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There was news of the new SpaceX space suit in Reddit and now a mention in Elon Musk's Instagram where he says:

First picture of SpaceX spacesuit. More in days to follow. Worth noting that this actually works (not a mockup). Already tested to double vacuum pressure. Was incredibly hard to balance esthetics and function. Easy to do either separately.

Question: What does "double vacuum pressure" mean in space-suit testing? How does one test a space suit to double vacuum pressure?

below: From The Verge's 08-Sep-2017 article Elon Musk shares another photo of SpaceX’s future space suits; Full-body this time. Credit: SpaceX/Elon Musk, original Instagram post.

The suits that SpaceX has designed are pressure suits, meant to be worn by astronauts while riding inside the Crew Dragon. They’re primarily needed in case there’s an emergency scenario during flight; if the spacecraft suddenly depressurizes, the suits will keep the astronauts alive until they can get to safety.

enter image description here

below: From last year's reddit post SpaceX suits look like they come straight from a scifi movie, appears similar to image in Musk's instagram post.

enter image description here

uhoh
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  • I miss the connections to the life support system of the space ship. – Uwe Aug 23 '17 at 14:47
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    @Uwe the image the question is an old and unofficial "leak" more than a year old and most probably shows a mock-up. The new one is on Instagram. – jkavalik Aug 23 '17 at 15:06
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    The line after pressure is the one that confuses me. That seems to imply someone at some point considered making it less functional for aesthetic reasons. –  Aug 23 '17 at 18:55
  • @not store bought dirt In case of emergency a space suit is a life support device, functionality should have the ultimate priority in the design process. – Uwe Aug 23 '17 at 19:48
  • @jkavalik The new picture on Instagram does not show the connections to the life support system too. They might be below the lower border of the picture. – Uwe Aug 23 '17 at 19:55
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    First thought is that it's good for double the pressure of a vaccuum. ie. zero psi. Well, that's not very good at all! – Octopus Aug 23 '17 at 20:34
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    Just to add to all the undocumented speculation, I'm going to guess that only the helmet is pressurized in this suit, just like the shuttle astros wore before the Challenger accident. They wore blue unpressurized flight suits and a pressurized helmet. http://www.cbsnews.com/network/news/space/51L/rw_51lphotos/crew_flightdeck.jpg The orange pumpkin suits came after the Challenger accident. – Organic Marble Aug 24 '17 at 20:21
  • The rationale for all LES’s is to provide clean atmosphere to breathe in event of a toxic cabin (think post-fire or toxic release) until it can be scrubbed or purged, AND to provide meaningful protection from DCS if there’s a depress event. I believe pressure profiles for both commercial providers is SBU so cant share that. LES and ACES for shuttle were 3.5psia on-demand. So they provided 3.5 over ambient, down to vacuum, but would only pressurize if cabin pressure was dropping. Soyuz Sokol suits have a different profile but same conops. – JPattarini Jun 15 '19 at 13:27
  • @organic marble That is incorrect. All suits currently in development or operation are fully pressurized, single-volume. The sole exception is the partial pressure suit MIT’s been working on for ages, which is not operationally ready. – JPattarini Jun 15 '19 at 15:43
  • @JPattarini source? – Organic Marble Jun 15 '19 at 15:46
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    @organic marble NASA standard 3001 Volume 1 & 2 requirements are public. CCP requirements were taken from there. Also, this is my job. – JPattarini Jun 15 '19 at 18:17
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    @JPattarini thanks. There is a lot of bs associated with this question already. And as I'm sure you know from JSC "In God we trust, all others bring data". – Organic Marble Jun 15 '19 at 18:25
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    @organic marble You said it. That’s why I chime in once in a while - it’s usually when I see bad data gaining a foothold. As you said, there’s enough of that. – JPattarini Jun 15 '19 at 18:31
  • @organic marble "They wore blue unpressurized flight suits and a pressurized helmet." How would they be able to breath out in the event of a depressurization? They would be fed pressurized air to their helmets, but their chest would be at vacuum pressure. – Mike H Jun 16 '19 at 20:45
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    @MikeH http://www.astronautix.com/l/lehhelmet.html It wasn't a good idea. – Organic Marble Jun 16 '19 at 21:07

5 Answers5

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A space suit could be tested to double the operating pressure. This test can be done in a vacuum or in air. For the stability of the suit, only the pressure difference between inside and outside is essential.

