RCC repair concepts

http://www.orlandosentinel.com/news/...eadlines-space

In article t,
Craig Fink wrote:

Sounds like NASA may be over constraining the requirements. When a problem
is over constrained it can and will effect the outcome.

That is very often the case. Good observation.

It would be nice to do the repair in a single spacewalk, but it's not
necessary. Limiting repairs to a single spacewalk would get you simple
patches, but can it fix all types of damage?

This requirement is interesting. I think the idea is that in case
damage is not detected until near the end of a mission and there is
little time or spare ECLSS for EVAs, the crew ought to be able to repair
any damage in as little time as possible.How much ECLSS capacity does a
nominal mission have for contingency EVAs? For instance, on STS-107
which was not planned to require any at all, how many EVAs could have
been supported at the end of a nominal mission, had the magnitude of the
damage been determined and a repair plan implemented? I realize that
the on-orbit inspection capability being implemented for future missions
would hopefully prevent any last-minute surprises in discovering TPS
damage; however, there always exists the possibility of late-discovered
or -suspected damage that may have to be dealt with as rapidly as
possible.

--
Herb Schaltegger, B.S., J.D.
Reformed Aerospace Engineer
"Heisenberg might have been here."
~ Anonymous

Herb Schaltegger wrote in
:

In article t,
Craig Fink wrote:

It would be nice to do the repair in a single spacewalk, but it's not
necessary. Limiting repairs to a single spacewalk would get you
simple patches, but can it fix all types of damage?

This requirement is interesting. I think the idea is that in case
damage is not detected until near the end of a mission and there is
little time or spare ECLSS for EVAs, the crew ought to be able to
repair any damage in as little time as possible.

Bingo.

How much ECLSS
capacity does a nominal mission have for contingency EVAs?

Typically just one.

--
JRF

Reply-to address spam-proofed - to reply by E-mail,
check "Organization" (I am not assimilated) and
think one step ahead of IBM.

Not been on line to read the whole article... pity peeps cannot be bothered
to just post a bit of the flavour here...

Hwever, how on earth would they test these patches? Are we going to see a
mini spacecraft that they practice on and then re enter it?

Brian

--
Brian Gaff....
graphics are great, but the blind can't hear them
Email:
__________________________________________________ __________________________
__________________________________


"Jorge R. Frank" wrote in message
...
| Herb Schaltegger wrote in
| :
|
| In article t,
| Craig Fink wrote:
|
| It would be nice to do the repair in a single spacewalk, but it's not
| necessary. Limiting repairs to a single spacewalk would get you
| simple patches, but can it fix all types of damage?
|
| This requirement is interesting. I think the idea is that in case
| damage is not detected until near the end of a mission and there is
| little time or spare ECLSS for EVAs, the crew ought to be able to
| repair any damage in as little time as possible.
|
| Bingo.
|
| How much ECLSS
| capacity does a nominal mission have for contingency EVAs?
|
| Typically just one.
|
| --
| JRF
|
| Reply-to address spam-proofed - to reply by E-mail,
| check "Organization" (I am not assimilated) and
| think one step ahead of IBM.


---
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Craig Fink wrote:

I hope NASA does the smart thing and picks more than one. In the article it
sounds like there is a "leading contender" of patchs. Since no one knows
what the damage might look like or where it is located, pick several ideas.
Small patch, medium patch, large patch, missing panel, and a bunch of
generic patch type material with fasteners.

As someone whose had to wrestle with just this problem... It's going
to be very difficult to create a kit, or series of kits, that can
cover every possible permutation of damage. At some point you have to
accept that there is damage you will be unable to repair.

After the initial cost of taking them to orbit, it costs nothing to store
them there.

Utterly wrong regardless of the meaning you attach to the word 'cost',
assuming you use a reasonable meaning. On top of volume, moment, and
weight, there is training, maintenance (preventative and corrective),
certification, inventory (space and ground), documentation...

article quote

Any RCC repair must meet several requirements. First, it must survive
re-entry. Materials must adhere in the vacuum of space and cure in orbit
within 24 hours. The fix must be able to be done in a single spacewalk with
little preparation of the surface to be repaired.

end article quote

Sounds like NASA may be over constraining the requirements. When a problem
is over constrained it can and will effect the outcome.

It would be nice to do the repair in a single spacewalk, but it's not
necessary. Limiting repairs to a single spacewalk would get you simple
patches, but can it fix all types of damage?

That limitation is probably driven by the need to conserve
consumables. Using multiple walks may require earlier replenishment
of Quest (if station resources are used), thus increasing total
program risk. Or if Shuttle resources are used it endangers the
capability to make an emergency spacewalk to close the payload bay
doors, stow the arm, etc.

It would be nice to have the material cure within 24 hours, but it's not
necessary. There may be other materials that are much better that might
cure with heat. On entry, the heat arrives first, before any significant
forces.

The problem is, the difference in time between the arrival of heat and
the arrival of significant forces is relatively small. You risk not
having the entire patch cured before stress is put on it. (Not to
mention the problem of the different rise rates for heating on
different parts of the airframe.)

