Rüdiger Klaehn wrote:
Fred J. McCall wrote:

[snip]
:The Russians have been transferring storable hypergolic fuel and oxidizer
:from Progress tankers to their stations (including ISS) for years. NoEVA
r clumsy pressure fittings seem to be required for this to work.

Now you might want to look at the thrust developed and burn durations.
I don't see any of those vehicles going to the Moon, landing, and then
taking back off.

So let me get this straight:

scaling up from the several hundred kgs the russian progress routinely
transfers to the ISS http://www.russianspaceweb.com/progress.html to
the tens of tons required for a lunar mission is so complex that it
can't be possibly be finished until 2018.
No. The only reason for the current envisioned delay to 2018 is to
allow a funding delay in developing a SDHLV due to the perceived need
to continue funding shuttle until 2010.


But building a huge heavy lift vehicle out of shuttle components has
negible technological risk?

negligable on-orbit technical risk, especially compared to on-orbit
assembly and fuel transfer operations. If shuttle and ISS have proved
one thing, it's that on-orbit technical risk should be traded for
ground technical risk wherever possible.


Orbital propellant transfer of storable propellants and even mild
cryogens such as liquid oxygen and liquid methane is not that hard.

says you.

There are even materials which remain flexible at liquid oxygen
temperatures, so you could use a simple bladder system. It is just that
nobody has ever seriously tried to do it.

Probably because it's just so simple. simple is boring... ;-)

Tom