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Posted: Sun Jun 06, 2010 9:27 am
by Smivs
Ahruman wrote:
You still have to launch all of it, in relatively tight launch windows (which come about two years apart).
By sending the descent/ascent module separately, you can send it within reason when you like. As it's un-manned it doesn't matter if it takes an age to get there, as long as it's there before the manned module arrives. With a long timescale like this for a Mars mission, you can spread the effort over time, and even ensure the 'Lander' is safely in Mars orbit before the manned module even sets off.
Posted: Sun Jun 06, 2010 5:47 pm
by Chrisfs
Ahruman wrote:Killer Wolf wrote:aye, why the return = harder bit.
The hardest part of an interplanetary flight is the first couple of hundred kilometres, getting off the planet.
For a return trip from Mars, you need to bring the rocket for that plus the launch facility with you.
This increases the mass of your initial launch by a factor of, say, 50.
You don't really need a launch facility, just a flat area and a ship that can lift off again. Fuel would be the biggest problem.
It worked with the Moon. Gravity on Mars is 38% of Earth which is about twice of that on the Moon. So in that respect, it would be easier to take off from Mars than from Earth.
Posted: Sun Jun 06, 2010 6:23 pm
by JensAyton
Chrisfs wrote:You don't really need a launch facility, just a flat area and a ship that can lift off again.
By “launch facility”, I don’t mean Cape Canaveral. Just a predictable launch surface – like the Apollo descent module.
Chrisfs wrote:Gravity on Mars is 38% of Earth which is about twice of that on the Moon.
Atmospheric drag is not negligible.
And yes, it’s easier than launching from Earth. If it wasn’t, no-one would even be considering it.