In article ,
"John Mullen" writes:
"Peter Stickney" wrote in message
...

Sorry for taking so long, but I was lining up some ducks...

(snip)

I can't think of any advantages to the STS's layout. What did you mean
here?

Just off the top of my head - better alignment of the Main Engine's
thrust lines with the CG of the entire stack. This gives you less
problems with control, and more tolerance of off-normal
conditions. (Such as losing a Main Engine - it's happened once on STS)

The Buran didn't have Main Engines on the Shuttle. One of its major
advantages to me, not having all that plumbing to the ET...

You asked what advantages there were for the STS layout over the
Bura/Energia. To be more explicit, the STS's placement of the main
engines in the Orbiter give a superior thrust line through the CG of
teh stack as a whole, leading to teh advantages in control and
tolerance of failure. The Energia setup, with the Main Engines on
what is essentially the external tank section of teh stack, has the
advantage in terms of operational flexibility - you can use an Energia
stack to launch something other than Buran, for a cargo-only flight.
The problem is that Energia's cargo is still parallel staged,
(side-by-side), and the problems of guidance & control of the stack,
and tolerance of failures remain. While teh plumbing of teh external
tank to the Shuttle is a bit complicated, it hasn't been much of a
factor wrt flying the Shuttle. It could probably benefit from some of
the Russian's rather better crygenic plumbing connectors, though.


Concentration of the Guidance & Control systems in a single,
integrated system, rather than having two independant systems that
have to try to talk to each other. Keeping the expensive, reusable
bits in one place, and throwing away the cheap stuff. (As it turns
out, this didn't work out as well as originally expected - rather than
a clear advantage wrt reusing STS SSMEs vs. the Energia's cheaper,
(but still not cheap) expendables, it seems to be pretty much of a
wash.

Exactly. Although the original concept of the STS being a reuseable vehicle
was excellent, the compromises made during the design process (many at the
behest of the DoD) negated them almost entirely.

The biggest problems with Shuttle reusibilit costs weren't physical,
but people/management/the economy in general - Labor costs in the
1970s skyrocketed, and that put the overhead costs of teh refit &
refurbish cycle through the roof.


They're not really relevant - every vehicle, from a Skateboard to a
Shuttle, has failure modes which are not survivable. If the aborts
had taken place at a slightly different time, or the reentry and
landing incidents, like the time a Soyuz Service Module didn't detach
after retrofire, causing the Soyusz to reenter not heatshield first,
but Aluminum hatch cover first (The SM burned away, allowing the
spacecraft to reorient itself before the crew was lost), and the
guidance problems that have caused some reentries to occur hundreds
of miles off from their targets could very easily have been much worse.

Aviation, and especially Spaceflight, is all about tradeoffs. What
sorts of system could have been aboard Challenger that would have
extended the survival envelope significantly, and wouldn't have been a
hazard during most of the flight?

Simple. A parachute for each crew member and a bail out pole, as they fitted
post-Challenger, might have at least given them a sporting chance.

I rather doubt it. bailing out from a Shuttle, or any large airplane,
such as a KC-135, requires the the aircraft be in steady, stable
flight - not a piece of wreckage tumbling through the sky at more than
Mach 3. Then you've got the problems that come from jumping above
50,000' (Note that the Challenger's cabin section's trajectory peaked
somewhere around 100,000' - anybody jumping would follow the same
tarajectory fairly closely - there isn't much drag up there.) Any
escape mechanism used in the region where teh Challenger's loss
occurred has to provide Pressure, Oxygen, protection from the cold -
Jumping at 50,000' and free-falling means that you'll most likely
freexe to death in short order - and protection from the prepellant
residues of the boost motors, which are extremely corrosive. Ejection
seats don't add much in the way of a _usable_ escape envelope, and add
in all the dangers that accompany hot seats in airplanes - the risks
of catastrophe due to inadvertantly activating a seat - not just the
big things like, say, blowing a section of the cabin roof off with
Primacord in orbit, but if setting off pyros & such in the cabin
atmosphere, would increase teh overall danger. Capsules would, at a
great penalty in wieht and structure, extend the envelope a bit
further, but no much - the big problem with ejecting much
higher/faster than Challenger was going when the breakup occurred is
that the deceleration incurred on an unmodified ballistic trajectory
are on teh order of 50-60Gs, and aren't survivable. Adding the
ability to change the trajectory would make any such system too heavy
and complicated to be worth it.

As for Burt Rutan, please don't make the mistake that SpaceShipOne is
the harbinger of entry into orbit. It's not. The design is very
heavily optimized for a single, very limited goal - getting an X-prize
equivalent mass to 100 km altitude. The peak Mach Numbers for SS1 are
down around Mach 2, the materials are all conventional, and the
"shuttlecock" re-entry profile isn't going to hack Mach 25. Don't get
me wrong, it's an excellent achievment, but useful Space Travel it
isn't.

I still think it is a very good step in the right direction. Waiting with
bated breath...

We've been through this before - technologically, SS1 is less of a
challenge than the X-15, 45 years ago. While SS1's performance will
be sufficient to win the X-Prize, it won't yield a useful, productive
system. I'm not seeking to minimize the achievement, but let's not
blow it up beyond what it really is.

In Buran and Energiya

No. I still think though that is was a shame it wasn't persevered with.

They were keeping it around, stored against the possibility that there
may be some interest in the future. But the Assemply Building
collapsed on it. If they couldn't keep a fairly new building
together, I rather doubt that they were going to be re-starting any
serious, and expensive development programs anytime soon.

--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster