Subject: Space-tech Digest #143 Contents: Livermore gun launcher (1 msg) The Lightcraft Project (1 msg) Making Orbit 93 (5 msgs) Project HARP (1 msg) Trucking Galileo (1 msg) Magsail tension (1 msg) Gordon Pusch leaving AECL (1 msg) ------------------------------------------------------------ Date: Mon, 1 Feb 93 11:22:30 CST From: eder@hsvaic.boeing.com (Dani Eder) To: space-tech@cs.cmu.edu Subject: Livermore gun launcher Sender: mnr@GS80.SP.CS.CMU.EDU On Jan 27th, 1993 I visited Dr. John Hunter, of the Lawrence Livermore National Laboratory, to discuss gas gun launchers and in particular the large gun he has in testing. His ultimate goal is to build guns that can fire useful-sized payloads into space. The present gun is a scaled down version to demonstrate the technology, and which can be used for hypervelocity testing later. The gun is located in the 'back lot' test area in the mountains near Livermore, CA, several miles from the Laboratory itself, which is where the offices are. The design goal of the gun is to fire a 5 kg projectile at 4 km/s. Using a lighter projectile, 1.5 kg, it should get 6 km/s. These are 1/2 and 3/4 of orbital velocity. It was intended to be a 1/10 linear scale version of a large 'space gun', which would launch several ton projectiles at the same speed (mass scales as L^3). The projectiles would then use on-board rocket propulsion to make up the rest of the velocity to Earth orbit, leaving some hundreds of kg of useful payload in orbit. The gun consists of a pump tube and barrel mounted at right angles to each other. It was designed this way so the barrel could be elevated for altitude shots without moving the pump tube, which is bigger and heavier. At the current location, all the shots will be horizontal into filled plastic water jugs, backed by sandbags, backed by a large hillside. This is because the Livermore test area is much too small to do altitude shots. If Hunter gets some more money, he wants to move the gun to Vandenberg, where he can shoot over the ocean. The expected range will be 400km vertical with an 88 degree elevation and 700 km downrange when firing for maximum range (near 45 degrees elevation). You don't want to shoot at 90 degrees, because then the projectile falls back on you. The pump tube is about 75 meters long, 14 inches in ID, and 17-20 inches in OD. It is thicker at the ends. In operation, the pump tube has a 1 ton piston (about 1 meter long) located near the far end from the barrel intersection. A methane-air mixture is pumped in to 10 atmospheres. In front of the piston, the volume is filled with hydrogen gas. The methane-air mix is ignited, and the piston drives down the pump tube at several hundred m/s. The hydrogen is compressed and heated until a rupture disk gives way, somewhere over 10,000 psi. The rupture disk is a stainless steel plate with an x-shaped groove cut in it. The depth of the groove is controlled so that the plate ruptures and opens in four petals. The hydrogen gas then accelerates the projectile. The piston is shrinking the volume in the pump tube faster than the projectile is creating volume by moving in the barrel, so for a while the pressure continues to rise, reaching a peak of 50,000 psi. The barrel is 30m long and 10cm in ID, and about 20-25 cm in OD. The end is covered by a polyethelyne sheet (about 10 mils) that keeps air out of the barrel. Most of the air is pumped out before firing. The residual air blows away the plastic film before the projectile gets there. The test projectiles are made of Lexan, about 50cm long, 10 cm in diameter, and mass 5 kg. The early tests were with compressed air driving compressed air, and reached 400 m/s, the most recent tests were compressed air behind the piston driving hydrogen gas, and reached 800 m/s. For comparison, this is about the speed of an artillery shell. These early tests are to make sure the mechanical parts work okay, the instrumentation works, etc. They are starting now on the combustion-driven shots, which will start at about 10% of a full propellant load, and ramp up in small steps, in case something starts to give. It is a real experimental mode. They will also get data on speed vs. gas load to use in later, less than full power shots. Among the things to fire out of this gun, after the gun itself is tested, is heat shield designs, and scramjet combustors. There is currently no other way to test above Mach 8 for more than a few milliseconds in a shock tunnel. Firing scramjet parts into real air at high speed and at reasonable scale has excited some interest already. Hunter's next gun would be one