Is it feasible to land on Mars and come back?

Presumably we'd use a nuclear reactor as the power source. Are we build a
generator that can produce a sufficently large amount of electricity without
a thermal reservoir to dump the waste heat?

Uzytkownik "Steen Eiler Jørgensen" napisal w
wiadomosci . ..
Chung Leong wrote:

It seems to me that the size of lander would be prohibitively large,
as the ascent module would need to carry enough fuel to enter into
Martian orbit. Compared to the Moon's, Mars' gravity is much
stronger. Mars also has an atmosphere, which means thermo-shieldings
on both the lander and the ascent module.

The return vehicle would be fairly large too, as it needs to carry
fuel for returning to Earth. In addition, it would carry the reentry
module and equipment for monitoring the Martian atmosphere. Even if
we use two launches, the rockets used to carry them into space would
be gargantuan.

Unless you utilize In-Situ Propellant Production. That's one of the main
points in Robert Zubrin's "Mars Direct"-plan.

Bring along some Hydrogen, which weighs next to nothing. Make it react
with
Mars' CO2-atmosphere, creating Methane and water (the Sabatier-reaction).
Electrolyze the water into Hydrogen, which is cycled back into the
reaction,
and Oxygen, which makes a great rocket fuel together with Methane.

--
Steen Eiler Jørgensen
"Time has resumed its shape. All is as it was before.
Many such journeys are possible. Let me be your gateway."

Henry Spencer wrote:
In article ,
Roy Smith wrote:

I assume by "reentry module", you mean, "reentry to Earth's atmosphere"?
If so, it's not really needed. The return vehicle could park itself in
Earth orbit and a shuttle (or other vehicle) could rendezvous with it to
get the cargo.

Unfortunately, decelerating *into* low Earth orbit is extremely expensive
in fuel. No, the return vehicle can't just "park itself" in LEO, not if
it has any ordinary propulsion system.

One strategy I've seen is to aerobrake and then do a circularising burn.
IRC the delta-v for that is about 0.7km/s- doable I think.

In article ,
Steen Eiler Jørgensen wrote:
Unfortunately, decelerating *into* low Earth orbit is extremely
expensive in fuel.

Unless you bring an aeroshell and use aerobraking.

Yes, that's workable, apart from some lingering technical uncertainties
(it's nothing like the gradual multi-pass aerobraking that's now fairly
standard, and there are real concerns about things like density variation
in the upper atmosphere).
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

Chung Leong wrote:

Presumably we'd use a nuclear reactor as the power source. Are we
build a generator that can produce a sufficently large amount of
electricity without a thermal reservoir to dump the waste heat?

It would be wonderful if we could use a nuclear reactor. But even though
it's technically possible, it's politically impossible, at least the next
100 years.

As for the thermal energi developed by the reactor, the hardware needs
heating, and excess heat can be dumped to the atmosphere. Yes, it's thin,
but it's there.

--
Steen Eiler Jørgensen
"Time has resumed its shape. All is as it was before.
Many such journeys are possible. Let me be your gateway."

In article ,
says...
Chung Leong wrote:

Presumably we'd use a nuclear reactor as the power source. Are we
build a generator that can produce a sufficently large amount of
electricity without a thermal reservoir to dump the waste heat?

It would be wonderful if we could use a nuclear reactor. But even though
it's technically possible, it's politically impossible, at least the next
100 years.

Not with this administration. NASA has a new nuclear initiative as of
last year. See: http://www.space.com/news/nasa_nuclear_020205.html.

Marc

"Sander Vesik" wrote in message
...
Chung Leong wrote:
Bar the development of some revolutionary technology, is it realistic to
think that we can land on Mars and come back?

Yes. All you really need is the willingness to spend a lot of money on
launching fuel tanks to LEO. strictly speaking, could have done decades
ago. Just nobody has been willing to cough up the money so far, either
for a brute force mission or otherwise.


Now that Falcon I can put 4500kg's into LEO for $6million it should be
financially doable.

"Steen Eiler Jørgensen" wrote:

It would be wonderful if we could use a nuclear reactor. But even though
it's technically possible, it's politically impossible, at least the next
100 years.

Not sure why you say that. We use nuclear plants for terrestrial power
generation, have nuclear power on space probes already (e.g. Cassini), and
of course numerous modern military ships use nuclear reactors. The US Navy
builds and operates huge numbers of ship-based nuclear plants.

- Xerxes