Henry Spencer wrote:

In article ,
Phil Fraering pgf@AUTO wrote:
I think I'd want to switch from hybrid rockets to a liquid-fueled
system, but that's just my prejudices.

Hybrids are not an unreasonable choice. The one limitation, for an
operational vehicle, is that loading a new fuel grain -- inherently a
large, clumsy object -- is distinctly less convenient than just pouring
one more fluid into the appropriate tank, and that's going to slow down
turnaround.

Oh, not necessarily. The hybrid grains are inert solid objects... keep
'em stored in a rack. No power required for refrigeration; if the
spaceport power blacks out during the heat of the summer, your fuel
doesn;t go away. The guys who deal with the fuel do not need specail
cyrogen protection suits; spills of hydrocarbon fuels do not need to be
mopped up and leeched out of the ground prior to the contamination
reached groundwater.

Also, the fuel tanks will not need to be periodically cleaned out or
inspected; there will be little risk of dirty sediment building up and
clogging things. Plumbing lines, and associated maintenance, are cut in
half. Replacing a hydrid fuel grain could be, if designed right, the job
of two guys and ten minutes, using tools available at any Home Depot.
And in this case, these two guys can be relatively low-tech, and thus
lower pay and overhead than the several guys needed for RP-1 maintenance
(and certainly far cheaper than LH2 maintenance guys). Since the solid
fuel won't spill and is damned unlikely to catch fire, storage costs and
facility insurance rates *should* be lower.

While RP-1 fueling might be quicker, the other operational advantages
that the solid fuel grain provide could well make that the operationally
cheaper route to go. We are quite some distance from where spacecraft
are able to just pull into a gas station, tank up and go.

--
Scott Lowther, Engineer
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