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Space Station Solar Equipment Showing Damage
bhmit1 writes "The latest space walk has turned up some bad news for the problematic solar panels: metal shavings. From the article: "The rotary joint, 10 feet in diameter, has experienced intermittent vibrations and power spikes for nearly two months. Space station managers were hoping a thermal cover or bolt might be hanging up the mechanism. That would have been relatively easy to fix, so they were disheartened when Daniel Tani radioed down that metal shavings were everywhere. 'It's quite clear that it's metal-to-metal grating or something, and it's widespread,' Tani said.""
Oil does not work in space. It either freezes or evaporates. In fact only some "solid lubricants" like graphite and MoS work to a point.
Baker's Law: Misery no longer loves company. Nowadays it insists on it
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"It's quite another to get the metal on metal thing going and getting stranded in space"
They have spares on board. Excepting the fact that it came as a surprise (a similar setup is ok), this is a non-issue.
In the original scheme of things -- i.e. back in the late 1970s when the Shuttle was being built -- the plan was that while the Shuttle would carry the vast majority of "medium size" payloads, they'd keep Delta around for small payloads (Delta has been upgraded quite a bit since then) and Saturn V around for the large payloads.
Needless to say, that plan was scrapped early on. Probably just before they overhauled the VAB and Pad 39 to make them Shuttle-compatible but Saturn V-incompatible.
-- Alastair
They supplied part of the computer system and the O2 Generator.
The Russians also provide two or three components and a second maneuvering system. They provide the only reliable supply vehicles and as I understand it, there's a considerable part of the orbit that's over Russian space.
In addition, they have never done anything near this big. As it is, the ISS is already double the mass of MIR, and it will go up by 50%. In addition, it is about 50% more living volume than mir and will still double over the next 2 years. This is WELL beyond what russia has done. This is all an new learning experience for the world. Fortunately, this experience will enable us to go to the moon and mars a lot cheaper and faster.Only three times the mass of MIR and you claim it's "WELL" beyond something the Russians have done? Nonsense. As I see it, there are a number of innovations in the structure and construction of the ISS, but the raw size isn't one of them.
Heck, look at China. Their space program is now outspending yearly what Apollo did at its' height. And with that, they launch a fraction of the flights that did and currently do. That is because they are busy trying to acquire the same technology (generally buying it from Russia or simply stealing it from NASA and RSA).
Where does that claim come from? Last I googled, China claims it only spends two billion a year. In comparison, when you adjust for inflation, NASA spending in the 60's peaked above $25 billion in 1996 dollars.These *were* designed to run for many rotations. The design specs for the SARJ (Solar Alpha Rotary Joint) were that the 10.5'x2.5', 2,500lb structure would rotate at 4 degrees per minute without imparting vibration to the laboratories that would mess up the microgravity experiments, for a minimum of 15 years. They also have to transfer 60kW of power at 160V while rotating through a "roll ring". These were the design specs, and they were engineered around that; this break was not supposed to happen. That's why this is considered an anomalous event. It's not a case of an insufficient design goal.
One thing that a lot of people don't realize is that there's still a tremendous amount of stuff that we don't know about living and operating things in space. It's deceptively similar to our world; just picturing it being like an Earth where you can't breathe and you can have enough velocity to fall in a circle simply doesn't cut it.
Example: TSS-1R. Space Shuttle Columbia deployed this as part of NASA's series of experiments with orbital tethers (for "hanging" craft from other craft and for raising and lowering orbits). When the tether was 19.7km out of the desired 20.7km deployed, it snapped. Evidence suggested arcing and burning in the tether. Why? The tether was at -3500VDC compared to the orbiter, with no current flowing through it. A minor defect in the tether's insulation left the conductive core exposed to space. Unexpected trapped gas in the insulation bubbled out in the vaccuum of space. This gas created a path for conduction to the orbiter, creating a plasma arc that burned away at the tether until the remaining strands failed under the strain.
In hindsight, it's easy to look at this and say, "Oh, we should have had a short-detection system." However, hindsight is 20-20. We've learned a great deal from past experiences, which unfortunately means that systems have to get more complicated. For example: where does the heat from running the drive motor for the arrays go? Why, it goes all over the place! It took an entire design study just to figure out where it would be going and what to do with it. Now picture unexpected current draws (creating more heat) from the metal shavings thrown into the mix, and what that will do for heat load, or what the metal shavings themselves could get into or allow to conduct unexpectedly. Things get tricky fast.
Too many people seem too eager to see a "finished product" in space. It's important that things like the ISS be seen foremost as learning experiences. In this case, I'm sure we'll see the same thing.
"We consider that six courts and an asylum claim are a rather odd way of returning to Sweden within a month."
Magnetic bearings have their place but it is not in this sort of application. They excel where the physical contact of normal bearings would cause low lifetime at high speed but in other applications normal bearing are just so much easier to build, use, and replace that their limited lifetimes are not significant.
The space station failure is probably either related to a temperature coefficient mismatch between two parts that are now rubbing or physical damage. A magnetic bearing would not specifically solve either problem.