Sign of damage seen in space station solar panel gear

fatal291 · Oct 28, 2007

Story Highlights NEW: Apparent metal shavings found in gears of solar panel joint Astronauts install spacewalk handrails, other equipment on Harmony Tani checks robot arm for sharp edges, which were blamed for tearing gloves European astronauts to visit in December, Japanese astronauts next year HOUSTON, Texas (AP) -- Spacewalking astronauts doing construction work Sunday outside the international space station made a disturbing discovery: what appear to be metal shavings inside a joint that is needed to turn a set of solar power panels. 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. "Wow," said his spacewalking partner, Scott Parazynski. The shavings resembled small flakes and were clinging to the joint as if to a magnet, Tani said. "It looks like a dusty table that you'd want to dust at home," he called down. The astronaut used tape to dab up some of the shavings. It will be returned to Earth aboard Discovery next week for analysis. NASA is uncertain whether the flecks are metallic, possibly from the aluminum foil lining the thermal covers, or some other material. This rotary joint, launched and installed just four months ago, controls the huge solar panel wings on the right side of the space station, to make sure they're facing the sun. The joint for the left solar wings is working fine. The rotary joint will remain in a parked position as much as possible until the problem is solved, said Mike Suffredini, NASA's space station program man

docm · Oct 28, 2007

Probably. Maybe a bad bearing race or ??? All it takes is a little torque in the wrong direction, or an out of spec part. <div class="Discussion_UserSignature"> </div>

3488 · Oct 28, 2007

Hi docm, If its an out of spec part, that's bad design is it not? If the insulation is damaged, could it be due to the extremes of temperature as ISS moves in & out of Earth's shadow, during each orbit, as the gear expands / contracts whilst keeping the Solar Panels orientated? Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

bobblebob · Oct 28, 2007

"the flat surface right below the gear is the race the bearing runs on, it looks kind of mottled and it we would expect it to look shiny" After seeing the EVA highlights, the bit i would be more concerned about would be that. It did look very messy, and not shiny at all. Edit: This could be way off, but if they metal is really the insulation foil, could the mottled effect on the flat surface be through that area not be protected enough due to the damaged insulation?

billslugg · Oct 28, 2007

I see two scenarios. In one, a stray piece of metal got in the bearing and got chopped up and spit out. No further damage will occur. In the other, damage to the rollers and/or race has occurred and it will eventually lock up. To me it is inconceivable that the thing wore out. It turns sooo slowly and it is in a weightless environment. Got to be something jammed in there. <div class="Discussion_UserSignature"> </div>

bobblebob · Oct 28, 2007

"To me it is inconceivable that the thing wore out" The port SARJ which has been operational longer is still working fine, so it must be some foriegn object thats inside there . Also, could something turning so slow actually tear up a peice of metal?

3488 · Oct 28, 2007

Thinking about it, it now does seem more likely to be a foreign object jammed in there. Wonder what it is & why? Andrew Brown. <div class="Discussion_UserSignature"> "I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before". Linda Morabito on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.http://www.launchphotography.com/ http://anthmartian.googlepages.com/thisislandearthhttp://web.me.com/meridianijournal </div>

bobblebob · Oct 28, 2007

The foil insulation seems most likely. Once the sample is back on the ground they will be able to find out very quickly

Testing · Oct 28, 2007

I have not seen the photo's, anyone got a link? I read that it is flakes? As I understand it the bearing cars wrap (clamp) around a semi conical circular track with gear teeth on the inner diameter. I think I saw the bearing cars years ago. Without a picture I cannot be sure. If the debris is evenly distributed across the track-bearing interface and all the way around the diameter, I would say too much surface load (over clamp) or a surface hardening defect? We shall see if my guess is correct. <div class="Discussion_UserSignature"> </div>

erioladastra · Oct 28, 2007

" see two scenarios. In one, a stray piece of metal got in the bearing and got chopped up and spit out. No further damage will occur. " It has been a long term issue so this is very unlikely.

fatal291 · Oct 29, 2007

There are photos on the link

alokmohan · Oct 29, 2007

Can you get it out of danger?

webtaz99 · Oct 29, 2007

F'n golf ball........ (j/k) <div class="Discussion_UserSignature"> </div>

earth_bound_misfit · Oct 29, 2007

Sounds like a job for a can of CRC <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> ----------------------------------------------------------------- Wanna see this site looking like the old SDC uplink?Go here to see how: SDC Eye saver </div>

billslugg · Oct 29, 2007

erioladastra Bill - "I see two scenarios. In one, a stray piece of metal got in the bearing and got chopped up and spit out. No further damage will occur. " erioladastra - It has been a long term issue so this is very unlikely. If a stray piece of metal got in there and disintegrated, it will be spitting out pieces forever. That said, the scenario is unlikely for another reason, a stray piece of metal would not have been disintegrated, it would have jammed the mechanism. I will guess that this bearing is a roller bearing with an inner and an outer race. In that case, there would be a certain clearance between the rollers and the race. Perhaps 2 or 3 thousandths of an inch. In this case it is probably set during manufacture and not adjusted by running the inner race up on a tapered shaft. The driving motor is quite small, being limited by the solar arrays. On earth, a three foot bearing holding a two foot shaft might be transmitting 10,000 or 15,000 HP. Throw a piece of metal in there and voila - chips. Later - complete failure. In space, there might be a 1/4 HP motor driving it. Throw in a chip and it jams. I go with the NASA speculated idea of bits of insulation material - Mylar. <div class="Discussion_UserSignature"> </div>

