STS-114 Mission Coverage and Discussion

srmeaney · 2005-08-02 17:30:48

Hey NASA... why exactly does the spacewalk have to be done with the arm on the ISS? I thought the Shuttle's extended arm was supposed to reach.

Maybe only when it aint docked.

Rxke · 2005-08-03 04:30:20

Gotta love the way how they call that hastily ducktaped blade a "modified hacksaw"

Though it has a little Apollo 13 "jury-rig or die" quality to it, hasn't it?

The extended arm was for camera inspection, IIRC. Scenario is when Shuttle needs repair, it docks with ISS and uses CanadarmII.

Palomar · 2005-08-03 05:54:09

The extended arm was for camera inspection, IIRC. Scenario is when Shuttle needs repair, it docks with ISS and uses CanadarmII.

*Looks like there's more "you scratch my back, I'll scratch yours" going on, and this time credit is due to America:

Shuttle Spacewalk Restores Space Station's Steering Mechanism
International Space Station (SPX) Aug 02, 2005
Two U.S. space shuttle astronauts went on another spacewalk to restore the steering gear on the International Space Station.

That's from spaceflightnow.com.

--Cindy

GCNRevenger · 2005-08-03 07:22:10

Repair seems to have been sucessful... I hope they go over the heat shield with the camera/laser arm one more time though.

heh, the hacksaw was held together with duct tape

Josh Cryer · 2005-08-03 10:01:05

Heh, that stuff can fix anything.

RobertDyck, I know you read this thread regularly, just wanted to let you know, if you haven't been reading the forum announcement thread, that we have LaTeX support now (the TeX button in the reply box). I think you were one of the users who asked for that ability some time ago.

SpaceNut · 2005-08-03 10:27:29

As noted the change to a non freon based foam occurred some time after 1997, what I am wondering is if the foam ages due to environment exposure or UV or ocean moisture? Making the manual blown on stuff more suseptible to this problem.

Also have used any tanks from the change over before these last few?

GCNRevenger · 2005-08-03 11:10:23

The blowing agent is just there to make bubbles in the foam. The "new" types generally have a much higher vapor pressure than freon, so the bubbles are less consistant and perhaps larger. Inconsistant spaces imparticularly introduce weaknesses in the foam, which is quite rigid, and breaks when under the vibration stress of liftoff.

RobertDyck · 2005-08-03 11:53:55

Way cool! Thanks.

[tex:c82c932245]\frac {\Pi}{4} = 1 - \frac {1}{3} + \frac {1}{5} - \frac {1}{7} + \frac {1}{9} - \cdots[/tex:c82c932245]

[tex:c82c932245]\picture(20){ (5,10){\bullet} (0,0){\bullet} (10,0){\bullet} %therefore% }[/tex:c82c932245][tex:c82c932245]\Pi = 4 \Large\sum\footnotesize_{k=1}^{\infty}\normalsize \frac {(-1)^{k+1}}{2k - 1}[/tex:c82c932245]

Palomar · 2005-08-03 12:26:32

Way cool! Thanks.
[tex:ea4726645c]\frac {\Pi}{4} = 1 - \frac {1}{3} + \frac {1}{5} - \frac {1}{7} + \frac {1}{9} - \cdots[/tex:ea4726645c]
[tex:ea4726645c]\picture(20){ (5,10){\bullet} (0,0){\bullet} (10,0){\bullet} %therefore% }[/tex:ea4726645c][tex:ea4726645c]\Pi = 4 \Large\sum\footnotesize_{k=1}^{\infty}\normalsize \frac {(-1)^{k+1}}{2k - 1}[/tex:ea4726645c]

*EEEEEEeeeeeekkkk!!! :shock: Numbers! And those weirdo symbols! Run for the hills! Arrrghh...all the TORMENT of school daze (I mean days) in *math class* is coming back! Help...

Honestly, I benignly envy the people who can easily toss stuff like this around.

Back on topic...

