10 ms·
NASA Funded Scientists Claim Breakthrough in Propellantless Propulsion
- ForHackernews 6y agoSounds really bollocks to me. Seems like shades of the Emdrive: https://www.popularmechanics.com/science/a15323/temdrive-controversy/ https://www.popularmechanics.com/science/a15323/temdrive-con...
- z92 6y agoReminds me of the recent EmDrive hype, that didn't go anywhere.
- S_A_P 6y agoI see what you did there...
- commonjcb 6y agoNot this shit again... Look closely at the picture of the test chamber in the article. Do you see Helmholtz coils surrounding the entire apparatus? Nope. https://en.wikipedia.org/wiki/Helmholtz_coil https://en.wikipedia.org/wiki/Helmholtz_coil It's the same story as the EMdrive: they run something at high current, without cancelling earth's magnetic field. high current + earth magnetic field = force. This method is used to move satellites: https://en.wikipedia.org/wiki/Magnetorquer https://en.wikipedia.org/wiki/Magnetorquer
- imglorp 6y agoWouldn't you want to run tests in multiple orientations to cancel Earth fields anyway? Similar to how you would run a Michaelson-Morley interferometer experiment.
- commonjcb 6y agoThe torsion balance introduces fixed biases, and can be operated only in XY plane. So in theory you're right, in practice it's not possible. Not canceling earth's magnetic field (an easy thing to do) when measuring microNewtons at high currents is just very poor experimental practice. Unprofessional. Amateur.
- deleted 6y ago[deleted]
- marsokod 6y agoYou could but that may be a bit complicated to set up, while Helmholtz coils are dead easy to make and install. It's just a frame, copper wires, 3 power supplies, a magnetometer and a PC (even an Arduino could drive it).
- mdorazio 6y agoBe careful here. Magnetorquers do exactly what the name says - they create torque, which manifests as rotation around a point. If a device demonstrates linear force, it's likely to be a different effect (electrodynamic), which currently requires a rather long tether to work [1]. [1] https://en.wikipedia.org/wiki/Electrodynamic_tether https://en.wikipedia.org/wiki/Electrodynamic_tether
- commonjcb 6y agoRight, or we can just link to the physical law itself: - Lorentz force - the force on a current carrying wire. No need for a long wire. It's in the range of micro-Newtons for few Amps, for 10cm, at earth magnetic field: https://en.wikipedia.org/wiki/Lorentz_force#Force_on_a_current-carrying_wire https://en.wikipedia.org/wiki/Lorentz_force#Force_on_a_curre... "When a wire carrying an electric current is placed in a magnetic field, each of the moving charges, which comprise the current, experiences the Lorentz force, and together they can create a macroscopic force on the wire (sometimes called the Laplace force)."
- firebaze 6y agoI find it quite hard to believe that this obvious question wasn't challenged by anyone. To me it is like questioning if any of the people involved prior to publishing this news are capable of solving 1+1. It's basic. I don't think of the relevant people as idiots.
- mleonhard 6y agoA 2013 paper by Fearn & Woodward makes no mention of the earth's magnetic field. After skimming the paper, I think their experiment is flawed. "Experimental Null Test of a Mach Effect Thruster." https://arxiv.org/pdf/1301.6178.pdf https://arxiv.org/pdf/1301.6178.pdf "The motion of the beam is damped by a pair of aluminum plates attached to the beam that move in the magnetic field of an array of small neodymium-boron magnets. The power circuit was extensively shielded to insure that stray fields did not compromise the results."
- Aesthetys 6y agoI’ve never understood this position with the EMdrive and similar technologies; wouldn’t magnetic propulsion revolutionize low-earth-orbit travel, or whatever the ceiling is for pushing against Earth’s magnetic field?
- 0xUser 6y agoSo much hate in the comments. Have some hope, people.
- gameswithgo 6y agoit has all the signs, just like EM drive did, of being experimental error. that is just realism.
- alkonaut 6y agoDid the EMdrive have a solid understanding of why it would work, rather than just being a discovered curious effect? What's interesting about this one is that there is a theory at least. Experiments aside, someone whould be able to either confirm or reject the theory on its own.
