In article ,
ed kyle wrote:
On the other hand, the [GD] plan's still-to-be-proven
long-term use of hydrogen fuel for lander and Earth
return propulsion, a key element for making this all
work, represents an unknown program risk.

There's no great issue with a hydrogen-fueled lander. There were serious
plans for such as Apollo followons. Hanging onto adequate amounts of
hydrogen for 2-3 days in space is not a big trick.

Using hydrogen for return propulsion, on the other hand, is a bit iffy.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |