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View Full Version : New possible explanation for Columbia: primer & pinholes



Jigsaw
2003-Apr-05, 04:28 AM
I don't know enough about it to tell, but are they just grasping at straws here, since no big obvious explanation has cropped up yet?

http://www.cnn.com/2003/TECH/space/04/02/sprj.colu.shuttle.investigation.ap/index.html

The theory: Zinc oxide from the launch tower's primer combining with rain to splash onto the Columbia while she stood there waiting, plus also possibly salt spray from the Atlantic, oxidizing and forming pinholes, and then the left-wing carrier panel is hit by a chunk of falling foam during launch and falls off, thus no longer protecting the pinholed wing during re-entry, thus allowing hot gases to get in the wing.

How plausible is this, O Engineers of the BABB? All four shuttles have the same kind of pinholes, apparently. So they're saying that it's only the fact that one of their carrier panels hasn't ever fallen off that has saved the other shuttles from suffering this same thing? That's a scary thought.

SAMU
2003-Apr-05, 06:59 AM
How about this explanation: Explosively violent launch conditions cause one or more of a million things to break. But the shuttle survives launch. Unfortunately, there is no provision in the program for post launch or pre flight (flaming reentry) inspection. Nor is there any inclination to do anything even when some suspicious, possibly damaging, event did happen.

It could cost a hundred million dollars each time to do something (Like launch a rescue/repair mission). If NASA were to launch one R/R mission every year, in 30 years they would have spent as much as a shuttle costs. Unfortunately, NASA has been losing shuttles at the rate of one every ten years. That puts us two times in the hole on the deal.

I think NASA tries to use mechanical or technological means of risk abatement too much. They need to get to the basics of risk abatement. Namely "Don't put all your eggs in one basket". No matter how well built the basket, if you have only one basket, sooner rather than later you are going to lose all your eggs. Of course, sooner or later both the primary and the backup will fail at the same time. But then simple math tells you that if the primary has a loss rate of one in ten years and the backup has a loss rate of one in ten years then the primary and secondary combined failure rate is one in ten years (1/10) times one in ten years (1/10) = one in one hundred years*. I could live with that.

*For those who need the math really simplified 1/10x1/10 =1/100. Or if you want to use your calculator .1x.1=.01

Nanoda
2003-Apr-05, 09:19 AM
That calculation is only true for independant events, ie - rolling dice. The events on the shuttle are more likely to be coupled. For example, the chances of a wildfire burning my house might be 1/1000; same for my neighbour. But if there is one, they'll likely both burn, so the chances of both burning aren't 1/1000 * 1/1000 = 1/1000000. What a morbid example... anyways.

I don't understand your main point, however. Namely, your eggs/basket analogy. All critical systems on the shuttle already have backups. What do you propose they do?

BTW, by mandating orbital inspections, you're introducing new risks. There are already sensors and stuff on the shuttle, so I'm presuming you want someone to go outside and look. This introduces new risks. EVA is hazardous. They might break something whilst out there (tiles are fragile). That hatch they opened might not have closed properly. Your idea as I understand it doesn't seem feasable to me.

BTW, more "baskets" means more chances of failure. There's a saying in engineering: It's easier to put all your eggs in one basket - just make sure you have a really good basket.

FP
2003-Apr-05, 03:55 PM
"Put all your eggs in one basket -- and watch that basket!" S. L. Clemens

Squink
2003-Apr-06, 02:45 AM
Zinc Oxide has a solubility in water of only 0.16 mg/100 ml. Despite Barry's claim: "every time it rained, corrosive zinc oxide washed onto the shuttles", zinc oxide is not usually regarded as corrosive. The chemical is widely used as a sunscreen, and yet there are no reports of people's noses falling off from the corrosive effects. That said, there may be some odd chemistry going on between the zinc and the carbon based lining. If so, the article doesn't detail what the precise reaction involved might be.

tracer
2003-Apr-07, 11:41 PM
That said, there may be some odd chemistry going on between the zinc and the carbon based lining.
Considering that flashlight batteries are powered by the oxidation-reduction reaction of zinc and carbon, I'd say there might be some chemistry going on there, yes.

Squink
2003-Apr-08, 03:27 AM
Considering that flashlight batteries are powered by the oxidation-reduction reaction of zinc and carbon, I'd say there might be some chemistry going on there, yes.

