NASA panel says US cannot do space any more.

In article ,
says...

On Monday, June 9, 2014 3:27:52 AM UTC+12, Jeff Findley wrote:
In article ,
Bull$hit. A smaller, fully reusable, launch vehicle will beat a large,

expendable, launch vehicle on cost.

You are setting up a straw man here.

You have ignored that I'm speaking of large fully reusable vehicles
vs. small fully reusable vehicles.

I still disagree with you. You're putting the cart before the horse.
Large fully reusable vehicles will have higher development costs,
construction costs, infrastructure costs, and maintenance costs than a
smaller vehicle. Building such a vehicle without a market is a risky
proposition indeed. There is no existing market for a large launch
vehicle of any kind to exploit. Without a market to attack, you'll find
precious few investors for such a project.

So, when you're putting up 420 tonne solar power satellites, you need
an 11,000 tonne fully reusable multi-stage rocket.

SPS (with power beamed to earth) has never been attempted. Again,
you're providing a solution to a problem which does not yet exist.
"Going big early" does not make sense in this situation.

A fully reusable sized for the existing DOD and comsat markets is a more
economically viable approach. Sure, you could consider that vehicle a
"proof of concept" for a much bigger vehicle, but you're still faced
with the problem of finding a market for the much larger vehicle.

Note that SpaceX has solved precious few technical problems in
spaceflight. They've largely been repeating what others have done.
They could have skipped Falcon 1 and attempted Falcon 9 from the
beginning. But, assuming the same number of launch failures for either
approach (new company learning the ropes), they'd have burned through
much more money by attempting the larger, more expensive, vehicle first.
Given how close SpaceX was to failing as a company (one more Falcon 1
failure was all it would have taken), they surely would have failed if
they'd have attempted Falcon 9 first.


Also, the "modular rocket" argument you make has *never* panned out in
reality. Engines optimized for a first stage are not the same as
engines optimized for vacuum. Engines that operate from sea level to
vacuum can be tricky (e.g. SSME). It's quite clear that you don't
understand these issues because you're not an aerospace engineer.

Other factors enter into the design of these stages which quite often
result in different propellants for lower stages versus upper stages.
Again, this arises due to the different requirements for the stages.
You can't dismiss those with the sort of simple minded math you keep
posting here. If that offends you, I'm sorry. But if I can see how
oversimplified your math is, with my mere bachelors of science in
aerospace engineering, then "real" engineers with PHD's in the same
would surely laugh out loud at your simple approaches to these very
complex problems.

Jeff
--
"the perennial claim that hypersonic airbreathing propulsion would
magically make space launch cheaper is nonsense -- LOX is much cheaper
than advanced airbreathing engines, and so are the tanks to put it in
and the extra thrust to carry it." - Henry Spencer