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.
|0||Human Being||1.77 meters/5.8 feet|
|1||Giraffe||6 meters/20 feet|
|2||City Bus||12 meters/40 feet long|
|3||Small Orion Drive ship||21 meters/70 feet|
|4||Millennium Falcon||35 meters/115 feet||Star Wars|
|5||Polaris||43 meters/140 feet||Tom Corbett, Space Cadet|
|6||Moonship||44 meters/144 feet||Chesley Bonestell,|
Conquest of Space
|7||Luna||46 meters/150 feet||Destination Moon|
|8||Arc De Triomphe||50 meters/164 feet|
|9||Orion Drive Mars|
|50 meters/165 feet|
|10||United Planets Star|
|51 meters/170 feet wide||Forbidden Planet|
|11||Nautilus||51 meters/170 feet long|
|12||Space Shuttle stack||56 meters/180 feet|
|13||Absyrtis||60 meters/197 feet||G. Harry Stine,|
|14||Boeing747||71 meters/231 feet|
|16||Ferry Rocket||81 meters/265 feet||Collier's Magazine,|
22 March, 1952
|17||Statue of Liberty||93 meters/300 feet|
|18||DE-51 Destroyer Buckley||93 meters/306 feet|
|19||Saturn V||111 meters/363 feet|
|20||DY-100 Botany Bay||92 meters/302 feet||Star Trek|
|21||California Redwood||112 meters/367 feet|
|15||RS-10||128 meters/420 feet||Andre Norton Star Born|
|22||Discovery||140 meters/459 feet||2001, A Space Odyssey|
|23||Romulan Bird of Prey||131 meters/430 feet||Star Trek|
|24||Great Pyramid of Cheops||139 meters/455 feet|
|25||Oscar class submarine||155 meters/509 feet|
|26||Galactic Cruiser Leif Ericson||168 meters/551 feet||Leif Ericson Model|
|27||Washington Monument||169 meters/555 feet|
|28||Klingon D7 battlecruiser||228 meters/750 feet||Star Trek|
|245 meters/804 feet|
|30||BB-62 Battleship New Jersey||270 meters/887 feet|
|31||NCC 1701 Starship Enterprise||289 meters/950 feet||Star Trek|
|32||Eiffel Tower||300 meters/984 feet|
|33||CVN-65 Carrier Enterprise||342 meters/1,123 feet|
|34||Empire State Building||443 meters/1,454 feet|
|35||Al Rafik||102 meters/335 feet||Attack Vector: Tactical|
|36||Tachi/Rocinante||46 meters/151 feet||The Expanse|
|37||10 Story Building||30 meters/98 feet|
|38||International Space Station||109 meters/358 feet|
|39||X-Wing Fighter||13 meters/41 feet||Star Wars|
|40||Eagle Transporter||31 meters/100 feet||Space 1999|
|41||Shuttle Orbiter||37 meters/122 feet|
|42||Type S Scout||39 meters/128 feet||Traveller RPG|
|43||Serenity||58 meters/190 feet||Firefly|
|44||DDG-90 Destroyer Chafee||155 meters/510 feet|
|45||ISV Venture Star||1,646 meters/5,400 feet||Avatar|
|46||CVN-68 Aircraft Carrier Nimitz||333 meters/1,092 feet|
|47||Imperial Star Destroyer||1,600 meters/5,249 feet||Star Wars|
|48||Scoutship Vega||20 meters/66 feet||Leif Ericson Model|
|49||Michael Battleship||132 meters/433 feet||Footfall|
|50||Orion Battleship||78 meters/256 feet|
|51||ANNIC NOVA||78 meters/256 feet||Traveller RPG|
|52||Valley Forge||1,600 meters/5,249 feet||Silent Running|
|53||Klingon K't'inga class|
|349.54 meters/1,147 feet||Star 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
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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
|Attack Vector: Tactical||0.25 ton/m3|
|Jet Airliners||0.28 ton/m3|
|Fighter Aircraft||0.35 ton/m3|
|Wet Navy Warships||0.5 to 0.6 ton/m3|
|WWII Battleships||0.7 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.
|Space Shuttle External Tank||0.011 ton/m3*|
|Long Duration Exposure Facility||0.049 ton/m3|
|Leonardo Multi-Purpose Logistics Modules||0.058 ton/m3|
|Hubble Space Telescope||0.061 ton/m3|
|International Space Station||0.074 ton/m3|
|Space Shuttle Orbiter||0.088 ton/m3|
|Space Station Mir||0.175 ton/m3|
|Space Shuttle Solid Rocket Booster||0.206 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.
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.
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:
|Thermal (heat radiators)||3.4%|
|Guidance, Navigation, and Control||8.0%|
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 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.
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.
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.
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:
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.
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.
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.
Physicist Luke Campbell had some additional suggestions:
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.
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.
The British Interplanetary Society (BIS) in general, and Sir Arthur C. Clarke in particular figured that there were three main types of spacecraft needed for the exploration of space: Space Ferry, Orbit-to-Orbit, and Airless Lander. Each is optimized for their own particular area of use.
More recently, orbital propellant depots and their related tanker ships also seem like a good piece of infrastructure. There are some sample realistic designs here, here, here, here and here. Not to mention here and here.
However, space warships are an entirely different kettle of fish.
The space ferry concept is what evolved into the NASA space shuttle. Its function is to boost payload into orbit, though you can think of it as an "atmospheric lander." Refer to the section on Surface To Orbit.
These are sometimes called "interface vehicles" because their function is to transport payload through the interface boundary between Terra's atmosphere and airless space.
The idea was to re-use as much of the rocket as possible, which is why the upper section has wings and the lower stages had parachutes. In Robert Heinlein's Space Cadet, the rocket is launched from a rocket sled going up the side of Pike's Peak. Nuclear powered rockets could boost more massive payloads, but a space elevator could boost so much more cheaply and efficiently.
Hop Davis estimates that space ferries launching from Terra will require a delta-V budget of around 10 kilometers per second (with orbital propellant depot) and require a thick atmosphere for aerobraking. It will require a bit more if there is no orbital depot, but not much more because coming down it uses aerobraking instead of propellant. The delta-V budget means they will probably have to be multi-stage if they are chemical rockets (good luck getting permission to use nuclear rockets). They will require a propulsion system with a thrust-to-weight ratio above 1.0.
Orbit-to-orbit spacecraft never land on any planet, moon, or asteroid.
Therefore they are free to use efficient propulsion systems with a thrust-to-weight ratio below 1.0, such as ion drives or VASIMR. They require no landing gear or parachutes. If there ain't no landing gear, it is an orbit-to-orbit. No streamlining is required either. They require no ablative heat shields unless they are designed to perform aerobraking to burn off delta-V without requiring propellant (like the Leonov in the movie 2010 The Year We Make Contact).
Hop Davis estimates that a orbit-to-orbit spacecraft will require a delta-V budget of only 3 to 4 kilometers per second, if orbital propellant depot are available. Otherwise it will be twice that, with along with a dramatic reduction in payload capacity. 4 km/s is well within the capabilities of a chemical rocket, but any higher and you will probably need staging or a propulsion system with more exhaust velocity.
