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Clinically Insane
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Just like on reddit, except ours won't suck.
TIL modern, consumer GPS chips are constantly analyzing their own telemetry data. If they realize "I'm flying in a missile", they deactivate themselves.
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Last edited by subego; Dec 31, 2014 at 05:54 AM.
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It's more "I'm going way too fast for what I was designed for," but yes, those chips do a lot more than just some math.
The basic location algorithms are pretty straightforward matrix algebra; you get data from at least 4 satellites and throw it into a system of (at least) 4 equations in 4 variables and just crank through. It's not 3rd grade arithmetic, but it's doable on paper. So with processor density going up all the time, a reasonable sized GPS chip can do a lot more than matrix algebra. The hardest thing for a GPS receiver to do, actually, is to find and lock onto the signals, since they are intentionally "in the grass" of the background radio noise - the system picks out the frequency hopping signal by knowing where each satellite's signal is supposed to be.
My contribution: (yesterday) I learned that people who work for AT&T don't like AT&T's call center decisions. Nobody like off-shore call centers, but when a face-to-face customer service rep tells you that they have "problems" working with call center people, it kind of means that those call centers aren't terribly effective... (Lame, I know, but it's all I've got right now.)
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That LinkedIn is a very valuable tool in determining who you DON'T want to hire.
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Originally Posted by subego
TIL modern, consumer GPS chips are constantly analyzing their own telemetry data. If they realize "I'm flying in a missile", they deactivate themselves.
Really? Is that kind of like scanners that throw up errors if you try to scan currency?
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AT&T iPhone 5S and 6; 13" MBP; MDD G4.
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Unfortunately, while I assumed it was intentional, and would thus be just like the scanners, Glenn makes a great point it may just be a beneficial side effect of throwing it new data faster than it can handle.
In the "beneficial side effect" department, not sure it's true but I understand the military did studies on making engines on combat planes quieter. Turns out, they can make them a lot quieter without a huge impact on performance, but it provides little to no tactical benefit, and loud planes actually serve to scare the shit out of the enemy.
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The GPS thing sounds like a rumor. I suspect a consumer GPS system assumes reasonable altitudes and speeds, and simplifies the equations for faster/more accurate solutions. Altitudes outside the atmosphere are unrealistic, as are very high speeds.
For example, suppose you're in orbit above the GPS satellites. It's possible to convert that into a location, altitude, and speed. But some of the calculation numbers will become negative, since you're on the opposite side of the GPS satellite "shell". If the consumer GPS device is actually a CPU with the full equations, it could solve it. If it's a purpose-built chip, or simplified software, it's going to have a nervous breakdown.
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Would you even be able to receive a signal from above a satellite?
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Chris Farley was the original voice of Shrek.
How did I not know that after all of these years?
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Originally Posted by subego
Just like on reddit, except ours won't suck.
TIL modern, consumer GPS chips are constantly analyzing their own telemetry data. If they realize "I'm flying in a missile", they deactivate themselves.
I used my iPhone GPS on an airplane above 30000 feet w/o problems.
Sure, speed is not missle speed, but still.
-t
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It sounds like a rumour, but I remember a rumour years ago that Saddam Hussein tried to get around a ban on shipping computers to Iraq by ordering a load of Playstation 2s so he could install Linux and use them to design missiles. If that was true then building in safety protocols to stop the wrong people from building missile guidance systems out of cheap consumer gear seems like a reasonable idea. The US military hobbled the accuracy on consumer GPS so why not? Maybe thats another rumour.
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I have plenty of more important things to do, if only I could bring myself to do them....
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Originally Posted by Waragainstsleep
It sounds like a rumour, but I remember a rumour years ago that Saddam Hussein tried to get around a ban on shipping computers to Iraq by ordering a load of Playstation 2s so he could install Linux and use them to design missiles. If that was true then building in safety protocols to stop the wrong people from building missile guidance systems out of cheap consumer gear seems like a reasonable idea. The US military hobbled the accuracy on consumer GPS so why not? Maybe thats another rumour.