The zinc-carbon cell has a zinc anode, a manganese dioxide cathode, and an electrolyte of ammonium chloride or zinc chloride, which is dissolved in water.
http://micro.magnet.fsu.edu/electromag/electricity/batteries/zinccarbon.html
The source of reduced zinc (metal) on the wing would be ?
I suppose that the aluminum of the wing itself could serve as an anode, if the carbon layer was porous, and there was something in the water capable of dissolving the wing's aluminum oxide coating. I don't know, but just blaming the problem on "corrosive" zinc oxide seems like an example of Bad Chemistry.

SAMU
2003-Apr-08, 05:20 AM
Well the fact is there is no way NASA is not going to send someone out for an inspection after launch, at least for the next few launches. The media will be in a frenzy with the usual post disaster prelaunch questions of "what are you going to do?". According to A&E they are already considering the following meens.

An astronaut enters the cargo bay and floats free. The shuttle pulls away and stops. The shuttle then goes into a slow roll so the astronaut can get a good look, possibly with a camera. The shuttle stops its roll and rises back up to capture the floating astronaut.

Sounds ok to me.

The next question is; what then? Well if there is damage you can't fly it back unless it can be fixed. If it can't be fixed it will have to be either abandoned or flown back on auto/radio or by a real gutsy (nutzy?) pilot. Of course another shuttle mission would have to be launched for a more detailed evaluation and to evacuate the surviving astronauts. Which means that another shuttle would have to be maintained on standby before any further launches. If tile damage I would suggest taking a mold of the damaged area with some dry powder molding material. Wet molding material woldn't work in vacuum. Dry molding can be reused if the astronaut taking the mold doesn't get a good mold the first time. When he gets a good mold the mold can be brought back into the shuttle for stabilization with somthing like plaster of paris for return to earth. The mold can then be used to make a custom patch for the damaged area.

If the damage is extensive then an evaluation will have to be made as to whether the repairs can be made in several missions, before more damage occurs due to the length of time it remains waiting on repair and cost/return factors.

SAMU
2003-Apr-08, 05:39 AM
That calculation is only true for independant events, ie - rolling dice. The events on the shuttle are more likely to be coupled. For example, the chances of a wildfire burning my house might be 1/1000; same for my neighbour. But if there is one, they'll likely both burn, so the chances of both burning aren't 1/1000 * 1/1000 = 1/1000000. What a morbid example... anyways.

I don't see two seperate shuttle launches as coupled. Two launches are two seperate rolls of the dice. Just because you "lose" on one doesn't mean you will lose on the other. And a win on the second one makes the lose on the first into a win. Unless you roll two loses in a row. But the formula for that is odds! (odds factoral or odds times odds)



I don't understand your main point, however. Namely, your eggs/basket analogy. All critical systems on the shuttle already have backups. What do you propose they do?.

All systems have backups except one. The shuttle airframe itself. Except if you consider the rest of the shuttle fleet as backups. NASA didn't see it that way. I think they do now.



BTW, by mandating orbital inspections, you're introducing new risks. There are already sensors and stuff on the shuttle, so I'm presuming you want someone to go outside and look. This introduces new risks. EVA is hazardous. They might break something whilst out there (tiles are fragile). That hatch they opened might not have closed properly. Your idea as I understand it doesn't seem feasable to me.


See message above.

skeptED56
2003-Apr-08, 09:22 PM
An astronaut enters the cargo bay and floats free. The shuttle pulls away and stops. The shuttle then goes into a slow roll so the astronaut can get a good look, possibly with a camera. The shuttle stops its roll and rises back up to capture the floating astronaut.


Here is an article from space.com. Read about the AERCam that was tested in 1997 on STS-87 it was only tested in the shuttle cargo bay but experts believe that it can get external view of the shuttle:

http://www.space.com/businesstechnology/technology/nasa_robots_030209.html


also about the AERCam:
http://www.skyrocket.de/space/index_frame.htm?http://www.skyrocket.de/space/doc_sdat/aercam-sprint.htm

Shouldn't the shuttles be equiped with something like this?

ToSeek
2003-Apr-22, 04:48 PM
Top ten failure scenarios (chart) (http://www.spaceref.com/news/viewsr.html?pid=8923)

DALeffler
2003-Apr-22, 05:19 PM
From CBS:

http://cbsnews.cbs.com/network/news/space/current.html

ToSeek
2003-Apr-23, 03:50 PM
Flawed foam found on Columbia twin tank (http://www.newscientist.com/news/news.jsp?id=ns99993657)

ToSeek
2003-Apr-23, 05:27 PM
Missing piece believed to be 't-seal' (http://www.msnbc.com/news/867336.asp)

The thinking now is that the piece seen floating away from Columbia was a "t-seal" from the front of the left wing.

