what we called them. Follies. In the traditional sense of the word. We had one rule—the first response to every idea had to be an appreciation of how outrageous it was and how ambitious it was. After we applauded each idea for its sheer impracticality, we would add it to the list of things we would want on an ideal spaceship. Everything was added to the list. Everything. Nothing was ever dismissed as too silly. Not even Gampy’s elephant or Ganny’s Hundred Acre Wood. Or my own Wild Strawberry Fields.

     Then, after we laid out the parameters of each astonishing addition, we’d give it to IRMA (the station's master computer) to run the math. How much lebensraum would it need? What kind of maintenance would be required? How much water? Oxygen? Power? Shielding? How much time would it take to construct? How much would it mass? How much payload penalty would we have to pay to include it? Balance all that against projected usage patterns. If we subtract it from the rest of the package, how much do we gain? Or lose? Everything was given a viability rating, a combined score, and we had a growing list of possibilities sorted by practicality all the way from must-have to violates-the-law-of-conservation-of-energy (from must-have to impossible-to-have). Ultimately, our final decision would be where to put the dividing line, the cut-off point between yes and no. From day to day, the maybe zone fluctuated in size. Sometimes it was a big purple haze, sometimes a sharp maroon line. Mostly it was just a shallow band of magenta.

     I knew what Gampy was doing, but I didn’t mind. It was a great game. He was teaching me to regard every choice as a location on a vast map of possibilities. Consider all the overlapping sets, consider the locus of optimal points. Look for a balance between imagination and sensibility, between desire and practicality, and ultimately between capability and cost-effectiveness.

     I turned seventeen and we began whittling our list. Practicality ruled. We didn’t discard any ideas because they were dumb, only because they were impractical. For instance, we could have a ship’s cat, if we wanted—we could afford the oxygen and water and food for a live animal—but it made more sense to fab a mechanical instead. Easier to train, a lot cleaner, and it would give us an extra set of mobile monitors that could get into small spaces; plus we’d get the same affectional bonus, and it would be a lot less expensive than having a tabby shipped out from Mars.

     The same standards applied to all our choices. Yes, we could have a bigger lounge, a genuine salon with its own attendant plumbing, but it would have to serve double duty as a theater and a dining hall and a gymnasium with all the attendant gear folded away into the bulkheads, unfolding as needed. Yes, personals could be larger, but that would mean a smaller crew and more dependence on bots and intelligence engines. That was a null-brainer—a smaller biomass-to-biosupport ratio (ratio of crew to life-support capacity) meant an expanded viability envelope (larger spare life-support capacity), and an enhanced payload window (higher payload mass that can be given a deltaV of x). Better for everyone.

     We had a keel. Actually, we had three keels in the junkyard, that mass of pods and leftover parts at the south end of the gig’s axis. We even had what was left of Gampy’s first boat. But it was obvious that Gampy wanted something bigger than that. Much bigger. He didn’t say it aloud, but he was thinking about the old Lysistrata (if you don't want to be either predator or prey, how about being a calculating lover?). He’d been talking about refitting her for years, ever since he’d claimed what was left of her for salvage. It made sense, the keel was still good and a lot of her internal harnesses still checked out, she just didn’t have life support any more. And of course, she’d need new engines, but we had seven decades of new technology to draw upon. We could use a lot of the existing mountings, and where we needed to, we could strengthen her frame with a bigger set of harnesses. We’d end up with a stronger ship than the original designers had conceived.

     Once we’d made that decision, the rest of the plan snapped into place like pieces of a jigsaw puzzle.

     We had fifty years of stuff hanging in the junkyard and at least another twenty years of resupply for all the old buckets still crawling around the belt. Plus a few items we’d bought on consignment for resale to option-holders. We had an assortment of power plants, all kinds. We had flywheels, solar panels, fuel cells, hot-and-cold fusion reactors, and even a couple of old turbines. Equipment? All kinds. We had pipes and pumps and all sorts of electronics and monitors and bots and sensors. And engines? Lord, did we have engines, more than enough to grab an asteroid and drag it home. We had six different kinds of blast engines and more than enough tanks of high-velocity propellants to drive them. And if that wasn’t enough we had solar sails, ion drives, plasma drives, mass-accelerators, and all the different kinds of spare parts necessary to repair those drives. We had all the stuff people used for throwing rocks around, all the stuff we leased to miners and comet-tossers and anyone else who wants to move a mountain. Best of all, we had the raw materials we needed to build at least a dozen traction units, and the keel of the Lysistrata was strong enough to hold them all. That’s why Gampy wanted us to think extravagant. We were going to build one of the fastest, most powerful ships in the system.

     I already knew what Gampy would say to that. “If it isn’t there, you haven’t created it yet.”

     (long ago when she was a little girl) Gampy said that I needed to learn how to swim, but I didn’t see the use of it. I wasn’t going anywhere I’d ever need that particular skill. But Gampy didn’t force the issue. Instead he made me a canoe. He found a bundle of plastic rods and tied two of them together at the ends. Then he put four cross-braces between them, arcing them out to form a canoe shape. Then he wrapped the frame with a wide sheet of transparent plastic wrap and a little bit of ribbon tape to hold the wrap in place. The boat was so light I could pick it up in one hand.

     …Ganny didn’t answer. She was still staring at the canoe. Abruptly, Ganny turned to face me. “Go start dinner. I’m going for a walk.” Translation: “I have to think about this.”

     Ganny came into the kitchen while I was mixing the sauce, I had a metal whisk that scraped round and round against the stainless bowl with a satisfying rasp. When Ganny came in, I stopped. She had a frown on her face. She looked annoyed. “I almost had it. I almost did. Damn.”
     “Had what?”
     She shook her head. “Nothing, it doesn’t matter anymore. I don’t have any…knitting needles.”
     “I don’t have any spokes.”
     “Spokes for what?”
     But Ganny didn’t answer. She was staring at…the whisk in my hand. She reached over and took it from me as if she’d never seen it before. She held it up before her eyes, still frowning, and spun it slowly between her fingers. A drop of green sauce separated itself and drifted lazily to the deck.
     “I am so stupid,” she announced. “I don’t need knitting needles at all.” She handed me back the whisk and bounced out.
     “Um, dinner will be ready in fifteen—” I called after her.
     “That’s all the time I need—”


     She waved at the display with her fork, bringing it to life. “See, here’s the problem, and I think Gampy knew it all along—what we have, we have a lot of. What we don’t have, we don’t have any. So whatever we do, we have to do it with what’s on hand. Because I suspect whatever we try to order, it probably isn’t going to get here (Gampy made some powerful megacorporations very angry at him, and they are out to ruin him). Here—”

     As she talked, the display assembled all of the various pieces of the proposed ship. The keel of the Lysistrata looked like a spear, but now with a shielded bulb instead of a point—the forward observatory and radar disc. The plasma drives and the accelerators were a thick bundle of thinner rods wrapped around the body of the spear. At the aft end of the schematic, the tractors clicked into place, looking like oversized feathers on a shuttlecock. “Now, we’ve got the raw material. We can spin out a radiation shield—” A large disc whirled into existence just ahead of the feathers. “The only thing we don’t have is a doughnut. A life-support system.” On the display, colored in red, a doughnut shaped module slid down the spear and parked itself just in front of the disc of the radiation shield. “Without a doughnut, we’re not going anywhere.”

     “We had this conversation already. Remember?”
     “Yes, sweetheart. But I wanted to restate the problem so you could see if I left anything out.”
     I shook my head. “This is where I always get stuck too. We don’t have enough raw material to fab a hull or deck plates or bulkheads.

(ed note: Reminds me of Gallagher's Glacier. He cannot afford the spine of a ship so instead he builds the structure of the ship out of an icy comet head for free)

     “Yes, we do. We just don’t know it.”
     “All we have is beanstalk cable. A lot of it.”
     “Yes, that’s what I said.”
     “You just lost me.”
     “Sorry, sweetheart. Usually, you’re half a jump ahead of me. There’s an idea that’s been rattling around inside my head for a while. Nobody’s ever done it, because nobody’s ever had to, but IRMA says it could work, the numbers all crunch.”
     I made the mistake of interrupting. “I was thinking maybe we could put the whirligig on the spear—?”
     “No, I already thought of that. The gig has too much mass. The torque would make it almost impossible to turn. Even if we throw away the ballast rocks.”
     “Put a gimbal in the keel? Put the engines on a swiveling axis—”
     “Still too much mass to push. And too much strain on the swivel joint. No, there’s something easier. Look—” She pointed at the display again. “We’re going to knit a spaceship. Without knitting needles.”
     “Huh—?” For a moment I thought she’d popped a seal. The strain of everything had finally gotten to her. I was genuinely scared for both of us. But no—
     Ganny pointed her fork at the display. “IRMA, show Starling how to knit a doughnut.”
     I watched as the display ran Ganny’s schematic. It wasn’t fancy, it was mostly blueprint, but it was impressive as hell. As soon as I figured out what she was thinking, I started getting enthusiastic. It was crazy, but it wasn’t that crazy. If we did it right, it would work.
     “Wow,” I finally said when I was coherent again. “I’d sure like to see the look on their faces when we arrive at Martian orbit with that.”
     “Or even Earth,” said Ganny. “You want to visit the big blue marble?”
     “Ganny, that’ll be the biggest ship in the ecliptic. Even bigger than the one Gampy designed. Bigger even than some of the ships going out on the long ride. You could plant a whole farm—
     “Uh-huh. That’s the idea. We’ll have to start cracking gas immediately. That’s another problem. How are we going to get enough air pressure to boil water for soup? But I have an idea on that one too. But I need you to study this. See if I’ve missed anything.”
     Ganny hadn’t missed much. There was only one big change that I suggested. “We need two doughnuts so we can rotate them in opposite directions—so they cancel each other’s torque (actually you do not need the extra doughnut IF the doughnut mass is a large percentage of the total ship mass). That makes us much more maneuverable. More important, that gives us two independent life-support modules. Remember what happened to the Ballista?”
     “That will double our cost—”
     “In materials, yes. But it’s not that much when you think about it. And we’ll have the bots for it, more than enough, they’re already growing in the fabbers. And they’ll work 24/7 with Saturdays off for prayers and maintenance.”
     “Probably more prayers than maintenance.” Ganny smiled. “But go on.”
     “There’s another advantage. We can stagger the construction, kind of like an assembly line. Once you configure a bot for a job on one wheel, you already have it configured for the same job on the other. As soon as it finishes its task on one doughnut, it goes to the other. Also, I think we should triple hull. At least. Maybe more. Maybe six times over the engineering requirements.”
     Ganny was following and nodding until I got to that last part. “Isn’t that a little extreme?”
     “Uh-uh. See, the thing is—if I were a dirtsider, I’d be terrified of this hull. Even not being a dirtsider, it gives me the cold shimmies. We have to have unquestionable hull-integrity. Everybody who hears about how this ship is built is going to think we’re crazy. At least until they think about it. It‘s like the first time someone said, ‘why not drop a cable from space and run elevators up and down?’ It defies common sense, or what passes for common sense on the marble. So we have to out-think their disbelief—what Gampy called their visceral-skepticism. And not just theirs. Ours as well. Like when they finally did drop a beanstalk, they had to make it six times stronger than their own math said was necessary. Just to be sure—in case they were wrong.”
     Ganny held my argument up to the light and looked at it carefully. She turned it over and over and over, much more than she needed to. But she understood what I was really saying. When you’re working with human beings, you’re not talking about rationality. You’re talking about belief systems. Everybody has one. Especially the people who believe they’re objective. So you don’t just build for functionality, you build for the kind of certainty that goes way beyond what people already believe. Triple hull. At least. Triple-triple hull.

     Finally, Ganny nodded. “It makes sense for a lot of reasons, especially the ones we won’t know about until afterwards. Let’s run it through IRMA and see what she says.”
     We topped it off with a dollop of gleeful dishing at the expense of MEBC. And then some exuberant fantasizing. After all, if we could do it once, we could do it a many times. We could even go into competition with MEBC (Martian Electric Boat Company, they make habitat modules. And they tried to bankrupt Starling and Ganny). Our materials cost would be significantly less, our production lines could be faster, our per-unit cost would be cheaper, our modules would have no size limitations—

     See, the problem was that once somebody does something, everybody else thinks that’s the only way to do the same thing. Spaceship design is still stuck in the twenty-first century. Sure, the individual bits and pieces of technology have improved, the materials are better, but everybody still uses the same old-fashioned design. Build a long strong keel. Attach engines at one end, life-support doughnuts at the other. Add supply pods, equipment pods, ballast pods wherever they fit. Your ship looks like a cluster of grapes on a stick, with solar wings and heat radiators sticking out wherever.

     Most ships start at the bottom of a gravity well. Earth or Mars. Wherever you can put down a factory without the neighbors complaining about the noise. All the different parts are manufactured in pieces, sent up the beanstalk, and assembled in space. So they’re made—designed that way—to withstand gravity as well as thrust. If you build the pieces in space, you only have to design them for thrust. And if you’re never thrusting more than a fraction of a gee, your engineering can be a lot different than if your pods are coming up the elevator at a thousand klicks an hour (300 m/s).

     In space, you design for tensile strength and connectivity and hull integrity. You don’t have to waste a lot of mass on heat shields and heavy plating and cross-bracing and all the other things that gravity and atmosphere demand. That’s what Ganny figured out. Looking at the little canoe that Gampy put together for me in an afternoon, Ganny started wondering, “Why can’t we build a life-support module the same way?” Build a frame and wrap it in plastic sheeting. Or even ribbon tape. Instant hull. Cheap. Easy.

     What stopped her wasn’t the plastic, but the frame. We didn’t have one. We didn’t have the materials to build one. We’d need to build a great big wheel. Very sturdy. One that would rotate and withstand the strain of centrifugal “gravity.” You lay down floor plates and then you put the bots to work, fabbing reels of plastic and wrapping it round and round and round until you had enough layers to feel secure. But we didn’t have a frame and we didn’t have the manufacturing capability to fab one. And even if we did, we still didn’t have hull plates or the way to build those either. Constructing the fabbers to build either of those things could take as long as three years, maybe as much as five. And we’d still need raw materials. Cannibalizing the junkyard—we’d have to build a shredder and a refinery and all kinds of separators and at least three dozen bots to run the equipment. Not cost-effective. Gampy was right. And probably somebody at MEBC had done all the same math and figured out how to put us out of business with a single phone call.

     Then Ganny saw the whisk in my hand and she saw something nobody else saw. As Gampy would say, they didn’t see it because they didn’t believe it. But Ganny was already halfway there. We didn’t need to build a rigid frame. We could spin one. It was so simple it was embarrassing. What did we have a lot of? Cable, ribbon tape, plastic wrap. And more cable. Lots of cable. Enough cable to rebuild the whirligig several times over. Enough cable to rebuild a couple dozen whirligigs, which was Gampy’s original idea. Don’t go out mining for gold, just sell shovels to those who do. You’ll make a lot more money.

     Think of a sling. Whirl it fast enough and centrifugal force will keep the sling rigid for as long as you spin it. Just don’t stop spinning.

     Start with a hub. It looks like the rim inside an automobile tire. Put the hub on the axis of the keel. The keel of the Lysistrata already had a half dozen hubs in place from its previous incarnation, so we were already set for the next step. Attach one end of a long cable to the top rim on the hub, attach the other end of the same cable to the matching spot on the bottom rim. Attach some weights to the cable, space them as far apart as you want your wheel to be thick. Do this at least three or four dozen times until you have looping cables all the way around. Kind of like the kitchen whisk, only loose.

     Now you spin the hub. Get it rotating nice and fast. As the whole thing whirls, the keel-weights fly outward to their farthest possible orbits, pulling the cables rigid. Now each cable becomes two spokes with a connecting arc. The keel-weights (mostly) flatten the arc between the spokes, and all the cables, spaced equidistantly around the hub, provide the spokes for a great big wheel. Keep the whole thing rotating and you have a rigid framework for your LSM (life support module). With no stiff spars at all.

     Now send spider-bots down the spokes and have them start stringing cables from spoke to spoke, start at the midpoint of each arc, and the weights as well, because you’re going to use the tension to control the final shape. Connect everything with ribbon tape. Lay a roadbed. It’s a suspension bridge without towers, everything joined at the center, turning round and round, and held in place by centrifugal force (Larry Niven said his famous Ringworld mathematically is a suspension bridge with no end points). Keep stringing cable and ribbon tape. Work your way up the spokes, connecting everything. Round and round all the little spiders go, crawling patiently around the circumference of the wheel, until they’ve woven a whole great web of wires, a gigantic whirling hoop. Now you start laying down your plastic wrap, unrolling it round and round and round just like the cables and the ribbon tape.

     Okay, all that makes it sound a lot easier than it really is. Actually, you have to construct five concentric wheels simultaneously, each one nested inside the other, like little Russian dolls. You do that so you can have multiple levels of gravity, just like the whirligig; but also because that gives you the security of five bulkheads between you and vacuum.

     And remember, you have to do it twice, because you need two LSMs. And a third one too—the “machine shop.” But once you’ve got everything turning, once you’ve got your fabbers turning out cable and tape, the whole process is automatic. The spider-bots are patient and uncomplaining. They only come back in when they need another reel of cable and fresh power cells. As they run the webs, a second set of spider-bots installs hatches, monitors, sensors, electrical harnesses, fiber-optic cables, pipes for plumbing and ventilation, accessibility tubes, pneumatic delivery systems, dumbwaiters, elevators, all of the hidden systems necessary for maintenance and viability.

     It sounds like a lot, but once you’ve got those big wheels turning, you can see how much there is and how little there is, both at the same time. With all the lights on, they look like grand empty outlines, amazing and awe-inspiring, every detail of the still-unbuilt wheels delineated like schematics brought to life, rotating proudly against the diamond stars. All the supports and cables, the spokes and interconnections, all the plumbing and wires, the lights and harnesses, everything connected together, rolling and turning, two of them, identical, rotating in opposite directions, but visibly syncing up every 10 degrees in a bright double vision that collapses into a momentary eclipse of brightness and then unfolding again like a kaleidoscope as they continue spinning past (three-dozen cable-spokes is 36 spokes. Distributed evenly in 360° means a spoke every ten degrees). A gigantic, flickering, headache-inducing, psychedelic display.

     Meanwhile we were focusing on the next step of construction—how to wrap the wheels, how to panel the decks and the bulkheads. The problem wasn’t that we didn’t have a good way to do it, the problem was that we had too many good ways. We were looking for the sweet-spot, what would work best and what we could afford and what we could accomplish quickly. There’s an old saying in engineering: “Good, fast, cheap. Pick two.” We were trying for all three.

     Now, about those decks and bulkheads. That’s what made Ganny laugh the loudest. After all those many times she said she’d never sit down and knit, not for anyone, now she was knitting the biggest longest scarves that anyone in the whole ecliptic had ever knit. At least a couple dozen.

     Well, actually she didn’t do the knitting, the knitting machines did, back and forth, back and forth, shuttling way too fast to see what they were actually doing on each pass, but each time back and forth, back and forth, adding a new row of intricately looped fiber. Back and forth they went, hissing and buzzing, clicking and clacking. Back and forth, patiently rolling out huge rolls of material, endless rolls, great barrels of triple-knit weave that would ultimately become the floors and walls and ceilings of the wheels.

     Okay, yes, the machines did the actual knitting, not Ganny—, but Ganny designed the system, so the knitting was hers, all hers, and as all the different cylinders of fabric began to stack up in the “machine shop,” Ganny’s grin grew broader and broader. “Yes, this is going to work. This is really going to work.”

     Let’s say you’re making cloth. The obvious way is to weave it over-under-over-under, the material is kinda like a checkerboard. But it’s not the strongest fabric you can weave. If a single strand breaks, you’ve got a place where there’s extra stress on surrounding strands and that’s where the rip is most likely to start. No, it’s a lot stronger to knit your fabric. Or even double-knit. Or triple-knit. Because you’ve got your thread all hooked around and through itself, in and out and under and over, to make an intricate fabric of multiple interlocked loops. If you knit nano-fiber, the result is an air-tight material so fine you can’t even feel the weave. Well, it’s not really air-tight, it’s just that the knit is so tight that most large molecules have a real hard time squeezing through; we use that a lot for starsuits. And graphene too. If you knit micro-fiber, you get a soft silky fabric loose enough to breathe and wick away moisture and feeling really nice against your skin, great for underthings, and we can sell it as space-lingerie in our fictional hotel. If you knit standard carbon-fiber, you get a larger scale of knit, lightweight and very resistant, it doesn’t wear out. And so on. All the way up to titanium cable, which gives you a very impressive chain mail. You can knit anything, whatever size yarn or wire you want. You could even knit elevator cables if you needed to, if you needed a net strong enough to catch an asteroid. Or an Enterprise fish. But probably not a giant space amoeba. If we ever met one, it would probably ooze through the mesh.

     Ganny set the bots to work weaving all these different knits, because she needed at least six different scales of tensile strength: micro-strength for the smallest of assaults, macro-strength for major events on the hull. She had IRMA run all kinds of simulations, and eventually we decided to panel the wheels with lasagna—multiple layers of knit, each layer pumped full of honeyfoam.

     Honeyfoam is a generic term for quick-hardening poly-crete. It creates a layered, bubbled substance; if you mix it right and spray it right, you get uniform-size bubbles and an internal structure like a honeycomb. Very strong. Each bubble stays liquid inside. If something punctures the foam, the liquid bubbles out and reseals the foam just as good as new. Plus honeyfoam also helps against cosmic rays and radiation.

     A lot of dirtsiders think that metal plating is the best defense against little cosmic bullets, but it isn’t. A cosmic bullet hits a molecule of metal and it splits off gamma radiation, which is even worse. Instead, we can dope the honeyfoam with particles of magnetized plastic and when the wheel spins, it creates a strong enough magnetic field to deflect a lot of radiation. Not that the stuff doesn’t respond to magnetism, but if we can reduce the overall exposure to what Ganny calls “sea level on a cloudy day,” we’re okay. Flip the polarities on the second wheel, the one that spins in the opposite direction, and the two magnetic fields overlay and combine instead of cancelling each other out.

     Anyway, we let all three wheels spin for a few weeks to make sure they were stable, no wobbles, nothing seriously off-balance, all the stresses and strains equalized across the frames, everything working, boards green, confidence high, viability optimum, 110 percent, five by five, lock and load, surrender Dorothy, and metaphors be with you. Everything.

     A week later, we started carpeting. First, the plastic wrap. The bots trundled round and round the circumferences, laying down “road-beds,” the bottom decks of the wheels, unrolling layer after layer of see-through plastic wrap, until we had a surface nearly a centimeter thick, much more than we really needed for this layer.

     That’s when we got serious with all the stuff we didn’t want anybody getting a good look at. Ganny didn’t want people seeing what level of technology we could apply to the problem. What we had was graphene. Large sheets of it. Rolls of it. Lots and lots of it. Enough to wallpaper a planet.

     Graphene is one of the strongest substances ever manufactured. It’s another one of those things you can do when you convince carbon atoms to behave themselves and line up nice and orderly in one-atom-thick sheets. You could stretch a piece of it over the top of a coffee cup, suspend a pencil over it, put a three mega-kilo cargo pod on top of the pencil, and the graphene still wouldn’t puncture. Roll it up tightly in tubes and you have cable strong enough for a beanstalk. Or a whirligig.

     The best graphene is fabbed in a null-gee vacuum, shielded from intense solar energy, but even way out here in the belt, you still get microscopic flaws and cracks, so if you’re going to make cables out of it, you have to interleave multiple sheets as you roll them up. We had a lot of graphene rolls, we fabbed it even when we didn’t need it and sold it to anyone wanting to build a beanstalk or a whirligig or hang a tent over a crater.

     In its sheet form, graphene is good for strengthening all kinds of things, and if you could mass produce flawless, uniform rolls of it, it would be one of the best construction materials in the universe. But so far, nobody has managed to produce more than a few dozen meters of flawless. So you have to wrap it in multiple sheets. Or in our case, just keep wrapping around and around and around. And around. The graphene foundation was necessary for what came next.

     Now, we laid down layers of nano-knit and carbon-polyfiber-knit and all the others, and of course more graphene sheets too, balancing them for strength and flexibility. That’s another thing dirtsiders don’t understand understand about engineering big things. You have to allow for expansion and contraction, stretching and shrinking, crinkling and cracking, material fatigue and fabrication flaws, and then add a dollop of wiggle room for bouncing and bumping. So we balanced heavy-knit and tight-knit and sheets of pure graphene. We sprayed honeyfoam over and under and inbetween everything, and if anything ever stretched or flexed or cracked enough to break the foam, the foam would just fizz for a second, harden, and repair itself. And of course, we also laid down grids of monitors between the layers to measure temperature, radiation, proximity, vibration, movement, flex, stress, pressure, deformation, internal sound levels, impact, leakage, contamination, material decomposition, and the possible presence of ethereal heffalumps and other boojums. And anything else we could imagine. Because we were designing this ourselves, we were going ultra on the specs. And then as all the internal monitors became active and we certified them, we began growing the matrices for an IRMA installation. Our ship wasn’t going anywhere without a brain.

     Then for a long time, it felt as if nothing was happening. The big wheels kept on turning, the spider-bots kept unrolling. They pushed the cylinders of fabric rolled around and around the decks like prehistoric dung beetles pushing giant dinosaur turds. Other spiders manipulated huge cones, unwrapping great arcs of material around the spokes. Very quickly, the wheels stopped looking like outlines of themselves and started looking like…wheels. And whatever was happening inside, the view rarely changed from one day to the next. We knew that progress was happening, we just didn’t feel it.

     So we concentrated on other things. We started moving all the necessary support pods into place both above and below the wheels. Raw supplies, processed food, oxygen and nitrogen tanks, gas-scrubbers, fabbers, all kinds of raw material for the fabbers, maintenance and repair equipment, spare bots and replacement parts, anything and everything. We cleaned out the closets, the pantries, the garage, and the attic. Then we started moving the life-support systems, too. Aeroponics, hydroponics, meat farms, more oxygen and nitrogen tanks, more gas-scrubbers, more fabbers, solar storm bunkers, lifeboat pods, emergency life-support units, starsuits, rebreathers, hazmat suits, O-masks, airlocks, and more bots. Did I leave anything out? If I did Ganny would catch it. Whatever she missed IRMA caught. And of course, we had all the checklists too. We had a century and a half of modern shipbuilding to draw upon and all the associated recommendations, requirements, specifications, tech manuals and certification sheets. We were pumped.

     Inside the third wheel, our engines were taking shape too. The wheel itself was going to be our radiation shield, protecting us from the emissions of our own drives. There wouldn’t be much radiation and most of it would be directed aftward, but just the same, starside you minimize every risk, to yourself and to everyone you approach.

     The bottom wheel was made of overlapping leaves, not linked at the sides and permanently connected only to the top rim of its hub. Just before launch, we’d release all the cable connections on the bottom rim and the wheel would unfold like a gigantic flower, opening out to become a great grand dish and revealing our engines to space. We’d keep it spinning for a few weeks while the spiders crawled across it, anchoring the separate petals along their edges, linking them together and forcing them into a gently curving concave shell. Then we’d spray them with heavy-honeyfoam, both inside and out, to give them permanent rigidity. During that whole time, we’d be running final tests on each of the engine tubes. When all that was finished we’d unroll the primary traction drives, big feathery things that would look like three gigantic oversized pistils sticking out of a very small flower. When everything was finally in place, the ship would look like a gigantic shuttlecock with a sharp pointy tip. We’d have the biggest traction engines ever built and 9 small secondary units spaced within.

     If we could avoid any serious missteps, then eight weeks after launch we’ll have tested and certified every major drive component. Allowing for the usual last minute unforeseen, unpredicted, and unexpected adjustments, calibrations, fixes, and repairs, the entire ship would be all-green in fourteen weeks. I would be nineteen and we would be starborne. We’d have not only the fastest ship in the system, we’d also have the most comfortable crew quarters.

     But right now, we had to finish attaching, loading, and balancing the supply and equipment pods that clustered the length of the keel. And after that, we had to build and install the gear to make the habitat wheels viable. Neither wheel had yet been certified as spaceworthy, we hadn’t even run preliminary pressurization tests, but if we started viability construction now we could minimize load-up time later.

     “It probably won’t be a long conversation. You’ve been crunching numbers for six months. I’ve been waiting for you to tell me what we’re doing.”
     “I thought you’d already figured it out. Saturn.”
     Ganny raised an eyebrow. “Saturn?”

     “We don’t have enough gas to fill the wheels. We can only pressurize them to fifteen kilometers. Even if we enrich the O-mix, even if we wear O-masks, we’re still going to have side effects—like pre-packed meals, because we can’t do any real cooking where water boils at room temperature. We can’t steal gas from the gig, that’s not fair to Spinward, it violates our deal with them, and it isn’t practical to crack gas from an asteroid because that’s another year or more sitting around waiting before we can launch. And we lose our window to go collect our stolen goods. So instead, we live in the pods for a couple weeks while we ship out to Saturn, collect ice from the rings, crack it for gas, fill both centrifuges and pressurize them to sea level. Isn’t it obvious? And while we’re out there, we grab as big a berg as we can and bring it back. Enough to fill the new lake at Luna City—it’ll be cheaper than lifting the same mass up from Earth and we can show a profit on our very first trip.”

     After dinner, Ganny said, “Okay, here’s the part I did without checking with you. You can get mad at me later.” She opened a schematic on the big display. She didn’t say anything. She just let me study it.

     “Hm,” I said. I pointed. “Rail-guns. Needlers. Laser-cannons. Missile launchers. Particle beams. Silent screams. Pain projectors. Funny-foam. Tanglefoot fields. Spider-nets. Stunners. Disruptors. Isn’t this a little overkill for pirates? Are we going to topple a government? Or are we just going to war against the Klingons?”

     “Yes,” she said. “We’ve had a pretty large arsenal for a long time, punkin. We’ve only needed it once, but that once was justified. We’ve kept most of the defensive gear hidden in the core of the junkyard, the rest is very well disguised and scattered in the most unlikely places. Spinward doesn’t know about this stuff, at least I don’t think they do, and I’m not leaving it behind for them. So as long as we’re schlepping it, we’re going to make it cost-effective.”

     “Ganny, this is a warship. Just pulling into orbit will look like a threat to some folks.”
     “As long as we don’t look like a warship. As long as we don’t make noises like a warship. As long as we pretend we’re not, they’ll pretend too. Because it’s convenient not to have large crowds of people running around in a panic.”
     “But—if we install all these weapons, aren’t we behaving the same way? Just as paranoid as they?”
     “Absa-tootley,” she agreed. “There’s the paradox. You want to leave any of this stuff behind?”
     “Hell, no. But I think you might want to mount the heavier weapons closer to the center of gravity to take some of the stress off the keel.”
     “Already considered that. It reduces our coverage. And the gear isn’t mounted to the keel, it’s mounted to a framework that clamps around the keel. It actually adds to the longitudinal strength. Oh, and I’ll want you in the fire-control simulator at least an hour a day from now until launch.”

