Transition from pressurised envoronment to vaccum environment

[armin11]

Hi,
I wanted to know who has an idea about a mechanism to transit from pressurised environment to vacuum environemtn without losing air.I know airlock does this work but it has some air loss.does anybody have idea?
I thought about some kind of bulb to be produced at the transition place,is it possible?is there any kind of material to do this?

 

[armin11]

material like soap bulb but stiffer that cannot transit matter

hi,
is there some kind of material that is not able to transit air molecules but is able to transit humans through it?something like soap bulb but stiffer that can recover itself if a perturbation occurs in it?

 

[Mech_Engineer]

There is no such thing available, what you're proposing would be something akin to a force field. You're going to have to use an airlock, there's basically no way around it.

 

[Mech_Engineer]

There's no way to do this wihout an airlock. You can pump down an airlock, I'm not sure its a given that you lose air through it...

 

[armin11]

But I think we can replace airlock,airlock loses some air each time it opens,though it is about 2 or 3 percent but it is considerable in a spacecraft ...

 

[Mech_Engineer]

What you're proposing is impossible given current technology- you would need an air-tight seal around whatever passes through the "membrane" (an impossible feat with something like a space suit which is covered on the exterior with fabric) and it would also have to capable of maintaining a non-leaking vacuum seal (also no small task).

 

[armin11]

Impossible is impossible!
The material can be like ambrio around baby when it is born!

 

[Mech_Engineer]

:zzz:

Got any material suggestions that act as a porous membrane to a man in a space suit but not air molecules?

 

[berkeman]

Hi,
I wanted to know who has an idea about a mechanism to transit from pressurised environment to vacuum environemtn without losing air.I know airlock does this work but it has some air loss.does anybody have idea?
I thought about some kind of bulb to be produced at the transition place,is it possible?is there any kind of material to do this?

hi,
is there some kind of material that is not able to transit air molecules but is able to transit humans through it?something like soap bulb but stiffer that can recover itself if a perturbation occurs in it?

Two threads merged.

arimin11 -- in the future, do not multiple post your question across multiple PF forums.

 

[cmb]

Actually, for some applications (particle beams) it is not only possible, but I believe it is now a commercial product.

See 'plasma window'.

Here is a link I've randomly pulled up:

http://www.techbriefs.com/content/view/1834/32/

http://www.aps.org/publications/apsnews/200501/dpp.cfm

 

[armin11]

Thanks cmb, interesting topic!

 

[Mech_Engineer]

So you're suggesting the astronaut should pass through a plasma arc?

 

[armin11]

Not exactly pass through plasma arc,but there can be a basic research based on the facts about plasma window,I think it is better than nothing! You see a problem here or have another opinion?

 

[Mech_Engineer]

My opinion is the same- you need an air lock...

 

[armin11]

I'm not sure about the effects of plasma on the astronaut's health and his systems.
How about using force fields or force shields?Any opinions?

 

[schliere]

Where are you getting this notion that that sort of technology exists or even is anywhere near usable?

 

[armin11]

I don't say it is usable now,but someday it'll be usable and the technology will be developed.So any idea now what the technology will be?

 

[Ryan_m_b]

Let's not bicker people.

Force fields are pure science fiction. The membrane idea is interesting but essentially it's just a fancy airlock, albiet one that uses endocytosis. How about rather than focussing on highly/overly speculative ideas (some of which have no basis in reality) you focus on the engineering problems of airlocks to make them more efficient?

 

[armin11]

You mean like recapturing some of the lost air?I've thought about it.My idea is that we transfer high voltage electricity to the air exiting airlock to make it ionized then with the help of a magnetic filed inside the airlock we can collect these air molecules that have gone out of airlock.But there are some flaws to this concept,like high voltage in a room full of oxygen is disaster or these ionized air molecules could harm astronaut's charged systems. Any idea to do this air recapturing ?

 

[MikeBH]

I like this questions. Innovative idea. However, passing through a substance might be possible. But not in a standard suit. As the astronaut is halfway through he will experience air pressure on one side and vacuum on the other. Given that his cross-section will be about 1m^2 that's 10 tonnes. It would put him under a bit of pressure. Suits are designed to take the pressure from the inside not the outside.

To prevent this problem he would have to have a special suit to go through or the substance would have to be very thick. Eitherway we are getting back to an airlock. If you really wanted to prevent air leakage it would be easier to design the airlock to collapse to prevent leakage. So the airlock is made of soft material that surrounds the astronaut when he enters and pushes all the air out. Then the air lock opens and no air is lost.

 

[armin11]

Thanks MikeBH, nice point about the material.I was googling some ideas and I found a technology called suitport. It is in a way that spacesuits are outside the spacecraft and when astronaut wants to don them he goes directly from a room into his suit and drifts away from spacecraft . This concept has some flaws,as the pressure between suit and room are different and what could possibly be the technology for returning to spacecraft . returning must be something like airplane landing,it should be precise and controlled.What you guys think of this idea and how can be the returning system? can he use some sort of electromagnetic things that when astronaut is close enough these systems are activated and park the astronaut autonomously in his place?

 

[MikeBH]

Thought this thread might be interested in this - what happens to a body in a vacuum?
That empty feeling, when everything sucks! http://wp.me/p2lfqY-11

 

[armin11]

How can we design a suit that can be donned and doffed symmetrically?I think if the suit is like coffin this criteria will be met!

 

[MikeBH]

Use a vacuum pump on the spacecraft to evacuate the air in the airlock back into the craft before opening the doors. Simple engineering solution.

 

[armin11]

They do that on airlocks,they pump the remaining air of airlock and vacuum it,but there is still some air loss.How could that little amount be zeroed,that is the problem.

