Pat Flannery wrote:

Is there any breakdown regarding how many of those are related to
orbiter inspection, TPS repair, and SSME (I assume that the cargo
version wouldn't use SSMEs, but rather expendable RS-68s for the sake of
economy and system simplicity) postflight checkout and maintenance?


Assuming that the shuttle goes away in 2010, there shouldn't be any
objection to using the remaining inventory of SSMEs as expendables for a
heavy lift vehicle.

Leaving aside the six that have been lost in flight, there seem to be
about 40 engines in the inventory (2005 through 2109), most of which
have fewer than 10 flights. Even omitting the workhorse engines (i.e.,
2012 with 22 flights), sufficient engines remain for several flights of
a shuttle-derived heavy lifter. (I get my numbers from the available
vehicle descriptions in press kits -- STS-108 omitted that info for some
reason).

Of course, the engines would be a mix of base, Block I, Block II, etc --
but if overall performance is an issue, either mix similar engines in
the same cluster or design the flights around the nominal thrust levels
for the least-capable engine (i.e., use 100% if the flight includes a
base engine, 104% if the worst engine is a Block I).

They're bought & paid for, and their only other use is as expensive
paperweights in a few museums. It would actually be *more* expensive to
replace them with RS-68s, since they'd have to be purchased (assuming
that the SSMEs have been stored in reasonably controlled conditions).

--
Reed Snellenberger
GPG KeyID: 5A978843
rsnellenberger-at-houston.rr.com