Shuttle fleet grounded again?

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.

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

Martin

"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.

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

Martin

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

has.mac

"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.

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

Martin

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

has.mac



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.

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?

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

Martin

"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.

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

Martin

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

has.mac



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.

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...

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

Martin
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...

Best Wishes

"Roger Hamlett" wrote in message
news

"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.

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

Martin

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

has.mac



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.

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...

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

Martin
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...

Best Wishes


I don't think it was really thought about at the design stage to any great
extend. They do allow for tile damage and in the very early mission tiles
did fall off. But I think the foam on the external tank has always been
there, they've just been very lucky, un to a point.

They could do another 100 launches before a lump of foam hits the leading
edge of the wing again, or it could happen on the next flight. If they
really want to keep the shuttle flying, I think they need to solve the
problem, which is the foam breaking off of the tank, either by placing it
inside the skin of the tank (probably requiring a redsign and therefore not
a practical option I agree) or to put some sort of cover over the top part
of the tank to hold the foam in place. Like I said something like a giant
Jonny might work.

I just don't understand NASA. You have to solve the problem, not simply
ignore it.

Martin

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.

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

Martin Brown wrote:

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

They could put that on a winged orbiter (assuming that's still a
requirement at all) if the orbiter had to carry crew only rather than
cargo. It's the sheer weight of the Shuttle that causes the extremely
high thermal loading.

Cargo should go up by rocket.

FoFP

"Martin Brown" wrote in message
...
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.

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
...
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

Roger Hamlett wrote:

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

That's what I'm wondering. Dammit: I haven't seen a live launch.

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.

The crew cabin sat on top of the Saturn V, with an escape tower. Thus
any damage from falling ice could hit only the booster systems and not
the reentry capsule.

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...

I'm starting to think "systemic fault", and since they've already moved
up the retirement of STS once...

FoFP