- NASA engineer introduces the helical engine that can take us to interstellar distances without refueling.
- With enough power and time, it would be able to attain 99% of the speed of light.
- The concept is quite bizarre but worth exploring.
Deep space travel is a trade-off between large propellant storage tanks and thrust. However, one NASA engineer believes that rockets could travel to stars without using ejecting any propellant from the engine.
David Burns, who is a manager of Marshall’s Science and Technology Office at NASA, has introduced a ‘helical engine’ that uses closed-cycle propellant. It can take us to interstellar distances without refueling.
Although many have expressed skepticism, Burns believes the concept is worth pursuing. It could be an intriguing testbed for exploring the relationship between the conservation of mass, force, and energy.
A Thought Experiment
To understand how Burn’s engine work, image a box resting on a frictionless surface. Inside that box is a heavy ring that slides on a rod. The ring can be pushed to one side using a mechanical spring.
Helical engine with the same mass
When the ring collides at one end of the box, it bounces back and the recoil direction of the box changes too. According to Newton’s Third Law of Motion, if the ring is pushed towards the right, the box will move left. The box won’t go anywhere but wiggle back and forth.
Now, image another situation where the mass of the ring is much higher when it slides at one end of the box. In this case, the box would get a greater kick at one end compared to the other. Thus, the box would accelerate in one particular direction.
Helical engine with relativistic masses
But is it possible to continuously change the mass of the ring? In theory, yes. According to Einstein’s special relativity theory, when an object approaches the speed of light, it gains mass. This effect is taken into account in particle accelerators.
Burns suggests that the ring inside the box could be replaced with a circular particle accelerator, which would accelerate the ions close to the speed of light during one stroke, and decelerate during another. To increase the system efficiency, it is necessary to employ a helix-shaped accelerator instead of a rod and box.
The accelerator needs to be big (approximately 650 feet long and 40 feet in diameter). To generate 1 N of thrust, it would consume 165 MW of power.
The engine would only be feasible in the frictionless environment (like space). As per Burns’ calculation, with enough power and time, the engine would be able to attain 99% of the speed of light.
An illustration of an EmDrive | Getty Images
This is not the first propellant-less design: many inventors have proposed interesting concepts since the early 1970s, but none of them has worked. The most popular of those designs was a rocket engine — named EM Drive — powered by electromagnetic waves.
Burns is very well aware of the fact that his design extremely inefficient. However, he believes that much of the energy can be harvested from heat and radiation emitted by the accelerator. It is also possible to conserve momentum, such as in the accelerated ions’ spin.
There are tons of technical challenges that must be addressed before building a practical engine. For example, it’s almost impossible to continually produce high current from heavier ions, using current technology. And most of the design parameters are limited by power, curvature, minimum ion velocity, and ion chemistry.