To allow enough flexibility, the pressure difference (inside to outside) should be not greater than 0.2 to 0.4 bar. Breathing pure oxygen in the suit at such a low pressure is possible and healthy to the user of the suit. At higher internal pressure it would be difficult for the astronaut to bend a knee or an elbow.

No Nonsense
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Uwe
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  • This is a nice, concise yet complete answer, and makes a lot of sense. Thank you! – uhoh Aug 23 '17 at 16:50
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    Bend the knee? To Dany? ;) – NVZ Aug 24 '17 at 03:28
  • Current US and Soviet suit designs are 0.25-0.35 bar; do we actually know that SpaceX's design operates with similar internal pressure? – Russell Borogove Aug 24 '17 at 03:29
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    @RussellBorogove: It would be weird if it didn't. I mean, it doesn't contain any revolutionary solutions like exoskeleton to reduce the suit's resistance to flexing (so the lower the pressure the better) and 0.3 bar is a reasonable lower limit where the astronaut can operate without impact on performance. The pressure can be temporarily reduced to allow extra flexibility, but not for long as this causes oxygen shortage. So while the operational limits may differ (e.g. the suit may lack the venting capacity) the nominal pressure shouldn't. – SF. Aug 24 '17 at 10:39
  • The look of the suit -- and I'm talking about the body here, not the helmet -- is different enough from all the suits I've seen before that I'm curious if it actually does incorporate a revolutionary solution of some kind, is what I'm getting at. – Russell Borogove Aug 24 '17 at 15:48
  • @RussellBorogove : The lower limit of suit pressure is given by human physiology and the upper limit by flexibility of the suit under pressure. There is not much range for higher operating pressure for a new suit design. There are no elements for constant volume joints visible. – Uwe Aug 24 '17 at 16:48
  • @RussellBorogove I am guessing only the helmet is pressurized, like the original shuttle launch and entry system. http://www.cbsnews.com/network/news/space/51L/rw_51lphotos/crew_flightdeck.jpg – Organic Marble Aug 24 '17 at 20:30
  • @Organic Marble : those helmets shown in the picture of the shuttle launch are pressurized by a very small pressure only. The pressure difference between helmet and body of the astronaut should be below about 0.03 bar. Such a system would help if the pressure inside the capsule is normal, but there is too few oxygen or to much smoke in it. But if the capsule loses pressure below 0.2 bar, a pressurized helmet with pure oxygen only would not save the astronauts. – Uwe Aug 24 '17 at 21:18
  • @Uwe I've unmarked accept here even though it is highly up voted and I have a hunch it is right, and will keep an eye on the situation. As long as there is a simple pressure relief valve as described in this answer there's no conceivable need for a 2 bar overpressure test. However, an overpressure limit need not be coupled to suit flexibility. Nobody would mind being a rigid balloon for a few seconds if it means not being a popped balloon. So let's see where this goes, and await further data. – uhoh Aug 26 '17 at 04:02
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Pressure here refers to a relative measurement, not absolute, as we're comparing things (inside and out). "Vacuum pressure" here refers to the pressure generated by having a vacuum on one side, and 1 atmosphere of pressure on the other.

This suit has been tested to double that, meaning it had its internal pressure increased to 2 atmospheres, so that double the pressure was applied to it. Thus it was tested at double vacuum pressure.

