The tile damage is from foam debris and measures 3.48-inch long and 2.31 inches wide at the base of the 1.12-inch thick tile. Today Team 4 met to discuss three repair options. We have the black emittance wash, which will keep heat from building up in the cavity. Another option is a gun that ejects a heat-resistant, caulk-like material into the cavity. The third repair option is the overlay, which is a 15" x 24" sheet of silicon carbide that gets augered into the tiles to cover up the damage.
Tomorrow morning we have a early morning meeting to start testing and viewing some more analysis results. Schedules and timelines in all groups are affected so you can imagine this is a very big group effort. However, if the analyst can prove that there will be no structural damage to the Orbiter upon re-entry, then we may fly in the as-is condition and it would be safe for the crew to return. However, if we do have to perform a repair option, it would require a two-person crew spacewalk, and be rather lengthy because of the location of the damage on the Orbiter.
I expect tomorrow to be a long day, but it's well worth it when I am working with dedicated engineers and analysts. Seriously, people are working so hard and it's great to see their passion for the space program and the crew. I love coming to Houston to support the mission because you never know what to expect and when an issue comes up, great minds collaborate and IT'S GREAT!
So here's a picture of the damage we're mostly concerned about.
43 comments:
Have any of the above 3 fixes ever been used before to fix a tile while in orbit?
They have previously not been used for on-orbit repairs. They have however been through testing and are available to the crew on-board. There are some crewmembers that are trained to use certain methods as well. More testing is being performed here at JSC as well stress and areoheating analysis from various centers.
Is there any advantage to flying in an 'as-is' condition, other than it would save the time for other mission objectives/issues? Is there any downside in conducting the repairs even if they are not strictly needed?
And can more than one repair option be used? It seems, as an example, that option 2 with the spraying foam, and option 3 covering the area could both be used together. Could they not, for some reason?
Thank you for your excellent blog.
This is an issue of concern for the space program itself. You just can't let it happen at just about every launch there is, and I wonder: are you guys taking some kind of steps to prevent this kind of damage to the shuttle? It's becoming more and more frecuent, or maybe this kind of damage was always present but came only to our attention after the Columbia disaster
mytho: you are exactly correct. This is now seen more public because of the recommendations from the Columbia Accident Investigation Board. Before Return-to-Flight (STS-114), NASA began on-orbit imagery inspection which provides up hi-res photos to inspect for any debris hits/anomalies and inproved ground-based cameras for launch. Also, the development of on-orbit repairs were also a recommendation from the CAIB. After doing some research on previous mission post-flight reports, I have seen many damages, some a whole lot bigger in dimension. But every area, tile thickness, and damage is different and requires its own analysis. At this point, there is no way to completely eliminate ET foam debris and we still face other issues such as the blanket lifting up last flight or protruding gap fillers. I will tell you this, post-flight, we return to KSC and target all in-flight anomalies to prevent them from occuring. Debris is just an issue that will always come up, but we have fixes to return the crew home safely.
As for the previous posting about flying in the as-is condition....If analysis proves that this damage is suitable for re-entry, then that's great! When we do the imagery inspection on the lower surface tiles, we have a criteria that we go by. Not every tile damage is documented. We take the tile thickness and location into consideration. This one definitely exceeds the criteria because of the depth of the damage and how thin the tile is in that location.
But aside from what you mentioned about flying back in the as-is condition for other mission objectives is incorrect. Spacewalks are very risky for astronauts. If the analysis proves good, it's a safe condition for our astronauts and our temperature loading is not a threat to the structure for re-rentry.
..and the option 2 that i mentioned is more like a putty material. some drawbacks to the plate is the size of the plate for such a small damage. The plate gets "screwed" into the tiles around the perimeter of the 15" x 24" plate. So it could creat more damage to the adjacent tiles that the other repair methods could cause.
As you suggested, if you were to put the option 2 material, which emits the heat to not get into the cavity, testing would have to be done that you wouldn't get a hot spot if you were to cover it with the plate creating localized heating down into the structure.
You provided great comments. thanks for reading!! -D.
