The "Real Aerospace" Thread

Discussion regarding the Outsider webcomic, science, technology and science fiction.

Moderator: Outsider Moderators

User avatar
icekatze
Posts: 1399
Joined: Sat Mar 05, 2011 8:35 pm
Location: Middle of Nowhere
Contact:

Re: The "Real Aerospace" Thread

Post by icekatze »

hi hi
Just because it looks like the spacecraft is travelling faster than light to someone on Earth, does not mean it is.
This is totally false. Its all relative. The speed of light is invariant in all reference frames, and things don't move faster than it in any reference frame, not just the reference frame of the traveler.

The reference frame of the traveler is not a privileged reference frame.

I'm not even talking about infinite mass, I'm talking about causality. Infinite mass is only one of many issues with FTL travel, and relativity absolutely enters into it. If it looks like it is going faster than the speed of light in any reference frame, then you can break causality.

User avatar
Mr.Tucker
Posts: 303
Joined: Tue Oct 29, 2013 4:45 pm

Re: The "Real Aerospace" Thread

Post by Mr.Tucker »

icekatze wrote:hi hi
Just because it looks like the spacecraft is travelling faster than light to someone on Earth, does not mean it is.
This is totally false. Its all relative. The speed of light is invariant in all reference frames, and things don't move faster than it in any reference frame, not just the reference frame of the traveler.

The reference frame of the traveler is not a privileged reference frame.

I'm not even talking about infinite mass, I'm talking about causality. Infinite mass is only one of many issues with FTL travel, and relativity absolutely enters into it. If it looks like it is going faster than the speed of light in any reference frame, then you can break causality.
I think you're looking at it from a wrong perspective. The speed of light is invariant in all reference frames LOCALLY, however it's arbitrary IN REFERENCE TO ANOTHER. What the drive does is, essentially, dissjoint the reference frame of the ship to that of the observer. Locally, nothing angers Mr. Einstein, but in reference to one another it's a different story. The drive separates a piece of space around the ship, and moves it (along with the craft). From the perspective of the observer, the craft disappears. Space moving at FTL speeds does not break causality, because space itself carries no information (see expansion of the universe). Matter carries information, and LOCALLY it stays bellow lightspeed.

User avatar
Arioch
Site Admin
Posts: 4486
Joined: Sat Mar 05, 2011 4:19 am
Location: San Jose, CA
Contact:

Re: The "Real Aerospace" Thread

Post by Arioch »

According to the Inflation Theory, spacetime itself expanded much faster than light in the first fraction of a second after the Big Bang. Though it was spacetime itself that was moving (and not objects relative to spacetime), surely at that moment things would have appeared to be moving away from each other faster than light (if we ignore the fact that everything was a superdense soup of energy and you couldn't see anything).

User avatar
icekatze
Posts: 1399
Joined: Sat Mar 05, 2011 8:35 pm
Location: Middle of Nowhere
Contact:

Re: The "Real Aerospace" Thread

Post by icekatze »

hi hi

No... it doesn't matter what perspective you are looking at it from. Massless particles and waves travel at c regardless of the motion of the source or the inertial frame of reference of the observer. The thing that changes between reference frames is not the speed of light but the passage of time. Simultaneity is observer dependent.

There is a painfully simple way to break causality with this method. All you need is two of these spacecraft. Using Bernard's star as an example:

• Spacecraft 1 leaves Sol, and from the frame of reference of the traveler, arrives at Bernard's Star instantly. Bernard's star is roughly 5.980 light years away from Sol.
• Bernard's star is traveling at roughly 142.7 km/s relative to Sol. A time dilation factor (y) of about 1.001135. y = 1 / Sqrt [ 1- (v2 / c2) ]
• Spacecraft 1 sends a message to Spacecraft 2. Spacecraft 2 is in orbit around Bernard's Star, at a similar relative velocity with the star compared to Sol.
• Spacecraft 2 travels back to Sol instantly, and arrives almost 2.48 days before Spacecraft 1 left. ((1.001135 * 5.980) - 5.980 = a difference of .0067873 years.)

The difference lessens depending on the speed that you travel, but increases with the distance you travel. And either way you slice it, if you go faster than light towards another object, from any reference frame, you can break causality.

(It is my understanding of expansion that the various parts of the universe in the early split seconds doesn't actually violate relativity due to the stretched nature of spacetime. And even though the velocity of receding galaxies is not real motion, it still has a very real effect on the waves traveling between them. As is shown with the red-shifting of photons. And because the recession is only moving away, not towards anything else, it further supports Consistency Protection. ie, a deterministic past.)

