1 Time to test the new patching materiel they're supposed to be carrying...

2 That's risky, too. People on the ground are working right now to try to make the decision as to which is the lesser risk.

3 If it's a question of risking two astronauts on the space walk vs. risking the whole shebang on re-entry, then I'd go with the space walk. Or is the risk that the patching materiel itself would cause problems on re-entry?

4

The scary thing is that this icing problem is happening in high summer.  Why did it suddenly become a problem in the last few years?  Because the foam insulation was reformulated due to "environmental concerns."   These shuttles cost something like $1.2B (replacement cost) each in today's currency, and are our only manned space launcher right now. 

I could go on a while, but the message should be clear:

1. We are wasting billions and lives for a questionable,  unquantifiable, but tiny environmental benefit (foam on tanks for ~8-12 launches per year).

2. The environmental movement is killing our space program. And astronauts.  We can only hope at this point that they haven't just killed some more.

I'm disgusted that NASA would let this go on.  They've got no business destroying our space program and national prestige with such abysmal management principles.

5 To the best of my knowledge, the foam reformulation has absolutely nothing to do with the foam loss. It always was an issue and nobody paid attention before Columbia. STS-27 landed with worse damage.

And anyway, read this:
http://www.spaceflightnow.com/shuttle/sts118/070813mmt/

I surprised that AP and Wired pretty much got the story straight (at least in the quotations Steven used). The filler material is between the tiles and not underneath, but it's a minor mistake.

6

If you notice in the picture, every one of the tiles has a unique serial number. That's because every tile is different. They're all machined for the positions they must fill.

To do a repair, the astronaut has to dig out the existing tile and then glue in another one. But the other one won't be precisely right, and maybe the glue won't hold during reentry.

The risk of using the patching kit isn't from the space walk, the risk is losing the ship during reentry when a gap around the patched tile leads to a burn-through, or when the patched tile comes loose and is pulled off.

7

I can't imagine what is going through the minds of the astronauts right now. Do we risk floating off in to space to glue a new tile in to place, or do we say screw it and hope it holds? Not a terribly extensive list of options.

This leads me to wonder why don't they have an escape capsule of some sort on the ISS? Don't these guys watch sci-fi at all? Everyone has escape capsules.

The other possibility I suppose would be to junk the shuttle and have a Soyuz capsule come and take them home, although I wonder how long the ISS could handle that many visitors.

 

 

8 Actual repair techniques available were listed at the link I posted. In short, replacing a tile in space is not possible. Instead, three options are available:
1. Paint the hole's inside with a black paint. This improves the heat removal by radiation
2. Fill the hole with a caulk (and then paint it)
3. Apply a patch, secured with screws into tiles.
As far as I know, tiles are not gouged further for option #3, so the patch is not flush with the surface.

9

The Shuttle can land itself without pilots. One scenario is that the entire crew does stay on the ISS and get evacuated with Soyuz capsules, and the Shuttle gets sent back without a crew.

But I doubt they'll do that.

10

I have to wonder how bad the odds would be before NASA would go with the pilot-less shuttle landing/Soyuz rescue scenario you describe.

Then I imagine being an astronaut on this mission waiting for a large faceless bureaucracy to decide how much I'm worth to them. That's a pleasant thought.

11

Or is the risk that the patching materiel itself would cause problems on re-entry?

I think the risk is that they just don't KNOW what will happen, since it's never been tried before.  They might have this dangerous space walk go absolutely right, the astronauts' work be 100% perfect, and it might STILL fail during re-entry, because of who-knows-why. 

Which is probably what they said when a shipwright first designed a sail-powered vessel.

The difference being, of course, that they don't HAVE to risk the crew; there could be a rescue mission, or the current crew could re-enter via repeated... um... Soyuz(?) capsules from the ISS.

I'm pretty sure I wouldn't want to make the call.  I DO know I wouldn't ever say "Let the shuttle come home alone."  That would kill NASA dead.

12 Didn't I hear something about them working up a simulation in one of their windtunnels? They are trying to duplicate the tile damage as best as possible then check to see how it behaves with and without the patch when subjected to hypersonic plasma.

13

Will, there's no possible way to do this in a wind tunnel. During reentry, the shuttle is moving at 25 times the speed of sound.

Computer simulation would be the only hope, and even that would be problematic. I suspect we don't really understand fluid dynamics at those speeds well enough to really write a decent simulation. And it isn't helped by the fact that near the nose and underside of the shuttle, the air is being turned into a plasma by the heat.

14

It may have been some know-nothing on the radio. It did sound fishy at the time. A couple guys hacking on putty with a plasma cutter would probably look like a simulation to a lot of people.

It's a shame we didn't get more than a basic introduction to hypersonic flow in my gas dynamics classes, but once the molecules start breaking down, everything goes to hell in a handbasket (aka non-linear). They're not going to drop undergrads in that swamp.

Almost all the hypersonic design happening today is done with CFD, and from what I understand, they actually have a pretty firm grasp on what's going on.

