The Excellence of the Shuttle System

"James Graves" wrote in message
...
Joann Evans wrote:

During reentry there should be ejection seats as a safety backup.

Unless you have re-entry worthy enclosures similar to the bailout
system of the B-70, what does ejection get you during re-entry? You just
toast seperately from the ship.

That's pretty much the problem. You're way up high, going way too fast,
for any effective bailout system.

You'd have to design a completely separate re-entry system.

In case you haven't seen it yet, Newsday had a gripping account of the
final few minutes of Columbia:

http://www.newsday.com/news/health/n...0,442476.story

[... deleted ...]

The idea's not new, we call it Shuttle-C. Some like it, some don't.
and it isn't necessairily cheap, either.

After all we do have a heavy launch
vehicle. The shuttle system without the shuttle.

There are many routes to cheaper and safer access to LEO. None of those
paths, however, start with the Shuttle program.

James Graves

Aluminium is a very cheap material but has to be inappropriate for building
the Shuttle's wings etc.
If the Shuttle had been constructed out of titanium, which has a 2000c
degree melting point instead of the 400-C of aluminium, how much lower would
it have been before breakup?
Perhaps a titanium wing structure with the interior box sections filled in
with a lightweight refractory foam to exclude the superheated gasses?
Titanium's STW ratio is favourable enough for fighter aircraft so why not?

(James Graves) wrote in message ...
That's pretty much the problem. You're way up high, going way too fast,
for any effective bailout system.

Actually, quite a few bailout systems have been proposed. A derivative
of the XB-70 ejection seat was among them.

http://www.astronautix.com/craft/egress.htm

You'd have to design a completely separate re-entry system.

And that was exactly what the bailout systems included.

A list of systems:
http://www.astronautix.com/craft/mancraft.htm

Specific re-entry capable examples that might fit into an ejection
seat-sized package:

http://www.astronautix.com/craft/encap.htm
http://www.astronautix.com/craft/geleraft.htm
http://www.astronautix.com/craft/moose.htm
http://www.astronautix.com/craft/paracone.htm
http://www.astronautix.com/craft/saver.htm

There's quite a number of capsule concepts, too, but those don't
retrofit as well into the shuttle.

Mike Miller, Materials Engineer

In article ,
Eric Fenby wrote:
Aluminium is a very cheap material but has to be inappropriate for building
the Shuttle's wings etc.

Aerospace aluminum alloys are not all that cheap, actually...

If the Shuttle had been constructed out of titanium, which has a 2000c
degree melting point instead of the 400-C of aluminium, how much lower would
it have been before breakup?

Possibly not any lower at all.

First, let's get the numbers right. Aluminum melts at 659degC, and
titanium at 1670degC. Moreover, those may not be the relevant numbers:
the highest *usable* temperature for a structural material is typically
rather lower, because most metals are quite weak by the time they're about
to melt. Aluminum alloys are generally considered structurally useful up
to 250-300degC, titanium alloys up to 500-600degC. The number we care
about is probably somewhere in between the usable temperature and the
melting point.

Now, as for a titanium Columbia...

For one thing, the outer thermal protection would have been different --
generally thinner -- since the interior could run hotter. (The big
advantage cited for titanium structure, when NASA was considering what
material to use, was that the development of the tiles etc. would be
easier.) So the hole might well have been bigger. Also, the structure
inside would have been hotter to begin with, since the whole point of
using titanium would have been to permit that.

Then too, the titanium would have been considerably thinner, since it's a
stronger (and denser) material.

Also, the combination of thinner material and titanium's *much* lower
thermal conductivity makes a titanium structure much more vulnerable to
localized overheating, since it's not nearly as good at conducting heat
away from a hot spot.

Put all this together, and it's not clear that you get much advantage,
especially given the horrendous conditions involved. This wasn't a case
of aluminum being almost good enough.

Finally, even holding together a little bit longer confers no real
advantage in such a situation. There would still be no realistic chance
of the wing holding together all the way to the ground (which is what it
takes to do a successful bailout from an orbiter -- the last man out
leaves at quite low altitude).

