There are many benefits, some of which are critical, for SSTO. Given
multiple engines (16+, say), it allows differential throttling, which
eliminates the need for any gimballing. Assuming your mass fraction
is about 95%, upon landing you could shut down 12 of the engines, and
throttle down the remaining 4 engines for landing/manuvering.
Assuming your engines are capable of some excess thrust, you would
be able to shut down a bad engine, and its counterpart, and throttle
up the remaining 14 engines to compensate.
The key to making use of these benefits will be making the T/W of
the smaller engines comparable to a few larger ones.
Back to the original post - there is really no benefit to multiple
catpack chambers - the area of the catpack is fixed somewhat by
the thrust needed and catpack life desired. Anything with multiple
catpack chambers would just add to the weight of the engine.
Dan
In a message dated 7/31/02 8:56:32 AM, [EMAIL PROTECTED] writes:
<< I'm no expert at this but I would guess that while it may be easier/cheaper
to build lots of small engines the maintenance hassle must be humongous.
It's tough enough to keep the shuttle space worthy with only 3 main engines.
If it has 10 or more it must be even tougher. More turbo pumps more fuel
lines to get cracks. More engines to gimbal.
I understand John's comment on how economy of scale already becomes relevant
when designing Armadillo's craft. On the other hand as I remember the goal
is to create a quickly re-usable vehicle. In that case the ability to
quickly inspect and repair a vehicle may proove to be cheaper in the long
term when the initial investment in fewer, larger engines is made.
I'll admit that I have no figures to back this up but it seems reasonable to
me. Thoughts?
Sander >>
_______________________________________________
ERPS-list mailing list
[EMAIL PROTECTED]
http://lists.erps.org/mailman/listinfo/erps-list
