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International Space Station Gyroscope Fails
b00m3rang writes "Reuters reports that one of the three working gyroscopes that keep the international space station stable and in the right position stopped working, just hours after a new two-man crew moved in for a half-year stay."
The article clearly states that ONE of three failed. The story posted makes it sound like the ISS is now starting to spin out of control.
That would be Hi-La-Ri-Ous if they had actually gone up in the Shuttle. They actually went up in a Soyuz capsule.
Now it is up to 2 of 4... http://www.sltrib.com/2004/Apr/04232004/nation_w/1 59922.asp
I wonder why they would place the circuit breakers outside the space station
I think the larger question is why they didn't engineer the breakers so they could be reset with servos or other electromechanical means.
Still, I wonder why the circuit breaker is not in a place easy to get to
Space is a difficult enviroment to engineer for. They probably put the circuit breakers outside thinking that they would rarely need to be used, if at all. By placing them outside they made more space inside the station.
I wonder if they have a special escape pod attached to the space station
There is actually a Soyuz spacecraft attached to the station to act as a kind of lifeboat if need be.
Remember in the original Star Trek on how Scotty never had enough dilithium crystals? I always thought that was kind of funny that they couldn't find a way to stash a couple of extra boxes of crystals somewhere.
It seems to be that way with NASA and gyros.
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It seems that over history, the spacefaring versions of our technology are quite inferior to what we have planet-side. On typical space vehicles, this is because the vehicles were built so long ago. The ISS is a relatively new invention, and the number of bangs, bumps and hiccups seems to be more or less consistant with it's much older counterparts.
I think you misunderstand the problem. Engineering gadgets here on earth is simple compared to engineering gadgets to be deployed in space. We've lived in the relatively friendly environment of the earth for our entire racial life. Space is a hostile environment which we have only been exploring in a limited fashion in the last fifty years or so.
Compare the space shuttles to your car. Sure, they probably cost more in maintenance than your car, but they were engineered in the 70s, and with a couple of exceptions, they're still operational. I'll be the ISS has been in continuous operation for longer than any gadget in your house.
Anyway, the first problem is that they have to engineer devices that are capable of withstanding the amount of thrust they'll be under just to be launched out of the atmosphere. Second problem is that these same devices have to survive in vacuum, and in atmosphere (they're built down here). Third problem is they have to last for a long time, because solving the first two problems is so expensive that building replacements is very cost prohibitive. Fourth problem is that they're built by the lowest bidder, and frequently also engineered by the lowest bidder. :)
It's too easy to point at something in space and compare it's performance to any given gadget you own. Now try strapping that gadget to a rocket and launching it into orbit, and if it survives, then you can make your comparison.
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Ever tried to twist a gyroscope? You can use them in two ways: if you don't try to push them, they stay oriented the same way so yo have a directional reference. But if you ty to move, they "push" back. This gives you something to "push against" in order to twist yourself in space. You don't need to spend expensive reaction mass hauled up from earth, you just use electricity from your solar cells, and you get a much smoother and more accurate control than thrusters.
However, a single gyro can only handle positioning about two axes - you can rotate it about its spin axus as much as you like. So for three axis rotational stabilisation you need at least two gyros at 90 degrees to each other.
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If you're wondering how a gyroscope works and what it does:
How stuff works has a nice article.
Nasa's also got a page about how they're used in space shuttles
The pods have a shelf-life. The one thats been there already is going back down with the old crew - the reason they can't have more than two is that they have to stagger the operational lifetime of the pods, since after 6 months in space (or some such thing) its no longer 'safe' ...
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Compare the space shuttles to your car. Sure, they probably cost more in maintenance than your car, but they were engineered in the 70s, and with a couple of exceptions, they're still operational.
I'd just like to point out that those "couple of exceptions" are actually 40% of the fleet, and that their removal from service resulted in the sudden and violent death of everybody inside.
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Remember theres (practically) no friction in space - a small amount of energy can accellerate a massive object (very slowly). I'd guess that the amount of accelleration needed to keep an orbiting body stable is pretty low. Of course if there was a metior strike, etc then it would probably send the station into a spin, but in that case (if there's enough of the station left) you would fire up the thrusters to provide a much bigger accelleration.
Although I'd be quite interested to know how massive the gyros are and how fast they spin. Also, how quickly can they spin up a gyro from stationary - I'd expect they have to do this quite slowly since the torque of spinning up a reasonably massive gyro would have some effect on the spin of the station.
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but needs to be recalibrated, as Andre Kuipers (ESA) stated on an interview this morning with Dutch television (Dutch language).
