8 ms·

How Will We Get Off Mars?

69 points by pmcpinto 11y ago

ams6110 11y ago
I think the first humans on mars will go with the understanding that it's a one-way trip. And there will no doubt be people willing to sign on for that.
- jahnu 11y ago
  Not only that but I guess they will accept they won't be able to live for long there too. Radiation and muscle wasting due to low gravity being the top two problems and growing food. Not much chance of overcoming those obstacles in even the medium term, if ever.
  - vollmond 11y ago
    Is muscle wasting a significant issue? Mars does have gravity, the people will no doubt be doing some physical work, so it won't be as bad as in orbit. On top of that, if they have no plans for ever coming back to Earth, then is there a significant downside to at least some atrophy?
    - jahnu 11y ago
      It's true that exercise does limit the loss and I guess you are right that it won't matter if you stay there. I suppose we just don't have enough data to say one way or the other. Edit: an old Nasa article on the topic... http://science.nasa.gov/science-news/science-at-nasa/2001/ast02aug_1/ http://science.nasa.gov/science-news/science-at-nasa/2001/as...
      - jerf 11y ago
        Correct. We know some things about how bad zero gravity is, we do not know how bad microgravity is. Given that it's probably a range (one presumes that .98G is probably medically indistinguishable from 1G, one presumes .02G is very like 0G though perhaps not quite indistinguishable), it's probably fair to say we are comprehensively ignorant.
  - devit 11y ago
    I don't think seeing people deteriorate and die on Mars on TV/YouTube will be great advertising for Mars colonization efforts, so hopefully they will wait until surviving and returning is possible.
- astrowilliam 11y ago
  I think the first humans to go to the red planet will actually orbit and not touch down. They will stay in orbit and either pilot robots on the ground or study what happens to the body during long space flight. This will help future space faring people that visit Mars and beyond.
  - eljimmy 11y ago
    I don't know about that. I think that would be a pretty big waste of time and resources. We're already controlling robots on Mars from Earth and anything they would be wanting to test on the body could be done in Earth's orbit. I'm also fairly certain they're already quite knowledgeable regarding the effects of weak gravity on the human body.
    - chrisabrams 11y ago
      Yes, but the lag time between Mars orbit and Mars surface is far less than Earth surface and Mars surface.
- Mvandenbergh 11y ago
  Unless they're almost entirely self sufficient very early on, that means an open ended spending commitment by whoever is running the programme. You can't cancel the programme because the colonists will die.
pnut 11y ago
That MAV experience does not sound appealing at all. 43 hours, standing up, no food, no toilet, no sitting down, no stretching your limbs. Riding on top of a metal rocket. Surrounded by millions of miles of lethal void.
- jahnu 11y ago
  Sounds similar enough to some bus rides I've taken across Asia.
- MrZongle2 11y ago
  "That MAV experience does not sound appealing at all." I would have to agree, though once in orbit the standing up/sitting down thing doesn't matter as much as the stretching. I don't imagine the rest would bother the crew that much, as they had to deal with it just to get to Mars in the first place.
- phire 11y ago
  About 10min after takeoff there will be no gravity, so the seats are practically useless anyway. It's the pre-flight checks which will make the lack of seats a large issue, they need to be at the MAV at least 4 hours before launch and have the doors closed maybe an hour before takeoff (before that anyone not doing checks could sit in the rover)
jackgavigan 11y ago
It's only when you realise that getting off Mars is far more like getting off Earth than getting off the Moon, that the full rationale behind SpaceX's obsession with a re-usable launch vehicle rocket that can land itself, becomes apparent.
- mikepurvis 11y ago
  Is the assumption there that a Falcon 9 lands vertically and a Dragon (or equivalent) is the ascent vehicle? Still doesn't really address the business of manufacturing the fuel or getting it into the rocket. Nor, indeed, the matter of lifting a Dragon 60m into the air to integrate it back onto its launcher. So much Earth infrastructure we depend on for this stuff.
  - jackgavigan 11y ago
    > ..lifting a Dragon 60m into the air to integrate it back onto its launcher. Why would you need to do that? Why not land the Falcon (Edit: Actually, it might be a Raptor) with the Dragon already on top of it?
    - phire 11y ago
      Raptor is the engine. Though it's unlikely anything baring the Falcon name will ever leave low earth orbit, it's just too specialised for the job of leaving earth's surface. It's not even designed to stay in LEO, they go out of the way to make sure it falls back into earth's atmosphere within a orbit or two (often less than a single orbit). You want to design a new craft from the ground up with the job ascending from mars. Ideally to save weight you want the stage's rockets to be used as many times as possible: Mars ascent, Mars Landing, Potentially orbital manoeuvres to get from LEO to mars and maybe the final part of earth ascent. But making a rocket fire that many times requires the ability to refuel, perhaps even twice (both LEO and on mars). You also have to be confidant about re-igniting the engine that many times over 5+ years.
      - greglindahl 11y ago
arrrg 11y ago
I always thought that the Lunar Module† was the single coolest piece of technology of the Apollo program. (Sorry Saturn V, raw power doesn’t really do it for me and beyond that you are mostly … boring.) It’s such an astonishing accomplishment to build something so lightweight, so complex, so versatile in such a short amount of time. It’s astonishing that it came together at all. And worked! Every single time, even beyond what it was originally intended for (during Apollo 13). A hypothetical MAV would have a similar role during a Mars trip. Be this complex yet lightweight and versatile little thing, a rocket that can take off from another planet without all the fancy infrastructure we have on Earth. (Luckily Mars has still relatively low gravity. Imagine trying to take off from Venus with it’s atmosphere and Earth gravity and think of all the stuff we need on Earth to pull that off.) — † https://en.wikipedia.org/wiki/Apollo_Lunar_Module https://en.wikipedia.org/wiki/Apollo_Lunar_Module
