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Repost: Hydrogen peroxide helicopter (and Len Cormier's Space Van)
My earlier response on sci.space.tech seems to vanished
into outer space--along with a number of other replies on sci.space.tech. "Lawrence Gales" wrote in message news:Pine.WNT.4.58.0407172228370.1384@your-kgj38sd53j... [snip] You might check out Len Cormier's Space Van 2008: http://www.tour2space.com/sv2008/sv2008.htm Len claims a number of advantages in *slowly* getting an orbiter to a high altitute (about 70,000 feet) and then releasing it at a moderate speed, about 350 mph: - Greatly reduced structural weight due to o Not having to fight your way at high speed through the lower atmosphere (remember the shuttle would tear itself to pieces if it did not throttle down to 65% around 40,000 feet) Unless you have a carrier aircraft bringing the launch vehicle up to altitude you're trading off one sticky problem for another. You still must use an oxidiser, if you expect the launch vehicle to be airbreathing until using rocket propulsion you have the issue of added weight unless you jettison something. Yes, airbreathing is not a promising way to climb to very high altitudes because of extreme density changes. Rocket propulsion, however, albeit heavy initially, is a good way to climb to high altitude. The high initial mass of a rocket system is of little consequence, if the propellants are cheap, and the tanks, engines, and fabric-covered, span-loaded, truss structure wing are light. The resulting system is light at altitude, where being light is important. Moreover, this part of the system is strictly subsonic and does not continue to orbit with the orbiter. o Not having to have strength in as many directions as its attitude is always nearly horizontal Now you have TWO structural problems instead of one. You must still have the strength to withstand the acceleration when the rocket is thrusting (2-7+G plus dynamic loading) AND you must have the horizontal strength to withstand the structural load of being hoisted to altitude (probably 2-5G plus dynamic loading) and this horizontal lift must be performed while fueled Acceleration is much less. Initial thrust-to-mass is only about 0.4. Normal loads from lift are less than 2 g's--with initial ultimate normal loads of 3 g's, allowing for safety factor. Most importantly, dynamic pressure is held to less than 2500 Pa (52 psf); this avoids panel flutter problems, as well as structural load problems on the orbitr aero surface which can now be designed for low-q reentry, approach and landing. o Less need for streamlining and thus more efficient packaging How high do you expect to lift this thing slowly. Unless its up to ~200,000ft+, you are still going to have big aerodynamics problems. Separation altitude is 21,300 m (around 70,000 ft). This is quite high for mach 0.5. Altitude at orbital speeds is more like 120 km (nearly 400,000 ft) --which yields low heating, as well as nearly neglible aero loads. - Greatly reduced chamber pressues (e.g., 1400 psi vs 3000 psi) leading to *much* longer engine life and reduced costs Why do you select the particular value's you select for chamber pressure? The baseline is an Aerojet AJ26/Kuznetsov Nk-33; we derate to 80 percent for greatly reduced maintenance costs. - Greatly reduced mass ratio: if we compare SSME (ground launch) with RL-10s, the MR reduces from 9.5 to between 6.5 and 7 --- a huge difference This mass ratio only counts if you forget the carrier and you find that you will have a greatly reduced total mass to orbit. The important paramater is cost, not gross mass. As for performance, orbiter mass ratio and staging point is what counts, not the mass ratio of earlier stages. - A much smaller minimum size vehicle: 80-100 tons versus 500-1000 tons I would say that slow airlaunch to a very high altitude has a very large advantage Debateable While you debate, we'll go to orbit--but only if we can manage to raise the funds necessary to develop the Space Van 2008. News groups are great. You can always count on a straight man. ;) Best (regards), Len (Cormier) PanAero, Inc. (change x to len) http://www.tour2space.com |
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