Shuttle fleet grounded again?

"Martin Brown" wrote in message
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Roger Hamlett wrote:

"Martin" wrote in message
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"has.mac" wrote in message
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"Martin" wrote in message
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Sky News are reporting that NASA have decided to ground the Shuttle
fleet
again once the current mission is complete. Looks like they are worried
over
the external tank foam yet again.

And with good reason. Big chunks of something were spotted on the initial
launch video - the live feed I was watching replaed it within about 10
minute of the launch. Nature seemed not to have noticed.

Does make you wonder why the insulation wasn't put on the inside of the
structure in the first place.

Too difficult to install it internally in a pressure vessel.

Didn't they used to paint the external tank. Would this help keep the
foam
in place, at the cost of weight?

The external foam system is a lot more complicated than you imagine. The
leading edges of the tank (and the bits near the engines) are subject to
serious aerodynamic and thermal stresses. Several foams are used.

All I know is that an aeroplane has its cabin insulation on the inside of
the skin and my loft insulation is inside not stuck on the roof.

However if you think on, your hot water tank (which like the external
tank, has to hold materials inside), is insulated on the outside, as is
the cold water supply cystern. In fact your 'loft insulation', is 'on'
the ceilings, and has the complete extra layer of the 'roof' outside it.

It has to cope with thermal expansion/contraction over a huge range of
temperatures and in an environment often at 100% humidity and weaknesses
in the closed cell foam structure allow ice patches to form.

Its a design flaw and I'm betting that without a fundemental re-design
they may have to live with it. I don't think paint would help as its
breaking away from the outer surface of the tank. Could they perhaps fit
something (like a giant condom) over the top end of the tank (where bits
coming off are more likely to hit the Orbiter) to help hold the foam in
place?

The problem is the huge range of temperatures and pressures the 'condom'
would have to survive. The odds are that unless it is made of something
like aluminium, you would end up with bits of this falling off as well...

The best solution for reentry is the old traditional ablative heat shield.
Very robust, low tech and entirely protected from damage during launch.

I think we may well have seen the last shuttle flight.

Me too. And that is a pity since there is nothing even on the drawing
board to replace it. The ISS I would happily dump into the ocean tomorrow
so that space *science* and astronomy got more funding.

What puzzles me, is that they didn't expect this (maybe they did...). If
you watch the old Apollo launches, you have so much ice falling, ignoring
any 'insulation' materials, that damage has to be expected. Every shuttle
launch has had tile damage during take-off, what was exceptional in the
Columbia launch, was not that it occurred, but the size of the piece
involved, and that it managed to damage the leading edge structure (which
is much tougher than the 'tiles'). Something like an alloy 'net condom',
should have been possible, if necessary at the cost of one crew place, to
keep the maximum size of pieces involved down to reasonable limits...

They did. There is some circumstantial evidence that the change to non-CFC
blown foams for the bulk tank insulation may have made it slightly more
brittle. OTOH some of the bits known to have fallen off in the past were
manually applied still using CFC-11 blowing agent.

NASA short report online at:
http://spaceflight.nasa.gov/shuttle/...fact_sheet.doc

Intrinsically there is a very nasty problem that huge changes in
temperature typically from 300K down to 20K for the LH2 tank has bad
effects on plastic to metal bonding. If foam cell integrity gets
compromised then cool spots develop and water ice ingress becomes an
issue.

Regards,
Martin Brown

Hi Martin


I think you will find they did expect bits to hit the Shuttle, they even
developed simulation software to predict it. The problem was they didn't
think that it could do the sort of damage to the structure that it did. If
you saw any of the testing of the leading edge panels, they were rather
shocked by the damage created.

The real problem is the whole shuttle was built as cheaply as possible and
at a time when the technology was primative and the shuttle has chugged on
and on for years with these faults. NASA has had a lot of luck over that
time, but a 40% loss rate on the fleet would not be something an airline
would be proud of!!

Best to close it down and put the three remaining orbiters in museums before
they kill anyone else. The ISS is a white elephant anyway. Nice idea but
that money could be better spent on more interesting projects. Who wouldn't
like to see a rover sent to Europa for example?

Just out of interest anyone know if the Russians had the same problem with
their copy of the shuttle? I think it flew once?

Martin

"Martin Brown" wrote in message
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Roger Hamlett wrote:

"Martin" wrote in message
...

"has.mac" wrote in message
...

"Martin" wrote in message
...

Sky News are reporting that NASA have decided to ground the Shuttle
fleet
again once the current mission is complete. Looks like they are worried
over
the external tank foam yet again.

And with good reason. Big chunks of something were spotted on the initial
launch video - the live feed I was watching replaed it within about 10
minute of the launch. Nature seemed not to have noticed.

Does make you wonder why the insulation wasn't put on the inside of the
structure in the first place.

Too difficult to install it internally in a pressure vessel.


Do you work with pressure vessels? If you do you will be well aware of
modern composite insulation that is used in the production of pressurised
liquid Oxygen/Nitrogen storage vessels.

Martin

What's this replacement for the shuttle they are talking about?