- at_a_remove 6y agoThe EMdrive also had a "why." Note, if you investigate these sorts of devices, they typically have a why. It's just that the why tends to ignore a bunch of other things and it's a disappointment in the end. Really, if you're curious, you should dig into the history of all kinds of devices like these, anything in the Impossible Class. The inventor spends decades grinding away at it, getting inconsistent, odd little results which are just tantalizing enough to keep them stumbling forward. I have often considered a taxonomy of these sorts of enterprises, with three orthogonal systems of reckoning. The first, a type really, is what principle is being violated (Second Law of Thermodynamics, Newton's Third ...). The second is psychological: misunderstanding, self-deception, or duplicity (typically to bilk inventors), with the understanding that the inventor typically starts with misunderstanding and proceeds onward. The third would, finally, be the discovered actual source of the odd results, which could be bad experimental design, not accounting for oddly-radiating services, vibration, friction, and so forth.
- slowmovintarget 6y agoThis one relies on the premise that Einstein was right again. This is not unreasonable, especially given his track record.
- 0xUser 6y agoWiki: (...) Woodward states there is no violation of momentum conservation in Mach effects: If we produce a fluctuating mass in an object, we can, at least in principle, use it to produce a stationary force on the object, thereby producing a propulsive force thereon without having to expel propellant from the object. We simply push on the object when it is more massive, and pull back when it is less massive. The reaction forces during the two parts of the cycle will not be the same due to the mass fluctuation, so a time-averaged net force will be produced. This may seem to be a violation of momentum conservation. But the Lorentz invariance of the theory guarantees that no conservation law is broken. Local momentum conservation is preserved by the flux of momentum in the gravity field that is chiefly exchanged with the distant matter in the universe.
- icegreentea2 6y agoHow does Lorentz invariance guarantees that no conservation law is broken?
- mhh__ 6y agoI can't remember what the conserved current of LI is but symmetry implies a conservation law. (Noether's theorem)
- rweir 6y agoCould we all just wait until there's a (reviewed) paper in Nature or something?
- strombye 6y agoCrackpots usually don’t get published in Nature. This is crackpot stuff.
- jp555 6y agoThis sounds, like the EM drive, too much like trying to move your car by sitting inside and pushing on the dashboard.... Still, a "vacuum propeller" would be a massive revolution (no pun intended) if it is at all possible.
- at_a_remove 6y agoIt is because the payoffs would be so enormous that business like this and "overunity motors" continue to gain attention. All of those other elixirs were shams, but this one will work! Finally, immortality! The enormity of the reward causes the payout matrix to lead people astray. Don't get me wrong, I see a vacuum chamber, which is light years ahead of most of these enterprises, but I would not spend a dime on it until it has been proven to work in a region of space relatively far from the Earth's magnetic field.
- roywiggins 6y agoIt's a kind of Pascal's mugging, I think. https://en.m.wikipedia.org/wiki/Pascal%27s_mugging https://en.m.wikipedia.org/wiki/Pascal%27s_mugging That said, Woodward does not seem to be an actual charlatan, so I don't have a problem with funding him. At least he might turn up something fun and/or interesting, even if I don't think it's going to usher in a new space age.
- shadowgovt 6y agoI personally believe he rides that line of charlatanism where he's not pursuing this theory in bad faith at all, but he of course recognizes that tromping around on the edge of a theoretical branch that most physicists don't think is worth exploring garners attention he wouldn't otherwise receive. I strongly suspect that whether history remembers him as a charlatan will depend heavily on whether one of the supports of his branch proves false and it snaps off, or whether he's been right this whole time and we suddenly oops ourselves a propellantless drive that operates by coupling to the gravitational field and pushing distant objects around. ;)
- jccooper 6y ago
- mikeknoop 6y agoHere’s the paper: https://www.researchgate.net/publication/280134421_New_Theoretical_Results_for_the_Mach_Effect_Thruster https://www.researchgate.net/publication/280134421_New_Theor...
- beepy 6y agoFrom the article: > Mike McDonald, an aerospace engineer at the Naval Research Laboratory in Maryland, will be among the first [attempt to replicate their results]. He leads an internal program for independently testing advanced propulsion systems, which has previously shot down promising results from the EmDrive.
- leephillips 6y agoThere might be such a place, although it’s more likely they’re trying to refer to the U.S. Naval Research Laboratory in Washington, DC.
- snowwrestler 6y ago> On a clear night in March 1967, Woodward was stargazing on the rooftop of Pensión Santa Cruz, a hotel in the heart of Seville, in Spain.... As Woodward gazed up from atop his Spanish hotel, he saw a speck of light arcing across the sky and mentally calculated its path. But as he watched the satellite, it began deviating from its expected trajectory—first by a little and then by a lot. > Everything Woodward knew about satellites told him that what he was seeing should be impossible. It would take too much energy for a satellite to change its orbit like that, and most satellites weren’t able to shift more than a couple of degrees. And yet, he had just seen a satellite double back with his own eyes. He didn't conclude that engineers at NASA or in the Soviet Union must have secretly achieved a breakthrough in satellite propulsion. Instead, he believes he saw a spacecraft of extraterrestrial origin. Seems more likely he spotted a reconnaissance aircraft at very high altitude. I think the U2, A-12, and SR-71 were all operational in 1967.
