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Author Topic: SCIENCE, Gravitational waves, and the whole LIGO OST!  (Read 512968 times)

Starver

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Re: SCIENCE, the Higgs, and everything else!
« Reply #285 on: January 28, 2013, 11:48:41 am »

Ninjaed

Even if it wasn't also prone to conveying adverse effects to the ship itself (which would probably work a lot better with a constant pressure than if it stressed by greated and lesser degrees), I'd be absolutely overjoyed with a (subjective) seven year round-trip to Alpha Centauri or a 28 year trip to the Andromeda Galaxy, in a 1g environment.

Cutting the journey times down to around four and a half years and (it appears) aroudn 14 years, respectively, doesn't sound very attractive when it means suffering 2g.  Having (say) one second of 5g every minute, on the top of a constant 1g is going to be unbearable (psychologically, if not physically and structurally) and not going to help much at all, although I've no idea where to start with that, save for averaging out the acceleration to 64/60ths of a g (1/15th above standard gravity) which, if smoothed, is hardly any advantage at all.


You can make the bursts more significant, but the intolerance (of psychology, physiology or engineering) to such bursts is going to be proportionally worse.


(Also, I think the technical problems of a constantly running 1g-accelerating engine, for those lengths of time is a hurdle, let alone one capable of t, five, ten times that for short periods of time, even if it's running for, say, half the number of years.)
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Sheb

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Re: SCIENCE, the Higgs, and everything else!
« Reply #286 on: January 28, 2013, 04:33:11 pm »

PTW.
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Siquo

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Re: SCIENCE, the Higgs, and everything else!
« Reply #287 on: January 29, 2013, 04:18:55 am »

Well, there's also the option of submersion in high-oxygen liquid (see http://en.wikipedia.org/wiki/Liquid_breathing), that could get us up to 20G, at least.
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Starver

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Re: SCIENCE, the Higgs, and everything else!
« Reply #288 on: January 29, 2013, 07:40:41 am »

First get me a high-g engine/ship setup, then we'll talk about being able to talk about taking advantage of that by buffering the crew's bodies against the force.  Personally I think the first attempts will be a more fractional g (minimum 1/6th, i.e. the moon, but preferably at least .5, and maybe as high as .75 if we can manage it?), trading off an expeditious expedition (at least from the crew's POV, although it also affects 'absolute' time as well) that needs more fuel/equivalent because it burns more quickly against one that can be more easily sustained (wear and tear on drive components, and ship structure) that needs more fuel because it's a longer pair of burns.

Without a concrete idea of the eventual drive parameters, I've no idea if there's a minima in the fuel/propellent use[1] that could influence that decision, or at least pull it one way or another (above or below 1g, which would be the absolute best for the crew asuming we weren't also wanting to acclimatise them to a higher-g landfall point, along the way), alongside possibly competing concerns about the structure of the station and the consumable supplies issue.

If it's something 'reactionless' (or refillable en-route, like the much vaunted Bussard Ramscoop of my youth) then perhaps slower acceleration[2] (or, at least, not quite so fast) is better because of the practical limits of power gain/through-put (and the margins and safety limits involved), rather than any other system.  Although "What if we had more and/or bigger engines?" could always apply, as long as they're not (barring the sought-after relativistic effects) reality-bending engines where putting too much power together this way causes 'problems'. ;)


[1] Of course a more fuel-saving solution would be to burn half (or quarter) of fuel, coast then slow down with the other half (or another quarter, leaving remaining half for return, if intended, and not optimistic about far-end harvesting of fuel/power-source).  But that'd not be a constant-g expedition, then, and would take longer and wouldn't reach the more relativistic speeds that we're contemplating making these a more 'livable' experience for the pioneers involved.  But I mention this so you don't think I've forgotten. ;)

[2] Or slower further acceleration once you've started to approach the relative speed at which the ramscoop best gathers and uses the interstellar whisps, because I can only imagine the effective extended collection-cone is going to be more acute at really high speeds...  Perhaps it'd be self-regulating, in that regard, and yet another aspect to the asymptotic barrier to speed that our ship must nudge against.  (But how would a Ramscoop decelerate?  Gather from (most of) the front 'cone' put redirect its energies back forward in a central spike of thrust?  Or used fuel gathered and stored from the initial phase?)
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10ebbor10

