Kepler Telescope To Send NASA Its Last Images (fortune.com) 27
We don't yet know if there's life on other worlds, however likely that is, but NASA's Kepler Mission satellite has helped pinpoint the abundance of planets orbiting other stars starting in May 2009. So far, it has provided data that scientists have used to confirm the existence of 2,650 exoplanets in a field of over 150,000 stars that it's examining. But that long service is about to end, as NASA said this week the craft is running out of fuel. From a report: The space agency has put the satellite into a form of hibernation until August 2, when there's time booked on the Deep Space Network -- a global array of receivers for space missions -- to download data from its 18th observational mission. Following that download, NASA will use the remaining fuel to start a 19th session. Fortunately, its successor is already in place and operational. The Transiting Exoplanet Survey Satellite (TESS) launched in April 2018, and produced a test image in May. TESS is a massive upgrade, observing almost 400 times the region of space as Kepler, or about 85% of what's observable from its orbit relative to Earth. Kepler is already a survivor, continuing to operate after part of the gyroscope mechanism failed that let it target star fields. Four wheels rotate in the gyroscope to provide a reaction that allows the necessarily precision in tracking, and two of the four failed by May 2013. NASA mission scientists figured out a clever workaround, in which they used pressure from the Sun to provide additional positioning assistance. The mission resumed under the moniker K2 in May 2014.
Theory of Ithaco Reaction Wheel Failures (Score:3, Interesting)
This seems at first blush to be completely nutty, but one new idea behind the high failure rate of the Ithaco reaction wheels (as used on Kepler) is *spacecraft charging*, causing micro-arcs across the steel ball bearings:
http://esmats.eu/esmatspapers/... [esmats.eu]
It explains Kepler, and potentially others, and also why it seems to happen with steel bearing components and not ceramic (since they are nonconductive).
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Until this theory is fully tested in space, perhaps craft should use ceramic bearings. What are their drawbacks?
Re:Theory of Ithaco Reaction Wheel Failures (Score:5, Informative)
It was based on observed failures in space. so there is no question that something is causing that. Bialke's paper goes to some extent to test the hypothesis and to some extent the experimentally verified in ground test in the same conditions used for life testing. They frosted the bearing surface and replicated some of the observed characteristics with as little as *10 volts* across the bearing, as opposed to the likely thousands of volts or more typical of spacecraft charging events
There is no real drawback to ceramic, aside from the fact that they have little flight experience and the one remaining manufacturer Honeywell has only used steel, as far as I know. It may explain the fact that certain batches and individual barrels of grease have been known to produce much longer-lasting gyros, possibly because the conductivity of the grease matters. For the effect to happen, there has to be a thin dielectric layer present. If the grease has a higher conductivity, the charge is never allowed to build up across the interface from ball to race.
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It was aimed using rays, not propelled. A reaction wheel and its spare failed, so they used Mr. Sunshine instead. Not as good as the original, but they were still able to do science.
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You forgot to mention hot grits.
But seriously, Trump is putting the importance of space above the people.
Kepler was $.5B (Score:2)
Then another unit just up that has all of the missions electrical, i.e. batteries, solar panels, and ideally, the main CPUs/storage, etc.
Finally, the rest should be in a unit that is mission specific. It could be communication sats. It could be spy sat. Or in this case
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Someone already thought of that, 60 years ago:
https://en.wikipedia.org/wiki/... [wikipedia.org]
which was used in *exactly* the manner you suggest.
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what science do you consider to be worth spending money on? What is you criteria?
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Unfortunately most projects are funded one at a time for a specific mission. Developing a new overall technology would take some general purpose funding that is very difficult to obtain. Its an issue in a lot of technology driven science and can be quite frustrating .
That said, there is a fair bit of modularity and design re-use in satellites in cases where it makes sense.
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Sad. (Score:2)
Like the Hubble, end of an era, you'll be missed! Thanks for all the wonderful discoveries!
We know who can fix this... (Score:2)