Even the US Air Force uses Playstations to build computer clusters : US Air Force connects 1,760 PlayStation 3's to build supercomputer
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Originally Posted by turtle777
I used my iPhone GPS on an airplane above 30000 feet w/o problems.
Sure, speed is not missle speed, but still.
-t
Or missile altitude.
It's almost like you're saying if you don't go as fast or as high as a missile, your GPS won't think you're a missile.
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Clinically Insane
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Originally Posted by Waragainstsleep
It sounds like a rumour, but I remember a rumour years ago that Saddam Hussein tried to get around a ban on shipping computers to Iraq by ordering a load of Playstation 2s so he could install Linux and use them to design missiles. If that was true then building in safety protocols to stop the wrong people from building missile guidance systems out of cheap consumer gear seems like a reasonable idea. The US military hobbled the accuracy on consumer GPS so why not? Maybe thats another rumour.
The accuracy hobbling is legit AFAIK, however it never seemed a big enough hobble to be of consequence.
The PlayStation story sounded bogus to me. Easier to buy a guidance system off the Russians...
Then I remembered the story Soviet fighter pilots used to import radar detectors (like for your car) because they more reliably informed you of a radar lock than the built in model.
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And while we're at it:
Bat bomb - Wikipedia, the free encyclopedia
"The bomb consisted of a bomb-shaped casing with numerous compartments, each containing a Mexican Free-tailed Bat with a small timed incendiary bomb attached."
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My daughter knows the word "shit" (too much time spent at the garage).
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"I have a dream, that my four little children will one day live in a
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but by the content of their character." - M.L.King Jr
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IIRC, it was part of the license required to get access to GPS signals - that the chip would disable itself if the altitude was over 70'000 feet or the speed was over some number, to avoid it being used to target missiles or military jets. There was also the scrambling, that the time signal from the satellites was off by a small amount and the correction was sent out encrypted. The scrambling was disabled by executive order back in the Clinton era, but it just meant setting the correction to zero - it can be turned on again if required.
I heard about these two together, and since the scrambling thing was confirmed true, I assumed they both were. May have been a bad assumption on my part.
EDIT: Wikipedia confirms this, although they put the ceiling at 60'000 feet. It appears that a receiver which does not disable itself at these speeds requires an export license to be sold outside the US, which means that it is easier to just implement that feature in all civilian devices and avoid the hassle.
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The new Mac Pro has up to 30 MB of cache inside the processor itself. That's more than the HD in my first Mac. Somehow I'm still running out of space.
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It is possible to use GPS from orbit - the ISS does. But the equipment they use has to be programmed to accept data that won't make sense to a basic GPS system. Velocity is WAY too fast for the processing speed in "affordable" GPS devices (the data does change too quickly for cheaper stuff to handle), and altitude won't make sense at all - the GPS satellites are at about 11,000 miles in altitude (half-synchronous orbits), so the ISS is below them, but the altitude axis answer is going to be outside expected values, so error checking routines in terrestrial and even aviation devices.
Early ground-based GPS devices could only get full solutions (location, altitude and direction) if moving at least 3-4 MPH, because they needed a change in location to calculate direction. If you stopped, the heading readout just went blank. Modern devices incorporate solid state magnetic compasses, so they give you more than just what GPS says.
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Way below. Only 250 miles, give or take.
It's like a trip to Dallas.
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Originally Posted by Cap'n Tightpants
My daughter knows the word "shit" (too much time spent at the garage).
Mine consistently asks for "glass of wine". Had to have a talk with his mother.
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Originally Posted by Laminar
Mine consistently asks for "glass of wine". Had to have a talk with his mother.
Could be worse, could be saying "Shit, go out the back, Laminar is home early!"
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Mankind's only chance is to harness the power of stupid.
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"Papa, I have to poop."
"Right now?" (jokingly)
"You have 5 minutes."
