Subject: Space-tech Digest #74 Contents: Karl Dishaw Laser Aircraft Propulsion George Herbert Re: Laser Aircraft Propulsion Kevin Ryan Re: Laser Aircraft Propulsion Eric Baxter Re: Laser Aircraft Propulsion Bob Munck Re: Laser Aircraft Propulsion Paul Dietz Spacewatch Camera (from sci.astro) Paul Dietz More on Spacewatch Telescope ------------------------------------------------------------ Date: Tue, 16 Oct 90 22:22 EST From: Karl Dishaw <0004244402@mcimail.com> To: space-tech Subject: Laser Aircraft Propulsion Airlines are cranking their prices up because of new fuel costs. If the Gulf War gets nasty enough petroleum might be very expensive from now on. This brings back the idea of safer energy sources-- specificly solar power satellites. I'm interested in an idea for powering aircraft with SPS-powered lasers. [Sun and Hertzenberg, "Laser Aircraft Propulsion," 3rd NASA Conference on Radiation Energy Conversion, 1978] The SPS has a CO2 laser on board, the laser hits a heat exchanger on top of a jumbo jet, and the exchanger powers a turbine engine mounted on top of the plane. This is cleaner and safer than jet fuel today, and the technology required doesn't take any breakthroughs. In '78 the authors said the fuel price needed to make the project profitable was $4/gal, asssuming NASA predicted Shuttle launch costs. Has anyone seen an updated version of this? I'd like to know if the economics of this are practical. Might be the best opening to get large structures up there. Karl Dishaw kdishaw@mcimail.com internet Selenite America Online ------------------------------ Date: Tue, 16 Oct 90 21:08:06 -0700 From: George William Herbert To: 0004244402@mcimail.com, space-tech@CS.CMU.EDU Subject: Re: Laser Aircraft Propulsion This has the same problems (if not worse) as any other orbit-to-ground energy transmission. If the beam is strong enough to carry a useful amount of power, it can do a lot of damage if it hits the wrong spot on the surface. Do you want YOUR house getting zapped because the beam wandered off target onto your property? 8-) Tracking a moving plane with the beam would be worse than keeping it on a stationary ground reciever, and the plane could never fly over inhabited ground. Also, NASA's late 70's launch costs were nearly (but not quite) an order of magnitude low for what actual costs are now. The shuttle is _not_ flying at the breakeven point relative to expendable launchers, and those are a lot more expensive than the shuttle was origionally hoped to be. == George William Herbert == **There are only two truly infinite things,** == JOAT for Hire: Anything, == * the universe and stupidity. And I am * =======Anywhere, My Price======= * unsure about the universe. -A.Einstein * == gwh@ocf.berkeley.edu == ********************************************* == ucbvax!ocf!gwh == The OCF Gang: Making Tomorrow's Mistakes Today ------------------------------ Date: Wed, 17 Oct 90 10:51 EDT From: RYAN%CMIMGD <@vb.CC.CMU.EDU:RYAN@CMIMGD.DECnet> Subject: Re: Laser Aircraft Propulsion To: space-tech@CS.CMU.EDU Regarding aircraft propulsion via orbital laser: As I recall the proposal, the laser would not be much of a threat to anyone on the ground. The idea was to use a small SPS, possibly several in reasonably low orbits (makes the aiming problem easier), transmitting energy via laser to a heat exchanger on the jet. The laser was selected to emit at frequencies that are greatly absorbed by the lower atmosphere. The jet would take off using conventional engines, rise to cruising altitude, and signal the laser sat. The laser, at low power, would lock onto a retroreflector on the heat exchanger (large disk sitting on top of the aircraft, rather resembling the radar dish on an AWACS [sp?] plane, containing one or more laser powered engines). The heat exchanger would pipe the heat transfer fluid directly into a fairly low-power jet engine: cruising has lower power requirements than takeoff or landing. If the retroreflector signal dropped the laser power would be cut as well. Tracking a cooperating target is not all that hard! Aiming would be accomplished with constant feedback from the aircraft. If laser lock was lost and could not be reestablished (for some reason) the aircraft still has landing fuel and quite a ways to glide. Advantages - lower fuel usage, less fuel in the aircraft itself (just enough for takeoff and landing), range unlimited as long as a SPS was in sight. The authors noted that the amount of damage that a jet aircraft fully laden with fuel can cause is at _least_ on the same order as the size laser they proposed firing for an hour or more - assuming that the power could reach the ground, which it really couldn't. This proposal may not be practical or more likely economical; but it's certainly interesting and doesn't seem to have any show-stoopers. kwr Internet: kr0u@andrew.cmu.edu ------------------------------ Date: 17 Oct 90 12:13:56 EDT (Wednesday) From: Baxter.Wbst@Xerox.COM Subject: Re: Laser Aircraft Propulsion To: space-tech@CS.CMU.EDU Just a thought on the laser powered aircraft. How many lasers would have to be on a satellite to support the air traffic currently moving through our skies? Or could a single laser support multiple aircraft by skipping around as an aircraft signalled a need? Eric Baxter baxter.wbst129@xerox.com ------------------------------ Date: Wed, 17 Oct 90 14:24:19 EDT From: munck@Stars.Reston.Unisys.COM To: space-tech@CS.CMU.EDU Subject: Re: Laser Aircraft Propulsion In <1AD99799FE1FC9FC04@VB.CC.CMU.EDU>, kwr says: > Advantages - lower fuel usage, less fuel in the aircraft itself > (just enough for takeoff and landing), range unlimited as long as > a SPS was in sight. That brings to mind the old Skyport idea: a BIG flying wing that never lands, designed to cruise at an absolute minimum fuel useage. More conventional planes take off from airports that it is passing, dock to it (a potential difficulity), unload passengers bound for elsewhere, load passengers going to their home port, undock, and land back where they took off. Passengers stay onboard in fairly spacious accomodations and take a shuttle down at their destination. I think the Skyport proposals I've seen relied on the shuttles to bring up fuel for it, but this seems to be a natural for laser power from an SPS. I think the story involving a Skyport that I read was in Analog, a handful of years ago. Its plot was built around an accident during docking. I remember being particularly impressed by the mechanism for fast unloading and loading of passengers; it seemed to resemble the big mechanical clothes storage/transport that dry cleaners have. There's gotta be a better way than "now boarding rows 62 through 95, aisle seats first." Bob Munck, UNISYS ------------------------------ Date: Thu, 8 Nov 90 09:41:36 -0500 From: dietz@cs.rochester.edu To: space-tech@CS.CMU.EDU Subject: Spacewatch Camera (from sci.astro) The following message appeared in sci.astro. The Spacewatch Camera project has upgraded to a new, bigger CCD, and are detecting many new earth-approaching asteroids. Note the rate: 5 in 2 months, or 30 per year. >From: jscotti@lpl.arizona.edu (Jim Scotti x2717) Newsgroups: sci.astro Subject: Re: The Tunguska Event Organization: Lunar & Planetary Laboratory, Tucson AZ. Lines: 41 [ ... lines omitted ... PFD ] On 1990 October 22, while observing with the Spacewatch Telescope (36 inch), using a new automated asteroid detection system and a 2048x2048 pixel Tetronix CCD, we detected what is now recognized as the smallest natural object ever observed outside of the earth's atmosphere. The object is an asteroid estimated as being between 50 and 100 meters in diameter, and was given the provisional designation of 1990 UN. At the time of discovery, it was about 0.1 AU from earth, moving about 1.3 degrees per day and was magnitude V=20.0. Since discovery, it has moved closer to the earth, with its closest approach being on November 7.2 when it is 0.042 AU from earth. The estimated absolute magnitude is H=23.7. The object is an Apollo type asteroid with semimajor axis of 1.71 AU, eccentricity of 0.53, and an inclination of 3.68 degrees. It is currently moving deep into the evening sky and its phase angle is about 100 degrees, making it appear extremely faint. Our last chance to observe this object should be November 9 or November 10 UT, however, we hope that radar observations using the Aricebo dish may be made this weekend. With only a 3 week arc, the object will be extremely difficult to recover the next time it is bright enough to be detected. In order to be bright enough, it must be within about 0.1 AU of earth, so the chances of that happening are rather small. With the addition of radar data, the orbit calculations are greatly enhanced, and perhaps in 10 or 20 years, we may be able to search for and find this object again. The next brightest asteroid was nearly 2 magnitudes brighter, intrinsically, so this object is a whole new, previously unobserved sized object. The Spacewatch asteroid survey is intended to detect earth approaching asteroids and has just started full-time observation beginning with the 1990 September observing run. We have detected 5 new earth approaching asteroids in the two months in which we have been surveying. Our survey limit is about magnitude V=20.5 with an integration time of about 170 seconds. Jim Scotti. -- Paul F. Dietz dietz@cs.rochester.edu ------------------------------ To: space-tech@CS.CMU.EDU Subject: More on Spacewatch Telescope Date: Fri, 09 Nov 90 10:33:40 -0500 From: dietz@cs.rochester.edu Jim Scotti kindly sent me more information on the Spacewatch Telescope at Kitt Peak. The system currently uses a 5.5x5.5 cm Tektronix CCD in a 36" f/5 newtonian telescope. They operate in time delay integration mode, in which the scope is stationary and the sky is scanned using the earth's rotation, with the CCD synchronously clocked to track the moving image. Getting a 20Kx2K pixel (6.6 x .66 degree) frame takes 1/2 hour. They take three scans of the same region to find and confirm moving objects (they also look for smeared images, indicating close, fast moving objects). Their software can automatically select earth-approachers over other classes of asteroids. Jim tells me they want to further upgrade the CCD. The Tektronix CCD has low quantum efficiency, and takes 80 seconds to read out. They want to go to a smaller but more sensitive CCD in a 72" scope, with an integration time of 20 seconds in fast scan mode. This would increase the survey area by a factor of 10 while losing 0.5-1.0 magnitudes. With luck, this upgrade will be on-line by perhaps 1995 or 1996, and will increase the earth approacher detection rate by a factor of at least 5, from the current rate of roughly 3/month. This sounds great, but I wonder why the five year wait? This project seems to be giving a lot of bang for the buck, especially considering the importance of EAAs as sources of ET materials. Paul F. Dietz dietz@cs.rochester.edu ------------------------------ End of Space-tech Digest #74 *******************