--Cindy

RobertDyck · 2005-08-03 12:51:30

They non-destructively tested the specific area of foam where the large strip came off. There weren't any voids or gaps between foam and skin. That's according to a televised interview with Eileen Collins while on-orbit. http://www.napa.ufl.edu/2005news/shuttlefoam.htm]This web page says the foam was examined with X-ray backscatter as well as tetrahertz imaging.

I still think the problem is low pressure air causing foam bubbles to burst, which forms voids in the foam as well as between foam and skin. That means voids didn't exist at lift-off but did form at altitude, once voids formed the foam failed at that spot.

Another solution is an adhesive binder. We already talked about wrapping the foam in some sort of containment skin; I prefer film to mesh because film produces an aerodynamically smooth surface, less drag and no foam loss at all. However, another solution is an adhesive that binds foam to the tank more strongly than the foam holds itself together. That means if foam fails it will fall off in small pieces rather than peal off. Theoretically chunk diameter should be equal to foam thickness. The foam is 1 inch thick over the "acreage", but gets 2 inches thick in close-out areas and PAL ramps are 7 inches thick.

When I participated in a medieval recreation society we used closed-cell foam inside steel helmets. After years of use the foam would become crushed and have to be replaced. Double-face carpet tape held the foam more strongly than the foam held itself together so it crumbled when trying to remove the it. We had to use a paint scraper to remove the foam and scrape off tape, the metal surface (or paint surface) had to be clean before applying new tape or the tape wouldn't stick. Fresh tape could be pealed off, but the adhesive of old tape set. Experience showed chunks the full thickness of the foam were only as wide as foam was thick, but some pieces did come off that were 1/2 thickness and diameter up to 4 times thickness with a rough tear surface, chunk thickness varied between 1/4 and 3/4 foam thickness. For 1/4" foam that meant 1" diameter chunks roughly 1/8" thick. If that holds for ET close-out foam that would mean the largest chunks would be 1" thick and 8" diameter, most chunks from 2" foam would be 2" diameter.

RobertDyck · 2005-08-03 13:11:43

*EEEEEEeeeeeekkkk!!! :shock: Numbers! And those weirdo symbols! Run for the hills! Arrrghh...all the TORMENT of school daze (I mean days) in *math class* is coming back! Help...
Honestly, I benignly envy the people who can easily toss stuff like this around.
Back on topic...
--Cindy

(Chuckle) It took me almost an hour to figure out how to format that. The 3 dots mean "therefore"; standard TeX doesn't have a command for it so I had to use picture drawing commands. The big [tex:560a175792]\sum[/tex:560a175792] is a sum symbol, usually written with the limits above and below rather than subscript and superscript, but obviously this version of TeX doesn't make exceptions for sum, limit, and calculus symbols. I had to specify font size rather than automatically adjusting to the thing it applies to.

Ok English-type people, I just used a dangling participle. I should have said "thing to which it applies" rather than "thing it applies to". Tough, I'm a math-type guy. I took computer science in university and if I get enough money would like to go back to take a degree in aerospace engineering. Until then I have to use fancy math things to make it look formal enough to be taken seriously.

Ps. Read last post on previous page, it's actually on topic.

Palomar · 2005-08-03 15:38:46

Ok English-type people, I just used a dangling participle. I should have said "thing to which it applies" rather than "thing it applies to". Tough, I'm a math-type guy. I took computer science in university and if I get enough money would like to go back to take a degree in aerospace engineering. Until then I have to use fancy math things to make it look formal enough to be taken seriously.

*At a university...sure. Vulcan Science Academy, right? You've been sent back in time to assist in the development of technology, admit it.

To say you're a math guy is an understatement. You are a Megabrain.

Another space walk being considered?

Another spacewalk a 'remote' possibility
With a successful spacewalk repair job today, engineers believe the shuttle Discovery's heat shield is in good shape for re-entry and landing Monday. But one question mark remains: What, if anything, to do about a damaged insulation blanket just below commander Eileen Collins' left cockpit window.

http://www.spaceflightnow.com/shuttle/s … va/]Source

--Cindy

P.S.: They're considering this a potential debris problem, not an entry-heating problem.

