Space Station Gyro Problem Dangerous?

mysterystevenson writes "After bringing more mass than ever before up to the ISS, one of the gyros has failed. Gyros help maintain attitude position in space; the more mass needed to be controlled, the more force that is exerted on the gyros. Now there is the danger that the Shuttle may be bringing yet more mass and starting construction while turning off another gyro, which could cause a need for thrusters to maintain attitude. The assemblies are not all constructed to be able to withstand such force and in a bad situation there could be a collapse which could affect the Shuttle and the ISS as well. Worse case could be total loss; a wise idea might be to alter the construction schedule and address the Gyro and Gyro design problems, before going forward with the introduction of more mass."

Comments

Solar arrays can't handle rocket fires???

[SirLoadALot]

Okay, who thought it was a good idea to put solar arrays so fragile that they can't withstand small rockets firing on a station that is equipped with those rockets? Ideally, they would just add another gyro to the December mission (which I imagine would cause the mission to be delayed for training at this late date), but apparently they don't currently have a spare. One of these gyros failed previously and the spare was installed. So someone felt that with FOUR of these gyros on the station, it was okay to have only ONE spare? Most of my customers would not accept that sparing ratio, and IANARS! I guess the best case scenario is that perhaps they can change the manner in which they plan to rewire the station to avoid taking 2 out of the 3 working gyros offline at the same time. This brings up training and procedure issues again, of course -- it takes time and practice and well-written, simulation-testing procedures to get people to do complicated jobs like this correctly, the first time. If I reverse the order of two ethernet plugs, or two variables in my code, I might need some time to find the problem later, but no one is going to be electrocuted, and no rockets will fire. :-)

Re:Solar arrays can't handle rocket fires???

[delta407]

Okay, who thought it was a good idea to put solar arrays so fragile that they can't withstand small rockets firing on a station that is equipped with those rockets?

Don't believe everything you hear on Slashdot.

ISS is not in imminent danger. First off, it can hold attitude indefinitely on two of four gyros. Second, the solar arrays can withstand the RCS thrusters firing, they just need to lock down the assemblies that rotate the solar arrays first. Therein lies the rub.

The next shuttle mission brings up more parts and re-wires a large section of the ISS's power grid. This means bringing some systems offline for the duration of a spacewalk, reconfiguring them, and bringing them back up shortly thereafter. Naturally, during this process, the ISS will be running on less redundancy than it is now. One of the spacewalks is slated to bring down two of the gyros, on the assumption that the other two can maintain attitude, while running off the new solar arrays which must rotate in order to generate the specified amount of power. Without the other gyro, RCS firings might be necessary, which make the solar cells unhappy.

This is a nontrivial but solvable problem. Solutions currently being proposed:

• Bring up the failing gyro for the duration of the spacewalk. It didn't up and die one day -- it's just vibrating a lot, and might do the trick.
• Leave the failing gyro off, and be prepared to bring it up only if the one operational gyro can't maintain attitude.
• Lock the solar array into a suboptimal orientation, and fire the RCS thrusters as necessary.
• Bring up a replacement gyro. They're about 800 pounds and aren't simple to install, which is a lot to be adding to a mission three weeks from launch, so this is unlikely.

They are rocket scientists, you know.

Re:No spares for the RAIG array?

[Jarjarthejedi]

A while ago popular science ran an article on the ISS. From what I remember (and my memory is far from perfect) the ISS has 3 gyros and originally had 3 spares. Over time the spares have been swapped in for busted originals so now there are no spares left. I'm 90% sure that's why they don't have any spares left, though my numbers may be off, they used em up and never replaced them.