Perhaps a titanium wing structure with the interior box sections filled in
with a lightweight refractory foam to exclude the superheated gasses?

If you want to spend considerable weight on improving tolerance to faults
in the thermal protection, probably much the most effective way would be
to forget screwing around with the structure, and put a layer of ablator
behind the leading edge.

Although I'm not up on everything that's done in advanced materials, I'm
not aware of any "lightweight refractory foams". Certainly not ones that
were available in the early 1970s.

Titanium's STW ratio is favourable enough for fighter aircraft...

Fighter aircraft are invariably mostly aluminum. The only exceptions are
the MiG-25 and MiG-31, which are steel (heat-resistant but very heavy).
The only operational titanium aircraft have been a few specialized
high-speed types, notably the Blackbirds.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

Eric Fenby wrote:

Aluminium is a very cheap material but has to be inappropriate for building
the Shuttle's wings etc.

Given the design choices, it was fine. The shuttle was never designed
to survive a significant breach in its TPS. Wether or not that was a
good design decision is a discussion for another day.

If the Shuttle had been constructed out of titanium, which has a 2000c
degree melting point instead of the 400-C of aluminium, how much lower would
it have been before breakup?

Answer: Not much lower. From the Newsday article:

"But with the boundary layer disrupted, the temperature of the
atoms and molecules blasting into the wing probably exceeded
8,000 degrees near the leading edge breach itself."

Perhaps a titanium wing structure with the interior box sections filled in
with a lightweight refractory foam to exclude the superheated gasses?

The foam would be blown away shortly before the wing melted and broke
off. They were still at hypersonic when big chunks of the shuttle were
breaking off.

Titanium's STW ratio is favourable enough for fighter aircraft so why not?

Titanium is a fantasically great material, from an aircraft designer's
perspective.

From an aircraft _builder's_ perspective, it isn't so nice.

For an example of this, check the TV show Nova, which recently aired a
program on the JSF competition. Boeing had lots of "fun" with a
specially machined titanium bulkhead that tied together the whole
aircraft. The material is very, very difficult to work with.

And then there's the question of how much it costs...

James Graves

James Graves wrote:

[snip]

The idea's not new, we call it Shuttle-C. Some like it, some don't.
and it isn't necessairily cheap, either.

After all we do have a heavy launch
vehicle. The shuttle system without the shuttle.

There are many routes to cheaper and safer access to LEO. None of those
paths, however, start with the Shuttle program.

Those that don't like the Shuttle-C concept seem to agree with you.

--

You know what to remove, to reply....

Sander Vesik wrote:

Joann Evans wrote:

But military C-130 crews also have to consider that someone may be
out to actively shoot them down one day.

space debris does that for space vehicles - esp ones with wings.


Even with recent events, except for possibly adding some
countermeasures for shoulder-fired terrorist weapons, this isn't a
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The weapons are not in any particular way exclusive or specific to
terrorists so its dishonest to call them "shoulder-fired terrorist
weapons".

Correct. But they are starting to be increasingly used by
terroriists. Thus the prospect of countermeasures on civil aircraft.

How do you classify stringers, btw? They have used by
terrorists to down far more aircarft than the ones in use in Iraq.

It's a 'terrorist weapon' if a terrorist uses it. This is exactly why
I did not simply say 'shoulder fired weapons.'

normal concern for most cargo aircraft...or even the shuttle.

It appears to be a concern for normal passenger aircraft occasionaly.

Right, but we still don't equip them with ejection systems. Greg's
point was that the C-130 is an example of a cargo plane that has this
feature. *My* point was that it's still a military aircraft whose
designers and operators know is mre likely to be operated in situations
where it may come under fire, as opposed to ejection primairily
motivated by catastrophic failure.

--
Sander

+++ Out of cheese error +++


--

You know what to remove, to reply....

(ed kyle) wrote in message . com...
(Ken S. Tucker) wrote in message . com...
The excellence of the shuttle system.

The orbiter part of the shuttle is a great machine
and has never failed (big time). The two catastophes
are from the SRB and the HO tank, and these appear
to be because of mismanaging risk, and ignoring
problems that are bound to show up in high
performance vehicles rather than any major flaw.