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"I have a dream, that my four little children will one day live in a
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but by the content of their character." - M.L.King Jr
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Today I learned when planning how to armor bombers, the original idea was to put it where bombers ended up with the most bullet holes.
One of the mathematicians on the project (Abraham Wald) pointed out that was ass-backwards. Where the bullet holes end up is where the plane doesn't need armor. Where there are no bullet holes is where you armor, because planes which get shot there don't come back for analysis.
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Originally Posted by subego
Today I learned when planning how to armor bombers, the original idea was to put it where bombers ended up with the most bullet holes.
One of the mathematicians on the project (Abraham Wald) pointed out that was ass-backwards. Where the bullet holes end up is where the plane doesn't need armor. Where there are no bullet holes is where you armor, because planes which get shot there don't come back for analysis.
The bombardier doesn't agree.
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That must have been a rather large caliber bullet.
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That B-17 wasn't "shot up," it was "run into" by another aircraft - probably part of a German fighter that the chin gunner shot up. The chin gunner was in the nose all the time, while the bombardier was only there during the actual bomb run; the gunner probably didn't survive that impact. My bad. It was flack damage over Cologne that destroyed the nose of that plane.
Yes, sometimes it helps to say out loud what you're thinking about. Some airplanes were designed to survive that sort of abuse and come home, such as the A-10. Because of experience with the B-17 and other aircraft in WWII, aerospace engineers knew what parts needed extra support, what parts needed armor, and what parts needed redundancy. The A-10 can survive losing one engine, half the tail, the outboard third of BOTH wings and everything forward of the cockpit and still fly hundreds of miles to get home.
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The tail also obstructs the view of the engine exhaust from below to help against stinger type missiles.
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Clinically Insane
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Originally Posted by ghporter
That B-17 wasn't "shot up," it was "run into" by another aircraft - probably part of a German fighter that the chin gunner shot up. The chin gunner was in the nose all the time, while the bombardier was only there during the actual bomb run; the gunner probably didn't survive that impact. My bad. It was flack damage over Cologne that destroyed the nose of that plane.
I was thinking either collision with another plane, or direct hit from an airburst.
It looks so clean, something non-explosive seemed reasonable.
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Clinically Insane
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Originally Posted by ghporter
Yes, sometimes it helps to say out loud what you're thinking about. Some airplanes were designed to survive that sort of abuse and come home, such as the A-10. Because of experience with the B-17 and other aircraft in WWII, aerospace engineers knew what parts needed extra support, what parts needed armor, and what parts needed redundancy. The A-10 can survive losing one engine, half the tail, the outboard third of BOTH wings and everything forward of the cockpit and still fly hundreds of miles to get home.
Wait... you're an Air Force guy. Aren't you supposed to be selling us on the JSF? No A-10 talk allowed!
[AF equivalent of "drop and gimme 50" goes here]
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Today I Leaned my dad, who I just told the Wald story to, happened to have had lunch with the guy's son about a month ago.
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Nah, the JSF is some brass' idea of cool. It's made of vapor and Major Military Contractor, not like a real plane.
I once saw a Fairchild factory pilot demonstrate the A-10 to a bunch of Tactical Air Command brass. They delivered them to Bergstrom AFB, where I was stationed at the time, so we were familiar with the plane showing up on a fairly regular basis. But then the factory pilot did the ENTIRE Thunderbirds airshow routine for us. Instead of flying out 5 miles to turn, he did everything over the airfield. All of it. In the inverted pass, the A-10 was literally flying level while inverted; the F-16 cannot do that, and has to have the nose pointed away from the ground for an inverted run. It was awesome.
Later, while stationed in Panama in 1987-89, (while ol' Manuel Noriega was going from being a pain to being a global drug threat), the US Coronet Cove fighter deployment was changed because of work on the runway at Howard AFB. The work was to improve the ends of the runways, so of course that meant there was less runway usable at the time. They couldn't fly A-7s there due to the shorter runway, so they brought in A-10s. They are quiet... so quiet that they were able to buzz Noriega's goons in a number of locations - sneak up on a clandestine pro-drug operation with an airplane that can shoot the living #$%^ out of a main battle tank and see what kind of hijinks ensue! And of course the laundry issues that come with it.
