Atomic Rockets

Design

SF author Ken MacLeod said that the specification of a human being is "a space suit for a fish." For a list of the parameters for a NASA spec space suit, go here.

Current NASA space suits have their drawbacks. They take forever to put on, they fight your every movement, and if you tear it you die hideously in about 90 seconds.

The only thing that allows an astronaut to bend their limbs at all is the magic of constant volume joints. These are why most pictures of space suits look like the Michelin Man (i.e., like a stack of donuts).

Taking a typical over-engineering approach, NASA has been looking into armored suits. These suits try to fix the tearing problem at the expense of making the first two problems much worse. True, hard suits do solve the depressurization problem, but at such a cost.

Gloves

The gloves are especially a problem. Back in the 1950's it was unclear if space suit gloves were even possible. You need to make the various protective layers thin enough to be able to fit between adjacent fingers. And with miniature constant volume cuffs at each finger joint. Some suit designers took a tip from deep sea diving suits and postulated mechanical pincers instead of gloves.

But as we know NASA did manage to design actual space suit gloves. However, they do not work very well. Almost every single NASA astronaut who has performed EVA has complaints about the difficulty of doing any fine work while wearing those gloves.

If you're headed for space, you might rethink that manicure: Astronauts with wider hands are more likely to have their fingernails fall off after working or training in space suit gloves, according to a new study.

In fact, fingernail trauma and other hand injuries—no matter your hand size—are collectively the number one nuisance for spacewalkers, said study co-author Dava Newman, a professor of aeronautics and astronautics at the Massachusetts Institute of Technology.

"The glove in general is just absolutely one of the main engineering challenges," Newman said. "After all, you have almost as many degrees of freedom in your hand as in the rest of your whole body."

The trouble is that the gloves, like the entire space suit, need to simulate the pressure of Earth's atmosphere in the chilly, airless environment of space. The rigid, balloonlike nature of gas-pressurized gloves makes fine motor control a challenge during extravehicular activities (EVAs), aka spacewalks.

A previous study of astronaut injuries sustained during spacewalks had found that about 47 percent of 352 reported symptoms between 2002 and 2004 were hand related. More than half of these hand injuries were due to fingertips and nails making contact with the hard "thimbles" inside the glove fingertips.

In several cases, sustained pressure on the fingertips during EVAs caused intense pain and led to the astronauts' nails detaching from their nailbeds, a condition called fingernail delamination.

While this condition doesn't prevent astronauts from getting their work done, it can become a nuisance if the loose nails gets snagged inside the glove. Also, moisture inside the glove can lead to secondary bacterial or yeast infections in the exposed nailbeds, the study authors say.

If the nail falls off completely, it will eventually grow back, although it might be deformed.

For now, the only solutions are to apply protective dressings, keep nails trimmed short—or do some extreme preventative maintenance.

"I have heard of a couple people who've removed their fingernails in advance of an EVA," Newman said.

From Astronauts' Fingernails Falling Off Due to Glove Design by National Geographic News (2010).

Skin Suits

An innovative alternative approach is the Mechanical Counter Pressure (MCP) Suit. Instead of trying to hold your body intact with air pressure, it holds it in with spandex. It sounds crazy but it just might be crazy enough to work.

A skin-tight suit of high tech cloth exerts pressure over the rocketeer's body to provide pressure. A bubble helmet with oxygen supply allows one to breathe. Open pores in the suit actually allow the body to be cooled by perspiration. Tears will cause bruising to the skin, but are not as lethal as they are on a conventional suit. The suit can be quickly put on. They do not interfere as much with movement (+20% energy expenditure, compared with +400% for a NASA suit). And you can store them by folding them up and putting them inside the bubble helmet.

They do need some care in design, though. Any concave areas on the body that the suit does not hug will bulge out under internal body pressure until it fills the void (i.e., your armpits will become armhills). Putty or fluid filled bladders will be needed to prevent this. Care must be taken around those nether regions, the small of the back, and in certain locations of the female chest.

And upon entering vacuum, one will have an instant attack of dire flatulence. Don't be polite, let it out right away or you may damage your intestines.

The pressure suit went on like a diver's wet suit, and looked like one only not so thick. It fit very closely; he had to use talcum power to get into it. Gloves dogged onto the ends of the sleeves, and a seal set firmly around his neck. He slipped into the boots, hung the small equipment bag over his shoulder, and reported back to the technicians.

They pulled and pinched, looking for loose spots. They didn't find any in Kevin's, but the next to come up was the girl he'd seen before, and after a moment they handed her a lump of what looked like clay. "Shove that under your breasts," the technician said. "Yeah, right there. Don't leave any gaps."

"But - " She was obviously embarrassed.

"Lady, you're going into vacuum," the man explained. "Your innards will be pressurized to about seven pounds by the air in your helmet. Outside is nothing. Your skin won't hold that. The suit will, but you've got to be flat against the suit, otherwise you'll swell up to fit any empty spaces. It won't do a lot of good for your figure."

"Oh. Thank you," she said. She turned away and used the clay as she'd been told.

From Exiles To Glory by Jerry Pournelle (1977).

Seam Tube

There may be a length of tubing added along the seams of the arms, legs, and torso. The suit will be relaxed for easy dressing, then the tubing will be pressurized to put tension on the fabric (This was used in the g-suits worn by early jet pilots). The tubing will automatically pressurize when the helmet is put on and pressured up. A more advanced design uses a strip of "shape metal alloy'. An applied voltage can toggle the metal strip between expanded and contracted.

There is some discussion of space suit design here.

Armor

In The Millennial Project Savage suggests that light tungsten armor plates be worn over the suit to give some anti-radiation protection (this would only be needed in high radiation areas, like the Van Allen belts). A minimal version of the suit can be developed for everyday wear inside a spacecraft. In cases of emergency air pressure loss, all you'd need is an oxygen mask and earplugs to survive for hours (This was used in Jerry Pournelle's "Tinker". The suit was worn like long johns under a coverall. The coverall is due to the fact that the suit is about as modest as wearing a coat of paint.). If you want to go to extremes, a full MPC suit could carry six litres of Spirulina culture with support equipment, creating a closed life support system.