rocketwatcher2001 · Oct 29, 2007

I don't know the design of this joint and bearing combination, so take what I'm about to say with a grain of salt. I know that some bearings are designed to have a "wear metal", or a softer metal surounding a harder metal. Sleave bearings in a car's engine around the crankshaft are usually this type. They should wear very slowly, unless there are unforeseen stresses on them, then they will wear at a much faster rate. They are very good at handling rotation only, and if any lateral load is put on them, they wear faster. If you open up your oil filter with a special can opener, you will see flakes of metal, which is normal, the flakes are little tiny pieces of wear metal, which is part of the outer sleave, and it's perfectly normal. If a lot of wear metal is in the filter, or you find a chunk of something, you probably have a bearing or a gear going bad. I'm glad that samples are being taken back, engineers can easily find out where the metal came from once they get it in the lab. If a lateral load is put on the shaft, a roller bearing is usually better, and it a thrust load is also on the shaft, a combination of roller bearings at the ends of the shaft with a ball bearing(thrust bearing) in the middle is usually best. Again, I don't know how this thing is designed, but my guess is that if it's wear metal from a sleave bearing, I bet the shaft has been experiencing unforseen lateral loads. If that's the case, then we've just learned something more about big space construction. I'm actually amazed at how well the ISS assembly is going, and my hat is off to the outstanding engineering teams that make it look so easy, even though it's probably one of the most difficult jobs that mankind has ever done. <div class="Discussion_UserSignature"> </div>

usn_skwerl · Oct 29, 2007

<blockquote>In reply to:<hr />Again, I don't know how this thing is designed, but my guess is that if it's wear metal from a sleave bearing, I bet the shaft has been experiencing unforseen lateral loads<hr /></blockquote> Hmm...like atmospheric drag? Would that be a possible source? <div class="Discussion_UserSignature"> </div>

rocketwatcher2001 · Oct 29, 2007

or just more force during attitude control, maybe because of inertia induced wobble. So when the ISS is moved by either it's control gyros, or boosted up, maybe the masts get a unforseen wobble to them, causing flexing and latertal loads that are very small, but very prolonged and take longer to dampen out than expected. Again, I'm just guessing <div class="Discussion_UserSignature"> </div>

CalliArcale · Oct 29, 2007

<blockquote>In reply to:<hr />If its an out of spec part, that's bad design is it not? <hr /></blockquote> No. If a part is out of spec, that means that the design may have been perfectly fine, but the assembly as built does not meet the design. Which means that it should have been caught during testing on the ground. However, I'm personally inclined towards the theory that it's part of the thermal insulation blankets. Sounds like it'll be a real pain to clean out, though. <div class="Discussion_UserSignature"> "People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff." -- The Tenth Doctor, "Blink" </div>

Testing · Oct 29, 2007

It has been reported in the STS-120 thread that the paticles have tested Ferrous. <div class="Discussion_UserSignature"> </div>

Testing · Oct 29, 2007

So SG, a few questions now that I THINK I know what I'm talking about from better than ten years ago. Some you may be able to answer, some will need further inspection. The SARJ is 10.5' diameter "race", or track, with 12 identicle bearing cars, or "trundles" riding on it. The cross section of the race is triangular with a gear toothed flange facing toward the axis of rotation. Each trundle has three pairs of roller bearings in three planes enclosing and in contact with the race faces. There is ferrous debris on the race face as a sample was taken and tested. Either FOD or generated by the rolling elements or the gear elements. FOD would be best case, gear the worst. Spare trundles on board. How many? Samples taken with tape, GREAT MOVE! Any embedded in race or rollers not easily removed? Window in trundle allows line of sight to roller surface. Further inspection. I can't imagine there is a spare race available on orbit. So the issue is if the trundles can be swapped out a few at a time and inspected-cleaned, are there sufficient cleaning materials aboard to wipe down the entire race? I guess we wait for further inspection on EVA-4. Forgot the most important question. When were these trundles launched. Did these go up 7 years ago waiting in orbit for the panels launched in June 07 or did they go up with the panels? Not for SG but general info for the board. The single greatest risk for space flight mechanisms is bearing rolling element contamination or lubricant failure. <div class="Discussion_UserSignature"> </div>

larper · Oct 30, 2007

<blockquote>In reply to:<hr />Not for SG but general info for the board. The single greatest risk for space flight mechanisms is bearing rolling element contamination or lubricant failure. <hr /></blockquote> Huh. Really? And how did you determine this? <div class="Discussion_UserSignature"> Vote Libertarian </div>

MeteorWayne · Oct 30, 2007

I wonder what they mean by "on orbit"? In the ISS or on the Orbiter? They did not make that clear. <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

usn_skwerl · Oct 30, 2007

oooohhhh crap! busted solar array!!! ripped/rough edges on the array!! eeesh! that doesn't look good. hopefully some way to fix it? Edit: It's the B3 right wing. about 1/4 from the top of the wing (11, 12, 13th bays) <div class="Discussion_UserSignature"> </div>

MeteorWayne · Oct 30, 2007

Hopefully, it's just twisted and that's just the sun angle that makes it look so bad... <img src="/images/icons/frown.gif" /> <div class="Discussion_UserSignature"> But the Krell forgot one thing John. Monsters. Monsters from the Id. I really, really, really, really miss the "first unread post" function </div>

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