The old image of orbit-to-orbit ships look like dumb-bells, the front ball is the cargo and habitat module, the rear is the propellant and radioactive atomic drive. The stick in between is a way to substitute distance for lead radiation shielding.
These are designed for landing on bodies that have no atmosphere, but you probably could get away with using them on Mars. They evolved into NASA's Apollo Lunar Module. So they will require some sort of landing gear. But no streamlining. They will require a propulsion system with a thrust-to-weight ratio near 1.0, depending on the surface gravity of the bodies they are designed to land on. This probably means chemical propulsion, maybe a solid-core NTR. Hop Davis estimates that airless lander spacecraft will require a delta-V budget of around 5 kilometers per second if orbital and surface propellant depots are available. Otherwise it will be twice that, with along with a dramatic reduction in payload capacity.
For sample designs, go to the Lander page.
So the smart way to design is to use an orbit-to-orbit spacecraft to travel between planets, and at a planetary destination use locally based surface-to-orbit services: either a space ferry, airless lander or surface-to-orbit installation at a spaceport.
But what if there are no locally available surface-to-orbit services? If NASA dispatches a Mars mission, there ain't no Martian space shuttles to ferry the crew down to the surface.
Making the entire spacecraft land-able is often a bad idea. For one, optimizing a spacecraft for both orbit-to-orbit and surface-to-orbit operations will probably result in an inefficient ship with the disadvantages of both and the advantages of neither. If you are designing with a weak propulsion system, it might not even be possible. And even if your propulsion system is up to the task, often it is better to park your ticket home in orbit where it is safe while other means are used to send crew into a possibly dangerous situation.
The standard solution is for the main spacecraft to carry small auxiliary spacecraft as landers, either aerodynamic space ferries or airless landers. The popular term from Star Trek is "Shuttlecraft".
A large space ferry shuttlescraft on modestly sized orbit-to-orbit spacecraft can make the ship look like an arrow.
Many aerospace engineers have pointed out that all of these spacecraft can be far more cheap and efficient if there were orbital depots of propellant and/or fuel established in various strategic locations where space travel is desired. This will necessitate some sort of tanker-type spacecraft to keep the depots supplied. They will be a species of orbit-to-orbit spacecraft optimized to carry huge amounts of propellant, and hopefully be unmanned drones or robot controlled. They can use an efficient propulsion system with thrust-to-weight ration below 1.0, ion or VASIMR. Like standard orbit-to-orbit, probably a delta-V budget of 4 km/sec, unless they are in a real hurry.
There will also be a species of airless lander optimized to carry propellant to planetary based depots, this is called a "lighter". As all landers the propulsion thrust to weight ratio will have to be near 1.0, probably chemical propulsion. As standard airless lander, probably a delta-V budget of 5 km/sec. The lighter will probably be designed to land a single modular tank from the cluster carried by the tanker.
(ed note: The Cargo ship section is quite long, click the Hide button if you want to skip over this section)
If spacecraft actually lands on a planet it may be a belly-lander instead of a tail-sitter, for ease of cargo loading/unloading. Otherwise it is like unloading cargo from the 25th floor window of a skyscraper.
Conventional cargo spacecraft have a conventional ship arrangement: a rocket engine aft of a cargo hold. You know, like pretty much every rocket you've ever seen: engines on the bottom.
The hold is an enclosed area to store cargo in, sections of which may or may not be pressurized. Unpressurized sections are for cheaper storage of inert durable cargo, e.g., raw ore. Pressurized sections are more expensive storage for delicate cargo that can be easily ruined by temperature and pressure extremes, e.g., produce and live animals.
The cargo hold may be rigged with attachment points for cargo containers. The hatches may be such to allow accessing individual containers. Alternatively the hold might be basically a huge tank. This is used for bulk cargo: liquids, gases, asteroid ore dust or gravel, grain, etc.
Cargo spacecraft might not bother with an enclosed area at all. Instead cargo containers are carried on the outside of spacecraft, attached to the ship's spine.
Unconventional cargo spacecraft have the rocket engine before the cargo hold. The engines are on the top.
This uses a waterskiing arrangement, with the engine and everything acting like a waterbound motorboat, dragging the cargo behind like a water skier. The rocket exhaust is angled such that it doesn't incinerate the cargo (but angled just barely enough to minimize thrust cosine loss). If the spacecraft carries relatively few cargo cans it is a Space Truck. If it carries long strings of cargo cans it is a Space Train. Yes, the boundary between a truck and a train is totally arbitrary.
Conventional cargo spacecraft may or may not be capable of landing on a planet (airless or with atmosphere). If the cargo ship cannot land and the local infrastructure is primitive, the cargo ship may have to carry landing shuttles to ferry cargo to and from the surface. If the local infrastructure is advanced, the ship can rent shuttle services from the local spaceport.
Unconventional cargo spacecraft are highly unlikely to be capable of landing at all. Certainly not if the planet has an atmosphere.
For transporting huge amounts of cargo, a safe bet is that the space industries will settle on a standard cargo container size. Because in the real world this lead to the miracle of Containerization. Which transformed global trade and built, nay even changed the world.
They would allow standardized design of cargo holds, they work well with space trucks and space trains, heck they work well as inert cargo vessels. Surface to Orbit services would probably be optimized to accommodate standard cargo container form factors.
Standarized cargo containers would become ubiquitous and cheap enough to find secondary markets for just the empty containers.
In the real world there are DIY people who alter shipping containers into inexpensive houses. In a RocketPunk future such containers can be tansformed into crude habitat modules by adding a few incidentals (plugging leaks, a bare bones life-support system, an airlock). Add some engines and you have a scratch-built spacecraft. Ikea in Space will probably offer inexpensive habitat modules based on shipping containers.
A new interstellar space colony on a shirt-sleeve habitable planet might bring along a commercial Farm From A Box to jump-start their agricultural self-sufficiency. Everything you need for a quick farm, neatly packed inside a shipping container. It's a kit!
Other "kits" mounted inside shipping containers include water treatment plants and electrical power generators. The military has shipping container kits containing medical surgery theaters, command and control facilities, and missile launchers.
And science fiction authors looking for an interesting (comments) background situation for their novel can pick up a few hints by doing a web search for news containing the search term "cargo container."
Eric Tolle was of the opinion that hexagonal cargo containers would probably be for bulk dry goods, Liquids would would best in cylinders or spheres, and containerized shipping would be best in rectangular cargo pods.
- Intermodal container
- Intermodal freight transport
- Twenty-foot equivalent unit
- Unit load
- Stowage plan for container ships
An intermodal container is a large standardized shipping container, designed and built for intermodal freight transport, meaning these containers can be used across different modes of transport – from ship to rail to truck – without unloading and reloading their cargo. Intermodal containers are primarily used to store and transport materials and products efficiently and securely in the global containerized intermodal freight transport system, but smaller numbers are in regional use as well. These containers are known under a number of names, such as simply container, cargo or freight container, ISO container, shipping, sea or ocean container, sea van or (Conex) box, sea can or c can.