Helmet

The helmet will have an outer layer of five millimeters of high density lead crystal. Inside will be two layers of dense borosilicate glass sandwiched between two layers of Lexan. The middle layer of Lexan will add strength and prevent shattering, the inner will act as a reserve helmet. The outer surface will be gold anodized to block glare, ultraviolet, and infra-red. There may be a nested set of telescoping curved armor plates that can be deployed for further protection.

Some SF novels have a space helmets equipped with a tiny airlock near the mouth, called a "chow-lock." It is used to allow the astronaut to eat and drink without venting the helmet's air to the vacuum of space. I am uncertain how practical this concept is, or how idiot proof it can be made.

The part of the suit that will cause designers the most headaches is the "neck dam". This goes around the neck, and tries to keep and air-tight seal. Otherwise the helmet shoots off like a champagne cork and all the air in the helmet will spray out. I personally would be in favor of straps that go from the neck dam and loop around ones arm around the armpits, but I'm no expert.

It also has to be comfortable to wear, and help in controlling the humidity inside the helmet (so it doesn't fog up). Another important part is the radio communication unit (see below), since the lack of air in space prevents the sound of your voice from reaching anybody. The old tagline to the first ALIEN movie was "In Space No One Can Hear You Scream". Other items might include windshield wipers (inside for condensation, outside for dust), a build-in set of binoculars, headlights for shadowed areas, and a mirrored sun-visor to prevent sunlight from burning out your retinas.

"Planetary suits" are used when there is an atmosphere, but it isn't breathable. They have a slightly different design from space suits.

Life Support Balls

It will also be useful to supplement one's supply of space suits with emergency life support balls. These are basically bare essential spherical suits with no arms, legs, or heads for use by people who are injured or untrained in suit operations. When a passenger liner has a problem, the crew members will stuff the passengers into these balls, zip them up, and tow them to safety. In this case, one would be wise to use balls that cannot be opened from the inside. Passengers can do remarkably silly things at the worst possible moment. And even a person highly skilled in space suits can be a problem if they are unconscious and suffering from a broken arm. It will be much quicker to slip them into a ball instead of trying to suit them up.

Going Outside

Buddy System

While wearing a space suit in vacuum, the iron-clad rule is The Buddy System. There are many mishaps that are trivial if you have a companion but fatal if you don't. Imagine that your suit springs a slow leak on your back just where you can't reach it with a repair patch. Oops.

In cases of emergency, two space suited people can "cross-connect" their oxygen supplies. This is generally done when one of them runs out of breathable gas, the other shares their oxygen until they get to shelter.

Safety Line

For strict safely, static lines or safety lines are mandatory. The spacecraft should have plenty of small steel rings bolted at regular intervals over the hull for spacemen to attach their safety lines to. Without a static line, a spaceman who manages to get both magnetic boots separated from the hull will suddenly find themself on a slow impromptu tour of the solar system. If their widows are real lucky the bodies might actually be recovered for burial.

Another useful item is a "line throwing gun". This allows one to shoot a safety line from one spacecraft to another. The line will have to be made of special materials, since most terrestrial ropes and cables will turn glass-like and shatter in vacuum.

Things get real nasty if the ship is a tumbling pigeon or otherwise rotates to provide artificial gravity. The poor EVA spacemen have to swing from hand-hold to hand-hold like trapezes artists. From their viewpoint, the spacecraft is overhead and below is a long fall to infinity. For details read Heinlein's short story "Ordeal in Space".

"Beeper"

They may also need a "beeper". This is a low powered radar the size and shape of flashlight, used to locate small objects nearby (like that zero-recoil wrench you let go of "just for a minute"). You wave it around until is starts beeping (heard over your suit radio). As you approach the object the beep rate increases.

Radio

Astronauts also have to watch what they say. There is no air in space, so unless you are touching helmets together, you cannot talk with others without a radio. But while speaking on Terra means your voice becomes fainter with distance, over a radio it will be loud and clear out to the limit of the radio's range. This means cursing under your breath or muttering behind somebody's back will not work. There might be several channels to allow a bit of privacy, or if several conversations are going on at once.

Some SF novels suggest that for privacy, two space suited people might turn off their raidos, and touch helmets. The theory is that the sound of the conversation will be conducted through the contact between helmets. However, others maintain that the area of contact will be so small (since the helmets are basically spherical) that no audible sound will manage to pass. In Poul Anderson's TAU ZERO, he says that instead astronauts will learn how to read lips.

Lindgren and Reymont exchanged a look above his bent back. She shaped unspoken words. Once he had taught her the Rescue Corps trick of lip reading when spacesuit radios were unusable. They had practiced it as something that made them more private and more one.

From TAU ZERO by Poul Anderson (1970)

Sticky Boots

Many SF novels have magnetized space boots to allow the rocketeers to adhere to the hull, but magnets do not work very well on hulls composed of titanium, aluminum, or magnesium. If one does have a ferromagnetic hull, it might be best to have magnets just in the boot toes but not the heels, to facilitate walking. These might be used inside the spacecraft's lifesystem, if you think those velcro footies used by the stewardess in 2001 are just too unmanly for words.

Visual Identification

Once people are suited up, it does become hard to tell who is who. In Destination Moon, there were four spacemen, and each had a uniquely colored suit. Kind of like colored tooth-brushes. But this won't work if you have more than a few spacemen, er, spacepeople. The person's name stenciled in large letter across the front and back is a possibility.

In Piers Anthony's The Kirlian Quest, he notes that this problem has occurred before: knights in armor are similarly anonymous. The solution is coat of arms and heraldry. When a proposed heraldic "device" (coat of arms) is submitted to the college of heralds, it is compared with all existing devices. The new device must have at least one major and one minor point of visual difference from those already registered. Otherwise it would be too easy to confuse the two devices in the heat of battle. Mistaking a foe for a friend could be fatal.

