Re: Ares alternatives? "NASA renegades"


"Jochem Huhmann" <joh@xxxxxxx> wrote in message
news:m2mydw5e3m.fsf@xxxxxxxxxxxxxxxxxxxx
"Jeff Findley" <jeff.findley@xxxxxxxxxxxxxx> writes:

I'm still not getting how you want to get lunar or Mars landers on their
way with EELV's. Sewing 10-15 ton modules together into a Mars lander
seems not exactly easy, especially if alone the heatshield won't fit
under the payload shroud in one piece. Fuel is important, but it's not
everything.

There is no law of physics that says heat shields need to be one piece.
The
shuttle, for example, has a few openings in the base of its heat shield
for
the landing gear, LOX and LH2 lines to the ET, and etc. Also, a Gemini
capsule was re-flown as part of the MOL program and it had a hatch in it.
It worked just fine too.

There's no law of physics that say heat shields need to be one piece,
right. But assembling such a lander (structure, heatshield and all) from
rather tiny chunks is a nightmare. You can't just easily dock together
things for that. You'll need a crew and do rather delicate work for that
and then you'll need to have even more launches. Look at how many
launches and EVA hours the ISS has needed and then show me how you
assemble a Mars craft this way. And then even without the Shuttle (which
at least has the crew already with it) and without the crew on the
station... no way.

Then I guess it would be impossible to assemble a large space station truss,
solar arrays, and radiators which are launched in pieces. No wait, it's
already been done on ISS.

How many launches of EELV's for pieces and assembly crews you're
thinking of here? 100? 200?

No, are you insane? The assembly flights really aren't that bad. Most of
them would involve docking or berthing modules together the way Mir and ISS
were assembled. The heat shield for the mars lander would be the biggest
challenge.

This is especially true since we do not yet know how to land large landers
on Mars. This is something that has not been done yet. Since it's not been
done yet, how do you know that Ares V would be big enough to launch the
required heat shield in one piece? The answer is you don't and even NASA
doesn't know. Might as well bite the bullet and start planning on missions
which require some form of LEO assembly and in orbit refueling.

Even with Ares V, a Mars mission is going to need to be assembled in LEO
from many launches. The bulk of that mass is fuel and oxidizer for the
engines, so a LEO fuel depot makes a lot of sense to develop.

I have nothing against fuel depots and in-orbit assembly. But I think
that current EELV's are just too small to deliver useful pieces of such
crafts, both mass- and size-wise. 60 to 100 tons of payload and 8 to
10 meters payload diameter makes all of this at least an order of
magnitude easier and this is easily worth a new launcher.

Note that your "feelings" would have prevented the building of ISS.

Jeff
--
"Many things that were acceptable in 1958 are no longer acceptable today.
My own standards have changed too." -- Freeman Dyson


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Relevant Pages

  • Re: Ares alternatives? "NASA renegades"
    ... The heat shield for the mars lander would be the biggest ... OK, but how many launches ... Another new technology if we have a propellant depot could possibly be ... cost, and that cost will be huge, leading to the same "been there, ...
    (sci.space.shuttle)
  • Re: Space Policy: Why Mars should be our top priority.
    ... V's to assemble it in LEO; but those launches would probably have cost less than a Shuttle launch on average, and we've done over a hundred of those. ... You'd need to launch 10-20 Saturn Vs probably within a 1 year period. ...
    (sci.space.policy)
  • Re: Ares alternatives? "NASA renegades"
    ... them would involve docking or berthing modules together the way Mir and ISS ... but how many launches and how long does it take to assemble the ... eat into every single payload. ...
    (sci.space.shuttle)
  • Re: Ares alternatives? "NASA renegades"
    ... and then you'll need to have even more launches. ... at least has the crew already with it) and without the crew on the ... Then I guess it would be impossible to assemble a large space station truss, ...
    (sci.space.shuttle)