Russian plans - A New space race?

"Derek Lyons" wrote in message
...
Brian Thorn wrote:

On Wed, 02 Jul 2008 05:36:33 GMT, (Derek Lyons)
wrote:


That doesn't rule out a DIRECT type system, though, and DIRECT is
looking more and more attractive with every redesign and upsizing of
the Ares family.

And what will look more attractive with every redesign and upsizing of
DIRECT?

Three launches, propellant depots, or L2 rendezvous, probably. Options
also available to Ares, but Ares V will cost enormously more to field
and Ares I is right at the razor's edge of being able to do its
mission at all. Not so Direct.

On paper at least. But then Ares worked on paper too.

Ares V is already maxed out (they can't make it any taller/wider or
add more engines to the first stage) and hugely expensive, ten years
before it is supposed to fly, and Ares I is no improvement at all over
EELV despite roughly the same cost. Time to try a different
architecture.

One can chase ever more optimal architectures for years on end...
It's a wonderful way to keep engineers and bureaucrats employed and
the internet (or at least the space fan corner of it) a buzzin'.

It sucks however for actually getting anything accomplished.

The problem with Ares I and Ares V is that they're both at the limits of
what they can do without ever more radical changes to the design. Ares I
has a distinct possibility of not being big enough to do the job of lifting
a fully fueled lunar Orion with all of its safety systems intact. Ares V is
nearing things like height limits for the VAB. So we're getting a launch
vehicle that's too small to support Orion upgrades in the future and another
launch vehicle which is too big to be upgraded itself. The "shuttle
derived" SRB's are the real culprit here. They can only be stretched so
far.

Some of the solutions to the Ares I vibration problem are pretty scary. The
active control system using reverse firing thrusters to dampen the
vibrations is something that needs to be *at least* two fault tolerant so
you would still have a chance of firing the Orion launch escape system if
you had a failure. You'd want it to be three fault tolerant if you want it
to be able to continue the mission with a failure. The more fault tolerant
you make it the more complex it becomes which increases the chances that
something will fail.

Solutions like this are called a HACK in my line of work. They're put there
because someone else won't allow you to put the RIGHT fix. Hacks are ugly
and almost always cause you continuous pain in the future because once they
go in, they're always considered too expensive, time consuming, or risky to
fix.

Jeff
--
A clever person solves a problem.
A wise person avoids it. -- Einstein