In Larry Niven's Protector, the Belters of the asteroid belt spend most of their lives inside their space suit. They have a tendency to paint their suits in extravagant colors. One of the characters had Salvador Dali's Madonna of Port Lligat on the front of their suit. In an interesting psychological quirk, Belters also tend to be nudists when in a pressurized environment.

Most Belters decorated their suits. Why not? The interior of his suit was the only place many a Belter could call home, and the one possession he had to keep in perfect condition. But even in the Belt, Nick Sohl's suit was unique.

On an orange background was the painting of a girl. She was short; her head barely reached Nick's neck ring. Her skin was a softly glowing green. Only her lovely back showed across the front of the suit. Her hair was streaming bonfire flames, flickering orange with touches of yellow and white, darkening into red-black smoke as it swept across the girl's left shoulder. She was nude. Her arms were wrapped around the suit's torso, her hands touching the air pac on its back; her legs embraced the suit's thighs, so that her heels touched the backs of the flexible metal knee joints. It was a very beautiful painting, so beautiful that it almost wasn't vulgar. A pity the suit's sanitary outlet wasn't somewhere else.

From PROTECTOR by Larry Niven. 1973

The tiger stripes on Jim's mask, the war paint on Frank's, and a rainbow motif on Phyllis's made the young people easy to identify. The adults could be told apart only by size, shape, and manner; there were two extras, Doctor MacRae and Father Cleary.


He poked his head inside, seemed about to leave, then came inside. He pointed to their outdoor suits, hanging on hooks by the clothes locker. 'Why haven't you removed those barbaric decorations from your masks?'

The boys looked startled; Howe went on, 'Haven't you looked at the bulletin board this morning?'

NOTICE TO STUDENTS

1. The practice of painting respirator masks with so-called identification patterns will cease. Masks will be plain and each student will letter his name neatly in letters one inch high across the chest and across the shoulders of his outdoors suit.

(ed note: headmaster Howe is a stupid little power-mad bureaucrat who does not understand the realities of life out on the frontier)

From RED PLANET by Robert Heinlein. 1949

Suit into Ship

As one adds more gadgets and attachments to a space suit, it gradually morphs into a tiny spaceship. It starts with spring-loaded broomsticks and picks up speed with the addition of tiny attitude jets and maneuvering rockets. As a parallel development, a rocket engine with a skeletal frame to hold astronauts is the first "space taxi". When a space suit is massive enough that one climbs into it instead of putting it on like clothing, equipped with mechanical arms and waldoes, you suddenly have a space pod. Then if the pod grows to the size of a baby spaceship, but with massive over-sized engines, you finally have a space tug.

"Broomstick"

A broomstick is a spring loaded gizmo used by astronauts to launch themselves from place to place, and to bring themselves to a stop upon arrival.

... This was where the broomsticks came in.

Commander Doyle had invented them, and the name, of course, came from the old idea that once upon a time witches used to ride on broomsticks. We certainly rode around the station on ours. They consisted of one hollow tube, sliding inside another. The two were connected by a powerful spring, one tube ending in a hook, the other in a wide rubber pad. That was all there was to it. If you wanted to move, you put the pad against the nearest wall and shoved. The recoil launched you into space, and when you arrived at your destination you let the spring absorb your velocity and bring you to rest. Trying to stop yourself with your bare hands was liable to result in sprained wrists.

It wasn't quite as easy as it sounds, though, for if you weren't careful you could bounce right back the way you'd come.

From Islands in the Sky by Arthur C. Clarke, 1952.

There are some professions which have evolved unique and characteristic tools - the longshoreman's hook, the potter's wheel, the bricklayer's trowel, the geologist's hammer. The men who had to spend much of their time on zero-gravity construction projects had developed the broomstick.

It was very simple - a hollow tube just a metre long, with a footpad at one end and a retaining loop at the other. At the touch of a button, it could telescope out to five or six times its normal length, and the internal shock-absorbing system allowed a skilled operator to perform the most amazing manoeuvres. The footpad could also become a claw or hook if necessary; there were many other refinements, but that was the basic design. It looked deceptively easy to use; it wasn't.

. . .

Everything happened in about five seconds. Brailovsky triggered his broomstick, so that it telescoped out to its full length of four metres and made contact with the approaching ship. The broomstick started to collapse, its internal spring absorbing Brailovsky's considerable momentum; but it did not, as Curnow had fully expected, bring him to rest beside the antenna mount. It immediately expanded again, reversing the Russian's velocity so that he was, in effect, reflected away from Discovery just as rapidly as he had approached. He flashed past Curnow, heading out into space again, only a few centimetres away. The startled American just had time to glimpse a large grin before Brailovsky shot past him.

A second later, there was a jerk on the line connecting them, and a quick surge of deceleration as they shared momentum. Their opposing velocities had been neatly cancelled; they were virtually at rest with respect to Discovery. Curnow had merely to reach out to the nearest handhold, and drag them both in.

From 2010: Odyssey Two by Arthur C. Clarke, 1982.

Rocket Pack

While engaging in extra-vehicular activity, our space-suited rocketeers may use a "broomstick", or some kind of small jets (a Manned Maneuvering Unit or MMU). NASA has also developed a nitrogen-gas propelled unit that fits on the backpack, called the Simplified Aid for Extravehicular Activity Rescue (SAFER). The SAFER can help an astronaut return to the shuttle or station in the event that they gets separated from the spacecraft. SAFER has a deltaV capacity of 3 m/s.

"The trick to jetting yourself in space,"—he went on, 'lies in balancing your body on the jet—the thrust has to pass through your center of gravity. If you miss and don't correct it quickly, you start to spin, waste your fuel, and have the devil's own time stopping your spin. "It's no harder than balancing a walking stick on your finger—but the first time you try it, it seems hard.

"Rig out your sight." He touched a stud at his belt; a light metal gadget snapped up in front of his helmet so that a small metal ring was about a yard in front of his face. "Pick out a bright star, or a target of any sort, lined up in the direction you want to go. Then take the ready position— no, no! Not yet—I'll take it."

