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The “helical engine” by David Burns
  • Description of the forecast
  • Description of the implementation
Designed by David Burns at NASA’s Marshall Space Flight Center in Alabama, the “helical engine” exploits mass-altering effects known to occur at near-light speed. Burns has posted a paper describing the concept to NASA’s technical reports server.

It has been met with scepticism from some quarters, but Burns believes his concept is worth pursuing. “I’m comfortable with throwing it out there,” he says. “If someone says it doesn’t work, I’ll be the first to say, it was worth a shot.”

To get to grips with the principle of Burns’s engine, picture a box on a frictionless surface. Inside that box is a rod, along which a ring can slide. If a spring inside the box gives the ring a push, the ring will slide along the rod one way while the box will recoil in the other. When the ring reaches the end of the box, it will bounce backwards, and the box’s recoil direction will switch too. This is action-reaction – also known as Newton’s third law of motion – and in normal circumstances, it restricts the box to wiggling back and forth.

But, Burns asks, what if the ring’s mass is much greater when it slides in one direction than the other? Then it would give the box a greater kick at one end than the other. Action would exceed reaction and the box would accelerate forwards.

This mass changing isn’t prohibited by physics. Einstein’s theory of special relativity says that objects gain mass as they are driven towards the speed of light, an effect that must be accounted for in particle accelerators. In fact, a simplistic implementation of Burns’s concept would be to replace the ring with a circular particle accelerator, in which ions are swiftly accelerated to relativistic speed during one stroke, and decelerated during the other.

But Burns thinks it would make more sense to ditch the box and rod and employ the particle accelerator for the lateral as well as the circular movement – in which case, the accelerator would need to be shaped like a helix.

It would also need to be big – some 200 metres long and 12 metres in diameter – and powerful, requiring 165 megawatts of power to generate just 1 newton of thrust, which is about the same force you use to type on a keyboard. For that reason, the engine would only be able to reach meaningful speeds in the frictionless environment of space. “The engine itself would be able to get to 99 per cent the speed of light if you had enough time and power,” says Burns.

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Source: New Scientists

According to Ethan Siegel (Ph.D. astrophysicist, author, and science communicator, who professes physics and astronomy at various colleges), the problem is that the idea of the "helical engine" relies on a fundamental misunderstanding of Special Relativity. It's true that when you accelerate an object close to the speed of light, the same acceleration (or thrust) will increase your speed by much smaller amounts the faster you're moving; Newton's second law of F = ma doesn't work, exactly, in Special Relativity. No object can ever move at the speed of light, and so as you continue to apply a force to a relativistic object, it's like you're increasing its mass, not just its speed. Different observers will disagree on the mass and speed of the object.

But if you instead write down Newton's second law as F = dp/dt, where p is momentum, this does work exactly (and equally for all observers), even in Special Relativity. If Burns had properly accounted for the total momentum of the box+ring system, which must include the energy/momentum of the applied fields and forces required to accelerate the individual components (like the ring) inside the box, he would have noted that the total momentum never changes, even under relativistic transformations and perfectly elastic ring/box collisions.

Instead, he examined the ring alone, and that's led to his math errors and his untenable conclusion. In fact, pre-existing fixed-target experiments at particle colliders have already demonstrated a conservation of momentum that serves as a counterexample to Burns' expectations. His idea is already dead-on-arrival.


Screenshot from Futrycon video on Youtube

David Burns

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David Burns has been named the manager of Marshall's Science and Technology Office. Burns joined Marshall in April 2016 after eight years with the U.S. Department of Defense Missile Defense Agency, where he served as the director of Science and Technology. He holds a doctorate in electrical engineering from the Air Force Institute of Technology, a master’s degree in electrical engineering from the University of Dayton, Ohio, and a bachelor’s degree in electrical engineering from the Air Force Academy.