DISQUS

enantiomer2000 · 1 year ago

that would be awesome. I wish them the best. I just came back from shenzhen and can just see the merchants offering to sell me a grav-thrust drive... tai gui le!

Snake_Oil_Baron · 1 year ago

While this aggravates every skeptical fiber in my... uh, skeptical fiber system, I am glad the work is being investigated. There seem to be a number of respectable people who feel this might be possible so at the very least, putting it to the test might provide some insight. Even if it doesn't work, coming to a better understanding of why it doesn't could prove useful.

And if it does work in a practical manner it would be big. Propulsion without propellant, even if it requires a lot of energy, could have many applications from below the sea to outer space. A robot machine or human vehicle with some manner of receiving energy from outside via lasers or resonance coils could fly around in a sensitive environment like an deep sea ecosystem or manufacturing space without kicking up turbulence. A lifting device which had no downdraft yet was not a slave to the air turbulence the way that lighter-than-air craft are could fill many niches in construction and other fields.

Will_Brown · 1 year ago

If I'm reading this at all correctly (as ever, not a given), then one of these Hyperion Power Modules ought to be sufficient for virtually any reasonable SSTO application short of a Pournelle/Niven novel. If that truly proves to be the case (and we ought to have a fairly definitive answer by next spring per Prof Yang), then a robotic mission to capture and deliver an asteroidal body to Earth orbit oughtn't not be too much further into the near-term future I should think. Something small to start, on the order of a cubic mile say.

Shirley it can't be this simple, can it? :)

nextbigfuture · 1 year ago

It seems that if it works as expected that lift from a 27 MWe power source would be about 81,000 tons. There would still need to be a secondary/hybrid propulsion but the cargo that could be delivered to space would be a lot more. Next year could be very interesting

pstudier · 1 year ago

In spite of their double talk about frames of reference, this still violates conservation of momentum. Draw a box around the system and ignore what is inside. Nothing comes out, except a little heat. Without some outlet for the momentum, there can be no thrust.

Perhaps there is some error in their measurements. Maybe when it warms up, there are convection currents.

Tom_Craver · 1 year ago

I agree - except we should keep in mind that conservation of momentum is a law derived from observation. There's a slim chance that since we've never observed a system this strange, it could be different. It's nearly certain that they've just missed something in their testing - but on the other hand, if no one did odd-ball experiments with results that give results that seem impossible under known laws/principles, we'd never learn anything new.

Another possibility is that the device works, just not the way they think - e.g. perhaps it's instantaneously accelerating electrons to nearly the speed of light, and they escape the system undetected.

I do wonder if there couldn't be some way, based on esoteric physics, to transfer momentum at a distance, without any apparent intervening medium. Would that be any stranger than some of the effects we see with entangled particles?

nextbigfuture · 1 year ago

From the emdrive FAQ, they say that no physical laws are broken.

Emdrive faq

Q. Does the theory of the EmDrive contravene the accepted laws of physics or electromagnetic theory?
A. The EmDrive does not violate any known law of physics. The basic laws that are applied in the theory of the EmDrive operation are as follows:

Newton’s laws are applied in the derivation of the basic static thrust equation (Equation 11 in the theory paper) and have also been demonstrated to apply to the EmDrive experimentally.

The law of conservation of momentum is the basis of Newtons laws and therefore applies to the EmDrive. It is satisfied both theoretically and experimentally.

The law of conservation of energy is the basis of the dynamic thrust equation which applies to the EmDrive under acceleration,(see Equation 16 in the theory paper).

The principles of electromagnetic theory are used to derive the basic design equations.
.
Q. Why does the EmDrive not contravene the conservation of momentum when it operates in free space?
A. The EmDrive cannot violate the conservation of momentum. The electromagnetic wave momentum is built up in the resonating cavity, and is transferred to the end walls upon reflection. The momentum gained by the EmDrive plus the momentum lost by the electromagnetic wave equals zero. The direction and acceleration that is measured, when the EmDrive is tested on a dynamic test rig, comply with Newtons laws and confirm that the law of conservation of momentum is satisfied.

Will_Brown · 1 year ago

Via Jerry Pournelle comes this purported refutation of the basic principle under consideration: ShawyerFraud.

Well beyond my intellectual ken, but much like the earlier Blacklight Power conundrum we merely have but to wait and see to find out for ourselves.

nextbigfuture · 1 year ago

Prof Yang and his group are not incompetent. He has done significant work for China's space program.
The Shawyer fraud paper claims that the force directions etc... are wrong, but Prof Yang has put this through computational analysis and any obvious"high school error" would have fallen out of that process.

They are running a test with a superconducting cavity that should generate newton level forces (not millinewtons).

It looks a million or two could be spent, and mostly on labor and equipment, so I do not see Shawyer getting rich off this unless it works.

I will be posting tonight on superconducting cavities with one billion -five billion Q. They are not that expensive or uncommon. They just need one with a custom shape and pay for operating costs of cooling it.

Maybe it won't work, but I am all for China spending a million or two on equipment and seeing what happens. With trillions being frittered away on wars and financial meltdowns, this is a serious cost/benefit bargain for civilization.

Will_Brown · 1 year ago

No disagreement from me, I just thought it better to include the theoretical challenge in the discussion and cite my source, that's all. Pournelle himself seems to echo my "wait and see" attitude, though he does provide some added historical background to the discussion that I found of interest.

No argument over who's money get's spent either, as long as they publish their results.

Stretching the whole blog-link concept, I updated my linked-to post on this topic (Thank you for that) with an analogy of this process to the magnetic force effect. Am I at all close? :)

RubberJesus · 10 months ago

I'm just concerned that if this does work the chinese government won't share this with the rest of the world