that uses a heat echanger rather than a driven piston to create the hot, high pressure hydrogen. This concept comes from the work done at Brookhaven on particle- bed nuclear rockets (Timberwind project). The gun would have no nuclear parts, but uses the same principle of small particles with lots of surface area to get high heating rates. By going with a particle bed heat exchanger, the pump tube, which is the biggest piece of hardware, goes away, shrinking the gun cost by 50%. This would be a small gun to demonstrate the design, then later guns would scale up to useful payloads. The reason Hunter didn't start with this type of gun was the Timberwind work was highly classified until after he had started building the current gun. Testing up to full power should take until late Feb. or Early Mar, it takes about 3 days to clean the gun and prepare for another shot, plus whatever glitches turn up. The gas gun that belongs to the University of Alabama at Huntsville, which I visited a month ago, can get about 1 shot per day, and has been doing that for 25 years. Dani Eder ------------------------------ Date: 3 Feb 93 12:58:00 EST From: "MITCHELL JAMES" Subject: The Lightcraft Project (SSI) To: "space-tech" In the Nov/Dec 1992 SSI Update is an article on "The Lightcraft Project". In that article on page 2, top center column, it states, "This laser energy is transferred directly into the air by inverse Bremsstrahlung absorption and creates a high pressure explosion." What is Bremsstrahlung absorption? Is the explosion driven only by the laser energy? Is there something special about laser light as compared to intensified sunlight for this purpose? Mitchell James mjames@bgm.link.com ------------------------------ Date: Thu, 4 Feb 93 07:21:44 -0500 From: dietz@cs.rochester.edu To: space-tech@cs.cmu.edu Subject: Making Orbit 93? Henry (or someone): could you post some more details on what you heard at Making Orbit 93? I'd especially like to hear about the hydrocarbon/peroxide SSTO concept (was it pressure-fed?). Paul ------------------------------ From: henry@zoo.toronto.edu Date: Thu, 4 Feb 93 15:15:31 EST To: space-tech@cs.cmu.edu Subject: Re: Making Orbit 93? >Henry (or someone): could you post some more details on >what you heard at Making Orbit 93? I'd especially like >to hear about the hydrocarbon/peroxide SSTO concept >(was it pressure-fed?). I expect I'll be posting bits and pieces over the next couple of weeks, as topics come up. Yes, the JP5/H2O2 SSTO design was pressure-fed, using Kevlar-wrapped tanks. (Bruce Dunn exhanged notes with him about peroxide and cautioned him to take a good hard look at his pressurization system.) This was a fully reusable manned vehicle, a la DC-1, by the way... and Max Hunter was co-author on the paper. (It might be in the proceedings, although it was meant for publication in something like JSR and Mitch might want to save it for that.) Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: Thu, 4 Feb 93 16:31 PST To: space-tech@cs.cmu.edu Subject: Making Orbit 93 From: Bruce_Dunn@mindlink.bc.ca (Bruce Dunn) > dietz@cs.rochester.edu writes: > > Henry (or someone): could you post some more details on > what you heard at Making Orbit 93? I'd especially like > to hear about the hydrocarbon/peroxide SSTO concept > (was it pressure-fed?). > > Paul Below is one piece of information which I already posted to sci.space. I repeat it for those who may have missed the posting, or who don't scan this USENET group. I will reply in a separate message to the question about the hydrocarbon/peroxide SSTO. xxxxxxxxxxxxxxxxxxxxxxxx I recently attended the "Orbit 93" conference in Berkeley. The following are notes I made at the presentation "Delta Clipper" by Bill Gaubatz, head of the SSRT program at McDonnell Douglas. The presentation was given using professionally prepared view-graphs from MacDonnell Douglas, many of which were marked "competition sensitive" (presumably reflecting the preparation of the view-graphs before MacDonnell Douglas won the contract for the DC-X test vehicle). Delta Clipper vehicle: The following comments refer to the "Delta Clipper" (name used during the talk) or DC-1 (name used on the net), the eventual product of a development program involving a DC-X technology demonstrator and a DC-Y prototype. Planned capability is 16,000 lbs to a 220 nautical mile orbit, 25,000 lbs to an unspecified LEO (low earth orbit). Vehicle is roughly three times as long as it is broad. The upper end is bullet like, becoming wider towards the base. The cross section is circular, except at the base where the four