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Phobos
2002-Jun-02, 02:04 PM
Whilst considering the current ideas floating around regarding lifter technology, a thought came to mind, which I would like to air on this board for those, interested.

Unlike jet aircraft, spacecraft are currently designed to carry and deliver their own propellant. This is because whilst aircraft can "push" against the surrounding air, spacecraft work in the vacuum of space and seem to have nothing to "push" against.

Once a spacecraft runs out of propellant it looses it's ability to manoeuvre and then generally looses most of its usefulness.

Quantum physics has given us a new understanding of what makes up the vacuum of space. Rather than being "empty", it is constantly being populated with temporary particles that owe their existence to the creative and destructive influence of the energy contained within the vacuum (zero point energy).

Since the vacuum of space contains temporary particles, I have started wondering if we could start designing propulsion systems that take advantage of our new understanding of the environment that the spacecraft are operating in.

My idea is that we design a thruster that exerts a force on these temporary particles instead of using onboard propellant. If possible such a design would in effect have a limitless supply of propellant.

OK so that’s the idea, I suppose there is probably some simple reason why it may not be possible to achieve thrust using this method but at the moment the idea seems sound - have I missed something?

Phobos

GrapesOfWrath
2002-Jun-02, 03:34 PM
On 2002-06-02 10:04, Phobos wrote:
have I missed something?

You mean, other than how to actually do it? /phpBB/images/smiles/icon_smile.gif

Chuck
2002-Jun-02, 03:42 PM
Keep a black hole in the engine and use Hawking radiation as a propellant, maybe?

Espritch
2002-Jun-02, 04:00 PM
From what I understand, these virtual particles always occure in pairs that almost immediately destroy each other. I don't see how you could use them without violating the conservation of mass and energy. I suspect the same rules of quantum mechanics that allow for their existence would rule out their use in this manner (I could of course be wrong).

Tomblvd
2002-Jun-02, 04:54 PM
On 2002-06-02 10:04, Phobos wrote:

Unlike jet aircraft, spacecraft are currently designed to carry and deliver their own propellant.

Huh? Jet aircraft don't carry their own propellant. Are you sure?


This is because whilst aircraft can "push" against the surrounding air, spacecraft work in the vacuum of space and seem to have nothing to "push" against.

I'm not sure how you tie propellant into this. But if that statement were true, rocket motors in space would not work now. But, fortunately, Newton was correct (his Third Law).


Once a spacecraft runs out of propellant it looses it's ability to manoeuvre and then generally looses most of its usefulness.

So does a jet.


My idea is that we design a thruster that exerts a force on these temporary particles instead of using onboard propellant. If possible such a design would in effect have a limitless supply of propellant.


I'm not sure which "temporary particles" you mean, but in any case there are probably not enough of them to have any effect on something like a spaceship. However, there are plans out there to develop something similar. Spacecraft will deploy a large sail (http://www.spacetoday.org/Rockets/NASASpaceSails/SailingToStars.html) in order to catch the solar wind. So, in essence, these craft do not have to carry any propellant, just one big-a** sail.



http://www.spacetoday.org/images/Rockets/SpaceSails/NASAspaceSailBig.jpg

Roy Batty
2002-Jun-02, 05:09 PM
Don't forget the current stuff:
http://www.planetary.org/solarsail/
/phpBB/images/smiles/icon_smile.gif

Espritch
2002-Jun-02, 05:14 PM
Judging from the direction of the commet tail, isn't the sail in the picture bulging in the wrong direction?

Phobos
2002-Jun-02, 06:49 PM
Thanks for the replies - I would like to add my comments to them:


Grapes - Yes actually doing it would not exactly be easy /phpBB/images/smiles/icon_cool.gif


Chuck - No we should not need our own black hole


Espritch - I share your understanding that the virtual particles occur in pairs, and only last for a brief moment (this is why I referred to them as temporary particles).

The question is "do they last long enough for us to "push" against them and thereby produce usable thrust ?"


Tomblvd - Jet aircraft convert their fuel into hot gasses that are indeed propelled out the back of the aircraft. However they are not the same as rocket engines because most of the energy is used to turn the turbines that in turn impart kinetic energy into the incoming air.

A better example is a jet boat. The velocity through the water is not a result of the exhaust of the spent fuel, but is instead a result of forcing water to move in the opposite direction that the boat moves in (a paddle boat performs a similar trick).

Newton’s third law "Every action has an equal and opposite reaction" is also the basis of how rockets work. The process currently requires something to be "pushed" away from the rocket and by so doing the "pushed" object exerts a force on the rocket. If we were able to use the virtual (or temporary) particles then they would perform the same role.

When I used the term “propellant” I meant the mass that is going to be used to propel the vehicle rather than the fuel that provides the energy for the process (upon reflection I should have worded this better).

I used the term "temporary particle" to refer to any matter which is created by the energy of the vacuum. Because virtual particles only last a brief time I referred to them as temporary.