SpaceNut · 2005-08-03 20:21:06

I am sort of wondering if the thermal blanket was damaged by the window shield that fell off earlier while waiting to launch?

GCNRevenger · 2005-08-04 09:05:56

They non-destructively tested the specific area of foam where the large strip came off. There weren't any voids or gaps between foam and skin. That's according to a televised interview with Eileen Collins while on-orbit. http://www.napa.ufl.edu/2005news/shuttlefoam.htm]This web page says the foam was examined with X-ray backscatter as well as tetrahertz imaging.
I still think the problem is low pressure air causing foam bubbles to burst, which forms voids in the foam as well as between foam and skin. That means voids didn't exist at lift-off but did form at altitude, once voids formed the foam failed at that spot.
Another solution is an adhesive binder. We already talked about wrapping the foam in some sort of containment skin; I prefer film to mesh because film produces an aerodynamically smooth surface, less drag and no foam loss at all. However, another solution is an adhesive that binds foam to the tank more strongly than the foam holds itself together. That means if foam fails it will fall off in small pieces rather than peal off. Theoretically chunk diameter should be equal to foam thickness. The foam is 1 inch thick over the "acreage", but gets 2 inches thick in close-out areas and PAL ramps are 7 inches thick.
When I participated in a medieval recreation society we used closed-cell foam inside steel helmets. After years of use the foam would become crushed and have to be replaced. Double-face carpet tape held the foam more strongly than the foam held itself together so it crumbled when trying to remove the it. We had to use a paint scraper to remove the foam and scrape off tape, the metal surface (or paint surface) had to be clean before applying new tape or the tape wouldn't stick. Fresh tape could be pealed off, but the adhesive of old tape set. Experience showed chunks the full thickness of the foam were only as wide as foam was thick, but some pieces did come off that were 1/2 thickness and diameter up to 4 times thickness with a rough tear surface, chunk thickness varied between 1/4 and 3/4 foam thickness. For 1/4" foam that meant 1" diameter chunks roughly 1/8" thick. If that holds for ET close-out foam that would mean the largest chunks would be 1" thick and 8" diameter, most chunks from 2" foam would be 2" diameter.

"Non destructive" huh? I wonder, did they EVER test the foam on the PAL ramps like they did the bipod foam? Or did they only cut up bipod samples and called it good...

I don't think any adhesive binder is going to be good enough, because it still can't ensure - and by ensure I mean literally - that the foam coming off the tank is in SMALL pieces. Where did you get this assumption that maximum "chunk" size would be no larger then the foam is thick? I'm not sure that I buy that... Experience with relativly modest blows issued by hand and the riggors of launch combined with bursting bubbles are two quite different situations.

The obvious solution is really quite simple, you take either a mesh (say, kevlar) and press that into the foam just after it is applied so that it sticks and lays flush (say, with a teflon rolling pin or something) or else you get some seriously strong coating material like high-end reactive curing Polyureas and spray the finished tank. All manually applied foam still needs to go in a big way.

SpaceNut · 2005-08-04 11:01:11

Would removing the foam along the ramp and putting in heaters cause a new problem for the edge adherance along the length on both sides of it.

The idea of pushing in the mesh might not be all that easy to do but it is worth a try. You should send it into the return to flight email address, I think it is still active.

Palomar · 2005-08-04 13:22:54

http://news.yahoo.com/s/ap/20050804/ap_ … RPUCUl]4th spacewalk ruled out

*Now there is supposely absolutely no problem posed by the thermal blanket.