He squatted down, lifted himself on his hands, and very cautiously broke his boots loose from the side, then steadied himself on a cadet within reach. He turned and stretched out, so that he floated with his back to the ship, arms and legs extended. His rocket jet stuck straight back at the ship from the small of his back; his sight stuck out from his helmet in the opposite direction.

He went on, "Have the firing switch ready in your right hand. Now, have you fellows ever seen a pair of adagio dancers? You know what I mean—a man wears a piece of leopard skin and a girl wearing less than that and they go leaping around the stage, with him catching her?"

Several voices answered yes. Hanako continued, "Then you know what I'm talking about. There's one stunt they always do—the girl jumps and the man pushes her up and balances her overhead on one hand. He has his hand at the small of her back and she lays there, artistic-like. "That's exactly the way you got to ride a jet. The push comes at the small of your back and you balance on it. Only you have to do the balancing—if the push doesn't pass exactly through your center of gravity, you'll start to turn. You can see yourself starting to turn by watching through your sight. "You have to correct it before it gets away from you. You do this by shifting your center of gravity. Drag in the arm or leg on the side toward which you've started to turn. The trick is—"

"Just a second, Sarge," someone cut in, "you said that just backwards. You mean; haul in the arm or leg on the other side, don't you?"

"Who's talking?"

"Lathrop, number six. Sorry."

"I meant what I said, Mr. Lathrop."

"But—"

"Go ahead, do it your way. The rest of the class will do it my way. Let's not waste time. Any questions? Okay, stand clear of my jet."

The half circle backed away until stopped by the anchored static lines. A bright orange flame burst from the sergeant's back and he moved straight out or "up," slowly at first, then with increasing speed. His microphone was open; Matt could hear, by radio only, the muted rush of his jet-and could hear the sergeant counting seconds: "And . . . one! . . . and . . . two! . . . and . . . three!" With the count of ten, the jet and the counting stopped.

Their instructor was fifty feet "above" them and moving away, back toward them. He continued to lecture. "No matter how perfectly you've balanced you'll end up with a small amount of spin. When you want to change direction, double up in a ball—" He did so. "—to spin faster—and snap out of it when you've turned as far as you want." He suddenly flattened out and was facing them. "Cut in your jet and balance on it to straighten out on your new course—before you drift past the direction you want."

He did not cut in his jet, but continued to talk, while moving away from them and slowly turning. "There is always some way to squirm around on your axis of rotation so that you can face the way you need to face for a split second at least. For example, if I wanted to head toward the Station—" Terra Station was almost a right angle away from his course; he went through contortions appropriate to a monkey dying in convulsions and again snapped out in starfish spread, facing the Station—but turning slow cartwheels now, his axis of rotation unchanged.

"But I don't want to go to the Station; I want to come back to the ship." The monkey died again; when the convulsions ceased, the sergeant was facing them. He cut in his jet and again counted ten seconds. He hung in space, motionless with respect to the ship and his class and about a quarter mile away. "I'm coming in on a jet landing, to save time." The jet blasted for twenty seconds and died; he moved toward them rapidly.

When he was still a couple of hundred feet away, he flipped over and blasted away from the ship for ten seconds. The sum of his maneuvers was to leave him fifty feet away and approaching at ten feet per second. He curled up in a ball again and came out of it feet toward the ship.

Five seconds later his boots clicked to steel and he let himself collapse without rebound. "But that is not the way you'll do it," he went on. "My tanks hold more juice than yours do—you've got fifty seconds of power, with each second good for a change of speed on one foot-second—that's for three hundred pounds of mass; some of you skinny guys will go a little faster.

"Here's your flight plan: ten seconds out, counted. Turn as quick as you can and blast fifteen seconds back. That means you'll click on with five foot-seconds. Even your crippled grandmother ought to be able to do that without bouncing off. Lathrop! Unhook—-you're first."

As the cadet came up, Hanako anchored himself to the ship with two short lines and took from his belt a very long line. He snapped one end to a hook in the front of the cadet's belt and the other to his own suit. The student looked at it with distaste. "Is the sky hook necessary?"

Sergeant Hanako stared at him. "Sorry, Commodore—regulations. And shut up. Take the ready position."

Silently the cadet crouched, then he was moving away, a fiery brush growing out of his back. He moved fairly straight at first, then started to turn.

He pulled in a leg—and turned completely over.

"Lathrop—cut off your jet!" snapped Hanako. The flame died out, but the figure in the suit continued to turn and to recede. Hanako paid out his safety line. "Got a big fish here, boys," he said cheerfully. "What do you think he'll weigh?" He tugged on the line, which caused Lathrop to spin the other way, as the line had wound itself around him. When the line was free he hauled the cadet in.

Lathrop clicked on. "You were right, sergeant. I want to try it again—your way."

"Sorry. The book says a hundred per cent reserve fuel for this drill; you'd have to recharge." Hanako hesitated. "Sign up for tomorrow morning—I'll take you as an extra."

"Oh—thanks, Sarge!"

"Don't mention it. Number one!"

From Space Cadet by Robert Heinlein. 1948

Legless

Many early designs of spacesuits for use in free fall were lacking legs. This simplifies the design. This gradually becomes a hard suit which allows an astronaut to work in a pressurized environment and so avoid the bends.

At this point, perhaps I should remind you that the suits we use on the station are completely different from the flexible affairs men wear when they want to walk around on the Moon. Ours are really baby space ships, just big enough to hold one man. They are stubby cylinders, about seven feet long, fitted with low-powered propulsion jets, and have a pair of accordion-like sleeves at the upper end for the operator's arms.

As soon as I'd settled down inside my very exclusive space craft, I switched on power and checked the gauges on the tiny instrument panel. All my needles were well in the safety zone, so I gave Tommy a wink for luck, lowered the transparent hemisphere over my head and sealed myself in. For a short trip like this, I did not bother to check the suit's internal lockers, which were used to carry food and special equipment for extended missions.