If thrust is producible but small then it could still be of use where we require a spacecraft to travel for an extended time (besides our power source may not be capable of producing large amounts of energy in one go - eg. solar cells).

The solar sail idea is a good one, and is another example of how a small push over an extended period of time can be a very effective means of propelling a spacecraft.


Roy - Nice animation


Espritch - /phpBB/images/smiles/icon_wink.gif



When the energy of the vacuum creates virtual (or temporary) particles the pair consists of a particle and an anti-particle. In order for this type of propulsion to work I would need to have a method of "pushing" both particles away (if I can do this then Newtons 3rd law will do the rest).

Anyone know if it is possible to impart movement in a specific direction before they destroy each other ?

Phobos

<font size=-1>[ This Message was edited by: Phobos on 2002-06-02 18:37 ]</font>

ljbrs
2002-Jun-03, 02:43 AM
No!

As I understand it, the vacuum of space simply carries along the rest of the objects in the universe with it as the space expansion accelerates. You could not use it to propel something faster than the expansion of the universe, so you probably would seem to be going nowhere rather than somewhere.

Then again, I might not understand it.

Whatever...

ljbrs /phpBB/images/smiles/icon_biggrin.gif /phpBB/images/smiles/icon_smile.gif /phpBB/images/smiles/icon_rolleyes.gif /phpBB/images/smiles/icon_confused.gif /phpBB/images/smiles/icon_wink.gif

David Hall
2002-Jun-03, 03:16 AM
I'm no physicist, so I may be totally off.

but as I understand it, all forms of jet or rocket propulsion rely on the action/reaction of Newton's 2nd law to work. None of them ever "push" on anything except themselves. The push always comes from "throwing" something away from yourself. Jet engines are just fortunate enough to be able to gather their reaction mass from the environment, while rockets have to haul their own along. This even applies to exotic engines like the ion propulsion used by Deep Space 1, and even exotic fusion and black hole drives must get the actual reaction mass from somewhere.

The deep space version of a jet engine would be a Bussard ramjet, which gathers hydrogen from space with a magnetic field.

So, I don't see how you could actually use the zero-point energy for reaction. Unless you found some way to gather up the virtual particles (including the antimatter?) and use them for reaction, which I can't see as being possible, due to their very virtualness. So I don't see any hope on that front.

However, people are theorizing that the zero-point can be tapped for energy production. Unlimited free energy would be a great help to spaceflight, maybe even better than antimatter. But you'd still need some form of reaction mass for propulsion.

Then again I may be all wet here.

Phobos
2002-Jun-03, 07:42 AM
On 2002-06-02 23:16, David Hall wrote:
But as I understand it, all forms of jet or rocket propulsion rely on the action/reaction of Newton's 2nd law to work. None of them ever "push" on anything except themselves. The push always comes from "throwing" something away from yourself.

Strictly we should be talking about Newton’s 3rd law (http://users.powernet.co.uk/bearsoft/Newtn.html) as momentum is not being transferred to us from elsewhere.

If you prefer to use the term "throw" that is fine - we are still talking about the same process.



Jet engines are just fortunate enough to be able to gather their reaction mass from the environment, while rockets have to haul their own along. This even applies to exotic engines like the ion propulsion used by Deep Space 1, and even exotic fusion and black hole drives must get the actual reaction mass from somewhere.


This is true, but I am not aware of others suggesting using the temporary virtual particles as a propelling mass. I am not proposing that we do away with a propelling mass; instead I suggest we use the mass that fleetingly comes into existence as a result of quantum fluctuations in a vacuum (and thereby avoiding actually launching this mass with our spacecraft).



The deep space version of a jet engine would be a Bussard ramjet, which gathers hydrogen from space with a magnetic field.

So, I don't see how you could actually use the zero-point energy for reaction. Unless you found some way to gather up the virtual particles (including the antimatter?) and use them for reaction, which I can't see as being possible, due to their very virtual ness. So I don't see any hope on that front.


I do not propose that we gather them up. In a vacuum they should be coming into existence on their own and therefore our thrusters will acquire them without actually doing anything. What I propose is that we provide a field, which is waiting for these particles to appear in our thrusters. As they come into existence they will be repelled from the spacecraft and in return we should receive a force via Newton’s 3rd law.



However, people are theorizing that the zero-point can be tapped for energy production. Unlimited free energy would be a great help to space flight, maybe even better than antimatter. But you'd still need some form of reaction mass for propulsion.


True here are a couple of examples:

NASA's Breakthrough propulsion project (http://www.grc.nasa.gov/WWW/bpp/HTML%20Presentation2%20folder/sld005.htm).
Nasa investigating quantum vacuum energy (http://www.grc.nasa.gov/WWW/bpp/HTML%20Presentation2%20folder/sld021.htm)

Tapping the energy would be nice, but I was just considering how we could use the virtual particles as a way of avoiding having to eject on-board mass from a rocket.

