
How Will We Get Off Mars? - pmcpinto
http://news.nationalgeographic.com/2015/10/151002-mars-mission-nasa-return-space/
======
lisper
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.

~~~
Nadya
_> 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.

~~~
mattstreet
Why is that such a priority for people? Why can't we just worry about taking
better care of the people we have NOW?

~~~
Nadya
We could treat everyone like millionaires and that wouldn't make an ounce of
difference to anyone if our entire species went extinct. Absolutely no
treatment we can give to one another prevents a catastrophic event from wiping
us all out.

A catastrophic event isn't going to stop and think "Oh hey, humans are
treating each other nicely. Maybe I shouldn't wipe them all out?"

~~~
Pinckney
Why is the perpetuation of Homo Sapiens a moral imperative?

~~~
Nadya
Why is being nice to others a moral imperative? In fact - why should _any_
decision be based off morals?

The continuation and survival of the human race is the top priority among a
large population of people. Some contribute by researching new medicines (Why
do this?), others improve quality of life for others (Why do this?), others
have children (Why do this?), and others look for a way to get us away from a
potentially doomed planet in case of disaster scenarios. They all have the
same reasoning - just different methods.

Morals are subjective to a population. The majority population of humanity has
decided that continuation of "us" is a "good thing".

Of course, one could argue things would be better off if humanity went
extinct. But that isn't in humanities' best interests (read: survival), so
people generally wouldn't agree with you.

~~~
Pinckney
"The continuation and survival of the human race is the top priority among a
large population of people. Some contribute by researching new medicines (Why
do this?), others improve quality of life for others (Why do this?), others
have children (Why do this?), and others look for a way to get us away from a
potentially doomed planet in case of disaster scenarios."

The vast majority of medical research goes to diseases that pose no
existential threat to Homo Sapiens. Even Malaria, which kills upwards of
500,000/yr, does not pose any existential threat. Late-life diseases such as
alzheimers have no effect whatsoever on Homo Sapiens, yet receive substantial
funding. No, medical research largely serves to decrease human suffering, a
goal which I do regard as noble.

Likewise, why does increasing quality of life matter? Humans will continue to
reproduce even in conditions of abject poverty. What does quality of life have
to do with anything? (You, after all, seem to think putting humans in a thin
metal tube and hurling them through space to live out their life on a cold,
barren rock is important. Surely you don't think this would increase their
quality of life).

As for children, I have no clue what people see in them. But they seem to
reproduce because having children makes them happy, not out of some perceived
obligation to Homo Sapiens.

My point isn't that you need to share my morals. My point is that you should
acknowledge your morals are not universal.

------
arrrg
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
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
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.

------
ams6110
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
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
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
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/as...](http://science.nasa.gov/science-news/science-at-
nasa/2001/ast02aug_1/)

~~~
jerf
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.

------
jackgavigan
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
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
_> ..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
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
I know what you meant to say by "unlikely anything baring the Falcon name will
ever leave low earth orbit", but note that the Falcon 9 upper stage drops off
the satellite in Geostationary Transfer Orbit (GTO) for every geosynch launch.
Presumably DSCOVR's launch to L1 also involved some kind of not-low transfer
orbit. And the 2nd Falcon heavy launch is planned to send the upper stage to
much higher than LEO, where it will drop off a variety of small satellites,
including Lightsail-B.

[https://en.wikipedia.org/wiki/Geostationary_transfer_orbit](https://en.wikipedia.org/wiki/Geostationary_transfer_orbit)

------
theophrastus
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
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.

------
outworlder
> 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.

------
pnut
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
Sounds similar enough to some bus rides I've taken across Asia.

------
madaxe_again
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_Orion_\(nuclear_propulsion\))

[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)

~~~
Armisael16
The hardest part of any Mars flight is simply getting from Earth's surface to
LEO. That step literally costs more delta-v than the rest of the mission
combined, and nuclear rockets really aren't up to that challenge - NTRs don't
have the TWR, and I don't really think Orion needs explaining on that front.

The other thing is that we can get to Mars with chemical rockets. Using an NTR
wouldn't make the journey meaningfully faster - we'd just bring a larger
payload - and while I'm sure that almost everyone would rather triple engine
Isp, personally I'd rather just go to Mars already instead of waiting for
another couple decades.

If we do start spreading out into space, the vast majority of our early trips
will be to the moon or to Mars. Don't overengineer the problem - an cheap and
adequate rocket now is better than an excellent rocket later.

------
glibgil
Stroke its pole.