What can JSF do? Cost us enough per airplane to put a whole town through graduate school, and still not fly as well as an F-4 from the 1960s, that's what. If they get it to actually fly...
But no, I don't have any real opinions about it...
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A few years back there was an A-10 that would fly over my grandparents vacation home on Lake George. There's basically hills along both sides of the trip of the lake. It was interesting till I realized he was about 500ft off the ground at all times. He was actually practicing popping over the hill, lining up to strafe the boats, then darting back over the hills.
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The New York ANG used to fly A-10s out of Hancock Field near Syracuse. I'm not sure who's flying them now, as the Brass has decided that the most survivable attack aircraft in history needs to retire.
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Glenn -----OTR/L, MOT, Tx
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Originally Posted by BLAZE_MkIV
A few years back there was an A-10 that would fly over my grandparents vacation home on Lake George. There's basically hills along both sides of the trip of the lake. It was interesting till I realized he was about 500ft off the ground at all times. He was actually practicing popping over the hill, lining up to strafe the boats, then darting back over the hills.
500ft pffft. Many years ago, when I lived in Norwich (lots of US airbases around there at the time), I was happily driving in queue of cars on the A11 when an A-10 hammered down the road at quite literally tree top hight flying over the cars from behind.
All the way along the road you could see cars swerving as the drivers were shocked by the (quite frankly enormous) noise it made. Very irresponsible. But memorable.
(Not as noisy as an F4 Phantom doing the same thing I remember from my childhood though.)
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This space for Hire! Reasonable rates. Reach an audience of literally dozens!
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Originally Posted by Doc HM
(Not as noisy as an F4 Phantom doing the same thing I remember from my childhood though.)
Saw a Vulcan at RAF Valley when I was a kid. It flew low over the runway and then climbed at about 45°. Noise and stench was incredible. But the way that it made the ground shake was unreal.
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The closest we get is the yearly airshow.
It's gotten reasonable now. They'll practice for 2-3 hours a couple days before the show itself.
20 years ago they (Thunderbirds or Blue Angels on alternating years) would buzz office buildings for what felt like 12 hours a day for a week straight.
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Back in the 70s and 80s, most of rural Western Germany would regularly see Phantoms and Tornados doing sub-100m supersonic training flights.
Broken windows were normal occurrences.
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I recall a plane flying over my garden when I was 6 or 7 and at the time I was certain it dipped a treetop on the way over. Had no idea what it was at the time, I later thought it was C-130 Hercules but I don't think it was as big as that. Similar looking though.
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I have plenty of more important things to do, if only I could bring myself to do them....
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This is actually from reddit, but is worth it IMO.
Possums are from Australia.
Opossums are from the Western Hemisphere.
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It's not just lazy language usage? Wow, that IS something to learn.
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Glenn -----OTR/L, MOT, Tx
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I learned that people at my local Walmart sell tamales and puppies from the back of their cars and trucks.
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I don't know about the tamales, but selling puppies at Wal-Mart seems to be pretty universal.
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Glenn -----OTR/L, MOT, Tx
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Originally Posted by ghporter
I don't know about the tamales, but selling puppies at Wal-Mart seems to be pretty universal.
I feel like you're using a much different version of the word "universal"
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Mankind's only chance is to harness the power of stupid.
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Clinically Insane
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Another direct from reddit:
If you try and burp in space, you end up barfing. Gravity is what keeps the food and beverages down when you let out the air.
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TIL that even if you tell four people in the same team as yourself to get ****ed*, you can get promoted to Team leader.
*The phrase was "Allez-vous faire foutre" which is saying **** off to a group of people.
The funniest part of this, is the guy that promoted him is leaving the team at the end of April.
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