main engines give the shape of a round edged square. In addition to the four main engines, there are four smaller engines. Engine type was not specified in the view-graphs. The vehicle burns hydrogen and LOX, and has a cargo bay at mid-vehicle. The cargo bay is 15x15x30 feet, and has a door to the side of the vehicle. The cargo is supposed to be put into a standard container, and loaded into the cargo bay using a simple ground-based scissors jack. The standard container will have power, coolant, and data transfer connections for maintaining the health of the payload. Gaubatz says the vehicle is "people capable", a term which he prefers to "man rated" which he implies is a term which should be used only for older style launchers. The vehicle has large design margins based on current aircraft practice, so that the vehicle will have a long lifetime. The vehicle will have "reliability centered maintenance", a buzz term which was not particularly clearly defined by Gaubatz. Gaubatz says that for design work, MacDonnell Douglas has brought together people with rocket skills (from their Delta commercial vehicle group) and airplane skills (from their aircraft group). In reply to a question from the audience, he stated that the group was about 60% rocket people, and about 40% aircraft people. The total launch crew in the "flight operations center" (he points out that "blockhouse" is not appropriate) is 3 people; a "flight operations manager" and deputy, and a ground operations controller. Drawings show something like a control tower for operations, with no provision for protection against explosions. Ascent to orbit will involve a burn of 369 seconds, with a maximum G loading of 3.0 The vehicle will have engine out capability at any time in flight. On ascent, once past 60,000 feet (about 9 miles downrange) the vehicle will pass out of FAA control - prior to this FAA clearance will be used. The vehicle enters nose first. The re-entry aerodynamics of the vehicle are derived from the very large body of data which is available on missile warhead re-entry aerodynamics. The angle of attack of the vehicle is controlled to minimize thermal loading. The vehicle has a 1200 to 1500 nautical mile cross range. Deacceleration is 1.1 g maximum during descent. On descent, the vehicle goes subsonic at 60,000 feet altitude, and the engines are then started and idled. At 5000 to 10,000 feet altitude, the vehicle is rotated base down. 2 engines are powered up to deaccelerate and land the vehicle (note that the other two main engines are idling, and can be powered up if needed). The vehicle will land on a pad using retractable landing gear. Wheels will be attached to the landing gear, and the vehicle rolled over to a "flight stand". After placement on the flight stand (which takes the weight of a fueled vehicle), the vehicle will be given a new payload, fueled, and reflown. Gaubatz notes that the noise footprint for a vertical takeoff and landing is more restricted than the noise footprint for a horizontal takeoff vehicle. Most maintenance is projected to take place on the flight stand - in normal circumstances a 12 hour turnaround is expected. Minor maintenance with "line replaceable units" will take less than 24 hours, while major maintenance involving interior components such as fuel cells will take place in less than 1 week at an adjacent hanger. Once a year, the vehicle will undergo a 30 day maintenance and certification. Gaubatz notes that the launch organization for the existing commercial Delta expendable launcher involves 320 people, who can send off 12 flights per year. He claims that this is the most efficient launch organization in the US. He claims that the same number of people will be able to support 4 to 5 Delta Clipper vehicles, each flying 40 times per year. He further notes that for expendable launchers, two thirds of the cost of a launch is for the cost of the expended hardware. DC-X vehicle: The following comments refer to the DC-X experimental vehicle, currently being built by MacDonnell Douglas for proof of concept testing: The DC-X program is a 2 year program, costing about $60 million. Gaubatz states that were the program handled in the "usual NASA manner" it would have been a $ 1000 million program, taking 5 to 8 years. The DC-X is similar in shape to the final Delta Clipper, but one third scale. The hydrogen tank is on the bottom of the vehicle, while the oxygen tank is on the top. The nosecone and tail of the vehicle is being built of composite material by Burt Rutan, of Scaled Composites. The interior of the hydrogen tank is lined