15

On a tangental note, every F1 team has a CFD group in house, and a few of the Chief Designers are CFD specialists.  Only one team doesn't have a windtunnel of their own (Spyker, and they're about to purchase the old Team Jaguar factory, which DOES have a 'tunnel), a couple have two.

I'd think that they probably DO have good models for the Shuttle and how it should react during re-entry ("Step 3: A Miracle Occurs").  The problem that I see, however, is that they just don't have actual experience with the patch stuff, how it deals with re-entry and the like.

Which is good and bad, of course.  Good, because they've never had to use it, bad because they don't know how it'll react.

Until they DO use it, they won't KNOW...

16 The Wikipedia article for CFD shows a simulation of the shuttle, but I doubt they're modeling it down to the level of individual tiles, or are capable of figuring out the consequences of slight irregularities at the level of individual tiles.

17

Will, there's no possible way to do this in a wind tunnel. During reentry, the shuttle is moving at 25 times the speed of sound.

NASA do have supersonic wind tunnels, but I don't think they have anything nearly that fast. A quick bit of Googling turned up one that can reach Mach 7, which is still pretty amazing.

Hope they find a solution and that it works.

18

Hmm... Wait a second...Texas A&M... Let me just see...

Ah, there he is. That's who taught my gas dynamics class. He took the Unsteady Wind Tunnel with him to Texas when he left ASU.

19 Good, because they've never had to use it, bad because they don't know how it'll react.

One submits that they did need it once...

I'm not certain why this would be a "dangerous" spacewalk. It's their own vehicle they're working on, so there's no real difficulty in interception. Perhaps it's just the time involved?

Also, just saw CNN run pictures of a NASA test bed... evidently they mocked up the tile setup, replicated the gouge, and used an arc-jet furnace to simulate the plasma at re-entry. Melted a bigger gouge down the tile, but didn't go deep. 'cos, whether that's what would actually happen...

20

I believe the current rescue plan calls for NASA to outfit another shuttle ASAP and send it up within 1 month, and returning with both crews.

 

21

One submits that they did need it once...

Did they have it then?  Did they even KNOW they needed it then?

22 The bottom line:  we need a replacement for the outdated POS known as the shuttle.

23 More or less my point, Duck. (No, they didn't have it then.)

24 The simulation facility is mentioned on the link that I posted. (Obviously, nobody reads reputable websites anymore. No, I'm not bitter.) Basically, it involves blowing compressed air from a tank over an arc furnace which creates a hypersonic flow of plasma.

I used to live near a facility which had an experimental H/F laser, for the Soviet reply to the SOI. An H/F laser is powerful enough to melt satellites in orbit, so the idea was to melt Reagan's toys without launching anything, because launchers can be intercepted by the same SOI kit. Anyway, it works by blasting hydrogen and fluoride through and across an orifice. The hypersonic shockwaves were heard all over the town whenever they fired it up.

I wonder if neighbours of the tile heating and simulation facility are filing noise abatement lawsuits. Those NIMBY people are everywhere

25 The spacewalk is dangerous because it's easy to make a wrong move with the boom and make another hole in the heat shield, which may end located not quite as fortunately over a stringer as the existing one. Haven't you seen Rocket Girls? Remember how someone moved the arm backwards? Ha, ha, only serious. It's not likely that the operator would do the same mistake, but the real danger is in the unpredictable flex of the extension boom.

26 I believe the current rescue plan calls for NASA to outfit another shuttle ASAP and send it up within 1 month, and returning with both crews.

Send up another shuttle within 1 month? Does NASA have the required magic pixie dust to make that happen? Or do they have another shuttle on hand that doesn't require 20,000 engineers and technicians to service it?

Pardon my skepticism. But although "fast turnaround" was one of the selling points of the shuttle program, NASA has never actually managed to do it. They can't; the system is incapable of it.

Considering that NASA, after Apollo, became a jobs program for aerospace engineers, it's not really all that surprising. If Endeavor cannot be patched in orbit, if there is no way to safely get the crew home, those people will either be stuck at the USS Boondoggle ISS until NASA actually can ready another shuttle, or have to come home on Soyuz capsules.

27

I'm not sure that long-term stay at the ISS is possible. The life support system is designed for three people. How long can it support ten?

I believe that it can probably do so for a couple of weeks, and maybe even a month. But how long can it produce breathable air? How long before the food runs out? The supply capsules (Soyuz) are scheduled years ahead; the Russians are no more able to advance their schedule than we are. Maybe less, in fact.

And I'm not sure that supply capsules can be used to evacuate crew.

The ISS has a single Soyuz capsule connected to it at all times. It's the emergency escape for the three normal crew. But evacuating ten is more of a problem.

The reality is that if they can't fix the problem, then they're going to have to risk reentry anyway. There is no alternative.

And if they lose a third orbiter, then that should be the end of the program. Absolutely no more launches, zero, nada. (Myself, I think they should have ended it after Columbia.)