Asri-unix.1112 net.space utcsrgv!utzoo!decvax!ucbvax!ARPAVAX:C70:sri-unix!DIETZ@USC-ECL Sun Mar 28 16:18:21 1982 Advanced Rockets and SSTO's I went to an interesting presentation last night about a new rocket idea called the Dual Expander rocket engine. The idea is this: most of the mass of propellant in a rocket is burned during the first parts of the launch. As it turns out, if you want to build a single stage to orbit vehicle the fuel burned during the first part should NOT be chosen for high exhaust velocity, but rather for high propellant density. Specifically, we should use hydrocarbons (like propane, methane or kerosene) instead of hydrogen. The dual expander rocket engine burns both hydrocarbons (propane) and hydrogen. It is essentially an engine within an engine. The interior engine burns propane and LOX during the first part of the launch with a chamber pressure of 6000 psia. It is surrounded by an annular combustion chamber where hydrogen and LOX are burned. This outer chamber has a smaller aperature than the space shuttle main engine, so a smaller nozzle is needed. When the center engine is shut down it generates far less thrust than the SSME, but at that point you don't need much thrust. The eignine has a top thrust of 1/2 of the SSME, but weighs 1/3 as much. The speaker presented several designs using the engines. The first is an upgraded shuttle. The SRB's are removed, and the main tank is enlarged to include a propane tank and extra LH and LOX. On the bottom of the tank goes a cluster of (eight?) dual expander engines. Both the tank and the orbiter are placed in a stable orbit. The engines are removed from the tank and returned inside the shuttle. If you want a real heavy lift vehicle, put the SRB's back on. I forget the exact figures but this thing lifts well over 100,000 lbs. of payload. And you have a tank in orbit to play with. A one man Air Force shuttle was also described. It is much smaller than the space shuttle. Depending on the exact design, it can be launched from a C5A or from the ground. It uses two dual expander engines and strap on propane tanks that get left in orbit. Next, several commercial SSTO's. Three designs were given, the smallest smaller than the space shuttle, the largest weighing 10,000,000 lb. and having 29 (!) engines. The speaker also showed how you can take the proposed airforce shuttle, put it on an upgraded space shuttle tank and get a vehicle capable of getting to geosynchronous orbit and back again. Another proposed design used LEO refueling from an ordinary shuttle. The last and most practical design is a disposable SSTO unmanned booster. It has two dual expanders. On top goes a second stage that propels the payload to geosynchronous orbit. It could carry over 6000 lbs. of payload. The kicker is this: the first stage is ~14 feet in diameter by 50 some odd feet long. These numbers should ring a bell, because the shuttle cargo bay is 15'x60', making this a "fully reusable disposable". Final note on this thing: it can be air-launched from the back of a 747! This would avoid dynamic pressure problems. Launch procedure involves putting the 747 into a 45 degree climb at 30,000 feet, igniting the rocket and pulling negative g's to get away. Boeing is examining putting a SSME in the tail of a 747 (!) to get it higher. The launch altitude then becomes something like 50,000 or 60,000 feet. This last idea has been looked at by SAC already; in the 60's they considered putting a Titan engine in the tail of a B52 to get it away from the field quickly: said vehicle could be at 30,000 feet 30 miles from the runway in 1 minute! I hope they get to develope the engine. It uses no really new technology. The speaker claimed it could be developed in 4-5 years at a cost of $400M (1980). He works for Aerojet (the company responsible for this thing) so he isn't unbiased. ------- ----------------------------------------------------------------- gopher://quux.org/ conversion by John Goerzen of http://communication.ucsd.edu/A-News/ This Usenet Oldnews Archive article may be copied and distributed freely, provided: 1. There is no money collected for the text(s) of the articles. 2. The following notice remains appended to each copy: The Usenet Oldnews Archive: Compilation Copyright (C) 1981, 1996 Bruce Jones, Henry Spencer, David Wiseman.