with balsa wood bonded to the metal (no- this is not a typo). All avionics are off-the-shelf from current aircraft instrument manufacturers. The vehicle is not designed to go above about 30,000 feet and does not carry enough fuel to get to orbit. MacDonnell Douglas however seems to be thinking about using the DC-X as a reusable sounding rocket after testing is finished ("SOAR" = Sub Orbital Applications Rocket"). The vehicle is unmanned, and is flown by computer with links to ground control. The major objective of the flight testing is to verify the design tools and assumptions used, in order to demonstrate the feasibility of the McDonnell approach to building an SSTO. Vehicle engines are an RL-10 derivative with a reduced expansion ratio for atmospheric flight. Isp at ground level is 337, and the engine can be idled at about 10% power, and run at any setting between 30% to 100 % power (3700 to 13500 lbs force). Only 30% power is required for landing. The first engine tested already has "a couple of hours" of run time (impressive for an engine originally designed as a throw-away item which only had to run for a few minutes). Considerable testing has been done to demonstrate "snap throttling", or very rapid changes in engine power. There are probably 4 engines (the viewgraph was confusing so I am not certain on this point). The RCS (Reaction Control System) runs on gaseous hydrogen and gaseous oxygen, and is in a replaceable module in the base of the vehicle between the engines. The top of the vehicle has a compartment for a parachute, for a "belt and suspenders" approach to getting the vehicle back in one piece. The top of the vehicle also has GPS receivers. The vehicle is launched by a 3 person crew in a trailer (flight operations manager, deputy, and ground operations controller). Total testing crew will be 35 people. Testing will be from WSSH, or "White Sands Space Harbor", starting in late May of this year at the White Sands Missile Range in New Mexico. Some provision will be made for the public to watch the testing - arrangements are not yet firmed up but will be publicized when available. Gaubatz notes that the White Sands people have been very co-operative. Gaubatz wants to test at White Sands to "get away from the current launch culture" (presumably represented by NASA). The vehicle will not carry a destruct package - something that Gaubatz regards as a victory over the existing launch culture and a demonstration of the reasonableness of the White Sands range safety people. Landing gear of the vehicle is retractable, and made by MBB (Deutsche Aerospace, in Germany). The landing gear is designed for up to a 7 G landing, and rough field capability is designed in. The landing gear is retracted during takeoff, and only deployed in the terminal phase of landing. Flight software is designed as much as possible to be the same software that would be used in controlling the final Delta Clipper vehicle. The software is being written in ADA, and is ahead of schedule and under cost. Gaubatz says "If I could build the whole vehicle out of software, I would". The flight operations control screens are designed to look like a "glass cockpit" in a modern airliner. Items displayed on the screen can be "clicked on" (presumably with a mouse) to display further information. Gaubatz is "fully anticipating overall success". Burt Rutan figures that the simplest approach to flight control is to put a pilot on board the vehicle. One of the flight controllers (operating a computer console on the ground) will be Pete Conrad. Gaubatz states that Conrad has been eyeing the parachute compartment in the DC-X, and hinting that if the parachute were removed, there would be room for a pilot! -- Bruce Dunn Vancouver, Canada Bruce_Dunn@mindlink.bc.ca ------------------------------ Date: Fri, 5 Feb 93 10:48:54 -0600 From: ewright@bach.convex.com (Edward V. Wright) To: Bruce_Dunn@mindlink.bc.ca, space-tech@cs.cmu.edu Subject: Re: Making Orbit 93 >The flight operations control screens are designed to look like a >"glass cockpit" in a modern airliner. Items displayed on the screen >can be "clicked on" (presumably with a mouse) to display further information. Yes and no. The control center looks like a "glass cockpit" in that it uses CRTs but the screens, which were designed by Pete Conrad, are more like those an industrial plant manager would see. >MacDonnell Douglas however seems to be thinking about using the DC-X >as a reusable sounding rocket after testing is finished ("SOAR" = >Sub Orbital Applications Rocket"). This would not be DC-X, but a larger vehicle, sometime