Intermodal containers exist in many types and a number of standardized sizes, but ninety percent of the global container fleet are so-called "dry freight" or "general purpose" containers, durable closed steel boxes, mostly of either twenty or forty feet (6.1 or 12.2 m) standard length. The common heights are 8 feet 6 inches (2.6 m) and 9 feet 6 inches (2.9 m) – the latter are known as High Cube or Hi-Cube containers.
Just like cardboard boxes and pallets, these containers are a means to bundle cargo and goods into larger, unitized loads, that can be easily handled, moved, and stacked, and that will pack tightly in a ship or yard. Intermodal containers share a number of key construction features to withstand the stresses of intermodal shipping, to facilitate their handling and to allow stacking, as well as being identifiable through their individual, unique ISO 6346 reporting mark.
In 2012, there were about 20.5 million intermodal containers in the world of varying types to suit different cargoes. Containers have largely supplanted the traditional break bulk cargo – in 2010 containers accounted for 60% of the world's seaborne trade. The predominant alternative methods of transport carry bulk cargo – whether gaseous, liquid or solid – e.g. by bulk carrier or tank ship, tank car or truck. For air freight, the lighter weight IATA-defined unit load device is used.
Ninety percent of the global container fleet consists of "dry freight" or "general purpose" containers – both of standard and special sizes. And although lengths of containers vary from 8 to 56 feet (2.4 to 17.1 m), according to two 2012 container census reports about 80% of the world's containers are either twenty or forty foot standard length boxes of the dry freight design. These typical containers are rectangular, closed box models, with doors fitted at one end, and made of corrugated weathering steel (commonly known as CorTen) with a plywood floor. Although corrugating the sheet metal used for the sides and roof contributes significantly to the container's rigidity and stacking strength, just like in corrugated iron or in cardboard boxes, the corrugated sides cause aerodynamic drag, and up to 10% fuel economy loss in road or rail transport, compared to smooth-sided vans.
Standard containers are 8-foot (2.44 m) wide by 8 ft 6 in (2.59 m) high, although the taller "High Cube" or "hi-cube" units measuring 9 feet 6 inches (2.90 m) have become very common in recent years. By the end of 2013, high-cube 40 ft containers represented almost 50% of the world's maritime container fleet, according to Drewry's Container Census report.
About 90% of the world's containers are either nominal 20-foot (6.1 m) or 40-foot (12.2 m) long, although the United States and Canada also use longer units of 45 ft (13.7 m), 48 ft (14.6 m) and 53 ft (16.15 m). ISO containers have castings with openings for twistlock fasteners at each of the eight corners, to allow gripping the box from above, below, or the side, and they can be stacked up to ten units high. Regional intermodal containers, such as European and U.S. domestic units however, are mainly transported by road and rail, and can frequently only be stacked up to three laden units high. Although the two ends are quite rigid, containers flex somewhat during transport.
Container capacity is often expressed in twenty-foot equivalent units (TEU, or sometimes teu). A twenty-foot equivalent unit is a measure of containerized cargo capacity equal to one standard 20-foot (6.1 m) long container. This is an approximate measure, wherein the height of the box is not considered. For example, the 9 ft 6 in (2.9 m) tall high-cube, as well as 4-foot-3-inch half-height (1.3 m) 20-foot (6.1 m) containers are equally counted as one TEU. Similarly, extra long 45 ft (13.72 m) containers are commonly designated as two TEU, no different than standard 40 feet (12.19 m) long units. Two TEU are equivalent to one forty-foot equivalent unit (FEU).
In 2014 the global container fleet grew to a volume of 36.6 million TEU, based on Drewry Shipping Consultants' Container Census. Moreover, in 2014 for the first time in history 40-foot High cube containers accounted for the majority of boxes in service, measured in TEU.
Manufacturing prices for regular, dry freight containers are typically in the range of $1750—$2000 U.S. per CEU (container equivalent unit), and about 90% of the world's containers are made in China. The average age of the global container fleet was a little over 5 years from end 1994 to end 2009, meaning containers remain in shipping use for well over 10 years
Other than the standard, general purpose container, many variations exist for use with different cargoes. The most prominent of these are refrigerated containers (a.k.a. reefers) for perishable goods, that make up six percent of the world's shipping boxes. And tanks in a frame, for bulk liquids, account for another 0.75% of the global container fleet.
Although these variations are not of the standard type, they mostly are ISO standard containers – in fact the ISO 6346 standard classifies a broad spectrum of container types in great detail. Aside from different size options, the most important container types are:
- General-purpose dry vans, for boxes, cartons, cases, sacks, bales, pallets, drums, etc., Special interior layouts are known, such as:
- rolling-floor containers, for difficult-to-handle cargo
- garmentainers, for shipping garments on hangers (GOH)
- Ventilated containers. Essentially dry vans, but either passively or actively ventilated. For instance for organic products requiring ventilation
- Temperature controlled – either insulated, refrigerated, and/or heated containers, for perishable goods
- Tank containers, for liquids, gases, or powders. Frequently these are dangerous goods, and in the case of gases one shipping unit may contain multiple gas bottles
- Bulk containers (sometimes bulktainers), either closed models with roof-lids, or hard or soft open-top units for top loading, for instance for bulk minerals. Containerized coal carriers and "bin-liners" (containers designed for the efficient road and rail transportation of rubbish from cities to recycling and dump sites) are used in Europe.
- Open-top and open-side containers, for instance for easy loading of heavy machinery or oversize pallets. Crane systems can be used to load and unload crates without having to disassemble the container itself. Open sides are also used for ventilating hardy perishables like apples or potatoes.
- Platform based containers such as:
- flat-rack and bolster containers, for barrels, drums, crates, and any heavy or bulky out-of-gauge cargo, like machinery, semi-finished goods or processed timber. Empty flat-racks can either be stacked or shipped sideways in another ISO container
- collapsible containers, ranging from flushfolding flat-racks to fully closed ISO and CSC certified units with roof and walls when erected.
Containers for Offshore use have a few different features, like pad eyes, and must meet additional strength and design requirements, standards and certification, such as the DNV2.7-1 by Det Norske Veritas and the European standard EN12079: Offshore Containers and Associated Lifting Sets.
A multitude of equipment, such as generators, has been installed in containers of different types to simplify logistics – see containerized equipment for more details.
Swap body units usually have the same bottom corner fixtures as intermodal containers, and often have folding legs under their frame so that they can be moved between trucks without using a crane. However they frequently don't have the upper corner fittings of ISO containers, and are not stackable, nor can they be lifted and handled by the usual equipment like reach-stackers or straddle-carriers. They are generally more expensive to procure.
Basic dimensions and permissible gross weights of intermodal containers are largely determined by two ISO standards:
- ISO 668:2013 Series 1 freight containers—Classification, dimensions and ratings
- ISO 1496-1:2013 Series 1 freight containers—Specification and testing—Part 1: General cargo containers for general purposes
Weights and dimensions of the most common standardized types of containers are given below. Values vary slightly from manufacturer to manufacturer, but must stay within the tolerances dictated by the standards. Empty weight (tare weight) is not determined by the standards, but by the container's construction, and is therefore indicative, but necessary to calculate a net load figure, by subtracting it from the maximum permitted gross weight.