How about an aerobraking pass through the atmosphere? Lower perigee, cure
the patch, raise perigee, check the patch, make additional repairs if
necessary, then deorbit. Even if the patch material cures in a vacuum, it
still might be a good idea to test it a little before entry.

One of the more knowledgeable folks might comment here, but I don't
think there is going to be enough fuel to perform any variant of this
procedure, especially one that raises the 'check the patch' orbit high
enough to have significant effects. (Especially considering that you
have to risk opening the doors to check the patch.)

D.
--
The STS-107 Columbia Loss FAQ can be found
at the following URLs:

Text-Only Version:
http://www.io.com/~o_m/columbia_loss_faq.html

Enhanced HTML Version:
http://www.io.com/~o_m/columbia_loss_faq_x.html

Corrections, comments, and additions should be
e-mailed to , as well as posted to
sci.space.history and sci.space.shuttle for
discussion.

(Derek Lyons) wrote in
:

Craig Fink wrote:

I hope NASA does the smart thing and picks more than one. In the
article it sounds like there is a "leading contender" of patchs. Since
no one knows what the damage might look like or where it is located,
pick several ideas. Small patch, medium patch, large patch, missing
panel, and a bunch of generic patch type material with fasteners.

As someone whose had to wrestle with just this problem... It's going
to be very difficult to create a kit, or series of kits, that can
cover every possible permutation of damage. At some point you have to
accept that there is damage you will be unable to repair.

Exactly. The CAIB recommendation called for repair capability for the
"widest practicable" range of damage, and the flight techniques panel that
is working this issue has made it clear that *they* will define what the
term "widest practicable" means (and it may mean something different for
return-to-flight than for long-term ops). Admiral Gehman is in concurrence
with this approach; he noted in one press conference that, while the foam
on STS-107 produced a 6-10 inch hole, if NASA mitigates all the sources of
"big" foam (bipod ramp, intertank flange, etc), then NASA only has to worry
about little pieces of foam causing little holes.

How about an aerobraking pass through the atmosphere? Lower perigee,
cure the patch, raise perigee, check the patch, make additional
repairs if necessary, then deorbit. Even if the patch material cures
in a vacuum, it still might be a good idea to test it a little before
entry.

One of the more knowledgeable folks might comment here, but I don't
think there is going to be enough fuel to perform any variant of this
procedure, especially one that raises the 'check the patch' orbit high
enough to have significant effects. (Especially considering that you
have to risk opening the doors to check the patch.)

You are correct. Lowering perigee low enough to *meaningfully* test the
patch will subject the orbiter to enough drag that *apogee* will also be
lowered quite a bit. The ability of the orbiter to recover from such a
maneuver, even assuming propellant were available (which it isn't), is
dubious.


--
JRF

Reply-to address spam-proofed - to reply by E-mail,
check "Organization" (I am not assimilated) and
think one step ahead of IBM.

This requirement is interesting. I think the idea is that in case
damage is not detected until near the end of a mission and there is
little time or spare ECLSS for EVAs, the crew ought to be able to repair
any damage in as little time as possible.

I would have thought this is also driven by a "flea and lice" scenario,
i.e., a mission cut short for some reason (such as like that Spacelab
refly) _and_ RCC/TPS damage occuring.

Jan

Jorge R. Frank wrote:

(Derek Lyons) wrote in
:

Craig Fink wrote:

I hope NASA does the smart thing and picks more than one. In the
article it sounds like there is a "leading contender" of patchs. Since
no one knows what the damage might look like or where it is located,
pick several ideas. Small patch, medium patch, large patch, missing
panel, and a bunch of generic patch type material with fasteners.


Exactly. The CAIB recommendation called for repair capability for the
"widest practicable" range of damage, and the flight techniques panel that
is working this issue has made it clear that *they* will define what the
term "widest practicable" means (and it may mean something different for
return-to-flight than for long-term ops). Admiral Gehman is in concurrence
with this approach; he noted in one press conference that, while the foam
on STS-107 produced a 6-10 inch hole, if NASA mitigates all the sources of
"big" foam (bipod ramp, intertank flange, etc), then NASA only has to
worry about little pieces of foam causing little holes.

That doesn't sound good to me. Kind of a minimalist approach. Off trying to
figure out what the smallest possible hole in the heat shield is, and
design a patch for it? Starting with hole where the approximate size is
know and working hard as they can in the wrong direction. "Widest
practicable" means smaller than?

Shouldn't NASA really be thinking about erroring on the side of safety, at
least until the next launch? Think grandious, not small, in terms safety.

Maybe the PAO needs a representative at the flight techniques panel? Can
you imagine what would happen if the next flight had a one square foot hole
in it like Columbia, for a different reason of course, and the astronaut
holds up a 6 inch patch to it? On national TV no less?


How about an aerobraking pass through the atmosphere? Lower perigee,
cure the patch, raise perigee, check the patch, make additional
repairs if necessary, then deorbit. Even if the patch material cures
in a vacuum, it still might be a good idea to test it a little before
entry.