- scrumper 11y ago
  I'd never thought about a favorite piece of Apollo tech, but you make a strong case: the LM is pretty amazing. The MAV will have to do all that and a lot more besides, and in a much bigger gravity well, and with an atmosphere, and for a multi-year period in an incredibly hostile, dusty environment. EDIT: Actually, I had a favorite - the F1 engine. I find the idea of needing an auxiliary gas generator rocket engine inside just to turn a fuel pump pretty amazing. Likely I'm a bit more impressed by raw power than you :)
  - baobabaobab 11y ago
    The gas generator is pretty standard in rocket engines, but yeah, it's hard to wrap your head around an engine with a 55,000 horsepower fuel pump.
- Mvandenbergh 11y ago
  The Lunar Module is the only real space-ship we've ever built. Everything else has been essentially designed around getting into or out of Earth's gravity and atmosphere.
glibgil 11y ago
Stroke its pole.
madaxe_again 11y ago
The whole single-purpose type solution that seems to consistently be proposed here bothers me. I mean, yes, I understand that one has to start somewhere, and that the conditions one would need to meet on other bodies would be radically different - but as an engineer "niche" solutions bother me, and type solutions are almost universally better. I fear that for as long as we un-necessarily bind ourselves to limited and massive chemical propellants, rocketry will remain forever an inefficient and expensive business. I fear our dreams of our future in space died with nuclear propulsion. Thermal nuclear rockets would be compact and could fuel up with pretty much any old crap, be it hydrogen, methane, co2, so long as it can be made cryonic and heated by fission to blast out of a nozzle. Irradiation can be made a not-huge problem by using shielded heat-exchangers. Adds mass, but not as much mass as solid or liquid fuels and oxidisers. Nuclear pulse propulsion is a more controversial proposition as it typically involves significantly irradiating wherever you go, but if you're dealing with non-atmospheric bodies, or bodies so utterly inhospitable that irradiating them isn't going to make a jot of difference, again, why not? Well, the why not commonly given is that if you lose a chemical rocket carrying a nuclear reactor you have a scope for fallout on earth, but then again, we fly RTGs, and if there aren't spaceborne nuclear launch platforms I'll eat my hat. Anyway. I really wish we would be brave enough to experiment with new tech, rather than incrementally improving existing tech. The horse is better than it was, to be sure, but it's still a horse. Some articles on this stuff if anyone fancies getting lost in a wiki-hole: https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls... https://en.wikipedia.org/wiki/Project_Pluto https://en.wikipedia.org/wiki/Project_Pluto (holy nuclear ramjet, batman) Progression of nuclear thermal rockets: https://en.wikipedia.org/wiki/Project_Rover https://en.wikipedia.org/wiki/Project_Rover https://en.wikipedia.org/wiki/NERVA https://en.wikipedia.org/wiki/NERVA https://en.wikipedia.org/wiki/Project_Timberwind https://en.wikipedia.org/wiki/Project_Timberwind
- prodmerc 11y ago
  yeah, for people who worry about Martian dust/sand not getting on Earth (still can't wrap my head around this one, it's not like it's going to do anything to Earth's ecosystem), I doubt they'd even consider anything other than proven traditional technology...
outworlder 11y ago
> Although hydrogen isn’t heavy, it requires large tanks for storage that would take up a lot of precious space. Is that the only problem? What about boil off? They don't touch that at all. EDIT: They do talk about boil off while being manufactured on mars, but not in transit.
lisper 11y ago
This is probably not going to be a very popular position but I'm going to say it anyway: there is no rational reason to bring a human back from Mars. In fact, there are precious few rational reasons to send a human to Mars to begin with. Robot technology has advanced to the point where they can do all the science better than we can. The only reason to send humans to Mars is to colonize, and if we're going to think seriously about colonizing Mars, we ought to think seriously about colonizing the arctic and antarctic first. Those are a whole lot more hospitable than Mars, and will continue to be a whole lot more hospitable than Mars even under worst-case climate change scenarios. In fact, maybe we ought to figure out how to get this planet to a sustainable steady-state before we start going around destroying another one. But either way, if you're going to land 18 tons of stuff on the surface it makes a whole lot more sense to make it 18 tons worth of permanent infrastructure than a one-time-use vehicle to get a handful of humans back to the home planet. Indulging our emotional need to not leave people behind gets awfully, awfully expensive.
- EC1 11y ago
  Yeah but colonizing Mars is just straight up cool.
  - lisper 11y ago
    Is it? Why? The truth is that Mars is a pretty miserable place for humans. It's cold. It's dry. It's dusty. I just came back from a trip to northern Canada, and it was a pretty bleak, desolate place, but it's a tropical paradise compared to Mars. So what makes Mars so cool? I really don't get it. The only thing I can imagine is that people think it's cool because they have no clue what it would really be like.
    - dimitriye98 11y ago
      Well, if we get a self-sufficient mars colony up, nuking ourselves will become survivable.
      - 11y ago
theophrastus 11y ago
Space elevators and lowered tethers await (nano-carbon?) materials of super tensile strength for a gravity well as deep as Earth's, but what materials are possible for 38% of that gravity on Mars? And/or, a partial 'rope trick' involving a lift balloon to raise a one person pod as high up as possible to where a hook could be lowered from an orbital vehicle to haul them up the rest of the way. It just seems that wenches are generally going to beat massively expended rocket fuel.
rjmunro 11y ago
Why do we have to send the whole ascent vehicle in advance? Why not just send the fuel tanks and some fuel making equipment, then use the cabin, life support, maybe even the rocket motors etc. from the descent vehicle to finish the craft? Going even further, if a combined descent/ascent vehicle could bring down empty fuel tanks, the fuel making equipment could stay on mars and make fuel to supply the next mission.