Container 20' 40' 40' high-cube 45' high-cube 48' 53' External
Length 19 ft 10.5 in
40 ft 0 in
40 ft 0 in
45 ft 0 in
48 ft 0 in
53 ft 0 in
Width 8 ft 0 in
8 ft 0 in
8 ft 0 in
8 ft 0 in
8 ft 6 in
8 ft 6 in
Height 8 ft 6 in
8 ft 6 in
9 ft 6 in
9 ft 6 in
9 ft 6 in
9 ft 6 in
Length 19 ft 3 in
39 ft 5 45⁄64 in
39 ft 4 in
44 ft 4 in
47 ft 6 in
52 ft 6 in
Width 7 ft 8 19⁄32 in
7 ft 8 19⁄32 in
7 ft 7 in
7 ft 8 19⁄32 in
8 ft 2 in
8 ft 2 in
Height 7 ft 9 57⁄64 in
7 ft 9 57⁄64 in
8 ft 9 in
8 ft 9 15⁄16 in
8 ft 11 in
8 ft 11 in
Width 7 ft 8 1⁄8 in
7 ft 8 1⁄8 in
7 ft 6 in
7 ft 8 1⁄8 in
8 ft 2 in
8 ft 2 in
Height 7 ft 5 3⁄4 in
7 ft 5 3⁄4 in
8 ft 5 in
8 ft 5 49⁄64 in
8 ft 10 in
8 ft 10 in
Internal volume 1,169 cu ft
2,385 cu ft
2,660 cu ft
3,040 cu ft
3,454 cu ft
3,830 cu ft
Empty weight 4,850 lb
Net load 61,289 lb
Each container is allocated a standardized ISO 6346 reporting mark (ownership code), four letters long ending in either U, J or Z, followed by six digits and a check digit. The ownership code for intermodal containers is issued by the Bureau International des Containers (International container bureau, abbr. B.I.C.) in France, hence the name BIC-Code for the intermodal container reporting mark. So far there exist only four-letter BIC-Codes ending in "U".
The placement and registration of BIC Codes is standardized by the commissions TC104 and TC122 in the JTC1 of the ISO which are dominated by shipping companies. Shipping containers are labelled with a series of identification codes that includes the manufacturer code, the ownership code, usage classification code, UN placard for hazardous goods and reference codes for additional transport control and security.
Following the extended usage of pallet-wide containers in Europe the EU started the Intermodal Loading Unit (ILU) initiative. This showed advantages for intermodal transport of containers and swap bodies. This led to the introduction of ILU-Codes defined by the standard EN 13044 which has the same format as the earlier BIC-Codes. The International Container Office BIC agreed to only issue ownership codes ending with U, J or Z. The new allocation office of the UIRR (International Union of Combined Road-Rail Transport Companies) agreed to only issue ownership reporting marks for swap bodies ending with A, B, C, D or K – companies having a BIC-Code ending with U can allocate an ILU-Code ending with K having the same preceding letters. Since July 2011 the new ILU codes can be registered, beginning with July 2014 all intermodal ISO containers and intermodal swap bodies must have an ownership code and by July 2019 all of them must bear a standard-conforming placard.
Containers come in many different types, each with a designation to distinguish the different types and uses. Designation for each container is (size)(type)/(tech level). There are three sizes of containers, coded as 4A (8 dtons or 112 cubic meters), 4C (4 dtons, 32 m3) or 4D (2 dtons, 16 m3). Containers are 3 meters high by 3 meters wide, and include all doors and fittings for cargo handling equipment. The size 4A containers are 12 meters long, 4C containers are 6 meters long, and 4D containers are 3 meters long.
Cargo Container Types
Container types Type Code Name Description 00 General Purpose A simple box with doors at both ends. 05 Sealed Same as type 00, but capable of being sealed against external atmosphere. Does not include life support or environmental controls. 32 Controlled Environment A type 05 but including environmental controls for heat and cooling. Can maintain any temperature between -35°C and 50°C. Requires external power supply, and has a 24 hour battery power supply. 50 Open Top Same as type 00, but missing the top. 55 Open Frame An open box frame with structural cross members. Used as a frame for heavy equipment. Can be covered with a flexible covering. 67 Modular A box designed to come apart into the six sides. Can be used as a type 00, type 50, or type 55, or folded flat for shipment. Four flat containers can be shipped in the space of one assembled container. 70 Tank A type 55 with a tank for transporting liquids or gasses in bulk. 90 Habitat A modular office, building component, or habitat. Provides full life support and cramped cabin quarters. Requires external power supply for life support, and has a 24 hour battery supply.
(ed note: This is a modification to the rules for the Traveller role playing game. But the reasoning is of general interest to cargo starship designers. Costs are in Travelle "credits" or CR, more or less equivalent to $1 US)April 2014 issue.
Why are standard cargo containers in Traveller 3m wide, 3m high and 6m long? Because no one consider the implications of containerized cargo on Earth when they wrote that description decades ago. Nor did they consider the standards for starships in Traveller. The standard cargo container, as written, is unusable in the standard starships, as written, in Classic Traveller.
A subsidized merchant (Type R) cannot stack two standard cargo containers in its hold because the deck height is only 6m. There would be no room to maneuver them about. From past experience working in steel yards and manufacturing plants, I would say as a minimum the decks would need to be 6.3m apart in order to safely stack two 3m containers, and it seems the writers of Fire, Fusion, & Steel 2 would agree because they suggest a minimum door size that is 10% larger in dimension than the corresponding dimension of anything that will be moved through it.
So let’s take a fresh look at containerized cargo for Traveller. On Earth, while there are occasionally containers dented by mishandling, it is rare, so a Traveller armor rating of 1 seems to be a reasonable ‘guesstimate’. This is also the standard minimum for grav vehicles, probably for much the same reason.
If the deck heights will be 3m then the maximum height of cargo containers should be 2.7m since starships will be the primary mode of transport. Does anyone know the Imperium’s standard axle size? Never mind, we’ll leave the other two dimensions at 3m and 6m. An Imperial standard shipping container would have a surface area of 84.6m2 and an external volume of 48.6 m3. Other important measurements depend on composition, per the table below.
Standard Cargo Container Measurements TL Material Volume* Mass (kg) Cost (Cr) 0 Light Wood 42.557 2.417 1,813 1 Wood 45.683 2.334 1,167 3 Iron 48.205 3.163 633 4 Soft Steel 48.252 2.785 558 5 Hard Steel 48.304 2.366 592 6 Titanium Alloy 48.403 1.578 1,973 7 Light Composite 48.452 1.037 1,038 8 Composite Laminate 48.501 0.790 790 9 Light Ceramic Composite 48.482 0.711 1,067 10 CrystalIron 48.526 0.742 668 12 Superdense 48.558 0.635 593 16 Collapsed CrystalIron 48.570 0.385 651
* Internal volume available to shipper, in m3
Containers are inexpensive and finding them “repurposed” to other functions would be quite likely. Researching “container architecture” might offer some ideas.
None of these would be vacuum resistant and the TL 0 and 1 containers couldn’t be made so. Adding a cargo door (e.g. one that was proof against vacuum) would add to the cost. Since most starships maintain shirt-sleeve environments in cargo areas this usually won’t be a problem; however, for high end cargos it might be worth a shipper’s while to pop for the added protection.