knows as DC-X' (that's DC-X prime). DC-X will never fly again after the end of its test program. McDonnell Douglas only has four of the RL-10 engines used on DC-X (the vehicle uses all four engines), and, when one of the engines fails and can't be fixed, the test program is over. That's why McDonnell Douglas gives a range for the number of test flights planned rather than a single number. ------------------------------ To: uunet!zoo.toronto.edu!henry@uunet.UU.NET Cc: space-tech@cs.cmu.edu, gwh@lurnix.COM Subject: Re: Making Orbit 93? Date: Fri, 05 Feb 93 16:31:01 -0800 From: gwh@lurnix.COM Re: Making Orbit 93 Argh; There it was, no more than 3 miles from my appartment, and I stayed home because I had a cold and missed seeing Bruce and talking to Henry again 8-( That peroxide/hydrocarbon SSTO isn't going to work. The strength of Kevlar composite as opposed to unidirectional Kevlar fiber is a factor of 3 to 3.5 weaker. (I have the source, _Designing with Advanced Composites_ by ??? (A Springer-Verlag grad-level engineering text) at home and can cite it later, with details...). I also suspect that they'll detonate their oxidizer supply... my mother, who did physical chemistry (i.e. blew things up at Stanford Research Institute back in the late 60's), refused to help me work with Peroxide if I was going to freeze or boil it or anything similar. [Bruce, take notes: she was a pro at dealing with explosives and thinks that Peroxide is a bad idea...]. She had a much better reaction when I told her I was going with straight Nitric Acid... On to more cheery news; I was home sick for the last 10 days, and got a couple of days more work done on my big dumb vehicle concepts and initial test setup. I now have a list of materials I need for the first stages of testing, a preliminary design for a test stand, I've reworked some of the testing so that I can do it at my fammily place in the country instead of a professional test site, and as soon as my tax refund gets back (giving me some spending money) stage 1 testing begins. I've just completed another redesign round of the small test vehicle, and I'm moving away from clustering to larger single engines. Reliability concerns are the driving force at this time; you don't gain reliability if you have a multi-engine design with no engine-out capability, you lose reliability. And thus, to increase system reliability, I move to single motor systems. Less failure points, and more redundancy in the critical areas is afforded. -george william herbert ------------------------------ Date: Sat, 6 Feb 93 13:43 PST To: space-tech@cs.cmu.edu Subject: Project HARP From: Bruce_Dunn@mindlink.bc.ca (Bruce Dunn) Dr. G. Bull was murdered several years ago in Europe. He was probably killed as a result of his activities related to military weapons in the Middle East. In the 1960s, Dr. Bull was associated with project HARP (High Altitude Research Project), run out of McGill University in Montreal, with U.S. Army funding. Project HARP involved the use of large guns to fire instrumented ballistic projectiles and rockets to high altitudes. The program seems to have been terminated in approximately the mid 1960s. Bull later became an arms designer and arms broker, who had dealings with Iraq among other countries. Following are some notes on the HARP project, which make an interesting comparison with the light gas gun launcher recently described by Dani Eder. Paper 1: Bull, G.V. (1964) Development of Gun Launched Vertical Probes for Upper Atmosphere Studies. Canadian Aeronautics and Space Journal 10:236-247. This paper was written to accompany a speech made by Bull in Toronto in May 1964. In the Introduction to the paper: "During the past several years, both theoretical and experimental investigations have been undertaken to determine the applicability of guns to scientific studies of the ionosphere. Such possibilities have intrigued ordnance workers for many years, but involve a complex mixing of advanced gunnery techniques, scientific experiment considerations and economics. "In late 1961, with material support from the US Army, McGill University undertook the development of a 16 inch gun system. In early 1962 this program came under full support of the US Army through the Army Research Office and the Ballistic Research Laboratories" In a section on sub-caliber ballistic projectiles, Bull says: "For example, in the case of a 16 inch naval gun which normally fires shells in the 3,000 lb. class at velocities of 2,800 fps, velocities as high as 6,000 fps can be obtained with shot weights of the order of 400 lb., the