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Re: SCIENCE, the Higgs, and everything else!
« Reply #289 on: January 29, 2013, 01:14:08 pm »

Just as a note, but using some calculations I found on the internet (Ie, not very trustworthy), about half to 3/4 a year arceleration at +- 1 G would get you to a significicant fraction of lightspeed(70%, more or less)

(Actually, redoing those calculations: 1G = 9,81m/s²  c=299,792,458 m/s meaning that you need about 30*106. seconds or slightly under a year to get to 1 g. Do note that this doesn't incorporate any discrepancy caused by relativistic stuff.)

So, a 1g arceleration gravitational craft isn't really feasible, as the ship will be forced to coast, or break lightspeed. (Or more likely, encounter relativistic dynamics and start to slow it's arceleration automatically).
« Last Edit: January 29, 2013, 01:32:39 pm by 10ebbor10 »
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USEC_OFFICER

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Re: SCIENCE, the Higgs, and everything else!
« Reply #290 on: January 29, 2013, 01:27:26 pm »

Wait. What? A half year at 1G to get you to a fraction of 1G? Or is that a fraction of light speed?
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Re: SCIENCE, the Higgs, and everything else!
« Reply #291 on: January 29, 2013, 01:29:17 pm »

Sadly, it's microscale only; If we could make it larger, though...

It would go well with our impellor drives.

Basically, it's a paper from NASA's propulsion labs and talks about two things; one is the Alcubierre style warp drive that a few of you probably heard about (potentially insanely cool, but kind of needs some matter that has never been proven to exist).

The other is a propellant-less thruster that has experimental evidence backing it up AND could potentially one day lead to 35-day Earth-Jupiter transit times.

Yep.
That article mentioned experiments that push vacuum with common electromagnetic fields generating 0.1N/kW of thrust. That is 30 000 times higher than what you would get by firing a laser backward.

Maybe somebody here heard more than that article (that looks like a fund-rising presentation) and 2 internet-ready linked from it (that are on different subjects) and can answer the following questions.

What exactly is carrying away momentum in this type of propulsion? (I can understand dynamic Casimir effect but it in effect just creates photons and pushes with them similar to the case with a laser.)
Can this recoil "something" be detected? (Total momentum is still conserved, right?)
Since they were talking about QCD vacuum (and mentioned our current sorry state with theoretical estimates of vacuum energy density) - what in the frame of QCD transmits the force?
Are they assuming that everything in their setup is still Lorentz-invariant?
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10ebbor10

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Re: SCIENCE, the Higgs, and everything else!
« Reply #292 on: January 29, 2013, 01:32:16 pm »

Wait. What? A half year at 1G to get you to a fraction of 1G? Or is that a fraction of light speed?
Blurgh. Typo. Half a year arcelerating at one G should get you at about 50-60% of light speed.

Edit: @ above. If I'm reading it correctly (only skimmed it). They are planning to use the electromagnetic field to push away virtual particles. (Particles of matter + corresponding antimatter that spontanously materialize and within a fraction of a second obliterate themselves again. So yeah, the recoilenergy is most likely transposed to whatever caused the particles to exist, or to radiation.)
« Last Edit: January 29, 2013, 01:37:04 pm by 10ebbor10 »
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Re: SCIENCE, the Higgs, and everything else!
« Reply #293 on: January 29, 2013, 01:50:47 pm »

The problem is that if the recoil momentum is carried away by radiation - then it is radiation they are pushing themselves with and should not be principally different from just using a laser.
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10ebbor10

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Re: SCIENCE, the Higgs, and everything else!
« Reply #294 on: January 29, 2013, 01:55:48 pm »

The problem is that if the recoil momentum is carried away by radiation - then it is radiation they are pushing themselves with and should not be principally different from just using a laser.
Probably it isn't. I dunno (haven't really read the document). Maybe it's just way more efficient, as you don't need to provide power for a laser.
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RedKing

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Re: SCIENCE, the Higgs, and everything else!
« Reply #295 on: January 29, 2013, 02:05:35 pm »

Sadly, it's microscale only; If we could make it larger, though...