SPACE CENTER, Houston - NASA told space shuttle Discovery's astronauts Thursday that a spacewalk to repair a torn thermal blanket will not be necessary.
Mission Control told the crew of seven that the shuttle will be safe for re-entry with the ripped blanket below the cockpit window.
The space agency had been considering sending the astronauts out to snip away part of the blanket for fear a 13-inch section weighing just under an ounce could tear away during the return to Earth and slam into the shuttle, perhaps causing grave damage.
It would have been the fourth spacewalk of the mission, and the second time during the flight that the astronauts had to step outside to repair the shuttle's thermal protection and reduce the risk of another Columbia-type tragedy during the trip home, when the spacecraft passes through the blowtorch heat of re-entry.
"We have good news," Mission Control radioed to Discovery. The mission management team concluded that the torn blanket "is safe for return. There's no issue."
An analysis showed that there would be no danger to the shuttle if a section of the blanket ripped away during re-entry, and wind tunnel tests in California showed the same thing, meaning no spacewalk will be necessary, Mission Control said.

I certainly hope so. But one astronaut is borrowing a phrase from Kennedy (at a time like this, borrowing from speeches always sends up a little red flag with me) and they're sounding a bit TOO reassured, IMO.

I did happen to catch an animated illustration of what damage that thermal blanket could potentially do, on ABC Nightly News last evening. It looked serious.

Best wishes to the crew like always. I hope they're right.

--Cindy

SpaceNut · 2005-08-04 13:42:24

They are currently doing wind tunnel test at Glenn to see if it could be a problem.
While the location of this is in a cooler one as compared to the under belly it still could be whiped around if it comes lose until it either damages the shuttle or comes off all the way on re-entry.

By the way these are the same facilities that were part of the aeronatics cuts that finally were funded.

Links were on the spacetoday.net site for the wind tunnel testing over the last few days.

RobertDyck · 2005-08-04 16:59:04

Could they apply 1" foam over the affected parts, then glue on (with adhesive stronger than foam) a shaped block of open cell foam with a polymer film skin sealing the block? The film would prevent humidity from getting in during at the cape, open cell won't burst during ascent, and the film could be made with a patch that blows out when internal pressure rises to let gas escape. The 1" layer of closed cell foam would provide temperature protection from the cryogenic tank, the open cell wedge would provide air deflection like the current ramp. If the open cell wedge is applied while spray-on foam is still wet, the spray-on foam would deal with irregular shapes such as bolt heads. I immagine this is similar to the current process, just replace the adhesive for the wedge with something stronger. Or is the problem the underlying closed cell foam weakening due to burst cells, and tearing off due to aerodynamic pressure from the wedge? Hmm. Would it work better if the wedge were glued directly to the metal? You would have to seal the wedge with a gas inside that has no humidity or liquefy at LOX temperature. Of course that wouldn't work on the [tex:2e19d1fa15]LH_2[/tex:2e19d1fa15] tank; the only gas I know that wouldn't liquify at [tex:2e19d1fa15]LH_2[/tex:2e19d1fa15] temperature is helium. Hmm, or could you fill the open cell foam block with helium and seal it in with film. That would eliminate the SLA-561 under layer that PAL ramps on the [tex:2e19d1fa15]LH_2[/tex:2e19d1fa15] tank have. The SLA-561 layer was blamed on loss of the PAL ramp for Columbia.

RobertDyck · 2005-08-04 17:11:51

Correction: the document I quoted did talk about "tetrahertz" imaging, but "tetra" is not a valid metric prefix. I did a search on NASA's web site rather than the foam manufacturer; I found NASA's term is "terahertz". That makes a lot more sense. "Tera" is the standard metric prefix for [tex:a329c4479c]10\footnotesize^{12}[/tex:a329c4479c]. http://www.nasa.gov/pdf/63758main_TPS_F … T.pdf]This document talks about imaging from [tex:a329c4479c]10\footnotesize^{11}[/tex:a329c4479c] to [tex:a329c4479c]10\footnotesize^{13}[/tex:a329c4479c] hertz, the portion of spectrum between microwaves and infrared.

GCNRevenger · 2005-08-04 19:18:56

I don't think there is a way you could possibly ensure that the whole PAL ramp wouldn't just tear away with sufficent certainty if it were just glued onto the underlying closed-type foam or directly to the metal if the thing is one big sealed block. If it were to tear away, the whole thing would come loose.

