Re: travel to Mars

[Kent Betts]

"Rob Jenkins"
> If I understand it correctly, Mars gets as close as 50 million miles to the
> Earth. That is 200 times farther than the moon.

I for one would like to see NASA perform a manned orbital mission to Mars, for
no other reason than because it's there. This would take funds from unmanned
missions and would therefore actually run counter to maximizing science return
per dollar. The trip takes about six months. As far as I know, conventional
thrusters are currently the best option and are adequate to the task.

The tough part about a Mars mission is the manned landing and return. The
gravity of Mars is substantial. A manned orbital mission would encourage the
development of life support systems and increase public awareness of manned
space flight, while avoiding the costly and risky aspects of a landing.

[Dale]

On Wed, 23 Jul 2003 07:11:35 GMT, Doug... > wrote:

>> As long as you are orbiting Mars you might as well land on one of its
>> moons and collect samples.
>
>Yep, though you don't have to travel that far to get asteroid samples.
>And it wouldn't be so much a landing as a docking -- those rocks have
>such weak gravity fields that you could push your lander off of either of
>them with your arm muscles, I bet.

Then maybe it wouldn't need an ascent stage- just build it like
the Flintstone's car, with their legs sticking out the bottom :)

Dale

[OM]

On Wed, 23 Jul 2003 02:50:35 -0700, Dale > wrote:

>Then maybe it wouldn't need an ascent stage- just build it like
>the Flintstone's car, with their legs sticking out the bottom :)

"Well, Senator, I have to admit that perhaps we erred when we included
a large rack of spare ribs in the food selection for the lander..."


OM

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[JGDeRuvo]

Though I respect your POV, Kent, what's the point of traveling there
if you don't land there?! Imagine if Columbus or Amerigo Vespucci
(the true discoverer of America) sailed across the Atlantic, took a
look at it from the coast for a few weeks and said "okay boys, let's
go home!"

There is no point in risking lives to simply orbit the planet when
unmanned probes can get the job done cheaper.

But the landing ... living there ... the human experience comes into
play then.


"Kent Betts" > wrote in message >...
> "Rob Jenkins"
> > If I understand it correctly, Mars gets as close as 50 million miles to the
> > Earth. That is 200 times farther than the moon.
>
> I for one would like to see NASA perform a manned orbital mission to Mars, for
> no other reason than because it's there. This would take funds from unmanned
> missions and would therefore actually run counter to maximizing science return
> per dollar. The trip takes about six months. As far as I know, conventional
> thrusters are currently the best option and are adequate to the task.
>
> The tough part about a Mars mission is the manned landing and return. The
> gravity of Mars is substantial. A manned orbital mission would encourage the
> development of life support systems and increase public awareness of manned
> space flight, while avoiding the costly and risky aspects of a landing.

[Henry Spencer]

In article >,
Rob Jenkins > wrote:
>If I understand it correctly, Mars gets as close as 50 million miles to the
>Earth. That is 200 times farther than the moon.

Correct. But for interplanetary travel, distance is not the most
important part -- with current technologies, the main problems are gravity
and velocity, not distance. Climbing out to Mars's orbit against the
Sun's gravity, matching velocities with Mars once you get there, and then
the same in reverse to come back, are what eat fuel. The most economical
trips to Mars and back cover hundreds of millions of miles.

>In existing thought about
>travel to Mars, what is regarded as the
>most effective propulsion system and how fast can it go? What are the
>alternatives?

Depends on how you define "most effective".

The only system that is available off the shelf right now is chemical
rockets, which use an awful lot of fuel but are inexpensive and
well-understood. It's perfectly feasible to mount a reasonable Mars
expedition using chemical rockets, although it would require orbital
assembly (or equivalent) and it would be expensive. Making fuel for the
return trip at Mars, from Martian resources, helps buts adds its own
complications.

The major near-term alternative is nuclear rockets. They use less fuel,
reducing the total mass that has to be launched into Earth orbit to put
an expedition together. They have a number of problems, however, both
political and technical. (A sample technical problem is that they run
much better on liquid hydrogen than on anything else, and storing liquid
hydrogen long enough to use it for the return trip is problematic.)
The money that would have to be spent developing them arguably might be
better spent launching more chemical fuel into orbit. Fuel is cheap,
nuclear development projects are very expensive, and the performance
advantage to be had from near-term nuclear rockets is not huge.

Neither technology inherently has a speed advantage. Speed is much more a
matter of how much extra you are willing to spend, and how much payload
you are willing to sacrifice, to achieve shorter trip times. A Mars
mission with minimum cost and maximum payload spends nine months or so in
transit each way, plus a wait of over a year on Mars for a suitable return
opportunity (which may not be a disadvantage, since it gives you more time
for science and exploration).

>Also, what was the highest speed attained in TLI during Apollo?

All Apollo TLIs boosted the spacecraft to about 11km/s, that being what
the mission required. A Mars departure actually doesn't require a lot
more than that.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

[Scott Hedrick]

"Kent Betts" > wrote in message
...
> A manned orbital mission would have little purpose other than the
adventure.

Remote operation from Mars orbit is much easier than it is from Earth.
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