As the conveyor belt decanted me into the air lock, I felt like an Indian papoose being carried along on its mother's back. Then the pumps brought the pressure down to zero, the outer door opened, and the last traces of air swept me out into the stars, turning very slowly head over heels.

The station was only a dozen feet away, yet I was now an independent planet—a little world of my own. I was sealed up in a tiny, mobile cylinder, with a superb view of the entire universe, but I had practically no freedom of movement inside the suit. The padded seat and safety belts prevented me from turning around, though I could reach all the controls and lockers with my hands or feet.

In space the great enemy is the Sun, which can blast you to blindness in seconds. Very cautiously, I opened up the dark filters on the "night" side of my suit, and turned my head to look out at the stars. At the same time I switched the helmet's external sunshade to automatic, so that whichever way the suit gyrated my eyes would be shielded.

Presently, I found my target—a bright fleck of silver whose metallic glint distinguished it clearly from the surrounding stars. I stamped on the jet control pedal and felt the mild surge of acceleration as the low-powered rockets set me moving away from the station. After ten seconds of steady thrust, I cut off the drive. It would take me five minutes to coast the rest of the way, and not much longer to return with my salvage.

From The Haunted Space Suit by Arthur C. Clarke. 1958

Space Taxi

A space taxi is a short ranged orbit to orbit vehicle used to carry astronauts and small amounts of cargo. At its simplest, it is a frame that astronauts attach themselves to, with a rocket engine at one end. More complicated taxis have an enclosed hull which may or may not be pressurized. Do keep in mind that the direction of "down" will appear to be in the same direction the rocket exhaust shoots.

Orion Space Taxi
PropulsionChemical
Specific Impulse450 s
Exhaust Velocity4,500 m/s
Wet Mass1,584 kg
Dry Mass759 kg
Mass Ratio2.0
ΔV3,120 m/s
Payload136 kg (2 people)
Length3 m
Diameter1 m wide

In this document about Orion drive spacecraft, they mention a space taxi. It carries two crew members, has a hardware mass of 623 kilograms, and a propellant mass of 825 kilograms. As near as I can measure, it can be approximated as a cylinder with a height of two meters and a radius of 0.5 meters, with a hemisphere of radius 0.5 meters on each end.

This gives it an internal volume of 2 m3. Assuming it has chemical propulsion, the propellant would take up about 0.8 cubic meters, and the two crew would take up 0.14 cubic meters. Carrying two crew, it would have a mass ratio of about 2, and thus a deltaV of about 3,120 m/s.

This is an emergency lunar escape vehicle concept, in case an Apollo Lunar Module crashed upon landing. It was designed to be assembled from various parts canibalized from the wreck. Note that in the two-man version, the pilot gets an acceleration chair, but the poor second astronaut is slung under the chair by straps. You can read more about this here, here, and here (PDF files).

Matt pulled himself along, last in line, and found the scooter loaded. He could not find a place; the passenger racks were filled with space-suited cadets, busy strapping down.

The cadet pilot beckoned to him. Matt picked his way forward and touched helmets. "Mister," said the oldster, "can you read instruments?"

Guessing that he referred only to the simple instrument panel of a scooter, Matt answered, "Yes, sir."

"Then get in the co-pilot's chair. What's your mass?"

"Two eighty-seven, sir," Matt answered, giving the combined mass, in pounds, of himself and his suit with all its equipment. Matt strapped down, then looked around, trying to locate Tex and Oscar. He was feeling very important, even though a scooter requires a co-pilot about as much as a hog needs a spare tail.

The oldster entered Mart's mass on his center-of-gravity and moment-of-inertia chart, stared at it thoughtfully and said to Matt, "Tell Gee-three to swap places with Bee-two."

Matt switched on his walky-talky and gave the order. There was a scramble while a heavy-set youngster changed seats with a smaller cadet. The pilot gave a high sign to the cadet manning the hangar pocket; the scooter and its launching cradle swung out of the pocket, pushed by power-driven lazy tongs.

A scooter is a passenger rocket reduced to its simplest terms and has been described as a hat rack with an outboard motor. It operates only in empty space and does not have to be streamlined.

The rocket motor is unenclosed. Around it is a tier of light metal supports, the passenger rack. There is no "ship" in the sense of a hull, airtight compartments, etc. The passengers just belt themselves to the rack and let the rocket motor scoot them along.

From SPACE CADET by Robert Heinlein. 1948

Space Pod

A space pod is a small pressurized vehicle with one or more waldoes or mechanical arms. They are often used for space construction and maintenance. In the movie 2001 A Space Odyssey, they were referred to as "EVA pods." In Wernher von Braun and Disney's Man In Space series, they were called "bottle suits." They are also known as "closed-cabin cherry picker", "manned autonomous work system", and the ever popular "man-in-a-can." One of their main advantages over a soft space suit is that they solve the depressurization problem.

I'm back to trying to put together some semi-realistic design for near-future space flight. In this case, I'm mainly trying to tackle a couple of problems. The first is the restrictions put on by current EVA technology. There's no such thing as being able to put on your spacesuit, go out the airlock and deal with an emergency these days. A minimum of about 20 hours of slow decompression and prebreathing pure oxygen is required before anyone goes out into space. Thats because the cabin environment of the Space Station, and the Shuttle is oxygen/nitrogen at sea level pressure, while the suits operate with pure oxygen at 5 p.s.i. They do that because, with present, vintage 1980 space suits, the arms and legs become impossible to bend if the pressure is any greater. The other problem is radiation shielding. For long stays outside, or any meaningful work beyond the Earth's ionosphere, the present suits just have inadequate radiation protection.

The potential solution is MAWS. It will have the same internal pressure as the station, or whatever long duration habitat we have in the future, because it doesn't have flexible joints. Instead it uses a couple of miniature versions of the station's robot arm. Its possible to put much better radiation shielding around MAWS, too. Probably the first exploration of asteroids or moons of Mars will be done in something like this design.

So this is the baseline look of the MAWS, as loosely worked out by NASA. Should it have a second set of heavier arms? Where would EVA equipment be attached? In general, what do you think of the idea?