In article , Martin Brown
wrote:

Fleetie wrote:

Anyway, I'm thinking of something like a wire mesh or plastic netting
shield wrapping
the entire external fuel tank, outside the foam, pulled tight over the
whole lot.
Then if any large bits of foam did come unstuck, they'd be held in and
prevented from
falling off. Even a good strong plastic netting wrap should do it, I'd have
thought.
---

Thoughts on that?

The stresses on the foam are pretty extreme at maximum. The ablator
material on the tank leading edge and near the rocket exhausts have to
withstand 1200F (sic) or ~650C and with a forced air flow that will
defeat any normal plastic mesh and most common metal ones.

Regards,
Martin Brown

Steven wrote:

What's this replacement for the shuttle they are talking about?

Vapourware.

Regards,
Martin Brown

"Martin Brown" wrote in message
...
Steven wrote:

What's this replacement for the shuttle they are talking about?

Vapourware.

Regards,
Martin Brown

And whatever happened to the Space Station rescue vehicle that was being
designed by NASA that was meant to be ready by now as well? That could
evacuate a full crew from the ISS.

As much as I'm a fan of manned space flight, NASA just doesn't have the
money to do it properly and with the next US President probably won't be
interested in Space.

Martin

"Martin" wrote in message
...

"Martin Brown" wrote in message
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Steven wrote:

What's this replacement for the shuttle they are talking about?

Vapourware.

Regards,
Martin Brown

And whatever happened to the Space Station rescue vehicle that was being
designed by NASA that was meant to be ready by now as well? That could
evacuate a full crew from the ISS.

As much as I'm a fan of manned space flight, NASA just doesn't have the
money to do it properly and with the next US President probably won't be
interested in Space.

Martin


The fact is the Shuttle is way past its sell by date, and was a botched mess
from the start. The worry is that although some life remains there is little
by way of replacement on the drawing board.

Pity the ESA Columbus Space Shuttle was never built.

"Mark J Underwood" wrote in
message ...

"Martin" wrote in message
...

"Martin Brown" wrote in message
...
Steven wrote:

What's this replacement for the shuttle they are talking about?

Vapourware.

Regards,
Martin Brown

And whatever happened to the Space Station rescue vehicle that was being
designed by NASA that was meant to be ready by now as well? That could
evacuate a full crew from the ISS.

As much as I'm a fan of manned space flight, NASA just doesn't have the
money to do it properly and with the next US President probably won't be
interested in Space.

Martin


The fact is the Shuttle is way past its sell by date, and was a botched
mess from the start. The worry is that although some life remains there is
little by way of replacement on the drawing board.

Pity the ESA Columbus Space Shuttle was never built.
Sorry I mean Hermes

"Mark J Underwood" wrote in
message ...

"Mark J Underwood" wrote in
message ...

"Martin" wrote in message
...

"Martin Brown" wrote in message
...
Steven wrote:

What's this replacement for the shuttle they are talking about?

Vapourware.

Regards,
Martin Brown

And whatever happened to the Space Station rescue vehicle that was being
designed by NASA that was meant to be ready by now as well? That could
evacuate a full crew from the ISS.

As much as I'm a fan of manned space flight, NASA just doesn't have the
money to do it properly and with the next US President probably won't be
interested in Space.

Martin


The fact is the Shuttle is way past its sell by date, and was a botched
mess from the start. The worry is that although some life remains there
is little by way of replacement on the drawing board.

Pity the ESA Columbus Space Shuttle was never built.
Sorry I mean Hermes


Given the massive cost of developing these things, perhaps it is time for
NASA, ESA, the Japanese and even (gulp) the French to get together to build
a truly international replacement?

Bob H

"Bob Hill" wrote in message
...



Given the massive cost of developing these things, perhaps it
is time for NASA, ESA, the Japanese and even (gulp) the French
to get together to build a truly international replacement?


Since France is one of the major contributors
to ESA launchers, there is no need to mention
them explicitly. Though perhaps the UK should
be, IIRC the UK is not a (significant) contributor
to ESAs launcher programs.

RonL

--
"Something unknown is doing we know not what."

"Bob Hill" wrote in message
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"Mark J Underwood" wrote in
message ...

"Mark J Underwood" wrote
in message ...

"Martin" wrote in message
...

"Martin Brown" wrote in message
...
Steven wrote:

What's this replacement for the shuttle they are talking about?

Vapourware.

Regards,
Martin Brown

And whatever happened to the Space Station rescue vehicle that was
being designed by NASA that was meant to be ready by now as well? That
could evacuate a full crew from the ISS.

As much as I'm a fan of manned space flight, NASA just doesn't have the
money to do it properly and with the next US President probably won't
be interested in Space.

Martin


The fact is the Shuttle is way past its sell by date, and was a botched
mess from the start. The worry is that although some life remains there
is little by way of replacement on the drawing board.

Pity the ESA Columbus Space Shuttle was never built.
Sorry I mean Hermes


Given the massive cost of developing these things, perhaps it is time for
NASA, ESA, the Japanese and even (gulp) the French to get together to
build a truly international replacement?

Bob H


Well if you look at other joint Aerospace projects the costs tend to rocket
(no pun) as everyone wants their own things included. The Eurofighter being
a classic example.

Is there really a need for a reusable vehicle? The old Soyuz manges to do
the job and probably cost peanuts to make by now.

Martin