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

[mheslep]

Seven of the prior flights had shown erosion or blow-by of the o-rings. Those events were rationalized into a gauge of robustness of the o-rings, when they were not designed to suffer any erosion. Then the engineers did not get the point across that the events were highly correlated with temperature.
Pages 22,23
http://www.soc.washington.edu/users/bpettit/soc506/tufte.pdf

 

[turbo]

In mechanical seal applications in industry it is common to use convoluted machining (Labyrinth seals) to engineer passive pressure-drops so that the primary seals (O-rings in this case) are not subject to the entire pressure differential. The solid-booster joints appear to be very simple, which probably ensures the re-usability of the components, possibly at the risk of primary seal failure.

 

[Coin]

"Why are you standing on the toilet?"
"Because it's there!"

*suspicious* how did you know what i was doing this weekend??!

 

[turbo]

*suspicious* how did you know what i was doing this weekend??!

Not much of a weekend! Nothing else to do?

 

[Enjoicube]

I'm no longer interested to see NASA spend my tax dollars to send people to the top of the mountain just for the sake of looking down. Let them send robots till their heart's content, but I don't trust them to send people any more.

Really? Curiosity never motivated you? I suppose manned missions are not as important to me, but still, think about where some of your money is already going. Meanwhile, a significant amount of my money is going to college sports, which reflect nothing I am interested in.

 

[elect_eng]

Really? Curiosity never motivated you?

Curiosity motivates me every day. NASA missions even had a role in my love of science growing up, since I was born in 1964. I vividly remember Apollo 13 and followed and understood what was happening since my Father (who was an Air Force pilot and a Physics major) explained it to me. What a great lesson to see humans exploring and risking their lives to discover and learn and then to overcome challenges and survive against the odds. Can you imagine how crushing it was to see the Challenger disaster and later find that it was unnecessary and ultimately a result of politics and mismanagement. I've lost faith in the modern day NASA and don't think any plan they have to put people on Mars is likely to be that important, and could be tragic.

I do think that the NASA robot explorers are very useful, despite the high failure rate in those missions. Note that cutting corners and trading risk for dollars is acceptable with robots, but not with humans.

I suppose manned missions are not as important to me, but still, think about where some of your money is already going.

OK, now I'm really depressed.

Meanwhile, a significant amount of my money is going to college sports, which reflect nothing I am interested in.

I played many sports growing up and found athletic training and competition educational and healthy for mind, body and spirit.

It's interesting you brought up sports because, in college, I rowed (crew) and remember that some rowers from Univ. of New Hampshire died in a tragic accident on the water (mid 1980's). A boat swamped and the cold water caused several people to lose their rational and try to swim to shore. This resulted in implemented changes adopted by all University crews to train people better. We were told to literally hold hands and not allow anyone to leave the boat - just wait for help. I never once thought that sports should be abolished because of this type of accident. However, if I found out that a football team tried to save money and bought fragile helmets which resulted in a death, I would never trust that organization again.

 

[MissSilvy]

Hm, I hope the OP isn't a scientist. He'd only be doing the thoroughly documented, explored and completely safe research.

If someone wants to go to Mars and are willing to put their 'sacred human life' at risk, so be it. History and advances are not made by people who are only willing to experiment and explore when they have 'comfortable spacesuits' and a 'fun room' in the space station. You're welcome to feel however you like but the scientific community at large is also welcome to not take you seriously. At all.

 

[Enjoicube]

I played many sports growing up and found athletic training and competition educational and healthy for mind, body and spirit.

Certainly sports are good when being played by all, and in no way would I support taking phys-ed out. However, tonight I have to survive through 50,000 people asking me about "the game" which I know nothing about. I glanced at the student newspaper today; it will cost from $150,000 to $200,000 to clean up for the "riots" that are expected to happen if we win (if we lose I am even more afraid). In no way is it rational to support a sport where less than %.01 of the university plays in the game, but costs enough money to renovate the Math building. Sorry if I came off as a bit sour the first time, I am currently forced to hide in my room to avoid these idiotic riots.

 

[elect_eng]

Sorry if I came off as a bit sour the first time, I am currently forced to hide in my room to avoid these idiotic riots.

No, I didn't think that at all. It's interesting conversation, and there is no simple answer in these cases.

 

[Enjoicube]

Ahh, I think I better understand your first quote right now. I do agree that space travel is a very risky propostion right now; this reminds me about Feynmans comment about the failure rate of spacecraft , which he estimated 1 in 100 (sadly, this seems to be true). Perhaps I was quick to judge there; you were talking about the agency that should carry out these plans, I was talking about whether these plans should be carried out. I am also a little quick to this argument because of the number of people I know who are more curious about their dinner than astronomy (although you might be hard pressed to find such people on these fora).
What advantages would we get by sending a human to Mars? Even if it did work properly, perhaps we would get a much needed morale boost, but I think even a mission to the moon could do that.
Personally, I am looking forward to any future missions and developments. Perhaps even I do not agree with a manned mission to Mars, as with that amount of money we could study both Mars and Jupiter with well equipped probes.