From Manned Autonomous Work System by Tom Peters (2010)

Discovery's extravehicular capsules or "space pods" were spheres about nine feet in diameter, and the operator sat behind a bay window which gave him a splendid view. The main rocket drive produced an acceleration of one-fifth of a gravity—just sufficient to hover on the Moon—while small attitude-control nozzles allowed for steering. From an area immediately beneath the bay window sprouted two sets of articulated metal arms or "waldoes," one for heavy duty, the other for delicate manipulation. There was also an extensible turret carrying a variety of power tools, such as screwdrivers, jack-hammers, saws, and drills. Space pods were not the most elegant means of transport devised by man, but they were absolutely essential for construction and maintenance work in vacuum. They were usually christened with feminine names, perhaps in recognition of the fact that their personalities were sometimes slightly unpredictable. Discovery's trio were Anna, Betty, and Clara.

Once he had put on his personal pressure suit—his last line of defense—and climbed inside the pod, Poole spent ten minutes carefully checking the controls. He burped the steering jets, flexed the waldoes, reconfirmed oxygen, fuel, power reserve.

From 2001 A Space Odyssey by Sir Arthur C. Clarke (1969)

He was nearer to the sun than any man had ever been. His damaged space-pod was lying on no hill, but on the steeply curving surface of a world only two miles in diameter.


Even then, it was still possible for men in the tiny self-propelled space-pods — miniature spaceships, only ten feet long — to work on the night side for an hour or so, as long as they were not overtaken by the advancing line of sunrise.


He was still not quite sure what had happened. He had been replacing a seismograph transmitter at Station 145, unofficially known as Mount Everest because it was a full ninety feet above the surrounding territory. The job had been a perfectly straightforward one, even though he had to do it by remote control through the mechanical arms of his pod. Sherrard was an expert at manipulating these; he could tie knots with his metal fingers almost as quickly as with his flesh-and-bone ones.


He had aimed the pod with its gyros, set the rear jets at Strength Two, and pressed the firing button. There had been a violent explosion somewhere in the vicinity of his feet and he had soared away from Icarus—but not toward the ship. Something was horribly wrong; he was tossed to one side of the vehicle, unable to reach the controls. Only one of the jets was firing, and he was pinwheeling across the sky, spinning faster and faster under the off-balanced drive. He tried to find the cutoff, but the spin had completely disorientated aim. When he was able to locate the controls, his first reaction made matters worse—he pushed the throttle over to full, like a nervous driver stepping on the accelerator instead of the brake. It took only a second to correct the mistake and kill the jet, but by then he was spinning so rapidly that the stars were wheeling round in circles.

Everything had happened so quickly that there was no time for fear, no time even to call the ship and report what was happening. He took his hands away from the controls; to touch them now would only make matters worse. It would take two or three minutes of cautious jockeying to unravel his spin, and from the flickering glimpses of the approaching rocks it was obvious that he did not have as many seconds. Sherrard remembered a piece of advice at the front of the Spaceman’s Manual: "When you don’t know what to do, do nothing." He was still doing it when Icarus fell upon him, and the stars went out.

It had been a miracle that the pod was unbroken, and that he was not breathing space. (Thirty minutes from now he might be glad to do so, when the capsule’s heat insulation began to fail… .) There had been some damage, of course. The rear-view mirrors, just outside the dome of transparent plastic that enclosed his head, were both snapped off, so that he could no longer see what lay behind him without twisting his neck. This was a trivial mishap; far more serious was the fact that his radio antennas had been torn away by the impact. He could not call the ship, and the ship could not call him. All that came over the radio was a faint crackling, probably produced inside the set itself. He was absolutely alone, cut off from the rest of the human race.

It was a desperate situation, but there was one faint ray of hope. He was not, after all, completely helpless. Even if he could not use the pod’s rockets—he guessed that the starboard motor had blown back and ruptured a fuel line; something the designers said was impossible—he was still able to move. He had his arms.


He slipped his fingers into the controls that worked his mechanical limbs. Outside the pod, in the hostile vacuum that surrounded him, his substitute arms came to life. They reached down, thrust against the iron surface of the asteroid, and levered the pod from the ground. Sherrard flexed them, and the capsule jerked forward, like some weird, two-legged insect… first the right arm, then the left, then the right… .

It was less difficult than he had feared, and for the first time he felt his confidence return. Though his mechanical arms had been designed for light precision work, it needed very little pull to set the capsule moving in this weightless environment. The gravity of Icarus was ten thousand times weaker than Earth’s: Sherrard and his space-pod weighed less than an ounce here, and once he had set himself in motion he floated forward with an effortless, dreamlike ease.

Yet that very effortlessness had its dangers. He had traveled several hundred yards, and was rapidly overhauling the sinking star of the Prometheus, when overconfidence betrayed him.

From "Summertime on Icarus" by Sir Arthur C. Clarke (1960)

Space Tug

A space tug is a tiny spacecraft with over-sized engines and some means of grappling another spacecraft. If the tug pushes its cargo,it will have a massive push plate on its bow, with a core of structural members to transmit the thrust of its engines to the push plate. If the tug pulls its cargo, it will have cables and winches on its stern, and the engines will be vectored to fire backwards at an angle so it does not torch the ship it is dragging. The engines will suffer a reduction thrust penality proportional to the cosine of the engine angle.

Note that if nuclear propulsion spacecraft are involved, the tugs and the spacecraft will generally be designed to dock bow to bow. Otherwise you will be exposing the other ship to the radiation from your engine.

According to the Technovelgy site, the term "space tug" was invented in 1942 by Eric Frank Russell in his short story "Describe a Circle"

NASA Space Tug concept (1970's)

Tinsley Space Tug concept

Space tug concept by Frank Tinsley. Tug has grapples and grippers on its stern. The four square plates around its waist are ion drive units (The crewman's hatch is unfortunately placed right in the line of fire of one of the ion drives).

