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It occurs to me that an aeroplane that is catapulted off a runway via a maglev system would eliminate many current problems we face With aircraft travel. Firstly the runway could be as long as they are now - or shorter if that is better. Secondly a maglev system has unlimited and immediate torque. Any kind of takeoff speed could be provided up to about 500km per hour, perhaps even more. Thirdly, the thrust would be so massive that the engines would not have to be used at maximum thrust for takeoff - so reducing wear and tear, but more importantly aircraft noise and pollution at airports. Fourth, the aircraft wheels would have to be mounted onto maglev ‘Shoes’ which would be heavy of course - but they would return to takeoff position after each takeoff. Fifth, the amount of onboard fuel required would then also be much less, making the aircraft lighter as it climbed. Sixth, the noise levels in the airport would be much lower so eliminating much of the political opposition to new runways - and supporting the case for more night flights. Seventh, as the plane would be mounted on shoes on the maglev and runway distance would be much greater than for steam catapult takeoff the stresses on the aircraft would not be any greater than they are for current takeoffs - And there would no wheel friction/pollution. Finally, eighth, there is plenty of renewable power now available to power the maglev, so we could potentially cut aircraft fuel consumption by almost 30pc, while eliminating aircraft fuel pollution around airports by more than 50pc. I believe this use of maglev tech is the answer to our aircraft-based global warming concerns - and so could save the travel industry. Maglev is proven and reliable technology.

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  • $\begingroup$ I feel like there is a duplicate question around here somewhere. $\endgroup$ – dalearn May 2 at 0:19
  • $\begingroup$ Going through such trouble to save 20 seconds of fuel? $\endgroup$ – user3528438 May 2 at 0:26
  • $\begingroup$ "Thirdly, the thrust would be so massive that the engines would not have to be used at maximum thrust for takeoff" Most airliner take-offs are not done at "maximum thrust". $\endgroup$ – Ron Beyer May 2 at 1:05
  • $\begingroup$ This isn't a question. $\endgroup$ – Michael Hall May 2 at 1:13
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    $\begingroup$ This sounds like the musings of someone with just enough knowledge to think outside of the box. But, not enough to recommend feasible solutions. I applaud outside of the box thinking. But, this site is a question and answer forum for factual info. Not for a pro/cons discussion based on nothing but opinion. This question will probably be closed on this site. Might I suggest the world building stack exchange to flush out your argument first. $\endgroup$ – Dean F. May 2 at 1:44
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Although this might not be an answer to a question, there was no question here.

“It occurs to me that an aeroplane that is catapulted off a runway via a maglev system would eliminate many current problems we face With aircraft travel.”

What problems are we having with current airport facilities?

”Secondly a maglev system has unlimited and immediate torque.”

The maglev system you propose would not provide torque. It would provide force. And, not unlimited force. The more force you need, the bigger the mechanism required, the more money spent. A jetliner is different from a roller coaster car or even a fighter jet.

”Thirdly, the thrust would be so massive that the engines would not have to be used at maximum thrust for takeoff...”

Aircraft would need thrust or force to accelerate to rotation speed. Your system would provide that much. After that, the aircraft would still need to continue producing the same thrust it uses now to accelerate to maximum climb rate or maximum climb angle. A catapult system would stop producing thrust/force immediately upon the airplane leaving the ground. The only thing this would solve would be to shorten the distance necessary to reach rotation speed. For example, fighters leaving aircraft carriers still must use enough thrust to climb out.

”Fifth, the amount of onboard fuel required would then also be much less, making the aircraft lighter as it climbed.”

The difference in fuel consumption rate between takeoff trust with a catapult and takeoff thrust without one would be the same. Turbine engines have to have time to spool up. The aircraft would have to use takeoff/go around power prior to the start of being catapulted regardless. Look at fighter jets being launched from an aircraft carrier. If it were possible for the engines to go from completely off to climb thrust in one second, you would only save less than 60 seconds of fuel.