 

[russ_watters]

I thought it had happened before, at least in that exhaust had partially burnt through the joint (or just the O-ring/sealing putty). But the attitude was - that didn't cause the shuttle to crash so it's not a problem.

I read through the wiki I posted: the previously noted problem was similar, but not exactly the same as what took down the Challenger. There was no leakage or destruction of the O-rings previously. The critical difference between the Challenger and what happened previously was the temperature at launch time changed the performance of the O-ring and that difference was clearly understood at the time.

Prior to that, the O-ring was performing in a sub-optimal way that was not as originally intended (and yes, should have been fixed), but the issue was well enough understood (at least by the engineers...) that the risk was manageable.

Rather like the debris impact/lost tiles a few years later.
I think that's a more serious failing than launching outside the official temperature spec of a component.

Well the Columbia problem was an exact repeat scenario that differed only in magnitude.

For the Columbia we have: 'If this problem gets a lot worse, it could destroy the shuttle' and predicting that was difficult
For Challenger, it was: 'If this problem happens, it could destroy the shuttle' and predicting that was essentially a experimentally proven.

1>My brakes failed on the drive home.
2>Did you have an accident
1>No I was going slow on a flat road
2>Ok, brake failure isn't a critical fault!

No, it's more like:
Columbia:
1>My brake pressure was low on the drive home.
2>Did you have an accident
1>No I was going slow on a flat road
2>Ok, brake failure isn't a critical fault! [This conclusion turned out to be wrong, of course, but it wasn't that unreasonable of a conclusion at the time, given the available evidence.]

Challenger:
1>My brakes failed completely - should I drive home? It might cause an accident. Last time I drove home and the brake pressure was low, but I didn't have an accident.
2>Um, are you suicidal?

 

[russ_watters]

Then the engineers did not get the point across that the events were highly correlated with temperature.

Being an engineer who deals with this problem on an almost daily basis, I would say that the fault is not with the engineers, the fault is an organizational structure that has mangers in place who do not understand engineering and will ignore the advice of the engineers based on that misunderstanding. Feynman in the wiki said this:

"It appears that there are enormous differences of opinion as to the probability of a failure with loss of vehicle and of human life. The estimates range from roughly 1 in 100 to 1 in 100,000. The higher figures come from the working engineers, and the very low figures from management. What are the causes and consequences of this lack of agreement? … we could properly ask "What is the cause of management's fantastic faith in the machinery?"

Simplly put, the managers ignored the simple bullet point conclusion because they didn't understand the analysis and were openly hostile to conclusions they didn't like. Fortunately, in my line of work the people who I write reports for only read the bullet point conclusions (I put them in front of the report) and never get to the analysis! They still ignore the conclusions, but at least there isn't anything to argue about!

 

[russ_watters]

Really? Curiosity never motivated you?

Manned missions are not and never have been motivated primarily by curiosity. The lunar missions were motivated, quite simply, by the desire to plant a flag. It is cool that we did it, but our curiosity could [probably then, absolutely certainly now] have been better satisfied with robots.

 

[D H]

I wouldn't sweat this issue. We're not sending people to Mars. Bush announced the plan, then didn't fund it as a real project and future Presidents aren't bound by that. The project certainly will not survive Obama's first term.

The announcement didn't even survive the announcement. There is no plan to send people to Mars and there never has been.

This is rather different from the FAA/NTSB attitude of: This is a problem, therefore we assume it will causes crashes until we can prove it doesn't.

That isn't a fair comparison. How many test pilots died in help get the aviation industry to the state it is currently in?

This was not the same NASA that sent men to the moon; - not even close!

The NASA that sent people to the Moon was even more callous that the NASA that launched the Challenger and Columbia. Read up on the Apollo 1 fire.

NASA was at fault or the Apollo 1 fire, and for the Challenger disaster, and maybe even for Columbia. NASA has a long history of ignoring the safety concerns of the engineers who built NASA's machines and the astronauts who rode on them.

The blame goes a lot higher than NASA, however. Johnson wanted a successful Apollo program to get the public's eye off the Vietnam War. Reagan wanted something to brag about in his state of the union address. http://books.google.com/books?id=dO...9HABg&sa=X&oi=book_result&ct=result&resnum=2".

NASA learned some lessons after each disaster. One of the key recommendations of the Challenger commission was to terminate the Shuttle, post haste. NASA proceeded to do just that. They canceled the mission to restore the Shuttle and canceled the Shuttle program entirely after 2010. The mission to resuscitate Hubble was put back in the manifest due to political pressure, even though there is no safe haven in such a mission. The Florida congressional delegates are balking at the termination of the Shuttle program because canceling it years before CEV starts flying will mean that Florida will lose a lot of jobs. The Shuttle program has been extended for two more missions to the ISS (plus the restoration of the canceled Hubble mission).