     Two hours before the fast ship was scheduled to arrive, I finally spoke up. “Ganny? Whatever he offers…we can’t accept it.”
     “If he knows we’ve built a ship, then he’s gotta be smart enough to know we’ve armed it.”
     “So he wants to hire us as muscle.”
     “That is a possibility, yes.”
     “Ganny, he’s bringing a Corporate Letter of Marque. It’s the only thing that makes sense. Hiring us as independent agents to do somebody else’s dirty work. We’d be privateers—pirates!”
     “Arrrgh,” said Ganny. “And it isn’t even the nineteenth of Septemberrr yet.”

From GANNY KNITS A SPACESHIP by David Gerrold (2009)

How Big Is It?

The Polaris is 792.6 tons of propellant and 396.3 tons of everything else. How big is this, exactly?

When comparing the spacecraft to other vehicles, just use the "everything else" value, ignore the propellant mass. This is because few earthly vehicles have total masses dominated by fuel mass as much as rockets are. How does 396.3 tons stack up?

Rick Robinson notes that is pretty small compared to "wet-navy" vessels. It's under the size of a coastal corvette. But compared to aircraft, it's huge. A Boeing 747 is only 180 tons empty. If you want to get an idea of other sizes, go check out Jeff Russell's huge Starship Dimensions website and Florian Käferböck's impressive Rockets and Space Ships Size Comparison.

0Human Being1.77 meters/5.8 feet
1Giraffe6 meters/20 feet
2City Bus12 meters/40 feet long
3Small Orion Drive ship21 meters/70 feet
4Millennium Falcon35 meters/115 feetStar Wars
5Polaris43 meters/140 feetTom Corbett, Space Cadet
6Moonship44 meters/144 feetChesley Bonestell,
Conquest of Space
7Luna46 meters/150 feetDestination Moon
8Arc De Triomphe50 meters/164 feet
9Orion Drive Mars
Exploration Vehicle
50 meters/165 feet
10United Planets Star
Cruiser C-57D
51 meters/170 feet wideForbidden Planet
11Nautilus51 meters/170 feet long
12Space Shuttle stack56 meters/180 feet
13Absyrtis60 meters/197 feetG. Harry Stine,
Contraband Rocket
14Boeing74771 meters/231 feet
16Ferry Rocket81 meters/265 feetCollier's Magazine,
22 March, 1952
17Statue of Liberty93 meters/300 feet
18DE-51 Destroyer Buckley93 meters/306 feet
19Saturn V111 meters/363 feet
20DY-100 Botany Bay92 meters/302 feetStar Trek
21California Redwood112 meters/367 feet
15RS-10128 meters/420 feetAndre Norton Star Born
22Discovery140 meters/459 feet2001, A Space Odyssey
23Romulan Bird of Prey131 meters/430 feetStar Trek
24Great Pyramid of Cheops139 meters/455 feet
25Oscar class submarine155 meters/509 feet
26Galactic Cruiser Leif Ericson168 meters/551 feetLeif Ericson Model
27Washington Monument169 meters/555 feet
28Klingon D7 battlecruiser228 meters/750 feetStar Trek
29LZ-129 Passenger
Airship Hindenburg
245 meters/804 feet
30BB-62 Battleship New Jersey270 meters/887 feet
31NCC 1701 Starship Enterprise289 meters/950 feetStar Trek
32Eiffel Tower300 meters/984 feet
33CVN-65 Carrier Enterprise342 meters/1,123 feet
34Empire State Building443 meters/1,454 feet
35Al Rafik102 meters/335 feetAttack Vector: Tactical
36Tachi/Rocinante46 meters/151 feetThe Expanse
3710 Story Building30 meters/98 feet
38International Space Station109 meters/358 feet
39X-Wing Fighter13 meters/41 feetStar Wars
40Eagle Transporter31 meters/100 feetSpace 1999
41Shuttle Orbiter37 meters/122 feet
42Type S Scout39 meters/128 feetTraveller RPG
43Serenity58 meters/190 feetFirefly
44DDG-90 Destroyer Chafee155 meters/510 feet
45ISV Venture Star1,646 meters/5,400 feetAvatar
46CVN-68 Aircraft Carrier Nimitz333 meters/1,092 feet
47Imperial Star Destroyer1,600 meters/5,249 feetStar Wars
48Scoutship Vega20 meters/66 feetLeif Ericson Model
49Michael Battleship132 meters/433 feetFootfall
50Orion Battleship78 meters/256 feet
51ANNIC NOVA78 meters/256 feetTraveller RPG
52Valley Forge1,600 meters/5,249 feetSilent Running
53Klingon K't'inga class
Battle Cruiser
349.54 meters/1,147 feetStar Trek

Note: according to the blueprints the Michael Battleship (49) is 408 feet tall. However, this would make the Shuttle Orbiters mounted on the battleship too small. I scaled the blueprint so the Orbiters were at their official length, which made the Michael 433 feet tall.

Credits for the computer meshes used in the images below:

  • 10 Story Building: KG
  • ANNIC NOVA: Winchell Chung (me)
  • Al Rafik: Charles Oines
  • Boeing 747: Jay
  • CVN-68 Aircraft Carrier Nimitz: Toby
  • DDG-90 Destroyer Chafee
  • Eagle Transporter: James Murphy
  • Galactic Cruiser Leif Ericson: Winchell Chung (me)
  • Giraffe: BMS
  • Human: ?
  • ISV Venture Star: krabz
  • Imperial Star Destroyer: Blenderwars
  • International Space Station: ?
  • Klingon K't'inga Battle Cruiser: ?
  • Michael Battleship: Winchell Chung (me)
  • Millennium Falcon: Blenderwars
  • NCC 1701 Starship Enterprise: William P. "Tallguy" Thomas
  • Ogre Mark V: Winchell Chung (me)
  • Orion Battleship: Winchell Chung (me)
  • Polaris: Winchell Chung (me)
  • Saturn V: Tesler
  • School Bus: tamias6
  • Scoutship Vega: Winchell Chung (me)
  • Serenity: JayThurman (Cyberia23)
  • Space Shuttle Orbiter: NASA
  • Space Shuttle Stack: ?
  • Statue of Liberty: Damo
  • Tachi/Rocinante: Chris Kuhn
  • Type S Scout: Winchell Chung (me)
  • Valley Forge: ?
  • X-Wing Fighter: Blenderwars
Maiden Flight, SDSD Freudian Nightmare
Imperial Weapons Development Center, Coruscant
To Whom it May Concern:

Gentlemen, let me start by saying that I am greatly honored to be chosen for command of such a magnificent vessel. That said, our insystem shakedown cruise has turned up a few minor issues that I would like to see remedied as soon as possible.

1) We understand your desire to continue the classical stylized lines of the first star destroyer class vessels, and we appreciate your asthetic sense in that regard. However, strictly speaking, was it absolutely necessary to scale up the bridge tower directly? I must confess the foreward bridge window is a great distraction. Militarily, we feel that as is, the three kilometer tall window pane may provide too tempting a target for enemy forces we may engage. We've lost four helmsmen so far to vertigo as well, and we don't think this is in the best interests of the vessel's well-being.

2) The sheer size of our vessel, while a glorious symbol of the mighty Emperor, which we all appreciate completely, has become apparent to us all. My initial briefing tour of the vessel took six days to complete, and the travel tubes were based on the design in use aboard the slightly smaller Executor-class vessels. Travel time being prohibitive, we were forced to camp out in the corridors of the major sectors when we stopped for the night. Furthermore, since our crew quarters sections are located entirely within the aft dorsal sectors, both our Engineering crew and ground forces complements have built tent cities within their own sections, and are living there. Fire hazard has become nearly intolerable and the hydroponics department has sent me six hundred messages insisting that the smoke from the camp-fires is ruining their crop, and that we have enough food left aboard for only another three weeks.

2) Our vessel's own gravity is not being handled as well as could be done, with some minor problematical consequences. Our plumbers called my attention to the fact that the sewage from our 6 million-man crew backwashed through the air vents in Sections 42 to 78, decks 258 through 532. Malaria and dysentary broke out in those sections, and we were forced to cordon it off to prevent an epidemic. Our first Chief Medical Officer unfortunately was killed when he requested the paperwork on those affected, and upon receiving e-mailed reports from all 739 of his senior doctors, the computer screen in his quarters self-destructed, propelling shrapnel throughout his quarters. All droids who enter the area have failed to return, and a remote camera probe sent in, recorded images of the survivors in the affected area where they were flinging their own feces at each other, warring with sharpened pieces of metal, and attempting to eat the dismembered limbs of the aforementioned droids.

3) On a similar note, regarding the unfortunate loss of our last CMO, we have finally decided that the staff requirements of this vessel are creating further problems. For instance, our Chief Engineer has begun the habit of signing his reports, "Chief Marshal, Sovereign Nation of Ree'Ak'tor." He has since sealed off those decks, and started a war. The war in question is against his apparent rival, the commander of our ground forces near the main flightdeck, who has taken to calling himself "Bringer of the Apocalypse." Surveillance records indicate that they have since stopped wearing their armor, and have begun smearing their bodies with industrial cleaning fluid and lubricants before launching raids upon the Engineering department. We believe that they have begun ritualistically sacrificing one of our TIE-fighter pilots before each attack to bring them luck.

Aside from a minor note that some of our turbolaser turret gunners may have starved to death when their food shipments were cut off by the warzone, there is little else to remark on, save that in our first tactical drill, during the course of a two-hour right turn, we failed to halt our rotation with the result of the subsequent and very unfortunate destruction of the entire Coruscant 4th Defensive Fleet. I've made a note to send out letters of regret the moment we reacquire contact with our communications room at the bow of the vessel. That of course is the reason why this message had to be sent to your offices via pen, paper, and one of our probe droids. I beg forgivness for the clerical difficulties that may cause.

Grand Admiral
SDSD Freudian Nightmare
unknown author (2013)

“Finally, let us turn to the biggest megaships of them all, the fleet carriers. Including them in this work is a choice which I expect to be somewhat controversial – many would argue that a fleet carrier is a formation, not a vessel – but with respect to those readers who may hold that position, since the Imperial Navy treats fleet carriers as a single vessel for asset accounting and command designation purposes, so in turn shall I.

“Let us begin with a look at the history of the type. Fleet carriers were not known before the Exterminomachy (5782-5901). While before that time lighthuggers had met with occasional hostility, they had proven more than capable of defending themselves against local system defense forces, in particular with the Perreinar Wheel1 – and in those cases where they were not, it was because they had encountered a Power not readily opposed by pure military force. This changed with the arrival of the skrandar berserker probes, whose numbers and willingness to embrace suicide tactics made them a serious threat to even well-defended vessels, and eliminating breeding site for which required the transport of full task forces to their host systems.

“The first fleet carriers, then, were improvisations; lighthuggers pressed into service under the right of angary. Stripped down by removing all cargo capacity, much crew space, and all other less-than-essential facilities, and enhancing their fuel capacity with multiple drop tanks, it became possible to clamp a small number of light units – overstocked with fuel and supplies – to the spine of such a vessel, and have it haul them slowly and painfully to a target system.

“Such crude improvisations were fraught with problems, from wear and tear on ships and crew during the slow transit, to the risk of interception before the transported units could free themselves from the carrier – both due to the inefficiency of the mechanical clamps, and the need to cut clamps frozen in transit or actual hard welds used where clamps would not suffice, to even entire vessels lost from the carrier in transit. (The last of these to be recovered, CS Bloodwashed3, was salvaged with all hands in 6722.)

“Fortunately, by the third year of the Exterminomachy, new designs were emerging from the cageworks at Ashen Planitia and Armory. The second-generation fleet carriers were custom-built starships, or rather, the specialized elements (the “propulsion head” and “collier module”) were, since the second generation eschewed the rigid designs of the first in exchange for dispersed tensegrity structures.

“In effect, the starships transported by the fleet carrier, along with the specialized elements, formed the floating compression struts of the overall structure, while being linked by braided cables (derived from orbital elevator technology) into a unified structure. The majority of the propulsive thrust is provided by the dedicated propulsion heads, while specialized fleet mediator software enables the use of the drives of the various carried ships to balance the structure and correct attitude. Meanwhile, supplies carried in the collier modules, distributed by rigged flexpipe and by cable-crawling logistics robots, eliminated the need to overload any individual ship with supplies, and indeed enabled the transportation of greater volumes of fuel and replenishment. Moreover, such fleet carriers could separate instantly if intercepted by simply blowing the explosive cable-couplers and engaging their drives independently, the dispersed tensegrity structure providing adequate safety separation for this.

“Such dispersed-design fleet carriers served with distinction throughout the remainder of the Exterminomachy, and have remained a key element of IN subluminal doctrine since. While there exist a third generation of fleet carrier designs, these merely reflect the evolution in technological reliability that allows the physical cables of the second generation to be replaced with vector-control tractor-pressor beams, and does not reflect any change in fundamental design or doctrine.

“As ad hoc structures, of course, it would be incorrect to say that fleet carriers have classes, in the strictest sense. However, the individual propulsion heads and collier modules, the former full starships in themselves, do. Thus, we shall begin our examination of fleet carriers with a look at the most common propulsion head in Imperial service, the Legends-class…”

– Megaships of the Imperium, Lorvis Maric, pub. 7290

  1. Perreinar2 Wheel: a fight-and-flight maneuver in which a lighthugger puts its stern towards the battle and engages its interstellar drive, thus retreating from the engagement while simultaneously treating the enemy to the close-range efflux of a pion drive – a situation which is very rarely survivable for anything larger than a baryon.
  2. From the eponymous horse archers who had perfected the “Perreinar shot” centuries before.
  3. Lost in the wreck of CS Cúlíän Daphnotarthius, which suffered a structural collapse of the spine while outward bound to IGS 31238 in the second year of the war.
From OUTSIZE by Alistair Young (2019)

Calculating Volume and Mass

The Easy Way 1

If you just want something really quick and dirty:

Estimate somehow the volume (m3) of your spacecraft. Calculate the mass by multiplying the volume by the average density (kg/m3) of a spacecraft.

Estimating Volume

  1. There are equations to calculate the volume of simple geometric objects such as cubes, spheres, cylinders, and cones. Approximate the spacecraft as an assemblage of such objects, calculate the volumes, then add them all up. Example: here.
  2. Create a scale model inside a 3D modeling package, and use the included tools to calculate the internal volume. Example: On my mesh model of the Galactic Cruiser Leif Ericson, the AreaVol script informs me the ship has an internal volumeof 68,784.87 cubic meters.
  3. See if somebody else has already calculated the volume. Example: According to ST-v-SW.Net the internal volume of the TOS Starship Enterprise is 211,248 cubic meters.
  4. Use the known volume of a comparable existing object. Example: a Russian Oscar submarine has a volume of 15,400 cubic meters. It is a good size for a spaceship.
  5. If the spacecraft is approximately a sphere or approximately a cylinder, just use the ship's average radius and height to calculate an approximate volume using the sphere or cylinder volume formulae. Close enough for government work.
  6. Make it up out of your imagination.

Of course there is some differences of opinion on the exact value of the average density of a spacecraft.

One easy figure I've seen in various SF role playing games is a density of 0.1 to 0.2 metric tons per cubic meter (100 to 200 kilograms). That corresponds to average pressure compartments being cubes 10 meters on a side, with pressure bulkheads averaging 17 to 33 kg/m2.

Ken Burnside did some research when he designed his game Attack Vector: Tactical. He found that jet airliners have an average density of about 0.28 metric tons per cubic meter, fighter aircraft 0.35 tons/m3, wet navy warships from 0.5 to 0.6 tons/m3, WWII battleships 0.7 tons/m3 (it don't take much excess mass to send them straight to Davy Jones locker), and submarines 0.9 tons/m3. For the combat spacecraft in AV:T, Ken chose a density of 0.25 tons/m3.

Ship Densities
Attack Vector: Tactical0.25 ton/m3
Jet Airliners0.28 ton/m3
Fighter Aircraft0.35 ton/m3
Wet Navy Warships0.5 to 0.6 ton/m3
WWII Battleships0.7 ton/m3
Submarines0.9 ton/m3

A student of the game Orbiter (who goes by the handle T. Neo) used the 3D models in the game to figure the volume of various space constructions. Dividing by their known masses yielded the densities.

Spacecraft Densities
Space Shuttle External Tank0.011 ton/m3*
Long Duration Exposure Facility0.049 ton/m3
S-IC0.050 ton/m3*
Leonardo Multi-Purpose Logistics Modules0.058 ton/m3
Hubble Space Telescope0.061 ton/m3
International Space Station0.074 ton/m3
Space Shuttle Orbiter0.088 ton/m3
Space Station Mir0.175 ton/m3
Space Shuttle Solid Rocket Booster0.206 ton/m3*

* Large portion of volume is dedicated to propellant

Fans of the Traveller role playing game have to do a bit of work. Starships in Traveller are rated in terms of "displacement tons" or "dtons". This is a measure of volume, not mass. 1 dton is 14 cubic meters, which is approximately the volume taken up by one metric ton of liquid hydrogen (actually closer to 14.12 m3). Liquid hydrogen is starship fusion fuel.

So if you assume a Traveller starship has an average density of 0.2 tonnes/m3, then given dtons the starship mass in metric tons is:

starshipMass = dtons * 14 * 0.2


starshipMass = mass of starship (metric tons)
dtons = displacement of starship (displacement tons or dtons)
0.2 = average density of starships (tonnes/m3)

Example: a Broadsword class mercenary cruiser has a volume of 800 dtons (or 1200 depending on where you read it). This means its mass is 800 * 14 * 0.2 = 2,230 metric tons.

Traveller deck plans are confusing as well. If they are ruled off in a square grid, chances are the squares are 1.5 meters on a side. The space between the floor and the ceiling of a deck is assumed to be 3 meters. Bottom line is that on a Traveller deck plan 1 dton is represented by two grid squares.


(ed note: This is from a tabletop starship wargame called Voidstriker. In the game one can custom design one's combat starships using a ship construction system. The different classifications of starship internals is somewhat interesting, but I found UDST to be hilarious.)

Ships are made of multiple sections called hulls. These hulls represent an unspecified amount of volume, and come in five types: Undifferentiated Starship Tissue (UDST), Containment, Magazines, Systems, and Hangars.

UDST hulls hold the ship's drives, power plants, hardpoints, crew quarters and access areas, command decks, and everything else that a ship requires to function at a minimal level. Containment hulls hold reaction mass, cargo and troops. Magazines hold internally-stored bombs, missiles and torpedoes. Hangars hold small craft (fighters, shuttles and the like). Systems hulls hold short and long range scanners.

Up to 80% (round down) of the ships hulls may be containment hulls, magazines, systems or hangars. The rest must be UDST hulls.

From VOIDSTRIKER by Charles Oines (2007)

While working on an old unfinished page I'd forgotten about, I realized that I really needed a decent estimate of Star Destroyer mass.   Despite not having much to really go on, I decided to make a guesstimate.  

Unless and until we get more information, it's as good as anything else:

So, let us assume that a Star Destroyer is 1600 meters in length.   Now we need an estimate of their density.   We have options here.

1.  We can attempt to use the density of Star Trek vessels.   Star Trek vessels like the Intrepid Class, for instance, have a density of over 1100 kg/m³.  However, we know that the vessels are constructed of different materials and so on, so this is a somewhat dangerous assumption.  There's also the fact that the Constitution Class ships had a far higher density of over 4300 kg/m³.   However, given that the Intrepid can land as most Star Destroyer classes seem able to, the Intrepid density seems the safer (albeit still dangerous) assumption.

2.  We can attempt to use the density of real-world spacecraft.   This is also dangerous, of course, since real-world spacecraft are hardly military vessels.  They are designed to allow people to get to space for a brief period of time, but can hardly be expected to withstand even a single hostile bullet or other decent-velocity impact.

Now, it happens that when Star Trek guru Rick Sternbach was designing the Intrepid Class for Star Trek: Voyager, he intentionally based their stated mass off of an estimate of the ship's volume, calculating the mass via a density derived from an estimate of the Apollo capsule command module.  And indeed, the Intrepid density is within about 10-20% of that value, assuming the Intrepid model used on this site for the estimate is basically the same as his.   However, the command module was basically just the crew compartment and heat shield for re-entry, a single part of the combined Command/Service Module (CSM), with the service module featuring the large engine bell and other machinery that enabled Earth-Moon transit.

Taking that combined vehicle which masses 30 tonnes and ballparking her volume based on her 4m diameter and 8m length (she's actually 11 meters, but between the rear engine bell and conical front section a 'shave' is not out of order for determining ballpark density), the CSM volume is 100m³ and her density is thus 298kg/m³.

That seems a bit light, so we can also compare to the space shuttle orbiter.  Empty, a newer shuttle like Endeavour weighs about 70 tonnes, and she's about 105 tonnes when full.   At about 37.25m long, 23.75m wide, and 17.25 meters tall, she's a big girl.   Determining her density is a little bit of a trick, though, since much of her total empty mass . . . not to mention her width and height . . . is nothing more than wing surfaces.   But since we're ballparking, we can simply take the fuselage as a cylinder and tack on a couple of extra meters for the eyeballed volume of the various atmospheric control surfaces.

So, per estimation from this site, we have the total length of 37.25 meters.   A smidgen of that is the vertical stablizer (the tail fin), but we'll just roll with that figure.  Given that the shuttle fuselage is roughly cylindrical, the height and width values of about 6 meters are sufficient for diameter (the crew area and payload bay are below six meters, the rear fuselage with the engines is over six).   So if we ballpark a 40x6 cylinder, we come up with a total volume of 1130m³.  Given her empty and full masses, the density ranges between 62 and 93kg/m³.

Well, now.   It seems that Rick Sternbach's choice was rather on the heavy side, after all.  The space shuttle tops out at around 100kg/m³, the Apollo CSM 300kg/m³, and the Apollo command module with heat shield by itself is near 1000kg/m³.  And yet the Constitution Class still came in four times more dense than that, and about 40 times denser than the space shuttle!

So where should we attempt to put the Star Destroyers?   Considering that large warships of the Clone Wars era seem to be largely hollow (e.g. the Venators with their extensive landing bay areas, the Malevolence with its massive open center railway areas, and so on), I hardly feel comfortable comparing it to an Intrepid Class ship that has very little empty space by comparison.

On the other hand, given the extensive use of simple steel even for external towers on the Death Star (per the ANH novelization), Coruscant buildings, and similar, it seems unlikely that durasteel or steelcrete will be superdense.   After all, given that a natural stone on Yavin was so dense that no weapon was thought capable of penetrating it, we could be forgiven in believing that Star Wars ships are built strong but as light as possible.

That said, I figure Star Destroyer density probably falls somewhere in the 500-1000kg/m³ range.

Given a calculated volume of about 54,000,000m³ for Star Destroyers at 1600m length, and a density range of 500-1000kg/m³, the mass of a Star Destroyer should fall somewhere between 27,000,000,000 and 54,000,000,000 kilograms.   That's 27 to 54 million metric tonnes.  

If one wants a specific estimate, I'd guess a density of 750kg/m³ and an ISD mass of 40,000,000 tonnes.

Using this density figure elsewhere would give us the following masses:

VesselMass in KilogramsMass in Tonnes (est.)
DS1 (@120km):678,525,000,000,000,000680 trillion
DS2 (@160km):1,608,000,000,000,000,0001.6 quadrillion
Super SD:9,484,425,000,0009.5 billion
Home One:253,978,500,000250 million
Trade Fed:1,520,812,500,0001.5 billion
Tantive IV:48,564,00050,000
Imp. Shuttle:357,750360
Millennium Falcon:2,937,7503000

Actual figures could vary significantly, of course, and my rounding above was somewhat haphazard.   I would say that this is especially the case with smaller vessels, but interestingly the X-Wing mass is almost identical to the empty mass of an F-14 Tomcat.  Once missiles and fuel are added, though, an F-14 can mass 33 tonnes.

Also, I don't have volume figures for the Venator or Acclamator.  I'd guesstimate the former at 15 million tonnes and the latter around 8-10, but I really have no clue as to the proper value.  This is just a complete pulled-from-the-posterior guess from memory.

The Easy Way 2

The second quick and dirty method:

Estimate the mass (kg) of each major component. Divide the mass of each major component by its density (kg/m3) to find the volume of each major component. Total the masses to get the spacecraft mass, total the volume to get the spacecraft volume.

Estimating Mass

Often you have the total mass, and the propellant mass. The dry mass is the total mass less the propellant.

If you have the mass ratio, you can figure your dry mass by totaling up the various components, then use the mass ratio to calculate the propellant mass and total mass.

remember that average NASA spacecraft dry mass (i.e., sans propellant) divides up to include:

Percentage of Dry Mass
Power Systems28.0%
Thermal (heat radiators)3.4%
Guidance, Navigation, and Control8.0%
Everything Else26.7%

Keep in mind that this is for NASA style spacecraft. The percentages for, say, the Starship Enterprise will be totally different and anybody's guess.

Now all you need are some figures on the average density of these various items and you can calculate quick and dirty ship volumes. I'm looking into it but it's hard.

The Hard Way

The following is a method to calculate the spacecraft's structural mass. It is derived from a document at Christopher Thrash's web site. He bases his analysis on data from the book all the pros in astronautics use, Space Mission Analysis and Design. There is some additional information here.

Lucky you, Eric Rozier has implemented the algorithm below as an on-line calculator.

Assumptions: as a first approximation, the spacecraft is modeled as a free standing column resting upon the engines. The column is "thin-walled", that is, the column radius divided by the hull thickness is less than 0.1. The column is only supported by its walls (monocoque construction). The column has its mass uniformly distributed along its length. The ratio of column's length to its diameter is 3.2 : 1.0. The hull is assumed to be capable of withstanding forces equal to its mass times gs of acceleration on any axis: axial, lateral, or bending.

This means that the following formula only work for a cigar-shaped rocket, not a spherical one.

Decide upon the volume, or total displacement of the hull in cubic meters (m3). This will boil down to volume for reaction mass plus volume for the crew and cargo. Calculate the volume for your reaction mass by

Vpt = Mpt / Dpt


  • Mpt = mass of propellant (kg)
  • Dpt = density of propellant (kg/m3) = 71 for liquid hydrogen, 423 for methane, 682 for ammonia, and 1000 for water
  • Vpt = volume of propellant (m3)

If you don't know the mass of the propellant, it can be calculated from the dry mass and the mass ratio:

Mpt = (R * Me) - Me


  • R = mass ratio (dimensionless number)
  • Mpt = mass of propellant (kg)
  • Me = mass of rocket with empty propellant tanks (kg)

Add the volume of the reaction mass to the desired living space volume to get the spacecraft's volume. Later you can figure the approximate spacecraft dimensions by using the formula for the volume of a cylinder ( v = π r 2h ), keeping in mind that it should be about 3.2 times as high as it is wide (although you can get away with larger values).

Now comes the fun part. This is going to be what they call an "iterative process". This means you do the calculations, take the results and do the calculations again on the results.

Step 1: Find Mass

M = M~st + Mst


  • M = mass of spacecraft (kg)
  • M~st = sum of mass of all spacecraft components except structure (kg)
  • Mst = spacecraft's structural mass (kg)

Since this is an iterative process to calculate Mst, the first time through Mst will be equal to zero.

Step 2: Find Density

D = (M/1000) / V


  • D = density of spacecraft (ton/m3)
  • M = mass of spacecraft (kg)
  • V = volume of spacecraft (m3)

Note that here density is in tons, not kilograms per cubic meter

Step 3: Find Structural Support Volume

Vsr = (V4/3 * Apg0 * D) / (1000 * Thm)


  • Vsr = volume of structural mass needed to support spacecraft (m3)
  • V = volume of spacecraft (m3)
  • Apg0 = maximum acceleration of spacecraft (Terra gs)
  • D = density of spacecraft (ton/m3)
  • Thm = "toughness" of hull material. Hard steel = 2.86.
Step 4: Find Anti-Buckling Structural Volume

Vsb = (V1.15 * (Apg0 * D)0.453) / 300


  • Vsb = volume of structural mass needed avoid buckling (m3)
Step 5: Find Actual Volume

The actual volume Vs is equal to the larger of Vsr and Vsb.

(Note: Mr. Thrash informs me that an aeronautical engineer of his acquaintance is of the opinion that while the equation in step 4 works fine for a small rocket with a ten ton payload, the equation does not scale well if used for a larger rocket. The engineer is sure that Vsr will almost always be enough to resist buckling as well. In other words, just use Vsb = Vsr).

Step 6: Find Structural Mass

Mst = Vs * Dhm


  • Mst = spacecraft's structural mass (kg)
  • Vs = volume of structural mass (m3)
  • Dhm = density of hull material (kg/m3) (7,850 for steel, 4,507 for titanium, 1,738 for magnesium)
Step 7: Start Over from Step 1

Use the new value for Mst and start over. Repeat until the value for Mst stops changing (or you get tired).

When you have your final value for Mst, and M, use M to check and see if the spacecraft's mass ratio is still acceptable. If not, reduce the value for M~st and do some more iterations.

Now you know why rocket scientists use computers to do all the grunt work.

Remember that the mass of the propellant tanks will be approximately equal to full propellant mass times 0.15. The tank mass will be included in the structural mass, if the ship designer is not totally incompetent.

The shortcut is to stop at step seven, reduce M~st by Mst, and everything will add up.

Calculating Volume Of Existing Model

Figuring the hull volume of an existing design is a bit more tricky.

By way of example, a Russian Oscar-II submarine is an oval cylinder about 18 meters wide by 9 meters tall by 154 meters long. It has an internal volume of about 15,400 cubic meters. It has a density of about 0.9 metric tons per cubic meter, so it has a mass of about 15,400 x 0.9 = 13,900 metric tons.

There are equations for calculating the internal volume of various geometric shapes. What you have to do is approximate your spacecraft design using only these shapes. A sphere is easy. A classic cigar shape is sort of a cylinder with a cone on each end. You'll find a crude example of that here.

If your spacecraft is a complicated shape like the Starship Enterprise, you have a real problem.

If you have a physical model of your spacecraft, you can try estimating its displacement by caulking it water-tight, immersing it in a container of water, and measuring the water it displaces. Alternatively, fill a box with sand, dump the sand into measuring cups to measure the volume of sand, put the model in the box and fill it with sand, dump the sand out into measuring cups, and finally subtract the two volumes to discover the volume of the model.

