How Will We Get Off Mars? • Hacker News Board

Re: How Will We Get Off Mars?

#21

Post by MrZongle2 » Tue, Oct 06, 2015, 4:01 PM UTC

pnut wrote: post #7

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.

"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.

Re: How Will We Get Off Mars?

#22

Post by madaxe_again » Tue, Oct 06, 2015, 4:05 PM UTC

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_propuls...

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/NERVA

https://en.wikipedia.org/wiki/Project_Timberwind

Re: How Will We Get Off Mars?

#23

Post by outworlder » Tue, Oct 06, 2015, 4:08 PM UTC

> 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.

Re: How Will We Get Off Mars?

#24

Post by baobabaobab » Tue, Oct 06, 2015, 4:09 PM UTC

scrumper wrote: post #17

arrrg wrote: post #9

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 be…

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 in…

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.

Re: How Will We Get Off Mars?

#25

Post by lisper » Tue, Oct 06, 2015, 4:11 PM UTC

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.

Re: How Will We Get Off Mars?

#26

Post by theophrastus » Tue, Oct 06, 2015, 4:15 PM UTC

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.

Re: How Will We Get Off Mars?

#27

Post by EC1 » Tue, Oct 06, 2015, 4:17 PM UTC

lisper wrote: post #25

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 se…

Yeah but colonizing Mars is just straight up cool.

Re: How Will We Get Off Mars?

#28

Post by lisper » Tue, Oct 06, 2015, 4:26 PM UTC

EC1 wrote: post #27

lisper wrote: post #25

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 se…

Yeah but colonizing Mars is just straight up cool.

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.

Re: How Will We Get Off Mars?

#29

Post by dimitriye98 » Tue, Oct 06, 2015, 4:31 PM UTC

lisper wrote: post #28

EC1 wrote: post #27

Earlier quoted context omitted.

Yeah but colonizing Mars is just straight up cool.

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.

Well, if we get a self-sufficient mars colony up, nuking ourselves will become survivable.

Re: How Will We Get Off Mars?

#30

Post by Nadya » Tue, Oct 06, 2015, 4:32 PM UTC

lisper wrote: post #25

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 se…

>if we're going to think seriously about colonizing Mars, we ought to think seriously about colonizing the arctic and antarctic first.

And with this you completely miss the reason why we need to colonize away from our planet.

What if a catastrophic event completely destroyed all life on Earth - the poles included? All of humanity. Wiped out in a single event. Getting people onto Mars is the first step to making sure humans can continue to exist in such an event.