NASA Is a Human Mission to Mars Feasible in the Near Future?

[mheslep]

I hadn't studied the details of the accident.
A pure oxygen atmosphere at a 21% partial pressure makes sense (and was used in Gemini/Mercury). Inward opening plug seal doors without explosive bolts are used on all commercial aircraft it balances the real risk of a leak with the few times during the flight when you can safely open the door.
It seems from the account that it was a very very badly thought out test rather than the design that was wrong. In particular pressurizing it to a flight pressure differential but still using pure oxygen was insane!

mgb - What do you mean by 'pure oxygen atmosphere at ... partial pressure'? Is that contradictory or do I miss something?

 

[mheslep]

How is it different? NASA had been warned about using a 100% oxygen atmosphere. They ignored those warnings. ...

IIRC, Apollo 1 was not a case of ignoring warnings, but a failure to weigh them adequately. They were up against a weight budget, and low pressure O2 saved considerable weight and space over a full pressure mixed atmosphere. So I would say they weighed the risks of pure O2 (incorrectly?) versus other design factors, not ignored them.

 

[mgb_phys]

mgb - What do you mean by 'pure oxygen atmosphere at ... partial pressure'? Is that contradictory or do I miss something?

Air is 21% Oxygen, if you make an atmosphere of 100% oxygen at 21% of atmospheric pressure the chemical effects are identical (Guy-Lussac's Law). You can breathe it and it doesn't burn any more strongly.

The advantage is that you reduce the pressure on the spacecraft hull by a factor of 5, you don't have to worry about decompression sickness (the bends) if you lose pressure and you don't have to carry the (admittedly small) weight of useless nitrogen.

But the same thing doesn't apply if you then do a test with 1.21 atmospheres of 100% O2 - that's just crazy!
They should have pressurised with either air or 1 atmosphere of an inert gas and then added 0.21atm of 100% O2.
A partial pressure of >1atm of O2 is always dangerous, in a decompression chamber you have to be careful that you haven't got any oil or grease on your clothes and that all the materials are safe. You can't even wear a cotton sweatshirt because of the fire risk.

 

[mheslep]

Air is 21% Oxygen, if you make an atmosphere of 100% oxygen at 21% of atmospheric pressure the chemical effects are identical (Guy-Lussac's Law). You can breathe it and it doesn't burn any more strongly.

The advantage is that you reduce the pressure on the spacecraft by a factor of 5, you don't have to worry about decompression sickness (the bends)if you lose pressure

Doesn't burn more strongly? Pressure aside, I understood that the presence of N2 greatly reduces the ignition hazzard. That is, pure O2 at even 21% of STP is an extreme fire hazzard compared to 21/79 O2/N2 at STP.

and you don't have to carry the (admittedly small) weight of useless nitrogen.

But the weight is not small: ~4x the gas by volume for 5-10 days of air for 3 man crew + additional tank overhead.

 

[mgb_phys]

Doesn't burn more strongly? Pressure aside, I understood that the presence of N2 greatly reduces the ignition hazzard. That is, pure O2 at even 21% of STP is an extreme fire hazzard compared to 21/79 O2/N2 at STP.

No, at normal (ideal gas law) conditions it doesn't make any difference.

But the weight is not small: ~4x the gas by volume for 5-10 days of air for 3 man crew + additional tank overhead.

I would have thought (running an air atmosphere) you would just absorb CO2 and top-up with pure Oxygen - so you only need to carry the amount of O2 actually used. The nitrogen isn't lost.

 

[mheslep]

No, at normal (ideal gas law) conditions it doesn't make any difference.

Hmm. Ok thanks. So what was the cabin pressure w/ Apollo One?

I would have thought (running an air atmosphere) you would just absorb CO2 and top-up with pure Oxygen - so you only need to carry the amount of O2 actually used. The nitrogen isn't lost.