Cost of Vacuum-resistant Cargo Containers TL Cost (Cr) TL Cost (Cr) 3 3,647 8 6,825 4 4,708 9 6,582 5 4,604 10 7,131 6 5,661 12 7,540 7 6,227 16 7,707
A container could hold a kiloton of high density material so planetary standards bodies would probably call for a maximum gross mass. What that would be IYTU would depend on what standards exist for cargo moving equipment. Present-day ISO standards call for a maximum net load of 28.2 tonnes but present-day standard cargo containers are 21% smaller than those described here, so 38 tonnes would be comparable on a volume for volume basis.
There are probably sub-containers available as well. These would be designed to fit inside the main container with little wiggle room. They might be standardized or not IYTU. Because they are protected by the main container they would have no minimum standards and could be as simple as plastic or cardboard boxes. Standard widths would be 2.8, 1.4, 0.93, 0.7, 0.56, 0.46, 0.4, 0.35, and possibly 0.31, 0.28, 0.25, and 0.23. Standard lengths would be 5.8, 2.9, 1.93, 1.45, 1.16, 0.96, 0.82, 0.72, 0.64, 0.58, 0.52, and 0.48. Standard heights would be less likely, especially on the smaller end, but if you had them they would probably be on the order of 2.4, 1.2, 0.8, 0.6, 0.48, 0.4, 0.34, 0.3, 0.26, 0.24, 0.21, and 0.2.
Note that the widths and lengths refer to their placement within the main container. One could have sub-containers that were longer from side to side of the main container than they were front to back, relatively speaking.
Most PCs won’t know or care what’s inside the shipping containers in the hull, but if you have PCs that do something other than standard merchant type activities this information could be useful. There are actually companies that arrange sub cargos for small concerns that cannot afford to ship full containers and they make good money saving their customers money on shipping by bundling their shipments with others to form full containers.
I am arbitrarily defining a conventional cargo ship as one with the engines in the aft section of the spacecraft, while space trucks and space trains have the engines in the fore section (like an 18-wheeler or a choo-choo train). The only difference between space trucks and space trains is the number of cargo cannisters.
As attractive as is the admirable reduction in radiation shield mass offered by the waterskiiing spacecraft concept, there are practical problems in being towed on the end of a kilometer-long cable.
But the bit about using tension instead of compression members is still a worthwhile idea. Take some species of space tug, mount the propusion system on outriggers so the exhaust does not fire directly back along the ship's spine, and attach cargo modules to massive couplings on the bottom of the thrust frame.
As with all cargo spacecraft, delicate cargo will be housed in pressurized temperature-controlled cannisters but bulk ores and other insensitive cargo will just be dragged along in nets.
Space Truckers haul relatively small numbers of cargo modules, often attached to a framework. However if the tug is hauling a long chain of cargo modules, this is more like a freight train with a locomotive at the front and a string of freight cars in tow. A "space train" as it were.
Much like railroad locomotives, this will be less like loading crates into a seagoing container ship and more like latching cargo cans into long strings terminating at the rocket engine at the top.
This was the lead ship for the warp superconvoys, the 100-kilometer cargo carriers that revolutionized interstellar industrial transport. Configured in 8-ship linked octogons at the head of the convoy, with 4-ship squares of booster tugs after each 10-container segment, and all controls subspace-radio synchronized, these superconvoys transported billions of kilograms per superconvoy.
Specifications Length 225 m Beam 220 m Draught 45.6 m Mass 72.5 million kg Ship's Complement Officers
5 Crew 61 Std Ship's Complement 66 Performance Range 2000 light-years Cruising Speed Empty - Warp 3.5
Loaded - Warp 2
Engines Adv 3rd Gen Warp Drive Fuel 1:1 matter/antimatter Notes Tractor beam coupling for cargo containers
Most powerful thrust in starship history
SUPERCONVOYS OPEN NEW ERA OF TRADE: Billion ton ships are boon to industry (2161)USS MULETRAIN, PROVIDER CLASS
ALBERTO SABELLA, CHIEF ENGINEERING OFFICER
It's working! Warp effect is being engaged, and this superconvoy is rolling! Next stop—Centauri Spaceworks.
I'll let the boys upstairs take the glory, but the truth is old greasemonkey Sabella down here in the Engine Room is who straightened this whole mess out, I must admit in all humility.
Problem: how to transport raw materials from whistle-stop asteroid belts in the boondock sectors to the space factories of the UFP? And I'm not talking a freighter or two here. I'm talking about the billions and billions of metric tonnage needed each stardate to feed the Federation's ravening industrial plant. Star Fleet is stymied.
Solution: Sabella to the rescue. lt's elementary, I patiently explain, what we need are warp convoys of a hundred freighters and more. It can't be done, sneer the design baboons. No ship could produce a warp effect that great. Who said anything about one ship? I reply.
So I spelled it out for them. At the head of the convoy, assemble a configuration of heavy warp-drive tugs, say eight of them in an octagon. Lock their controls together and use the whole pile as the inertial driver. Next, string out a dozen or so of those new kilometer-long cargo cans, coupling them with tractor beams. Then—and here my brilliance staggers even my own modest self—plug in another configuration of warp tugs, four should do it, and knit the rest of the convoy with the same pattern, synchronize it all with subspace radio so that all warp engines engage simultaneously, and ride into the sky!
It can't be done, cry the designers.
An interesting conjecture, muses star Fleet.
It can be done, admit the designers in wonderment. Maybe only warp 2 or so, but this would save years of travel time, and trillions of credits.
Trillions? asks Star Fleet. Maybe we'll consider it. They considered it, they did it, it's done.
Merely brilliant, Sabella, I say. Merely brilliant.
LARGEST SPACELIFT EVACUATES DOOMED PLANET (2165)USS ENDURANCE, MANN CLASS
OKURU NELSON, ADMIRAL
Our flagship Endurance has run a final sensor scan of Bayard’s Planet, and I can report with certainty that not a single inhabitant has been missed by this, the largest spacelift in history. None too soon either. The shock wave from the supernova explosion that destroyed the Kepler will reach this systems sun in less than three star-dates, and it is 100 percent probable that it will initiate a chain reaction nova.
And the nova will destroy all life in the star system. All oceans will boil away; the gamma ray bombardment will scorch the surface; the planet itself may undergo an internal disruption and blow apart. it was imperative that Bayard’s Planet be evacuated. But how to evacuate ten million inhabitants? With the biggest spacelift ever.
Every starship within a fifty light-year radius was pressed into the effort by special request of the UFP. And I am just amazed by the response. Cruisers, destroyers, scout-ships, corvettes, all rendezvoused. Also trading clippers, low-warp tugs, even pleasure crafts of every type all rallied to the cause.
But all these valiant volunteers twice over could not have removed ten million people in time. Then an engineer in Star Fleet Merchant Marine named Sabella came up with the novel idea of refitting those new super-convoys with life support and jury-rigged decks. And that turned the corner for us. Starbase 5 renovated two superconvoys to accommodate passengers in an amazingly short time, and after weeks of impossible logistics and unmeetable timetables, we have succeeded in evacuating the entire planet. The galaxy has never seen an operation of this scope before. And I for one fervently hope it never has to again.