I'm curious; what kind of foam causes this damage? I tend to think of foam as soft fluffy stuff, not something rock hard that can make holes. :)
Why don't they put the foam on the inside of the tank? I'm sure it's much more complicated than that but it seems like the best solution.
Seriously why dont they just put the shuttle belly out on takeoff . that would protect the tiles.
I work in a mechanical field, and it's by no means as complex a field as aerospace travel, however when we have a broken or worn part, we simply replace it. I was wondering how difficult it is to actually replace broken tiles while in space, and if it would be possible, why not provide several spare tiles in the kit of repair parts they already must have so that this might be done in emergency situations like this.
Pardon my total lack of knowledge here:
When does this type of damage happen anyway? I assume its on assent and during orbit, not on the ground pre-takeoff.
So, why don't yall just put some semi soft coating that will burn up on re-entry over the tiles before liftoff? (I assume the tiles are already designed in a modular fashion for easy repairs.)
A one use protective layre that could stay on until burning off on re-entry/decent perhaps might save a lot of dings, worry and repairs.
I dunno its just a though. I suspect that speed during takeoff is far less than during landing, therefore temperature would be cooler. Also unsure if such a coating might produce insumountable drag.
Is the 15 x 24" plate made of silicon carbide (SiC) and not silica carbide? Just a few thoughts. Have you ever considered having the astronaut hand tool a patch of the same refractory material the tiles are made of? It is a fibrous aluminosilicate if I recall and very easy to carve with a blunt tool. The patch could then be "glued" in place with the caulk like material. That should give slightly better thermal insulation than the caulk alone. Also, the photos you guys take of the damaged sections are pretty darn good too. (At least from the space station) If a several photos could be taken from different angles you might be able to get a 3D image. With that you could tell the astronaut what shape patch to cut out while still in the shuttle.
I'm curious, and have wondered for a few years now.. At what point would Mission Control consider leaving a shuttle in orbit for use but not for re-entry, due to damage, or is this even an option?
I imagine the ISS crew could make use of a shuttle on hand for a few things if one was deemed unfit for re-entry, like the capture and repair dying satellites or other experiments. Returning a shuttle's crew to Earth might present a minor logistical problem depending on their number for the mission, but there are other ways to handle that.
I'm a middle-aged orbital and re-entry vehicle with a few missing pieces and I'm enjoying these comments!
Fark says hi
http://forums.fark.com/cgi/fark/comments.pl?IDLink=3001252
Actually very interesting, hopefully you don't get too much spam out of this
I wonder ... why not just create two layers of tiles that are each about half the thickness of current tiles? Then if one layer is damaged, at least the next will protect it enough to land (albeit with some thermal damage).
One probably completey unworkable way (that my brain just popped up with) to keep the foam from flying off:
Cover the whole dang tank w/some kind of mesh. Think chicken wire (but able to withstand the stress of the high airspeed during takeoff). The foam could bubble all it wanted, but the mesh keeps it in place.
I wonder how much weight that'd add to the whole assembly. Hmm.
About the foam flying off teh tank on take off- I have a one word solution.
Duct tape.
Aww shoot. That's two words.
Maybe I'm being naive, but wouldn't the better solution be to solve the disentigrating foam problem? It seems to me that a lightweight nylon (or similar substance) netting could be embedded into the foam to keep it from flaking off.
Maybe that's too simplistic, but sometimes simple is best.
Has any study been done to replace the foam with a less destructive substance? Areo-gel, possibly? Super insulation without the weight / mass / kinetic energy problem?
// more slashies
Stickytape fixes everything. :)
I'm also curious to know if the tiles can be replaced in flight?
Out of curosity, and I'm sure there is a good reason. Given that these tiles seem to break/get damaged fairly frequently, why does the shuttle not carry a couple of spares?
I know that doesn't help the situation they are in now and they need to keep the weight down - but it seems that they break often enough to warrant it. No?
I sure as hell hope you get the whole space shuttle situation figured out.
On a brighter note, who do you study Judo under???
You know, I remember seeing a video after Columbia of a piece of foam totally destroying some of these tiles. I think it was 60 minutes or something. This doesn't look nearly as dramatic as that video would have suggested.
