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Comment Re:There is no way NASA mixed the measurement syst (Score 1) 244

As others have pointed out below, while it it true there was a units mix-up, this error wasn't caught due to other, more wide ranging problems. IEEE did a great writeup of this a while back (article link - didn't link to IEEE directly since you probably have to be a member to see the article). Very interesting reading. In summary...

First the spacecraft was asymmetric, causing some issues with the stabilizing flywheels and the onboard thrusters (used for major course corrections). Second, the person doing the calculations for the major course corrections noticed that the burn time (calculated using the bad units) didn't look right compared with previous missions. However, his management made him prove that the calculations were wrong, instead of proving they were right (presumably knowing that they would be different, given the first point about the asymmetries). He didn't catch the units error, and since he couldn't prove they were wrong they went along as if nothing happened. The article was really pointing out that while this was a technical error, the more fundamental issue was a management and culture issue. To me this made for an interesting case study in how to handle unknowns in a mission critical system - assuming things are wrong until proven otherwise, not vice versa.

(I don't seem to have the Spectrum issue with me, but I seem to remember it had some other articles about related management/culture failures).

"Tube Map" Created For the Milky Way 142

astroengine writes "Assuming you had an interstellar spaceship, how would you navigate around the galaxy? For starters, you'd probably need a map. But there's billions of stars out there — how complex would that map need to be? Actually, Samuel Arbesman, a research fellow from Harvard, has come up with a fun solution. He created the 'Milky Way Transit Authority (MWTA),' a simple transit system in the style of the iconic London Underground 'Tube Map.' (Travel Tip: Don't spend too much time loitering around the station at Carina, there's some demolition work underway.)"

Comment Re:Yeah, but it is reliable. (Score 1) 245

At the risk of being pedantic and not really contributing to an older thread (hey, it's slashdot, right?), radar originally/typically measures range - that's what the last 'R' stands for (RAdio Detection And Ranging). True, that's evolved to where some modern radars use Doppler for things, but ranging is it's bread and butter.

That being said, I think I agree here - vehicle speed measurements seem like an odd application of LIDAR, given the wavelengths. I haven't worked out the math, but I given the distances/velocities we're talking about here I'd be interested to see how speed error is impacted by pointing "jitter" (that is, the beam moving around b/c a human is pointing the beam at a moving target that has many features that are large compared to the laser's wavelength). It would be even more interesting to compare that against that radar errors, especially when on considers that the radar might have problems localizing the speed when vehicles are close (as others have pointed out). One would think someone did tests like these once upon a time, but.....

Perhaps I should rush to patent a combo device that uses both technologies, claiming that the two pieces of evidence together overcome their individual weaknesses. Apparently you don't even need proof that it works!

Comment Re:back in my day (Score 1) 785

While in general you are right, fire departments are quite concerned about how well their radios work (a friend is a firefighter, and they go on test runs of large industrial buildings in their area to make sure they can communicate), in this case I'm not sure it matters.

I believe the passive systems the OP was referring to use their own, local "cell tower", to which all nearby phones try to communicate (since this tower is the closest, by rule that's the one the phones will try to talk to). If this tower isn't connected to the outside world, though, no calls/texts get through. All other RF comms, however, provided they aren't using the cell network, will operate just as they normally would. As someone else suggested, I think there were even provisions to allow emergency calls only pass through.

I'm too lazy to search, but I think there was a slashdot story about French theaters doing something similar. Someone more bored than I am will get some mod points if they can find it.

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