Date: Sun, 24 Jan 93 05:06:40 From: Space Digest maintainer Reply-To: Space-request@isu.isunet.edu Subject: Space Digest V16 #074 To: Space Digest Readers Precedence: bulk Space Digest Sun, 24 Jan 93 Volume 16 : Issue 074 Today's Topics: *** BUSSARD RAMSCOOP *** Galileo Laser Test Successful Mir mission to Mars? ques about earlier "suicides" of SDI scientists Solar sails TAU Probe?(1000 Astronomical Units) Welcome to the Space Digest!! Please send your messages to "space@isu.isunet.edu", and (un)subscription requests of the form "Subscribe Space " to one of these addresses: listserv@uga (BITNET), rice::boyle (SPAN/NSInet), utadnx::utspan::rice::boyle (THENET), or space-REQUEST@isu.isunet.edu (Internet). ---------------------------------------------------------------------- Date: 23 Jan 93 06:52:45 GMT From: Ron Baalke Subject: *** BUSSARD RAMSCOOP *** Newsgroups: sci.space In article , jbh55289@uxa.cso.uiuc.edu (Josh Hopkins) writes... >lwahl@matt.ksu.ksu.edu (Lynne K Wahl) writes: > >>Hmmm... This sounds like an interstellar probe is needed to collect >>information before a *really* fast spacecraft is launched. How about >>a .01c speed probe with a small "sail" that would be primarily used to >>collect interstellar H (for testing) and with magnetic sensors to check >>on the magnetic medium as it goes. How far from the sun would this >>"Pathfinder" type of probe need to go before getting outside the sun's >>environment? We have four spaceraft (Pioner 10 & 11 and Voyager 1 & 2) that have already left the solar system and looking for the heliopause. I'd say one of them would reach the helipause within 10 years. >>As an exercise, how fast would, say a refueled shuttle ET, one SSME, >>and a 30 ton probe go if launched in a "generic" solar escape orbit? > >Really slowly. > >JPL proposed the TAU (Thousand AU) mission a number of years >ago. It would have used a nuclear reactor and an ion drive to boost out of >the solar system in about fifty years and check out interstellar space. >Unfortunately, since it required new power, engines and communications gear it >never got very far. The TAU mission would also use a light-wave communications system. It would study low energy cosmic rays, low frequency radio waves, interstellar gases, gravity waves and perform high precision astrometry. The spacecraft would also be targeted to flyby Pluto on its way out of the solar system. ___ _____ ___ /_ /| /____/ \ /_ /| Ron Baalke | baalke@kelvin.jpl.nasa.gov | | | | __ \ /| | | | Jet Propulsion Lab | ___| | | | |__) |/ | | |__ M/S 525-3684 Telos | Every once in a while, /___| | | | ___/ | |/__ /| Pasadena, CA 91109 | try pushing your luck. |_____|/ |_|/ |_____|/ | ------------------------------ Date: 23 Jan 1993 06:33 UT From: Ron Baalke Subject: Galileo Laser Test Successful Newsgroups: sci.space,sci.astro,alt.sci.planetary From the "JPL Universe" December 30, 1992 GOPEX reaches Galileo via laser beam By Mark Whalen JPL researchers took advantage of Galileo's recent pass by Earth to achieve a major milestone in space communications, by successfully transmitting laser beams fired from the ground to the spacecraft at distances of up to 6 million kilometers (3.7 million miles). "This experiment is part of a program to show that future deep space missions can use laser beams to send back to Earth larger volumes of space-acquired data than is currently possible using radio signals," said Dr. James Lesh, supervisor of the Optical Communications Group and principal investigator for the Galileo Optical Experiment (GOPEX). The experiment's objectives, said Lesh, were to show that an uplink beacon laser -- required as a reference for pointing a return beam back to Earth -- could be successfully pointed to a distant spacecraft based only on the navigational predicts of the spacecraft trajectory. To do this, the distortions produced by Earth's atmosphere had to be predicted and accommodated. The GOPEX demonstration began on Dec. 9 (one day after Galileo made its closest Earth approach on its way to Jupiter) at 600,000 kilometers (370,000 miles), and continued through Dec. 16. Laser beams were simultaneously transmitted to the spacecraft from a 61-centimeter (24-inch-diameter) telescope at the Table Mountain Observatory near Wrightwood, Calif. and from a 1.5-meter (60-inch) telescope at the U.S. Air Force Phillips Laboratory's Starfire Optical Range near Albuquerque, N.M. The transmissions, which were detected by Galileo's onboard camera, established a record for the farthest known transmission and reception of a laser beam, a final distance of 6 million kilometers. "GOPEX was extremely successful," said Lesh. "A real pleasant surprise in the experiment was that we conducted the experiment so repeatedly. Each day we made transmissions, we had extremely reliable detections on the spacecraft camera. "We would predict ahead of time, `on this frame, we're going to see a series of pulses about so high on the picture,' and as soon as we got the image back, sure enough, there they were," he said. Spacecraft signals produced by current radio-frequency systems are used for three purposes, according to Lesh -- communications, navigation and science investigations. "There are completely analogous applications in the laser area," he said. "We can communicate at substantially higher rates while occupying much less room on the spacecraft," said Lesh. "The antenna is the main feature on the spacecraft with radio frequencies, often reaching diameters in excess of four meters. At laser frequencies, 10-50 centimeter telescopes are quite adequate. "We can also use optical beams for navigation," Lesh continued. "When viewed from Earth, the light beam from a spacecraft will look like a blinking star. We can view it in the context of the stellar grid, or relative to target bodies we are approaching. That information can be used to derive angular coordinates of the spacecraft. "Laser signals also can be used to determine the spacecraft's range, which, together with the angle information, can be used to locate the spacecraft," said Lesh. As far as science investigations are concerned, Lesh claims that scientists could use optical signals to probe phenomena such as planetary atmospheres, to measure scattering from the interplanetary dust particle distribution, or to make spatially selective measurements of planetary ring systems using very short wavelengths (below one micron). "Also," Lesh added, "optical signals are not corrupted by solar wind fluctuations, like radio frequencies are. Some past investigations of gravitational bending of radio waves have been limited by charged particle fluctuations in the solar wind." Lesh also said laser communications technology will yield a data rate increase "of about one-to-two orders of magnitude" over radio frequencies. The idea of testing a laser uplink is not a new one. Lesh said that the GOPEX demonstration was originally proposed in June 1984, but was rejected at the time because there were no plans for Galileo to view Earth on its way to Jupiter. But the 1986 Space Shuttle Challenger accident prompted changes in Galileo's launch system and necessitated a new flight path, which included two gravity-assisted flybys of Earth. "At the same time," he said, "Earth viewing became part of Galileo's priorities, and the climate became much more receptive to our doing the experiment, subject to us demonstrating beyond any doubt that we would not damage any instrument on board the spacecraft." In that regard, preperations were made to conduct GOPEX during the Earth-1 encounter in December 1990. But inconclusive data turned up on a test to determine if the experiment might harm the Galileo orbiter's Near-Infrared Mapping Spectrometer, so "about three days before the experiment, we were waved off," said Lesh. In the intervening two years, testing of the effects of laser signals on the NIMS and Solid State Imaging Camera detectors concluded that "we were safe to substantially higher levels than we would ever produce at the spacecraft," said Lesh. What's next for the program? Lesh said proposed plans call for a flight experimental terminal to be flown aboard a space shuttle in the latter half of the 1990s. "We are developing the base technology for this now," he said, "and are trying to augment the base program with some new flight experiment monies that will allow us to do the (shuttle) demonstration." Operational use of this technology is anticipated some time after the year 2000, Lesh added. "We expect that the first deep space mission to fly optical will fly it as a mission enhancement experiment," said Lesh, "although this could change with the new emphasis on low-cost microspacecraft. "I believe that there are missions that can be best served by laser frequencies, and there are those that are best served by radio frequencies," he said. "Laser beams do require a certain amount of pointing, for example. If you have large uncertainty about the spacecraft pointing direction, it may be better to use radio waves. However, most missions currently flying or on the drawing boards provide adequate attitude control to use laser communications. "Nevertheless," said Lesh, "I don't see us de-implementing any capabilities in the future; I see us providing an additional capability that will allow future missions to plan for and make best use of the available technologies." ### ___ _____ ___ /_ /| /____/ \ /_ /| Ron Baalke | baalke@kelvin.jpl.nasa.gov | | | | __ \ /| | | | Jet Propulsion Lab | ___| | | | |__) |/ | | |__ M/S 525-3684 Telos | Every once in a while, /___| | | | ___/ | |/__ /| Pasadena, CA 91109 | try pushing your luck. |_____|/ |_|/ |_____|/ | ------------------------------ Date: Sat, 23 Jan 1993 09:11:02 GMT From: Marcus Lindroos INF Subject: Mir mission to Mars? Newsgroups: sci.space ...perhaps the Russians should have tried to boost interest in their space program in the West by launching a manned flyby mission to Mars?! A fully fuelled Energia should be powerful enough to launch a Mir space station with supplies for a crew of two plus a Proton rocket for course corrections. In addition, a Soyuz capsule for return to Earth would be needed, and probably an additional module for storing supplies and equipment. --- The entire mission would last one year, with a close Martian flyby + course correction some six months after launch. As I see it, we would obtain a lot of valuable information from doing it. For example, how do humans cope with the psychological strains of an interplanetary mission, being totally cut-off from Earth for months? We would also learn a lot about guiding a manned spacecraft millions of kilometers