When it comes to space, we have a problem with our human desire to go everywhere and see everything. A huge problem. It’s space. It’s far too vast. Even at the maximum speed permitted by the Universe, it would take us years to reach our nearest neighboring star.
Another human drive is to find solutions to large problems. In his spare time, NASA engineer David Burns has been doing just that. He’s developed an engine concept that, he claims, can accelerate to 99 percent of the speed of light – all without the use of propellant.
He’s posted it to NASA’s Technical Reports Server under the title “Helical Engine,” and, on paper, it works by exploiting the way mass can change at relativistic speeds – those close to the speed of light in a vacuum. It has not yet been reviewed by an expert.
Understandably, this paper has generated buzz comparable to the early days of the EM Drive. And yes, even some headlines claiming the engine could ‘violate the laws of physics’.
While this concept is intriguing, it is unlikely to defy physics anytime soon.
Burns describes a box with a weight inside, threaded on a line, and a spring at each end bouncing the weight back and forth as a thought experiment to explain his concept. In a vacuum, such as space, this would wiggle the entire box, with the weight appearing to stand still, much like a gif stabilized around the weight.
Overall, the box would continue to wiggle in the same spot; however, if the weight’s mass increased only in one direction, it would generate a greater push in that direction, and thus thrust.
This should not be completely possible, according to the principle of momentum conservation, which states that the momentum of a system remains constant in the absence of any external forces.
But! There’s a special relativity loophole. Hooray for special relativity! According to special relativity, objects gain mass as they approach light speed. So, if the weight is replaced with ions and the box with a loop, the ions can theoretically move faster at one end of the loop and slower at the other.
Burns’ drive, however, is not a single closed loop. It’s helical, like a stretched out spring – hence “helical engine”.
“The engine accelerates ions confined in a loop to moderate relativistic speeds, and then varies their velocity to make slight changes to their mass. The engine then moves ions back and forth along the direction of travel to produce thrust,” he wrote in his abstract.
“The engine has no moving parts other than ions traveling in a vacuum line, trapped inside electric and magnetic fields.”
It sounds really cool, doesn’t it? And, in theory, it is. However, it is not without significant practical issues.
According to New Scientist, the helical chamber must be quite large. To be precise, it is 200 meters (656 feet) long and 12 meters (40 feet) in diameter.
It would also require 165 megawatts of energy to produce one newton of thrust. It takes a power station to generate the force required to accelerate a kilogram of mass per second squared. So much input for such a small output. It is extremely inefficient.
But in the vacuum of space? It just might work. “The engine itself would be able to get to 99 per cent the speed of light if you had enough time and power,” Burns told New Scientist.
And here’s something else. Humans – not all of us, but more than a few – are desperate to travel to interstellar space. We may never get there. But if we never even try to think about it, that “may” becomes a “definitely.” Isn’t it true that you miss 100% of the shots you don’t take?
You can check out Burns’ concept here.
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