Damaris,
*Please* post more information about the decision to go ahead with landing without a repair attempt.
The LCD video is incredible; I was wondering how you simply "eyeballed" the surface for damages.
Meanwhile, Neptec says that the damage burrowed all the way through the affected tile; is the location of the tile why this isn't as much a concern?
(Others--LCS video here.)
Very cool.
I'd imagine that most of the suggestions here on how to prevent such damage from ever happening again, would add too much weight, thereby reducing how much cargo the space-truck can haul to the ISS in one go.
Plus, they'd all require many millions of $ in R&D alone, before we even look at the actual implementation costs. Just not worth it for a system that will be retired soon anyway.
Couldn't you use a combo of the putty and that black emittance wash over the putty?
I've had the same thought as another anony. Why not use a light nylon mesh to cover the external surface of the tanks or cover the tanks and add a thin layer of foam to stick it to the structure. It would act like rebar does in concrete to bond the substance together. Just my 2 cents.
or to add to what Kevin said, instead of just one method, use the panel to cover the gap, then paint with the black emittance, or putty, than plate, than paint...
P.S. EVIL!
Oh boy. Once you get posted on Fark you're going to have A LOT of comments. I've seen your blog before (I forget how I found it) but I wish you the best of luck in achieving you dream.
-Andy
www.andyt13.com
I'm curious why NASA does not have a filling compound on the ISS than can fill in the hole for re-entry.
I would think that a paste of an un-fired ceramic compound, such as silicon carbide or Alumina, could be injected into the hole.
The heat of re-entry would sinter the ceramic compond and form a temporary "Bandage" sufficient to provide a temporary heat shield.
You could even pre-sinter with a laser or tourch then re-apply to cover shrinkage points.
I wonder why NASA hasn't seen fit to add a shuttle repair module to the space station?
Could some type of protective coating be put over the sensitive areas of the shuttle before take-off? One that would burn off during re-entry?
I can Fedex you down a couple rolls of duct tape for the next shuttle launch if need be.
Best.
I'm not an expert here, but as an engineer and space enthusaist I'd like to take a stab at answering everyone who has asked why the shuttle doesn't simply carry spare tiles.
If memory serves, no two tiles on the shuttle exterior are identical. The only way to make sure any damage can be fixed is to carry a complete set of spare tiles into orbit. Even limited to the areas most at risk of damage, that's a lot more mass and volume than will be needed to perform the repairs.
Also, tile replacement is a relatively involved process. Sure it'll fix the damage, but it involves further compromising the heat shield in the process. Not something I really want to try in orbit, without the facilities to make sure it's done right the first time.
The repair options the author lists are more along the lines of a compact spare, like most cars have in the trunk. Are they the ideal fix? No. Does they need to be? Also no. They just have to last through one re-entry - long enough to get home safely and put in a proper replacement.
Just 2 words:
Duct tape.
Responding to a few suggestions folks have made (disclaimer: I don't work in aerospace, but I read a lot).
Replacing tiles on orbit -- that's a non-starter because every tile is more or less unique in its shape and thickness. I know they all pretty much look like rectangles, but they're not. They each have their own distinctive shape to conform to the shuttle's curved surfaces, etc. You'd have to carry with you an entire set of replacement tiles, which is obviously a no-go.
A better suggestion there would be to have some sort of tile-making machine on board to make copies of whatever got damaged. However, in terms of weight and complexity, I'm sure that's a pretty difficult proposition too.
Even if you could make a replacement tile on board, there would be the problem of fully extracting the old tile and cleaning off the sub-surface sufficient to properly glue the new tile in place. Fine detail work like that is really, really hard in a EVA suit.
Also, these tiles aren't hard and strong like bathroom tiles. They are explicitly designed to be lightweight and immensely insulative. What you get out of that equation is a low-density, porous material that you can literally poke holes in with your fingers if you want. This, I gather, is the prime reason why on-orbit repairs are seen to be so risky. It would be very very easy for an astronaut to accidentally damage more tiles while clunking around in those bulky EVA suits.
Really, we need better space suit technology. Thankfully, there are people working on that problem.
