Transition from pressurised envoronment to vaccum environment

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 space craft 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

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

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

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

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 wanna 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 lets 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.