[extropy-chat] FWD [forteana] Re: Are dwarfs better for longduration spaceflight?]

[Adrian Tymes]

--- spike <spike66 at comcast.net> wrote:
> > "Terry W. Colvin" <fortean1 at mindspring.com> fnarded:
> > Designing for absolute minimum weight aerospace vehicles is fraught
> > with problems...
> 
> Granted, however we are discussing only *scaling* as a function
> of the needs of the astronaut.  This exercise is not about shaving
> close to the margin; the margin is the same for the smaller 
> vehicle as it is for the larger.

Actually, considering how small a fraction makes up the crew and crew
support - the "payload" - of any manned space vehicle to date...yes, we
are talking about shaving close to the margin.  Relative to, say,
making a more efficient propulsion method so we don't have to cram the
payload and vehicle structure into a few percent of the total vehicle
weight.

> My notion is that under these extreme conditions,

Getting to orbit already requires fairly extreme performance from the
rocket.  How 'bout we pursue technologies, like laser launch or mass
drivers (for cargo only) or nuclear engines (the ones with
nonradioactive exhaust, please) and so forth, that mitigate that
requirement instead?

> > ... While a measure of weight as saved, it made the vehicle
> > so difficult to manufacture that the cost increases by far
> outweighed
> > any operational savings...
> 
> Of course, but manufacturing constraints in aircraft,
> where you are making many, are not directly comparable
> to manufacturing constraints in spacecraft where you
> are making one or two.

If we're to make space access affordable, then spacecraft will likely
have to become at least as mass-produced as aircraft.  (Granted, 777s
don't have nearly the production volume of most things coming out of a
Ford plant, but the processes used to make the two - including the
existence of practical cost controls - are far similar than the
practices used to make most spacecraft today.)

Besides, even in a one-off/unique craft, there are redundant components
that can themselves be set up for bulk manufacture if the craft is
designed right, thus saving much cost of the overall craft.  (Imagine,
for example, the cost savings if the Shuttle's thermal tiles could be
swapped around with each other as needed.  Most of them are apparently
specially shaped for their particular location, though.)

> Ja I should have defined this mission more carefully.

That's another problem: trying to do extreme engineering for just one
scenario of limited appeal (no landing?  Habitat design suitable for a
very small number of people?), rather than trying to find ways to save
money for everyone.  Refusing to reuse what's out there, and insisting
that your performance needs mean you can't design stuff for any other
mission, will itself make your mission far more unaffordable - and
wasteful.  The cost savings of commodity hardware - which other people
pay for the design and much of the manufacture of - trump almost *ANY*
cost savings you can get from any degree of specialty engineering when
it comes to missions like this.  Which means that, while you might be
right that you would get cost savings on some element of your project,
that doesn't mean that it would be the overall ideal way to accomplish
even that specific mission.