The Kepler mission has lost its second gyroscope, ending the ability of the telescope to aim precisely.
The Kepler mission has lost its second gyroscope, ending the ability of the telescope to aim precisely. More details here.
The telescope’s primary mission, to stare continuously at one section of sky, looking for exoplanet transits, is over, though it might still be re-purposed for other astronomical research.
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"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
The Kepler mission has lost its second gyroscope, ending the ability of the telescope to aim precisely. More details here.
The telescope’s primary mission, to stare continuously at one section of sky, looking for exoplanet transits, is over, though it might still be re-purposed for other astronomical research.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
I’d like to know why they only put a single gyroscope in that machine, given that it’s in an orbit that doesn’t allow servicing. Hubble started off with 6 gyros, and 8 to 10 gyros were replaced with service missions. Did they think that they had reasons to believe that Kepler’s gyros were significantly more reliable?
The spacecraft had 4 reaction wheels to begin with, not one. One failed about a year ago. The second started going bad this year.
Gyros have been a chronic problem, as they are a moving part that moves a lot. They had no reason to think these gyros were more reliable than previous ones, though the technology has improved. The simple fact is that Kepler was designed for a three year mission, which it survived to complete. You want to guarantee a longer mission you have to spend more, and the money is not always there for such things.
First of all, I was under the impression these items were reaction wheels, not gyros. I hope to heck modern spacecraft are designed with something better than spinning mass for gyroscopic reference. Fiber optic ring laser gyros aren’t exactly bleeding-edge technology anymore.
I’m unacquainted with the details of spacecraft engineering, but if friction was an issue, it seems that the reaction wheel design must feature close-tolerance physical bearings of some kind that presumably require lubrication to function. This implies that the wheels operate in a sealed pressurized box of some kind, else the lubricant would evaporate or otherwise disperse. I should think that in zero-G, this would even be true of solid lubes like molybdenum disulfide, but maybe there’s some ultra-low vapor pressure lube with a high surface tension that will stay put in zero-G and very low ambient pressure. Regardless, if it’s the case that the reaction wheels just don’t last beyond a certain point – plus or minus – once they’re in space, then adding extras to the design won’t really buy you anything useful in the way of extra reliability or vehicle service life. If they only deteriorate when running then it would make sense to design in some dormant stand-bys that can be called on, incrementally, to replace units that fail in service. But the most sensible thing to do, it seems to me, is to design reaction wheels with non-contact magnetic bearings designed to operate in the ambient hard vacuum of deep space. Perhaps there are engineering considerations of which I am unaware that render this idea a non-starter for energy-use or cost reasons, but I would require a fair amount of convincing on this point.
My uneducated guess might be that magnetic bearings would create a small generator effect and thus cause some power problems like an excess static charge would.
The extra magnets could be a weight problem(?).
Any magnetic system used to spin up the gyroscope might interfere with the sensors controlling them or reading them.
You would think though that if they could get an aircraft gyroscope to work for 10 years plus they could get one in space to work a bit longer than three years.
Or just add more backups.
Has anybody ever tried using a superconductor bearing? I would think achieving the required low temperature wouldn’t be much of a problem in space?
Thanks. I mistyped, and I meant to ask why they only put one SPARE gyro in the satellite. With Hubble, a gryo died roughly every two years.
You would need a continuous supply of liquid helium(I think) to keep the superconductor cool.
And in the end it would just be a magnet and you would get all the same magnet problems you would get from regular magnets spinning next to each other.