Nathan Tuggy
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ProPuke
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    A space suit with 1 or even 2 bar pressure inside and vacuum outside would be useless, you can't close your hands or bend a knee or elbow against that pressure difference. Think of the pressure inside a car tire. To allow enough flexibility, the pressure difference should be not greater than 0.2 to 0.3 bar. – Uwe Aug 23 '17 at 14:27
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    @ProPuke Do you have a reference to back up your assertion that the suit is pressurized to 1 atm? – Organic Marble Aug 23 '17 at 14:29
  • I'm sure the suit is not designed to operate at 1 atm, but if you replace the "atmosphere of pressure" with "operating pressure" in the above, the answer would be correct, would it not? I think it gives the right intuition at least and doesn't deserve downvotes. – Bear Aug 23 '17 at 17:17
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    @Bear it's not just a small inaccuracy. Pressure is a fundamental issue of space suit design and use. Wrong answers get down voted, that's how SE works. If they are edited so that they are no longer wrong, that opens an opportunity to reverse the down vote. This encourages the person who writes the wrong answer to fix the problem. Other readers stopping by use up and down votes to judge the accuracy of the post, so up voting a wrong answer misleads future readers and defeats the whole purpose of voting. SE is about good answers, and the votes help show if an answer is good or not. – uhoh Aug 23 '17 at 17:29
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    @Uwe While 2 atmospheres of pressure would be a uselessly rigid suit, we are talking about a test. Certain tests exercise a single property to great extremes beyond normal operation, with disregard for other operational parameters. So I don't think we can assume that the operational practicality of the pressure precludes it from being used as a test focused on durability. You might test at extreme pressures as a safeguard. – AaronLS Aug 23 '17 at 18:47
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    @AaronLS we have no indication that the suit was tested with 2 bar pressure. "Already tested to double vacuum pressure" is not a precise specification. The vacuum in a test chamber for suits might be below 1 mbar down to 1 µbar, but the exact value is not important. The pressure difference between inside and outside the suit is really important. – Uwe Aug 23 '17 at 20:07
  • @Uwe And we have no indication that it wasn't. – AaronLS Aug 23 '17 at 20:09
  • @Uwe And I agree "'double vacuum pressure' is not a precise specification". That's essentially my point. We can't assume test parameters use practical operational bounds, as your first comment stated. Nor can we really assume anything else. – AaronLS Aug 23 '17 at 20:14
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    I am unsure as to why this has downvotes. As a couple of posters have noted, "testing" is very different to "use" and "double vacuum" is fairly commonly used to mean the differential between vacuum and 2ATM. It's an easy standard to understand. – Rory Alsop Aug 23 '17 at 21:37
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    I downvoted it because there is no evidence the answer, which quotes specific pressure numbers, is not completely made up. Or pulled out of thin air, as it were. I would be happy to upvote it if a reference was given. – Organic Marble Aug 23 '17 at 23:25
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    @RoryAlsop the "space" in "space suit" is a clue that the context is not terrestrial, so the sea-level 1 atmosphere concept would not apply. The quickest of searches for "space suit pressure" within this site or of the internet https://i.stack.imgur.com/ImB4i.jpg shows that it's of order 3-6 psi. The mechanism for addressing wrong answers in SE is to down vote and comment, and I'm pretty sure that you understand this concept quite well. – uhoh Aug 24 '17 at 03:12
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    Which is why I happily upvoted it as it is a good answer. Musk is very good at making things accessible to the public - read it again with that in mind. 1ATM does apply when getting them to understand. And please refrain from unnecessary snark - remember the "be nice" rule. – Rory Alsop Aug 24 '17 at 06:19
  • @RoryAlsop encouraging others users to up vote faulty answers is not nice to future readers, no matter how politely it is done. I'm pointing out that you've been active in SE for a while, and I am pretty sure you understand the concept (and importance) of down voting problematic answers quite well. 3-5 psi is so far away from 15 psi that this needs to be fixed. Right now it's plain wrong and you should not advocate up voting. – uhoh Aug 24 '17 at 14:01
  • @uhoh I don't see that you have any citation that proves testing pressures are correlated to operational pressures. You're statement "it's plain wrong" is inconclusive. Again, testing pressures often test extremes far beyond operation parameters. We don't have enough information to determine which answer is correct. – AaronLS Aug 24 '17 at 15:44
  • If the suit was tested with 2 atmospheres internal pressure and this is double vacuum pressure, the conclusion is the value of vacuum pressure is 1 atmosphere. Something must be wrong here... – Uwe Aug 24 '17 at 17:09
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The suit is not designed for space walks. It is meant to protect the user in case they are exposed to vacuum. Therefore I find it strange that the accepted answer assumes the suit would be depressurized. It is not intended to be operated in a vacuum. In fact, the suit will be worn inside the capsule at 1 atm.

