Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

What we know about the EmDrive and Cannae Drive

reddit.com

Post reply on HN
Print view View original

81–90 of 180 posts

Re: What we know about the EmDrive and Cannae Drive

#81

Post by kowdermeister »

Steuard wrote: post #4

This is not worth getting excited about. Really. Extraordinary claims require extraordinary evidence. These drives would violate conservation of momentum.[0] Conservation of momentum is built in to the known laws of physics at an extraordinarily deep level. It is obviously not impossible that our known laws are wrong, but the alternative would be to somehow produce a radically different set of physical laws that neve…

> Extraordinary claims require extraordinary evidence

So what do you call a second, replicated experimental setup conducted in vacuum, if not extraordinary?

Re: What we know about the EmDrive and Cannae Drive

#82

Post by pauloday »

drzaiusapelord wrote: post #79
MCRed wrote: post #56

I've some direct experience with a similar situation. I can speak to the issue of "why hasn't spaceX or other major company experimented with this". During the "Cold Fusion" era, when Pons & Fleishman had claimed to develop room temperature fusion, I worked for a major US lab doing superconductor research. (We invented the first superconductors that operated at liquid nitrogen temperatures-- Y1B2C3O) While fusion isn…

This is one of the many reasons why I consider all "fururist" media as just sci-fi wish fulfillment for kiddies. Its just incredible how unreadable /r/futurology is, for example. Its just a lot of pats on the back about some amazing life-changing technology, that is eternally 10 years away. I don't have access to the Mondo 2000 stuff today, but if any of that was to believed we'd have AI masterminded rockets to moon…

I love reading /r/futurology comments for comedy purposes, but I have a weird sense of humor

Re: What we know about the EmDrive and Cannae Drive

#83

Post by rntz »

mrfusion wrote: post #60
DennisP wrote: post #47

Earlier quoted context omitted.

Also conservation of energy. Thrust can't vary by velocity because there's no such thing as absolute velocity. So your velocity (relative to whatever) keeps increasing linearly, while kinetic energy increases quadratically. At some point you start getting more energy out than you put in. For some reason, this disturbs a lot of people more than violating conservation of momentum. The alternative is that there really i…

I'm not understanding this argument. Wouldn't the same amount of thrust get you less and less delta velocity as your velocity increases?

Not unless you're experiencing friction.

Re: What we know about the EmDrive and Cannae Drive

#84

Post by syncsynchalt »

Steuard wrote: post #38
pavlov wrote: post #16

Earlier quoted context omitted.

Are you serious? If you had the power, you would actively prevent NASA from doing these experiments and trying to falsify the claims? I could somehow understand that if the experiments cost a billion dollars. But they don't. Any Europa mission is in no way related to nor threatened by these drive tests.

Yes, actually. Every dollar that NASA spends has the potential to accomplish something for humanity. To my eye, even the vast potential benefits of this technology are more than washed out by the tremendously low probability that it will turn out to be real. I absolutely do not want NASA to give money to every person who comes to their door claiming to have a recipe for a warp drive. There has to be some threshold of…

Given the small amounts involved, it's worth the money just to figure out the source of experimental error. NASA isn't giving money to random kooks off the street, these are actual physicists in labs doing the work.

Re: What we know about the EmDrive and Cannae Drive

#85

Post by indrax »

mrfusion wrote: post #40

If (big IF) this turned out to be real, could we use these on helicopters instead of blades? Or are blades more efficient? Also would it make the hoverboard feasible, or does it require way too much energy?

Blades are much more efficient. I've done some back of the napkin estimates that this would levitate if paired with lockheed's supposed small fusion reactor. (and works at all, and if the drive reaches improvements that one paper thought possible, and if it scales with power input, and ....)

This inefficiency would still be great in space because you don't have to carry reaction mass with you. (and hovering on earth would mean sustained 1g acceleration in space, which is fantastic.) But if you're swimming through reaction mass anyway, then just push it as efficiently as possible.

