Helical engine

Flyaway

Flyaway

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Sounds hugely inefficient at the very least.

www.newscientist.com

NASA engineer's 'helical engine' may violate the laws of physics

Rocket engines that don't need propellant have been proposed before: this is an illustration of the EM-drive For every action, there is a reaction: that is the principle on which all space rockets operate, blasting propellant in one direction to travel in the other. But one NASA engineer...
www.newscientist.com www.newscientist.com
 
Flyaway said:
Sounds hugely inefficient at the very least.
Click to expand...

Inefficiency covers a multitude of sins, this has a high energy input for the delivered thrust, but a low mass expenditure for the delivered thrust. Its mass efficiency varies with how fast you want to go. Probably very poor at lower speeds given all the infrastructure of power-plant and 200m drive you're hauling around, but improving rapidly as the ultimate speed grows, especially as you increase towards significant fractions of C. This isn't an engine for Earth orbit, it may not even be an engine for Earth to Mars, but for interstellar missions it's a potential competitor with Bussard ramjets etc. (If it works).
 
Here is a working link to Burns' original paper: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20190029294.pdf
Sorry, but it is garbage.
He accelerates his ions almost sideways but also slightly forwards, pointing out the net forward momentum gain on them after multiple cycles. But he quite forgets that all the while the equal and opposite reaction experienced by the accelerating magnets is not just sideways the other way but also slightly backwards, leading to an equal and opposite momentum change on the engine after those same multiple cycles. Net thrust after recovering the ion momentum at the far end: zero.
Like all these perpetual motion ideas, he buries the obvious in some dark technical corner hidden behind jargon-riddled smoke and mirrors.

I haven't looked that closely, but one effect which can be overlooked by the inexperienced is that at relativistic speeds, the particle rest mass ceases to be relevant. Its momentum is its velocity times its relativistic mass, not its rest mass. For example a force doubling its momentum might increase its velocity by only a few percent but would nearly double its relativistic mass. But it takes the same doubling of momentum, and the same accelerating force x time, as does a non-relativistic doubling of speed for constant mass. You do not get the relativistic mass increase without the accompanying reaction force. It may be that this is why he failed to notice the reaction in his analysis.

The absolutely one and only way to accelerate yourself in a Relativistic inertial reference frame is to exert a force on something external, even if you have to throw it out the back yourself.
 
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Snag it looks & sounds remarkably like the debunked EM Drive...

Worse, the efficiency is so low, you'd have to haul a lot of power supply and cooling system. Almost better to go for a photon rocket...
 
That latest piece is just referencing/recycling the New Scientist article which opens this thread. There is nothing new in it.

As I said above, the mistake is in assuming that there is no reaction to the force accelerating the increasingly massive ions: Relativity notwithstanding, whatever EM field you use to accelerate the ions will exert an equal and opposite backwards force on the field generator, so net thrust remains zero whatever internal speed they reach. It's a schoolkid error, just cunningly wrapped in classic perpetual-motion sleight of hand.

A case of "OK, so they rumbled the asymmetric microwave oscillator. Let's see if swapping the microwaves out for ions will make 'em weep." Nah, sorry bud. For propulsion your asymmetric accelerator has to be linear and let stuff out the back, you might as well try feeding your rocket exhaust into Reaction Engines' cryo heat exchanger and recirculating the propellant. But hey-y, maybe if I write that one up, NASA and New Scientist will put my name in lights too....
 
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DWG said:
Inefficiency covers a multitude of sins, this has a high energy input for the delivered thrust, but a low mass expenditure for the delivered thrust. Its mass efficiency varies with how fast you want to go. Probably very poor at lower speeds given all the infrastructure of power-plant and 200m drive you're hauling around, but improving rapidly as the ultimate speed grows, especially as you increase towards significant fractions of C. This isn't an engine for Earth orbit, it may not even be an engine for Earth to Mars, but for interstellar missions it's a potential competitor with Bussard ramjets etc. (If it works).
Click to expand...
Bussard Ramjets run into their drag limit at about 0.14cee. sadly. And since you need to kick them up to something over 0.08cee before they start, well...
 
The latest brighterside.news piece points to New Scientist's 2019 piece as a source. The NS piece can be found by following the link in this thread's post #1.
Further reading here and here.
 
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