69 points by pmcpinto 11y ago

I think the first humans on mars will go with the understanding that it's a one-way trip. And there will no doubt be people willing to sign on for that.

jahnu 11y ago
Not only that but I guess they will accept they won't be able to live for long there too. Radiation and muscle wasting due to low gravity being the top two problems and growing food. Not much chance of overcoming those obstacles in even the medium term, if ever.
- vollmond 11y ago
  Is muscle wasting a significant issue? Mars does have gravity, the people will no doubt be doing some physical work, so it won't be as bad as in orbit. On top of that, if they have no plans for ever coming back to Earth, then is there a significant downside to at least some atrophy?
  - jahnu 11y ago
    It's true that exercise does limit the loss and I guess you are right that it won't matter if you stay there. I suppose we just don't have enough data to say one way or the other. Edit: an old Nasa article on the topic... http://science.nasa.gov/science-news/science-at-nasa/2001/ast02aug_1/ http://science.nasa.gov/science-news/science-at-nasa/2001/as...
    - jerf 11y ago
      Correct. We know some things about how bad zero gravity is, we do not know how bad microgravity is. Given that it's probably a range (one presumes that .98G is probably medically indistinguishable from 1G, one presumes .02G is very like 0G though perhaps not quite indistinguishable), it's probably fair to say we are comprehensively ignorant.
- devit 11y ago
  I don't think seeing people deteriorate and die on Mars on TV/YouTube will be great advertising for Mars colonization efforts, so hopefully they will wait until surviving and returning is possible.
astrowilliam 11y ago
I think the first humans to go to the red planet will actually orbit and not touch down. They will stay in orbit and either pilot robots on the ground or study what happens to the body during long space flight. This will help future space faring people that visit Mars and beyond.
- eljimmy 11y ago
  I don't know about that. I think that would be a pretty big waste of time and resources. We're already controlling robots on Mars from Earth and anything they would be wanting to test on the body could be done in Earth's orbit. I'm also fairly certain they're already quite knowledgeable regarding the effects of weak gravity on the human body.
  - chrisabrams 11y ago
    Yes, but the lag time between Mars orbit and Mars surface is far less than Earth surface and Mars surface.
Mvandenbergh 11y ago
Unless they're almost entirely self sufficient very early on, that means an open ended spending commitment by whoever is running the programme. You can't cancel the programme because the colonists will die.