((Edit: They can also get up to incredible real velocity by falling towards a gravity well, then warping directly away and falling back down again. Repeating that process over an over, while picking up more velocity each time. Something that makes the time dilation factor even greater, and makes it a potential planet destroyer.))

Nemo
Posts: 277
Joined: Tue Apr 26, 2011 1:04 am

Re: The "Real Aerospace" Thread

Post by Nemo »

Arioch wrote:I think the implied promise in the recent "IXS Enterprise" NASA media campagin that a Star Trek-style starship is just a few years off is silly, embarrassing, improper, and likely to backfire in the long run in terms of rallying support around the space program. I think false promises and exaggerations hurt more than they help; people don't like it when you lie to them, and they remember it. However, I understand that the NASA people have to fight for funding, and I don't see anything more sinister in their (misguided) attempts to secure funding than just that.


Yes, yes this. We haven't even gotten an aeolipile equivalent built yet.
Image

User avatar
Mr.Tucker
Posts: 303
Joined: Tue Oct 29, 2013 4:45 pm

Re: The "Real Aerospace" Thread

Post by Mr.Tucker »

icekatze wrote:hi hi

No... it doesn't matter what perspective you are looking at it from. Massless particles and waves travel at c regardless of the motion of the source or the inertial frame of reference of the observer. The thing that changes between reference frames is not the speed of light but the passage of time. Simultaneity is observer dependent.

There is a painfully simple way to break causality with this method. All you need is two of these spacecraft. Using Bernard's star as an example:

• Spacecraft 1 leaves Sol, and from the frame of reference of the traveler, arrives at Bernard's Star instantly. Bernard's star is roughly 5.980 light years away from Sol.
• Bernard's star is traveling at roughly 142.7 km/s relative to Sol. A time dilation factor (y) of about 1.001135. y = 1 / Sqrt [ 1- (v2 / c2) ]
• Spacecraft 1 sends a message to Spacecraft 2. Spacecraft 2 is in orbit around Bernard's Star, at a similar relative velocity with the star compared to Sol.
• Spacecraft 2 travels back to Sol instantly, and arrives almost 2.48 days before Spacecraft 1 left. ((1.001135 * 5.980) - 5.980 = a difference of .0067873 years.)

The difference lessens depending on the speed that you travel, but increases with the distance you travel. And either way you slice it, if you go faster than light towards another object, from any reference frame, you can break causality.

(It is my understanding of expansion that the various parts of the universe in the early split seconds doesn't actually violate relativity due to the stretched nature of spacetime. And even though the velocity of receding galaxies is not real motion, it still has a very real effect on the waves traveling between them. As is shown with the red-shifting of photons. And because the recession is only moving away, not towards anything else, it further supports Consistency Protection. ie, a deterministic past.)

((Edit: They can also get up to incredible real velocity by falling towards a gravity well, then warping directly away and falling back down again. Repeating that process over an over, while picking up more velocity each time. Something that makes the time dilation factor even greater, and makes it a potential planet destroyer.))

Aha, now I see what you're getting at. Here's the thing about ALL warp drives: they depend upon general relativity, not special relativity. Special relativity applies to flat spacetime (Minkowski spacetime), but when one warps spacetime, general relativity is used. General relativity solves this conondrum through the use of something called closed causal loops, and actually allows for the existence of such systems. Whether or not they actually exist would depend on a theory of quantum gravity. Which we do not have. Alcubierre himself solved the matter in his original paper by causally disconnecting the interior of the bubble from the warp field. It may very well be impossible, however I still see no problem in trying to find out exactly why. Why would it be a sham to measure spacetime oscillations?

Now to answer your two examples:
1) You would need to match Barnard's Star's velocity BEFORE you engage the drive. At lest that's my understanding of it.
2)Once activated, it is my understanding that the bubble would carry the craft in the direction it was already heading. If one falls toward the gravity well, and engaged the drive, it would carry him further inside the well, not outside. One cannot jump back, or so it seems.

EDIT: And still no one seems interested in quantum vacuum plasma thrusters, which is a far more exciting and proven technology :( .

User avatar
NuclearIceCream
Posts: 81
Joined: Tue Feb 25, 2014 12:32 am

Re: The "Real Aerospace" Thread

Post by NuclearIceCream »

I was a actually interested in those things. Being able to get to get around the solar system with a drive than can pretty much be accelerating during most of the journey would be awesome.

