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

Questions about Nasa's space drive answered

wired.co.uk

Post reply on HN
Print view View original

141–150 of 205 posts

Re: Questions about Nasa's space drive answered

#141

Post by Gravityloss »

The most important question that should have been top center: with reactionless propulsion it is possible to create a free energy device.

Attach the thruster to a wheel.

When the thruster is firing, it consumes constant power and the wheel accelerates, spinning ever faster.

The wheel can be attached to a generator that produces power which is thrust times the rim velocity.

Thus, after a certain speed, the wheel produces more power than the thruster consumes.

This was discussed on a rocketry list.

Re: Questions about Nasa's space drive answered

#143

Post by jcfrei »

mnl wrote: post #120
tobinfricke wrote: post #41

Here are two nice posts by physicist John Baez with some reasons to be skeptical about the "reactionless drive": https://plus.google.com/117663015413546257905/posts/WfFtJ8bY... https://plus.google.com/117663015413546257905/posts/C7vx2G85...

I'd never understand how intelligent and educated people lose it completely when it comes to Physics. They've been exposed to some PopSci tales not meant to be accurate at all and then feel entitled to be right when they figure out some nonsensical consequences by themselves -no proper maths involved ever-. It's depressing. Baez is right, of course. I've been checking the (Word-generated) "papers" from this guy's gro…

The issues raised by Baez are quite substantial. I'm surprised the report was still published by NASA.

Re: Questions about Nasa's space drive answered

#144

Post by bellerocky »

Gravityloss wrote: post #141

The most important question that should have been top center: with reactionless propulsion it is possible to create a free energy device. Attach the thruster to a wheel. When the thruster is firing, it consumes constant power and the wheel accelerates, spinning ever faster. The wheel can be attached to a generator that produces power which is thrust times the rim velocity. Thus, after a certain speed, the wheel produ…

And where would the "free energy" be coming from? Pretty sure you'd be losing energy, as energy doesn't come from thin air.

Re: Questions about Nasa's space drive answered

#145

Post by VikingCoder »

Gravityloss wrote: post #141

The most important question that should have been top center: with reactionless propulsion it is possible to create a free energy device. Attach the thruster to a wheel. When the thruster is firing, it consumes constant power and the wheel accelerates, spinning ever faster. The wheel can be attached to a generator that produces power which is thrust times the rim velocity. Thus, after a certain speed, the wheel produ…

At least one of the theories on the article talked about pushing on virtual particles, like a submarine pushing on the water around it. This would imply to me that efficiency goes down with speed. Just a thought.

Re: Questions about Nasa's space drive answered

#146

Post by ghshephard »

Gravityloss wrote: post #141

The most important question that should have been top center: with reactionless propulsion it is possible to create a free energy device. Attach the thruster to a wheel. When the thruster is firing, it consumes constant power and the wheel accelerates, spinning ever faster. The wheel can be attached to a generator that produces power which is thrust times the rim velocity. Thus, after a certain speed, the wheel produ…

I"m not following why you think the wheel generator will produce more power than is required to spin the wheel in the first place. Friction is a pretty big issue in your scenario. It seems orthogonal to the actual results.

Re: Questions about Nasa's space drive answered

#147

Post by crusso »

tensor wrote: post #131
crusso wrote: post #122

Doesn't this remind anyone of the not-so-long-ago overhyped E-Cat? http://en.wikipedia.org/wiki/Energy_Catalyzer

Not at all. Unlike the e-cat, the design here is clear and it sounds like it's independently verified from the ground up with good experimental conditions. The e-cat had "secrets" that they wouldn't divulge and it's tests were also questionable with the machine being plugged into a power source the whole time.

"verified from the ground up with good experimental conditions"

No it hasn't. That's the hype. Read the Baez commentary referenced elsewhere. Research all the other physics breaking phenomenon that had experimental confirmation but were still shown to be wrong.

It's not like this effect was just noticed yesterday. You'd think that for an effect that Shaw created a company for in 2000, we'd have solid experimental results by now that addressed every single problem.

It mostly reminds me of the E-Cat in that there are people who want it to be true so badly that they cherry pick the results and statements that they want to believe while disregarding contraindications.

Re: Questions about Nasa's space drive answered

#148

Post by chton »

gus_massa wrote: post #101
chton wrote: post #87

Earlier quoted context omitted.

While it's true that most reactionless drives break some of the most basic physical laws, that's not the case for all of them. An Alcubierre drive is a good example of a propulsion method that works within the current laws, yet does not emit anything. The idea that the designs they tested (and EmDrive) would be reactionless is exactly why everybody is so baffled and excited by this. If they are, they must have some w…

Alcubierre drive is not a thruster, you can't attach it to a spaceship to move it. It's something like: "If you put a spaceship inside this, and it stabilizes the gravity field using that, then it will travel faster than light in an external reference frame." It travels at a constant speed, so it doesn't need to emit particles to change the momentum. (On the other side, it uses exotic matter that no one has ever seen…

In an Alcubierre drive the total system does accelerate forward. The spaceship itself won't, but the total system ('bubble', contents and ship together) will increase in momentum to an outside observer. I agree that it may be impossible to construct, but it's theoretically possible.

According to the experiments, the drive seems reactionless so far. It's possible that it does emit something that we can not measure, it's also possible that it transfers momentum to something else, or that it works on something else entirely. We simply don't know yet. There is potential here, if there does turn out to be experimental evidence for it being truly reactionless, for that to require an addition to physics. Even if the evidence turns up something else, it'll at least be interesting.

I agree that there are a lot of ifs, ors and buts. That's why everybody is calling for independent confirmation. Just like the neutrino case, that's how science is supposed to work. But any potential for expanding our understanding should be given proper attention and enthusiasm.

Re: Questions about Nasa's space drive answered

#149

Post by smellf »

jliechti1 wrote: post #112
gus_massa wrote: post #101

Earlier quoted context omitted.

Alcubierre drive is not a thruster, you can't attach it to a spaceship to move it. It's something like: "If you put a spaceship inside this, and it stabilizes the gravity field using that, then it will travel faster than light in an external reference frame." It travels at a constant speed, so it doesn't need to emit particles to change the momentum. (On the other side, it uses exotic matter that no one has ever seen…

I asked a particle physicist to compare the validity of this to the faster than light neutrino claim that came up and his response was: "Although several people are drawing that comparison, they're really not in the same class. OPERA did an extremely thorough analysis of the faster than light neutrino result before they published. In the end it turned out to be a very subtle experimental error that cause the problems…

But there's three independent labs working on this concept, plus NASA. _Who_ is lying, the EmDrive folks? And if they are, then how are NASA, the Chinese and the other lab all replicating their results?

Re: Questions about Nasa's space drive answered

#150

Post by MiguelHudnandez »

JulianMorrison wrote: post #102

A superconducting version of the EmDrive, would, in principle, generate thousands of times more thrust. And because it does not require energy just to hold things up (just as a chair does not require power to keep you off the ground), in theory you could have a hoverboard which does not require energy to float in the air. If they have just solved flying cars and hoverboards, I think we can officially declare this to…

> And because it does not require energy just to hold things up (just as a chair does not require power to keep you off the ground), in theory you could have a hoverboard which does not require energy to float in the air.

An item where you could dump electricity into it once, cut power, and have it resist gravity -- forever, and for free! -- is absolute horse shit.

Post reply on HN