The petals near the bow are heat radiators. Sadly the radiators are spaced too closely. In reality one would want two radiators at 180° or at the most four radiators at 90°. The arrangement shown would have the heat from one radiator impinging on its neighbors.

And at the tip of the pointed prow would be the tiny nuclear reactor. It would be nice to include a small shadow shield to protect the crew from nuclear radiation.

Lockheed Space Tug concept (1963)

Details are sparse on this design. Click on blueprints for larger image. Blueprint is written in Italian but it has been translated for the website by Alberto Bursi. The engines are around the waist, on swivels. The designers also appear to have a flippant attitude towards maintaining a sense of up and down. If the pilot turns his head he will see his copilot's feet.

Boeing Intra-Orbit Personnel/Cargo Tug concept (1981)

The diagram is from this PDF file. Annoyingly it included lots of facts and figures about the tug, then said and here is a diagram of a totally unrelated Boeing concept that we will not give you any data for.

Assorted

Safety Check

On Earth, Andrew Lear's habits would have been no more than a character trait. In a hurry, he might choose mismatched socks. He might put off using the dishwasher for a day or two if he were involved in something interesting. He would prefer a house that looked "lived in." God help the maid who tried to clean up his study. He'd never be able to find anything afterward.

He was a brilliant but one-sided man. Backpacking or skin diving might have changed his habits -- in such pursuits you learn not to forget any least trivial thing -- but they would never have tempted him. An expedition to Mars was something he simply could not turn down. A pity, because neatness is worth your life in space.

You don't leave your fly open in a pressure suit.

A month after the landing, Childrey caught Lear doing just that.

The "fly" on a pressure suit is a soft rubber tube over your male member. It leads to a bladder, and there's a spring clamp on it. You open the clamp to use it. Then you close the clamp and open an outside spigot to evacuate the bladder into vacuum.

Similar designs for women involve a catheter, which is hideously uncomfortable. I presume the designers will keep trying. It seems wrong to bar half the human race from our ultimate destiny.

Lear was addicted to long walks. He was coming back from a walk, and he met Childrey coming out. Childrey noticed that the waste spigot on Lear's suit was open, the spring broken. Lear had been out for hours. If he'd had to go, he might have bled to death through flesh ruptured by vacuum.

From "The Hole Man" by Larry Niven. 1974
Men on the Moon ed. by Donald A. Wollheim, 1958

The instructor ordered his group to "Suit upl" without preliminary, as it was assumed that they had studied the instruction spool.

The last of the ship's spin had been removed some days before. Matt curled himself into a ball, floating free, and spread open the front of his suit. It was an unhandy process; he found shortly that he was trying to get both legs down one leg of the suit. He backed out and tried again. This time the big fishbowl flopped forward into the opening.

Most of the section were already in their suits. The instructor swam over to Matt and looked at him sharply. "You've passed your free-fall basic?"

"Yes," Matt answered miserably.

"It's hard to believe. You handle yourself like a turtle on its back. Here." The instructor helped Matt to tuck in, much as if he were dressing a baby in a snow suit. Matt blushed.

The instructor ran through the check-off list -- tank pressure, suit pressure, rocket fuel charge, suit oxygen, blood oxygen (measured by a photoelectric gadget clipped to the earlobe) and finally each suit's walky-talky unit. Then he herded them into the airlock.

From SPACE CADET by Robert Heinlein (1948)

First Jamieson, then Wheeler, chanted the alphabetic mnemonic - "A is for air-lines, B is for batteries, C is for couplings, D is for D.F. loop ..." which sounds so childish the first time one hears it, but which so quickly becomes part of the routine of lunar life - and is something nobody ever jokes about.

From EARTHLIGHT by Arthur C. Clarke. 1955.

And in Clarke's "The Haunted Spacesuit" aka "Who's There?" they chant "FORB" for Fuel, Oxygen, Radio, Batteries.

[Steve and Nadia] donned the heavily-insulated, heated suits, and Stevens snapped into their sockets the locking plugs of the drag line.

"Hear me?" he asked. "Sound-disks all x?"

"All x."

"On the radio-all x?"

"All x."

"I tested your tanks and heaters-they're all x. But you'll have to test..."

"I know the ritual by heart, Steve. It's been in every show in the country for the last year, but I didn't know you had to go through it every time you went out-of-doors! Valves, number one all x, two all x, three all x..."

"Quit it!" he snapped. "You aren't testing those valves! That check-up is no joke, guy. These suits are complicated affairs, and some parts are apt to get out of order. You see, a thing to give you fresh air at normal pressure and to keep you warm in absolute space can't be either simple or foolproof. They've worked on them for years, but they're pretty crude yet. They're tricky, and if one goes sour on you out in space it's just too bad-you're lucky to get back alive. A lot of men are out there somewhere yet because of sloppy check-ups."

" 'Scuse it, please-I'll be good," and the careful checking and testing of every vital part of the space-suits went on.

From SPACEHOUNDS OF IPC by E.E. "Doc" Smith, 1931.

First things first, and the first thing you need in space is a space suit. Apart from its necessity for working on space projects (building space stations, etc.) it is absolutely vital for examining the outside of your ship in case of damage from meteorites, etc. It may even be necessary to abandon ship, in extreme cases, and in this event your very existence depends upon its efficiency. You see me here in a self-contained, total-vacuum, mark-seven suit. Below you will find listed some of its most important features:

  1. Radio mast of ultra short-wave radio.
  2. Compressed air cylinder of closed-circuit air supply.
  3. Jet on universal mounting and chemical-fuel container.
  4. All joints reinforced. A punctured space suit means death!
  5. Reinforced plastic boots with electro-magnetic soles.
  6. Large universal-vision, anti-cosmic "Plastilight" helmet.
  7. Scaling ring to visor, metal with rubber "hose" lining, inflated from air supply.
  8. Miniature tele-view tray (referred to as the "T" tray).
  9. Control stick to jet (3). Twist grip rotates jet for manœuvring in space.
  10. Hydro-ammonal container and feed line to flame gun.
From Ron Turner's Space Ace pop up book (1953).