Well the lift off stored gas must be 4x heavier w/ STP cabin atmosphere vs 21% STP. Over mission time no doubt recycling is done, but at an energy cost - so more H2/O2 for the fuel cell, etc. Vaguely recalling here that only semi permanent orbiting platforms recycle the CO2 (Sabatier reaction?), short trip vehicles just capture it.

Edit: Turns out everybody captures at the moment, ISS plans to recycle in the future:
www1.nasa.gov/pdf/146558main_RecyclingEDA(final)%204_10_06.pdf

 

[signerror]

Doesn't burn more strongly? Pressure aside, I understood that the presence of N2 greatly reduces the ignition hazzard. That is, pure O2 at even 21% of STP is an extreme fire hazzard compared to 21/79 O2/N2 at STP.

No. When you have a fire extinguisher or welding gas that is compressed inert gases (like nitrogen), the point is that it has no oxygen, and it displaces atmospheric air. So the fire or weld is under an oxygen-depleted blanket, and hence stops combusting or oxidizing.

It's not the presence of N2; it's the absence of O2.

In a gas (at low pressure), there is no chemical effect in adding one gas to another - molecules are far apart and barely interact (ideal gas principle). This is the opposite of a liquid, where molecules are strongly interacting and a mixture of chemicals is not simply the sum of its parts - hence, e.g., azeotropes.

 

[mgb_phys]

Hmm. Ok thanks. So what was the cabin pressure w/ Apollo One?

For the fatel test it was 1.2Atm of pure 02 - the idea was to simulate the pressure differential in flight where it would be 0.2atm O2 inside and vacuum outside. Although the mechanical stress is the same - there is a big difference chemically between 0.2atm pure O2 and 1.2atm O2.

Later Apollo missions started at near air pressure (although oxygen rich to reduce the bends - about the same mix as a nitrox scuba dive) and reduced to 0.2atm pure O2 in flight.
It would be difficult to engineer a capsule that could take being at only 0.2atm on the pad - it would have to stand 80Kpa inward pressure on the ground and 20kPa outward in space.

Well the lift off stored gas must be 4x heavier w/ STP cabin atmosphere vs 21% STP. Over mission time no doubt recycling is done, but at an energy cost -

But you only have to lift the volume of N2 to fill the inside of the capsule (at 1kg/m^3) not enough to be consumed over the length of the flight.
You have to remove CO2 because it is toxic at far lower concentrations than the point you have to worry about loss of oxygen. It's not worth recycling CO2 because you generaly have lots of oxygen around - either from fuel cells in Apollo/Shuttle era or from splitting water in the solar powered ISS.

 

[Dale]

I would much prefer a manned base on the moon (go there and stay) over a manned mission to Mars (go there and come back). I think there would be more generally valuable spin-off technologies.

 

[russ_watters]

How is it different? NASA had been warned about using a 100% oxygen atmosphere. They ignored those warnings. The astronauts insisted that the vehicle doors have explosive bolts so they could escape in an emergency. NASA instead removed the explosive bolts. The astronauts burned to death because of decisions consciously made by NASA upper management.

In both cases, NASA upper management should have listened to the warnings from their engineers and astronauts, they should have had the cajones to stand up to extreme political pressure (the pressure to launch Challenger came direct from the White House; Reagan wanted to brag about the launch that evening in his state of the onion address), and they should have ignored the idiotic press. They didn't, and people died as a result.

Besides what was already said about the failure to properly weigh the warnings vs ignoring them, the 100% oxygen environment issue was only half of the problem: the fact that the test was run with the cabin pressure at 16 psi vs the 2 psi it has in flight was a risk that was just plain not recognized. Some materials (theh velcro) that barely even burn at 2 psi partial pressure oxygen are damn near explosive at 16 psi pp oxygen. The pressure issue was just plain missed. If someone had thought of the issue before, the plugs out test might still have been run at 16 psi, but maybe with compressed air instead of pure oxygen.

 

[jacksonpeeble]

Gosh.. you started out absurdly and then went into pure insanity.