Designing with CGI Modeling

Finally, you can hire a computer artist to use your blueprints to create a computer model in Lightwave then use the AreaVolume plug-in to determine the volume of the model.

Alternatively, you can proceed like graphic artist Myn.pheos, creating your mesh in the amazing free program Blender and using the 3D Printing Toolbox to calculate the volumes. Myn.pheos also has some techniques to find the center of gravity of various components, and to discover optimal placement of heat radiators.

The following tips are specific to the Blender software, but an artist skilled with another 3D computer modeling program could adapt the tips to their software. Myn.pheos is a native of Slovakia, and English is his second language. Myn.pheos:

Area and Volume

Guessing the volume of spacecraft isn't accurate in most cases. Boxy shapes aren't the most pleasing, and computing volume or area of curved surface by hand is tedious and hard. So the best approach is to let the computer [do the] work for you. In Blender, there is no build-in way to compute volume of objects. But there exist scripts than can do this. One of the is Quantities Bill by Yorik. It computes length, area or volume depending on the topology of mesh. If you have the shape of the spacecraft in your mind, let it pass the test. Roughly model the hull, propellant tank or crew compartment (it must be one object, with no holes in it) so you can get the volume. If you want to know the area of hull, simply remove the smallest face from the mesh and run the script. The figures aren't exact (this depends on how precisely you modelled the hull), but they are obtained fast, and it's easy to [re-calculate the figures if you alter the shape of the hull].

Where is the Center of Gravity?

This is easy to guess in case of homogeneous objects. But spaceships aren't that case. When you know the mass of spacecraft, rough location of components and their estimated weight, you can try to search for the center of gravity (COG). In Blender, it is possible to find the COG easily, just place vertexes in COG of each component. Decide the weight of each vertex, and then add as many as you'll need. Logically, the sum of them should be equal to total mass of ship. To get the COG, simply select all vertexes and make sure the pivot is set to Median point.

(ed note: in Blender, if the pivot control is set to "Median", when you select a group of vertexes the pivot control will automatically appear at the mathematical median point. Myn.pheos is saying that at the center of gravity of each component, place a number of vertexes proportional to that component's relative mass. Select all the COG vertexes of all the components, and the pivot control will indicate the COG of the spaceship as a whole. Keep in mind that the ship's axis of thrust must pass through the COG)

Where to place radiators?

That depends on the shape of the ship. If you have several spots where they look good, you can test the placement. This involves rendering the image and then using histogram to interpret the rendered result. First create two materials. For hull, create fully transparent material (Alpha = 0.0), with no specularity (Spec=0.0), don't forget to check the Ztransp button on. For radiator, use total white material (Col = R 1.00, G 1.00, B 1.00), with again without specularity (Spec=0). Make sure both receive all ambient colour (Amb = 1.0). Now to the environment settings. As background, use total black color (HoR = 0.0, HoG = 0.0, HoB = 0.0, ZoR = 0.0, ZoG = 0.0, ZoB = 0.0), and ambient perfect white (AoR = 1.0, AoG = 1.0, AoB = 1.0). Turn on Ambient Occlusion, make the Sub button pushed (so it darkens occluded spots), ensure that Energy is 1.0 and Plain button pushed.

Now only to set the camera (the best to be perpendicular to the radiator) and render.

Open the rendered image in an image editor. I use GIMP, but only the histogram is important. Now set the lower value in histogram to the lowest non-zero number (remember the pitch black background?), and read the statistical data. The most important is Mean value, this is the average value of all pixels on radiator. Divide this number by 255 to get the percentage of unoccluded area. There rest is probably heating up the ship, so change try with another radiator position.

This method has some weak points, but it is good enough for some decisions. The fully occluded pixels aren't taken into account, the precision increases with samples, the edges aren't treated well (they are not full white, if antialiasing is on).


I must say that I am very impressed with Myn.pheos' technique. I am reasonably skilled with Blender, but it never occurred to me that it could be used to find centers of gravity and optimal heat radiator placement. Myn.pheos is a genius.

Radiation Backscatter

A gentleman who goes by the handle Dogmatic Pyrrhonist (and TiktaalikDreaming) is a noted crafter of spacecraft mods for the simulation game Kerbal Space Program.

He decided to make a Gaseous-core Open-cycle nuclear thermal rocket mod for KSP. He is using Blender 3D as his modeling program.

He wanted to add some heat radiators (because GCR need lots of them), when he became aware of the dangers of neutron embrittlement, neutron activation, and radiation scattering. It seems that William Black was working on a similar project.

Dogmatic Pyrrhonist Backscatter 1

Dogmatic Pyrrhonist
     After shadow shields were brought up in William Black's feed regarding his work on a Gas Core Rocket, I had a good read about various things (mostly from Winchell Chung's Atomic Rocket pages, see
     Turns out my prior plan of wide-short expanding radiator panels would result in radiation scattering, eventual enbrittlement of the radiators, and basically cooking the crew with neutrons, and gamma rays. The radiator free, high thrust, low ISP edition had no such issue, and has a simple shadow shield in line now. But the high ISP needed a radiator rethink.
     I have a plan for the radiators, much like one of the pre-movie sketches of the Martian's Hermes on Atomic Rockets ( Basically a triangle type arrangement made from staggered rectangular panels that all fold away.
     That means a much longer frame to hold all that radiator. All of it, forward of the shadow shield.
     Anyway, WIP, this is the rocket, edition one of the shadow shield, and the frame structure. I'll be adding a final frame at the end to spread load onto a wider area. I'll be wanting that as a separate piece, as the KSP heat transfer systems don't include cooling fluid pumping, so the frame, rocket and radiators will all have extremely heat conductive values to mimic the working fluid. Which means I'll need one extra piece to be an insulator, to protect the rest of the craft from those 1390C radiators.

William Black
     This is looking great! I recall we had that conversation early on, when I described why the rectangular radiators arrayed around the nozzle would reflect radiation forward onto crew and vehicle, and so would definitely need to be forward of a radiation shadow shield, or did I have that discussion with Winchell Chung?
     The propulsion bus for my version is definitely an in-space assembly. I gathered (from yours or Winchell Chung's comments) that for KSP purposes it would need to be segmented and fold-away. 
     Oh, BTW, data sheet for 5% Borated Polyethylene here

Dogmatic Pyrrhonist
     William Black Yep, I remember all the reasons why you'd gone for the triangular shape. At first I was going to just dismiss the idea under the category of "Kerbals don't care". But then, I thought, I'd still like the thing to be real-world-sane, esp as I'm looking at doing some Realism-Overhaul conversions for some of the mods. So, while there's no mechanism in game to handle it, I have come around to thinking it should be arranged to at least mostly shield payload/crew.
     I roughed in a truncated triangle to get the surface area right for the radiators, and adjusted the shadow shield to match. I might need more than 51.5m of frame. :-/
     That's quite the shadow shield.
William Black
     Dogmatic Pyrrhonist, yeah, that's pretty much how I did it. I needed a 6.7 meter diameter shadow shield and wound up adding an additional 9.1 meters to my truss, two 3.0 meter sections between the shadow shield and the aft edge of the radiator and one 3.0 meter section between the forward edge and propellant tank. With the 29.8 by 10.01 meter propellant tanks for the 80 day Mars mission spacecraft that puts my crew module 12.4 meters past the 100 meter minimum separation between crew and nozzle.

(Then noted virtual production engineer Ron Fischer made a quiet but brilliant suggestion:)

Ron Fischer
     You can use lighting and shadows in your CG rendering program to analyze the shadowing of the shield. In fact, this is where the original math for lighting simulation came from: radiation studies on tanks in the 60s. Might as well go "Back to the Future" on that one! 

(You could almost see the light bulbs lighting up over each person's head.)

Dogmatic Pyrrhonist
     Ron Fischer I had not thought of that.

Winchell Chung
     Yes, what Ron Fischer said.
     I just remembered about somebody was using Blender to calculate spillover from heat radiators in their design
     Actually, some scientists did something similar to resolve the Pioneer Anomaly.

Dogmatic Pyrrhonist
     Dammit Winchell Chung , I've got enough tabs open in my browser already. :-)
     Initial ray casting adjustments, although I haven't checked yet if that's enough radiator. Nor whether it's still in shadow when rotated 45 or 90 degrees.

Winchell Chung
     Dogmatic Pyrrhonist You might have to simplify the model. First approximation with a light at the reaction chamber, the shadow shield, and the radiator.
     If you want to get into actually modeling the scatter, be my guest.

Dogmatic Pyrrhonist
     Winchell Chung Scatter is easy. Just place light sources at the outside edges of things that might scatter. I should disable rendering of things that would be basically transparent to neutrons or gammas, etc.
     oooo.... transparency. :-)

Dogmatic Pyrrhonist
     Oh dear, emissive, transparent, reflective shaders.

Winchell Chung
     Dogmatic Pyrrhonist Yes! That's the ticket! Radiation design by CGI mesh modeling. Hot stuff!

Ron Fischer
     Very cool Dogmatic Pyrrhonist Also, Winchell Chung I recommend requesting use of those for Atomic Rockets! Should illustrate the point nicely!
     Hey! I should suggest this to the good people making Kerbal. Could be a cool part of the design experience for nuclear spacecraft. 
     It is interesting to note that the cylinders which (I guess) are used to gimbal the engine get quite a strong dose. 

William Black
     Dogmatic Pyrrhonist and Winchell Chung I've found that you can optimize the shadow shield using this technique. I've found that a smaller shadow shield diameter is possible by adding truss segments between the shadow shield and the aft end of the radiator panels. Because the truss is lighter than the shadow shield, you realize a mass savings. 

From a thread on Google Plus (2015)
Dogmatic Pyrrhonist Backscatter 2

      I've been checking my rework of my gas core NTR for Kerbal Space Program regarding the shadow shield. Using 3d ray casting as it was originally intended.

     Each radiation emitter gets its own colour, so I can see what might be the cause of anything getting past the shield. Which is important, as there's a world of difference between active fission cores and a bit of stored uranium. Most of the non emitting structure uses a rough translucent blender material so it can scatter, emulating, well, scatter, and re-emission. The shadow shield itself I did as a reflective opaque, although that isn't quite true. It's reflective to high energy electromagnetic (gamma), but absorbent to neutrons. Above the shadow shield though, are the uranium tanks. And although they themselves are emitting neutrons and other things, you really really don't want them getting hit with bonus neutrons. There's also the tungsten dust tanks, and as that exists to absorb, I used an opaque material for them, although the radiation they're collecting, it didn't make a big difference.

     Looking up past the plume (volume emitter material) there's a faint blue tinge for the plume's emission on the structural ring around the top. I'm mostly ok with that because from last time I did this it became apparent there's absolutely no way to prevent all the radiation from the plume. You can minimise, but not remove. And why am I checking the radiation from the plume? This is a model of an open cycle gas core reactor nuclear thermal rocket, so the exhaust has fission fuel and products in it. As little as you can engineer, but likely something like 1%

     Anyway, now almost a Kerbal Space Program mod. Still needs a better plume and several square km of radiator (slight exaggeration)

From a thread on Twitter (2019)

Meanwhile William Black was already hard at work on a GCR. He is also using Blender 3D.

When William Black read Ron Fischer's brilliant suggestion, he quote "found this to be a compelling proposition, an opportunity to test out the validity of my design" unquote.

William Black Backscatter 1

      I found this to be a compelling proposition, an opportunity to test out the validity of my design.
     Dogmatic Pyrrhonist and I both set about individually setting up a radiation simulation by CG lighting; his results are to be found at links in this thread November 6, 2015
     Initially, for purposes of approximation, I used a cone, which you strip out of the scene once it has served its purpose, this is used to insure the radiators panels (and everything else forward of the shadow shield) are completely within the shadow region. It is a matter of placing the cone so to intersect the aft-most edge of the radiation shadow shield, if all components forward of the shadow shield are properly placed nothing should protrude through the surface of the cone.
     I realized the technique can be used not only to optimize the shadow shield in terms of placement, but also in terms of diameter. Previously, using the cone I had realized that increasing the distance between the aft edge of the radiator panels and shadow shield allows a smaller diameter shadow shield. Using this technique allowed me to test that theory, and it in fact worked exactly as anticipated. Truss segments mass less than the 5% Borated Polyethylene of the shadow shield, so there is a savings on structural mass, which is important because, as we all know, every gram counts.
     I rendered the scene against a gray background, then a second time against a completely black background.
     I made an attempt (which may be laughable) to model the plume. I used a bright blue emission shader. I was curious in regards to how much blue emission, representing radiation from the plume, would show up on the structure of the vehicle. Lacking data on the physical characteristics of plume expansion immediately after leaving the nozzle, this may be an insufficient test, so I’m not sure this adds anything, but darn, it looks nifty.
     Ron Fischer suggested I attempt this again with volumetric lighting, and I intend to do so at a future date.

From William Black (2015)

Physicist Luke Campbell had some additional suggestions:

     You might want to check for radiation scatter from the rocket bell to the radiators. You could make the entire structure aft of the shadow shield glow, make the shadow shield 100% black, make the spacecraft fore of the shadow shield white, and then look at the craft from the back to see if the edges of the radiators are illuminated. If they are, neutrons and gamma rays emitted from the reactor can scatter off the rocket bell (say), bypass the shadow shield, scatter off the radiator, and make their way to the payload/crew/control electronics/whatever. Just eyeballing it, it looks like that could happen.
     Also, from the linked post describing the design — you probably will want a few centimeters of lead fore of the borated polyethylene, for sopping up the gamma rays. The set of materials that are good at stopping neutrons seems to be orthogonal to the set of materials that are good at stopping gamma rays. By putting the poly between the reactor and the lead, you arrange it so that gamma rays produced by neutron interactions in the poly are also blocked by the lead part of the shield.

From Luke Campbell (2015)

     Physicist Luke Campbell examined my Blender radiation simulation and suggested some modifications which might test the model more rigorously.
     Following his suggestion I applied emission shaders to everything on the “hot” side of the shadow shield, so, rather than just the gas core reactor, this now includes all structure (truss, engine gimbals and supports) and all LH2, Helium coolant lines, and turbine pumps and associated plumbing including the turbine exhaust, and of course the expansion nozzle.
     I applied a flat non-reflective black shader to the shadow shield, and applied a white shader to all structure on the “safe” side of the shadow shield (truss, radiator panels and heat exchanger housings, tensioning cable, cable rigging, LH2 and Helium coolant lines).
     Changes in place, I ran the radiation simulation again. As you can see from the top image the simulation revealed that radiation was in fact impinging on the aft outer corners of the radiator panels and the tensioning cables, a fact not visible in my previous simulation.
     This means radiation would travel along these parts of the vehicle, turning them into additional sources of radiation, damaging the radiator system and vehicle structure via radiation embrittlement, damaging control and electrical systems, and it means radiation would scatter from these points onto the rest of the vehicle posing a hazard to the crew.
     I added truss segments and increased the diameter of the radiation shadow shield, running the simulation after each configuration change, till I arrived at a good result, which you can see in the second image down.
     The lower two images are non-rendered screen captures of the same area of the model, the aft-most portion of the propulsion bus. Before structural modifications on the Left, and the final optimized configuration, on the Right.

From William Black (2015)

Pioneer Anomaly

Something like Myn.pheos technique for placing heat radiators was used to solve the mystery of the Pioneer Anomaly. The trajectory of space probes in general and the Pioneer probes in particular should follow precisely Newton's Laws of Motion. Once you've accounted for all the extra factors, of course. So scientists were quite upset when the probes started to gradually diverge from their calculated trajectory. There are all sorts of proposed explanations, ranging from observational errors to new laws of physics.

Dr. Frederico Francisco (Instituto Superior Técnico, Lisbon) and colleagues believe they have the answer. Others have tried and found wanting the hypothesis that heat radiated from the probes could be the culprit. But Dr. Francisco et al submit that this is because the radiation mathematical models are too simplistic. Using the 3D CGI rendering technique known as "Phong shading", they have shown this will account for the Pioneer Anomaly. Phong shading takes into account not just the heat radiated, but the heat that hits parts of the probe's structure and is reflected from it.

As you can see, this is very similar to the technique used by Myn.pheos.

How Much Does It Cost?

How much does a spacecraft cost? I have no idea. This depends on zillions of factors: economic system of the nation producing the spacecraft, is it a prototype/standard model/specialized/third-hand ship, etc.

As a data point, Rick Robinson has made lots of assumptions for his RocketPunk future, and came up with a ballpark figure of $1 million per ton of inert mass or $500,000 per ton of payload capacity. With a deep discount for second and third-hand spacecraft. As I said this depends on lots of assumption, read the link to find more details (and so you can fiddle with the factors yourself).


Figuring the surface area of a spacecraft is about the same level of difficulty as figuring the internal volume. The same techniques apply: approximate the spacecraft as a series of easy to calculate shapes, or use a CGI package that can calculate it for you.

Usually it isn't worth the bother unless you are trying to figure the mass of the armor required for a warship. Or you worry if there is enough space on the hull to place all the stuff you want to put.

Some other bits of dynamic tension for you.

Surface area goes up at a square function, volume at a cubic function. Everything fights for surface area on the hull of the ship — if you want more weapons, you need surface area to mount them. If you want sensors or radiators, ditto. Don't forget docking ports, fuel tank hookups, and everything else you'll want. If you're using plausible engines with thrusts rated in double digit milligees (as opposed to the over-the-top engines I use for Attack Vector: Tactical), it's more and more likely that your ship will look like a fusion torch with a christmas tree that's been well and truly loved by a cat on top of it. :)

The lesser your surface area for a given volume, the less armor you need for a given rate of protection. For a generalized case, most internal components can, as Rick likes to point out, be approximated by aircraft parts for unit density. (Surface naval ships range from average density of 0.35 to 0.65 for some of the fully loaded WWII battleships, aircraft range from 0.2 to about 0.4).

Perhaps, to minimize the hazards of radiation, they use structural osmium for the hull? :)

One side effect of this wide range of masses for hulls is that for a given constant K (drive output in terawatts), the frigate is going to have 1/5 the thrust of the corvette, and the cruiser will have 1/25th the thrust of the corvette. (if two ships have the same engine output, the one with more mass will have a lower acceleration) That's a wide enough disparity that the setup is probably ungameable, and may prove problematic for novels. (This sort of disparity is why freighters in the Ten Worlds aren't sitting ducks. They're sitting ducks with two broken wings and both feet stapled to a stump, painted bright flourescent orange.)

When dealing with kinetics, that disparity of thrust really changes the available defenses and offensive capabilities. Fuel on the launch platform is a weapon, and the target's evasion parameter is set by how much thrust it can generate in a unit of time.

From Ken Burnside (2008)


Reduced to fundamentals, there are two basic shapes for your atomic rocket: the cylinder (cigar shape) and the sphere. Both have advantages and disadvantages. Of course matters are different in the totally unscientific world of media science fiction.

Any Freudian symbolism is the responsibility of the reader.

Flying saucers are not atomic rockets and are therefore beyond the scope of this website. If you want the absolute best information (including blueprints) of the most famous flying saucers from movies and TV, run, do not walk, and get a copy of The Saucer Fleet by Jack Hagerty and Jon Rogers. For rocket-like spacecraft, the last word is Spaceship Handbook by the same authors. Both books are solid gold.


The cylinder is more aerodynamic (for take-off and landing on planets with atmospheres), and allows the use of a smaller anti-radiation shadow shield (because from the point of view of the reactor the body of the ship subtends a smaller angle). It also lends itself well to the tumbling pigeon concept since it does not have to spin as fast as a sphere of the same volume in order to generate the same centrifugal gravity.

Drawbacks include a larger surface area, and a larger "moment of inertia" for yaw and pitch maneuvers (but a lower moment of inertia for roll maneuvers). This means it takes forever to point the ship's nose in different directions as compared to a sphere, which means poor maneuverability (See short story "Hide and Seek" by Sir Arthur C. Clarke for details). Larger gyros or stronger attitude jets will be needed. A faster roll rate is actually not of much use, unless you are trying to get a weapon turret to bear on an enemy ship (See the wargame Attack Vector: Tactical for details).

Cylinder shapes are also better if your ship has a so-called "spinal mount" weapon, that is, where instead of mounting a weapon on your ship you instead build the ship around the weapon. Such weapons are typically long and skinny, which fits the profile of a cigar more than a sphere.


Spheres have the largest enclosed volume for the smallest surface area of any shape, which is a major advantage where every gram of structural mass is a penalty. They also have a smaller moment of inertia for yaw and pitch maneuvers. Drawbacks are the opposite of the cylinder: they are only slightly more aerodynamic than a brick, they don't shadow shield well, and they are lousy tumbling pigeons.

Spheres also require more internal support structure than cylinder to handle the same acceleration load, particularly if you're going to be putting decks inside of it that rely on the structural framework of the spheroidal hull for rigidity. Cylinders under acceleration support themselves in the same manner as a skyscraper building, spheres need extra bracing to keep the equator from sagging. Of course this only becomes a problem if the acceleration is greater than a tenth of a gee, neither spheres nor cylinders have any problem coping with milligee acceleration.

On the other tentacle, if the shape has to be pressurized, like a fuel tank or a crew compartment, non-spherical shapes require more bracing mass and are more expensive to construct than spherical shapes.

Ken Burnside noted that another drawback of a sphere is that your internal volume is going to have a lot of "wasted dead spaces" near the hull. Odd shaped volumes that are what happens when you have an interior wall sectioning off part of the curved surface of the sphere. Anybody who has tried to lay out a floor plan inside a Buckminster Fuller geodetic dome house knows the problem.

Yet another thing to keep in mind is that using current manufacturing techniques, constructing a cylindrical hull costs about 70% of the cost of constructing a spherical hull with the same volume.

Why? Because it is more difficult to manufactured girders and plates that are bent compared to straight ones. A cylinder is constructed using straight stringers. The frames are circular, but all the frames have the same radius and radius of curvature. A sphere on the other hand uses curved stringers and circular frames all of different sizes (well, there are actually two frames of each given radius, but you understand the point I'm trying to make).

On most modern wet-navy warships, the hull plates are mostly straight, with a few bent in one dimension, and only a couple bent spherically in two dimensions. Bending is expensive. Eliminating the bending cost will require one and perhaps two breakthroughs in manufacturing technology.


Many early designs were cylindrical but also carrying a winged landing craft. This gave the spacecraft the appearance of an arrow or a spear. Granted, the landing craft was usually for the return trip to land the astronauts on Terra, but there were a couple intended for landing on Mars, and even one for landing on a hypothetical planet with an atmosphere around another star.

Now launching an spear-type spacecraft into orbit from Terra surface (or other planet with an atmosphere) has a problem of stability, due to the large landing craft wings. As Tim McGaha noted: "there's a reason the fletching isn't on the front of the arrow." This is why it is so important to ensure that the booster rocket has tail fins at the base that are as large (or larger) than the wings on the landing craft. Otherwise the rocket will tumble. Remember that the end of the ship the flames shoot out of should point toward the ground if you want to go to space. If it starts pointing toward space you are having a bad problem and you will not go to space today.

Stephan Jones points out: "The Titan missiles that would have been used to boost the proposed Dyna Soar rocket glider would have had fins strapped on, to counter the aerodynamic mess created by a winged body up top."

So I guess this means you use "arrow" configuration when boosting from the surface of a planet with an atmosphere, while you can get away with using "spear" configuration in vacuum.

Samples of arrow configuration.

These designs are spears. Either they are to be launched in vacuum, or the artist didn't get the memo.


Other ship geometries are possible. In Sir Arthur C. Clarke's Islands in the Sky there is an Terra-Mars passenger liner shaped like a doughnut (torus). The power plant and propulsion system is in the hole, and the ship spins for centrifugal gravity.

And there is also the open-frame design, where components are attached wherever is convenient and braced by girders. The von Braun Moonship from the Collier's article is an example.

Which Way Is Up?

Remember that in a spacecraft under acceleration, "down" is in the direction the exhaust is shooting (i.e., under acceleration the ship will seem like it is landed, sitting on its tail fins with the nose pointed straight up). The spacecraft living quarters will be arranged stacked like floors in a skyscraper. The floors will be at ninety degrees to the exhaust direction. Spacecraft arranged this way are called Tail-sitters. Most spacecraft are tail-sitters.

Usually spacecraft will NOT have their floors parallel to the exhaust direction, i.e., sideways like an aircraft or boat. This is the idiotic "Confusing-a-spaceship-with-an-passenger-airliner" school of ridiculous spacecraft design, found in science fiction with moronically bad science such as Star Trek, Star Wars, Battlestar Galactica and practically all the rest. Get it through your head: Rocket Are Not Boats people!

The only way this will work is with some sort of hand-waving paragravity. And even then why would anybody use such a stupid layout? If the paragravity fails, the rear wall abruptly becomes the floor, the floor becomes the wall, everybody falls to the new floor and breaks their ankles, and all the control panels are out of reach on the freaking ceiling. Now what, Flash Gordon? If you are going to be routinely dueling with Klingon battle cruisers, you do not want a minor weapons hit on the paragravity generator rendering the entire blasted ship inoperable. Just make the floors parallel to the exhaust direction like Heinlein intended, and you'll eliminate that failure mode. In any event, in the realm of spacecraft design, fail-deadly designs are frowned upon.

The producers of the TV series The Expanse understand this. In the first episode, a rescue party approaches the silent derelict ship the Scopuli.

But what's this? The ship's name plate looks upside down! Did the special effects artists make a mistake?

WRONG, you trekkie! Ships do not move through space on their bellies like an airplane. The producers of The Expanse got it exactly right. Ships move vertically like a sky-scraper. If we view it that way:

...suddenly we see that the name plate is perfectly correct.

The Expanse gets a big platinum star from me for that bit of accuracy. With the exception of the 2001 movies I don't recall anybody getting that correct (well, also maybe SyFy's Ascension, but that almost doesn't count). And that is only the start of things they got right. I love this show.

When Rockets Are Boats

As always there are exceptions

There are only two situations where it actually makes sense to use the passenger-airliner arrangement:

  • For spacecraft that actually do act like aircraft at some point, e.g., the Space Shuttle.
  • For cargo spacecraft that do not want to use a crane to move cargo up and down over tens of meters. Instead they become belly-landers.

Yes, an atmospheric lander that is transporting cargo will embody both situations.

The drawback is the crew spaces have to be arranged to accomodate both orientations. Just like the old NASA Space Shuttle. Or the FLIP ship.

Things get confusing if you have a spacecraft equipped with a centrifuge for artificial gravity. Under thrust with centrifuge deactivated, "down" is in the direction of thrust. With no thrust and centrifuge spinning, "down" is in the direction away from the spin axis. Under thrust with centrifuge spinning, "down" will be in a weird corner direction that is the vector sum of the two accelerations. There are ways of dealing with this.

There was an interesting hybrid in Larry Niven's World of Ptavvs. The "honeymoon special" was laid out sideways like an aircraft. The spacecraft resembled a huge arrow. It sat on the takeoff field like any aircraft while the passengers boarded. It would taxi down the runway and take off with JATO units, the "tail feathers" acting as wings. Once aloft, the scramjets kicked in, boosting the ship into Terra orbit. In space, the main fusion propulsion system was in the belly, not the tail. The ship flew through space sideways, which kept the direction of "down" still pointed at the floor. The wings also contained the heat radiators.


The other, far to the right, was a passenger ship as big as the ancient Queen Mary, one of the twin luxury transports which served the Titan Hotel.

Well, at least he had time to burn. As long as he was here, he might as well see what a human called a luxury liner.

He was impressed despite himself.

There were thrintun liners bigger than the Golden Circle, and a few which were far bigger; but not many carried a greater air of luxury. Those that did carried the owners of planets. The ramjets under the triangular wing were almost as big as some of the military ships on the field. The builders of the Golden Circle had cut corners only where they wouldn’t show. The lounge looked huge, much bigger than it actually was. It was paneled in gold and navy blue. Crash couches folded into the wall to give way to a bar, a small dance floor, a compact casino. Dining tables rose neatly and automatically from the carpeted floor, inverting themselves to show dark-grained plastic-oak. The front wall was a giant tridee screen. When the water level in the fuel tanks became low enough, an entrance from the lounge turned the tank into a swimming pool. Kzanol was puzzled by the layout until he realized that the fusion drive was in the belly. Ramjets would lift the ship to a safe altitude, but from then on the fusion drive would send thrust up instead of forward. The ship used water instead of liquid hydrogen, not because the passengers needed a pool, but because water was safer to carry and provided a reserve oxygen supply. The staterooms were miracles of miniaturization.

Like a feathered arrow the Golden Circle fell away from the sun. The comparison was hackneyed but accurate, for the giant triangular wing was right at the rear of the ship, with the slender shaft of the fuselage projecting deep into the forward apex. The small forward wings had folded into the sides shortly after takeoff. The big fin was a maze of piping. Live steam, heated by the drive, circled through a generator and through the cooling pipes before returning to start the journey again. Most of the power was fed into the fusion shield of the drive tube. The rest fed the life support system.

In one respect the “arrow” simile was inexact. The arrow flew sideways, riding the sun-hot torch which burned its belly.

“I’m sure one of them is a honeymoon special. It’s got a strong oxygen line in its spectrum.”

From WORLD OF PTAVVS by Larry Niven (1965)

The scientifically accurate layout of Niven's honeymoon special was commendably used in the otherwise forgettable movie Lifeforce (forgettable unless you are fond of nude lady space vampires). The British spacecraft HMS Churchill has its NERVA engine also located in the ship's belly instead of the tail.

This makes sense since the Churchill is a belly lander, as are all NASA derived space shuttles. Under NERVA thrust the direction of "down" matches the interior arrangement of the shuttle's habitat module. The fact that the ship appears to be moving through space sideways is of no concern.


(ed note: Dr. Floyd is riding up to the space station in the Pan Am Space Clipper)

Now, thought Floyd, we are on our own, more than halfway to orbit. When the acceleration came on again, as the upper stage rockets fired, the thrust was much more gentle: indeed, he felt no more than normal gravity. But it would have been impossible to walk, since “Up” was straight toward the front of the cabin. If he had been foolish enough to leave his seat, he would have crashed at once against the rear wall.

This effect was a little disconcerting, for it seemed that the ship was standing on its tail. To Floyd, who was at the very front of the cabin, all the seats appeared to be fixed on a wall topping vertically beneath him. He was doing his best to ignore this uncomfortable illusion when dawn exploded outside the ship.