Lowering perigee low enough to *meaningfully* test the
patch will subject the orbiter to enough drag that *apogee* will also be
lowered quite a bit.

Yeah, that's the idea. That's where the energy comes to heat up the patch.
After one pass that lowers apogee to the minimum 2 day orbit, not much fuel
is required to increase perigee. The only additional fuel is two times that
required to raise perigee a bit.

Take a look at the CAIB preliminary report, in particular the heat rate/
dynamic pressure plot. 5 BTU/sec can be obtained with essentially no
dynamic pressure. Look at the slope of the curves here. Heat rate has a
slope much much () greater than dynamic pressure.

I wonder what dynamic pressure is required to lower apogee to the minimum
safe 2 day orbit?

If you want the name of someone who works at JSC who can come up with the
guidance changes, give me a call.

The ability of the orbiter to recover from such a
maneuver,

I don't understand this statement? What is unrecoverable?

even assuming propellant were available (which it isn't), is
dubious.

It would be interesting to see what the record shows for usable OMS/RCS
fuel on the runway? What do you think it is?

Overall, it's probably not very useful idea, other than the knowledge that
it might be useful in the future for some unknown reason.

Craig Fink

Jorge R. Frank wrote:

Craig Fink wrote:

I hope NASA does the smart thing and picks more than one. In the
article it sounds like there is a "leading contender" of patchs. Since
no one knows what the damage might look like or where it is located,
pick several ideas. Small patch, medium patch, large patch, missing
panel, and a bunch of generic patch type material with fasteners.


Exactly. The CAIB recommendation called for repair capability for the
"widest practicable" range of damage, and the flight techniques panel that
is working this issue has made it clear that *they* will define what the
term "widest practicable" means (and it may mean something different for
return-to-flight than for long-term ops). Admiral Gehman is in concurrence
with this approach; he noted in one press conference that, while the foam
on STS-107 produced a 6-10 inch hole, if NASA mitigates all the sources of
"big" foam (bipod ramp, intertank flange, etc), then NASA only has to
worry about little pieces of foam causing little holes.

That doesn't sound good to me. Kind of a minimalist approach. Off trying to
figure out what the smallest possible hole in the heat shield is, and
design a patch for it? Starting with hole where the approximate size is
know and working hard as they can in the wrong direction. "Widest
practicable" means smaller than?

Shouldn't NASA really be thinking about erroring on the side of safety, at
least until the next launch? Think grandious, not small, in terms safety.

Maybe the PAO needs a representative at the flight techniques panel? Can
you imagine what would happen if the next flight had a one square foot hole
in it like Columbia, for a different reason of course, and the astronaut
holds up a 6 inch patch to it? On national TV no less?


How about an aerobraking pass through the atmosphere? Lower perigee,
cure the patch, raise perigee, check the patch, make additional
repairs if necessary, then deorbit. Even if the patch material cures
in a vacuum, it still might be a good idea to test it a little before
entry.

Lowering perigee low enough to *meaningfully* test the
patch will subject the orbiter to enough drag that *apogee* will also be
lowered quite a bit.

Yeah, that's the idea. That's where the energy comes to heat up the patch.
After one pass that lowers apogee to the minimum 2 day orbit, not much fuel
is required to increase perigee. The only additional fuel is two times that
required to raise perigee a bit.

Take a look at the CAIB preliminary report, in particular the heat rate/
dynamic pressure plot. 5 BTU/sec can be obtained with essentially no
dynamic pressure. Look at the slope of the curves here. Heat rate has a
slope much much () greater than dynamic pressure.

I wonder what dynamic pressure is required to lower apogee to the minimum
safe 2 day orbit?

If you want the name of someone who works at JSC who can come up with the
guidance changes, give me a call.

The ability of the orbiter to recover from such a
maneuver,

I don't understand this statement? What is unrecoverable?

even assuming propellant were available (which it isn't), is
dubious.

It would be interesting to see what the record shows for usable OMS/RCS
fuel on the runway? What do you think it is?

Overall, it's probably not very useful idea, other than the knowledge that
it might be useful in the future for some unknown reason.

Craig Fink

Jorge R. Frank wrote:

"Brian Gaff" wrote in
:

Not been on line to read the whole article... pity peeps cannot be
bothered to just post a bit of the flavour here...

Hwever, how on earth would they test these patches? Are we going to
see a mini spacecraft that they practice on and then re enter it?

No. They plan to put a practice panel in the shuttle payload bay (on STS-
114, it will be mounted on the LMC, next to the replacement CMG). The EVA
crew will practice the repairs, then the panel will be returned to the
ground and tested there (most likely arcjet testing).


They could alway put a sample on the trailing edge of the body flap. It was
brought out at one of the CAIB that NASA ran a DTO on ?STS-2? with some
materials there. That way when they get down with their sample in the
payload bay, they also have one that flew through the entry environment.
They could even have the sample poking out into the plasma flow a little
bit to more closely match the environment at the leading edge. Put several
samples out.

This would give NASA a control sample to compare to the arcjet testing
sample.

Craig Fink