You are thinking about this too hard, its really very simple, that NASA was getting ready to tear off the PAL ramps as a future upgrade to the tank anyway, since they probobly aren't nessesarry at all. A few "ramp free" alternatives were also cited in the documents from the ET office.

And please, please please don't get fixated on just the PAL ramps, that is like patching only one leak in a sinking ship with dozens of holes and a rotted hull, ALL sources of dangerous foam need to have an effective counter.

RobertDyck · 2005-08-04 20:40:44

Replacing or eliminating the PAL ramps combined with an adhesive that doesn't permit foam to peal off means only small bits fall. That leaves them where they thought they were.

The only remaining technique is a polymer film wrap. A mesh would still let bits fall through the holes; no better than a strong adhesive, just as heavy as film, and unless you found a way to recess the mesh within the foam it would provide aerodynamic drag. A wrap holds all small particles in, as well as protecting foam from air flow pressure and a smooth air flow surface. STS-1 and 2 painted the ET, removing the paint reduced weight by 1000 pounds, 0.5 tons. Expect a polymer film wrap to weigh about that much, reducing cargo capacity by an equal amount. Actually it would reduce cargo to lowest orbit by that amount, a higher orbit requires more fuel so it would reduce cargo capacity to ISS by an amount greater than weight of the film. Shuttle can lift 27.500 metric tonnes to 204km orbit @ 28.5° inclination, or 16.050 tonnes to 407km orbit @ 51.6° inclination. Using that ratio it would mean 0.8567 US ton reduction in lift to ISS. But the film may weigh slightly more than paint, so as a rough rule of thumb say 1 metric tonne reduction to ISS. Is that acceptable?

GCNRevenger · 2005-08-04 21:47:55

I don't buy your assertion that adhesive will ensure - and I mean ensure - that foam shedding won't still be a problem. Everything you know about the behavior of foam on adhesives in the common every-day kenetics is irrelivent, since the material is exposed to such different and greater stresses during the riggors of acent. Why wouldn't the outter 9/10ths of the foam still shed as huge contiguous chunks, leaving behind only the little bit actually in contact with the foam? The possibility exsists, so there needs to be another system to counter it.

A few small bits shouldn't be a problem, and a mesh would be much lighter then a heavy elastomer coating like I had in mind. Apply it while the foam is still curing, and press it into it flush with a rolling pin or something. Problem solved... But anyway, I expect that a very thin polymer film isn't going to be good enough, it needs to be much heavier then paint, so I would expect double the mass penalty that you have cited. I am also concerned that expanding gasses would build up under it too much from the foam we know that cracks, so you would have to punch holes in it and make the contour less-then-laminir anyway.

Acceptable? Thats the wrong question to ask... It will be acceptable to NASA if they like it or not, if it cuts down ISS payload too much, thats just too bad, they will have to lighten the load somehow. A REAL fix to the foam problem is a requisit before Shuttle flies again.

srmeaney · 2005-08-05 05:15:31

A few small bits shouldn't be a problem, and a mesh would be much lighter then a heavy elastomer coating like I had in mind. Apply it while the foam is still curing, and press it into it flush with a rolling pin or something. Problem solved... But anyway, I expect that a very thin polymer film isn't going to be good enough, it needs to be much heavier then paint, so I would expect double the mass penalty that you have cited. I am also concerned that expanding gasses would build up under it too much from the foam we know that cracks, so you would have to punch holes in it and make the contour less-then-laminir anyway.

Whats wrong with a nylon Sock covering the Fueltank?

Also, with NASA's new not worth a fourth space walk philosophy in face of the exposed thermal blanket near the window, We forgot to ask: What four square foot panel fell off the shuttle during launch??

If this is the same bunch of idiots who decided to land Columbia based on the rather nice explosive spray of red ceramic being nothing to worry about, they need to be taken out and shot as traitors (Sorry, I meant promoted sideways into the department of Education).

GCNRevenger · 2005-08-05 07:07:15

Nylon mesh would still be awfully dense considering the thickness it would have to be, and it isn't as strong as other fabrics/meshes like polyaramides or UHMW polyethylene. Probobly also has inferior thermal properties, which is a concern since this stuff will be pushed through supersonic air.