From 2001 A SPACE ODYSSEY by Arthur C. Clarke (1969)


For what it is worth , the game GURPS Traveller: Starships defines the following terms:

  • Drive Axis: a line that originates in the center of thrust in the engines. Sometimes called the Thrust Axis. One end points in the direction the exhaust goes, the other end points in the direction the ship moves (Newton's "equal and opposite reaction"). Remember that "down" is in the same direction the exhaust goes. The drive axis should pass through the ship's center of gravity, otherwise under thrust the ship falls off its tail and spins wildly.
  • Tail Lander: a spacecraft whose decks are perpendicular to the drive axis. Almost all the ships described in this website are tail landers. SpaceX's Falcon line of boosters are tail landers.
  • Belly Lander: a spacecraft whose decks are parallel to the drive axis. The Space Shuttle is a belly lander.
  • Fore: in the direction of the drive axis towards the ship's nose. This is the direction of "up".
  • Aft: in the direction of the drive axis towards the ship's tail. This is the direction of "down".
  • Port: a line perpendicular to the drive axis passing through the spacecraft's main airlock. Ship's "left."
  • Starboard: a line perpendicular to the drive axis 180° from Port. Ship's "right."
  • Dorsal: a line perpendicular to the drive axis 90° from Port, counterclockwise when looking aft. Ship's "top" or "back."
  • Ventral: a line perpendicular to the drive axis 90° from Port, clockwise when looking aft. Ship's "bottom" or "belly."
  • Outboard: away from the drive axis.
  • Inboard: towards the drive axis.

The problem with the definition of port is that in a nuclear powered spacecraft, the logical place for the main airlock (and the ship docking point) is the ship's nose. Which makes "port" the same as "fore", thus ruining the nomenclature system. The idea is to have the directions at ninety degrees to each other, not coinciding. Some other distinguishing spacecraft feature will have to be used, but there doesn't seem to be any good candidates.

And what gets my goat is the terms "Dorsal" and "Ventral". They only apply to belly-landers. Applying those terms to a tail-lander is just propagating that accurséd "Confusing-a-spaceship-with-an-airbus" fallacy. Unfortunately there does not seem to be an alternate term for dorsal and ventral. Come to think of it, "Port" and "Starboard" are also airbus like.

Of course there will be a few spacecraft that actually are belly-landers, mostly cargo and aerospace shuttles. That is: spacecraft designed to have the cargo access hatch as near to the ground as possible, or spacecraft that can also operate as aircraft. Most spacecraft will be either tail-landers, or orbit-to-orbit ships that never land (but still have a tail-lander's internal layout).

On NASA spacecraft, they arbitrarily pick a direction for port. The spacecraft's X axis is the Drive axis, with +X in the direction the spacecraft accelerates and -X is the direction the exhaust goes. The astronauts lie on their backs, with eyes facing +X (up) and backs facing -X (down). Y axis passes through astronaut's left and right shoulders. +Y is right (starboard) and -Y is left (port). The Z axis passes through the astronaut's head and feet. +Z is in the feet direction (ventral, pfui!) and -Z is in the head direction (dorsal, ditto). This is important for the pilot to know when they are using rotation and translation controls.

If the ship has some sort of centrifugal gravity where spin gravity does not match thrust gravity, there will be some sort of jargon for "thrust gravity downward direction" and "spin gravity downward direction." The wet navy won't help you with this one, make it up yourself. If the centrifuge's spin axis happens to be the same as the drive axis, up is "inboard" and down is "outboard". Inside a centrifuge the directions "spinward" and "trailing" (anti-spinward) will be used, refering to the direction of centrifuge spin.


     "Mr. Archer — report to compartment nineteen, starboard, G-norm shell," the officer said abruptly, making him feel as though he were being inducted into the navy.
     "That's it," Groton said. "I'll drop you off — or would you rather find your own way?"
     "I would rather find my own way."
     Groton looked at him, surprised, but let him go. "G-norm is level eight," he said.

     He saw the numbers now: 96, 95, 94, each no doubt representing an apartment or office. Those on the right were marked P, those on his left S. Port and Starboard, presumably. Starboard being right, he must be heading for the stern.
     Of a torus? Exactly where were bow and stern in a hollow doughnut spinning in space?

     "But I have one crucially important question — "
     "To wit: which way is Stern?"
     Ivo nodded. "That is the question."
     "I'm surprised at you, den brother. Haven't you learned yet that your stern is behind your stem?"
     "My mind is insufficiently pornographic to make that association."
     "Take your bow. It's inevitable."
     Ivo smiled amiably, realizing that it was his turn to miss a pun of some sort. He would catch on in due course.

     He stopped off at the latrine — and realized suddenly that every toilet faced in the same direction. The arrangement was such that when a person sat, he had to face the "forward" orientation of the torus.
     "When you take your inevitable bow, your stern is sternward." he said aloud, finally appreciating Brad's pun — a pun inflicted upon the nomenclature of the entire station.

From Macroscope by Piers Anthony (1969)

You serve "in" a ship, not "on" one. "Abaft" means "behind", "forward" means "in front of." It is a "deck", not a "floor".

Pressure-tight walls are "bulkheads", pressure-tight doors are "pressure-tight doors." Non-pressure tight doors are just doors and non-pressure tight walls are just walls. Generally non-pressure type items are pretty flimsy. Doors in the decks (floor and ceiling) are "hatches.".

It's not a "restroom" it's a "head", it's not a "kitchen" it's a "galley." It's not the "dining room", it's the "mess deck" (unless it's for officers, then it's the "wardroom"). The "mess" refers to the crewmen currently eating on the mess deck. It's not a "bunk" its a "rack", it's not a "ceiling" it's an "overhead." It's not a "hallway" it's a "companionway" or "passageway", it's not the "stairs", it's a "ladder." And the "brow" is any walkway or catwalk leading to the main airlock.

These are all from the naval tradition, the air force jargon is totally different.

Navigation Lights

Aircraft have about nine different types of lights mounted on them. Most of them will be useful on a belly-landers, a few of them will be useful on a tail-sitter.

Port Light: red light on tip of port wing, visible in arc from 250° clockwise to 0° (110° wide arc centered on 305°)
Starboard Light: green light on tip of starboard wing, visible in arc from 0° clockwise to 110° (110° wide arc centered on 55°)
Aft Light: white light centered on tail, visible in arc from 110° clockwise to 250° (140° wide arc centered on 180°)
Meaning: Allows observer to determine what direction the aircraft is pointing in the black of night.
Notes: If red is on observers right and green is on the left, aircraft is heading straight for the observer. If only white is visible aircraft is heading away. If only red is visible aircraft is heading from right to left. Navigational lights are generally always on.
STROBE (also anti collision)
Light: very bright white pulsating strobe light. Two at each wing-tip (one fore, one aft), one on tail.
Meaning: Signals that the aircraft is entering an active runway. During flight it increases the aircraft's visibility.
Notes: On the ground strobes are off. When plane enter active runway strobes are activated. Strobes remain on during take-off, flight, landing, and are turned off when plane vacates the runway.
BEACON (anti collision)
Lights: Flashing red lights, one centered dorsal, one centered ventral.
Meaning: aircraft engines are running and aircraft is moving or will move soon. Warns ground crews to stay away from the engines or die. Alerts other aircraft that are on the move.
Notes: Lights flash to attract attention, they are red because that is the code for danger. Beacons are generally lit as long as the engines are powered up.
Illuminates wing so pilot can check wing at night for icing or other damage.
Helps pilot see area in front of plane as they taxi along the runway. Generally on nosegear.
Illumniates same area as taxi light but are much brighter. They are too blinding to other traffic to be used during taxi. Generally on nosegear.
Like taxi light except are angled left/right to assist aircraft turning. Generally on nosegear.
Very bright lights on wing to help pilot during landing. They illuminate the area where the plane is going to touch down. Sometimes airlines have procedure to turn them on below 10,000 feet or during climbs/descends.
Light illuminating the airline logo painted on the tail. The Starship Enterprise has lots of these, illuminating the name ENTERPRISE and various StarFleet insignia.

The Cygnus spacecraft uses LED navigational lights from ORBITEC. A standard set of ORBITEC nav light consists of five lights: a flashing red light on the port side, a flashing green on the starboard side, two flashing white lights on the top and one flashing yellow on the bottom side of the fuselage.

The SpaceX Dragon spacecraft has a red port, green starboard, and flashing white strobe light. The white strobe flashes in an irregular/random sequence so as not to confuse the flashing with a rotation.

Bullseye Address

In the US Navy, each compartment had a "bullseye" or Navy Ship Compartment Number. It is sort of a three-dimensional address of each space or compartment. While this is useful to keep new recruits from getting lost, the more important use is for damage control. Reporting a damaged location to, from, or between damage control parties must be rapid and unambiguous.

The compartment number is often stenciled on the walls and/or the doors.

Dangerous or important locations may be labeled by something like Semotic Standard symbols

1940-era Numbering

Every door, hatch and manhole  aboard the LST is labeled.  This metal sign provides certain information and learning to read these labels help one navigate through the vessel.  These labels were helpful in reporting emergencies because they utilized a standard method for giving describing any location aboard the ship.  Each label will have a combination of numbers and a name for the compartment.

The first number indicates the deck number.  The second number indicates that the opening is abaft of a particular frame and the last number indicates the number of the opening from the inboard out (port even numbers, starboard odd). A letter after the numbers indicates the use of the compartment.

 A-Supply and Storage L-Living Quarters
C-Control    M-Ammunition
E-Machinery T-Trunks and Passage
F-Fuel V-Voids

So in this example from a hatch aboard the LST:









So in English, 2-28-2 ESC TRUNK, would mean that the opening before you was an escape trunk, starting on the second deck, just aft of the twenty-eighth frame and is the first opening inboard out on the port side.  The second line, 4-28-2-T tells you the trunk continues all the way to the fourth deck, just aft of the twenty-eighth and here it is still the first opening from the inboard out.  This trunk gives access to: ELEC STORES 3-28-2-A or a store room for electrical parts on the third deck, which is aft of the twenty-eighth frame and is the first opening from the inboard out; and AUX ENG ROOM 4-28-O-E or the auxiliary engine room on the fourth deck aft of the twenty-eighth frame and the space is a machinery space.

(ed note: A different system will be needed for spacecraft, since they do not really have a port or starboard and the frames are parallel to the decks instead of perpendicular to them.)

USS Midway Bullseye

(ed note: this is an older form of US Navy compartment numbering)

USS MIDWAY - A "bullseye" is the three dimensional address of each space or compartment

A "bullseye" is the address of each compartment. This is an older form of the bullseye. The C indicates a location in the rear third of the ship. The "2" (in 208) shows we are on the second deck. The "08" indicates how far left or right we are from the keel or center of the ship. "FR 163" shows how far the forward bulkhead (wall) or frame is from the bow. The bottom line indicates which division is responsible for cleaning the space.

One more item: On a carrier the hangar deck is the ONE or first deck. Counting down the decks would be the TWO DECK (Second deck) , THREE DECK (third deck) etc.

Counting decks up from the hangar deck is the "01" (OH ONE) deck, the "02 (OH TWO DECK) etc. On MIDWAY the flight deck is the 03 deck.

from Bob Perry (2010)
Navy Ship Compartment Numbering

Compartments are numbered for identification to facilitate location. The identification number assigned locates each compartment specifically, and generally indicates the function and use of the compartment. Compartment numbers consist of four parts, separated by hyphens, for example 6-150-0-E, in the following sequence:

  1. Deck Number
  2. Frame Number
  3. Position in relation to centerline of ship
  4. Compartment use
Deck Number: The main deck is the basis for this numbering scheme and is numbered 1. The first deck below the main deck is numbered 2, and so on. The first horizontal division above the main deck is numbered 01, and the numbers continue consecutively for subsequent upper division boundaries. Compartments are numbered by the lowest deck within the space.

Frame number: The forward perpendicular is the basis for this numbering scheme and is numbered "0" (zero). "Frames" are consecutively numbered, based on frame spacing, until the aft perpendicular is reached. Forward of the forward perpendicular, frames are "lettered" starting from the perpendicular to the bull nose (A, B, C, etc.) while frames aft of the after perpendicular are "double lettered" to the transom (AA, BB, CC, etc.). Compartments are numbered by the frame number of the foremost bulkhead of the compartment. If this bulkhead is located between "frames," the number of the foremost "frame" within the compartment is used. Fractional numbers are not used except where frame spacing exceeds four feet. 

Frame spacing examples:


Position in relation to centerline: The ship's centerline is the basis for this numbering scheme. Compartments located so that the centerline of the ship passes through them are assigned the number 0. Compartments located completely to starboard of the centerline are given odd numbers, and those to port of centerline are given even numbers. The first compartment outboard of the centerline to starboard is 1, the second is 3 and so forth. Similarly, the first compartment outboard the centerline to port is 2, the second is 4 and so forth. There may be cases in which the centerline of the ship would pass through more than one compartment, all of which may have the same forward bulkhead number. Whenever this occurs, that compartment having the portion of the forward bulkhead through which the centerline of the ship passes is assigned the number 0 and the other carry numbers 01, 02, 03 etc.

Compartment Use: A capital letter is used to identify the assigned primary use of the compartment. Only one capital letter is assigned, except that on dry and liquid cargo ships a double letter identification is used to designate compartments assigned to carry cargo. Examples of compartment use are storage areas, various tanks, and living quarters. 

Some examples from NSTM 079 volume 2:

A Storage area
C Ship and Fire Control operating spaces normally crewed
E Machinery spaces which are normally crewed
F Fuel or Fuel Oil tanks
J JP-5 tank
L Living quarters
M Ammunition (stowage and handling)
Q Areas not otherwise covered
T Vertical access trunk
V Void

Example of Compartment Numbering

Given Compartment "6 - 150 - 0 - E," we can determine that it is located:

a) five decks below the Main Deck,
b) foremost bulkhead is at frame 150,
c) centered upon the centerline of the ship, and
d) is used as an engineering space.

In the science-fictional GURPS Traveller: Starships, they use the following system. Odd numbers are port, even numbers are starboard. Numbering is consecutive in order from inboard to outboard, fore to aft, dorsal to ventral.

Pressure Tight Doors

A pressure tight door is air-tight. Which will prevent you from dying from asphyxiation if the adjacent compartment is hulled by a meteor.

Ordinary doors in your house are not pressure-tight because generally there is the same Terra-normal atmospheric pressure on both sides.

This is not the case on passenger airplanes, submarines, or spacecraft. There the section that the people inhabit are at 101.3 kiloPascals of pressure or so, which will sustain human life. But outside the people section the pressure is very different, either higher or lower (or even zero), which will kill people. So a pressure-tight door is used, which tries to cope with this pressure difference.

Alistair Young pointed out to me that pressure doors are designed as "plug doors." The door is tapered, so one side has more surface area than the other (much like a bathtub drain stopper). The side with more surface area is designed to face the compartment with higher pressure. If you do not know which side will have more pressure (e.g., between two pressurized rooms but you do not know which room will be hulled by a meteor) then you'll need a submarine pressure hatch or something.


A plug door is a door designed to seal itself by taking advantage of pressure difference on its two sides and is typically used on aircraft with cabin pressurization. The higher pressure on one side forces the usually wedge-shaped door into its socket, making a good seal and preventing it from being opened until the pressure is released. Conversely, a non-plug door relies on the strength of the locking mechanism to keep the door shut.


The plug door is often seen on aircraft with pressurized cabins. Due to the air pressure within the aircraft cabin being higher than that of the surrounding atmosphere, the door seals itself closed as the aircraft climbs and the pressure differential increases. This prevents accidental opening of the door. In the event of a decompression, with there no longer being a pressure differential, the doors may be opened, and as such most airlines' operating procedures require cabin crew to keep passengers away from the doors until the aircraft has safely landed. On some aircraft the plug door opens partially inward, and through a complex hinge design can be tilted to fit through the fuselage opening, or the door may have locking hinged panels at the top and bottom edges that can make it smaller than the opening, so that it may be swung outward.

Plug doors are used on most modern airliners, particularly for the small passenger doors. However, since plug doors must open inward, the design is disadvantageous for cargo doors. Due to its large area, the cargo door on an airliner cannot be swung inside the fuselage without taking up a considerable amount of valuable cargo space. For this reason, these doors often open outward and use a locking mechanism with multiple pins or hatch dogs to prevent opening while in flight.


An inward opening plug hatch design was used on the Block I Apollo Command Module, because the explosive-release hatch of Gus Grissom's Mercury capsule Liberty Bell 7 prematurely blew at the end of the flight, causing the capsule to sink in the Atlantic Ocean and nearly resulting in Grissom's drowning. The Apollo cabin was pressurized at launch to 2 pounds per square inch (14 kPa) above standard sea level pressure, which sealed the hatch. A cabin fire during a 1967 Apollo 1 ground test raised the pressure even higher (29 pounds per square inch (200 kPa)), and made the hatch impossible to remove for the crew to escape. This killed Grissom along with his entire crew, Edward H. White and Roger Chaffee. Because of this, NASA decided to change to a quick-release, outward opening hatch on the Command Module.

Plug hatches were retained for the CM docking hatch and the two hatches on the Apollo Lunar Module, as the risk of fire in the low-pressure (5 pounds per square inch (34 kPa)) in-space atmosphere was much lower. Plug hatches were also used for the inner airlock hatch on the Space Shuttle. Currently, they are used on the International Space Station, as well as on the hatch between the Orbital Module and Descent Module of the Russian Soyuz spacecraft.

Deep-sea vehicles

Deep-submergence vehicles such as the Alvin use a plug hatch which is sealed inward by the pressure of the ocean water.

From the Wikipedia entry for PLUG DOOR


In naval terminology, "doors" lead from one side of a deck to another side of the same deck; hatches go between decks. In other words, doors are in the walls, hatches are in the floor and ceiling. Doors in non-pressure tight walls are "doors", doors in pressure-tight bulkheads are "pressure-tight door." On a spacecraft with no artificial gravity the distinction between openings in the walls and openings in the decks is sort of academic. Of course all the mechanical details are identical.

A small circular or oval access hatch is called a "scuttle." An escape hatch is usually a quick-acting scuttle (see below), because crew members trying to escape are generally in a hurry.

An opening into an uncrewed space for purposes of inspection and maintenance are called "manholes." This is generally into the interior of tanks and crawl spaces between equipment.

On wet navy vessels, doors and hatches leading into compartments containing flammables, weapons, high explosives, or petroleum engine fuel are forged out of bronze instead of iron. The latter can strike sparks when closing the hatch or turning the handwheel, with unfortunate results. Bronze is non-sparking. You might see something similar in a spacecraft hab module insanely designed to use pure oxygen as a breathing mix.


Pressure tight doors have "dogs", which are individual fasteners that clamp the door to maintain the seal with the door coaming. Ordinary doors do not have dogs, and cannot be "dogged down". On wet-navy ships, water-tight doors have eight dogging latches around the edges.

Some pressure tight doors have a clever arrangement where a single handle can close all the dogs simultaneously (a "quick acting" door). Otherwise the dogs have to be turned individually. Naturally the clever doors require more scheduled maintenance than the standard kind.

A pressure-tight door is a damage control barrier, while an ordinary door is an access control barrier.

Fancy pressure-tight doors will have some sort of indicator telling you if there is pressure or vacuum on the other side. The fanciest will have manometers, more bargain-basement models will just have a valve attached to a whistle. Turn the knob, and if it screeches there ain't no air over there.

On a high-tech spacecraft, there might be an automatic mechanism which will shut pressure-tight doors and hatches if it detects a hull breach or other unexpected drop in air pressure. There is a safety question of just how much the door will insist upon closing if an unfortunate crew member has a body part trapped. If the pressure drop is gradual enough or the well being of the crew is important enough, the door will be programmed to allow the crew member to open the door a bit and free themselves. Otherwise the blasted door will do it darnedest to amputate the unlucky crew member's limb (or head, or torso, or whatever). Also note that such automatic doors will contain complicated components and thus require lots of regular maintenance.

A standard watertight door as used by the US Navy has 8 dogging latches around the edges. These provide leverage to hold the door closed against flooding. The Navy considers these doors to be the most effective way to contain flooding, and doors will have a plaque on them with a letter showing at which level of preparedness the door gets shut and dogged. (A good discussion of those "material conditions" can be found at (navalmaterialconditions.htm)).

The problem with standard watertight doors is that they're a pain in the (posterior). Most often, they're not fully dogged down; sailors will use one dog to hold the door closed as they pass through it on regular duty. I have heard sailors literally curse whoever fully dogged a door.

The easiest kind of quick-acting door actually has a lever, instead of a wheel. The lever moves a bar, the bar moves other bars, and the bars pop the dogs simultaneously open or closed. While not as resistant to flooding as a standard WTD, it has the advantage that all dogs are more likely to be engaged, and so the Navy uses them in high-traffic areas. These are actually what I'd expect to see on out-atmosphere ships. The heavy doors you show on the page are designed for submarines, where they have to hold against very heavy pressures in case of flooding. Remember, water piles up an additional atmosphere of pressure every ten meters of depth, and submarines like the Los Angeles class commonly operate at depths of 200 meters.

I was a surface warfare girl, not a submariner, so I can tell you that the lighter, lever-actuated QAWTD (DSC_9950.jpg) have their machinery on the side that doesn't face a weather deck... or, in the case of a QATD that leads from one interior space to another, the machinery faces the inboard side, as flooding is more likely to come from outboard. I presume that Submarines use the same logic, but I don't know that to be the case.

I've heard my HT/DC buddies complain about servicing doors. More moving parts means more maintenance, of course, and more fiddling to make sure all the parts are working properly at the same time.

From Navy veteran Jennifer Linsky (2015)

      As soon as they were standing upright and held to the gray, unpainted hull plating by their boot magnets, and with the bulk of (their interstellar ambulance starship) Rhabwar hanging above them like a shining and convoluted white ceiling, the Captain began to speak.

     It said, 'There are only so many ways for a door to open. It can hinge in or outward, slide vertically or laterally, unscrew clockwise or anticlockwise or, if the builders are sufficiently advanced in the field of molecular engineering, an opening could be dilated in an area of solid metal. We have yet to encounter a species capable of the latter and, if we ever do, we'll have to be very careful indeed, and remember to call them 'sir'.

From CODE BLUE — EMERGENCY by James White (1987)

anti-buckling vents: vents, either permanent or automatically opening (using, for example, rupture disks) in the event of a significant pressure differential across them, installed in non-spacetight bulkheads and deckheads to prevent them from behaving as de facto spacetight compartmentalizations while lacking the structural strength to serve in that role.

After a number of incidents in which decompressions caused by hull punctures and the resulting pressure differentials caused crumples and collapses of non-spacetight bulkheads, severing piping and cable runs passing through or along those bulkheads, anti-buckling vents became a standard component of celestime architecture.

(For this reason, it is important to immediately follow decompression procedures when the alarm sounds, whether or not the source of decompression appears to be in the current compartment.)

(ed note: Mr. Young had noted to me earlier:

This same reading has me thinking about decompression — specifically, the DC-10 incidents in which the blowout of the outward-opening cargo door decompressed the hold, but the loss of the aircraft was due to the subsequent buckling of the cabin floor from the pressure differential, severing control runs and making the aircraft uncontrollable. Ultimately solved by adding vents in the floor to make the cabin equalize pressure with the (decompressed) hold should the incident recur.

Seems like this could also be applicable to spacecraft. Scenarios where it's better to let the next compartment decompress rather than risk buckling a bulkhead with important lines running through/along it.)


Cargo door problem and other major accidents

Main articles: American Airlines Flight 96 and Turkish Airlines Flight 981

Instead of conventional inward-opening plug doors, the DC-10 has cargo doors that open outward; this allows the cargo area to be completely filled, as the doors do not occupy otherwise usable interior space when open. To overcome the outward force from pressurization of the fuselage at high altitudes, outward-opening doors must use heavy locking mechanisms. In the event of a door lock malfunction, there is greater potential for explosive decompression.

On June 12, 1972, American Airlines Flight 96 lost its aft cargo door above Windsor, Ontario. Before takeoff, the door appeared secure, but the internal locking mechanism was not fully engaged. When the aircraft reached approximately 11,750 feet (3,580 m) in altitude, the door blew out, and the resulting explosive decompression collapsed the cabin floor. Many control cables to the empennage were cut, leaving the pilots with very limited control of the aircraft. Despite this, the crew performed a safe emergency landing. U.S. National Transportation Safety Board (NTSB) investigators found the cargo door design to be dangerously flawed, as the door could be closed without the locking mechanism fully engaged, and this condition was not apparent from visual inspection of the door nor from the cargo-door indicator in the cockpit. The NTSB recommended modifications to make it readily apparent to baggage handlers when the door was not secured, and also recommended adding vents to the cabin floor, so that the pressure difference between the cabin and cargo bay during decompression could quickly equalize without causing further damage. Although many carriers voluntarily modified the cargo doors, no airworthiness directive was issued, due to a gentlemen's agreement between the head of the FAA, John H. Shaffer, and the head of McDonnell Douglas's aircraft division, Jackson McGowen. McDonnell Douglas made some modifications to the cargo door, but the basic design remained unchanged, and problems persisted.

On March 3, 1974, in an accident circumstantially similar to American Airlines Flight 96, a cargo-door blowout caused Turkish Airlines Flight 981 to crash near Ermenonville, France, in the deadliest air crash in history at the time. The cargo door of Flight 981 had not been fully locked, though it appeared so to both cockpit crew and ground personnel. The Turkish aircraft had a seating configuration that exacerbated the effects of decompression, and as the cabin floor collapsed into the cargo bay, control cables were severed and the aircraft became uncontrollable. Investigators found that the DC-10's relief vents were not large enough to equalize the pressure between the passenger and cargo compartments during explosive decompression. Following this crash, a special subcommittee of the United States House of Representatives investigated the cargo-door issue and the certification by the Federal Aviation Administration (FAA) of the original design. An airworthiness directive was issued, and all DC-10s underwent mandatory door modifications. The DC-10 experienced no more major incidents related to its cargo door after FAA-approved changes were made.

From the Wikipedia entry for McDonnell Douglas DC-10

Submarine Pressure-Tight Doors

Submarine watertight bulkhead door are entertaining, though they are probably far too wasteful of mass to use on a real spacecraft. But they are instructive. And they are so retro. The technical term is "quick-acting water-tight doors", as opposed to the doors with "dogs."

These are damage control barriers for use when the hab module's hull is breached. As such it is uncertain which side of the door will suddenly contain vacuum. However, in an airlock (or other situation where you are pretty sure you know which side will always have pressure), as a safety measure you want the door to open such that the air pressure will be constantly pushing the door safely shut instead of trying to blow the door open and kill everybody. And to prevent morons from opening a door leading to vacuum, since they cannot possibly tug open something being held shut by 14.7 pound per square inch. If you have a low-IQ individual on your ship who can pull with over 19 metric tons of force, you have a bigger problem than inadequate safety on your pressure-tight doors.

As a general rule you'll want your hab module doors set so that they close in the outboard direction and open inboard. Presumably the drop in air pressure will be from a catastrophic hole in the hull, not the center of the spacecraft. So at a door connecting two compartments, the compartment closer to the hull is more likely to be in vacuum during a disaster. This will not always be true, but that's the way to bet. Thus the air pressure will be helpfully holding the door shut.

On wet-navy surface ships they mount doors such that the gears and mechanism of the quick-acting-door are on the dry side so they are not exposed to corrosive seawater. This means the machinery faces the inboard side, because presumably the water will be coming from a breach in the hull on the outboard side. Whether this is a concern on a spacecraft depends upon how much wear and tear the machinery suffers under vacuum.

Keep in mind that submarine doors have to contain an order of magnitude more pressure than a spacecraft door ever will. That's why they look like bank vault doors. A spacecraft pressure door will only need to cope with one atmosphere of pressure or so, while a submarine at 200 meters depth needs to be able to handle 20 atmospheres. Former Navy Jennifer Linsky is of the opinion that a spacecraft would probably use pressure doors similar to the quick-acting-door pictured above as opposed to these massive submarine doors.

I have yet to locate any description about how submarine bulkhead doors operate, so I had to look at lots of images and use my raw powers of deduction. Besides, the quickest way to find the answer to something on the internet is to post an inaccurate explanation. Experts will come boiling out of the woodwork eager to tell you just how wrong you are.

I got nowhere fast with analyzing the images until I realize there were two types of doors that looked similar. Since I do not know the proper terminology, I'm dubbing them "Innie" and "Outie", much like navels.

  • Innie
    • When the door is opened, the side of the door revealed is concave (full of gears and machinery). When door is shut you see a smooth convex surface.
    • The strike plates are bulges in the door frame
    • Actuators are attached to part of latch farthest from door body
    • The latches rotate towards the door body to engage the strike plate
  • Outie
    • When the door is opened, the side of the door revealed is convex (with no gears exposed). When door is shut you see a concave surface full of gears.
    • The strike plates are curved arching knobs
    • Actuators are attached to part of latch nearest to door body
    • The latches rotate away from the door body to engage the strike plate

How Quick-Acting Water-Tight Doors Work

Color Key:

  • Red: Handwheel and Worm. The handwheel can look like a wheel, a cross bar, or a wheel with a bar extending from the center.
  • Yellow: Worm gears and levers
  • Green: Actuators
  • Blue: Latches

The mechanism of Innie and Outie doors work pretty much the same, with the exception that the latches rotate in opposite directions.

The wheel or crossbar (red) in the center of the door is spun. This rotates the worm of a worm drive (not shown).

The worm engages the four worm gears (yellow) attached to four levers, moving the levers into extended position (far ends of the levers move further away from center).

The ends of the levers push four oddly-shaped actuators (green) away from the center of the door body and closer to the door body edge.

The actuators push on the edge of pivoted latches (blue). The latches rotate on their pivots to engage the strike plates. Innie latches rotate in the opposite direction from Outie latches. To do so, the Innie door has the actuators attached to the latches on the part of the latch furthest from the door body, while Outie actuators are attached to part of latch closest to door body.

"How do you know it doesn't have a leak?" Fred wanted to know.

"Sorry to sound stupid, but this space living's new to me," Tom remarked. "So it has a leak? So what?"

"Do you know there's pressure on the other side of that door?" Fred asked.

"Why, there's bound to be! We sealed it pressurized," Stan said.

"Doesn't mean it still has pressure," Fred explained. He moved to the door and to the control panel next to it. "Look, the secret of living to a ripe old age out here involves a firm belief in Murphy's Law. Never take anything for granted, especially when your life may depend on it. Always assume that something's malfunctioned until you know it hasn't. Suppose the med module sprung a leak during boost to LEO Base, or when they were transferring it to a Cot-Vee, or when they unloaded it here and docked it to GEO Base. What would be the consequences?"

"We'd have lost a lot of our equipment, to say nothing of most of the Pharmaceuticals and lab reagents in there," Dave ventured.

