On Tuesday, February 4, 2003, at 12:49 AM, David Weinshenker wrote:
As I said, I'm not sure how completely I agree with this, but it occurs to meHeavy return on its own need not be all that hard, particularly if you don't have major crossrange requirements, and aren't too fussy about a precise landing. A blunt body
that "heavy return" does seem to be one of the more difficult mission modes...
heavy lift, and manned lift and return, are comparatively easy by comparison.
(Apollo was heavy lift/manned return, but not heavy return...)
with ablative shield and parachutes+retrorockets ought to be enough to return most
payloads. You need a big transport vehicle to go pick it up, but that keeps complicated infrastructure on the ground, where it's easy to get at.
The Shuttle was a good design, given its mission: do everything with exactlyOn this point we disagree. Even given the mission (which was a bad one), shuttle
one spacecraft type.
was not a good choice. SRBs, particularly segmented SRBs, were a bad choice. LOX/hydrogen was a bad choice. Toxics in the OMS were a bad choice. The stack geometry looks like it may turn out to have been a bad choice. Hindsight is 20-20, but many of the shuttle's design compromises were criticized at the time, and the some of specific predictions made by those critics have turned out to be true. I'm not talking about outsiders like Easterbrook, but insiders who were involved in details of the design process. Right now I'm reading volume one of Heppenheimer's history of the shuttle, and it makes for some very interesting reading. The shuttle design process was so heavily politicized from the very beginning that it's a wonder they were able to come up with a flyable design that met all of the political and technical constraints. Unfortunately some of the design compromises required have had fatal consequences. Still, it's an impressive engineering achievement. Nothing I say about the political impact on the shuttle design can detract from the extraordinary engineering skill of the people who designed and built it.
This is somewhat orthogonal to the "manned vs. unmanned" question: It may wellOne can imagine a small ship intended to dock with a containerized landing module containing the heavy cargo. The container has support structure and protection for the cargo, along with a heat shield and braking rockets. The manned section has life support, OMS, instrumentation, etc. The pilot picks up the payload, lands it, and the container is then processed separately from the smaller ship, which is returned to orbit on either an expendable or in the payload bay of an RLV. The small ship need not
be better for the heavy cargo vehicles to be piloted, but it's likely to make
everything cheaper, safer, and more versatile if the big, fragile heavy-lander
isn't the prime option for personnel transport to and from orbit. (I envision
that one with a single seat, occupied by a pilot who might possibly be drawing
a "hazardous duty" bonus on his flight pay...)
have any TPS or even any ability to maneuver in the atmosphere independent of the container. The same ship could perform ferrying on orbit. In fact I'll go so far as to suggest that the one of the hallmarks of a spacefaring civilization is the use of a containerized transportation system (though not necessarily in the form I describe). There's no way spaceflight can be called routine if every payload is a custom job.
......Andrew
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