sub-caliber vehicle in this case having a ballistic coefficient considerably higher than the normal shell. By re-design of the gun (i.e. extending the chamber and barrel) to optimize at this lighter shot weight, velocities approaching 7,000 fps are possible." A series of sub-caliber "Martlet 2" vehicles were built, which were sub-caliber and rode the barrel in a fall-away sabot. Canted fins on the projectile maintained aerodynamic stability, and spun the projectile up so that it was stable once leaving the atmosphere. These were fired at elevations of from 60 to 90 degrees from a 16 inch naval gun (on loan from the U.S.) which was located in Barbados. The gun was bored out to 16.5 inches and made into a smooth-bore cannon. Altitudes of approximately 500,000 to 600,000 feet (100 miles, 160 km) were projected for this arrangement, and early trials reported in the reference cited went as high as 112 km. Martlet vehicles carried instruments made from discrete solid-state electronics - they were potted in a mix of epoxy and sand (!) and the designers did not seem to have any real trouble getting the electronic to survive the launch acceleration which peaked at approximately 20,000 g. Martlet vehicles also routinely carried a liquid mixture of trimethyl-aluminum and triethyl-aluminum to be released at high altitudes for ionosphere studies. Another option was to carry sodium-thermite mixes which when ignited would release sodium vapor (a type of experiment similar to the Pegasus satellite barium releases). If projectiles of a similar weight were fired for range rather than height then ranges of up to 150 to 200 miles were calculated, depending on the ballistic coefficient. Shots from the gun were routine and relatively inexpensive. Bull states: "Normally, loading of the gun can be accomplished in under one half hour, allowing a firing rate of one an hour." "Standard service propellant available as surplus (WM/.245) has been used, and the gun geometry has not been modified. Firing programs are planned for the summer and fall of this year [1964] when the gun barrel will be extended and lighter sabots used with propellant designed to match the light projectiles, which should extend the Martlet 2A apogee to 200 km." [if I remember correctly, the gun was fitted with a fiberglass muzzle extension which was successful in improving the performance]. "The economics of the gun launched probe has been as predicted, with the Martlet 2A airframes loaded with TMA/TEA and a flare in the nose cone varying in price between $2500 and $3500, with gun launch costs (propellant and gun wear) included." After having discussed ballistic projectiles, Bull discusses gun- launched rockets: "Gun fired artillery rockets have been developed extensively since World War II and normally must withstand barrel acceleration loads of the order of 30,000 g along with the rotational loads superposed by shell spin. The performance of this type of rocket is only of marginal interest in the vertical probe application where non-spinning (from a stress viewpoint) vehicles are flown at acceleration levels of less than 10,000 g and relatively very large rocket motors are desired with high mass fractions. In May of 1963, work was started on what was designated as the Martlet 3A rocket assist vehicle as part of the HARP program. The objective of this activity was the development of a 16 inch gun launched probe which would carry some 40 lb. of payload to altitudes in the 500 km range." The Martlet 3A and later 3B rocket vehicles were sub-caliber and used various solid propellants in various configurations. The main problem with gun launched rockets is supporting the solid propellant during the launch acceleration so that it does not collapse into the internal cavities molded into the propellant grain, and a lot of development work was performed to investigate the performance of various solid propellant grains. From their knowledge of the performance of the 16 inch gun system and general information about the specific impulse and mass fraction of solid fuel rockets, it was calculated that it would be fairly easy to put a payload into orbit using the HARP gun and a multistage solid fuel rocket. Orbital Launch Vehicle Characteristics from Figure 31 in the Bull paper: Total launch weight: 2000 lb. Stage 1 weight: 1440 lb. Stage 2 weight: 403 lb. Stage 3 weight: 117 lb. Payload: 40 lb. Muzzle velocity 4500 fps Mass fraction 0.8 Specific impulse 300 sec (vacuum) [Note from B.D.: I think that the Isp estimate of 300 sec is overly optimistic, and would be happier believing 280 with the limited