1. Gravity is not that essential. Depends on how long the trip is.
2. Gee that's a pretty big unnecessary addition. Piping hot showers every day!
3. Yeah different propulsion method probably needed.
5(?). lol.. why would you need a craft of 200 people? Are you disconnected from reality! space elevators... 20 doctors... football fields.

Yeah i don't know how to respond to this post anymore.

1. We want to go to mars, we need to explore. Simple as that.
2. You don't need world crafts containing thousands of people for a simple one off mission. A hand full of people would do fine.
3. Its not a walk in the park.

Agreed. The original post reminds me of Star Trek. It was really sort of amusing; either the poster wasn't serious, or he/she isn't the most intelligent/thoughtful individual.

I disagree that we need to explore. We just want to. I'm all for it after we get out of our little economic situation.

 

[earamsey]

Well, I am thinking creating a vehicle and atomosphere to do science anywhere in the solar system that is reusable not just a extended camping trip ... geez what a waste that would be! I don't want Mars program to be another apollo failure take the time to do it right and end up with something truly useful that can be used to explore the solar system.

Remember the goal is to do science not just go there and leave behind some junk that'll surely get destroyed by Mars weathering anyways. Yes, the rovers been on Mars for a time but they are small and low to ground and I don't know if they have encountered and survived storms.

Why create what I suggested?
1.can be reused to travel anywhere in the solar system for very long extended periods of time and large enough to have space for real labs to conduct scientific study instead of having to weight untiil one returns to earth.
2.large number of people is for psychological reasons;
2A.a mission with 2 spocks and 2 scotties is not going to lead to any great discoveries and thus a waste of time.
2B.people will surely get injured exploring and you need facilities to cure them thus, you need doctors and enough such that if a few die some are left.
2C.provide enough people for a variety of socializations among the various ethnicities that are likely to occupy station.
3.Why gravity generator? This is a no brainer, animal physiology evolved under gravity; you'll need it even if you planned to halplessly drift to Mars in a tin can. Being able to create it for long duration missions is paramount; mission to jupitor or even pluto!
4.Why skin tight space suites, see http://www.physorg.com/news10683.html" , because you can't explore in those bulky cumbersome suites NASA uses and you'll not need them when exploring on surfaces of most celestial bodies. MITs solution gives scientists freedom and mobility needed to effectively conduct scientific field work.
5.Why the need to generator your own water? Hehehehe, another no brainer;
5A.Well, water is basic necessity of life.
5B.Can't work well if one doesn't feel good especially on long duration missions.
5C.It can be done so why not?
6.Space Elevator? Well, because falling to Mars is dangerous. A space elevator can slowly and but steadily lower people, supplies and equipment to surface.
7.GPS is needed so it is easy to find different places of interest quickly. redoplayable so it can be recovered and reused in other deep space missions.
8.poor sleeping habits in long duration space missions will surely lead to murder -- it's human nature to become mentally disabled with lack of sleep I dare you to find a human that can for your 2 year martian mission. All this will help provide a comfortable environment most can adjust too.

Other essential stuff I left out.
1.Need to fabricate parts from materials found in space using nano frabrication; the theoretical diamonoid type fabricator looks promising.
2.doppler system for Mars and other celesetial bodies with weather system. It is helpful to know when a mighty martian storm is headed near by so one has adquate time to take cover to not have this is a Lunacy Program not a Deep Space Science Program.
3.Structures that can widthstand fierce winds and storms of mars. Todate a NASA space structure will be ripped to shreads or tossed around the storm like a rag doll.
4.Clean living and work environment on station. No noise and no horrible smells. as is with IIS.
5.Filter out radition that causes one to see flashes and disturb their sleep.
6.little clubs where ppl can give little shows or plays --- why not? the size of the station I proposed will be very large and accommodating. -- Remember -- best science is done when one feels good and in heathy environment.

Again I reiterrate, if this sounds too fantastical then you should not be planning deep space missions because I fear current plans are nothing more than a one way trip to a grave yard.