Is there a logical reason why astronauts’ space suits have legs? They don’t walk anywhere. Wouldn’t it make more sense to have a single pod for both legs, which would make it easier to put on and take off the space suits?

【翻译自quora, Jonathan Miller, 30+ Years NASA Engineer, Johnson Space Center, Houston 】

Believe it or not I’ve been asking that question for years. I call it the Dolphin or Mermaid suit.


And finally I got another engineer’s attention long enough to explain why this is not such a good idea.


First of all you are correct, in freefall (microgravity) of the ISS they are not walking. There are still stresses that have to be accounted for. When an astronaut is manipulating a massive object they must react those forces somehow. Most commonly that is done with foot restraints.


Now I can imagine designing a foot restraint that works with a single pod for both legs. But getting into and out of that would be very tricky. Not to mention we already have these in use all over ISS and they would need to be replaced.


More fundamentally there is a bigger problem. Suit sizing is not just a matter of convenience. The astronaut is actually floating within the spacesuit and when the crewmember moves, the suit has to move with him or her and the load path has to be consistent and understood for it to work properly.


In other words, you have this volume pressurized to 4.3 pounds per square inch and this large voluminous pod where your legs are, when you start torquing a bolt, how are your legs positioned within that pod? How do you react that load?


The current spacesuit is quite rigid in the lower torso and reacts much of that load for you. And that load is distributed across your entire lower torso.


We don’t handle large satellites like this anymore, but if that satellite starts going sideways can you imagine the loads going through the crew member?


Finally, last but not least, in a large pod for both legs the hoop stress would be enormous. The hoop or circumferential stress increases in proportion to the radius. The spacesuit already has a large thick metal reinforcement at the waist to counter this. With a large pod for both legs this metal reinforcement would need to be extended all the way to the feet. This additional weight would negate any material savings from not having individual legs.


So there you have it, the Dolphin suit would actually be quite challenging to make.


@ Mark Shulmann

Good answer, Jonathan. I’m sure you’ve hit all the major reasons, but I’m wondering about a minor reason: It seems to me that having your legs “tied together” in a single pod might give an astronaut a claustrophobic feeling. I’m sure if there were a big advantage to having a single leg pod, then you’d just suck it up and train until the feeling of being bound goes away, but I wonder if any of the astronauts have ever expressed a preference for separate suit legs. It seems like it would feel more natural, but maybe when you’re in free fall you really don’t care about your legs. Any idea?

好答案, Jonathan 。 我确定您已经写出了所有主要原因,但我想知道有一个次要原因:在我看来,双腿“绑在一起”到一个裤筒中可能会使宇航员产生幽闭恐惧感。 我敢肯定只有一个裤筒有很大的优势,那么您只需将把双腿放在一起并训练,直到被束缚的感觉消失,但我想知道是否有任何宇航员曾表示过喜欢分开双腿的宇航服,这样似乎感觉更自然,但也许当您飘来飘去的时候,您实际上并不在乎您的腿。 有什么想法吗?


I think if we had a spacesuit for tourists it would be acceptable to have a leg pod. The difficulty is when you need to use your upper body to do work. You need a stable lower body. For tourists you could imagine a pod for the entire body with no arms and legs. Kind of like the rescue ball.

我认为,如果我们为游客提供太空服,那么只有一个裤筒是可以接受的。 困难在于您当用上半身来做工作时。 您需要下半身很稳定。 对于游客来说,您可以想象包裹住手和腿的整个宇航服。 有点像抢救球。

@ Mark Shulmann

Wow, that does not look comfortable. The tourism thing is starting to lose some of its luster! Thanks for the reply, and for the thoughtful original answer.

哇,看起来不舒服。 旅游业看起来并不很好! 感谢您的答复和深思熟虑的原答案。

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