Differences between revisions 11 and 12
Revision 11 as of 2017-10-27 19:37:54
Size: 5992
Revision 12 as of 2017-10-27 19:40:09
Size: 6011
Deletions are marked like this. Additions are marked like this.
Line 51: Line 51:
|| Airbus 380 || 576 tonnes || 275 km/h || 76 m/s || 1680 MJ || || Airbus 380 || 576 tonnes || 275 km/h || 76 m/s || 1680 MJ ||  9000 ft runway ||

Aircraft Launch with Launch Loop Transformer Track Technology

The following presumes good computer models and active control of thrust and cable tensioning. Computation is cheaper than extra structural strength added to an aircraft.

Military Fighter Launch

  • Note: I prefer peace to war, and defense to offense. Perhaps if defense is good enough compared to offense, war becomes unlikely. But people are insane, so I fear this will just add fuel to the hellish fire of hatred. Loop power requires a well-prepared fixed location, a source of electrical power, and is unlikely to be usable in occupied territory without months of construction. I welcome suggestions to make this even less likely to be used for offensive operations and invasions.

One of the first applications of loop technology may be the rapid burst launch of squadrons of military aircraft. Presume control distributed among the aircraft to separate them safely after launch, and to control them in the turbulent wake of their predecessors, so they can average one second spacing. In peacetime, this allows low cost training and quiet operation, less likely to upset civilian neighbors. It reduces pollution and fuel consumption. Green war? :-(

I was in the economy parking lot at Portland Airport (PDX) when a pair of F15 fighters (?) took off from runway 10L, then rotated and hit the afterburners overhead, seemingly flying straight up (though I don't think they have that much thrust). The noise was ear-splitting and bone rattling; when the noise and shaking died down, I could hear half-a-dozen car alarms blaring in the parking lot. I suppose pilots need training, but every noisy exercise like this shifts voters into the "cut the military budget, shut down the PDX Air Guard" voting block. A quiet way to launch training exercises, and a quick way to get an entire squadron airborne to altitude in a crisis, will promote a squadron's political and military survivability.

Assume a launch of 30 F-35A aircraft, one per second. WAG follows:

  • Takeoff mass: 30 tonnes
  • Maximum takeoff engine thrust: 100 kN (added to catapult thrust)
  • Takeoff acceleration: 20 m/s²
  • Takeoff speed: 120 m/s (much faster than carrier)
    • 50 m/s² 5 gee turn, 144 meter radius, about 2 seconds to straight up
    • Afterburners above 300 meters (far above ground) to continue climb

  • Loop catapult thrust 500 kN, total 600 kN
  • Takeoff time 6 seconds (and 6 vehicles in process)
  • Takeoff length 360 m
  • Unpowered abort length 640 m (including curved "waterbath" dispersal to avoid rear-end collision)
  • Takeoff energy = 216 MJ per aircraft (including engine power)
  • Takeoff energy from loop = 180 MJ per aircract
  • Takeoff energy for 30 aircraft = 5.4 GJ = 1500 kWh from the loop (about $200 of electrical input)
  • Average power during launch 180 MW

The aircraft may be connected to the sled with cables so they can be "flown like kites" after reaching takeoff speed. They can be hauled back down to the ground during an abort, with subsequent aircraft flying over the aborted aircraft.

Wikipedia: The EMALS 300-foot (91 m) LIM will accelerate a 100,000-pound (45,000 kg) aircraft to 130 kn (240 km/h; 150 mph), cites EDN 240 km/h is 66.7 m/s, in 91m is average 24.4 m/s², perhaps a peak of 30 m/s², kinetic energy of 200 MJ.

Launch loop version 1 assumes a 14km radius D magnet and 14 km/s, thus a radial acceleration of 14000 m/s². A 500 m radius power loop with 8,000 m/s² acceleration would move at 2000 m/s and store 2 MJ/kg. 3000 meters of 4 kg/m rotor stores 24 GJ. With a transformer track, this is more than enough energy to launch the 30 aircraft. With a 1 MW grid feed, loop energy could be restored in 90 minutes.

Commercial airport runway launch

If the loop takeoff assist system is available for war, it should be maintained for peaceful purposes 95% of the time. Commercial airliners are less noisy than fighters on afterburners, but perform many more takeoffs at most airports, angering civilian neighbors. Let's protect the neighbor's sleep from commercial takeoffs as well.

Here's some air transport takeoff masses and speeds:

Boeing 737

45 tonnes

250 km/h

69 m/s

108 MJ

Boeing 757

109 tonnes

260 km/h

72 m/s

284 MJ

Boeing 747

363 tonnes

290 km/h

81 m/s

1180 MJ

Airbus 380

576 tonnes

275 km/h

76 m/s

1680 MJ

9000 ft runway


181 tonnes

360 km/h

100 m/s

905 MJ

Per runway flight ops at big airports seem like one per minute, but might be 30 seconds apart? So, we might need power capacity for an occasional Airbus 380, but we will typically be launching about 1200 MJ per minute, or 20 MW of launch power, on average. A 24 GJ loop could easily launch a 1.7 GJ Airbus 380, getting that huge bird off the ground with as much thrust as the cable-anchoring hardpoints would allow. Presume that we attach to the aircraft at many points, and adjust the distribution of forces on the cables to minimize structural load; we could get it off the ground with much less than 10,000 feet of runway.

The Concorde is a special case. 100 m/s (on its small, overloaded undercarriage) created far more damage to its tires than normal aircraft. It may require both thrust and vertical support to reduce the tire stress. Landing after an aborted takeoff would put the full weight of the aircraft on the wheels, plus vertical acceleration. The Concorde's fatal accident (which doomed the SST concept) was a tire failure during takeoff. Sled-assisted launch probably won't help. The Concorde was a commercial and economic failure. While another high performance commercial passenger aircraft may succeed someday, it is probably beyond the planning needs of loop assisted launch.

AircraftLaunch (last edited 2017-10-27 19:45:18 by KeithLofstrom)