expansion ratio nozzle which could be fitted onto a gun launched rocket ; the mass fraction however is probably less than could be achieved using modern composite materials for the motor case - overall, the calculations probably hold up ok] The first and second stages were to be fired at relatively low altitude, but clear of the atmosphere. The third stage was to circularize the orbit, and would be fired horizontally at orbital altitude. Such a vehicle was never built, although motors of the first stage size were developed. The HARP group was also involved in exploring the possibilities of launching liquid fueled rockets from the gun. These could be thin-shelled as long as they had no gas spaces in them (you can accelerate a balloon full of water at any g force you like, as long is it is fully supported during the acceleration). Paper 2: Eyre, F.W. (1966) The Development of Large Bore Gun Launched Rockets. Canadian Aeronautics and Space Journal 12:143-149. "The concept of a rocket launched from a gun is not new. It will suffice to affirm in this paper that the gun launched artillery rocket was in full development during the Second World War and this investigation still continues. Like so much work in allied fields, a great deal of what has been done and is being done is classified and cannot here be repeated." "The conventional solid propellant gun, firing meaningful projectiles, currently appears able to develop a maximum muzzle velocity of some 6000 to 9000 fps. Allowing an 80% recovery of muzzle kinetic energy as potential energy, this corresponds to a ceiling for sounding work of some 800,000 to 1,000,000 ft. (say 160 to 200 statute miles). Significant improvements beyond this level must come either from use of a different type of gun or from rocket boost during vehicle flight, which is here considered." "Figure 3 shows muzzle velocity vs. shot weight for the Barbados gun. [HARP]" "Assumed conditions: Max. pressure 60000 psi Fixed charge, 1000 lb. M8M propellant Web size optimized." [some approximate data points from Figure 3 graph, and from Figure 4 showing acceleration vs. shot weight] Shot weight Muzzle velocity Max. acceleration 500 lb. 7700 fps 13,000 g 1000 lb. 6400 fps 9,000 g 1500 lb. 5700 fps 6,500 g 2000 lb. 5200 fps 5,000 g Eyre then goes into a long technical discussion related to how to support propellants of various types in a solid fuel rocket during the gun acceleration. Perhaps the neatest concept is to simply fill all empty spaces in the rocket with a fluid which then can support the propellant grain hydrostatically during launch (sort of a rocket water- bed). The rocket is then accelerated using some form of pusher plate, which seals the liquid in. The plate drops away after launch, and the fluid is then vented or drained before ignition. With regard to practicality and performance, Eyre writes: "It has transpired in design studies that although structural problems do arise due to the acceleration loads, and additional problems are posed by the necessity to use a folding stabilizer assembly, mass fractions almost as high as conventional rockets can be achieved and the design problems are partially alleviated by an all supersonic flight regime. Given this condition the advantage of the gun can be seen in that a typical vehicle of mass fraction 0.8 would have an apogee of 176 miles used conventionally, 257 miles at 1000 fps launch, 342 miles at 2000 fps, 435 miles at 3000 fps, 529 miles at 4000 fps and so on." Eyre then discusses the fabrication of a full-scale, full bore (16 inch) motor with a weight of 1450 lb., designated the Martlet 4A and designed for the Barbados gun. At the time of writing of the paper, it does not appear as if this had yet been test launched - I do not know how far the program was carried before it was canceled. "Current work is directed towards development and application of a thin plastic wear resistant coating [they were worried about excessive wear on the rocket casing], and launching of 16 inch motors to investigate scale factor effects. At the time of writing [1966] full bore Aerojet General Corp. grains are awaiting launch. ... At the present time a heavy test program is about to commence with many agencies participating and for the most part full scale hardware ready for launch." In summary, up until the time of writing of the later of the two quoted papers in the mid 1960s, HARP under Dr. Bull appeared to have been highly successful using a surplus 16 inch naval cannon in firing projectiles to high altitudes and in firing solid fueled rockets. His comment on vehicle design