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Comment: Re:Seriously? (Score 2) 366

by Megane (#49800535) Attached to: Crowdfunded, Solar-powered Spacecraft Goes Silent
They're waiting for reboot because it froze the system completely. TFA says that the manufacturer of their "avionics board" had fixed this bug but it wasn't in the one that went up. So most likely it was a driver bug. A crash or lock-up in kernel space is a lot more problematic than just filling up a filesystem. And apparently they had scheduled an upload of the fix, but the satellite crashed right before the comms window. So now instead of a solar sail, they have a solar brick.

Comment: Re:Simple.... (Score 1) 366

by Megane (#49800319) Attached to: Crowdfunded, Solar-powered Spacecraft Goes Silent
Oh, but that's the best part. There apparently is a watchdog, but it only trips after four or five weeks by (presumably unchanged) default, and it's completely independent (rather than being reset regularly by a signal from a properly-operating system). This for a mission that wasn't even supposed to last two weeks. The good news is that the orbit could last for as long as six months with the sail un-deployed.

Comment: Re:CSV (Score 4, Interesting) 366

by Megane (#49798923) Attached to: Crowdfunded, Solar-powered Spacecraft Goes Silent

To be fair, that was copypasta from TFA. And they carefully omitted the next sentence: "The manufacturer of the avionics board corrected this glitch in later software revisions. But alas, LightSail’s software version doesn’t include the update."

That still doesn't excuse a problem that would have been found by bench-testing the thing for a few days before sending it up. Nor does it excuse constantly appending one file to store data in an unattended system. Also, anything that JPL sends up has a backup channel that can push that little red button on the main computer. All they can do now is hope for cosmic rays to reboot it randomly. At least it's in LEO and not zipping off into interplanetary space.

In the meantime, the team is looking at several fixes to work around the software vulnerability once contact is reestablished. One is a Linux file redirect that would send the contents of the troublesome beacon.csv file to a null location, a sort-of software black hole. Lab testing on this fix has been promising—over a gigabyte of beacon packets have already been sent into nothingness without a system freeze.

Well, isn't that special. Now they test it. So if they can just link it to /dev/null, did they really even need that data? It's always fun to cause a mission to fail by recording data that wasn't even needed.

Comment: Re:A lot of inertia (Score 1) 586

by Megane (#49791797) Attached to: How Tesla Batteries Will Force Home Wiring To Go Low Voltage
Why are you fixated on 12VDC? The only thing special about 12V is 6-cell lead-acid automotive batteries. Data centers use 48VDC, which gives 4 times the wattage over 12VDC (though still less than half of 120VAC), while not needing heavy-duty switches because of arcing. (120VDC is scary with a big knife switch where you can see the arc)

Comment: Re:High Voltage DC more likely (Score 2) 586

by Megane (#49791731) Attached to: How Tesla Batteries Will Force Home Wiring To Go Low Voltage
I recommend you go to Youtube and look for videos showing 110 volts AC vs DC with a knife switch to see the important difference. Hint: "zero crossing". You can't just splice your whole house into the same voltage of DC expect anything to work the same. Sure, your incandescent lights would work, but the wall switch wouldn't be able to turn it off, and might even start a fire from the arc. There's a reason that data centers use 48VDC and no higher.

Comment: Re:AC is the standard (Score 1) 586

by Megane (#49791631) Attached to: How Tesla Batteries Will Force Home Wiring To Go Low Voltage

Except that those weren't built into every wall of a house, and so were easy to replace. Good luck trying to rewire your house for anything that requires a larger gauge of wire or extra wires, if the wires are all behind sheetrock and run through studs on a slab house with no basement. And you'll also have to change all your plug outlets, because no electrical code is going to allow a completely different standard to use the same plug.

Sure, things change, but some things also don't change. The compact disc (both audio and data) is still with us, over 30 years later. Despite Blu-Ray, DVD is in no danger of dying off. Whatever new electrical standard you think could possibly happen would need to have good enough reasons to justify the time and expense of rewiring. Knob-and-tube wiring went away because of safety (no ground, fire hazard, you may not even be able to get insurance), and it was cheaper to install cables than to nail up a bunch of knobs.

If it wasn't for Newton, we wouldn't have to eat bruised apples.

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