Suiting Up

I had an awful time getting into it - dressing in an upper berth is a cinch by comparison. The photographer said, "Just a minute, kid. I've seen 'em do it at Wright Field. Mind some advice?"

"Uh? No. I mean, yes, tell me."

"You slide in like an Eskimo climbing into a kayak. Then wiggle your right arm in-"

It was fairly easy that way, opening front gaskets wide and sitting down in it, though I almost dislocated a shoulder. There were straps to adjust for size but we didn't bother; he stuffed me into it, zippered the gaskets, helped me to my feet and shut the helmet.

. . .

But I didn't get tired of it; a space suit is a marvelous piece of machinery - a little space station with everything miniaturized. Mine was a chrome-plated helmet and shoulder yoke which merged into a body of silicone, asbestos, and glass-fibre cloth. This hide was stiff except at the joints. They were the same rugged material but were "constant volume" - when you bent a knee a bellows arrangement increased the volume over the knee cap as much as the space back of the knee was squeezed. Without this a man wouldn't be able to move; the pressure inside, which can add up to several tons, would hold him rigid as a statue. These volume compensators were covered with dural armor; even the finger joints had little dural plates over the knuckles.

It had a heavy glass-fibre belt with clips for tools, and there were the straps to adjust for height and weight. There was a back pack, now empty, for air bottles, and zippered pockets inside and out, for batteries and such.

The helmet swung back, taking a bib out of the yoke with it, and the front opened with two gasketed zippers; this left a door you could wiggle into. With helmet clamped and zippers closed it was impossible to open the suit with pressure inside.

Switches were mounted on the shoulder yoke and on the helmet; the helmet was monstrous. It contained a drinking tank, pill dispensers six on each side, a chin plate on the right to switch radio from "receive" to "send," another on the left to increase or decrease flow of air, an automatic polarizer for the face lens, microphone and earphones, space for radio circuits in a bulge back of the head, and an instrument board arched over the head. The instrument dials read backwards because they were reflected in an inside mirror in front of the wearer's forehead at an effective fourteen inches from the eyes.

Above the lens or window there were twin headlights. On top were two antennas, a spike for broadcast and a horn that squirted microwaves like a gun-you aimed it by facing the receiving station. The horn antenna was armored except for its open end.

This sounds as crowded as a lady's purse but everything was beautifully compact; your head didn't touch anything when you looked out the lens. But you could tip your head back and see reflected instruments, or tilt it down and turn it to work chin controls, or simply turn your neck for water nipple or pills. In all remaining space sponge-rubber padding kept you from banging your head no matter what. My suit was like a fine car, its helmet like a Swiss watch. But its air bottles were missing; so was radio gear except for built-in antennas; radar beacon and emergency radar target were gone, pockets inside and out were empty, and there were no tools on the belt. The manual told what it ought to have - it was like a stripped car.

Carry steel bottles on your back; they hold "air" (oxygen and helium) at a hundred and fifty atmospheres, over 2000 pounds per square inch; you draw from them through a reduction valve down to 150 p.s.i. and through still another reduction valve, a "demand" type which keeps pressure in your helmet at three to five pounds per square inch-two pounds of it oxygen. Put a silicone-rubber collar around your neck and put tiny holes in it, so that the pressure in the body of your suit is less, the air movement still faster; then evaporation and cooling will be increased while the effort of bending is decreased. Add exhaust valves, one at each wrist and ankle-these have to pass water as well as gas because you may be ankle deep in sweat.

The bottles are big and clumsy, weighing around sixty pounds apiece, and each holds only about five mass pounds of air even at that enormous pressure; instead of a month's supply you will have only a few hours - my suit was rated at eight hours for the bottles it used to have.

. . .

To make darn sure that you're getting enough (your nose can't tell) you clip a little photoelectric cell to your ear and let it see the color of your blood; the redness of the blood measures the oxygen it carries. Hook this to a galvanometer. If its needle gets into the danger zone, start saying your prayers. (ed. note: in Heinlein's other novels, instead of a galvanometer they use an "anoxia warning light")

. . .

Air sighed softly into the helmet, its flow through the demand valve regulated by the rise and fall of my chest - I could reset it to speed up or slow down by the chin control.

. . .

I didn't bother with a radar target or beacon; the first is childishly simple, the second is fiendishly expensive. But I did want radio for the space-operations band of the spectrum - the antennas suited only those wavelengths.

. . .

The only thing that complicated the rest of the electrical gear was that everything had to be either "fail-safe" or "no-fail"; a man in a space suit can't pull into the next garage if something goes wrong - the stuff has to keep on working or he becomes a vital statistic. That was why the helmet had twin headlights; the second cut in if the first failed - even the peanut lights for the dials over my head were twins. I didn't take short cuts; every duplicate circuit I kept duplicate and tested to make sure that automatic changeover always worked.

Mr. Charton insisted on filling the manual's list on those items a drugstore stocks - maltose and dextrose and amino tablets, vitamins, dexedrine, dramamine, aspirin, antibiotics, antihistamines, codeine, almost any pill a man can take to help him past a hump that might kill him.

. . .

I made it a dress rehearsal - water in the drinking tank, pill dispensers loaded, first-aid kit inside, vacuum-proof duplicate (I hoped it was vacuum-proof) in an outside pocket. All tools on belt, all lanyards tied so that tools wouldn't float away in free fall.

. . .

I ran into a snag. The spare bottles I had filched from those ghouls had screw-thread fittings like mine - but Peewee's bottles had bayonet-and-snap joints. Okay, I guess, for tourists, chaperoned and nursed and who might get panicky while bottles were changed unless it was done fast - but not so good for serious work.

. . .

"Mind your pressure. Kip. You're swelling up too fast." I kicked the chin valve while watching the gauge - and kicking myself for letting a little girl catch me in a greenhorn trick. But she had used a space suit before, while I had merely pretended to.

From Have Space Suit - Will Travel by Robert A. Heinlein, 1958.

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

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

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