Re: EELVs Are A Bad Deal

From: Will McLean (mclean1382_at_aol.com)
Date: 02/09/05 

Date: 8 Feb 2005 18:41:03 -0800

Alex Terrell wrote:
> Interesting quote: Griffin also said that ... he takes a 'dim view'
of
> approaches that would rely on orbital staging and assembly
operations,"
> and how he doesn't "'think EELV is a competitive option...'"
>
> What does he mean by "orbital assembly". This implies astronauts
going
> out and doing complex building stuff. All that would be needed is for
> two vehicles to dock and head off. Docking is hardly complex - these
> days you wouldn't even need any solid data links.

In fairness to Griffin, it isn't quite that simple. Just docking two
stock EELVs gives you a fairly limited mass in Lunar orbit.

More than two launches, and you have to worry more and more about the
tradeoff between boiloff and being able to launch several vehicles
reliably in a narrow timeframe, and a space tug or some other way to
get them together.

There are ways to work around that, but they start to get further from
"just docking and heading off"

I suspect you want a combination of upgraded EELV and orbital assembly.
Your first EELV upgrade step is probably more powerful propulsion on
the upper stage. Fortunately, you want something very similar for the
TLI stage anyway.

If you can transfer LOX in orbit with tranferring the whole tank,
things get simpler, but that hasn't been demonstrated yet.

So, if you upgrade both EELvs to 30 tonnes or more to LEO, you can do
it in three launches. The first two send up two full LOX tanks, and a
space tug collects them at an austere depot, with a truss, attitude
control, and sun and earthshades. The third sends up a CEV, full LH
tank and engines.

Dock the CEV forward, the rest aft, tap the tanks and go.

This is considerably more complicated than sending the whole stack on a
shuttle-derived HLV. I think the complication is worth it, to get a
higher flight rate, and, at least as important, the redundancy of at
least two different launch systems. But I can appreciate the contrary
view.

I think an early attempt to demonstrate orbital LOX transfer would be a
really good investment, one way or the other.

Will McLean

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