With all that, putting people into space is inherently risky. The astronauts are after all sitting on top of a bomb, a very powerful bomb. The astronauts all know some risk is involved. NASA does pay incredible attention to risk, every day. NASA's goal is to reduce the risk to an acceptable level. They cannot minimize the risk; the only way to minimize the risk is to not fly at all. There will always be some risk if we are to continue flying people into space.

I'm no longer interested to see NASA spend my tax dollars to send people to the top of the mountain just for the sake of looking down. Let them send robots till their heart's content, but I don't trust them to send people any more.

Your heart is in the right place, but your mind isn't. Do you drive to work? Go out partying on weekends? Chase after wind women? All of these endeavors are incredibly risky. You accept these risks (probably without thinking much about them) because the alternative is to give up being human.

We send people into space because we are human. We want to explore the unknown, both because it is unknown and because doing so has enhanced us in many ways. We could stop spending all that money we do on space exploration because "we have so many problems down on the Earth." The paltry 0.6% of the federal budget spent on NASA will not end global warming, or end hunger, or end war.

We could, as some in the space science community fervently wish, stop spending money on sending humans into space and only send robots. That is not what would happen. Space science, without the added impetus that it is forging the way for human spaceflight, would wither and die. Without that impetus, space science cannot compete with other science and with the "myriad problems we have on the Earth." One former spacefaring country has performed this experiment with ending funding for human spaceflight. The space scientists in that country convinced their politicians to stop wasting money on sending humans into space. The politicians obliged, and went a step further: They stopped wasting money on sending anything into space. Great Britain's space budget, $350 million per year, makes NASA's budget look gargantuan.

 

[russ_watters]

The NASA that sent people to the Moon was even more callous that the NASA that launched the Challenger and Columbia. Read up on the Apollo 1 fire.

The conclusion may be true, but the example that you use to support it certainly is not. The Apollo 1 fire should have been predicted, but it wasn't, whereas the Challenger failure was predicted and was ignored and the Columbia failure had happened previously and was underestimated.

As some astronaut said in the aftermath: the Apollo 1 incident was caused by a failure of imagination, not a failure of will. There was no maliciousness or callousness. Heck, the driver was Kennedy's goal, so any callousness would have to be attributed to the political pressure to achieve the goal, not NASA's path laid out to meet it.

 

[Phrak]

Wasn't it Morton Thiokol who pronounced the Columbia shot within safety margins?

 

[mgb_phys]

Wasn't it Morton Thiokol who pronounced the Columbia shot within safety margins?

IIRC (and a quick flick through the Feynman book) - the launch was below the rated temperature for the motors so MT were in the clear. Their engineers (especially the ones working on the seals) said no but management didn't pass this on to Nasa. So although MT didn't exactly say yes, they didn't say no either - essentially allowing Nasa to launch.

I think the first Apollo fire was fundementally different. That was the early days of rockets, the risks were very high and everybody knew it. The Shuttle accidents were in an era when the risks were well known and there was a large organisation to control and manage them - it was this organisation that failed.

It's rather like the risks you might be prepared to take flying the first military jet, or the first carrier landing vs. the risk that are reasonable on a civil airliner.

 

[D H]

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.

 

[mgb_phys]

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.

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!

 

[mheslep]

Being an engineer who deals with this problem on an almost daily basis, I would say that the fault is not with the engineers, the fault is an organizational structure that has mangers in place who do not understand engineering and will ignore the advice of the engineers based on that misunderstanding. Feynman in the wiki said this: Simplly put, the managers ignored the simple bullet point conclusion because they didn't understand the analysis and were openly hostile to conclusions they didn't like. Fortunately, in my line of work the people who I write reports for only read the bullet point conclusions (I put them in front of the report) and never get to the analysis! They still ignore the conclusions, but at least there isn't anything to argue about!

I also deal with this issue continually as an engineer, and sometimes as a manager. Thiokol Management takes considerable blame on this one, but I also blame the engineers, especially on the subject of o-ring performance vs temperature. The engineering presentation on that topic was confusing and contradictory. An engineer can not simply say "don't launch below X degrees". He also must present a coherent argument as to how they reached that conclusion. In every engineering organization I've been associated with, there has always the bright, but flawed engineer: either over confident from inexperience, or some old timer that predicts doom from in and all changes over how they did 30 years ago, etc. The only way those responsible for the organization can not be held hostage by these biases is to insist on a review of the engineering basis. Although the engineering bottom line was correct in this case, their communication to management on the subject was poor: it included conflicting, distracting and irrelevant information. Good management, when receiving such information, should have been conservative (and pushed for better). Instead they took advantage of the confusion to indulge in recklessness.
Here's the presentation material again. Pages 16-22 point out the problems with the actual presentation; page 23 has an example graphic by Tufte showing how it could have been done: demonstrating dramatically how the o-rings were almost certain to fail in very cold temperatures.
http://www.soc.washington.edu/users/bpettit/soc506/tufte.pdf

 

[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.