This is far more speculative, since as far as we know there have not been any space warships created yet. Refer to Warship Design, Warship Gallery, Space War: Intro, Space War: Detection, Warship Weapons Intro, , Warship Weapons Exotic, Space War: Defenses, Space War: Tactics, and Planetary Attack.
Fundamentally they are weapons platforms, so by definition they will be carrying various weapons systems. They may or may not have armor or other defenses, they may or may not have human crews. They probably will have an over sized delta-V capacity, and a large thrust capacity so they can jink around and complicate the enemy's targeting solution (i.e., dodge around so you are harder to hit). Lasers will require large amounts of power, and huge heat radiators and heat sinks to cope with waste energy. They will probably be carrying little or nothing that cannot be used to attack the enemy.
Space Arks are an outer-space version of that old Noah story: some cosmic apocalypse is going to obliterate the world, so it behoves the human race to evacuate to another world a breeding population of humans, a civilization starter kit, as much of the worlds scientific knowledge and culture they can cram in, and a viable subset of Terra's ecosystem (with redundancy, none of this "two by two" nonsense). Yes, it is a popular scifi trope.
It is basically a colony ship to establish an interstellar colony. Except the stakes are higher and the build time is limited. The time limit is set by the arrival date of the apocalypse. Designing it won't be easy. If the ship can be designed to be indefinitely habitable (a "worldship") then the journey to a safe place can be done leisurely. But since such ships are generally built in a clawing rush, they have a limited life until their warranty runs out. So the journey has to be as fast as possible.
Another challenge is attempting construction of the space ark while all the selfish people in the entire freaking world try to seize it for their own survival.
The space ark can be a generation ship or a sleeper ship. A popular option is putting an engine on the end of a space colony. A more challenging option is putting an engine on Terra large enough to move the entire planet somewhere safer. But that is out of the scope of "types of spaceships." Or is it?
John Brunner's epic novel THE CRUCIBLE OF TIME is about an alien race whose planet is faced with annihilation by an oncoming nebula. However the focus in the novel is more on the thousands of years before the building of the ark. The aliens are starting with medieval levels of scientific ignorance and do not even know they are in danger. It is a race to see if they can develop enough science to make space arks before the nebula clobbers them.
- The Epic of Gilgamesh
- Battle for Terra
- Titan A.E.
- Sky Captain and the World of Tomorrow
- After Earth
- The Bear with the Knot on His Tail by Stephen Tall
- Olias of Sunhillow by Jon Anderson
- Star Trek TOS "For the World is Hollow and I Have Touched the Sky"
- Warhammer 40,000's Eldar craftworlds
- Halo universe megastructure "The Ark"
- When Worlds Collide
- Born of the Sun by Jack Williamson
- Outpost video game
- Building Harlequin's Moon by Larry Niven and Brenda Cooper
They are lofted into orbit by either a chemical booster or laser launch service. Or manufactured in orbit; with Maw, Paw, and their brood buying tickets on a passenger service then taking possession.
At the cheapest they are basically a habitat module which rents propulsion services from a space tug, momentum bank, or a power-beaming service. Mid-range models will be something like a hydro ship, with some efficient and cheap (but low thrust) integral propulsion system. Top-of-the-line will be something approaching a full blown space tug, with enough delta-V to haul cargo.
These are examined in more detail here.
As mentioned in the section on Ice Mining, when it comes to the industrialization and colonization of space, water is the most valuable substance in the Universe. Among other things it can be used for life support, reaction mass, and radiation shielding.
There will be lots of robot asteroid miners, many who will specialize in volatiles such as water. These include the CFW NEO MicroMiner, the Robot Asteroid Prospector (RAP), the Asteroid Provided In-Situ Supplies (APIS), the Kuck Mosquito, the Water Truck, and the Water Ship.
There is a prototype life support system called the Water Wall that is mostly composed of water.
There is even a rocket engine called the Microwave Electrothermal Thruster which uses water for reaction mass, has a respectable exhaust velocity of up to 9,800 m/s, is very reliable, and can easily be powered by solar panels. Oh, and unlike ion drives, you can make massed clusters of the little darlings and they won't electromagnetically interfere with each other. You can make an array of 400 or so to produce a whopping 12,000 Newtons of thrust. They are also very easy to repair. Even by an amateur.
Best of all, if you mix water with a binder and freeze it, you get Pykrete, which is a building material. You could even use it to, well, build a spaceship or space station with. This turned up in Neal Stephenson's science fiction novel Seveneves, but there is no reason it couldn't be done in reality.
Which means you could make a spacecraft that was mostly water.
For an example, see the Spacecoach below.
Now this would not be suitable to make space battleships or space fighters with, but it would be dandy for interplanetary wagon trains for Maw and Paw Kettle to go homesteading in the asteroid belt. Mostly made of water, which cheaply comes from in-situ resource utilization. Not the strongest nor the most durable, but very affordable.
This would also be useful for somebody with limited access to raw materials. Say, refugees from a galactic war entering a remote uninhabited star system, carrying only whatever odd bits of material and tools that will fit into the cargo space not filled with refugees.
In 2010 Brian S. McConnell and Alex Tolley developed the Spacecoach concept and published it in a paper Reference Design for a Simple, Durable and Refuelable Interplanetary Spacecraft. This relatively low cost orbit-to-orbit spacecraft would be admirably suited for wagon trains in space. They could actually open up the solar system to pioneers if coupled with a low-cost surface-to-orbit transportation system such as a laser launcher. But McConnell and Tolley think the mass could be brought down enough to bring it within the boost capacity of, say a SpaceX Falcon 9 or Falcon 9 Heavy.
The basic premise of the spacecoach is to create a fully reusable orbit-to-orbit spacecraft that uses water and waste gases from crew consumables as its primary propellant.
So the design makes the consumables mass do double duty: first as life support for the crew, then as propellant. This drastically lowers the mass of the spacecraft, thus lowering the cost.
This also removes the incentive to install an expensive and cantankerous closed ecological life support system. Yes, supplies for a multiple year journey take up a lot of mass, but since it can be lumped under the heading of "propellant" it does not matter as much.
The water component of the consumables can do triple or quadruple duty. Before it is used as propellant, it can also serve as radiation shielding, supplemental debris shielding (as pykrete), and thermal regulation. In his simulation boardgame High Frontier developer Philip Eklund called water "the most valuable substance in the universe", and he was not kidding.
The spacecoach is also mostly constructed of water, in the form of pykrete. Very little metal is to be used. Actually it is very much like the composite ship from The Martian Way
The spacecoach will have sizable solar cell arrays used to power some species of electric rocket. There is some research underway to determine which of the many electric propulsion systems works best with water.
Ion drives, VASIMR, and helicon double layer rockets won't work because they are electricity hogs. They need to be fed by a nuclear reactor or equivalent, solar cells are too weak. Besides the insane price tag on a reactor and the ugly mass penalty, governments will be dubious about entrusting Maw and Paw Kettle with nuclear energy. They do have wonderful exhaust velocities, but the price is just too blasted high. Some won't even work with water as propellant.