- sgt101 6y agoOr a bird. Less high up, nice white tummy, reflects the light.
- nkoren 6y agoDo you honestly think that somebody trained in astronomy could mistake a bird for satellite? Have you seen how satellites move? They traverse the sky in a perfectly straight and constant-motion fashion that is utterly unlike any bird. Even a high-altitude plane such as the U-2 would be fairly difficult to misidentify as a satellite. For obvious reasons, U-2s and SR-71s and such didn't employ lights while operating at altitude; therefore the only way to see them would be via reflected light. It would need to be reasonably long after sunset, or else the sky isn't dark enough to credibly see a satellite -- but not so long after sunset that the plane would be in the earth's shadow. Satellites have a similar window of observability -- but it's much longer, because they're much higher. A high-altitude plane would have a very small window. Moreover, it would need to execute that turn without crossing the terminator: as soon as any reflecting object crosses the terminator, that reveals its altitude.
- 6y ago
- gintoddic 6y agoIt's really disappointing that a human can work on something for 30 years and only get a tiny amount of thrust. Our science needs to go in different directions it seems we are stuck living in the past.
- sebringj 6y agoInteresting caveat about traveling close to the speed of light...if you run into hydrogen atoms, which is near 100% likely, your ship violently explodes because at very high speeds, there is a huge reaction on tiny matter collisions. I just learned this and it was like learning that sound doesn't travel in space when I was young and ruined many a starwars movie effects. I keep learning how ignorant and dumb I am the more I follow SpaceX and become curious about space.
- kaiju0 6y agoInterstellar ships will be shaped like pencils to deflect rather than impact gasses. They will also have to have consumable nose cone sections with old ones in the front being removed and new ones installed at that back. Like a mechanical pencil.
- pluto9 6y agoWhat happens when the ship has to turn around to decelerate, with its engines facing the front?
- undersuit 6y agoTurn on the drives as soon as you can for the deceleration burn and pray.
- mrob 6y agoThe only realistic option is another set of engines on the other end.
- pmayrgundter 6y agoZubrin, in Entering Space, introduced me to the idea of using a solar or much larger magnetic sail to drag against the outcoming solar wind of the destination star. So that's one way to spend no energy slowing down for interstellar travel.
- mleonhard 6y agoThe turn-around takes place at the half-way point of the journey. This means that for the entire second half of the journey, the engine is pointed at the oncoming dust. Engines used in such long journeys will likely emit a thin stream of particles at extreme velocities. This stream is not wide enough or thick enough to stop space dust from hitting the engine. An unshielded forward-facing engine will get destroyed. So we must shield the engine. Instead of having two shields and turning the ship around, just turn the engine around. Make the engine emit streams forward from the sides of the ship.
- roywiggins 6y agoIt's worth noting that if a propellentless drive works, it will probably generate free energy. This may adjust your expectations on how likely this idea is. How likely is a free energy device (ie, one that reliably gives you more energy out than you put in)? Well, this thruster can't be any more likely, because it would produce free energy. https://arxiv.org/abs/1506.00494 https://arxiv.org/abs/1506.00494 > the kinetic energy of a mass with a constant force applied will increase with the square of time, while the electrical energy input only increases linearly with time. A mass with such a drive attached would eventually have a kinetic energy greater than the energy input. ... > For example, an evacuated track 10km long and supplied with 1 GW of power that is fed via induction along the track to a 100 kg mass equipped with an EM drive would result in the mass experiencing an acceleration of 4000 m/s2(i.e., 407 g’s) and having a velocity of 8.94 km/s at the end of the track, at which point the mass would have a kinetic energy of 4 GJ. The time to accelerate the mass is only 2.23 seconds,however, so the energy input required is only 2.23 GJ. At the end of the track, the mass could be decelerated via regenerative braking, generating more energy out (4 GJ) than was input (2.23 GJ), for a net gain of 1.76 GJ free energy.
