Space Suit Design

NASA's space suits were made with an anthropomorphic image to meet a socio-political requirement.

There are two basic designs for space suits: soft and hard. Hard suits have rigid bodies made out of plastic and metal; the suits move only along the joints. Soft suits are made out of cloth; they're supposed to be flexible, but they aren't, because there are too many layers. Soft suits have gloves, hard suits have grippers. Hard suits are simpler, thus cheaper and more reliable. They're also more maneuverable and the grippers are more useful. You can do things with hard suits that are impossible with soft suits, like cover them with armour.

Hard suits are superior in every way - except for one way: soft suits look human-like, hard suits look robot-like. So NASA went with the soft suits - a psychological factor trumping all the engineering factors.

-- RichardKulisz

Hard suits weigh more. At $10,000/lb launch costs, weight is always a huge factor in designing for space. I highly doubt (gut feeling) that the work done on the Hubble repair could have happened with grippers. Oh and the suits used now are 2 pieces and come in just a few (three?) sizes, rather than being custom-fitted the way suits were through the Apollo era. Can hard suits be made to one size fits all? Shuttle era suits weigh about 100lbs, have a 100% oxygen atmosphere at 4.3 or 8.3psi. The top is hard-shell fiberglass, the joints requiring the most mobility are mechanical bearing assemblies - http://spaceflight.nasa.gov/shuttle/archives/sts-70/crew/wardrobe.html. I'd like to see some specific references to the assertion that the current suit design is compromised by requirements that it 'look human'. -- StevenNewton

Shuttle era suits keep a pressure difference of less than 1 atmosphere. Hard suits used in deep sea diving have to sustain pressure differences many (hundred?) times that; that is why they weigh so much. I'm certain (gut feeling) that anything made out of cloth will be heavier than something of equal rigidity which is made out of a stronger material like aluminum. I'm equally certain that NASA's R&D efforts applied to hard suits would've made as many gains as with soft suits.

The only advantage of gloves is having some tactile feedback. But how much can a person feel through those gloves anyways? Do astronauts ever rely on it? And nowadays, such things can be simulated; and as technology progresses, it becomes more and more desirable to have sensations transmitted by technology instead of relying on crude gloves. -- rk

NASA did investigate hard suits in the early days. As far as I recall from the documentary where this was discussed, the hard suits had two perceived disadvantages over the soft. Firstly, the joints sometimes had to be "programmed", that is the wearer couldn't always move directly between any two positions, sometimes they had to move the joint to a special intermediate position before moving to the desired position. And secondly, the assessment of the two suit technologies was done on the surface of the Earth, (possibly with no pressure differential across the suit material, I can't exactly recall). Under those conditions, the hard suit performs comparatively badly, the wearer appears slow, clumsy and hampered; whereas the wearer of a (deflated) Mercury type soft suit could do gymnastics.

Rigidity, by the way, is not a fixed requirement. Some perfectly feasable suit designs have almost no rigid components at all, using layers of elastic material to exert the required pressure on the wearer's skin directly, rather than through maintaining a pressurised atmosphere around them.

Can you point to any sites with info about these suits (the only reference I can get to them is in JerryPournelle science fiction and the MillenniumProject?. Has anyone ever built an elastic, "skin reinforcing" suit?

A PSI of < 1 atmosphere means you can use pure O2. If you have at least 1ATM you have to use an O2/N2 mix (or else you get extreme fire danger, as happened in the Apollo 1 capsule fire). A mixed-gas system is extra complexity that could fail, and it adds weight also. Soft suits aren't "cloth", they are modern lightweight materials like Kevlar, spandex, Dacron and Teflon. Because they only need to sustain a few psi (or at most 1ATM if you go with mixed-gas), there's zero benefit to using materials that can sustain deep-sea pressures.

Force-feedback at the level of human touch is still in its infancy, and NASA prefers to use reliable technology, and of course the process of space-rating something itself adds a delay to the adoption of new technologies.

-- StevenNewton

Metals have the reputation of being heavy, but a metal cylinder designed to hold 1 atm of pressure difference (or any other non-zero pressure) is lighter than a cylinder of spandex, Kevlar, or any other kind of woven material designed to hold the same pressure. That's why all space stations have been made of metal, rather than being inflated. -- DavidCary

Really? Tell that to Robert Bigelow....

As far as I can tell, Bigelow attempted to solve the problem of compactly transporting habitable modules. I do not believe he was primarily concerned with weight. The inflatable module is very compact, as it allows the station module to ship as a pancake-shaped contrivance, which then inflates to its final shape upon destination arrival. In theory, this lets you transport a greater amount of mission equipment, which better amortizes the costs involved (or, by using a smaller lifter, which ends up being net-cheaper because of reduced fuel requirements).

"there's zero benefit to using materials that can sustain deep-sea pressures."

Yes, exactly. A hard suit designed for space (lightweight, sustain 1 atm or less) is going to be much, much lighter than commercial hard suits designed for the deep sea (needs to be extra heavy so it doesn't bob up to the surface). In fact, it should (in theory) be even lighter than the flexible suits.

Actually, I think the soft suits look bizarre and unhuman. What do the hard suits look like? Like the suits in 2001: A Space Odyssey? Can you point me to a web site with pictures?

Entire Document (Designed for use by Elementary School Teachers)

A simpler case is the color of the space suit. The suit used on the very first American space launches was identical to that used by SR-71 pilots. The exception was that it was now in a space-age looking silver color, instead of the original orange-red. Some claim that this had nothing to do with radiation protection, and everything to do with looking cool. (See the above references for info about the different (currently worn) suits, including an orange one for launch-reentry)

"Have Spacesuit - will travel"

MIT has a new design for a space suit, the [biosuit]: http://web.archive.org/web/20070809033939/http://web.mit.edu/newsoffice/2007/biosuit-0716.html

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