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Because you don't "just do" an EVA. Putting on a suit and going outside the station requires a lot of planning. You have to have the right time of the crew's daily cycle. You have to have the right ground personnel available to support the EVA. You have to schedule it for a time when you have sufficient TDRS (ground relay satellite) time available to cover the entire EVA. You maybe have to find a time when the station will be in the right attitude with respect to the Sun for the right amount of time, due to heating/cooling issues with the suit and perhaps (?) lighting issues with the area to be serviced. (And if the station has to be oriented a certain way, that might affect the amount of time the downlink antennas can be pointed in the general direction of the TDRS satellite.) Most importantly, the ground controllers have to draw up a complete step-by-step plan of the EVA, and the crew has to have time to study it. Take all that into account, and add the fact that the crew's every minute is planned days or
weeks in advance, and you can see how it just takes some time to put together everything it takes to do an EVA. Going outside the vehicle is a risky activity. Extreme care is taken in its planning and execution, and rightly so.
In a life-threatening emergency, like a sudden rapid depressurization, the plan probably calls for the crew to board the "rescue vehicle" (a Soyuz that stays docked at the station), undock, and deorbit.
(Disclaimer: I don't work in the ISS program, but I have a general - read: vague - idea of how EVA works in the shuttle program. Consider the above to be an educated guess - but correct in spirit.)
They will resume thruster orientation maintained by the Russian modules. the Zarya Control module (Formerly the FGB Tug), and the Zvezda Service Module which is how the altitude and orientation were maintained until the Gyroscopes were installed as a part of the Z1 Truss.
Zarya was launched in November 1998.
Unity was attached by Shuttle Endeavour in December 1998.
Zvedza docked to the fledgling station on July 25th, 2000.
The Z1 Truss was installed by Shuttle Discovery in October, 2000.
The Control Moment Gyroscopes which are an integral part of the Z1 Truss, weren't activated until Assembly Mission 5A in February 2001.
Yes, this is a big deal, it will not however, result in the station tumbling out of control and dooming it forever.
I wonder why they would place the circuit breakers outside the space
station.
Well, there are only so many places inside where you can put stuff. Something has to go outside, so you put the stuff out there that should rarely, if ever, need servicing. The stuff that needs more frequent access goes inside. Circuit breakers are (speculating here) relatively simple, well-understood technology that you don't expect to have to replace. They should "just work".
If those ciruit breakers are like anything in my house, they
go out all the time.
Note that they're not going out to reset the breaker, but to replace it. The breaker can be monitored and reset remotely. In fact, the breaker was reset yesterday - probably from the ground - but it tripped open again. I believe the working theory is that the gyro's OK, but that the breaker is bad - tripping when it shouldn't. If this is true, then replacing the breaker will recover the gyro without having to replace it (a much more difficult affair).
However, that is not the type of gyroscope that has failed here! In the last couple decades, gyroscopes have been used as actuators to actually provide the TORQUES necessary to MANEUVER space vehicles. This is very different from the much more common use of gyros simply to determine attitude. In fact, these gyroscopes are more correctly referred to as Control Moment Gyrospcopes or CMGs. (Incidently, they come in two flavors, single and dual gimbaled - with the ISS using the much less common and more complex [read prone to failure] dual gimbaled CMGs (DGCMG)).
A CMG works as a torque amplifier. You essentially spin up the inner element to a high rpm (usually 3000-5000 rpm) and then apply a small torque to the outer gimbal. The the gyroscopic rigidity of the inner rotating element resists this torque and the result is a much-amplified reaction torque imparted on the vehicle.
Traditionally, three-axis stabilized spacecraft that require fine pointing control have used reaction wheels or momentum wheels for control. CMGs allow for orders of more magnitude of more torque (for an equivalent mass alternative) and more momentum storage (unfortunately, momentum is conserved even in space, so if you impart an angular rate to a spacecraft, you must have some element inside the spacecraft to 'store' an equal an opposite momentum - this is what actually limits a spacecraft's slew rate). The downside of CMGs is that they are mechanically complex (don't even get me talking about null-spaces) and that high rpm inner element must be lubricated extremely well if you want the vehicle to perform for years without an oil change (as those are hard to come by in LEO); thus they tend to higher failure rates. The solution to this has tended to be to add redundant CMGs (which is probably still a better option than using less capable alternatives.)
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If it was an imminent emergency, how short a time before they could get out there? Minetes, hours, days?
I asked a coworker who's a former Station flight controller and got you a better answer to this question. It would take hours at least. If the crew were to just don their suits and go outside the station, they would very quickly get extremely ill.
The reason is that the suits they use for EVA are pressurized at only 3-4 PSI, whereas the pressure in the ISS is maintained at 14.7 PSI. With the sudden drop in pressure, the crew would get decompression sickness - "the bends". The usual EVA procedure is for the crew member who's going out to breathe pure oxygen for several hours before the EVA. This flushes the nitrogen from their bloodstream and tissues and prevents decompression sickness.
The gyroscope that failed isn't used to measure orientation in space, but rather, to CONTROL orientation in space. You ever played around with a gyroscope, or a bicycle wheel on an axis, or anything? When you spin it up it resists movement along certain axes in relation to its own axis of rotation. It "pushes back". The gyros being used on the ISS are big massive suckers that are used to control the ISS's position in space, not to simply measure it. Fiber optic gyros would thus not suffice for this purpose.
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