Furthermore, seems unlikely that pressurizing a suit to 1.8 atm would be considered rigorous testing (0.8 differential, double max operating pressure). I find it far more reasonable to assume that double vacuum pressure means they pressurized the suit such that the differential was double what it would be if exposed to vacuum at 1 atm. This would be a 2 atm differential, as many downvoted answers have suggested.

EDIT: Here is a fact sheet which has the Dragon capsule's internal pressure at 13.9-14.9 psi

DKu
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  • References....? Not assumptions....? – Organic Marble Aug 24 '17 at 18:26
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    A good stackexchange answer should be more than "I find it far more reasonable..." because a dozen people can post a dozen things that they find reasonable. If you can reason this through, carefully and at least somewhat convincingly, from an engineering perspective, that might make up for not having any verifiable links, but that would be hard. It would be much better to show some verifiable backup to your thinking. Welcome to stackexchange, and if you haven't already, take the tour to learn about what makes a good SE answer. – uhoh Aug 24 '17 at 18:34
  • I am not assuming that the suit is not meant for spacewalks. This is an important clarification, considering the accepted answer appears to make the assumption that it is. – DKu Aug 24 '17 at 18:34
  • Yes, I recognize what a good SE answer is, but I had to say something because the accepted answer is misleading. This suit is not designed for spacewalks.

    I also find it strange that every single answer BUT the accepted answer are being dogged for references, when it does not provide any and makes assumptions as well, such as the false assumption previously mentioned.