- shadowgovt 6y agoNot precisely free; it moves energy around(1) by interacting with the inertial mass of other objects in the galaxy and applying force to them at a distance (the details of how, which objects, and how much force, at least in the Wikipedia summary, are really sparse). In theory, if we could run an unbreakable string from Earth to Mars and twist it around a spindle, the differing orbits of Earth and Mars would pull that string taut and that string yanking the spindle around would generate energy that wasn't "free," but (like solar) would be free for all practical purposes. Do too much of it, and Mars crashes into Earth of course, but there's a LOT of energy that could be siphoned off from the planets' different velocities before something like that happened. It's the same kind of "free" spacecraft get making a gravity-assist maneuver; they slow (or speed up) the orbit of the body they're assisting off of imperceptibly. (1) ... of course hypothetically. The details of the mechanism are not well-understood and appear mostly theoretical.
- PaulAJ 6y ago> [..] while the electrical energy input only increases linearly with time. This is the fallacy. In an electric motor the power required to exert a force is proportional to the speed, so if you want to keep the acceleration constant you need to increase the electrical power (i.e. rate of energy use) linearly over time. Hence the total energy input increases with the square of the time, just like the kinetic energy imparted. If the system is 100% efficient then the total electrical energy used will be equal to the kinetic energy of the mass.
- PaulHoule 6y agoSee https://en.wikipedia.org/wiki/Dean_drive https://en.wikipedia.org/wiki/Dean_drive particularly this article http://www.rexresearch.com/dean/stine.htm http://www.rexresearch.com/dean/stine.htm
- deleted 6y ago[deleted]
- motohagiography 6y agoSo, I have to ask: If Elon Musk is working on propulsion tech to go to Mars, and Bob Lazar claims to have worked on reverse engineering propellentless tech and is one of the single digit number of living people to have encountered it directly, and NASA is slow rolling their own understanding of it, given the limited available expertise in this area how can Musk afford to not hire Lazar? From a due diligence perspective, Musk would need to know with a high degree of certainty that Lazar is full of crap. While this might sound insane, from a portfolio perspective, if a VC firm is invested in SpaceX, Blue Origin, Virgin Galactic, or anyone else in the space, it seems negligent to not have some exposure to a company with someone like Lazar involved in it, unless you really knew for sure, as he and people like him present an existential risk to rocket-based tech companies. That guy is the ultimate hedge.
- xibalba 6y ago> know with a high degree of certainty that Lazar is full of crap This is your answer. Extraordinary claims require extraordinary proof, and Lazar can't ever seem to manage the latter.
- motohagiography 6y agoI'd agree, but if we're trading tropes, the absence of evidence is not evidence of absence either. He's easy to discredit and dismiss, and it's meaningless to my life whether he's real or not, but if you've got billions on the line in the space propulsion game, I'd think you'd need to have gone deep into his claims to determine he's full of it.
- carry_bit 6y agoIf he wasn't full of crap, then you also running the risk of the government/some other group not wanting the tech out there and then preventing the success of your investment.
- boxed 6y agoYour logic assumes only one such person. The problem is that there are tens of thousands of similar people with, let's be super kind, unlikely ideas. If you hire them all that's not a hedge that's a huge cost with an almost 0% probability of payoff. I'd bet the number of such people with unreasonable ideas will go drastically up if you start hiring them too.
- mnw21cam 6y agoSo, https://xkcd.com/955/ https://xkcd.com/955/ appears to be relevant. If someone were to take it, I'd make a bet that this is not real. If it is not real, then I win the bet, but if it is real, then I'd be too fascinated by the result to care.
- njarboe 6y agoOne should note that propellantless propulsion systems exist. They are called lasers. It is just that the thrust to weight ratio of such an engine is very low. A quick google search does not bring back any designs or research papers of such a system, as the results are swamped by the idea of using ground based lasers to push spacecraft instead of the craft itself containing the laser.
- nojokes 6y agoI would like to see more pictures of his desk. I adore such setups.
- qayxc 6y agoI'm more curious to learn why the image on the monitor shows a screenshot instead of an actual desktop or open program(s).
- mcswell 6y agoNit: "as Newton put it, inertia is why an object at rest tends to stay at rest." No, what Newton said is that an object in motion tends to continue in motion at the same velocity (and an object at rest tends to remain at rest, i.e. with velocity=0). While this doesn't have a lot to do with the original article (hence my "nit"), it was revolutionary at Newton's time. People had observed objects at rest staying there; that's why you can sit on a chair. But they had also observed that any object in motion (except for those in the sky) slowed down and eventually stopped, unless you kept pushing them. Newton attributed this to friction. This theory--which contradicted what people could plainly observe with their eyes--is what makes possible satellites (and keeps the moon in orbit), since being outside the atmosphere, they experience very little friction. Of course the other thing necessary for man-made satellites is a way to get them moving fast enough, for which Newton's third law comes in handy (it's why rockets accelerate, even outside the atmosphere).