for guns of different scales is interesting: "Obviously since launch weight (ie payload) is increasing roughly as the cube of the scale, while peak accelerations are decreasing linearly, the larger the gun the simpler the vehicle engineering problem." Bruce Dunn Vancouver, Canada Bruce_Dunn@mindlink.bc.ca ------------------------------ Date: 28 Jan 1993 00:19:46 -0500 (EST) From: "GORDON D. PUSCH" Subject: Trucking Galileo --- update and retraction To: space-tech@cs.cmu.edu I found the 1991-Dec issue of _Ad_Astra_ (v.3, n.10, pp.12--17) while packing, and contrary to my previous claim, it did not, repeat, *NOT* state that Galileo failed the antenna-opening test before launch; on the contrary, it "passed with flying colors" after arrival at KSC. However it *did* quote Project Manager Wm. O'Neil as saying that in retrospect, they should have "lubricated the pins just before final stow for launch," that it was "never raised as a concern," and that future anntenas should include "push-off springs" to ensure deployment. It also states that a JPL spokesperson refused to say how much trucking Galileo cost, but that Tom Williams (Deputy Project Manager, Advanced TDRS) says that flying it would have cost about $65K/flight --- or about 0.005% of Galileo's $1.4G pricetag... I *still* think it was a foolish economy... and that it should have occured to *somebody* that ten years is too long to wait between lube-jobs... :-( Gordon D. Pusch ...for two more days :-( ------------------------------ Date: 28 Jan 1993 01:04:38 -0500 (EST) From: "GORDON D. PUSCH" Subject: Magsail tension --- and update To: space-tech@cs.cmu.edu I've been meaning (in my copious free time) to get back to the magsail- tension problem, but haven't had time yet. Maybe I'll do it while I'm, uh, *waiting* to start my next job... :-( G.E. Lee-Whiting found an error in his original calculation of the tension some time ago; it *does* in fact indicate a logarithmically-divergent tension a-la Paul Dietz and the Landau-Lifschitz result. However the force/arc-length *does* vanish as I kept insisting to Paul --- it just doesn't do it fast enough to keep the tension from diverging, thus resolving the "paradox" posed by the vanishing circumferential force- density in the infinite major-radius limit... It is not yet clear to us whether G.E.L-W's calculation *actually* yields the _mechanical_ tension --- there are some questions whether the Lorentz- force density integrated over an *open* surface can really be legitimately set equal to the integral of the mechanical stress, since the usual proof uses Gauss's theorem for *closed* surfaces... I've been meaning to do a self-consistent perturbative magnetoelestic calculation, but it's been a rawther low priority --- maybe I'll get to it in my soon-to-be copious free time... I found some refences on the "Virial thm" BTW --- but I think there may be something fishy about the derivation --- among other things, it always seems to assume the conductors are a "perfectly incompressible fluid," rather than an elastic medium... I found several references on *numerical* magnetoelastic stress calculations, and it appears that it's a *REALLY* tough problem; regardless of whether one uses virtual work, direct Biot-Savart plus Lorentz-force, or several other approaches, it boils down to taking the small difference of two enormous numbers somehow, so the result is mostly round-off error. There are also consistency problems --- for example, a finite-element calculation of the magnetic field (and therefore force) will only be C^0 continuous, and therefore can't be consistently inserted as a load in a finite-element stress calculation... :-( Finally, our local finite-element expert says that finite-element hoop-stress calculations really can't be trusted when the major- to minor-radius ratio gets really big --- round-off error again... :-( If I ever resolve this issue, I'll let y'all know --- in the meantime, it's really a non-issue, since the tension can be more effectively taken up by the radial shrounds than the by the hoop-stress... :-T Gordon D. Pusch ... for two more days :-( ------------------------------ Date: 27 Jan 1993 23:57:34 -0500 (EST) From: "GORDON D. PUSCH" Subject: Leaving AECL (and SPACE-TECH, for a while :-(... To: space-tech-request@cs.cmu.edu ... I'll actually be leaving AECL on 1993-Jan-29, so I'll be off the air until I either get another job, or subscribe to "CompuServe" or "GEnie;" I sure hope it's the former... :-( Gordon D. Pusch (for two more days :-( ------------------------------ End of Space-tech Digest #143 *******************