It would go well with our impellor drives.

Basically, it's a paper from NASA's propulsion labs and talks about two things; one is the Alcubierre style warp drive that a few of you probably heard about (potentially insanely cool, but kind of needs some matter that has never been proven to exist).

The other is a propellant-less thruster that has experimental evidence backing it up AND could potentially one day lead to 35-day Earth-Jupiter transit times.

Yep.
That article mentioned experiments that push vacuum with common electromagnetic fields generating 0.1N/kW of thrust. That is 30 000 times higher than what you would get by firing a laser backward.

Maybe somebody here heard more than that article (that looks like a fund-rising presentation) and 2 internet-ready linked from it (that are on different subjects) and can answer the following questions.

What exactly is carrying away momentum in this type of propulsion? (I can understand dynamic Casimir effect but it in effect just creates photons and pushes with them similar to the case with a laser.)
Can this recoil "something" be detected? (Total momentum is still conserved, right?)
Since they were talking about QCD vacuum (and mentioned our current sorry state with theoretical estimates of vacuum energy density) - what in the frame of QCD transmits the force?
Are they assuming that everything in their setup is still Lorentz-invariant?
Ger....bwaah? I just read through that NASA paper, and I need some Excedrin now. I grok the basic concept, but I'm kind of stunned that they're getting that level of result, and wondering how well it would actually scale up. I suppose if you have thousands and thousands of these tiny Q-thrusters mounted on an array plate it might work.

Based on their submarine analogy, there would be a "wake" but it would be in the form of....something? I don't understand virtual particles enough to say. If they blink out of existence every few nanoseconds, and you're getting your push from harnessing their oscillations, then I think the "wake" would essentially blink out of existence as well.

Pretty damn spiffy, if I'm processing that right. A form of thrust with no messy exhaust trail or recation mass to mess with. It's like the Chevy Volt of spacecraft.  :P


EDIT: Also interesting that it exceeds the stated performance characteristics of the controversial EmDrive that the Chinese have been working on. EmDrive prototypes have been reported to produce up to 300mN/kW, while the Q-thruster would appear to produce...400mN/kW? (based on the 4000μN/10W figure)
« Last Edit: January 29, 2013, 02:25:07 pm by RedKing »
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MonkeyHead

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Re: SCIENCE, the Higgs, and everything else!
« Reply #296 on: January 29, 2013, 02:10:56 pm »

The wake might blink in and out of existance until the oscillations are damped by some mechanism within the planck foam. You probably dont want to follow a craft making some kind of antimatter wake.

RedKing

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Re: SCIENCE, the Higgs, and everything else!
« Reply #297 on: January 29, 2013, 02:36:02 pm »

Well, if the drive itself disrupted the "blinking out" part, I think that would create Hawking radiation (which they describe in the paper as one of the virtual particles being deprived of its twin, which has become trapped in an event horizon).

Of course, I have no f'ing clue about half of what I'm talking about. I feel like a monkey trying to diassemble, clean and rebuild a carburetor with some twigs and leaves.
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Remember, knowledge is power. The power to make other people feel stupid.
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Science is like an inoculation against charlatans who would have you believe whatever it is they tell you.

MonkeyHead

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Re: SCIENCE, the Higgs, and everything else!
« Reply #298 on: January 29, 2013, 02:41:54 pm »

Yea, Hawking radiation kinda implies antimatter. Not nice exhaust material.

RedKing

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Re: SCIENCE, the Higgs, and everything else!
« Reply #299 on: January 29, 2013, 02:59:08 pm »

Yea, Hawking radiation kinda implies antimatter. Not nice exhaust material.
Well, but...Hawking radiation wouldn't annhilate matter, would it? (I guess the answer is "we'll know once we prove it exists...")
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Remember, knowledge is power. The power to make other people feel stupid.
Quote from: Neil DeGrasse Tyson
Science is like an inoculation against charlatans who would have you believe whatever it is they tell you.
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