"Plus your life if you managed to get that door opened with vacuum on the other side of it."

"It's not supposed to open with vacuum on the other side of it."

"Hell of a lot of people got killed out here because something was 'supposed' to be fail-safe, Dave. Everybody, look here at the little panel alongside the door. There's one of these at every hatch. If you ignore it, you're likely to kill yourself by what we might call 'traumatic abaryia,' which is a word I just made up, Doc, and that you can steal if you want. Crack that door with vacuum on the other side of it, and the pressure in this module would drop in less than a minute to a level that would kill you. The automatic door on the inboard end of the living module would automatically seal. Hell, Pratt can't afford to let everybody in GEO Base get killed just because some damned fool forgot to look at the tell-tale alongside the door before he tried to open it. Sure, it's supposed to be fail-safe—but don't you ever believe it! You stay alive out here by placing absolutely no trust whatsoever in safety devices that were designed by engineers sitting down on dirt. They aren't going to get killed if it doesn't work. Fired maybe, but they're still alive. You all listen to me. You're part of the same team I'm on, and we can't afford to lose a single one of you. Especially you, Doc. I may not be able to keep you from getting shortened a foot or two, but I may be able to keep you alive."

The pressure indicator showed there was indeed pressure in the med module, but Fred told them not to believe even that. "It could be frozen or have malfunctioned in sixty different ways. Next step is to check the test port in the door."

Fred showed them how to crack the test port on the door and listen for the whistle. Every door and hatch had such a test port, a very simple device that couldn't fail: a small opening that could easily be opened and just as easily shut and sealed again. Any pressure differential across the door would cause the test port to whistle.

"We're in luck. The pressure held," Fred told them.

From Space Doctor by Lee Correy (G. Harry Stine) 1981


An airlock is a way for an astronaut (presumably dressed in a spacesuit) to exit the pressurized habitat module without all the atmosphere blowing out into the limitless vacuum of space.

Basically it is a chamber with two airtight hatches, which do not open simultaneously. One hatch opens into the hab module, one opens into space, and the pressure inside the chamber can be switched from ship pressure down to vacuum. Before opening either hatch, the pressure inside the chamber is equalized with the environment beyond. This is called "cycling" an airlock.

On the International Space Station, the rule is that the pressure inside the airlock must be below 3.5 kPa before you can open the outer hatch to space. Otherwise the pressure inside the airlock might break the hatch hinges.

As a mundane analogy, imagine a spaceship is a house, a space suit is winter coat, vacuum is the bitter cold of winter, air is the warmth inside the house, and the airlock is an entryway (the "warmth-lock"). To leave the house, you walk into the entryway, close the door behind you so the heat does not escape, put on your winter coat hanging in the coat closet, open the front door into the cold of winter, leave the house, and close the front door behind you. Just like an airlock.

When cycling down to vacuum all the air in the lock is stored in tanks, of course. Just venting it to space is a criminal waste of limited breathing mix. This would not be done unless it was an emergency or if it was an incredibly primitive airlock. Even with a reasonably designed airlock there is going to be some small unavoidable breathing mix loss with each cycle.

Very small or very cut-rate spaceships might not have an airlock. They take up lots of room and are expensive. They might be optional on a one-man Belter asteroid mining ship. Of course this means the pilot will have to put the toothpaste and any other pressure sensitive supplies into a pressurized locker before they vent the entire hab module and open the hatch. An example is the Lunar Module from NASA's Apollo program.

A stripped-down variant on the airlock is the "suitport". Instead of a chamber, the backpack of a space suit attaches to the ship's hull. An astronaut enters the suit by crawling through the backpack, seals the inner door, then detaches from the hull. It requires much less mass and volume than a full airlock. On the other hand, they are difficult to design if the atmospheric pressure inside the ship/spacestation is not the same as inside the suit. Soft suits commonly have lower pressure than the habitat.

Besides the usual cargo lock we had three Kwikloks. A Kwiklok is an Iron Maiden without spikes; it fits a man in a suit, leaving just a few pints of air to scavenge, and cycles automatically. A big time saver in changing shifts. I passed through the middle-sized one; Tiny, of course, used the big one. Without hesitation the new man pulled himself into the small one.

From Delilah and the Space-Rigger by Robert Heinlein (1949)


1. Personnel must wear vacuum suits before exiting the starship if so indicated by crimson-caution telltales. (Any exceptions must possess “vacuum-capable” endorsement countersigned by Environmental Systems Engineer.) Follow instructions posted in airlock chamber.

2. In an emergency, caution enforcement system may be disabled by opening emergency controls panel. (Alarm will sound in DCC.) Follow procedures posted within. Always attempt egress through interior hatch first, exterior hatch second.


Do not ignore any amber-test or crimson-caution telltales. Spacetight doors may not have properly sealed and/or chamber may not have reached safe pressure differential. Always wait for blue-go “disembark” indicator before trying to exit.

When using emergency controls, always check “hatch sealed” test lights and manual indicators before using manual pressurization override controls. As you proceed, constantly monitor pressurization and differential-pressure gauges, located within emergency controls panel.

In the event of damage or mechanical failure, spare parts and tools for emergency repairs are located beneath the emergency controls panel secondary door.

From AND DON’T HOLD YOUR BREATH (IT NEVER HELPS) by Alistair Young (2014)

(ed note: images are from JSC-20466 EVA Tools and Equipment Reference Book Rev. B, November 1993)

The airlock is normally located inside the middeck of the spacecraft's pressurized crew cabin. It has an inside diameter of 63 inches, is 83 inches long and has two 40-inch- diameter D-shaped openings that are 36 inches across. It also has two pressure-sealing hatches and a complement of airlock support systems. The airlock's volume is 150 cubic feet.

The airlock is sized to accommodate two fully suited flight crew members simultaneously. Support functions include airlock depressurization and repressurization, extravehicular activity equipment recharge, liquid-cooled garment water cooling, EVA equipment checkout, donning and communications. The EVA gear, checkout panel and recharge stations are located on the internal walls of the airlock.

The airlock hatches are mounted on the airlock. The inner hatch is mounted on the exterior of the airlock (orbiter crew cabin middeck side) and opens into the middeck. The inner hatch isolates the airlock from the orbiter crew cabin. The outer hatch is mounted inside the airlock and opens into the airlock. The outer hatch isolates the airlock from the unpressurized payload bay when closed and permits the EVA crew members to exit from the airlock to the payload bay when open.

Airlock repressurization is controllable from the orbiter crew cabin middeck and from inside the airlock. It is performed by equalizing the airlock's and cabin's pressure with equalization valves mounted on the inner hatch. The airlock is depressurized from inside the airlock by venting the airlock's pressure overboard. The two D-shaped airlock hatches open toward the primary pressure source, the orbiter crew cabin, to achieve pressure-assist sealing when closed.

Each hatch has six interconnected latches and a gearbox/actuator, a window, a hinge mechanism and hold-open device, a differential pressure gauge on each side and two equalization valves.

The 4-inch (10 cm) diameter window in each airlock hatch is used for crew observation from the cabin/airlock and the airlock/payload bay. The dual window panes are made of polycarbonate plastic and mounted directly to the hatch by means of bolts fastened through the panes. Each hatch window has dual pressure seals, with seal grooves located in the hatch.

Each airlock hatch has dual pressure seals to maintain pressure integrity. One seal is mounted on the airlock hatch and the other on the airlock structure. A leak check quick disconnect is installed between the hatch and the airlock pressure seals to verify hatch pressure integrity before flight.

The gearbox with latch mechanisms on each hatch allows the flight crew to open and close the hatch during transfers and EVA operations. The gearbox and the latches are mounted on the low-pressure side of each hatch; with a gearbox handle installed on both sides to permit operation from either side of the hatch.

Three of the six latches on each hatch are double-acting and have cam surfaces that force the sealing surfaces apart when the latches are opened, thereby acting as crew assist devices. The latches are interconnected with push-pull rods and an idler bell crank that is installed between the rods for pivoting the rods. Self-aligning dual rotating bearings are used on the rods for attachment to the bellcranks and the latches. The gearbox and hatch open support struts are also connected to the latching system by the same rod/bellcrank and bearing system. To latch or unlatch the hatch, the gearbox handle must be rotated 440 degrees.

The hatch actuator/gearbox is used to provide the mechanical advantage to open and close the latches. The hatch actuator lock lever requires a force of 8 to 10 pounds through an angle of 180 deg rees to unlatch the actuator. A minimum rotation of 440 deg rees with a maximum force of 30 pounds applied to the actuator handle is required to operate the latches to their fully unlatched positions.

The hinge mechanism for each hatch permits a minimum opening sweep into the airlock or the crew cabin middeck. The inner hatch (airlock to crew cabin) is pulled or pushed forward to the crew cabin approximately 6 inches. The hatch pivots up and to the right side. Positive locks are provided to hold the hatch in both an intermediate and a full-open position. A spring-loaded handle on the latch hold-open bracket releases the lock. Friction is also provided in the linkage to prevent the hatch from moving if released during any part of the swing.

The outer hatch (airlock to payload bay) opens and closes to the contour of the airlock wall. The hatch is hinged to be pulled first into the airlock and then forward at the bottom and rotated down until it rests with the low-pressure (outer) side facing the airlock ceiling (middeck floor). The linkage mechanism guides the hatch from the closed/open, open/closed position with friction restraint throughout the stroke. The hatch has a hold-open hook that snaps into place over a flange when the hatch is fully open. The hook is released by depressing the spring-loaded hook handle and pushing the hatch toward the closed position. To support and protect the hatch against the airlock ceiling, the hatch incorporates two deployable struts. The struts are connected to the hatch linkage mechanism and are deployed when the hatch linkage is rotated open. When the hatch latches are rotated closed, the struts are retracted against the hatch.

The airlock hatches can be removed in flight from the hinge mechanism using pip pins, if required.

The airlock air circulation system provides conditioned air to the airlock during non-EVA periods. The airlock revitalization system duct is attached to the outside airlock wall at launch. Upon airlock hatch opening in flight, the duct is rotated by the flight crew through the cabin/airlock hatch, installed in the airlock and held in place by a strap holder. The duct has a removable air diffuser cap, installed on the end of the flexible duct, which can adjust the air flow from 216 pounds per hour. The duct must be rotated out of the airlock before the cabin/airlock hatch is closed for airlock depressurization. During the EVA preparation period, the duct is rotated out of the airlock and can be used for supplemental air circulation in the middeck.

To assist the crew member before and after EVA operations, the airlock incorporates handrails and foot restraints. Handrails are located alongside the avionics and ECLSS panels. Aluminum alloy handholds mounted on each side of the hatches have oval configurations 0.75 by 1.32 inches and are painted yellow. They are bonded to the airlock walls with an epoxyphenolic adhesive. Each handrail has a clearance of 2.25 inches between the airlock wall and the handrail to allow the astronauts to grip it while wearing a pressurized glove. Foot restraints are installed on the airlock floor nearer the payload bay side. The ceiling handhold is installed nearer the cabin side of the airlock. The foot restraints can be rotated 360 degrees by releasing a spring-loaded latch and lock in every 90 degrees. A rotation release knob on the foot restraint is designed for shirt-sleeve operation and, therefore, must be positioned before the suit is donned. The foot restraint is bolted to the floor and cannot be removed in flight. It is sized for the EMU boot. The crew member first inserts his foot under the toe bar and then rotates his heel from inboard to outboard until the heel of the boot is captured.

There are four floodlights in the airlock.

If the airlock is relocated to the payload bay from the middeck, it will function in the same manner as in the middeck. Insulation is installed on the airlock's exterior for protection from the extreme temperatures of space.

From NASA SHUTTLE REFERENCE MANUAL: Orbiter Structure: Airlock

NICK T: I saw Gravity the other day and while visually and emotionally compelling, and besides the liberties taken with orbits, something else struck me as unrealistic, but I'm not sure if it is or isn't: the apparent lack of physical security on spacecraft. As for its counterpart, I have a vague notion there is ferocious information security so someone with a transmitter can't deorbit a satellite.

While getting into orbit is something of an obstacle, are there no locks on airlocks? Is space like Canada?

TildalWave: I could give you detailed technical specification of all the airlocks, hatches and whatnot that has access to and from the ISS (yes, there are several, although I suspect the movie tried to present the Quest joint airlock?), So I think this is best left to be explained by those that were both there, and have seen the movie. For example, Leroy Chiao (@AstroDude on Twitter), a former NASA astronaut and commander of the International Space Station (ISS) said in his review of the movie for

… there is no way to enter an airlock from the outside, unless it had already been prepared for such an entry. The inner hatch would have to already be sealed.

Additionally, again from my experience on Twitter, I've seen it mentioned that the repressurisation process in the movie took perhaps 3 seconds. That is again highly inaccurate and the repressurisation of the crew lock takes roughly 45 minutes, but can be somewhat hurried in case of an emergency. It would most certainly not be 3 seconds from 0 psi (0 kPa) to 14.7 psi (101 kPa) that is the ISS internal atmospheric pressure on astronauts' return from their EVA (Extravehicular Activity).

For example, when Luca Parmitano's helmet started filling with water from his PLSS (Portable Life Support Unit) and he rushed back to the airlock, it took many agonizing minutes to repressurize it, as he wrote in one of his blog posts. If it took 3 seconds, or thereabouts, that would literally feel like being inside an explosion. This repressurisation process can be somewhat appreciated by looking at the reverse, the depressurisation process for the Quest joint airlock:

The usual pressure inside the ISS is 1 bar, though in the Quest airlock this is 0.7 bar during depressurisation in connection with nitrogen purging. When the astronauts are in the crewlock ready to start their EVA this pressure is reduced first to 0.35 bar when a leak check is performed on the suits. If this is ok the crewlock is reduced in pressure down to 0.2 bar. The final depressurisation to vacuum occurs through venting through a valve in the EVA hatch. The hatch can now be opened and the EVA can begin.

The hatch remains open for the duration of the EVA for several reasons, among which also for astronauts to be able to return in an emergency, and also to conserve the volumes of the nitrogen and oxygen in the external tanks that are used for nitrogen purge, repressurisation and also to recharge the EMUs (Extravehicular Mobility Unit, of which there are two types onboard the ISS).

And no, none of the ISS external airlocks or berthing hatches open from the outside, so no keys there. Not the Russian docking ports on Poisk, Pirs, Rassvet or Zvezda service module, not on Leonardo cargo bay, Tranquility, Harmony, the JAXA's Kibō that has an airlock with a key release of the CYCLOPS (Kinetic Launcher for Orbital Payload Systems) small satellite launch system but from within the ISS, and not on the Quest joint airlock. The only hatches that have a sliding opening door that opens from the outside are on the resupply vehicles (there's many, so I'll spare you with the list), that are mostly tightened in place with a set of bolts that need to be removed with a torque wrench.

Anyway, I didn't see the movie yet, but I guess its script likely wouldn't work, if they tried to make it 100% accurate. The preparations for EVA take roughly one day with all kinds of, in terms of motion pictures, rather boring procedures that I don't expect anyone would be too interested in. Not in an action movie at least. Maybe in a documentary, but even there it likely wouldn't take longer than perhaps 10 minutes to go through it? So my advice would be that if you've forked out for the tickets, then make the best of it and enjoy the ride. ;)

Organic Marble: Locks aren't needed, because it is physically impossible to open the hatch from outside unless the airlock is depressurized.

All airlock hatches are inward opening (the STS Orbiter side hatch was not an airlock hatch) and the air pressure inside amounts to tons of force keeping the hatch closed (the back of my envelope says about 144 tons of force).

For example, check out this picture of the ISS US airlock. That white thing flipped up is just a thermal cover. You can see the actual outer hatch hinges behind Cassidy and the hatch is down behind his backpack.

Hobbes: There are three major arguments against physical security on manned spacecraft:

  1. A lock is a point of failure. Given the dire consequences of an astronaut being locked out after a spacewalk, you need to make really sure people can get in in an emergency. So adding a lock would make the hatch design a lot more complicated, for no added value (see point 2).

  2. Hijacking a manned spacecraft is really unlikely. There are only 3 nations on Earth capable of launching a manned mission. If one of them decides to hijack another nation's mission, they'd have an international crisis on their hand, if not a war. So the hijacker pays a huge price, for no benefit (see point 3).

  3. Why bother? Manned missions are largely peaceful scientific missions. If you want to take part, pay a few dozen million and you can send an astronaut up to the ISS. No need to kick in the door. Also, there's no point in hijacking a manned mission. Say you've taken over a spacecraft: what are you going to do with it? There's no benefit to hijacking.

For unmanned satellites the situation can be more complicated, esp. in the case of military satellites. It's likely those have countermeasures against remote tampering (hacking) on board.

Physical security? Again, unlikely. Launching a space mission isn't covert: anyone can track your spaceship, so if you launched a mission to hijack an enemy's satellite, they'd know it's you. Their response would be to bomb your launch site, so you'd get to do this no more than once. Again high cost, little benefit. The only problem military satellites face is getting blown up by an antisatellite missile, and those are difficult to defend against. A ballistic missile defence system is huge and expensive, to add that to a satellite would add several tons of weight and cost a fortune.



N2 79%, O2 21%
< 25.1 kPa: Anoxia
101.3 kPa: Normal
> 254.0 kPa: O2 toxicity
> 400 kPa: N2 narcosis

O2 100%
< 5.3 kPa: Anoxia
32.4 kPa: Normal
> 53.3 kPa: O2 toxicity

10 secs until unconscious
90 secs until fatal damage
maybe Ebullism
The Bends

< 6.3 kPa w/bare skin
     (Armstrong Limit)
     (Kittinger Syndrome)
< 2.0 kPa w/Pumpkin Suit
Never w/space suit

< 3/5 kPa can safely open ISS outside airlock hatch without damaging the hinges

"Spacing" or "airlocking" is a nasty form of execution, where the victim is forced into the airlock while not wearing a spacesuit. The airlock is then cycled, hurling the victim into airless space where they suffocate. Sometimes this is made as a threat, e.g., "Follow my orders you scum, or I'll throw you out the airlock stark naked!"

Spacing is more or less the equivalent of a pirate making a victim walk the plank. The more merciful way is to put them in the airlock in ordinary clothing, or nude. They will be unconsious in about ten seconds and dead in 90. The more sadistic way is to have them in a spacesuit with about an half an hour's worth of oxygen, so they can be tortured by the reality of their approaching demise as they watch the oxygen gauge slowely drops to zero.

Some writers have the dramatic idea of opening the airlock while it is still pressurized so as to blow the victim into space. This avoids the necessity for a space suited person to enter the lock and kick the body out. However standard air pressure is not strong enough to blow the victim into space. You need about ten atmospheres for that. Also the victim will probably be frantically hanging onto anything they can grab inside the airlock in any event. Using ten atmospheres of air pressure to remove the executed is probably a waste of good breathing mix.

A more civilized version of this is when somebody happens to die onboard the ship. The airlock can be used to send the dear departed on their way by space burial.


"You know what the folks back home don't understand, the ones who've never left Earth, is just how dangerous space can be. Aside from incidents like this, just the everyday reality of living your days and nights in a big tin can surrounded by a vacuum."

"I remember my first time on a transport, on the Moon-Mars run. I was just a kid, maybe seventeen. A buddy of mine was messing around, and zipping through the halls, and he hid in one of the airlocks. I don't know, I guess he was gonna try to scare us or something, I don't know... But just as I got close, he must have hit the wrong button because the air doors slammed shut, the space doors opened, and he... just flew out into space."

"And the one thing they never tell you is that you don't die instantly in vacuum. He just hung there against the black like a puppet with his strings all tangled up... or one of those old cartoons where you run off the edge of the cliff and your legs keep going."

"You could see that he was trying to breathe, but there was nothing. The one thing I remember when they pulled in his body... his eyes were frozen."

"A lot of people make jokes about spacing somebody, about shoving somebody out an airlock — I don't think it's funny. Never will."


      Channel B, the all-talk channel on the intercom:

     "Hey, when we get back to base, what're we going to say when they ask us why we couldn't catch the bogie?"
     "Our butterfly net had a hole in it?"
     "That's very funny —hey, aren't you the guy who, when they start insulting your ship in the bars, you start nodding your head and agreeing?"
     "Yeah, well —I don't like to argue with my own shipmates."
     "Has anyone ever noticed there something weird about (first officer) Korie? —Like he's always calculating?"
     "There's something weird about everybody on this ship. That's why we're here."
     "Hey, does anybody know what the penalty for mutiny is?"
     "Last I heard, it was death by spacing."
     "Hmm—that's getting more attractive every day."
     "Forget it. The last one to try taking over the ship was Captain Brandt."
     "And what happened to him?"
     "Korie sent him to his room."
     "That bastard—that's pretty harsh treatment for an old man."

From YESTERDAY'S CHILDREN by David Gerrold (1972)

The Autocrat of Ceres sat in his very plain chair in the very plain compartment, and regarded the two very nervous people before him with regret. He was going to have to kill them.

“I’m very much afraid,” he said, “that I don’t have much choice in the matter. You were each expected to show cause why I should not put you to death. I have seen no such cause shown. Instead I have seen two people who have allowed a petty squabble over mining rights to degenerate into another useless rock war. It is your egos, and not the mining rights, that prevent justice in this case. And the Autocrat’s Law requires me to remove all obstacles to justice. Case closed.” The Autocrat nodded toward his marshals, and they stepped forward.

The plaintiff screamed, the defendant fainted. The marshals were good at what they did. Within seconds, both of the claimants were restrained, sedated, and being taken away, toward the Autocrat’s very plain, very famous, very deadly airlock. The one where pressure suits were not allowed. The place to which human obstacles to justice were quite literally removed.

Justice, as with many other things in the Belt, was in short supply, and when available, was not of the best quality—too rough, too harsh and too rushed. To the Inner System dandies who visited now and again, the Autocrat’s Law seemed barbaric, violent and vengeful. But to the Belters, who had no other source of justice, the Autocrat’s Law represented civilization itself. In all the wide, wild, ungovernable vastness of the Asteroid Belt, they knew there was one place, one name, one law that all could trust. Only the Autocrat’s Law could protect them against themselves. Harsh and final it might be, but so too was it impartial.

For the Belters knew the Belt was huge—ungovernably huge. There could be no law when law enforcement was impossible, and no conventional enforcement was possible when the population density was something less than one crotchety misanthropic old coot per million cubic kilometers. It was easy for other things besides law to get lost in the midst of all that vast expanse.

Things like sanity, order, trust, proportion. Megalomania was an easy disease to catch when a man or a woman could have a world—albeit a very small one—for the effort of landing on it. And if your own world, why not your own law, your own empire? Why not declare the divine right of kings and expand outward, conquering your neighbors as you go?

The Belt had seen a thousand rock wars between independent states, many of which consisted of two rock-happy miners taking potshots at each other. If lunatics wanted to exterminate each other, that was their own affair, but there was a more serious and basic problem. Other people could get drawn in, or get caught in the cross fire. In all likelihood, the Autocrat had saved dozens of lives this day by blotting out the leaders in this pointless fight.

But, obvious as the case had been, the Autocrat had taken pause before rendering his decision. The present Autocrat of Ceres was a most careful person. But so was the previous holder of the post, and the one before that. No other sort of person would ever be appointed.

Not only Ceres, but the entire Belt Community as well depended on the Autocrat’s authority to supply order, discipline, regimentation, at least to Ceres and its surrounding satellites and stations. Anarchy surrounded Ceres on all sides, but even the Belt’s wildest anarchists knew they needed Ceres to be stable, orderly, predictable, to be a place where a trader could buy and sell in safety.

The rules might change elsewhere with every passing day, but at Ceres the Law was always the same. Claims filed in the office of the Autocrat were honored everywhere—for they were backed not only by the Autocrat’s Law and Justice, but his Vengeance.

Nothing but fair dealing was ever done in a Ceres warehouse. None but fair prices were ever paid. No one brought suit frivolously. For the Autocrat himself stood in judgment of all cases.

By the Law, the Autocrat was required, in every case from unlicensed gambling straight up to claim jumping and murder, to find cause why the death penalty should not be exacted against one—or both parties—to the case. If the Autocrat could not—or would not—find such cause, plaintiff and claimant, accuser and defendant died.

The Autocrat’s Law had a long reach. Many defendants were tried in absentia, having chosen to flee rather than face a day in court. But as the saying went, If the Autocrat finds you guilty, he will find you in the flesh. His bounty hunters—and his rewards—found the guilty everywhere. Very few places refused to honor his warrant—and none were places a sane man would flee towards.

Indeed, fear of the Autocrat’s Justice prevented all but the most worthy claimants from coming forth to ask it, and prevented all but the most venal from risking its power. Calls for justice were few and far between when the sword was as sharp as it was double-edged.

From THE RING OF CHARON by Roger MacBride Allen (1990)

(ed note: Lazarus Long tells a story of how he ended up staying years — long enough for his babies to be grown men — on a planet because the government confiscated his ship, and it took that long to make enough money to buy his ship back. Also, that planet is a slaver planet, where slavery and slave trading are legal, something Lazarus detests, badly.)

Once I got my hands on my ship, I had it fumigated and checked it over myself and had it loaded with items I thought I could sell and had food and water taken on for the human cargo it had been refitted for, and sent the captain and crew on a week’s leave, and notified the Protector of Servants — the state slave factor, that is — that we would load as soon as the skipper and purser were back. (the Protector of Servants is also the asshat who confiscated Lazarus' ship in the first place, but who doesn't recognize Lazarus)

“Then I took my family on a holiday inspection of the ship. Somehow the Protector of Servants was suspicious; he insisted on touring the ship with us. So we had to take him along when we took off from there, very suddenly, shortly after my family was aboard. Right out of that system and never went back. But before we put down on a civilized planet, me and my boys — two almost grown by then — removed any sign that she had ever been a slaver, even though it mean jettisoning stuff I could have sold.”

“What about the Protector of Servants?” I asked. “Wasn’t he some trouble to you?”

“Wondered if you would notice that. I spaced the bastard! Alive. He went thataway, eyes popped out and peeing blood. What did you expect me to do? Kiss him?”

From TIME ENOUGH FOR LOVE by Robert Heinlein (1973)

Iris Doors

There are two main styles of "iris" doors: Leaf Iris and Petal Iris.

Leaf Iris Doors

In the role playing game Traveller, airlock doors are often in the form of a iris. This is probably due to the authors of Traveller taking the advice of Robert Heinlein. He noted that science fiction writers can evoke a futuristic vibe by throwing out a weird detail as if it was commonplace, e.g., The door dilated. This phrase has evolved to science fiction fan jargon meaning "cool, but inefficient", but I digress.

Anyway, in the artwork for Traveller game supplements, iris doors are generally depicted as something like a titanic camera diaphragm iris. Sort of like the iris shield on the Stargate, but without the sharp pointy bits.

An iris actually will not work on an airlock, since those always have a small hole in the center where the air will leak out. However, NASA is looking into a rugged iris design that is air-tight.

Besides the lack of a hermetic seal, the individual leafs have to be very thin or they cannot interleave. Which makes for a flimsy door, not a good idea for a hatch which is the only thing standing between you and a horrible suffocating death from the airless vacuum of space.

The Traveller drawings and deck plans also ignore the fact that there has to be space around the edge of the door for the leaves to retract into. The entire door diameter is about 1.55 the size of the door opening. If a standard Traveller iris door had an opening 1.5 meters in diameter, the entire door mechanism would be 2.33 meters in diameter.

Petal Iris Doors

Another design that would work is a four, five, or six petal door; like the one on the roof of the Millennium Falcon which Lando Calrissian exited to rescue Luke Skywalker from the underside of Bespin, in the movie The Empire Strikes Back. Like the NASA design they are actually air-tight.

The petals can be of any arbitrary thickness, allowing an overwhelming safety margin protecting you from death by space asphyxiation. The thickness also allows the use of locking cylindrical bolts like in bank vault doors, providing additional protection from door breaches by air pressure or space pirates.

Unfortunately such doors need even more space around the edge for the petals to retract into. For a six-petal rotating design the door diameter is 1.83 times the size of the door opening.

Docking Ports

A docking port is specialized pressure hatch on a spacecraft that can mate to another docking port on another spacecraft or space station. It creates a pressurized connection so that crew can walk or float from one spacecraft into the other without having to put on space suits. It also makes a strong mechanical connection, because if the connection between the two ships fails when the hatches are open the results will be most tragic.

An airlock is not required as part of a docking port, but it is insanely dangerous to leave it out of the design. Having said that, as far as I am aware there are no real-world spacecraft with airlocks due to the mass and volume of an airlock (with the exception of NASA's space shuttle). Airlocks do add lots of extra mass, which cuts into the rest of the module's mass budget.

Space stations components can be connected in a semi-permanent fashion by mating their docking ports.

A docking mechanism is used when one spacecraft actively maneuvers under its own propulsion to connect to another spacecraft. So Flash Fearless—Space Ace manually pilots his space cruiser to dock with Space Station Beta, while the station watches nervously.

A berthing mechanism is used when space station modules or spacecraft are attached to one another via the manipulations of a robotic arm (instead of their own propulsion) for the final few meters of the rendezvous and attachment process. So the uncrewed resupply rocket approaches the space station and turns off its engines. The station crew extends the robot arm, grabs the rocket, and manhandles the rocket to berth it to the station's berthing port.

Currently there exist no mechanisms that can perform both docking and berthing. NASA is developing the NASA Docking System which will do both, but the design has not been finalized yet.

Note that a robotic arm had better be equipped to deal with high-voltage electrostatic discharge. Or the results of the lightning bolt will be unfortunate.

It is also a very bad idea to have no international standards for docking ports. If the Russian ports cannot dock with Chinese ports, this will drastically reduce the number of rescue options if an emergency happens. There is work being done on a Universal Space Interface Standard, but nothing hs been completed yet.

Early docking ports were even more stupid. They were non-androgynous systems, with a male part and a female part. Sort of like the two ends of an electrical extension cord, one with prongs the other with a receptacle. Which means if the rescue spacecraft and the stricken spacecraft both had male ports, they were out of luck. Or at least the stricken ship is.

If spacecraft commonly have nuclear propulsion systems and/or nuclear power systems, ship design will more or less force ships to dock bow-to-bow (nose-to-nose).

Here's why. Radiations shields by their very nature are massive, and thus cut into the payload capacity. So instead of coating the entire reactor, ships will use "shadow shield" as the smallest possible shield. In the diagrams below, the white area is safe, and the blue area with skull-and-crossed-bones is filled with the deadly radioactive shine from the reactor.

Now say that a lunar shuttle vehicle arrives, and wants to dock. It does not want to wander into the blue radiation zone, or its crew will be irradiated. The crew of the nuclear ferry vehicle does not want the lunar shuttle in the radiation zone either, because the shuttle's metal structure could scatter (reflect) radiation from the ferry's reactor into the ferry's crew.