The fourth spacewalk issue shouldn't be a big deal, it shouldn't be a serious reentry hazard since Shuttle reenters belly-first, it would just fly off above and back away from the orbiter. Its only a concern during the glide phase, and then only a minor one. Its a question if they want to risk extra repairs in the hanger after landing, not the safety of Shuttle vaporizing like Columbia.

The decision to land Columbia wasn't flawed for one very simple principle: You don't worry about things you can't fix. A rescue would have been impossible, a repair would have been impossible, a non-fatal reentry would have been unlikly if NASA knew about the damage or not. So even if they knew, the only thing they could have done was crossed their fingers and hoped for the best. Columbia was doomed the day that NASA decided to keep flying Shuttle as-is after wing-foam impact damage was discoverd after an earlier flight.

Palomar · 2005-08-05 10:34:31

*Thought I'd put this here rather than create a new thread:

http://science.nasa.gov/headlines/y2005 … tm]Shuttle & ISS glide across sky like bright stars...

for folks in the "ground track": Southern Florida, central Texas, Mississippi River Delta. August 6 & 7.

Side by side apparitions of two bright spaceships are rare and beautiful.

My husband and I saw the ISS and one of the Shuttles pass over in this manner in the mid-1990s. It really is an awesome sight; indeed, like big bright stars gliding swiftly along.

Which ship is which? The brighter light is the shuttle. Although Discovery is smaller than the ISS, its super-white top reflects more sunlight. Both ships should be easy to see in the deep-blue dawn sky.

See reference to Mars as well.

--Cindy

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#251 2005-08-02 17:30:48

Re: STS-114 Mission Coverage and Discussion

#252 2005-08-03 04:30:20

Re: STS-114 Mission Coverage and Discussion

#253 2005-08-03 05:54:09

Re: STS-114 Mission Coverage and Discussion

#254 2005-08-03 07:22:10

Re: STS-114 Mission Coverage and Discussion

#255 2005-08-03 10:01:05

Re: STS-114 Mission Coverage and Discussion

#256 2005-08-03 10:27:29

Re: STS-114 Mission Coverage and Discussion

#257 2005-08-03 11:10:23

Re: STS-114 Mission Coverage and Discussion

#258 2005-08-03 11:53:55

Re: STS-114 Mission Coverage and Discussion

#259 2005-08-03 12:26:32

Re: STS-114 Mission Coverage and Discussion

#260 2005-08-03 12:51:30

Re: STS-114 Mission Coverage and Discussion

#261 2005-08-03 13:11:43

Re: STS-114 Mission Coverage and Discussion

#262 2005-08-03 15:38:46

Re: STS-114 Mission Coverage and Discussion

#263 2005-08-03 20:21:06

Re: STS-114 Mission Coverage and Discussion

#264 2005-08-04 09:05:56

Re: STS-114 Mission Coverage and Discussion

#265 2005-08-04 11:01:11

Re: STS-114 Mission Coverage and Discussion

#266 2005-08-04 13:22:54

Re: STS-114 Mission Coverage and Discussion

#267 2005-08-04 13:42:24

Re: STS-114 Mission Coverage and Discussion

#268 2005-08-04 16:59:04

Re: STS-114 Mission Coverage and Discussion

#269 2005-08-04 17:11:51

Re: STS-114 Mission Coverage and Discussion

#270 2005-08-04 19:18:56

Re: STS-114 Mission Coverage and Discussion

#271 2005-08-04 20:40:44

Re: STS-114 Mission Coverage and Discussion

#272 2005-08-04 21:47:55

Re: STS-114 Mission Coverage and Discussion

#273 2005-08-05 05:15:31

Re: STS-114 Mission Coverage and Discussion

#274 2005-08-05 07:07:15

Re: STS-114 Mission Coverage and Discussion

#275 2005-08-05 10:34:31

Re: STS-114 Mission Coverage and Discussion

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