At what point can an astronaut take off their helmet and why do they need to wear one for take off? (Asked by an actual 5 year old)
In: Physics
In the Space Shuttle (less so on the SpaceX rocket and its lovely minimalist design!) it wasn’t so much the risk of explosion (which the Shuttle had no real survival mode for anyway) but stuff flying off the dashboard and hitting crew members in the face.
I remember one Youtube video of a “shuttle launch to orbit from in the cabin” and one of the crew’s flightplans comes loose from its velcro housing when they’re at about 6g before main-engine cutoff, and it flies right to the back (bottom) of the upper deck. They joke about it, but a 1kg ring-bound flightplan in a hard plastic cover, at 6g, isn’t something you want slamming into your face when you can’t even put your arms up to shield yourself.
At least in the Space Shuttle days, it really was as “trivial” as that.
Once the dangerous part of the launch is over.
The first thing the spacecraft has to do it to get into orbit by riding on top of a huge rocket. This is very dangerous as rockets are known do spontaneously explode on occasion (as you would expect from a vehicle made of 98% fuel and riding a explosion at 10 times the speed of sound).
Once into orbit and clear of the rocket the risk of an accident requiring a helmet becomes basically 0.
**[edit]** They’ll have to put their suit and helmet back when approaching the space station, because it is also dangerous (the main risk is a loss of control and collision with the station)
**[edit]** For those confused: the helmet isn’t here to protect them from an explosion directly, but from the potential decompression that comes with a failure of the vehicle and/or the violent shaking and acceleration that happen in an abort scenario.
Should it be EBIA5 (Explain Because I Am 5)?
I don’t have an answer for this, but I just want to say that’s a really good question from someone that age
The short answer is when it is safe. The first leg of the launch is super dangerous. Once you are in space, there isn’t really a whole lot to go wrong.
While the engines are burning, something could fail. These things are crazy hot, and crazy complicated. One little thing going wrong can cause an explosion in the blink of an eye.
Challenger is an unfortunate example. There was a piece of rubber (an o-ring) that froze, and so it didnt seal properly. 73 seconds after launch the shuttle disintegrated.
Additionally, the atmosphere gets really thin really quickly. Once you are in space there’s not a whole lot of forces on the rocket. But going through the atmosphere you have to push all the air out of the way.
Columbia is an unfortunate example of this. On launch a piece of foam broke a panel of the shuttle. On reentry, since the panel was cracked the force of the air ripped it open and the entire shuttle got destroyed.
Both of these things end at about the same time. The lower stage(s) disconnect pretty soon after it is out of the atmosphere. Once in space, the capsule keeps moving along since there is nothing to stop it. Also theres really not a whole lot of force on it, so there’s really just not anything left to go wrong.
Edited: The Challenger disintegrated, it didnt explode
The suits worn for launch are called “flight suits” and are distinct from the suits used for spacewalks *(which are almost closer to suit-shaped vehicles)*.
The flight suits ~~are not sealed/have no life-support systems~~ are sealed/probably have limited life-support systems and can be though of as something like what a test pilot or race car driver wears specifically to minimize/prevent injury during a crash or otherwise violent incident and those helmets are pretty much exclusively to protect their heads/faces from *impact* trauma… *edit:* AND I don’t know if the limited life-support is tied into the vessel or entirely self contained or how long it can function but the “flight suits” of previous programs have traditionally been thought of as “get me down” suits for whatever that tells us about…
[This is the new “spacewalk-suit”.](https://www.wired.com/story/no-more-spacewalk-snafus-nasas-new-space-suit-fits-everyone/) *(note all the hardpoints/metal swively-bits/the fact you basically open the back and “climb in”…)*
***
On Earth a human can wear a simple helmet/facemask to overcome an environment with no breathable air but in outer space we need to re-create that protective layer of atmospheric over the *ENTIRE BODY*.
It’s not just that there’s no air in space… When people talk about the *VACUUM* of space that basically means that not only is there no air up there but space is *actively* trying to remove air from anything that has it…
If you’ve ever sucked the air out of a bottle/glass and felt it stick to your lips or mouth you then imagine a force hundreds of times stronger acting *everywhere all at once* and you get an idea of how much more dangerous outer space is for human.
***
…and this one just ate at my little noodle for years and I wished someone had explained better when I was little but when people talk about a vacuum or low-pressure environment causing your blood or spit to “boil” it makes a more sense if you think of how the entire atmosphere is a fluid that goes from a very sparse/loose level of compression near the edge of space to a very high level of compression deep below the surface.
We live near sea level at a medium level of atmospheric compression and to transport us to the edge of space is to transport a fleshy pressure vessel to a low-pressure environment.
Boiling is a physical process of releasing pressure from a fluid and we know it takes heat energy to do it down here at sea level and then we know it takes a little less heat energy to boil water at a higher altitude *(food packaging will direct you to boil for longer at a higher elevation because it simply can’t get as hot so it takes longer to achieve the same cooking results)*.
I finally just imagined taking that pot of water all the way up to the edge of space and how without applying any energy at all it would start to froth and “boil” away to vapor as it simply became easier for the fluid to naturally flow from an area of high pressure to an area of low pressure as the area of low pressure became *everywhere*.
“Boiling blood” just sounded like science I couldn’t understand rather than common sense until I imagined that soaring pot of water…
When the rocket take off. The rocket will fight against the earth gravity to get outer space which mean it will create a G-force. Astronaut clothes create it own pressure and prevent blood on human body boiled, prevent oxygen pushing downward to earth gravity which cause lack of oxygen around the face of astronaut.
I do have a related question…
If there is an emergency and a hole gets knocked in the side of the space capsule so that the air is lost, though the ship is otherwise okay, what are the options in most cases for getting the astronauts back? Do they expect to try to dock with, or EVA (spacewalk) to the ISS and wait for another mission, or can they possibly deorbit and hope their ship holds? Obviously, it would depend on the circumstances.
They don’t need the helmet at all. You could fly in the Dragon craft in your underwear. Or less
The helmet is worn for two reasons. One is that in the case of a failure, the astronauts are likely to be jostled around in the craft, possibly banging their heads. You don’t want them to be stunned, because you may need them to be able to make fast, correct decisions to save themselves. So the physical protection of a helmet is important.
The second is a failure of craft could let all the air out. The helmet is sealed and fed with pressurised air, or even oxygen, to keep them alive if that happens.
Once the dragon craft is released, there is no force out there that could jostle the craft, or that could break anything and let the air out quickly. So the risk is low, and so they take off both the helmets, and their flight suits.
Woody from toy story, “I just lit a rocket… rockets explode!!”
Once the rocket stops exploding they can take their helmets off.
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