pnut 11y ago

That MAV experience does not sound appealing at all. 43 hours, standing up, no food, no toilet, no sitting down, no stretching your limbs. Riding on top of a metal rocket. Surrounded by millions of miles of lethal void.

jahnu 11y ago
Sounds similar enough to some bus rides I've taken across Asia.
MrZongle2 11y ago
"That MAV experience does not sound appealing at all." I would have to agree, though once in orbit the standing up/sitting down thing doesn't matter as much as the stretching. I don't imagine the rest would bother the crew that much, as they had to deal with it just to get to Mars in the first place.
phire 11y ago
About 10min after takeoff there will be no gravity, so the seats are practically useless anyway. It's the pre-flight checks which will make the lack of seats a large issue, they need to be at the MAV at least 4 hours before launch and have the doors closed maybe an hour before takeoff (before that anyone not doing checks could sit in the rover)

jackgavigan 11y ago

It's only when you realise that getting off Mars is far more like getting off Earth than getting off the Moon, that the full rationale behind SpaceX's obsession with a re-usable launch vehicle rocket that can land itself, becomes apparent.

mikepurvis 11y ago
Is the assumption there that a Falcon 9 lands vertically and a Dragon (or equivalent) is the ascent vehicle? Still doesn't really address the business of manufacturing the fuel or getting it into the rocket. Nor, indeed, the matter of lifting a Dragon 60m into the air to integrate it back onto its launcher. So much Earth infrastructure we depend on for this stuff.
- jackgavigan 11y ago
  > ..lifting a Dragon 60m into the air to integrate it back onto its launcher. Why would you need to do that? Why not land the Falcon (Edit: Actually, it might be a Raptor) with the Dragon already on top of it?
  - phire 11y ago
    Raptor is the engine. Though it's unlikely anything baring the Falcon name will ever leave low earth orbit, it's just too specialised for the job of leaving earth's surface. It's not even designed to stay in LEO, they go out of the way to make sure it falls back into earth's atmosphere within a orbit or two (often less than a single orbit). You want to design a new craft from the ground up with the job ascending from mars. Ideally to save weight you want the stage's rockets to be used as many times as possible: Mars ascent, Mars Landing, Potentially orbital manoeuvres to get from LEO to mars and maybe the final part of earth ascent. But making a rocket fire that many times requires the ability to refuel, perhaps even twice (both LEO and on mars). You also have to be confidant about re-igniting the engine that many times over 5+ years.
    - greglindahl 11y ago

arrrg 11y ago

I always thought that the Lunar Module† was the single coolest piece of technology of the Apollo program. (Sorry Saturn V, raw power doesn’t really do it for me and beyond that you are mostly … boring.) It’s such an astonishing accomplishment to build something so lightweight, so complex, so versatile in such a short amount of time. It’s astonishing that it came together at all. And worked! Every single time, even beyond what it was originally intended for (during Apollo 13). A hypothetical MAV would have a similar role during a Mars trip. Be this complex yet lightweight and versatile little thing, a rocket that can take off from another planet without all the fancy infrastructure we have on Earth. (Luckily Mars has still relatively low gravity. Imagine trying to take off from Venus with it’s atmosphere and Earth gravity and think of all the stuff we need on Earth to pull that off.) — † https://en.wikipedia.org/wiki/Apollo_Lunar_Module https://en.wikipedia.org/wiki/Apollo_Lunar_Module

scrumper 11y ago
I'd never thought about a favorite piece of Apollo tech, but you make a strong case: the LM is pretty amazing. The MAV will have to do all that and a lot more besides, and in a much bigger gravity well, and with an atmosphere, and for a multi-year period in an incredibly hostile, dusty environment. EDIT: Actually, I had a favorite - the F1 engine. I find the idea of needing an auxiliary gas generator rocket engine inside just to turn a fuel pump pretty amazing. Likely I'm a bit more impressed by raw power than you :)
- baobabaobab 11y ago
  The gas generator is pretty standard in rocket engines, but yeah, it's hard to wrap your head around an engine with a 55,000 horsepower fuel pump.
Mvandenbergh 11y ago
The Lunar Module is the only real space-ship we've ever built. Everything else has been essentially designed around getting into or out of Earth's gravity and atmosphere.

glibgil 11y ago

Stroke its pole.