User avatar
icekatze
Posts: 1399
Joined: Sat Mar 05, 2011 8:35 pm
Location: Middle of Nowhere
Contact:

Re: The "Real Aerospace" Thread

Post by icekatze »

hi hi

If spacecraft 1 matches Barnard's Star's velocity before it leaves, and spacecraft 2 has matched Sol's, it will still arrive about 2.48 days before spacecraft 1 left. And that's not taking into account any third bodies in the area. Spacecraft 2 could simply be flying by Barnard's Star at any arbitrary real velocity. Not to mention all the other bodies passing by, or in orbit of the star. Since the message between the two craft is transmitted through normal radio waves, there is no special interaction between the two required.

If the drive requires all objects within its historic light cone to be moving in the same reference frame, then its usefulness has immediately dropped to, "only the most stringently controlled laboratory settings."

It was my understanding that the drive moved in the direction it was pointed. Removing space in the front and producing space behind, without consideration of its real velocity. If that is not the case, it is still possible to tremendous real velocities through orbital maneuvers around extremely massive objects, which can now be approached in reasonable time periods.

I never said that it couldn't possibly happen. I remain extremely skeptical, but if they do pull it off, its going to change a lot of things in mind bogglingly big ways. Things besides just increasing the universal speed limit.

(Quantum vacuum plasma thrusters are neat, and I expect that if they do work as predicted, it will be interesting to see the effects on quantum states at extremely high time dilation. But since they don't involve time travel, I guess they're not as divisive.)

User avatar
Mjolnir
Posts: 452
Joined: Sat Mar 05, 2011 1:24 pm

Re: The "Real Aerospace" Thread

Post by Mjolnir »

discord wrote:my personal theory on the subject involves a likeness with the speed of sound, there are surprising amounts of similarities actually.
basically there is some kind of drag or something, that makes it very difficult to go faster, overcoming that and you go faster, pretty straight forward, how is another matter entirely though, because classic reaction engine just will not get the job done, something else is needed, just like proper wing and body shape was needed for supersonic flight, not just more power.
As icekatze said, there's only the most superficial of similarities. Supersonic speeds did only require more power, they could easily be achieved with guns and rockets. The only difficulty was practical supersonic aircraft. The problem with traveling faster than light is due to space and time being related in such a way that there is no logically inconsistent way to even speak of speeds greater than c. It is not a matter of "some kind of drag or something", there is no mysterious difficulty in acceleration to overcome, speeds just do not add to produce results greater than c. Time dilation and length contraction are observed facts, and combining them with travel faster than light would allow for violation of causality.

The Alcubierre drive still has a number of fundamental issues beyond its utterly enormous energy requirements, such as the need for FTL travel to produce and control the Alcubierre bubble and the violations of causality. And it does violate causality. That issue is independent of how long it takes for the travelers...not being subject to time dilation just means it takes more time to reach your past.

As for White's work, it's essentially a highly sensitive interferometry experiment attempting to measure the difference in curvature of spacetime due to the mass-energy of a capacitor when charged and uncharged. The effect would be extremely subtle, and so far attempts to measure it have failed, and there's a lot of skepticism about it being possible to measure at the scales being attempted. Nothing about the experiment points to a way of actually building a warp drive of any sort, any more than the Cavendish experiment pointed the way to gravity control.

User avatar
RedDwarfIV
Posts: 398
Joined: Sat Jan 25, 2014 12:22 am

Re: The "Real Aerospace" Thread

Post by RedDwarfIV »

Actually, the Supermarine Spitfire could have reached supersonic speeds if not for the fact that it's control surfaces were made useless at transonic velocities, as elevons would just get pushed flat. The Bell X-1 needed a movable horizontal stabiliser to reach supersonic speeds. Though that was a technology the RAF had flying on some planes years before the sound barrier attempts.

My point being that it wasn't just more power that was needed, but more control too.
If every cloud had a silver lining, there would be a lot more plane crashes.

Keter
Posts: 10
Joined: Thu Jan 30, 2014 7:42 am

Re: The "Real Aerospace" Thread

Post by Keter »

Mr.Tucker wrote:Now here's something I find really interesting (and scary; Star Trek got a lot of things right):

http://www.youtube.com/watch?v=9M8yht_ofHc
No credibility with anyone in the know. With any luck, Paul March is at Eagleworks Lab to rule out White's conjecture and eliminate it as distraction and/or regain White as investigator in Woodward's research.
discord wrote:sen: Alcubierre warp drive is probably not gonna work out as is, since his idea has power and material requirements that are just a tad bit extreme, but it points to it being theoretically possible.

and jives well with my 'idea' that something fundamental needs to change for it to work.
Alcubierre himself discredits the idea. See here:
https://twitter.com/malcubierre/status/ ... 0628078592
Nemo wrote:Dwarf, those are all solutions for technical challenges for a problem that doesn't yet exist. The way they're going about deriving that funding sends off alarm bells for me. If you want my buy in you must demonstrate a practical set of steps forward, focusing on the first small step in line. Its not a positive outlook, I'll freely admit, but whenever I see a pie in the sky promising tech being put forward that has this kind of end goal focus I immediately think money pit/scam.
That's what it is. White has no positive results so far from his interferometer experiments.