BigJim
2003-Apr-23, 06:11 PM
I have an idea! Let's build a ten-billion dollar space station for the sole purpose of taking high-resolution photos of the shuttle while in orbit! Even better, we could add a complicated and dangerous EVA maneuver to manned space missions to look for damage that may not exist and probably wouldn't be seen even if it did! In addition, that would require reviving the MMU, which weighs hundreds of kilos, but space missions are never weight-strapped! Don't we all remember when on early shuttle missions, they would lose many tiles even being transported to the launch pad? (http://quickstart.clari.net/qs_se/webnews/wed/cf/Ashuttle-problems.Rqjo_DFO.html) This is not the first mission on which tiles have been lost!
Many of these suggestions are verging on ridicuolousness. The obvious answer is to replace the aging shuttle, which costs about $600 million a flight. Even the expendable Soyuz is far cheaper per flight than the shuttle.

I believe the current discussions about extending the life of the shuttles to 2020 are ridiculous and miss the key point, that the shuttle is outdated. It is a product of 1970s technology and costs far too much to be economic. What is really needed is a revival of the cancelled X-33 program to provide affordable, common access to space. Rutan's SpaceShipOne will hopefully be the forerunner of a new age in private spaceflight, and NASA will have to catch up. NASA does not need to plan having a shuttle on the pad on each flight or start designing an external camera system for the shuttle. It needs a new focus. There are two main steps where NASA should focus its efforts in the next ten years:

1) Designing an SSTO (http://www.islandone.org/Policy/SSTO-ASpaceShipForTheRestOfUs.html)
2)Pursuing an agressive Mars exploration program with a Sample Return aimed for the end of the decade, and then starting a humans-to-Mars program with a ten year timeline (http://www.nw.net/mars/)

Designing a 20-year old vehicle to operate for twenty more vehicles is neither productive, cheap, nor valuable in the long run, and we will essentially be putting all of our eggs into a glass basket.

I liken the current situation to this analogy:
You have four old cars. However, these often get punctured tires (heat tiles fall off). Usually, this is a minor thing that you do not worry about and you continue to drive them every so often. One day, though, one of them gets a flat tire! What should you do? The answer is not to have someone get out every mile to check the tires, and it is not to build a camera that can continually inspect the tires, and it is not to stop driving. The answer is to provide a simpler, more robust and capable system that has tougher tires and is cheaper to use. Then, all of our eggs will not be in one basket but rather will be continually supported by the great chicken of space exploration.

Sorry, I'm starting to ramble, but I think you get my idea. :)

BigJim

newt
2003-Apr-24, 09:44 AM
With apologies to the OP Jigsaw, as this is off-thread, BigJim's reference to "SSTO" reminded me of a site which may be of interest to those thinking post-Shuttle.www.spacefuture.com/vehicles
Sorry for the digression. Cheers.

newt
2003-Apr-24, 09:49 AM
Darn, that link I gave doesn't work. Try this.www.spacefuture.com/vehicles/vehicles.shtml
Cheers. Newt.

ToSeek
2003-Apr-24, 03:53 PM
No new shuttle flights until 2004, at the earliest (http://www.spacedaily.com/2003/030423195613.0yfra4s9.html)

newt
2003-Apr-24, 11:57 PM
I'm not familiar with the exact method of manufacture of the RCC leading edge segments, whether stranded, particulate, or whatever. Usually the exposed surface is almost entirely the polymer used to set, or bind, the main structural component of the composite(e.g. the strands of fibreglas, Kevlar, carbon, whatever). Polymers can deteriorate due to many things such as UV, single atoms of oxygen (reactively) in Low Earth Orbit, particle impact in orbit (micro-asteroids?), and even by outgassing (molecular evaporation) of the polymer itself.
I suspect any of these may be more likely causes of pitting (sorry, don't see the full penetration of the panel implied by the term "pinholes" as likely) than flakes of zinc oxide and rain water contacting these panels relatively briefly.
To qualify that though, I do recall reading that USAF mechanics working on the SR-71, largely constructed of titanium, could only use titanium tools as steel tools could leave trace amounts that, at the high temperatures reached at high speeds, would react and cause corrosion.
Anyway, for a decent overview of the external materials used on the Shuttle, check here:
www.centennialofflight.gov/essay/Evolution_of_Technology/TPS/Tech41.htm. Cheers.