Re: What we know about the EmDrive and Cannae Drive

#86

Post by raverbashing »

MCRed wrote: post #56

I've some direct experience with a similar situation. I can speak to the issue of "why hasn't spaceX or other major company experimented with this". During the "Cold Fusion" era, when Pons & Fleishman had claimed to develop room temperature fusion, I worked for a major US lab doing superconductor research. (We invented the first superconductors that operated at liquid nitrogen temperatures-- Y1B2C3O) While fusion isn…

> When you get to the fringes-- that's where the action is-- but it's also where you can have confusing or odd results.

I think this phrase sums it the best

I also usually remember that the Casimir effect, a tested and true effect, used to take a lab of experts some years to reproduce results

Re: What we know about the EmDrive and Cannae Drive

#87

Post by suprgeek »

MCRed wrote: post #56

I've some direct experience with a similar situation. I can speak to the issue of "why hasn't spaceX or other major company experimented with this". During the "Cold Fusion" era, when Pons & Fleishman had claimed to develop room temperature fusion, I worked for a major US lab doing superconductor research. (We invented the first superconductors that operated at liquid nitrogen temperatures-- Y1B2C3O) While fusion isn…

"arse technica" - Nice one!

Re: What we know about the EmDrive and Cannae Drive

#88

Post by scott_s »

InclinedPlane wrote: post #12
creamyhorror wrote: post #9

Earlier quoted context omitted.

According to physicist Harold White, leader of the NASA Eagleworks team, it can't simply be a "photon rocket": The NASASpaceflight.com group has given consideration to whether the experimental measurements of thrust force were the result of an artifact. Despite considerable effort within the NASASpaceflight.com forum to dismiss the reported thrust as an artifact, the EM Drive results have yet to be falsified. After c…

Realize that this is the exact same level of verification as superliminal neutrinos, except at a vastly decreased level of rigor. At this point the overwhelmingly likely explanation is that there is some phenomenon at work which we don't understand or haven't properly accounted for, not that there is new physics afoot.

I think that the most likely explanation is experimental error.

Re: What we know about the EmDrive and Cannae Drive

#89

Post by waterlesscloud »

syncsynchalt wrote: post #84
Steuard wrote: post #38

Earlier quoted context omitted.

Yes, actually. Every dollar that NASA spends has the potential to accomplish something for humanity. To my eye, even the vast potential benefits of this technology are more than washed out by the tremendously low probability that it will turn out to be real. I absolutely do not want NASA to give money to every person who comes to their door claiming to have a recipe for a warp drive. There has to be some threshold of…

Given the small amounts involved, it's worth the money just to figure out the source of experimental error. NASA isn't giving money to random kooks off the street, these are actual physicists in labs doing the work.

Not only is it not random kooks off the street, it's the Advanced Propulsion Physics Laboratory, a group NASA set up for the express purpose of exploring exotic and unlikely propulsion concepts.

They've done a small experiment on this particular concept and gotten interesting results. It would be utterly baffling if a group set up to explore such things explored them and then quit when they got interesting results.

Re: What we know about the EmDrive and Cannae Drive

#90

Post by Steuard »

3iak wrote: post #73
Steuard wrote: post #54

Earlier quoted context omitted.

Yes, it would be more precise if I had prepended "local" every time I said "conservation of momentum" above. With that clarification, I'm happy to stand by what I've said.

"local" seems like a fairly large assumption for something hypothesized by at least some to work through quantum mechanics, of which a central tenant is non-locality. In fact, given the consistency of qm experimental results over the past 50 or so years, it seems entirely plausible to think that it would be a field of study which could upend classical physics. All that being said I agree extreme skepticism is healthy…

I may have been using a technical term too glibly there.

Local conservation of momentum is a fundamental property of any translation-invariant model in the framework of quantum field theory. All this means is that the (vector) momentum flowing into any point in space-time must equal the momentum flowing out plus any increase in "stored" momentum at that point (whatever that might mean).

Quantum mechanics is a "local" theory in the formal sense, at least in any halfway mainstream formulation (from Copenhagen to many-worlds). Even the "spooky action at a distance" that folks talk about in reference to quantum phenomena is never capable of transmitting information outside of the "cone of causality" in space-time (which is the "light cone" in most relativistic theories: information can't travel faster than light).

Post reply on HN