Excuses, Excuses
Jun 12th, 2009 by Jonathan Goff
Sorry guys, I said I’d post the second half of that thought today (the one about how to use dual-launched EELVs for manned missions). But I’m exhausted. Been doing far too many cycles of stay up till 1am, then get up at 6:30 or 7am over the past two weeks. I’m going to bed. Hopefully I can get my thoughts written up tomorrow. Sorry.
Jon,
Sleep. That helps you stay safer at your industrial site.
The blog can wait.
A fascinating thought from NSF . . .
What would the Delta IV numbers be if they switched to a pair of SSME rather than the RS-68?
Has anyone ever looked closely into whether RS-68 truly offers more economical performance?
Bill,
I’m sure the performance would improve a bit…but man, that would be expensive. I don’t believe for a second that switching to SSMEs would make Delta-IV more economical.
~Jon
What would get reused? The tanks? It would no longer be a Delta IV.
Actually, the question is whether the SSME (if produced in quantity) truly is as expensive as urban legend supposes.
SSME is just “too expensive” kinda has a “known fact” quality to it that just might not be true.
Bill,
I’d really believe that an engine running as close to the edge as the SSME would be more expensive than an RS-68. Even if DIRECT were around, and even if their magical SSME costs came into being, two SSMEs are still going to be substantially more expensive than one RS-68. And I don’t think the added performance would make up for it–though I might be wrong.
~Jon
Well, there *is* the whole “system” aspect that has to be considered. If SSME enables a mission with existing (or lightly modified) hardware, and RS-68 requires a significant increase in changes over SSME, then the engine expense is just one element.
This, at least, is what I understand the DIRECT folks’ argument to be regarding RS-68 vs. SSME.