madaxe_again 11y ago

The whole single-purpose type solution that seems to consistently be proposed here bothers me. I mean, yes, I understand that one has to start somewhere, and that the conditions one would need to meet on other bodies would be radically different - but as an engineer "niche" solutions bother me, and type solutions are almost universally better. I fear that for as long as we un-necessarily bind ourselves to limited and massive chemical propellants, rocketry will remain forever an inefficient and expensive business. I fear our dreams of our future in space died with nuclear propulsion. Thermal nuclear rockets would be compact and could fuel up with pretty much any old crap, be it hydrogen, methane, co2, so long as it can be made cryonic and heated by fission to blast out of a nozzle. Irradiation can be made a not-huge problem by using shielded heat-exchangers. Adds mass, but not as much mass as solid or liquid fuels and oxidisers. Nuclear pulse propulsion is a more controversial proposition as it typically involves significantly irradiating wherever you go, but if you're dealing with non-atmospheric bodies, or bodies so utterly inhospitable that irradiating them isn't going to make a jot of difference, again, why not? Well, the why not commonly given is that if you lose a chemical rocket carrying a nuclear reactor you have a scope for fallout on earth, but then again, we fly RTGs, and if there aren't spaceborne nuclear launch platforms I'll eat my hat. Anyway. I really wish we would be brave enough to experiment with new tech, rather than incrementally improving existing tech. The horse is better than it was, to be sure, but it's still a horse. Some articles on this stuff if anyone fancies getting lost in a wiki-hole: https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls... https://en.wikipedia.org/wiki/Project_Pluto https://en.wikipedia.org/wiki/Project_Pluto (holy nuclear ramjet, batman) Progression of nuclear thermal rockets: https://en.wikipedia.org/wiki/Project_Rover https://en.wikipedia.org/wiki/Project_Rover https://en.wikipedia.org/wiki/NERVA https://en.wikipedia.org/wiki/NERVA https://en.wikipedia.org/wiki/Project_Timberwind https://en.wikipedia.org/wiki/Project_Timberwind

prodmerc 11y ago
yeah, for people who worry about Martian dust/sand not getting on Earth (still can't wrap my head around this one, it's not like it's going to do anything to Earth's ecosystem), I doubt they'd even consider anything other than proven traditional technology...

outworlder 11y ago

> Although hydrogen isn’t heavy, it requires large tanks for storage that would take up a lot of precious space. Is that the only problem? What about boil off? They don't touch that at all. EDIT: They do talk about boil off while being manufactured on mars, but not in transit.

lisper 11y ago

This is probably not going to be a very popular position but I'm going to say it anyway: there is no rational reason to bring a human back from Mars. In fact, there are precious few rational reasons to send a human to Mars to begin with. Robot technology has advanced to the point where they can do all the science better than we can. The only reason to send humans to Mars is to colonize, and if we're going to think seriously about colonizing Mars, we ought to think seriously about colonizing the arctic and antarctic first. Those are a whole lot more hospitable than Mars, and will continue to be a whole lot more hospitable than Mars even under worst-case climate change scenarios. In fact, maybe we ought to figure out how to get this planet to a sustainable steady-state before we start going around destroying another one. But either way, if you're going to land 18 tons of stuff on the surface it makes a whole lot more sense to make it 18 tons worth of permanent infrastructure than a one-time-use vehicle to get a handful of humans back to the home planet. Indulging our emotional need to not leave people behind gets awfully, awfully expensive.

EC1 11y ago
Yeah but colonizing Mars is just straight up cool.
- lisper 11y ago
  Is it? Why? The truth is that Mars is a pretty miserable place for humans. It's cold. It's dry. It's dusty. I just came back from a trip to northern Canada, and it was a pretty bleak, desolate place, but it's a tropical paradise compared to Mars. So what makes Mars so cool? I really don't get it. The only thing I can imagine is that people think it's cool because they have no clue what it would really be like.
  - dimitriye98 11y ago
    Well, if we get a self-sufficient mars colony up, nuking ourselves will become survivable.
    - 11y ago

theophrastus 11y ago

Space elevators and lowered tethers await (nano-carbon?) materials of super tensile strength for a gravity well as deep as Earth's, but what materials are possible for 38% of that gravity on Mars? And/or, a partial 'rope trick' involving a lift balloon to raise a one person pod as high up as possible to where a hook could be lowered from an orbital vehicle to haul them up the rest of the way. It just seems that wenches are generally going to beat massively expended rocket fuel.

rjmunro 11y ago

Why do we have to send the whole ascent vehicle in advance? Why not just send the fuel tanks and some fuel making equipment, then use the cabin, life support, maybe even the rocket motors etc. from the descent vehicle to finish the craft? Going even further, if a combined descent/ascent vehicle could bring down empty fuel tanks, the fuel making equipment could stay on mars and make fuel to supply the next mission.