On 12/27/2015 11:13 AM, David Weinshenker wrote:
On 12/25/2015 09:25 PM, Henry Spencer wrote:
Why not go for more powerful liquid motors or more of them instead...
Because the US has no suitable large liquid engines. The RS-27A is out
of production and too small, the RS-68 uses the wrong fuel for
high-thrust first-stage engines, and that was basically it for
off-the-shelf engines. And there is reason to fear the cost and schedule
impact of having MSFC and Rocketdyne develop a big new engine.
In other words, we've (post-SSME) let our design pipeline for large
booster engines run dry, to the extent that any new effort along those
lines would effectively be starting from scratch (and therefore looks
like a "long pole in the tent" in the context of near-term launch
vehicle proposals.)
Or put another way, once you have an incoming launch vehicle
requirement, it may be too late - especially in the context
of the compressed budget and schedule expectations which seem
to be the "modern" fashion - to initiate an applicable engine
development project. (Note that the F-1 work began well before
anything resembling the Saturn/Apollo launch configuration, as
such, had been explicitly specified - but it was foreseen that
lunar missions might be proposed, and it could be anticipated
that these would require large launch vehicles and new high-
thrust engines.)