If you examine the situation, the only safe way seems to be bow-to-bow. Even more so if two nuclear spacecraft want to dock. You may remember this is how the Apollo command and service module docked to the lunar module, even though neither was nuclear powered.

Alistair Young coined a term for this: Booping. A re-use of the word for "tapping your pet affectionately on the nose."

Nuclear spacecraft being forced to dock nose-to-nose does throw a monkey wrench into Traveller's definition of "Port", but that's just too bad.


The current standard for docking adapters in Imperial space, suitable for both docking and berthing, is defined by IOSS 52114, the Imperial Universal Starship Interface (IUSI).

The standard defines androgynous docking adapters in three standard sizes (IUSI-C/crawlspace, IUSI-P/gangway, and IUSI-F/freight container), in both standard (containing a transfer passage and data interface capability) and extended (containing additionally power and utility transfer connections) formats. These adapters are specifically designed to operate with Imperial-standard airlocks (per IOSS 51008) but can be fitted over any of a wide variety of airlock and/or spacetight door standards.

Standard and extended adapters are mutually compatible, with the redundant connections on the extended adapter fitting into sealing caps on the standard adapter. While adapters of differing sizes cannot directly connect, collapsible connection modules for this purpose are available at many starports or compilable from freely-available recipes.

– The Starship Handbook, 155th ed.

From DOCKING by Alistair Young (2015)

prophylock (n.): Used primarily by free traders, a prophylock is a collapsible docking module used when rendezvousing with untrusted vessels for cargo transfer. Similar to a standard docking module, a prophylock is a cylinder with an IUSI-P or IUSI-F androgynous adapter on each end, one to attach to the host starship and one to dock with the foreign starship.

The prophylock, however, has near its outboard end an armored barrier which prohibits the passage of sophonts, equipped with a secure passage (complete with mechanical interlocks preventing both sides from being opened simultaneously, and sampling systems for testing the contents before opening the inner door) through which the transfers may take place. In the event that both vessels are using prophylocks, the secure passage systems are designed to allow transfers from one to the other without direct integration, but also without requiring anyone to occupy the ‘tween-lock volume.

Rather than the direct data systems connection of a standard IUSI adapter, the prophylock connects the foreign data bus to a limited-functionality terminal, permitting communication and negotiation to take place without information risk.

Finally, the outboard end of the prophylock is equipped, for the case in which a lack of trust should turn out to be justified, with an explosive collar to sever the outboard androgynous adapter, thus reliably breaking the connection between vessels, along with solid-fuel jettison rockets to push the host vessel back immediately upon collar detonation, shortening the time to safe burn clearance as much as possible.

Fly safe. Dock safer.

– A Star Traveller’s Dictionary

(Yes, I was thinking of Out of Gas when I wrote this one…)

From SAFETY by Alistair Young (2016)


Far back in time, long before Captain Kirk ordered the Starship Enterprise to enter Warp Factor Five, longer even before Frank Belknap Long invented the term space warp drive, sailing vessels moved by "warping." Also known as "kedging".

You've seen it a million times. A person is inside a rowboat near a mooring dock, holding a rope tied to said dock. All they have to do is the old "heave-ho" routine, pulling on the rope, and the rowboat moves to the dock. The rowboat is "warped" into place.

On the International Space Station, this was adapted for "berthing", replacing the mooring line with the robot arm. In old Robert Heinlein novels, spacecraft were warped into docking ports on a space station the old fashion way, with space-rated mooring lines. Heinlein figured that a spacecraft attempting to dock by using attitude jets was too dangerous. It wastes reaction control system propellant as well, while a mooring line can be re-used.


      Goddard Hotel stuck out from the side of Circum-Terra like a cartwheel from a pile of junk. The hub on which it turned ran through its center and protruded out into space. It was to this hub that a ship would couple its passenger tube when discharging or loading humans. That done, the ship would then be warped over to a cargo port in the non-spinning major body of the station. When the Glory Road made contact, there were three other ships in at Circum-Terra, the Valkyrie in which Don Harvey had passage for Mars, the Nautilus, just in from Venus and in which Sir Isaac expected to return home, and the Spring Tide, the Luna shuttle which alternated with its sister the Neap Tide.

     The two liners and the moon ship were already tied up to the main body of the station; the Glory Road warped in at the hub of the hotel and immediately began to discharge passengers. Don waited his turn and then pulled himself along by handholds, dragging his bags behind him, and soon found himself inside the hotel, but still in weightless free fall in the cylindrical hub of the Goddard.

From BETWEEN PLANETS by Robert Heinlein (1951)

One of them shot something at us and a line came snaking across. Before the knob on the end of it quite reached us there was a bright purple brush discharge from the end of it and every hair on my head stood straight up and my skin prickled.

The knob on the line clunked against the side of the ship and after a bit the little line was followed by a heavier line and then they warped us together, slowly. The Mayflower came up until she filled the port.

From FARMER IN THE SKY by Robert Heinlein (1950)

      "Damn it—I won't if I don't have to." He was fingering his controls again; the blast chopped off his words. When it stopped, the radio maneuvering circuit was calling him.
     "Flying Dutchman, Pilot speaking," Jake shouted back.
     "Terminal Control—Supro (space station Supra-New York) reports you short on fuel."
     "Don't approach. Match speeds outside us. We'll send a transfer ship to refuel you and pick up passengers."
     "I think I can make it."
     "Don't try it. Wait for refueling."
     "Quit telling me how to pilot my ship!" Pemberton switched off the circuit, then stared at the board, whistling morosely. Kelly filled in the words in his mind: "Casey said to the fireman, 'Boy, you better jump, cause two locomotives are agoing to bump!'"
     "You going in the slip anyhow, Jake?"
     "Mmm—no, blast it. I can't take a chance of caving in the side of Terminal, not with passengers aboard. But I'm not going to match speeds fifty miles outside and wait for a piggyback."
     He aimed for a near miss just outside Terminal's orbit, conning by instinct, for Weinstein's figures meant nothing by now. His aim was good; he did not have to waste his hoarded fuel on last minute side corrections to keep from hitting Terminal. When at last he was sure of sliding safely on past if unchecked, he braked once more. Then, as he started to cut off the power, the jets coughed, sputtered, and quit (he ran out of fuel).
     The Flying Dutchman floated in space, five hundred yards outside Terminal, speeds matched.
     Jake switched on the radio. "Terminal—stand by for my line. I'll warp her in."

From SPACE JOCKEY by Robert Heinlein (1947)

The two ships, perfectly matched to eye and almost so by instrument, nevertheless had drifted a couple. of miles apart while the epidemic in the liner raged and died out. The undetectable gravitational attraction between them gave them mutual escape velocity much less than their tiny residual relative motion. Up to now nothing had been done about it since they were still in the easiest of phone range. But now it was necessary to pump reactive mass from one to the other.

Roger Stone threw a weight fastened to a light messenger line as straight and as far as he could heave. By the time it was slowed to a crawl by the drag of the line a crewman from the War God came out after it on his suit jet, In due course the messenger line brought over a heavier line which was fastened to the smaller ship. Hand power alone took a strain on the line. While the mass of Rolling Stone was enormous by human muscle standards, the vector involved was too small to handle by jet and friction was nil. In warping in a space ship the lack of brakes is a consideration more important than power, as numerous dents to ships and space stations testify.

As a result of that gentle tug, two and a half days later the ships were close enough to permit a fuel hose to be connected between them.

From THE ROLLING STONES by Robert Heinlein (1952)

As for the other passenger decks, they found that when they had seen one, they had seen all. Shipboard refreshers interested them for a while, as the curious and clever modifications necessary to make a refresher function properly in space were new to both of them. But four hours is too long to spend inspecting showers and fixtures; after a while they found another fairly quiet spot to loaf and experienced for the first time the outstanding characteristic of all space travel—its monotony.

Much later the ship’s speaker blared, “Prepare for acceleration. Ten minute warning.”

Strapped down again, each in his place, the boys felt short blasts of power at rather long intervals, then a very considerable wait, after which there was the softest and gentlest of bumps. “That’s the drag line,” remarked the sergeant in Matt’s compartment. “They’ll warp us in. It won’t be long now.”

Ten minutes later the speaker announced, “By decks, in succession—discharge passengers.”

     “Then carry himl”
     “How? Piggy-back?”
     “Any way—but do it! The ship is sinking!”
     Tex opened his mouth, closed it again, and dived toward a small locker. Matt yelled. “Tex—get a line!”
     “What do you think I’m doing? Ice-skating?” Tex reappeared with a coil of thin, strong line used in warping the little craft in to her mother ship. “Easy now—lift him as I slip it under his chest.”

From SPACE CADET by Robert Heinlein (1948)

There was frenetic and noisy activity around the base and halfway up the flanks of the interstellar leviathan. Burdened warehouse trucks scooted out of the gaping holds and empty ones scooted in; winches rose and fell. Ground armor clanked into the maws of big freight copters and the loaded copter lifted swiftly to make room for others. Higher up, pale lemon tractor beams reached out to enfold the long slim paratroop ships as they returned from their drops, and warp them home.

From SLEEPING PLANET by William Burkett (1965)

Electrostatic Discharge

In the space environment, it is possible for parts of a spacecraft to charge up (like shuffling your feet on the carpet on a dry winter's day) which can result in an electrostatic discharge (like when you've shuffled, then touch the door knob).

This can cause a spark to jump between spacecraft components or between two docking spacecraft, resulting in damage. In addition if an astronaut on EVA touches the wrong spacecraft or space station component they could get zapped with a severe electrical shock.

Designers will include some sort of discharge probe to safely equalize the electrical potential between the two objects.


Plasma contactors are devices used on spacecraft in order to prevent accumulation of electrostatic charge through the expulsion of plasma (often Xenon).

An electrical contactor is an electrically controlled switch which closes a power or high voltage electrical circuit. A plasma contactor changes the electrically insulating vacuum into a conductor by providing movable electrons and positive gas ions. This conductive path closes a phantom loop circuit to discharge or neutralize the static electricity that can build up on a spacecraft.

Space contains regions with varying concentrations of charged particles such as the plasma sheet, and a static charge builds up as the spacecraft moves between these regions, or as the electrical potential varies within such a region.

Static electricity may also build up on a spacecraft as a result of space radiation, including sunlight, depending on the materials used on the surfaces of the spacecraft.

A plasma contactor is mounted on the Z1 segment of the International Space Station Integrated Truss Structure.

From the Wikipedia entry for PLASMA CONTACTOR

Astronauts Jeff Williams and Thomas Reiter began a scheduled 6-hour spacewalk outside the International Space Station at 1004 EDT (1404 GMT) on Thursday.

One of their main tasks will be to install a device to measure the potentially dangerous static-electricity build-up outside the ISS. The solar arrays, which generate electricity for the orbiting outpost, operate at a higher voltage and have more adjacent solar cells than most spacecraft.

As a result, they collect electrons from the ionised gas in space more quickly than they can be discharged. Eventually, this charge can be released in the form of a spark. That arcing can vaporise some of the metal on the space station, creating a small, dense cloud of ions that expands across its surface. As it does so, it picks up even more negative charges.

NASA has two major concerns about this build-up of charge. First, sporadic arcing could cause long-term damage to the station’s skin-like thermal heat shield, which keeps the station’s temperatures within an acceptable range.

Second, arcing could shock a spacewalking astronaut. NASA says there is a health risk if the ISS charges to more than 40 volts, and a 2002 NASA report says that voltages as low as 60 volts could cause cardiac arrest in a spacewalking astronaut.

“Space vampires”

“If that breakdown occurs on either the metal glove rings on a spacesuit or the neck ring, then you can potentially discharge a fair amount of current from the space station through the astronaut’s space suit or through the astronaut himself,” says Charles Swenson, the principal investigator for the new device at Utah State University’s Space Dynamics Laboratory in North Logan, US.

NASA had sent a previous device, called the Floating Potential Probe, to measure the charge build-up outside the ISS in 2000, but it failed and was discarded during a spacewalk in 2005.

So in July, the space shuttle Discovery delivered a better device, called the Floating Potential Measurement Unit, to the station. The 130 centimetre by 150 cm device, which is shaped like a cross, will help refine computer models of electrical build-up outside the ISS. “When we’re feeling really punchy, we say it protects the astronauts from space vampires,” Swenson told New Scientist.

Escalating problem

Right now, two plasma contactor units bleed excess charge away from the space station, which helps protect astronauts from dangerous sparks. The units make a dense gas of xenon ions that contact the surrounding ionised gas in space, grounding the ISS to its space environment.

But the problem of charge build-up looks set to get worse because the next shuttle mission, scheduled for launch no earlier than 27 August, will deliver more solar arrays to the ISS. These additions could escalate the charging problem, Swenson warns.

The Floating Potential Measurement Unit will be the first item Williams and Reiter will install during their spacewalk. They will also replace an electronics box called a rotary joint motor controller and a computer for a radiator; attach two experiments that expose different materials to the harsh environment of space; test an infrared camera and add other gear to the outside of the station.

These changes will help prepare the station for its continued construction, which will be accomplished through 15 more shuttle flights by 2010. “We’re now ready to execute one of the most challenging sets of flights in the history of the space station programme,” deputy ISS director Kirk Shireman said last week. This spacewalk “is very important to put us into position for these flights”.


Spacecraft Charging

  • Low altitude plasma -Subject of this talk
    • Cold, dense plasma that most often suppresses satellite surface charging - Roughly similar to an air ionizer
    • Can also cause charging by interaction with spacecraft voltage sources
    • Encountered at orbital speeds (8 km/sec)
  • High altitude plasma
    • A problem at Geostationary, polar orbits, and radiation belts - Many charging anomalies including loss of spacecraft
    • Energetic, rarified plasma, able to charge satellites to high voltages directly
    • Encountered at variety of speeds (trapped plasma, solar wind)
  • Particle radiation
    • Trapped radiation and auroral arcs
    • Encountered over range of speeds up to relativistic

Our natural plasma varies with altitude, past and current solar activity, Earth’s variable geomagnetic index, latitude, longitude, and local time. Cold dense plasma in low earth orbit (LEO) gives rise to different problems than hot, rarified plasma at Geostationary orbit (GEO).

International SpaceStation

  • 440+ tons, mostly aluminum
  • 100 meters wide
  • 160 VDC primary power from 8 wings(120VDC secondary) is grounded to hull. “S” bonding or better between all elements
  • Russian System (28VDC) is not grounded
  • Oxide and other insulators cover outer surface
  • Flies in “F” region of ionosphere at 400km

Is ESD a problem to ISS?

  • A hazard occurs whenever one disturbs an equilibrium: i.e., while passing any sort of energy into anything of value to you.
  • ESD: the act of passing electricity through something of value to you == A hazard
  • We have non-bonded conducting objects (especially including crew) in plasma with B fields and E fields. Lots of ways to make an electrostatic discharge == Lots of hazards


  • The risk of electrostatic discharge through EVA crew was elevated in 2001 to be one of the top ISS program risks
    • Only recently downgraded
    • This presentation shows why

The Players:

  • The EVA crewperson (the potential victim…)
  • The Potential Antagonists:
    • The ISS metallic structure
    • The ISS thin oxide and insulating coatings
    • The ISS high voltage solar power arrays
    • The natural plasma (and sun/earth influences on it)
    • The artificial plasma created by ISS PCUs
    • The Earth’s magnetic field (“B”)
    • The EVA suit(s) and tools/tethers

The Hazards: Simplest spacecraft charging hazard causes in low earth orbit:

  • Un-encapsulated high voltage PV power systems, with negative end grounded to spacecraft conducting structure, that can collect electrons from the cold dense ionospheric plasma
  • Large metallic spacecraft structures that generate motional EMF when flying through earth’s magnetic field at orbital speed (V×B⋅L) and also collect electrons for the plasma.

The “Negative” Plasma Hazard:

  • Electrons preferentially attracted to exposed positive conductors, while ions not as mobile.
    • Cold dense plasma problem: not seen at GEO
    • “High side” circuit potential moves down, toward neutral
  • Voltage regulation causes the return side (equipotential with hull) to move below neutral
  • Oxide layers prevent ion neutralization of negative plane.
  • Un-bonded crew then at one potential while ISS Structure moves to another
    • Surface dielectric breakdown can make a highly-localized, large discharge (ISS is 0.01 Farad capacitance)

Negative Plasma Solutions

  • This is not just a crew problem: Discharge canbreak down dielectrics, create EMI, if too high
  • Solved with plasma contactor unit (PCU) to make slow neutral plasma “bath” around ISS.
    • Essentially forces the collected electrons back into the environment in the form of charged particles.

And if the PCU fails?

  • Redundant PCUs
  • Point the active solar arraysurfaces to wake
    • Potentially significant power loss to ISS
  • Monitor the plasma environment
    • If weak enough, can live with worst-case potential
    • Crew susceptible earlier than dielectrics: we live with some dielectric risk and generally only turn on PCUs during EVAs

How do we know what the environment is?

The Floating Potential Measurement Unit (FPMU), using the The Plasma Interaction Model (PIM)

We worry about Positive, too

  • This is a V×B⋅L problem with a long metal boom perpendicular to B field lines, moving at high speed
  • Amplifies in concentrated field near Earth’s poles
    • Local potential at truss tip changes rapidly from the last time the crew made contact. Renewed ground contact makes a capacitive inrush: an “AC” momentary shock hazard
    • Some conducting surfaces on suit can act like a collector, giving electrons a path through crewperson to local ground: A “DC” hazard


  • Ironically, the positive hazard is exacerbated when the plasma contactor removes the negative hazard.
    • Tries to keep the ground plane from suppressing
    • Pushes the end of truss over the top in positive potential hazard


  • ISS operates in electrically conductive plasma environment
  • PCU’s provide ISS ground to plasma
  • As truss flies through the magnetic field a voltage is created along it
    • Combined with PCU’s creates positive potentials on ISS conducting structure
    • High potentials only seen outboard of rotating truss join
    • Plasma acts as a common ground

Positive Risk Mitigation

The ISS Program has enacted all of the following:

  1. Revisit probabilistic risk assessment
    • Result: Crew severe Injury Risk is 1.94E-4 per 5.5 hrs of EVA outboard of rotary joint in un-modified suit, 1.54E-4 with sensor cable modified as listed below, vs. 5.99E-5 for a 6.5 hour EVA when not in positive plasma region of concern. Risk downgraded from catastrophic consequence to severe injury consequence.
  2. Isolation of US Suit external conductive pathways
    • Result: MMWS can be electrically isolated from the EMU and coated to prevent electrical contact
      • Approved at Program review 10/15/ 2009. Now available on-orbit
      • Isolates the most probable plasma charging/contact area
      • Other isolations not practical without major suit contract mods & recertification
  3. Isolation of US Suit internal conductive pathways
    • Result: Safety panel approved a temporary taping of the connections inside the US suit when needed for EVAs that include activity in the positive charge region.
      • Fixes the most probable conducting path to the crewperson & dramatically reduces the AC portion of the risk cause
      • Now available on-orbit. First implemented 2010
      • Other isolations not practical without major suit contract mods & recertification
  4. Adjustment of plasma potential via ISS attitude
    • Result: “sideways” attitude removes the V×B component . The +/-YVV-Z nadir stage attitudes are approved within NASA & Boeing for overlapping ranges from zero to +/-55 deg Beta. (85% of all days)
    • No critical ops in problem area have been identified requiring immediate high-beta EVA: at worst a nuisance of waiting for right conditions, operating in degraded conditions.
  5. Refine study of neuro-physical pathways, impedances, and responses
    • Result: Detailed model shows neuro-physical startle/strong-reflex/pain response (not death) is still possible
      • Corroborated with new International standards for shock exposure
      • Permanent injury is still criedible

(ed note: Humans have found alien carvings on various planets from an unknown race dubbed the "Plumies". The good ship Niccola is sent to try and find a Plumie ship and make peaceful first contact. Which is appropriate since author Murray Leinster invented the term in 1945. They didn't call Leinster the "Dean of Science Fiction" for nothing.

Unfortunately the Niccola's xenophobic weapons officer starts firing unauthorized missiles at the alien ship because of course he does.)

      There were noises inside the Niccola, now. Taine fairly howled an order. There were yells of defiance and excitement. There were more of those inadequate noises as rockets went out—every tube on the starboard side emptied itself in a series of savage grunts—and the Niccola's magnetronic drive roared at full flux density.
     The two ships were less than a mile apart when the Niccola let go her full double broadside of missiles. And then it seemed that the Plumie ship was doomed. There were simply too many rockets to be seized and handled before at least one struck. But there was a new condition. The Plumie ship weaved and dodged its way through them. The new condition was that the rockets were just beginning their run. They had not achieved the terrific velocity they would accumulate in ten miles of no-gravity. They were new-launched; logy; clumsy: not the streaking, flashing death-and-destruction they would become with thirty more seconds of acceleration.
     So the Plumie ship dodged them with a skill and daring past belief. With an incredible agility it got inside them, nearer to the Niccola than they. And then it hurled itself at the human ship as if bent upon a suicidal crash which would destroy both ships together. But Baird, in the radar room, and the skipper in navigation, knew that it would plunge brilliantly past them at the last instant—

     And then they knew that it would not. Because, very suddenly and very abruptly, there was something the matter with the Plumie ship. The life went out of it. It ceased to steer. It began to turn slowly on an axis somewhere amidships. Its nose swung to one side, with no change in the direction of its motion. It floated onward. It was broadside to its line of travel. It continued to turn. It hurtled stern-first toward the Niccola. It did not swerve. It did not dance. It was a lifeless hulk: a derelict in space.
     And it would hit the Niccola amidships with no possible result but destruction for both vessels.

(ed note: they don't realize it yet, but the Niccola's "magnetronic drive" prevents the Plumie's propulsion system from operating if the two ships are too close together. )

     The Niccola's skipper bellowed orders, as if shouting would somehow give them more effect. The magnetronic drive roared. He'd demanded a miracle of it, and he almost got one. The drive strained its thrust-members. It hopelessly overloaded its coils. The Niccola's cobalt-steel hull became more than saturated with the drive-field, and it leaped madly upon an evasion course—
     And it very nearly got away. It was swinging clear when the Plumie ship drifted within fathoms. It was turning aside when the Plumie ship was within yards. And it was almost safe when the golden hull of the Plumie—shadowed now by the Niccola itself—barely scraped a side-keel.

     There was a touch, seemingly deliberate and gentle. But the Niccola shuddered horribly. Then the vision screens flared from such a light as might herald the crack of doom. There was a brightness greater than the brilliance of the sun. And then there was a wrenching, heaving shock. Then there was blackness.

     He clutched crazily at anything. The Niccola's internal gravity was cut off, and his head spun, and he heard collision-doors closing everywhere, but before they closed completely he heard the rasping sound of giant arcs leaping in the engine room. Then there was silence.
     Guided by the emergency light, he scrambled to the bank of communicator-buttons. What had been the floor was now a side wall. He climbed it and thumbed the navigation-room switch.
     "Radar room reporting," he said curtly. "Power out, gravity off, no reports from outside from power failure. No great physical damage."
     He began to hear other voices. There had never been an actual space-collision in the memory of man, but reports came crisply, and the cut-in speakers in the radar room repeated them. Ship-gravity was out all over the ship. Emergency lights were functioning, and those were all the lights there were. There was a slight, unexplained gravity-drift toward what had been the ship's port side. But damage-control reported no loss of pressure in the Niccola's inner hull, though four areas between inner and outer hulls had lost air pressure to space.

     "Mr. Baird," rasped the skipper. "We're blind! Forget everything else and give us eyes to see with!" 
     "We'll try battery power to the vision plates," Baird told Diane. "No full resolution, but better than nothing—"
     They worked together, feverishly. They were dizzy. Something close to nausea came upon them from pure giddiness. What had been the floor was now a wall, and they had to climb to each of the instruments that had been on a wall and now were on the ceiling. But their weight was ounces only. Baird said abruptly: "I know what's the matter! We're spinning! The whole ship's spinning! That's why we're giddy and why we have even a trace of weight. Centrifugal force! Ready for the current?"
     There was a tiny click, and the battery light dimmed. But a vision screen lighted faintly. The stars it showed were moving specks of light. The sun passed deliberately across the screen. Baird switched to other outside scanners. There was power for only one screen at a time. But he saw the starkly impossible. He pressed the navigation-room button.

     "Radar room reporting," he said urgently. "The Plumie ship is fast to us, in contact with our hull! Both ships are spinning together!" He was trying yet other scanners as he spoke, and now he said: "Got it! There are no lines connecting us to the Plumie, but it looks . . . yes! That flash when the ships came together was a flashover of high potential. We're welded to them along twenty feet of our hull!"
     Diane had returned to the utterly necessary routine of the radar room which was the nerve-center of the ship, gathering all information needed for navigation in space. The fact that there had been a collision, that the Niccola's engines were melted to unlovely scrap, that the Plumie ship was now welded irremovably to a side keel, and that a Plumie was signaling to humans while both ships went spinning through space toward an unknown destination—these things did not affect the obligations of the radar room.

     She looked. The view was of the Plumie as welded fast to the Niccola. The welding was itself an extraordinary result of the Plumie's battle-tactics. Tractor and pressor beams were known to men, of course, but human beings used them only under very special conditions. Their operation involved the building-up of terrific static charges. Unless a tractor-beam generator could be grounded to the object it was to pull, it tended to emit lightning-bolts at unpredictable intervals and in entirely random directions. So men didn't use them. Obviously, the Plumies did.
     They'd handled the Niccola's rockets with beams which charged the golden ship to billions of volts. And when the silicon-bronze Plumie ship touched the cobalt-steel Niccola—why—that charge had to be shared. It must have been the most spectacular of all artificial electric flames. Part of the Niccola's hull was vaporized, and undoubtedly part of the Plumie. But the unvaporized surfaces were molten and in contact—and they stuck.
     For a good twenty feet the two ships were united by the most perfect of vacuum-welds. The wholly dissimilar hulls formed a space-catamaran, with a sort of valley between their bulks. Spinning deliberately, as the united ships did, sometimes the sun shone brightly into that valley, and sometimes it was filled with the blackness of the pit.

From THE ALIENS by Murray Leinster (1959)

      I wanted to see the Mayflower from space, but they made us strap down before I could locate it. I got a pretty good view of Supra-New-York though; the Mayflower was in the 24-hour orbit the space station rides in and we were closing almost directly on it when the word came to strap down.
     Captain DeLongPre was quite some pilot. He didn't fiddle around with jockeying his ship into the new groove; he gave one long blast on the jet, the right time, the right amount, and the right direction. As it says in the physics book, "every one-plane correction-of-orbit problem which can be solved at all, can be solved with a single application of acceleration"—provided the pilot is good enough.
     He was good enough. When we went weightless again, I looked over my shoulder out a port and there was the Mayflower, with the Sun gleaming on her, large as life and not very far away. There was the softest sort of a correction bump and the loudspeaker sang out, "Contact completed. You may unstrap."

     I did and went to the port from which we could see the Mayflower. It was easy to see why she could never land; she had no airfoils of any sort, not even fins, and she was the wrong shape—almost spherical except that one side came out to a conical point.
     She looked much too small—then I realized that a little bulge that was sticking out past her edge at one point was actually the bow of the Icarus, unloading on the far side. Then suddenly she was enormous and the little flies on her were men in space suits.

     One of them shot something at us and a line came snaking across. Before the knob on the end of it quite reached us there was a bright purple brush discharge from the end of it and every hair on my head stood straight up and my skin prickled. A couple of the women in the compartment squealed and I heard Miss Andrews soothing them down and telling them that it was just the electrical potential adjusting between the two ships. If she had told them it was a bolt of lightning she would have been just as correct, but I don't suppose that would have soothed them.
     I wasn't scared; any kid who had fooled around with radio or any sort of electronics would have expected it.
     The knob on the line clunked against the side of the ship and after a bit the little line was followed by a heavier line and then they warped us together, slowly. The Mayflower came up until she filled the port.

     After a bit my ears popped (the two docking ports have mated and the airlocks opened) and the loudspeaker said, "All hands—prepare to disembark."

From FARMER IN THE SKY by Robert Heinlein (1950)

      “Tex — Tex!” Atkill called softly. Texas woke from sleep with a start. Atkill was bending over his telescope, watching something with an expression of unholy joy on his face. “Come here, Tex, and look — we have visitors at last. I knew they’d come eventually. Three ships!”
     Three thin pencil-ships floated in space, tiny things glinting in the harsh light of the great sun. Atkill watched them carefully, calculating their course accurately. They should reach him in a short three hours at their present velocity. He set to work rapidly.
     In an hour he had set the controls in the power-room for starting the Flame, and had set up the little piece of apparatus he had made in the garbage-lock, with a long, thin tube of aluminum held in place by strings of insulators. The rod projected some twenty feet from fee side of the ship. Along with the little apparatus he had made, there were three powerful magnets he had been making, and a little spark-gap of chrome-nickel blocks between the long aluminum tube and a heavy lead that grounded to the ship. Atkill had plans.

     “Tex, sweet lad, we are about to be saved. The mere coming of our friends gives us once more, power, light and life! I can start the Flame!”
     “Uhm — that’s right good news. How come? Yuh couldn’t before. They may decide to wipe us out instead of helping.”
     Atkill laughed cheerfully. “They’ve got to help. The sun’s been doing the necessary work for the last three months! All they have to do is come near — and they will. Remember, Tex, the late unpleasantness we watched from space here that they were having on that planet? War. They want weapons — science. We’ve got it. We’re a strange ship, a ship of neither their world or the enemy world. We are, apparently, a dead ship. They see in us a possibility of help. They will investigate.”
     “Uhm — but how come they’ll have to help?”
     “For three months that sun has been deluging our ship with ejected electrons. We’ve built up a tremendous charge. We haven’t lost a bit of it. Those ships, just come from a planet, have a much smaller charge. We’ll discharge to them, my lad, with a smash of about eighteen mega-volts — an extra two million. Really I need only sixteen or so. I said eighteen for safety — and I’ll have it. My starting apparatus for the Flame is weak on magnetism and gravitational fields, but the extra electric will make it up, I suspect.”

