Re: SSME vs. J2 / RS-68


"Ed Kyle" <edkyle99@xxxxxxxxxxx> wrote in message
news:1142888093.637178.13320@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Jeff Findley wrote:
<landings.geo@xxxxxxxxx> wrote in message
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So we have to ask, why is this better than using EELV's and EELV derived
vehicles? Why are we letting NASA design and build yet another launch
vehicle when it's looking like the EELV's aren't getting the business
they
need to keep their prices down?

One reason is that the EELVs are optimized for GTO
missions with two stages. To be used for LEO
missions, they would need to be redesigned quite
a bit. An optimized two-stage LEO launcher would
have a smaller first stage and a bigger second stage
than Delta IV or Atlas V. This would mean that
NASA would not be buying EELVs, but would instead
be paying bucks to develop an "EELV-derived"
launcher.

But that's my point. The shuttle derived vehicles NASA wishes to pursue are
becoming less and less shuttle derived. If the SSME is dropped completely
from both the stick and the SDHLV, and the SDHLV's first stage needs to be a
larger diameter than the ET (due to the lower ISP of the RS-68), then what's
the point? It will have no commonality at all with the EELV's so there is
no opportunity for cost savings.

However, an EELV, or an EELV derived vehicle, has more opportunities for
commonality and for cost savings.

Jeff
--
Remove icky phrase from email address to get a valid address.


.

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