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I thought that the experience of developing the GPS network (where all the sattelites and ground stations must be time co-ordinated to within 10+ decimal places
by bl4k 16y ago
I thought that the experience of developing the GPS network (where all the sattelites and ground stations must be time co-ordinated to within 10+ decimal places in seconds) would have helped them with this missile system.
A GPS satellite travels much faster than a missile, and is accurate to within meters, so the tolerances are much higher (and the system was designed prior to patriot).
There is a definite 'not invented here' syndrome amongst defense contractors - I doubt they share any information, research or solutions amongst one other, which means the US tax payer foots the bill each time one of these contractors must independently develop and implement a system that has likely already been built in another part of defense.
- some1else 16y agoOh, Interesting. I always figured GPS satellites were geo-stationary, but in fact (as you pointed out), they travel at 7000 mp/h :-0
- pmjordan 16y agoGeostationary orbits would tie the satellites to being directly above the equator, which (a) would prevent the system from working beyond a certain latitude and (b) would cause an extremely bad distribution of "visible" satellites and angles between signals, precision would suffer.
- kiujygtyujik 16y agoNot to mention the transmitter power you would need if they were 25,000miles away in GSO rather than 90mi away in LEO
- chrisbolt 16y agoGPS satellites are actually in MEO, at 12,500 miles away. http://en.wikipedia.org/wiki/Medium_Earth_orbit http://en.wikipedia.org/wiki/Medium_Earth_orbit
- tetha 16y agoNote that while you sit on your chair, you are travelling pretty fast. Relativity for the win!
- weaksauce 16y agoI would wager that some of the NIH syndrome is due to top secret requirements and blackops development that makes things tough to get at source code for other systems.
- rdtsc 16y ago> There is a definite 'not invented here' syndrome amongst defense contractors Yes. Especially because of contractors. A defense contractor is not going to its competitors in order to reveal and exchange know-how. That know-how is a trade secret that gives them competitive advantage. Except that in this case, lack of sharing results in making the same mistake multiple times, which results in loss of human life. Interestingly lately I have observed that the government is trying to tighten up its defense spending belt and there is a tendency to develop more in-house rather than contract out. In order to gain public support the Congress keeps voting to increase the salary of service personnel. That leaves less money to spend on contracting out. So perhaps we'll see more sharing in the future at least between DoD's own projects.
- gaius 16y agoThe DoD should have stuck to its guns (hah) and continued to mandate Ada.
- Retric 16y agoIt's much simpler to track and predict the position of objects orbiting the earth than moving though the atmosphere. Wind, temperature gradients, particulate matter, mist, etc add a lot of uncertainty to the predictions. PS: As you increase accuracy more things become important factors. Large Ship guns actually started to track things like temperature at different altitudes to increase accuracy.
- regularfry 16y agoAlso, a GPS satellite is actively designed to be found. A ballistic missile? Not so much.