”Sixth, the noise levels in the airport would be much lower so eliminating much of the political opposition to new runways - and supporting the case for more night flights.”

When looking at aircraft carriers as an example, you would increase noise. This is because you would have to take the engines to takeoff thrust immediately before the launch. More time on the ground would be spent at the maximum noise level.

”Seventh, as the plane would be mounted on shoes on the maglev and runway distance would be much greater than for steam catapult takeoff the stresses on the aircraft would not be any greater than they are for current takeoffs”

???? The stress on the total airframe would not be any greater if you keep the acceleration distance the same. But, the stress would all be put on the front landing gear instead of the engine mounts that are already designed for it.

”Finally, eighth, there is plenty of renewable power now available to power the maglev, so we could potentially cut aircraft fuel consumption by almost 30pc, while eliminating aircraft fuel pollution around airports by more than 50pc.”

??? There is no where near enough renewable energy produced in this world. There is currently not enough renewable energy produced to power non-aviation activities. As mentioned in the above points, this would not decrease the fuel consumption either.

I applaud your out of the box thinking. Unfortunately, your target in this fight to decrease fuel consumption is way too small. You are targeting a phase of flight that takes up less than 60 seconds of flights that can last between one hour and twenty hours. What other benefit can your proposal have besides fuel consumption. Shortening of runways could be a benefit for new and future airports, but not for current ones.

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  • $\begingroup$ Thankyou for your response and informed critique. In response I would say this is not like short runway catapult. It is a long runway concept. Stresses are much lower and takeoff speed much higher. How much fuel would be saved if takeoff velocity was 500 km/hr on a commercial airliner? What would be the effect on the engine fans if the plane was being thrust forward by massive ground power? Also you say this would not reduce takeoff noise/pollution, but would it not be more like being fired by a gun - one that accelerates you over a mile or more? Also much wind power is still not stored. $\endgroup$ – Richard Gillespie May 2 at 7:35
  • $\begingroup$ If a bullet weighing 200 tons left the ground at 500 km/hr, what angle of ascent would be possible to achieve the highest point? Obviously the ailerons would have to be able to withstand the stress. $\endgroup$ – Richard Gillespie May 2 at 7:47
  • $\begingroup$ @RichardGillespie - It is less a physics problem and more a practicality problem. In the example of a 200 ton bullet, the gun would be fired at an angle. The greater the angle, the higher the max altitude. Angling the runway would not be practical. The only purpose for your catapult system would be to accelerate the aircraft prior to liftoff. An A380 would leave the ground at 150 knots and continue to accelerate to safely climb away from the ground at 190 knots. It would continue to accelerate to cruise at over 520 knots. These are flying speeds. Below 130 knots is stalling and falling speeds. $\endgroup$ – Dean F. May 2 at 13:08
  • $\begingroup$ @RichardGillespie - Your example of 270 knots (500 kmph) would achieve liftoff. But, the force of drag would decelerate the aircraft far faster than it would for your 200 ton bullet. The engines would have to provide takeoff and climb out thrust while leaving the catapult. Stress on the ailerons would not be a factor. Stress on the passengers would be. This would be from being thrown into the air in a non-linear, less than smooth fashion. Don’t underestimate passenger comfort in the commercial feasibility of this. $\endgroup$ – Dean F. May 2 at 13:24
  • $\begingroup$ @RichardGillespie - On the other end of the spectrum, a Cessna 172SP takes about 3-5 seconds for its engines to reach max horsepower. It takes less than 1000 feet of ground roll (on a good day on a hard surface with low density altitude) to reach the 55 knot speed necessary to rotate the nose to a 10° pitch up attitude. At full throttle, it would continue to accelerate to the 74 knot best rate of climb speed. If thrust is lost after rotation, it will decelerate under its 48 knot stall speed in a matter of 2 or 3 seconds. In a catapult, it would have to maintain full throttle from the ground up $\endgroup$ – Dean F. May 2 at 14:13

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