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A bit of development history at "GPS Almost Ended Before it Began": > The death struggle: NRL wanted a two-dimensional system, and Parkinson and the Air Force
by throw0101c 3y ago
A bit of development history at "GPS Almost Ended Before it Began":
> The death struggle: NRL wanted a two-dimensional system, and Parkinson and the Air Force wanted three dimensions plus time. The NRL patent called for atomic clocks in the user equipment, which would have made them prohibitively expensive. Parkinson and the Air Force wanted atomic clocks on the satellites instead, which would greatly simplify the GPS user receiver if atomic clocks could be modified to fly in the high-radiation environment of space. It wasn’t going to be easy to do, but space-qualifying atomic clocks turned out to be possible. NRL had tried to orbit a laboratory atomic clock, but it had quickly failed under the intensity of space radiation.
> With these modified concepts all defined, Parkinson spent the next three months trying to, at least, convince the key players in DoD not to say no. In December 1973, the Defense System Acquisition Review Council reconvened and voted yes. It was not that everyone in the military liked what they saw. Many navigation officials in the services liked the systems they had such as TACAN, VOR, DME, LORAN, etc. The Air Force was particularly opposed to GPS and no doubt preferred more airplanes.
* Embedded PDF: http://www.brightcopy.net/allen/avne/60-9/index.php#/p/20 http://www.brightcopy.net/allen/avne/60-9/index.php#/p/20
* https://en.wikipedia.org/wiki/Bradford_Parkinson https://en.wikipedia.org/wiki/Bradford_Parkinson
- nradov 3y agoIt makes you wonder what other proposals actually were killed at an early stage that would have succeeded brilliantly had they been funded.
- syncsynchalt 3y agoI firmly believe that the GPS we got is the best option we could have picked. I've read a lot of the design papers from the 60s and 70s that formed GPS. The initial design was a 3-satellite constellation that would only cover Viet Nam. Options considered [1] included a receiver broadcasting to the satellite (wouldn't scale infinitely) or having an atomic clock in each receiver (high cost and weight). The expectation would be that there were about 100 GPS receivers worldwide: those installed in USAF and USN planes, and possibly some in USN ships or US Army tanks. One constraint they eventually settled on was that a receiver should be portable (less than 50kg) and inexpensive (less than $500k adjusted)[2]. It just goes to show how far we've come from what was at the time considered ambitious in its size and cost goals. [1] https://www.xyht.com/wp-content/uploads/2016/07/3-5-redacted-TOR-10012525-17-1-Briefing-navigation-satellite-study_Redacted.pdf https://www.xyht.com/wp-content/uploads/2016/07/3-5-redacted... page 57 [2] https://www.xyht.com/wp-content/uploads/2016/07/3-5-redacted-TOR-10012525-17-1-Briefing-navigation-satellite-study_Redacted.pdf https://www.xyht.com/wp-content/uploads/2016/07/3-5-redacted... page 73
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- Rebelgecko 3y agoThe original Woodford & Nakamura TOR has a really cool hand drawn table showing all of the alternatives and their pros/cons. It was definitely for the best that they went with the most technically challenging option (inventing atomic clocks that are small enough to go to space) since that choice is responsible for a lot of the neat aspects of GPS (users don't need to be near ground stations, they don't need their own synchronized clocks, and GPS receivers really are receive-only) Edit: just scrolled down and saw that my comment is a bit redundant with syncsynchalt's :)