Suederwind
Posts: 772
Joined: Thu Jul 05, 2012 8:55 pm

Re: The "Real Aerospace" Thread

Post by Suederwind »

Not really sure if that fits here or in another thread.
Anyway, a nice little blog about various space project (from 1940 onwards till today), who created them, why they failed and many more:
http://falsesteps.wordpress.com/
Forum RP: Cydonia Rising
[RP]Cydonia Rising [IC]

User avatar
Arioch
Site Admin
Posts: 4486
Joined: Sat Mar 05, 2011 4:19 am
Location: San Jose, CA
Contact:

Re: The "Real Aerospace" Thread

Post by Arioch »

NASA has tested a quantum vacuum plasma thruster (a space thruster that requires electricity but no fuel), and verified that it does produce a consistent, measurable thrust.

http://www.extremetech.com/extreme/1873 ... ally-works

The drive uses particles created spontaneously by random quantum vacuum fluctuations and uses them as propellant. The thrust is very small, a tiny fraction of that of an ion drive, but as long as you have an energy source (such as solar panels), you can keep it up indefinitely.

User avatar
RedDwarfIV
Posts: 398
Joined: Sat Jan 25, 2014 12:22 am

Re: The "Real Aerospace" Thread

Post by RedDwarfIV »

That's the NASA testbed though. Apparently the thrust could be raised to 4 newtons per kilowatt. Meanwhile, a Hall Effect ion thruster requires 25 kilowatts for just 0.95 newtons of thrust.
If every cloud had a silver lining, there would be a lot more plane crashes.

Nemo
Posts: 277
Joined: Tue Apr 26, 2011 1:04 am

Re: The "Real Aerospace" Thread

Post by Nemo »

A little slow here, but back to the NASA QVPT test:
NASA Abstract wrote:Thrust was observed on both test articles, even though one of the test articles was designed with the expectation that it would not produce thrust. Specifically, one test article contained internal physical modifications that were designed to produce thrust, while the other did not (with the latter being referred to as the “null” test article).
If the experimental control delivers similar results to the experimental results my reaction isn't success. I start looking for a failure in my measuring stick.

User avatar
icekatze
Posts: 1399
Joined: Sat Mar 05, 2011 8:35 pm
Location: Middle of Nowhere
Contact:

Re: The "Real Aerospace" Thread

Post by icekatze »

hi hi

I suspect that the measured thrust is similar to the thrust observed in the Crookes Radiometer

Nemo
Posts: 277
Joined: Tue Apr 26, 2011 1:04 am

Re: The "Real Aerospace" Thread

Post by Nemo »

I would think the experiment took place in conditions closer to vacuum pressure, beyond the lower boundary where that method stops producing thrust.

User avatar
icekatze
Posts: 1399
Joined: Sat Mar 05, 2011 8:35 pm
Location: Middle of Nowhere
Contact:

Re: The "Real Aerospace" Thread

Post by icekatze »

hi hi
Testing was performed on a low-thrust torsion pendulum that is capable of detecting force at a single-digit
micronewton level, within a stainless steel vacuum chamber with the door closed but at ambient atmospheric
pressure.
Ambient atmospheric pressure does not sound like vacuum to me.

Nemo
Posts: 277
Joined: Tue Apr 26, 2011 1:04 am

Re: The "Real Aerospace" Thread

Post by Nemo »

What. The. Hell. They put it in a vacuum chamber and chose not to turn it on? I find myself agreeing on your idea. Are they intentionally fumbling tests to draw in funding now?

User avatar
icekatze
Posts: 1399
Joined: Sat Mar 05, 2011 8:35 pm
Location: Middle of Nowhere
Contact:

Re: The "Real Aerospace" Thread

Post by icekatze »

hi hi

Back when that vacuum tunnel train idea was being tossed around a friend of mine, who works with vacuum chambers on occasion, talked at length about all the different problems associated with creating a vacuum on Earth. I couldn't even repeat half of it with any accuracy, but from what I gather, once you start getting to really low pascal values, getting the pressure any lower becomes extremely difficult and energy intensive.

Attaining Ultra High Vacuum involves some rather outlandish strategies, like baking everything, then freezing it with liquid nitrogen. Then there's the problem with materials out-gassing at low pressures.

Post Reply