Hall Effect Thrusters, Microwave Electrothermal Thruster (MET), and Electrodeless Lorentz Force Thruster (ELF) are much more suitable. They require much more modest amounts of electricity. Their exhaust velocities are weaker than the electricity hogs, but they are still much more potent than puny chemical rockets. These drives are also simpler to fabricate (i.e., cheaper, more reliable, lightweight, durable, and easily serviced). They can be clustered into arrays in order to increase the thrust. Electricity hog drives start interfering with each other if you cluster them.
The MET is especially simple. It isn't much more than a metal tube with a microwave magnetron attached. No moving parts either. It is sort of like a cross between a rocket engine and a microwave oven.
Current research shows a MET using water propellant can crank out a good 8,800 m/s exhaust velocity (Isp 900 sec) while an ELF can do about 16,700 m/s (Isp 1,700 sec). A Hall Effect thruster using water could theoretically do 29,000 m/s (3,000 sec) but researchers are still trying to figure out how to adapt them to water propellant.
For back-of-the-envelope calculations figure a spacecoach engine can do from 7,900 m/s to 20,000 m/s exhaust velocity (Isp 800 sec to 2000 sec). Compare this with chemical rocket's pathetic 4,400 m/s (450 sec).
20,000 m/s might not be quite enough to manage a trip to Ceres (10.593° inclination to ecliptic means a lot of delta V is needed), but the performance may be improved with more research.
The low thrust also minimizes the need for mass-expensive structural members.
McConnell and Tolley do have several design competitions open.
This is from Water Walls Life Support Architecture: 2012 NIAC Phase I Final Report (2012)
The idea here is to make a environmental control life support system (ECLSS) with a higher redundancy and reliability by making it passive, instead of active. Meaning instead of needing a blasted electrically-powered water-pump moving vital fluids around, use special membranes so that the vital fluids automatically seep in the proper direction. Fewer points of failure, fewer moving parts, no electricity needed, much more reliable.
The system harnesses the power of Forward Osmosis (FO), which mother nature has been using for the last 3.5 billion years since the first single-celled organism. Each unit has two compartments A and B, which share a wall made out of what they call a "semi-permeable membrane".
Compartment A contains contaminated water. Compartment B contains a solution (the "draw solution") which attracts water like a magnet using osmotic pressure. The contaminated water gets sucked through the semi-permeable membrane but leaves the contaminants behind (because the membrane won't let them through). The pure water (or purer water) winds up in compartment B with the draw solution and the contaminants remain in compartment A.
Since osmotic pressure is used there is no need for an electrical-powered water pump. It happens naturally just like a ball rolling downhill.
The research team noted that there already exists a commercial example of this: the X-Pack Water Filter System by Hydration Technology Innovations. You put nasty river water full of toxins and pathogens in compartment A and add a special sports-drink syrup into compartment B as draw solution. In about 12 hours compartment B will be filled with a refreshing sterile non-toxic sports-drink and all the horrible crap will be left behind in A.
So the research team realized that they could make a full ECLSS if they could develop some different types of forward osmosis bags and connect them together. They need bags that can do CO2 removal and O2 production (via algae), waste treatment for urine, waste treatment for wash water (graywater), waste treatment for solid wastes (blackwater), climate control, and contaminant control.
As a bonus cherry on top of the sundae, since all these will basically be bags of water, they can do double duty as habitat module radiation shielding.
The reliability comes from using lots of independent inexpensive disposable bags. The current system depends on driving an electromechanical water pump until it fails, then frantically trying to repair the blasted thing before all the toilets back up. Because the FO bags are cheap and low mass, they can be considered disposable, the spacecraft brings along crates of them with the other life support consumables. Because each bag uses forward osmosis as a built-in pump, there is no single point of failure. When one bag or cluster of bags, or integrated module of bags uses up their capacity, you switch the water line to the next units in sequence. The used bags can be cleaned, filled, and reused. Alternatively they can be stuffed somewhere in the habitat module to augment the radiation shielding.
|Specific Power||4.8 kW/kg|
|Thrust Power||484 megawatts|
|Specific Impulse||450 s|
|Exhaust Velocity||4,400 m/s|
|Wet Mass||350,000 kg|
|Dry Mass||100,000 kg|
|Mass Flow||49 kg/s|
|Initial Acceleration||0.06 g|
Kuck Mosquitoes were invented by David Kuck. They are robot mining/tanker vehicles designed to mine valuable water from icy dormant comets or D-type asteroids and deliver it to an orbital propellant depot.
They arrive at the target body and use thermal lances to anchor themselves. They drill through the rocky outer layer, inject steam to melt the ice, and suck out the water. The drill can cope with rocky layers of 20 meters or less of thickness.
When the 1,000 cubic meter collection bag is full, some of the water is electrolyzed into hydrogen and oxygen fuel for the rocket engine (in an ideal world the bag would only have to be 350 cubic meters, but the water is going to have lots of mud, cuttings, and other non-water debris).
The 5,600 m/s delta-V is enough to travel between the surface of Deimos and LEO in 270 days, either way. 250 metric tons of H2-O2 fuel, 100 metric tons of water payload, about 0.3 metric tons of drills and pumping equipment, and an unknown amount of mass for the chemical motor and power source (probably solar cells or an RTG).
100 metric tons of water in LEO is like money in the bank. Water is one of the most useful substance in space. And even though it is coming 227,000,000 kilometers from Deimo instead of 160 kilometers from Terra, it is a heck of a lot cheaper.
Naturally pressuring the interior of an asteroid with live steam runs the risk of catastrophic fracture or explosion, but that's why this is being done by a robot instead of by human beings.
In the first image, ignore the "40 tonne water bag" label. That image is from a wargame where 40 metric tons was the arbitrary modular tank size.
There are more details here.
|Specific Power||9.6 kW/kg|
|Propulsion||Solid core NTR|
|Specific Impulse||198 s|
|Exhaust Velocity||1,942 m/s|
|Wet Mass||123,000 kg|
|Dry Mass||30,400 kg|
|Total ΔV||2,740 m/s|
|Total Propellant||92,600 kg|
|Boost Propellant||75,700 kg|
|Landing Propellant||16,900 kg|
|Boost ΔV||1,859 m/s|
|Landing ΔV||881 m/s|
|Mass Flow||155 kg/s|
|Initial Acceleration||0.25 g|
|Tank Length||8.5 m|
|Total Length||11.9 m|
|Guidance Package||0.45 tons|
and Feed Lines
|Landing System||0.68 tons|
|25% Growth Factor||2.09 tons|
The Lunar ice water truck is a robot propellant tanker design by Anthony Zuppero. Its mission is to boost 20 metric tons of valuable water from lunar polar ice mines into a 100 km Low Lunar Orbit (LLO) cheaply and repeatably. It is estimated to be capable of delivering 3,840 metric tons of water into LLO per year.
This design uses a nuclear thermal rocket with currently available materials, and using water as propellant (a nuclear-heated steam rocket or NSR) instead of liquid hydrogen). This limits it to a specific impulse below 200 seconds which is pretty weak. However, numerous authors have shown that a NSR could deliver 10 and 100 times more payload per launched hardware than a H2-O2 chemical rocket or a NTR using liquid hydrogen. This is despite the fact that the chemical and NTR have much higher specific impulses. NSR work best when  the reactor can only be low energy,  there are abundant and cheap supplies of water propellant, and  mission delta-Vs are below 6,500 m/s.
