On Wednesday, January 16, 2013 11:28:47 AM UTC-6, Bill D wrote:
Just for fun, lets work out the numbers. With that much tension, probably not too much catenary arc (droop). Taking advantage of the low specific gravity of Spectra (it floats) conducting the launch over water should be considered with the ground roll on a near-shore runway and the winch on a ship 15 miles or so offshore. Think Dillingham Field in Hawaii. Presumably the rope tension will need to be equal to the glider weight as is the case with glider winches so 1/4" Spectra isn't going to do it. The German DAeC winch guidelines require a minimum of 150% the strength of the heaviest glider to be launched so the rope will need a breaking strength of no less than 1,275,000 Lbs-F. Consulting the Samson Rope "Amsteel Blue" catalog you will need 3 5/8" diameter rope. ________________________________ And engineers, how many h.p. winch to pull 245 tons? (Electric/Diesel locomotive engine?) ________________________________ We know the force in Lbs but we need the giant glider best climb speed (Vy) so assume 120 knots or 202 feet per second. A simple formula with give HP but overestimate since the rope speed will reach 202 FPS only at the beginning of the rotation phase but it helps estimate the peak HP required. One HP = speed in FPS times force in Lbs divided by 550 so 245 tons is 490,000 pounds times 202 FPS gives 98,980,000 divided by 550 = 179,964 HP. For most of the launch 'merely'100,000 or so HP would be enough if the ship based scheme scheme was used. If the ship were sailing away from the glider at the start of the launch, its kinetic energy would supply any "excess" HP needed at the start of the launch. So what engine could do that? The Wärtsilä-Sulzer RTA96-C could. http://en.wikipedia.org/wiki/W%C3%A4...Sulzer_RTA96-C I'll estimate the launch will take about 10 minutes so with a specific fuel consumption of .28 Lbs of per HP/Hr the launch would consume about 520 gallons of heavy bunker oil or about what a 747 uses taxiing to the runway. _________________________________ Still sounds more appealing than 747 wake turbulence. ________________________________ Indeed! So what could go wrong? You'd need a well thought out "launch abort" plan so the glider could always be landed back on the departure runway if the launch fails very similar to the Space Shuttle abort procedure. Most likely, it would not be necessary to jettison the payload in an emergency. Bill D

i think the coolest way to deal with a failed winch launch in this scenario would be to fire the rocket, with the glider attached. this would quickly get you the altitude needed to be able to easily make it back to a runway.