     – DKu Aug 24 '17 at 18:35
  • OK, I understand. And it is a challenge right now because you can't leave a comment under the other answers until you get a little more reputation (points). But posting a comment as an answer is not really a solution to that. You could go to the SE chat area and start a discussion perhaps, but doing it this way is not how SE works. Answers have to be answers to the question as asked. – uhoh Aug 24 '17 at 18:39
  • By this logic, the accepted answer is not a good one. None of the information provided in it is relevant. It assumes what double vacuum pressure is, and provides information on pressurization for spacewalks, which this suit will not be used for. My answer at least provides a helpful bit of info in that the suit is NOT meant for spacewalks. It's a pressure suit. – DKu Aug 24 '17 at 18:41
  • The live SpaceX broadcast has just started; launch in about six minutes. I'm going to watch it :) This question will still be here tomorrow. 21 up votes suggests it's not such a bad answer. If you look you'll see that suits are in the 0.2 to 0.4 bar range, I do not think you will find one in use anywhere today that is useful with a 1 bar pressure difference. But, if you do, that would help support your answer! – uhoh Aug 24 '17 at 18:41
  • Yes, the information in the answer is accurate, but irrelevant. It gives no information that would validate "double vacuum pressure" means double operational pressure. As far as 21 votes, there is a reddit answer to this same question with 160 votes, stating that double vacuum pressure is 2 atm differential - https://www.reddit.com/r/explainlikeimfive/comments/6vijzp/eli5_how_can_you_have_double_vacuum_pressure_to/ – DKu Aug 24 '17 at 18:58
  • @DKu: Yes, because votes on Reddit clearly indicate what's authoritative reference material and what isn't. That said, this could be a good answer; I think the missing link is the unsupported assertion that the capsule will be at 1 atm, which a quick search could find neither proof nor disproof for. – Nathan Tuggy Aug 24 '17 at 19:05
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    Here we go, a Dragon data sheet, which has the internal pressure at 13.9-14.9 psi: http://www.spacex.com/sites/spacex/files/pdf/DragonLabFactSheet.pdf – DKu Aug 24 '17 at 19:11
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    Using a 1/3 atm suit is accepted practice (on shuttle, and ISS) and doesn't require references. Using a 1-2 atm suit isn't, and does. It would be wonderful if someone made a usable 1 atm suit, eliminating all annoying prebreathe protocols. I just don't believe that it has happened yet. – Organic Marble Aug 24 '17 at 20:14
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    @DKu : the Dragon data sheet gives a value of 13.9-14.9 psi for normal pressure inside the capsule. But there is no specification for the pressure inside the suit in case of emergency when the capsule has lost its atmosphere. – Uwe Aug 24 '17 at 20:21
  • The suit is worn to be prepared for the case of emergency when the capsule loses its atmosphere and there is a vacuum inside. In this case the suit will be operated in a vacuum. If the pressure inside the suit is still 1 atm, the astronaut is severly handicapped by the inflexible suit. – Uwe Aug 24 '17 at 20:56
  • @DKu I'm starting to have second thoughts as I keep turning this over in my head. Testing to see when it "pops" is related to avoiding loss of life in extreme circumstances, and this is different than mobility/dexterity. – uhoh Aug 25 '17 at 00:08
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I concur the Double vacuum testing is probably testing to twice bursting strength in vacuum.

See http://www.astronautix.com/s/spacesuits.html for a fascinating look at various spacesuits. They have been made out of pure metal, fabric, mixed materials, at 1 atm, at 0.2 atm, or at no atm simply mechanical counter-pressure. They have used "tomato worm" limbs (constant volume convoluted tubes - the better with to bend at pressure) among other solutions. All of the solutions work. The question is what question are you asking; "get me down" suit, survival suit, open space/outside vehicle suit, lunar surface, martian surface? What the constraint of this particular suit is will be fascinating.

Richard McCue
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    Do you have any references to support your assertion that the suit was tested to twice its burst pressure? Please note that the suit would certainly have been damaged in that case, since burst pressure, is after all, the pressure at which it would burst. – Organic Marble Aug 23 '17 at 23:28
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    Testing to twice the burst strength seems to be self-contradictory. Imagine Musk saying "Already tested to double the burst pressure." The only way this could be true is if the burst pressure were zero; 2 x 0 = 0 or more nicely put "Twice nothing is still nothing" – uhoh Aug 24 '17 at 06:31
  • You want to rise pressure until the suit bursts and then double the pressure inside the suit? But there is a hole now in the suit and rising pressure is not possible with a big hole. – Uwe Aug 24 '17 at 16:38
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Double vacuum pressure would mean two atm of difference from inside to outside. Others have remarked "you can't close your hands or bend a knee or elbow against that pressure difference": that's why space suits are normally designed with joints that operate without changing the inside volume and thus are not susceptible to stiffening under the large pressure difference.

That's what makes them bulky. The picture shown here is nothing like that. I wonder why.

  • Do you have a reference to back up your assertion that double vacuum pressure for this suit is equal to two atmospheres? – Organic Marble Aug 23 '17 at 18:31
  • It is not true that double vacuum pressure would mean two atm of difference from inside to outside. That is only a wrong interpretation of a unclear and misleading statement. Designing the suit with constant volume joints does not help the astronaut to close his hand against pressure in the glove. But it is true that the pictures do not show any indication for constant volume joints. – Uwe Aug 23 '17 at 20:19