The original article describes the water extraction subsystem at the lunar pole. It is a small reactor capable of melting 112.6 metric tons of ice into water (92.6 metric tons propellant + 20 metric tons payload) in about 45 hours. This will allow the water truck to make 192 launches per year, delivering a total of 3,840 metric tons of water per year.
Since the water truck is lifting off under the 0.17 g lunar gravity, its acceleration must be higher than that or it will just vibrate on the launch pad while steam-cleaning it. The design has a starting acceleration of 0.25 g (about 1.5 times lunar gravity).
The landing gear can fold so the water truck will fit in the Space Shuttle landing bay, but under ordinary use it is fixed. The guidance package mass includes radiation shielding. In addition, the guidance package is on the water truck's nose, to get as far as possible away from the reactor. The thrust structure and feed lines support the tank and anchor the reactor. The 25% growth factor is to accommodate future design changes without having to re-design the rest of the spacecraft. The reaction control nozzles perform thrust vector control. They take up more mass than a gimbaled engine, but by the same token they are not a maintenance nightmare and additional point of failure.
The reactor supplies about 120 kilowatts to the tank in order to prevent the water from freezing. The reactor mass is 50% more than minimum. The lift-off burn is about 20 minutes durationa and consumes 0.7 kg of Uranium 235.
|Specific Power||31 W/kg|
|Propulsion||Solid core NTR|
|Specific Impulse||190 s|
|Exhaust Velocity||1,860 m/s|
|Wet Mass||299,030,000 kg|
|Water tank mass||25,000 kg|
|Sans Payload Mass||148,000 kg|
|Payload mass||50,000,000 kg|
|Dry Mass||50,148,000 kg|
|ΔV|| 802 m/s|
 1280 m/s
 752 m/s
|Mass Flow||[1,2] 903 kg/s|
 2,684 kg/s
|Thrust||[1,2] 1,680 kiloNewtons|
[1,2] 4,990 kiloNewtons
|Nozzle Power||[1,2] 4.9 gigawatts|
 1.6 gigawatts
|Engine Power||[1,2] 12.1 gigawatts|
 4.1 gigawatts
|Initial Acceleration|| 0.0006 g|
 0.0009 g
 0.005 g
The Water Ship is a robot propellant tanker design by Anthony Zuppero. Its mission is to deliver 50,000 metric tons of valuable water from the Martian moon Deimos to orbital propellant depots in Low Earth Orbit (LEO) cheaply and repeatably. It is not much more than a huge water bladder perched on a NERVA rocket engine. It might have integral water mining equipment as does the Kuck Mosquito, or it might depend upon a seperate Deimos ice mine.
Mass of water bladder is 25 metric tons (rated for no more than 0.005 g). Mass of nuclear thermal rocket plus strutural mass is 123 metric tons (struture includes computers, navigation equipment, and everything else). Mass without payload is 25 + 123 = 148 metric tons. Payload is 50,000 metric tons of water. Dry mass is 148 + 50,000 = 50,148 metric tons. Propellant mass is 248,882 metric tons. Wet mass is 50,148 + 248,882 = 299,030 metric tons.
At Deimos, only about 4.55 megawatts will be needed to melt 299,000 metric tons of ice into water (50,000 tons for payload + 249,000 tons for propellant). The engine nuclear reactor can supply that with no problem. The water must be distilled, because mud or dissolved salts will do serious damage to the engine nuclear reactor. By "serious damage" I mean things like clogging the heat-exchanger channels to cause a reactor meltdown, or impure steam eroding the reactor element cladding resulting in live radioactive Uranium 235 spraying in the exhaust plume.
Nuclear thermal rocket was designed to be a very conservative 100 megawatts per ton of engine. Engine will have a peak power of 12,142 Megawatts (for stage  and ). This works out to a modest engine temperature of 800° Celsius, and a pathetic but reliable specific impulse of 190 seconds. A NERVA could probably handle 300 megawatts per ton of engine, but the designer wanted to err on the side of caution. This will require much more water propellant, but there is no lack of water at Deimos.
This design uses a nuclear thermal rocket using water as propellant (a nuclear-heated steam rocket or NSR) instead of liquid hydrogen). This limits it to a specific impulse below 200 seconds which is pretty weak. However, numerous authors have shown that a NSR could deliver 10 and 100 times more payload per launched hardware than a H2-O2 chemical rocket or a NTR using liquid hydrogen. This is despite the fact that the chemical and NTR have much higher specific impulses. NSR work best when  the reactor can only be low energy,  there are abundant and cheap supplies of water propellant, and  mission delta-Vs are below 6,500 m/s.
It is true that electrolyzing the water into hydrogen and oxygen then burning it in a chemical rocket will get you a much better specific impulse of 450 seconds. But then you need the energy to electrolyze the water, and equipment to handle cryogenic liquids. These are just more things to go wrong.
In the table, , , and  refer to different segments of the journey from Deimos to LEO.
-  Start at Deimos. 497 m/s burn into Highly Eccentric Mars Orbit (HEMO). At apoapsis, 305 m/s burn into Low Mars Orbit (LMO)
-  At LMO periapsis, 1,280 m/s burn using the Oberth Effect to inject the water ship into Mars-Earth Hohman transfer orbit
-  270 days later at LEO periapsis, 752 m/s burn using the Oberth Effect to capture the water ship into Highly HEEO
- [x] Water ship does several aerobrakes until it reaches an orbital propellant depot in LEO
Total thrust time is about 10 hours.
Water ship's propellant has 15,137 metric tons extra as a safety margin. When it arrives, hopefully some of this will be available. It will take 322 metric tons of propellant for the empty water ship to travel from HEEO to Deimos, or 1,992 metric tons to travel from LEO to Deimos. Plus 0.139 gigawatts of engine power and 10 hours of thrust time.
Traveling from Deimos to LEO will consume about 12.7 kg of Uranium 235. Given the fact that Hohmann launch windows from Mars to Earth only occur every two years, the fuel in the engine nuclear reactor will probably last the better part of a century before it has to be replaced. The engine will be obsolete long before then.
For more details, refer to the original article.
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.
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.
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.
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 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.
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.
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.
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.
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:
AUX ENG ROOM
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.)
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:
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.
- Deck Number
- Frame Number
- Position in relation to centerline of ship
- Compartment use
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:
CG/DD/DDG/FFG 12IN Cutters 1FT LPD 2FT CVN/LSD 4FT LHD/LHA 7FT
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.
On a naval vessel, "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.
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 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.
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. Also note that such automatic doors will contain complicated components and thus require lots of regular maintenance.
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.
- 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
- 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
- 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.
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.
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.
"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.
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.
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.
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 left diagram below, the white area is safe, and the blue area 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.
This does throw a monkey wrench into Traveller's definition of "Port", but that's just too bad.
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.
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.
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"
- Emergency navigational astrodomes
- Docking (rendezvous) windows
- Airlock doors
- Landing windows
- Cockpit windows for shuttles that fly like aircraft when they land
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 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.
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.
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.
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:
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.
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 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.
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.
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?