     The ships were slowing now, approaching cautiously. They were less than fifty miles away now. Atkill could see them clearly with the naked eye now as dots of light. He went back to the power-room and started the gyroscope device. It had been improved in the months that had passed, and was now a quite efficient machine for swinging the ship as he wished.
     Anxiously he watched the ships approach. Finally a lone, small ship came out of one of the three greater spaceships, and approached slowly. It circled the earth ship at a distance of a few hundred yards, then finally came toward them. A long metal arm reached out from the ship, and the machine came gently directly toward the out-jutting terminal Atkill had arranged.
     “Tex — get set as I showed you at the controls — one, two and five switches closed, four and six open, three at the midpoint. When the Flame starts, snap the dial seven to 458-23. Got it?”
     Atkill was working at the single, tiny lock. He closed a switch and the magnets ground slightly in their supports, pressing away from each other. Swiftly he made several further adjustments, and watched the ship. Absolute space — an almost perfect insulator. Would the discharge-shock be sudden enough to give the result he so desperately needed? Or would it be a slow leaking that would be perfectly useless?

     The discharge rods were less than a foot apart. Slowly the pilot of the stranger ship maneuvered them skillfully together. There was a terrific strain out there now — enough to have started his Flame if he had been in position to use it.
     They came within an inch — then suddenly they touched. A blinding, roaring smash of electric energy crashed across the gap between Atkill's discharge points. Less than two inches of separation, creating an electric field of terrific intensity. Atkill could feel the charge leak suddenly from his body — and cried out in exultant triumph as the clear white of the Release Flame suddenly sprang into being on his little block of iron. A tiny flame no larger than a flashlight bulb, a dazzling white point of light that pulsed for an instant, steadied, and glowed as it would glow for hundreds of millennia if left undisturbed.

From THE SPACE BEYOND by John W. Campbell jr. (1976)

(ed note: Our heroes on the Venus Equilateral space station are trying to invent an electron particle beam weapon. This hobby project takes on some urgency when a fellow named Murdock becomes a pirate and terrorizes the entire solar system. Engineers Channing and Walt brainstorm how to make the weapon work.)

      "Another thing, whilst I hold it in my mind," said Channing thoughtfully. "You go flinging electrons off the station in basketful after basketful, and the next bird that drops a ship on the landing stage is going to spot-weld himself right to the south end of Venus Equilateral. It wouldn't be long before the station would find itself being pulled into Sol because of the electrostatic stress— if we didn't run out of electrons first!"
     "I hardly think that we'd run out— but we might have a tough time flinging them away after a bit. Could it be that we should blow out a fistful of protons at the same time?"
     "Might make up a concentric beam and wave positive ions at the target," said Channing.
     "Don," said Walt in a worried voice, "how are we going to replace the charge on the station? Like the bird who was tossing baseballs out of the train— he quit when he ran out of them. Our gun will quit cold when we run out of electrons— or when the positive charge gets so high that the betatron can't overcome the electrostatic attraction."
     "Venus Equilateral is a free grid," smiled Channing. "As soon as we shoot off electrons, Old Sol becomes a hot cathode and our station collects 'em until the charge is equalized again."
     "And what is happening to the bird who is holding on to something when we make off with a million volts? Does he scrape himself off the opposite wall in a week or so— after he comes to— or can we use him for freezing ice cubes? ("frozen" is slang for "fried to a crisp and stuck to the wall") Seems to me that it might be a little bit fatal."
     "Didn't think of that," Channing said. "There's one thing: their personal charge doesn't add up to a large quantity of electricity. If we insulate 'em and put 'em in their spacesuits, they'll be all right as long as they don't try to grab anything. They'll be on the up and down for a bit, but the resistance of the spacesuit is high enough to keep 'em from draining out all their electrons at once. I recall the experiments with early Van de Graaff generators at a few million volts— the operator used to sit in the charged sphere because it was one place where he couldn't be hit by man-made lightning. It'll be rough, but it won't kill us. Spacesuits, and have 'em sit in plastic chairs, the feet of which are insulated from the floor by china dinner plates. This plastic wall covering that we have in the apartments is a blessing. If, it were all bare steel, every room would be a miniature Hell. Issue general instructions to that effect. We've been having emergency drills for a long time; now's the time to use the grand collection of elastomer spacesuits. Tell 'em we give 'em an hour to get ready."

(ed note: Murdoch's two other ships are destroyed by the electron gun, and his ship is crippled by a glancing blow)

     Murdoch's radio was completely dead. His ship was yawing from side to side as the static charges raced through the driver tubes. The pilot gained control after a fashion, and decided that he had taken enough. He circled the station warily and began to make a shaky landing at the south end.
     Channing saw him coming, and with a glint in his eye, he pressed the lever for the fourth and last time (firing the electron gun at nothing, but energizing Venus Equilateral's structure with a powerful positive charge).
     Murdoch's ship touched the landing stage just after the charge had been driven out into space. The heavy negative charge on the Hippocrates met the heavy positive charge on Venus Equilateral. The ship touched and from that contact, there arose a cloud of incandescent gas. The entire charge left the ship at once, and through that single contact.
     When the cloud dissipated, the contact was a crude but efficient welded joint that was gleaming white-hot.
     Channing said to Walt: "That's going to be messy."
     Inside the Hippocrates, men were frozen to their handholds (meaning the dead carbonized bodies are stuck to the handholds). It was messy, and cleaning up the Hippocrates was a job not relished by those who did it.

From RECOIL by George O. Smith (1943)

Airlock Tunnels

Sometimes they are docking adaptors, with a different type of connector on each end.

Docking in the Eldraeverse

While IOSS 52114-compliant docking adapters are commonly used in most polities throughout the Worlds, in selected regions and on the fringes non-compliant docking adapters are found in use. For this situation, IOSS 52114 also defines the IUSI-NC universal adapter, consisting of an inflatable tunnel with an IUSI-compatible adapter at one end, and an open end coated with a nanotechnological bonding compound capable of adhering to all commonly used hull materials, releasing upon mesh command without altering the attachment surface. The IUSI-NC can be installed during an extravehicular activity when pressurized transfers are required.

– The Starship Handbook, 155th ed.

From Docking by Alistair Young (2015)

     "One more thing, Captain."
     Rod knew something tricky was coming. Horvath had Dr. Hardy ask for all the things Rod might refuse.
     "The Moties want to build an air-lock bridge between the cutter and the embassy ship," Hardy finished.

     "Doctor, I don't like the idea of joining the two ships."
     "But, Captain, we need something like this. People and Moties are constantly passing back and forth, and they have to use the taxi every time. Besides, the Moties have already started work—"
     "May I point out that if they join those two ships, you and everyone aboard will thenceforth be hostage to the Moties' good will?"
     Horvath was ruffled. "I'm sure the aliens can be trusted, Captain. We're making very good progress with them."
     "Besides," Chaplain Hardy added equably, "we're hostage now. There was never a way to avoid the situation. MacArthur and Lenin are our protection, if we need protection. If two battleships don't scare them—well, we knew the situation when we boarded the cutter."

     The lock was begun as soon as Rod gave permission. A tube of thin metal, flexibly jointed, jutting from the hull of the Motie ship, it snaked toward them like a living creature.

     The landing boat was a blunt arrowhead coated with ablative material. The pilot's cabin was a large wrap-around transparency, and there were no other windows. When Sally and her Motie arrived at the entryway; she was startled to see Horace Bury just ahead of her.
     "You're going down to the Mote, Your Excellency?" Sally asked.
     "Yes, my lady." Bury seemed as surprised as Sally. He entered the connecting tube to find that the Moties had employed an old Navy trick—the tube was pressurized with a lower pressure at the receiving end, so that the passengers were wafted along.

From The Mote In God's Eye by Larry Niven and Jerry Pournelle (1975)

There weren't the questions about cargo or permits. The invaders had come in like they owned the place, and Captain Darren had rolled over like a dog. Everyone else—Mike, Dave, Wan Li—they'd all just thrown up their hands and gone along quietly. The pirates or slavers or whatever they were had dragged them off the little transport ship that had been her home, and down a docking tube without even minimal environment suits. The tube's thin layer of Mylar was the only thing between them and hard nothing: hope it didn't rip; goodbye lungs if it did.

From Leviathan Wakes by James Corey (2011)


Rockets don't got windows. At least nothing like the huge panorama picture windows you see on the Seaview or the bridge of an Imperial Star Destroyer.

When NASA was developing the windows for the Apollo spacecraft, there were some failures. After that, they decreeded the following: A spacecraft window is structurally defined as any piece of glass that is thermally or mechanically stressed and will endanger the crew or mission success if it breaks.

Huge windows on a spacecraft are not a good idea for many of the same reasons as they are not used on a submarine.

  • Window frames create a structural weakness in the hull.
  • If they break they let all the air out of the compartment, killing everybody. At the least you need airtight shutters.
  • They let in deadly space radiation.
  • If the spacecraft performs aerobraking or aerocapture the windows have to be protected from the blowtorch heat. This was a headache when NASA designed the Apollo Command Module. Windows melting or shattering could ruin your whole day.
  • With a few exceptions, there isn't anything to see. Outside of the exceptions the only things to see are
    • Endless black space dusted with stars
    • The eye-melting fury of the Sun
    • The planet you are orbiting, for the small fraction of the total space mission time that you are close enough to see the planet.

"But…but…but…!" you protest, "what about watching the dazzling spectacle of a space battle?" RocketCat does a face-palm at your naïveté. Star Trek, Star Wars, Battlestar Galactica, et al to the contrary, space battles will NOT be fought at spitting distance. Directed energy weapons will force ranges such that the enemy ships will only be visible through a telescope.

Watching a space battle through a port hole, you will either:

  • See nothing because the enemy ships are too far away to see without a telescope
  • See nothing because a reflected laser beam or nuclear explosion has permanently robbed you of your eyesight

Instead of windows, spacecraft will have lots of external sensors and video monitors inside for the crew to watch. Much like watching a football game: you will get a far superior view of the game if you stay home and watch it on TV.

As points of reference, the side windows on the Apollo Command Module (CM) are 33 centimeters square. The CM docking windows were 20×33 cm. The Apollo Lunar Module landing windows were 64×71 cm triangles, with the top edge further from the hull so the pilot can look down at the landing legs. The windows on the Space Shuttle airlock hatches were 10 cm in diameter.

The Cupola on the International Space Station has the largest windows used in space to date, the top window is an 80 cm disc. Yes, it has very thick shutters (made of Kevlar and Nextel). It is used to conduct experiments, dockings and observations of Terra. It also helps with the use of the amazing Canadarm2 remote manipulator.


Places where windows might be worth the drawbacks are"

Window Construction

This is from Apollo experience report: Spacecraft structural windows

Trusting the astronaut's lives to something made out of glass is nerve wracking, since glass is notoriously brittle. The strength of glass is measured by the modulus of rupture (MOR). A safety factor of 3.0 was used.

The Apollo command module has five double-pane windows, as shown in the diagram.

All five windows are double-panes of aluminosilicate glass. The space between the panes is evacuated and fill to 7.0 psia with dry inert nitrogen gas.

Every attempt is made to prevent stress on the windows. The mounting process was designed to preclude installation stress. The frames were design to avoid loads on the window. This was done by injecting a silicone elastomer around the edge of each pane and curing it in place. This potted the windows in their frame and provided an air-tight seal.

The only load was the pressure of the nitrogen, since there wasn't anything that could be done about that.

The aluminosilicate glass thermally tempered to 25,000 psi MOR for hatch and side windows and 23,200 psi MOR for the rendezvous windows. A safety factor of 3.0 was used. Each pane of a double-pane has the same thickness. Hatch 0.23 inch, side 0.25 inch, and rendezvous 0.20 inch. All panes are coated on both sides with a high-efficiency antirefection (HEA) coating.

The double-pane windows are covered with a 0.7 inch thick fused amorphous silica pane as a heat shield. When the command module does its flaming re-entry, the windows have to be protected or the results will be most unfortunate. They will be exposed to thermal loading for about 15 minutes.

The heat shield panes are insulated around the edge by a 0.02-inch-thick fiberglas layerr using a silicone elastomer bonding agent. The 0.080-inch-thick steel frame and retainer were designed so that the flat glazing would fit on the conical hull. It had a 0.05 inch gap on all edges between the insulation and frame so the shell could contract when it hit the cold Pacific ocean without shattering the glass. The pane had an outboard coating of magnesium fluoride, and an inboard blue-red coating.

Docking Window

Docking or rendezvous windows are generally aimed parallel to the axis of the docking port. Since the NASA Apollo CS module and the Russian Soyuz have the docking port on their nose, their docking windows are aimed straight ahead.

There may be a "docking control station" with special windows, either for guiding small craft to docking ports or for bringing the ship itself up to dock to another ship or a station. You could use video screens, but a viewport is simpler, and less likely to go to "snow" at the worst possible moment. The docking control station might be out on a boom or otherwise elevated to give a better field of view.

The Russian Soyuz does not use either a video screen nor a window. It uses a periscope which rear-projects onto a frosted glass screen. This is an admirable low-tech solution. There is no electronic screen which could malfunction, but neither is there a large vulnerable glass window letting in radiation.

Virtual Windows

With the advent of virtual reality there is a semi-plausible solution to the spacecraft window problem: use virtual windows instead. Mount some huge computer monitors on the walls and have them display what would be seen through an actual physical window in that location.

Or even more cyberspacelike: wear some virtual reality goggles, and have the computer paint a fake window wherever you want in your field of vision. With this you can change the location of the windows at your whim. All the immediacy and instinctual utility of a physical window, but with none of the vulnerability.

Except of course if the virtual reality computer is stopped or destroyed, suddenly you are trapped in a metal box you cannot see out of. You might want a couple of emergency physical windows you can unshutter for just such an situation.


Lia was pleased to notice on the ride to the command deck that the ship’s containment field held at a steady one gee. The bridge itself was about twenty-five meters across and held command-nexus stations for the various specialists, as well as a central table—round, of course—where the awakened were gathering, sipping coffee and making the usual soft jokes about cryogenic deep-sleep dreams. All around the great hemisphere of the command deck, broad windows opened onto space: Dem Lia stood a minute looking at the strange arrangement of the stars, the view back along the seemingly infinite length of the Helix itself where heavy filters dimmed the brilliance of the fusion-flame tail that now reached back eight kilometers toward their destination—and the binary system itself, one small white star and one red giant, both clearly visible. The windows were not actual windows, of course; their holo pickups could be changed and zoomed or opaqued in an instant, but for now the illusion was perfect.

From ORPHANS OF THE HELIX by Dan Simmons (1999)

(ed note: in the novel everybody wears virtual reality goggles called zeespecs. They can paint items over your field of vision, like fake windows. They can also paint the controls on your spacecraft control panel, so you can have your station on any convenient flat surface.)

      No windows in Louis Pasteur—have I mentioned that? But there were camera dots embedded in the hull that could assemble a visual image and project it through a zeespec. Somehow, I was coherent enough to manage this task, and so was watching as the exit portal irised open in the ceiling above us. Our ladderdown reactors hissed to life. Propulsion came online.

     The worst of it was that my allocation duties were quickly done with, and everyone else seemed to have a job to do. So it was that I pulled up an external window and a navigation graphic, had time to correlate the two, and made the announcement: “Our orbit takes us right past the starship. I mean, right past it.”
     “Departure conic,” Darren Wallich said distractedly, his eyes on instruments I couldn’t see. “‘Orbit’ usually means you’re not still under thrust.”
     “Not by my dictionary,” I fired back, unaccountably annoyed at the contradiction.
     “Possibly. But learn the language while you’re here, right?”
     “Anyway,” I continued, “our departure conic looks like it’ll bring us very close, like within a couple of kilometers. It should be coming over the horizon right about now.”
     “Coming over the limb,” Wallich corrected. And chuckled. Oh, this was going to be a fun voyage.

     But now everyone started stabbing at the air, pulling up exterior-view windows to see what I was talking about. Here is what these windows showed: a circular opening in space, a hole not only through the ship’s hull but through chairs, instrument panels, and people—a hole looking out at focus infinity, no matter what was in the way. Not so hard on the eye, really, but it takes getting used to, especially the way it tracks head but not eye movements. Turn to look at someone, and suddenly there are stars showing through where a face or a heart should be.

     “You might want to look outside, Baucum said. “Three o’clock high, twenty degrees. We have a visitor.”
     Oh. Reluctantly, I turned and opened a round exterior window, anchoring it to the bulkhead beside me. Where Baucum was pointing, there hung a…smudge? Cloud? No, of course, it was a transient megastructure, a diffuse bloom of loosely interacting mycora, massing maybe twenty or a hundred kilograms smeared across thousands of cubic kilometers of space.

From BLOOM by Wil McCarthy (1998)

Interior Arrangement

In all the crew's "blastoff stations", they will have acceleration couches. As most space fans know, the human body can tolerate more gravities of acceleration when lying horizontal than when sitting upright in a chair. Crew members who will have to operate controls while under multi-gravity acceleration will have fancy chairs which hold their bodies horizontal, vital controls at their fingertips, and critical dials, telltales, repeaters, and read-outs mounted above them in easy view. The rest of the crew will be lucky to get glorified cots or hammocks (They will probably be stuck with using whatever it is that they sleep in. Tough if they are using a "hot bunk" system.). In the movie DESTINATION: MOON, the pilot had the important controls located on a sort of lap-board for easy access. For real high gravity acceleration, the crew will have to use couches that are high-tech waterbeds.

And remember that Rockets Are Not Hotels. They are going to be cramped. Though keep in mind that in free-fall the entire three-dimensional living area can be used so it won't be as cramped as the floor space might lead you to believe.

The corridors will have cables, pipes and ducting either exposed or behind easily removable panels. This is to facilitate repairs. The panel brackets can double as hand-holds. The main function of panels is to protect the cables from clumsy crew members flying in free-fall. Of course all the cables and pipes will be color-coded. If the designers are smart they will double-key them as well.

The corridors will become instantly dark if the power goes off (since port-holes let all the radiation in the ship won't have any). Navy veteran Jennifer Linsky says that US Naval ships have so-called "battle lanterns." They are located in all corridors and most compartments. Each contains a rechargable 12 vold battery hooked to the ship's power grid, constantly charging. If the power grid goes dead, the lamps switch to battery power and turn on. They have red lenses to preserve the night vision of the damage control teams.

This also means that all those color-coded pipes and cables will also have stenciled labels or other double-keying, since red lighting renders color coding worthless.

In James Blish's SPOCK MUST DIE, shuttlecraft have "glow-pups", which are tubes filled with (imaginary) "ethon" gas excited by a built-in radioactive source. They will glow with no power for millions of years.

As with so many other things, high tech items predicted by Star Trek have come to pass. The modern version is called a "Gaseous Tritium Light Source", and is used in submarines. A tube of borosilicate glass is internally coated with a phosphor. It is filled with a trace amount of radioactive Tritium gas and sealed. It will glow for about 10 to 20 years, and is not particularly radioactive. Even if the tube breaks, the gas is too rarefied to be a health hazard. They sell these things in England as glow-in-the-dark keychain fobs.

Glow-pups will be in strategic places for lighting, and will also be placed to indicate hatches and sharp corners of equipment. Anywhere to help getting around in the dark.

"In there. Find your locker and wait by it." Libby hurried to obey. Inside he found a jumble of baggage and men in a wide low-ceilinged compartment. A line of glow-tubes ran around the junction of bulkhead and ceiling and trisected the overhead: the 50ft roar of blowers made a background to the voices of his shipmates.

From "Misfit" by Robert Heinlein (1939)

Rick Robinson notes that the corridors will probably not be cramped like those on a submarine. The main reason subs are so claustrophobic is because the entire sub has to have, on the average, exactly the density of water. Spacecraft don't have to. (spacecraft designers do have to worry about how much air it takes to pressurize the lifesystem, and the mass of the bulkheads enclosing the interior space.)

While not cramped, the interior will probably be similar to the inside of a conventional Naval vessel. That is, it will be full of sharp corners and hard girders to bark your shins or to give you a concussion. The rule in the U.S. Navy is "one hand for the ship, one hand for you." In other words, always keep a hand free, and when moving through the corridors, you put you hand on the thing sticking out into the passageway as you reach it.

The duty stations of the crew members will probably be cramped. In NASA speak the "work envelope" will be small.

Ladderways may be offset between decks. You don't want to have a five story fall awaiting somebody who slips off the ladder. Especially if the spacecraft is pulling three gees. If they are offset, the farthest one can fall is one deck's worth. However, Rick Robinson has an interesting alternate solution. He notes that moving equipment and supplies through a ship is always a problem, and will be exacerbated by offsetting the ladderways. His solution is to have the ladderway openings in a straight line, but while the spacecraft is under thrust, the ladders will be inclined to become stairs. The stairs will prevent fall-through. When the spacecraft enters free-fall, the stairs are rotated to a vertical position, becoming a ladder again and allowing the ladderway to become a fast route for moving equipment. The stair/ladders can be secured in either position by cotter pins. Don't forget to attach the pins to the ladders with wires to prevent them from floating away while the ladders are rotated. And obviously places where the ladderway penetrates a pressure bulkhead will have large hatches.

has some important observations:

Another thing you might want to think about, based on my naval engineering days: how big are the biggest parts in the engineering spaces? That is, what's the size of the biggest thing you might have to move in and out of the craft for repairs or replacement? The radiators are already on the outside. Are there reactor vessels, fusion containment cells, or some other nifty big bits that cannot be broken down into smaller parts? How about tanks (for algae, fuel, water, sewage, recycling, air)? You're going to need a way to get that stuff on and off, and a way to handle the large mass safely.

Barry P. Messina

In the movie Forbidden Planet, there is a small crane mounted over a deck hatch to facilitate moving equipment between decks. It is shown in the scene where the invisible monster enters through the hatch into the bunkroom full of sleeping enlisted men. It is the long metal arm that the invisible monster bumps out of the way.

Submarines In Space

Several times in science fiction, a reactionless drive or antigravity/paragravity drive is invented. And then the scientist gets the bright idea that if they mount the drive inside a submarine they will have Instant Spaceship.

In reality this would not work very well. A submarine is build to resist stronger pressure outside pressing in, not stronger pressure inside pressing out. And if the submarine is nuclear powered, you had better attach some kind of heat radiator. Nuclear submarines get rid of heat by sucking in cold ocean water and spewing out hot heat sink water. This won't work in space, there isn't any ocean. Not to mention the fact that a sub nuclear reactor's coolant system requires gravity to work.

This trope seems to have been invented by John W. Campbell jr., in an article he wrote about the Dean Drive in 1960. Other novels that use this theme include The Daleth Effect by Harry Harrison (1969), Gilpin's Space by Reginald Bretnor (1983), Salvage and Destroy by Edward Llewellyn (1984), and Vorpal Blade by John Ringo (2007). There is a mention of an "inertial drive" (another name for a Dean Drive) in Randall Garrett's Anything You Can Do but there it is used as a way to make recon drones float in the air.

This also seems to have influenced a certain Matt Jeffries, designer of the original Starship Enterprise, Klingon Battle Cruiser, and related works. A couple of his designs feature a "sail" or "conning tower" which are common to submarines. Perhaps he read Campbell's Dean Drive article and was inspired. If the first few starships were actually refitted submarines, maybe purpose-built starships would retain the conning tower for tradition.

The first Matt Jeffries design with a conning tower was the Botany Bay aka DY-100 from the Star Trek episode "Space Seed." It was later re-used as Automated Ore Freighter Woden in "The Ultimate Computer".

Around 1967, the AMT plastic model company wanted to cash in on Star Trek mania. They wanted to make a line of plastic model starship kits, but of their own design. So they hired Matt Jeffries to make a starship, the Galactic Cruiser Leif Ericson. Again it had the signature submarine conning tower. Unfortunately the kit was a financial disappointment, and further starships in the line were cancelled. The kit was re-issued in 2011 due to demand from those who had the original kit when they were young.

In the early 1970's, when Larry Niven and Jerry Pournelle were writing the classic The Mote in God's Eye, they used the Leif model as the inspiration for the INSS MacArthur.

Around 1975 Matt Jefferies was hired by George Pal to work on a TV series based on THE WAR OF THE WORLDS. As you can see the Hyperspace Carrier Pegasus is an outgrowth of the Leif Ericson. Note that instead of two side engines, the Pegasus has four, two on each side. For the TV series, Jefferies actually had the Pegasus upside down in relation to the Leif Ericson, in order to make the connection less obvious. The TV series was never picked up, alas. But this is a facinating glimpse of what might have been.

Occasionally in later science fiction illustrations one again finds the submarine conning tower.

Analog Dean Drive Article

A modern nuclear-powered submarine needs only relatively minor adaptations to make an ideal spaceship; it has everything it needs, save for the space drive.

The Dean drive requires a rotary shaft drive; our nuclear submarines turn nuclear energy into heat, produce steam, drive a turbine, and generate electric power. Electric power is perfect for running the Dean drive.

The modern submarines are — we have learned from past sad experience — equipped with lifting eyes so that, in event of accidental collision, quick salvage is possible. Pontoons can be towed in place, sunk beside the ship, and hitched to the built-in lifting eyes, and the ship refloated. The eyes are, of course, designed into the ship so that the structure can be lifted by those eyes without structural damage to the hull.

Dean drive units could be attached directly to the existent eyes. (ed note: you can see this in the image. The two bands around the submarine's waist hold the Dean Drive units. This also means the ship's direction of motion is in the direction the conning tower is pointed, which would make sense.)

The pressure hull of modern submarines is designed to resist at least 600 feet of water pressure; its actual thickness is a piece of classified data, of course, but we can guesstimate it must be at least 4 inches thick. After the second Bikini bomb test, the old submarine Skate was still in pretty fair condition; the light-metal streamlining hull looked like the remains of an airliner crash, but the pressure hull was perfectly intact. Stout stuff, a sub’s pressure hull.

And very fine stuff indeed as protection against the average meteor; the light streamlining hull would stop the micrometeors, of course.

Not even 4 feet of steel would stop primary cosmic rays, of course… but those inches of armor steel would have considerable damping effect on the Van Allen radiation belt effects.

The nuclear subs have already been tested with full crews for 30 continuous days out of contact with Earth’s atmosphere; their air-recycling equipment is already in place, and functions perfectly. What difference if the ‘out of contact’ situation involves submersion in water, instead of out in space?

The modern nuclear submarine is, in fact, a fully competent space-vehicle, lacking only the Dean drive.

With the Dean drive, the ship, if it can lift off the Earth at all, can generate a one-G vertical acceleration. Since that acceleration is being generated by engines capable of continuous operation for months — if not years — at a time, the acceleration can simply be maintained for the entire run; there would be no period of free-fall for the ship or crew. Therefore the present ship structure, equipment, and auxiliary designs would be entirely satisfactory. Also, a sub has various plumbing devices with built-in locks so the equipment can be used under conditions where the external pressure is widely different from the internal.

In flight, the ship would simply lift out of the sea, rise vertically, maintaining a constant 1000 cm/sec drive. Halfway to Mars, it would loop its course, and decelerate the rest of the way at the same rate. To the passengers, and to the equipment on board, there would be no free-flight problems.

There is one factor that has to be taken in to account, however; the exhaust steam from the turbine has to be recondensed and returned to the boiler. In the sea, seawater is used to cool the condenser; in space, the cold vacuum would do the job.

The tough part would be the first 100 miles up from the Earth; ice could be used.

As a crash program, this could have been done — if work started when Dean first applied for his patent — in 15 months. The application went in in July 1956; 15 months later would have been October 1957.

Under the acceleration conditions described above, a ship can make the trip from Earth to mars, when Mars is closest, in less than three days. And even when Mars is at its farthest possible point, on the far side of the Sun, the trip would only take 5 days.

It would have been nice if, in response to Sputnik I, the US had been able to release full photographic evidence of Mars Base I.

from "The Space Drive Problem" by John W. Campbell, Jr in Analog Magazine June 1960

The Daleth Effect

Analog December 1969. Illustration for Harry Harrison's "In Our Hands, The Stars", which was later expanded into the novel The Daleth Effect.

Harry Harrison wrote an amusing but cautionary tale called The Daleth Effect. In the novel, an Israeli scientist discover the principle for a reactionless drive. Naturally the first real test is the Submarine Spacecraft trick.

He returns to his native Denmark to develop it. He wishes to develop the idea without it falling into the hands of the military, since it also has potential as a weapon. Good luck with that.

Denmark keeps it a secret until they feel obligated to use the technology in public to rescue some cosmonauts stranded on Luna. Any fool could have told the Danes that no good deed goes unpunished.

Naturally the US, Soviet Union, and other powerful nations will stop at nothing to lay their hands on this technology. The race is on! They try all sorts of tactics to pressure the Danes but to no avail. They look on with helpless rage as the Danes establish a Lunar base and make a large ship for a visit to Mars.

Like absolute idiots the Danes invite foreign dignitaries to ride on the Mars trip. Naturally pretty much 100% of the dignitaries turn out to be secret agents. Hilarity ensues. And then the novel has a most ironic and satisfying ending.

Gilpin's Space

Eccentric but brilliant scientist Saul Gilpin invents a magic hyperspace faster-than-light propulsion system / antigravity surface-to-orbit gadget which can be cobbled together from parts available from your local hardware store. He mounts it on a submarine and has instant starship. Then he and the submarine depart for parts unknown.

This makes the totalitarian government very unhappy. They want to use this technology, they do not want citizens getting their hands on it. Makes it far to easy to escape the totalitarian state. Then they find out that Gilpin has mailed blueprints of the gadget to quite a few people. Hilarity ensues.

Salvage and Destroy

An ancient alien interstellar empire is worried about the large US and Soviet submarine fleets. Once Earth discovered anti-grav and FTL drives, the warlike unstable Earthlings would have a ready-made fleet of combat starships. This could turn into a nasty problem.

(ed note: aliens on Earth are covertly observing a US submarine)

“She’s an attack sub.” Joshua altered course as the black hull came sliding toward us out of the dawn mists. He gave one blast on the horn. “Mark, can you read the number on her sail?”

“SSN-767.” Mark put down his binoculars and took Jane’s Fighting Ships from the book rack in the wheelhouse. “USS Muskelunge. Four thousand six hundred tons dived. One hundred and ten meters overall. Six torpedo tubes plus subsurface attack missiles. Pressurized water-cooled reactors feeding two steam turbines. Speed dived-fifty knots plus. Complement—one hundred and ten.” He closed the book. “She’s among the most powerful warships in the Cluster—now the Ult fleets are laid up.”

“Fit that sub with inertial drive and she’d be ready for space!” said Joshua. “And there’s over four hundred like her at sea.”

An instant space fleet!” remarked someone on the foredeck.

“They couldn’t make a vortex passage. They couldn’t get out of this starfield. They wouldn’t have anybody to fight.”

“They’d find somebody. Or settle for fighting each other!”

Add inertial drive and Earth would have a space fleet! However unlikely, the idea was chilling. The men and women with me would gladly crew a human fleet, apparently blind to the outcome of such madness, as the Terrans were blind to the imminent effects of their own folly.