The shuttle design, including the design of the
orbiter itself, has a fundamental flaw. There is
no escape option for the crew in the event of a
catastrophic failure during the first couple of
minutes of flight (the SRB phase). This design
was anything but excellent. Arrogant, foolish,
or stupid are better descriptive terms. The
shuttle designers had access to years of solid
and liquid propulsion system flight history.
They should have full well known that even the
most successful launch systems (like Minuteman)
failed 1-2% of the time - and that the failures
often occurred during the first few minutes of
flight.

- Ed Kyle


I quote from the above referenced article:


But investigators were struck by the way the crew modules of both
Challenger and Columbia broke away relatively intact. The
survivability study concluded relatively modest design changes might
enable future crews to survive long enough to bail out.


A properly designed and built crew module could separate from the
orbiter at the bulkheads (perhaps primacord or other explosive
separation system). It could subsequently decelerate by airdrag or fly
under rocket power then land using parachutes.

Zoltan

(Mike Miller) wrote in message ...
(James Graves) wrote in message ...
That's pretty much the problem. You're way up high, going way too fast,
for any effective bailout system.
Actually, quite a few bailout systems have been proposed. A derivative
of the XB-70 ejection seat was among them.
http://www.astronautix.com/craft/egress.htm
You'd have to design a completely separate re-entry system.

And that was exactly what the bailout systems included.
A list of systems:
http://www.astronautix.com/craft/mancraft.htm
Specific re-entry capable examples that might fit into an ejection
seat-sized package:
http://www.astronautix.com/craft/encap.htm
http://www.astronautix.com/craft/geleraft.htm
http://www.astronautix.com/craft/moose.htm
http://www.astronautix.com/craft/paracone.htm
http://www.astronautix.com/craft/saver.htm
There's quite a number of capsule concepts, too, but those don't
retrofit as well into the shuttle.
Mike Miller, Materials Engineer

If you look at the Columbia ascent problem, the left
wing became the hazard by yawing and rolling the
orbiter beyond safe conditions. At that point it would
be better to discard both wings (explosive bolts) and
return within the remaining capsule. I would think the
wingless orbiter would extend it's flight to well beyond
KSFC, giving the crew a bailout option over the
Atlantic, possibly including some light-weight para-
chute breaking on the orbiter.
It might be possible to bring a wingless orbiter down
into the Atlantic by modest parachute without
significant trauma to the crew, as the X-B70 and
later the proposed B1-A was initially to incorporate.
((IIRC this was scrapped on the B1-A because it
added ~5,000 lbs)).

Regards Ken S. Tucker
PS: Thank you all for responding to my OP.

(Ken S. Tucker) writes:

If you look at the Columbia ascent problem, the left
wing became the hazard by yawing and rolling the
orbiter beyond safe conditions. At that point it would
be better to discard both wings (explosive bolts) and
return within the remaining capsule. I would think the
wingless orbiter would extend it's flight to well beyond
KSFC, giving the crew a bailout option over the
Atlantic,

....Except that without wings, the bare orbiter fuselage would be unstable,
and the re-entry plasma would be eating through the unprotected scars left
by the wing roots. Cutting loose the crew cabin would result in similar
stability and thermal protection problems...


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

(Karl Hallowell) wrote:
(dave schneider) wrote:
[...]
One disadvantage to a smaller winged orbiter, btw, is one that Henry
and others have pointed out: the larger orbiter has a better
energy/surface figure because you're supporting the mass with more
area (scaling laws), and this means the smaller vehicle has tougher
TPS requirements for vulnerable areas like leading edges.

Capsules dodge the leading edge thing, so the scaling laws don't hurt
as much for them.

If I understand the original poster, he suggests scaling the entire
orbiter down rather than just the wings. In that case, the surface
area per mass should increase. And if I understand you, that means the
energy (dissipation?) per surface area should decrease.


I would hope he was scaling the whole thing down, as the orbiter is
much too heavy for any smaller wings! And because of various volume
considerations, a scaled down orbiter doesn't get light enough to
maintain the current area/mass ratio -- or else I'm way off in
remembering Henry's comments from 6-10 months ago!

/dps