 

[Ryan_m_b]

Thanks MikeBH, nice point about the material.I was googling some ideas and I found a technology called suitport. It is in a way that spacesuits are outside the spacecraft and when astronaut wants to don them he goes directly from a room into his suit and drifts away from spacecraft . This concept has some flaws,as the pressure between suit and room are different and what could possibly be the technology for returning to spacecraft . returning must be something like airplane landing,it should be precise and controlled.What you guys think of this idea and how can be the returning system? can he use some sort of electromagnetic things that when astronaut is close enough these systems are activated and park the astronaut autonomously in his place?

I'm not sure what you mean by returning, I don't see why it would be that much different to finding the airlock. Essentially the design is that a suit is attached to the outer hull with the back of the suit opening up directly into the ship. All an astronaut does is climb into the suit, press a button to close the back of it (presumably another tight fitting hatch closes on the inside to prevent a hole) and disconnects: see this picture for a demo. It could be made so that where the suit is stored there are protruding hand holds so that when an astronaut gets back he holds on and slots himself in place.

 

[armin11]

By Returning I mean that when astronaut does his/her job and wants to get back to airlock. i think it is better if astronaut gets close enough to a distance to the craft and then an autonomous system catches him and attaches him to the craft.In the suitport, donning and doffing are not symmetrical, I mean doffing the suit isn't as easy as donning it. I'm trying to come up with an idea for a suit that it can be donned and doffed easily.Any ideas?

 

[Travis_King]

The amount of oxygen the astronaut is taking with him to breathe is much more than the losses in the airlock. The energy needed to nigh-fully pump down the airlock is probably more detrimental than the slight air loss.

 

[Ryan_m_b]

By Returning I mean that when astronaut does his/her job and wants to get back to airlock. i think it is better if astronaut gets close enough to a distance to the craft and then an autonomous system catches him and attaches him to the craft.In the suitport, donning and doffing are not symmetrical, I mean doffing the suit isn't as easy as donning it. I'm trying to come up with an idea for a suit that it can be donned and doffed easily.Any ideas?

I still don't understand why an automated system is needed. Astronauts have managed for decades to get out of and into their vehicles, why would a suitport system be any more complicated.

Regarding getting in and out it is hardly any more complicated than a Russian Orlan suit and IIRC those allowed a cosmonaut to go from inside to full EVA in a matter of minutes compared to the NASA suits that took hours.

 

[armin11]

@Travis: So we try to come up with an idea to both lower the power and cost needed and lower the air loss!
@Ryan: Don't you think it'll be good if an autonomous system catches them?! We had some cases where astronaut couldn't find the airlock door or couldn't ingress the airlock!
So let's think about improving EVA from the way it is!

 

[Ryan_m_b]

@Ryan: Don't you think it'll be good if an autonomous system catches them?! We had some cases where astronaut couldn't find the airlock door or couldn't ingress the airlock!

Ah I see, I thought you meant that a suit port specifically would need one. As for floating away a tether would be useful.

 

[Travis_King]

@Travis: So we try to come up with an idea to both lower the power and cost needed and lower the air loss!

The thing is, if you want to reduce power, you have to do it slowly (reallllly slowly if you also want to drop the pressure as close to vacuum as is practical). They already do this because you can't just take an astronaut, whose body is at 14.7 psi, and throw him in a suit that's pressurized to ~4.5 psi. He would most likely suffer decompression sickness (the bends). So they slowly drop the pressure in the crew cabin (or equipment cabin) to acceptable levels. They can drop it even futher after that, but that would mean hours sitting in a space suit waiting for the room to decompress. (unless, of course, you wanted to use a big heavy motor/pump and use up a great deal of precious energy).

For a larger scale station, with a great many space walks, it might be practical to invest in this (although one would imagine the number of flights coming to replenish supplies would be numerous enough to take care of lost air), but for something like this it's not really worth the time and money.

 

[armin11]

Dear Travis, I'm thinking about a large scale station and in it the tiny bit of air and oxygen are important! We don't have much available sources in long distance trips for example to mars,to produce needed oxygen for daily use so we must get the best of the available air, so we don't want to lose even the tiniest oxygen molecule! What I understand from your post is that you say we build larger pumps with greater efficiency. Is that right? But if astronaut goes directly in his suit we won't have the problem of waiting for the room to decompress.

 

[Travis_King]

It's a very nice idea, and certainly a problem for longer treks, as you pointed out. But here's the problems

1. The energy required to pump the room down to near vacuum means a larger, heavier pump/motor. This means heavier deadweight, thus more fuel required, plus less space. But this isn't the main problem, especially on so-called "Large scale stations".

2. The big problem is the time it takes. What are you gaining by waiting in the suit inside the room while the air pumps out? An average person uses approximately .5 Liters of air per breath at normal conditions. (and at standard psi, its somewhat less at the 4.3 psi suit pressure, though somewhat higher in O2 concentration). But let's say .5L per breath. Thats roughly 7.5 L of air per minute, 450 L per hour.

They already spend nearly an hour decompressing down to the nominal suit pressure (after several hours decompressing down to the ~10 psi I mentioned before) So you would need to balance between the air used just waiting versus venting the 5psi compartment. You waste both time and air depressurizing the compartment, whereas you can vent the air you would lose waiting anyway and spend the time and oxygen on something worthwhile.

I haven't done any of the calculations, but I'm going to bet it's either close, or it's deemed more valuable to have them outside breathing oxygen, than having the astronauts sitting inside wasting that oxygen in an attempt to save air that is mostly nitrogen.

 

[armin11]

Thanks,nice points! I've thought about donning suits in higher pressures like 8 psi and then until we reach the destination lowering pressure for the dexterity, but there are constraints in suit materials I think. What do you suggest for breathing oxygen outside?