Dale.Amon%CMU-RI-FAS@sri-unix.UUCP (08/11/84)
The skyhook SF story was most likely the novel by Arthur C. Clarke. I don't have my libary handy in my office and I don't remember the title. Something of Paradise I think. I do seem to remember I survey of the real skyhook studies in the back of the novel. The only public technical info on the Geostar system that I know of was published in two different articles in the AOPA Pilot. Both were within the last 3 years. Anyone interested in the details should latch on to a pilot friend and copy these articles. I might add that the design has been improved considerably since then, as they have actually done their pilot test. What these improvements are, I have no idea. Friends at SSI get understandably tight lipped when it comes to details like that... The reason for the cheapness is that the system smarts are centralized. Military systems do not require the navigating object to respond and give away it's position. This technical complication makes the satellite more complex and makes the receiver enormously complex and ridiculously expensive. Geostar basically uses very simple time-coded signals to triangulate the location of an object. The actual calculations are done on large, (multiply redundant), central computers. The satellites are simple high power transmitters with big receivers antennas, and the aircraft carries a simple transponder/display device. The key to the cheapness of the transponder is spreading the market to include trucks, cars, boats, hikers, etc, so that mass production cuts the cost even more. I doubt that the basic unit is much more complex than an ELT. Billing is quite simple, because anybody can buy a list of all currently active 'N' numbers and the owner addresses on floppy diskettes. I'm not sure how they intend to bill earthworms. In one swell foop, this system makes the ELT (and all it's long history of false alarms) obsolete, undersells the military efforts to become a commercial sales outfit, annihilates large portions of the National Airspace Plan (NASP), brings blind landing/takeoff capabilities within the reach of the merely well-to-do and in general gets rid of loads and loads of very very expensive avionics required for IFR flight. Of course the FAA will probably try to ignore it for as long as possible, because even though the administrations have changed, Lynn J Helms tied the agencies destiny and reputation to the above mentioned budgetary disaster (NASP), and they are unlikely to admit it publicly until forced to do so. They will probably salve their wounded pride by keeping the requirement for VOR-DME technology, although hopefully it will lay the MLS controversy to bed. We'll just have to see what happens when AOPA gets through working them over...
stevel@haddock.UUCP (08/16/84)
Geostar and ELT are not the same or even comparable systems. Geostar tells you where you are if you ask it. ELT tells other people where you are when it thinks you are in trouble. ELT works when you are lying unconcious after a crash. Geostar probably will be broken and if it does work you won't be awake to ask it where you are and how far you have to walk to reach civilazation when you wake up. A great concept is a crash hardend, i.e. expensive, Geostar/ELT device that tells the Geostar main computer that something has happened.