from Earth and similar things necessary for launching a full-scale Mars mission. --- I can't see any technical problems. The Energia is relatively untested but the crew would rendezvous with the Mir/Energia combination in orbit and not be aboard during the launch. The Suyuz was designed for lunar missions and should be able to withstand the higher temperatures of an atmospheric re-entry from interplanetary space. The weakest link? Perhaps the Mir station itself. Its systems have been unreliable for most of the missions in Earth orbit. MARCU$ -------------------------------------------------------------------------- . . . Fififinlandssvensk Marcus Lindroos Internet: mlindroos@abo.fi Computer Science Abo Akademi University Finland ------------------------------ Date: Sat, 23 Jan 1993 23:10:38 GMT From: Daniel Burstein Subject: ques about earlier "suicides" of SDI scientists Newsgroups: sci.physics,sci.misc,sci.space In <23JAN199307045841@delphi.gsfc.nasa.gov> packer@delphi.gsfc.nasa.gov (Charles Packer) writes: >In article , dannyb@panix.com (Daniel Burstein) writes... >>down the results of any investigations. The only stuff I've found has >>been news articles simply describing the venets.["events", presumably] >How about recalling where you saw the news articles, and when? >Try real hard... problem with the articles I've found is that they're only reporting the deaths, or, at best, giving a "investgators are looking into it" I haven't been able to find any coverage giving the results of the enquiries. The story just seemed to have died (no pun intended). This is -kind of- reaching into ALT.CONSPIRACY stuff, but these deaths certainly did occur, so I reached out to the SCI type nets because that's where people who deal with scientists would hang out... dannyb@panix.com ------------------------------ Date: 23 Jan 93 08:39:41 GMT From: Marcus Lindroos INF Subject: Solar sails Newsgroups: sci.space In jbh55289@uxa.cso.uiuc.edu writes: > 18084TM@msu.edu (Tom) writes: > > >Josh Hopkins: > > > >Has anyone given any thought to sailing on something besides optical/IR > >waves? How about a giant radio antenna? X-ray reflectors? > > The Starwisp uses microwaves if I recall correctly. Make an impossibly huge > mesh that's impossibly light and send impossible amounts of radio energy at it > (say a good sized SPS worth) and you've got a starwisp. I think Bob Forward's > proposal used 10 GW to boost at 115 gravities for a few days. It would then > coast at .2 C for twenty years before zipping through Alpha Centauri. There was another proposal as well. A small space probe suspended behind a giant solar sail (2km across, total mass of one hundred kg(?)) would reach Alpha Centauri in 250 years if we make a close flyby of the Sun - one solar radius from the surface (0.7 million km). Is there a way to manufacture an ultra-light sail able to withstand the temperature (4000-5000K at least)? --- The we come up with the materials and nanotechnology to do it, it might be an attractive alternative. 3-10 centuries is a long time, but the probe could double as a deep space survey probe while moving outwards and building a craft having a lifetime of a couple of hundred years will be possible in a near future. > -- > Josh Hopkins jbh55289@uxa.cso.uiuc.edu > > Q: How do you tell a novice from an expert. > A: A novice hesitates before doing something stupid. MARCU$ ------------------------------ Date: Sat, 23 Jan 1993 08:26:09 GMT From: Marcus Lindroos INF Subject: TAU Probe?(1000 Astronomical Units) Newsgroups: sci.space I recently saw a couple of pictures of the proposed Thousand Astronomical Units probe in a book by Nicholas Booth. The craft itself looks like an enlargened Cassini/Mariner mk.II, with a huge antenna dish [diameter of approx. 15 meters], an optical laser system for communications, an 1.5-meter telescope for carrying out measurements of radial velocities for nearby stars(?) and the customary particle and fields experiments equipment. --- The second part, the ion engine, wasn't really dealt with in the text so I'd appreaciate it someone could fill in the details. It's basically a long cylinder with a small nuclear reactor in the rear end powering the engine. The ion drive will accelerate the propellant [metals like Mercury or Cesium?] to velocities of up to 70km/s and will fire continuously for ten years. After that, the two parts would separate and the engine section would act as a relay station between the probe itself and Earth. The spacecraft will reach a velocity of 100 km/s and a distance of 1000 AU (0.002 light-years) in only fifty years. In addition, a Pluto orbiter could be released as the probe leaves the solar system. --- How would the probe be launched? It appears to be far too big and heavy to fit inside a standard rocket booster. Will they use the shuttle for this, and will the ion engine be used for accelerating the probe out of Earth orbit as well? --- Jet Propulsion Laboratory came up with the mission plan. Perhaps Ron Baalke can shed some light on this? MARCU$ -------------------------------------------------------------------------- . . . Fififinlandssvensk Marcus Lindroos Internet: mlindroos@abo.fi Computer Science Abo Akademi University Finland ------------------------------ End of Space Digest Volume 16 : Issue 074 ------------------------------