From nuclear submarine to inertial spaceship—an immense leap. Yet that hunter-killer exemplified a leap of the like magnitude. From sail to atomics in a hundred years! If the Terrans survived the next hundred would they leap into the dark? Into the Cluster?

I shook myself. Not even their present exponential advance would take them to vortex transits within a century. But within centuries? Up to the stars or down to hell?

from Salvage and Destroy by by Edward Llewellyn (1984)

Vorpal Blade

Shortly after they'd stopped the invasion, the Adar had given him another strange device. On first tests, it had appeared to be the world's most powerful nuclear hand grenade. Any electrical power sent to it, so much as a spark of static, and, well, there was a boom. A really big boom. "There should have been an earth shattering Ka-Boom!" boom. Putting three-phase on it had, in fact, erased a solar system.

The Adar didn't know what it was supposed to do but Weaver had basically guessed that it was, in fact, some sort of Faster-Than-Light drive. It took nearly a year of tinkering, and two more planets, to figure out that it was, in fact, such a drive. It had taken another year to create the first prototype starship.

By then, Weaver had switched sides in the ongoing sales war, leaving the Beltway and taking a direct commission in the Navy, which was the lead service in developing the world's first spaceship. He'd pointed out even before switching sides that the Navy just made more sense. The President wanted a presence off-world as fast as possible. They'd picked up enough intel in the brief war to know that the Dreen had some sort of FTL as well. Finding out where the Dreen were, whether they were headed to Earth through normal space, was a high priority. The only way to make a spaceship, fast, was to convert something. The obvious choice had been one of the many ballistic missile submarines that were being decommissioned.

So Weaver, while continuing to consult on engineering issues, was now the astrogation officer of the Naval Construction Contract 4144. Despite a couple of shakedown cruises around the solar system, the Top Secret boat had yet to be named. The 4144 had all the beauty and problems of any prototype. Most of the equipment was human, much of it original to the former SSBN Nebraska. Other bits were Adar or Human-Adar manufacture. The fact that it worked at all was amazing.

"How fast are the missiles? I mean, space is big, right, so they have to be fast?" Miller continued peering out the window, on a submarine, in front of him. The window seemed to be harder to get used to than the fact that he was standing inside humanity's first starship. A freakin' window on a submarine, he thought.

"The propulsion system is a mix of Adar tech and human. The thing is basically designed around the old nuclear thermal rocket concept but uses a small quarkium reactor instead of a fission reactor. No radiators needed and we use a dense Adar coolant for propellant instead of LOX or hydrogen or water. The Adar stuff gives us waaaay better m-dot. Using an Adar material for the nozzle we were able to get over eight thousand seconds of specific impulse out of it."

(ed note: 8,000 Isp is an exhaust velocity of about 78,000 m/s. Which would make that propulsion system a torch drive. Freaking missile has performance better than a blasted Zubrin nuclear salt water rocket.)

from Vorpal Blade by John Ringo (2007)

Non-scientific Media SciFi Ships

If you want to ignore this entire website and just make a tired old standard TV or Movie spaceship utterly without scientific accuracy, Mythcreants has you covered. But don't let RocketCat catch you or he will give you an atomic wedgie.

Actually, if you actually want such a thing, what are you doing in this website in the first place?


(ed note: Now remember that this is only for movies and TV shows, not novels. And it is more of a joke than something serious, though it is surprisingly accurate.)

The other day, I was scrolling through Netflix, looking for a distraction from all the pain of my hair and all my terrible car opinions, seeking out some quality space-travel-focused sci-fi, because I love that crap. As I was scrolling, looking at the thumbnails of the various movies and shows and whatever, I realized something: when those thumbnails showed a picture of a spaceship, you could almost instantly know, generally, what that show or movie was about. I mean it! Here, let me show you.

There’s almost always at least one signature spacecraft for any of these space-based sci-fi shows, and I was realizing that they design of the ships, while varying wildly from movie to movie, seemed to be remarkably consistent for a given sub-genre of space sci-fi.

You could look at one ship and immediately know that, say, the show would take place in the relatively near future, and have a pretty good gorunding in science, or look at another and immediately know nobody gave two shits about physics, but it’ll be a fun ride.

I compiled several thousand examples and fed them into the Jalopnik Mainframe (a cluster of over 400 Timex-Sinclair 1000 computers dumped into an abandoned hot tub in a bunker underneath Ed Begley Jr’s combined EV R&D lab/sex-lab) which ran an advanced AI that categorized the ships into eight distinct classes. I took those ship classes, translated the descriptions into English from the AI’s native Dutch, and produced this handy chart, which you can use to make your space-movie choices quicker and better!

Did we miss any categories? I’m pretty sure most space-based sci-fi fits into one of these. Star Wars is 4, Star Trek is 3, I’d put the monolith from 2001 and 2010 in 7 but the Discovery and Leonov in 2, and I think the big cylindrical Heighliners from Dune go in 7.

Categorize your favorites! What could it hurt, right?

(ed note: the following is from a thread on Twitter)


     Class 0 - B Movies
     Class 1 - REALISM
     Class 2 - Kubrick land
     Class 3 - Where every nerd has gone before
     Class 4 - Cosmic thrillers
     Class 5 - The one from Wall-E
     Class 6 - Independence Day and it's imitators
     Class 7 - Overly pretentious crap

     RedPyre: Also, as someone that used to be in the Star Trek ship discussion fandom and left for more hard sci fi pastures, "This type of sci fi generates the most painful geek fights" on class 3 is WAY too accurate.

     Ilan Muskat: This is supposed to be a goof, but boy oh boy is it a handy narrative shorthand. It's real, real hard to separate philosophy from aesthetics.

     Winchell Chung: Agreed!
     "Narrative Shorthand", that's the concept I've been groping for, thanks!
     Anybody who wants a dubious graduate thesis can ask the question if the visual categories in the chart approximate some sort of archetypal images embedded in the human psyche.
     My question is Why is it so easy to make a chart like this?
  • Is the scifi movie visual aesthetic riddled with clichés?
  • Are there too few concept artists?
  • Are the movie visual directors too conservative?
  • Does the target audience demand it?
  • or what?
     My other question: is the chart comprehensive? Or are there other commonly used narrative shorthand tropes that got left out?

     Mike Doscher: These basic categories serve to explain the world and the nature of the story with the need for certain classes of exposition. In a meta sense they also describe the story creators and the expectations of the audience.
     As pipelines become longer and more expensive, visual treatments need sign-off from multiple people, each of which needs convinced as to viability of the project. This ultimately tends to channel visual treatments into certain categories.
     This isn't because people are dumb, but rather that you're playing a high-stakes game of telephone where everyone has their own interests that they're pursuing at the same time the team is trying to get the project made.

     Winchell Chung:

     Makes perfect sense to me. On a related note, I've heard similar arguments about why there are so many re-makes of existing movies. The high-stakes nature of movies makes a "built-in audience" an increase in project viability

     Craig Perko:

     Clarity of first impressions. Just like how we design warriors to be big bulky dudes with huge shoulderpads...

     Winchell Chung:

     From Douglas Adams The Restaurant at the End of the Universe:
     The designer was clearly not instructed to beat about the bush. “Make it evil,” they’ve been told. “Make it totally clear that this gun has a right end and a wrong end. Make it totally clear to anyone standing at the wrong end that things are going badly for them. If that means sticking all sorts of spikes and prongs and blackened bits all over it then so be it. This is not a gun for hanging over the fireplace or sticking in the umbrella stand, this is a gun for going out and making people miserable with.”

     Supership 79:

     What about the Expanse? Class 4 and Class 2 hybrid?
     The expanse has very thought-out ship designs and while they're heavily greebled you can always tell what faction they're from and what the basic function of the ship is, and the science is Good Enough to not be flat out space opera.

     Tom Anderson:

     Is "you can always tell what faction they're from" compatible with "very thought-out"? Why haven't ship designs converged on a global optimum?
     Genuine question, I haven't watched the show!
     I'm trying to think of historical examples of this. Maybe the way the Soviets stuck to jet fighters with an air intake right at the front, when virtually no western jets did that (I can only think of the Lightning)?

     Supership 79:

     Its mostly in what color lighting and paint schemes the ships use. earth ships are bluish, mars ships are reddish, and belter ships are yellowish. Anyways its a great show, highly recommended.

     Cyrs the unsinkable sea serpent:

     Yes, paint is how you tell them apart, not design (too much at least) because regardless of your politics, your physics are pretty fixed

     Pete Appleby:

     All part of having a clear narrative, but still in the real world you can absolutely tell at a glance who are from a Soviet origin as opposed to Western, whatever it may be ship, aircraft, clothing, switch... the cultural aesthetic is everywhere. Good sci fi has that consistency

     Ilan Muskat:

     I don't 100% see where Star Control/Futurama/Cosmic Encounter fit in, the "wacky hijinks" space smorgasbord that's not *quite* the Planetary Romance of Class 0, but not quite the Geek-Continuity Rigmarole of Class 3. (Maybe if the protagonist's ship looks like a banana.)
     Barbarella has enough class 0 for all BD

     Winchell Chung:

     Yes, agreed. Needed is some category for whimsical/absurd ships. Like "Mega Maid" from Spaceballs.

     Don't forget Queen Amora's swan spaceship from Flesh Gordon. Looked all ethereal while flying. Crashed, the swan showed all those girders and burnt airframe members sticking out of the wreckage. Very absurd.

     NickStevens Graphics:

     Or the Flesh Gordon “ship”

     Ilan Muskat:

     Heck, Battle Beyond the Stars. "If your protagonist's space ship looks like a part of human anatomy that would be censored from Instagram..."
     "The ship looks like a giant person" also applies to Necromongers from Chronicles of Riddick (otherwise mostly Class 4) and Gurren Lagann (Class... banana, again)


     Wouldn't Nell be class 7 (bio-inspired shape)? except it fails the deep ideas and being philosophical part.
     Funnily, Battle Beyond the Stars has several examples of the other categories as well.

Mythcreants: Designing Your Spaceship

What Is Your Ship’s FTL Propulsion Method?

It turns out space is big. Really big. Getting around means you’ll have to massage your way past Einstein’s rule that nothing can go faster than the speed of light.

Going Really, Really Fast

Your ship just pours on the speed, never mind what physics says. Despite the talk of warping space, this is essentially the Star Trek method. While the ship accelerates to well past the speed of light, it never leaves normal space. It can still scan the area ahead,* so it won’t be taken by surprise if there’s a hostile fleet lying in wait. Another consequence is that going FTL is only an escape if you’re faster than the other guy. They can still track you after you’ve kicked it up to full throttle.

Visiting a Pocket Dimension

Since this universe won’t let us go FTL, let’s go to another one. This is the hyperspace of Star Wars and Babylon Five (B5). Exiting our universe completely, these ships tunnel through their own personal dimension to get where they need to go. Usually, this means that activating the ship’s FTL drive makes it safe from attack. There can be exceptions, but jumping to hyperspace will usually be a moment of relief. Because it’s such a powerful way to get out of trouble, there should be limits on when it can be used. In Star Wars, ships can’t go into hyperspace within a planet’s gravity well. In B5, it requires specially constructed gates for all but the largest ships.


Even more extreme than the pocket dimension, there’s no travel time at all with this method. The ship simply disappears from one place and reappears in another. It’s most famously seen on Battlestar Galactica (BSG), but it appears in other stories as well, such as the Solar Clipper series by Nathan Lowell.

Ships with this form of propulsion can travel truly massive distances. Even if the jumps they make are relatively short, the only limiting factor is how quickly they can recharge for another one. This means that ships can easily escape any kind of trouble so long as their engines are working. BSG limits this with time consuming FTL equations and a delay as the ship drives spool* up. As a side benefit, a teleportation drive means that ships often end up nose to nose, rather than millions of miles apart.

It Doesn’t Have One

It turns out that the speed of light is a difficult speed limit to break, and authors looking for a more science-friendly story often stay below it. Your ship can still go plenty fast with sublight engines, fast enough to make interplanetary travel a breeze. You’ll be limited to one solar system, sure, but look how much there is to explore right in our own backyard. Limiting your ship to sublight speed will make it more realistic, and allow you to engage in nitty gritty science fiction.

How Does Your Ship Move at Sublight?

No matter what your FTL method is (if you have one), your ship will still need to get around in normal space. How you do this will have a big influence on the level of your setting’s technology, not just how you get from place to place.

On a Carefully Projected Course

This is the current method for navigating our solar system. 21st century spacecraft have very limited fuel, so they have to plan nearly every bit of thrust, leaving nothing to chance. The course that Rosetta took to rendezvous with the comet 67P, for example, is incredibly complicated, and full of complex math. When Apollo 13 suffered a damaging explosion, they couldn’t just turn around and fly back to Earth. They had to keep going on the course they’d committed to.

Using this method will make fuel management an active part of your story. The characters won’t be able to go wherever they please; they’ll have to be constantly watching their tanks. It’s very limiting, but the good news is that because this is how real spaceships work, there’s plenty of reference material. This is hard scifi at its finest.

A variant is to use engines that have extremely long-lasting fuel sources but produce little acceleration. Ion engines fit the bill nicely. Ships can get going at a good clip with a long enough burn, but deviating from their course will be very difficult because of how long it takes to build up thrust.

With Impulse Engines

This is the standard for the vast majority of space-going scifi settings. The ship employs some kind of extremely efficient reaction drives to push it where it needs to go. When Captain Picard orders his ship into orbit of a new M-class planet, he’s not worried about running out of gas before they get there. Even in Firefly, when Mal does occasionally fret about running out of fuel, it’s understood that this isn’t a problem for better funded ships. When in doubt, this is the option to go with. It’s tried and true, letting you explore your setting without much fuss.

By Raising the Solar Sails

This is a quirky third option if you want to give your ship more of an old-timey feel. Solar sails are a real technology that uses solar wind ([sic] They use solar photons, not solar wind) to generate thrust. Your ship will work more like a sailing ship, and who doesn’t want sailing ships in space? With a bit of handwavium, you can even borrow a bunch of nautical terminology to spice up your setting’s jargon. Your ship can tack across the port quarter and run up the mainsail.*

Practically, this method of propulsion has some caveats to consider. Ships will be slower further from the sun,* and going toward the sun will be more difficult than going away. The sail itself is also important. It would be huge and no doubt prone to damage. This is your chance to get an astronaut swinging through the rigging to repair meteorite impacts!

What’s the Interior Like?

The inside of your ship is at least as important as the outside. Do your characters feel at home within its hull, or is each day a strain on their nerves?

NASA Chique

If you ever take a look at the International Space Station, you’ll notice that it’s incredibly crowded. There’s stuff floating everywhere because space is at a premium. This is the look you go with if you want your ship as close to modern technology as possible. There probably wouldn’t be artificial gravity. The food would mostly be slurped from bags. Using the bathroom would be… complicated.

This is the kind of ship one has to be very dedicated to serve on. It lends itself to explorers making the first push to Mars or maybe homegrown space enthusiasts cobbling together their own ship form whatever is lying around.

Military Practical/Cold and Austere

These two are different sides of the same coin and are essentially the difference between Battlestar Galactica and Battlestar Pegasus. Both are function over form. Practicality reigns over comfort. Everything has a purpose, and nothing is wasted. The difference is that on Galactica this is reassuring. Everything is running like a well-oiled machine. On Pegasus it’s unnerving. All human comforts have been swallowed up by the unfeeling ship. On the TV show, they achieve this with lighting, camera work, and music. In prose, you can do this with positive and negative descriptors: “clean” vs “sterile” or “disciplined” vs “controlled.”

Characters on this kind of ship are most likely military or maybe high-level corporate types. They’re here to do a job. That won’t be the only aspect of their characters, but it will be ever-present. They’ll all be part of something bigger than themselves, whether they want to or not.

Warm and Lived In

Welcome aboard either Serenity or the Millenium Falcon. These ships are homes as well as machines. Even if the characters don’t necessarily want to be on board, the ship’s environment will have a calming effect. This works on the audience as well, if you do it right. They will start to feel comfortable with the ship, like slipping on an old sweater. They’ll react viscerally if the ship is threatened by intruders. Use this to set up poignant stories.

This kind of ship is often independently owned but not always. Star Trek’s Deep Space Nine space station fits the bill, as does Babylon Five. It’s a place where people live as well as work, and they can’t help but leave their mark.

Like a Space Hotel

This is an odd choice pioneered by Star Trek: The Next Generation. The Enterprise D is so well appointed that it often feels like some kind of cruise ship. The quarters are palatial, anyone can have anything they want to eat whenever they want it, and the holodecks provide endless forms of entertainment. This kind of ship is meant to awe the audience. To make them think, “Wow, the future is amazing!”

There’s nothing wrong with that, but it can make your characters harder to identify with. Drama loses some of its edge if the characters can return home to their cabins and order a three course meal while getting a deep tissue massage.

How Good Are Its Sensors?

Unless you’re in very old science fiction, your ship’s going to need more than the mark one eyeball to see with. Looking out the window just won’t cut it in the cold vacuum.

Only Blips on a Screen

This level of technology is pretty close to what we have today. Sensors will tell you that something’s out there and maybe its mass, but that’s it. Unless the mystery object is broadcasting a signal, you won’t know anything about it. This is great for building tension and suspense. What’s that blip out there? It’s getting closer. Should we open fire?

The downside is that it’s a very involved method. Your characters can never just know what’s going on with another ship. They’ll always have to question their information, and the audience will want to know how they learned it.

Like Long Range Eyes

The next step up are sensors that give you about the same information as a visual examination of whatever’s being scanned. You can tell that little blip is a TIE fighter, that it has Imperial markings, but not that it’s carrying Lord Vader. This method provides a decent balance, allowing you to easily describe what’s happening around your ship without giving too much information to the audience. It works particularly well for a setting like Star Wars, in which the space battles are clearly analogous to historical naval combat when visual range encounters were common.

They Give a Full Spectrum Scan

Star Trek sensors can tell you what an approaching ship is made of, how many people are on board, and how many of them own cats. There is seemingly no end to the pinpoint information these scanners can produce from remarkably far away. This is another case of wowing your audience with the wonders of the future. It also allows you to put on dazzling displays of description as the characters learn absolutely everything about what they’re looking at. Of course, you have to be good at description in order for that to work.

The drawback to having such powerful sensors is that sometimes drama depends on the characters not having certain information. Many an episode of Trek features the previously all-seeing scanners inexplicably not noticing that a hostile ship was charging weapons. You can sometimes explain this by saying there’s some kind of interference or another, but that excuse will get tired if you aren’t careful.

How Does It Fight?

Space battles are an ever-present element of science fiction, and chances are if there’s a ship in your story, it will eventually be attacked. How does it defend itself? Or, if its crew is a bit more proactive, how does it attack other ships?

It Doesn’t

One of the novel things about Firefly was that, as Jayne so eloquently put it, “A transport ship ain’t got no guns on it.” Serenity was completely unarmed, which made things interesting when it ran into hostile vessels that weren’t. If your ship has no weapons, your characters will have to be more inventive. They can’t just blow the attacking space pirates out of the sky. They have to run and hide or cobble some kind of weapon together. It limits your options, but it can be engaging.

With Directed Energy

Whether it’s a simple laser or something more complicated, this is a beam of energy projected across space at the speed of light. It has very long range. It’s precise and accurate. If you can see something, you can hit it with this weapon. Space battles with such a weapon will be short, as there isn’t a lot of maneuvering to be done when incoming fire is moving at the speed of light. This is good news if you’re in a visual medium with a limited budget, but perhaps bad news if you want to film the Battle of Britain in Space. Early Star Trek used this kind of weapon a lot, before Deep Space Nine (DS9) took things in a more WWII type direction.

Using Space Guns

These are any weapons that operate more or less the way modern firearms do. BSG has actual space guns – that is, shells propelled by explosive chemicals. Star Wars has space guns disguised as directed energy weapons. They call them lasers or blasters, but they clearly operate more like battleship cannons. The biggest advantage to this style of weaponry is that building dramatic space battles is easy. You just take your inspiration from historical naval battles, especially WWII. You can have giant capital ships slugging it out broadside to broadside while fighters dogfight around them.

The downside is that you aren’t taking full advantage of being in space. Space is a completely alien environment, and it’s limiting to focus exclusively on how battles used to be fought.

By Lobbing Missiles

As mentioned, space is really big. Your ships will often be so far apart that light will take several minutes to cross the gulf between them. At that range, even a laser is useless. Instead, your ship could use guided, self propelled projectiles that can travel to the target and adjust their course to ensure a hit. This type of weaponry is seen in the Honor Harrington series, where it introduces a completely different dynamic to space combat.

Battles become tense waiting games as enemy missiles come burning in. The fire-and-forget nature of these weapons means that once they are launched, the characters can only watch and hope for a hit. The main action of combat focuses around using countermeasures against incoming fire. It requires a different mindset than the more fast paced battles with space guns, but it has an appeal all its own.

It Sends Out Fighters

From X-Wings to Vipers to Star Furies, fighters are a mainstay of space combat. If your ship is big enough, it may fight primarily by launching smaller craft to attack the enemy. This allows for some excellent drama. Dogfights between fighters are perfect for moments of individual heroism, and fighter pilots will always be popular as main characters. Plus, removing your characters from the safety of their mothership is a great way to ratchet up the danger.

Of course, this method isn’t always practical. You need a ship big enough to carry fighters, for one thing. For another, space fighters aren’t terribly realistic. Targeting systems would probably be too accurate for dodging and weaving to be an effective defense. Fighters also imply your ship is purpose-built for combat, which won’t work in many stories.

It Uses a Mix

Chances are very good that your ship will use some combination of the above options. Galactica has both fighters and space guns. The Enterprise has directed energy weapons with its phasers, while photon torpedoes are much more like missiles. The key is to remember what each kind of weapon means for your story.

How Do Characters Get Off It?

No matter how cool your spaceship is, eventually the characters will have to leave it. How do they do that?

By Landing and Docking

If your spaceship is on the smaller side, it may let people off directly, whether that means landing on a planet’s surface or docking with a space station. Larger ships can do this as well, but it starts to get impractical, especially with landing. Having this be your ship’s primary means of egress puts a major limit on your characters’ freedom of movement. They can only go where the ship goes. It also means that if the ship is damaged, getting off it will be more difficult, which is great for drama.

On Shuttles

The most practical method, especially for larger vessels, this means your ship carries a number of smaller craft that are fully functional spaceships in their own right. They have a limited range of course, but they’ll get you to the ground and back. This increases your characters’ freedom of movement, allowing some to visit the big city while others explore mysterious alien ruins. It also opens the possibility of a story with one or more characters trapped and isolated on a damaged shuttle.

The important thing to remember is that the ship breaking doesn’t mean the shuttles are broken. If the ship has a power failure, the audience will immediately ask why the characters don’t divert power from the independent shuttle engines.

Via Teleportation

While transporters were originally a way for Gene Roddenberry to save money on landing sequences, they have since carved out a place for themselves in science fiction. These are devices that move a character from one place to another instantaneously. They can work via matter energy conversion, micro-wormholes, or anything else that sounds reasonably scientific. They offer unparalleled freedom of movement, getting your characters into places they’d have no other way of reaching. You no longer have to spend time on travel sequences or explain how the characters arrived so quickly.

The drawback is that sometimes you’ll have stories that only work if your characters can’t get somewhere. Teleportation is such a powerful way of getting around that you may have trouble writing it properly. If you’re going to use this method, establish early what can and can’t be teleported through, and then stick with it.

How Does It Look?

In this last section, we consider your ship’s physical appearance. We’re looking at broad strokes rather than specific details. Decide on the shape and paint job once you’ve considered some broader themes.

Old and Beat Up

As seen with Serenity, the Millenium Falcon, and every other independent trading vessel ever featured in a science fiction story. This is the look of the underdog. It’s a scrappy ship that’s got heart. In other words, something we will always root for. It’s great for communicating how outmatched and poorly equipped the main characters are, which is something the audience will love.

Big and Mean

This ship means business. If it’s not bristling with weapons, it’s some kind of mega cargo carrier that can fit a dozen lesser ships inside it. This look projects power. It is imposing, and communicates a level of seriousness to your story. You don’t want to use this look for a lighthearted romp through the solar system, but it’s perfect for an epic war with evil robots. Note that the ship doesn’t actually have to be large. DS9’s Defiant is a small ship, but it’s definitely Big and Mean.

Sleek and Sexy

The true ship of the future, a triumph of technology and engineering. This ship will dazzle the audience with all its swanky design features. Pair this with a Hotel in Space look for the interior, and you have the Enterprise D. Ships like this work best in optimistic settings, where they portray the awesome heights humanity can achieve. Your protagonist may come off as something of a tool if they’re flying one of these in a gritty, realistic setting where people have to scrounge for survival.

By now you should have a pretty good idea what your spaceship is like, at least in terms of the big picture. The rest can be added as you go. These steps will get you a skeleton, but you’ll still have to fill in the rest. How comfortable is the captain’s chair? What kind of noise do the engines make? These smaller scale questions should be addressed as they come up, but now you have a solid foundation to base them on.


Yes, alien spacecraft are not going to look like ISO Standard Human Spaceships. But it is debatable that they will look as if designed by Cthulhu.


The sci-fi equivalent of a guy wearing a black hat and twirling his mustache. Or rather, one thousand razor-sharp metallic mustaches twirling all at once with the energy of a thousand suns glowing beneath its armored plates.

Or, if you prefer, the Badass Longcoat of spaceships.

Obviously if a spaceship is meant for atmospheric maneuvers too, it would make sense for it to be aerodynamic. This is not about that. Nor is it about dagger-shaped Star Destroyers. No. This is about spaceships with way more than any practical numbers of sharp edges.

This trope describes a spaceship that ranges from a dart-like multi-pronged fighter to a gigantic armored Kraken brimming with blades, spikes, antennae, metallic claws and for good measure, a huge glowing maw at the front like some hellspawned sea creature. Unfortunately, this trope has becoming close to generic, and a new design trick when coming up with such vessels is to make them asymmetrical and thus slightly less conventional.

At first, this kind of starship design was a radical departure from what at the time was standard in film and TV, but with advancing technology, especially computer generated imaging, TV and movie spaceships became increasingly complicated as programmers could animate smaller and smaller individual segments. This has caused an explosion in the number of sharp edges and non-functional moving parts assigned to antagonist spaceship designs to the point where most people in fiction powerful enough to threaten a planet are seen flying around in giant metal squids with a hundred vicious claws and blades on every tentacle.

On the inside, these ships are usually just your standard blue-lit control centers, huge docking bays, and very long metal corridors. But the sheer number of metallic blades and tentacles just screams "Look at me, I am so marvelously evil!"

As a general rule, the spaceships become more squid/octopus-like as they grow in size and in the number of spikes and blades they possess. Often they possess a Wave Motion Gun and for extra points, the ship has to radically and slowly transform its shape just to use it, giving the heroes enough time to disarm the superweapon.

While it makes sense for a small ship designed for atmospheric maneuvers to be aerodynamic and sleek, the larger "Kraken" varieties are almost always Awesome, but Impractical.

If a ship has two long, spear-like engine or weapons pods, it's technically not this trope. This is about when enemy spaceships go way overboard on the sharp edges to impractical levels. How does a pilot climb inside such a ship without tearing their pressure suit?

Compare Spikes of Villainy, the costume version of this trope.

Also compare Eldritch Starship, which can really look like anything, but utilizes mind-bending, conceptually alien principles in its design and may or may not look like a giant metallic sea urchin.

(ed note: see TV Trope page for list of examples)


...something astonishing and strange had happened to Volyova’s ship. The ship had remade itself into a festering gothic caricature of what a starship ought to look like... He had heard of ships being infected with the Melding Plague... but he had never heard of a ship becoming so thoroughly perverted as this one while still, so far as he could tell, being able to continue functioning as a ship.

—Clavain describing the Nostalgia For Infinity, Redemption Ark

The polar opposite of ISO Standard Human Spaceship, these are spacecraft, time machines, and/or interdimensional vehicles whose weirdness goes beyond Living Ship and possibly into Alien Geometries or a mobile version of the Eldritch Location.

The milder form of this usually begins with Bigger on the Inside or dimensionally transcendent in some way other than bog-standard Faster-Than-Light Travel, and it only grows weirder from that point on. May involve Body Horror or invoke elements of Cosmic Horror Story.

They might be constructed from unconventional materials, powered by unconventional power sources, be dimensionally transcendent, or have an Unusual User Interface. Their interiors may even look like they were designed by M. C. Escher. There's no guarantee that the crew or the ship itself won't change its interiors (or even its exterior) from time to time. Frequently they are a Genius Loci or function as a Setting as a Character. They are always surreal in some way that a typical spaceship in fiction just isn't.

The trope has three major variations (with a lot of overlap), but beyond these three archetypes there is much, much variety:

  • "Starfish" Spaceship - as in Starfish Alien, only for technology. These are spacecraft whose very conceptual design, let alone its performance, seems to defy the laws of physics both in-universe and in Real Life.

  • "Changeling" Spaceship - spacecraft that is physically possible, but transforms radically (not just extendable wings and the like). The interior, exterior, or both could transform.

  • "Lobster" Spaceship - spacecraft that is physically possible, and probably has engines, a bridge, etc., but much of the ship seems to be a Lovecraftian mass of antennae, spines, blades, metallic tentacles and other parts of uncertain function.

(ed note: see TV Trope page for list of examples)


Eldritch Starship: Oh, there are a few.

Take esseli starships, for example. Unlike the link!n-Rechesh (who would be another fine example), they know better than to try to grow fully organic starships, so from outside the hulls and drives look relatively normal. Then you go through the airlock, and it’s all flesh, all the time, with heart-valve doors, neuron-cluster control interfaces, food-secreting glands, recycling intestines, and suspicious organic gurgles everywhere. Mining ships have refinery stomachs and tentacles.

Múrast starships are carved out of ice bodies, with the necessary technology fitted within, and then refrozen. Which is all very sensible when you consider their favored environment, but doesn’t explain why they always carve them into baroque cathedral-like structures rather than anything more utilitarian.

And then there are the seb!nt!at, who as creatures of nuclear forces that dwell deep within stars, do not build their starships out of matter in any conventional sense.

Starfish Aliens build Starfish Starships, basically, just as far as physics will allow.

The tortured structures built by rogue mining drones and other wild mechanicals are about as Gigeresque as it gets, though.


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Type: Space Ferry

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Type: Orbit-to-Orbit

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Type: Airless Lander

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Type: Shuttlecraft

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Type: Tanker

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Type: Tug

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Type: Cargo Ship

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Cargo Containers

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Space Truckers and Trains

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Type: Warship

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Type: Space Ark

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Water Wall

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Kuck Mosquito

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Water Truck

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Water Ship

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Type Notes

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Organic Spacecraft

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