As for the suggestion of carving some type of patch to fit in the gouge, there is again the problem of detail work and accidental damage, combined with the problem of accurately molding the replacement piece. If you've ever tried to make something to fit snugly into an irregularly shaped hole, you'll appreciate the difficulty there.
Launch belly-out: I'm sure aerodynamic concerns rule this out. The whole system was designed to work in the belly-in configuration (for better or worse) and changing that design would have enormous engineering repercussions. I'm not saying it's a bad idea, only that it's more complex than "just flying the shuttle belly out".
The caulk gun option seems the most viable for most repair scenarios (I agree that the idea of bolting the silicon carbide plates on is inherently risky enough that you'd only want to go that route for some really major damage), but wouldn't it be nice if someone could develop a spray-can type application of the same aluminosilicate material with enough binder mixed in to make it stick. That would allow the astronaut to fill in the hole without actually having to touch the belly of the orbiter themselves.
Damaris:
This is THE chance of a lifetime to test the STA-54 ablative goop and see how it performs!
Please don't pass it up! It's a chance to learn something. Especially if this is a non-critical repair, this is the time to test the technology.
Richard B. Drumm
VP,CAS
Regarding the idea of carrying extra tiles as replacements...if only the tiles were like bricks, all the same size and shape. But all of them aren't the same. So many of them are uniquely shaped according to their location, in order to maintain a smooth, aerodynamic surface. The numbers visible in the photo above identify each tile to facilitate replacement between missions. They just look up the number to determine its proper specifications. But that's one ground.
Fabricating a replacement tile out of a blank using hand tools, on orbit, probably isn't nearly as easy as it sounds. My uninformed guess is that some sort of portable CAM device would be required...at a substantial weight/space penalty.
Since this is a survivable nick, from what I understand, isn't it the perfect time to test one of these repairs? If the patch fails completely, we'd know not to try that again.
if one of the repairs were to be tested and failed it could do more damage than not having a repair at all. i'm assuming most of the work that Damaris' team is doing is to determine whether the probability of a catastrophic failure of their repair is greater than the probability of the damage itself causing a larger failure.
Hi Damaris!
Just wanted to let you know how much I've been enjoying reading your blog since I found it a couple of days ago. It's fascinating getting "the inside story" from someone involved in the shuttle program, especially someone with such an obvious love of and passion for space exploration, your enthusiasm and desire to Go really comes across in your writing.
It's been particularly interesting hearing your thoughts on STS-118, because this mission has a great personal interest for me, in that some 16 years ago Barbara Morgan was kind enough to send me a lovely personally signed photo and a handwritten letter, after I wrote to hear asking for some advice about the work I do in junior schools here in the UK. I guess you call it "Outreach" over there, but to me it's just been my mission in life the past 25 years or so to go into schools and give illustrated lectures and hold workshops about space exploration and astronomy. It's been something of a personal crusade of mine too to emphasise that girls can grow up to be astronauts just as boys can, there's no difference now. Of course, this is a lot truer over there in the US where girls have lots of role models (including your good self now!) but over here it's not quite such an easy sell; we have a space program, of sorts... I think we supply the ISS with its toilet paper or something ;-) but British kids can't simply grow up to be astronauts, they have to literally move to another part of the world to achieve that dream. But hey, Michael Foale and Priers Sellers did it, so it's possible! (Not for me now, sadly... too old...)
So that's why STS-118 means a lot to me. Whenever I give a talk in a school I always prop two framed photos up by the projector screen or whiteboard I'm using. One of Chriats McAuliffe, who continues to be a source of great inspiration to me, and another of Barbara Morgan - proof that girls CAN Go if they want to! I don't mean that to sound patronising, it's just a sad fact that over here in the UK there are still some unenlightened folk who try and steer girls away from science and engineering subjects at school and towards - well, others, I'm sure you can fill in the names for yourself.
But anyway, I'm finding your blog absorbing reading, and I'll look forward to following your training as it moves forward and telling all the kids I talk to all about your successes.
All the best from the UK!
Stu
http://journals.aol.com/stuartatk/Cumbrian-Sky
what is the most suitable temperature for the comfort of astronauts?
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