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Comment Re:Very needed (Score 1) 53

"Vaporizing" satellites doesn't really help you. All you've done is split one big satellite into a whole bunch of tiny satellites, each of which is still moving at orbital velocity (thanks, conservation of momentum..). Except now you have a dispersed debris field moving at orbital velocity instead of a single satellite.

Comment So, a good move then (Score 4, Informative) 288

Monster's general counsel said the move would "significantly disrupt Monster's business and that the two companies had worked well for years, with Monster paying Apple more than $12 million in licensing fees since 2008."

So, this is a philanthropic move from Apple, then. Monster are bottom-feeders that prey on the naive, and the world would be a better place without them.

Comment Re:Satellites (Score 1) 403

Local overheating, hard radiation hits; voltages can actually be pretty high depending on string length and your orbit. Spacecraft experience high differential charging depending on the plasma environment through which they are passing. Outright cell failure is relatively rare though; typical failure mode is degradation below the operable voltage.

Comment Re:Satellites (Score 1) 403

I don't know the underlying physics, but radiation (including solar radiation), especially at high temperature, causes the junctions in the solar cells to become less efficient over time. Less efficient cells generate more heat, which increases the rate of deterioration. Eventually the open-circuit voltage of the cell drops so low that it is below your spacecraft power bus and you stop being able to pull power off the array.

Another failure mode is when individual cells short-out, which happens when the junctions just straight up burn out. This generally results in the loss of individual cells, which lowers the voltage of the array or, depending on architecture, may take down that cell's entire string.

Comment Re:Satellites (Score 2) 403

L1, L2, and L3 are weakly stable; think being at the top of a parabola. It doesn't take much effort to keep yourself there, but you do have to reject orbit perturbations. L4 and L5 on the other hand are actually stable, which is why trojans collect there. Note that there aren't any natural equivalents to trojans at L1, L2, and L3.

Comment Re:Satellites (Score 2) 403

Solar cells will degrade to the point they can't supply keep-alive power to the spacecraft; batteries will degrade to the point they can't sustain the spacecraft through eclipse season; electronics will accumulate more and more total ionizing dose, single event upsets and latchups will become more and more frequent, and things will basically stop working. I don't think anything we've launched will come within an order of magnitude of a millennium.

Comment Re:That would be useless wiring weight (Score 5, Interesting) 403

We don't design LEDs into our own boards, and we explicitly remove them from COTS boards that we use. Generally speaking the diffusers on LEDs outgas, meaning a) they are depositing materials on your spacecraft surfaces (bad) and b) could result in a shorting risk (also bad). There may be space-grade LEDs that big-space (think Hubble, JWST, Voyagers, etc.) use but I would be surprised. There's simply no need.

"Is it plugged in? Is it turned on? Is it on frequency?" solves about 99% of basic device connection issues. An LED will make one very short portion of that slightly shorter, and then only when testing on the bench, since you can't see it as soon as you box it up. As soon as you can talk to a device, you are able to run a long form functional test on it, exercising every part of the design and ensuring everything is working correctly. If it passes, you're good. If it fails, you pull the unit.

For ground support equipment, yeah sure, throw an LED on every rail and switch output.

"Just think, with VLSI we can have 100 ENIACS on a chip!" -- Alan Perlis

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