Phobos

<font size=-1>[ This Message was edited by: Phobos on 2002-06-03 03:55 ]</font>

David Hall
2002-Jun-03, 08:25 AM
On 2002-06-03 03:42, Phobos wrote:

Strictly we should be talking about Newton’s 3rd law (http://users.powernet.co.uk/bearsoft/Newtn.html) as momentum is not being transferred to us from elsewhere.

If you prefer to use the term "throw" that is fine - we are still talking about the same process.


I just knew I'd get in trouble here. I was almost certain that "equal and opposite reaction" was the 2nd law. Looks like I got my brain backwards on this one.




I do not propose that we gather them up. In a vacuum they should be coming into existence on their own and therefore our thrusters will acquire them without actually doing anything. What I propose is that we provide a field, which is waiting for these particles to appear in our thrusters. As they come into existence they will be repelled from the spacecraft and in return we should receive a force via Newton’s 3rd law.


Ok, it sounds like it might work to me. But something still doesn't feel right. I feel like it's missing something obvious about the action/reaction. But this is getting beyond my ability.

It sure would be nice if we could design something that doesn't need reaction mass. With that and a cheap, limitless source of energy, we might just be able to make to another star.

David Hall
2002-Jun-03, 08:33 AM
Hey, wait a minute. I just remembered something. A.C. Clarke used just such a zero-point drive in his novel The Songs of Distant Earth. I just went back and read his description. He doesn't give any details of how it works, but he does say that it wouldn't need any fuel.

That book was written in 1986, so it looks like he was way ahead of you. /phpBB/images/smiles/icon_biggrin.gif

Phobos
2002-Jun-03, 11:37 AM
On 2002-06-03 04:33, David Hall wrote:
Hey, wait a minute. I just remembered something. A.C. Clarke used just such a zero-point drive in his novel The Songs of Distant Earth. I just went back and read his description. He doesn't give any details of how it works, but he does say that it wouldn't need any fuel.

That book was written in 1986, so it looks like he was way ahead of you. /phpBB/images/smiles/icon_biggrin.gif


Nope, I was referring to a new means of finding the required mass to be used to "push" (or "throw"). There are several ways for us to provide the necessary fuel - using the energy of the vacuum is just one of many old ideas (call it mass of the vacuum if you like /phpBB/images/smiles/icon_biggrin.gif)

Phobos

<font size=-1>[ This Message was edited by: Phobos on 2002-06-03 07:38 ]</font>

2002-Jun-03, 01:49 PM
<a name="20020603.5:4"> page 20020603.5:4 aka Push{er}(sp)
On 2002-06-02 14:49, Phobos wrote: To:
MY baINdex (http://www.badastronomy.com/phpBB/viewtopic.php?topic=183&forum=1#LOCKTHRD)
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hmm 40 pluss lines & time to get ready to GO 5:46 A.M. PST

Argos
2002-Jun-03, 02:03 PM
Quantum propulsion implies some statistics.
If we want to use particles as propellant, there is a *position* where we want them to be, in this case, the fuel tank or some sort of "combustion" chamber. The uncertainty principle states that we cannot choose the position *and* speed of a single particle at will (then imagine the trillions needed each second to boost a spaceship). If we do choose a position we'll lose the capability to establish its speed. So, we can end up having all the particles in the right place, but at speeds that might not satisfy our needs. Therefore, at first glance it seems to be limits for the useful handling of the vaccum energy.

Phobos
2002-Jun-03, 02:31 PM
On 2002-06-03 10:03, Argos wrote:
Quantum propulsion implies some statistics.
If we want to use particles as propellant, there is a *position* where we want them to be, in this case, the fuel tank or some sort of "combustion" chamber. The uncertainty principle states that we cannot choose the position *and* speed of a single particle at will (then imagine the trillions needed each second to boost a spaceship). If we do choose a position we'll lose the capability to establish its speed. So, we can end up having all the particles in the right place, but at speeds that might not satisfy our needs. Therefore, at first glance it seems to be limits for the useful handling of the vaccum energy.


This type of propulsion would not involve combustion, rather we would impart momentum on the particles as they appeared "somewhere at random" inside the thruster chamber. The field would be in place waiting to "push" all virtual particles as they arrive. We do not know where within the chamber they will be, or what direction they will be moving in, we only wish to impart momentum to them at the ealiest opportunity (due to their breif lifespans).

Once we have successfuly transferred momentum to these temporary particles we would have achieved our goal and produced some thrust.

We would not need trillions per second to boost a spacecraft. We would just use whatever thrust we can produce - we are in no hurry as we have a limitless supply of mass to use.

Interestingly I have just come across the following NASA link which considers using just such an aproach:

Emerging Possibilities for Space Propulsion Breakthroughs (http://www.grc.nasa.gov/WWW/PAO/html/warp/ipspaper.htm)


But wait, there's more: Another avenue to explore pushing against space is to examine the contents of the vacuum that may be indicative of a reaction mass. In addition to the items mentioned above, consider the following phenomena: Cosmic Background Radiation (ref 21), Virtual Pair Production (ref 22), and Dark Matter (ref 23). Whether any of these may constitute a reaction mass or may be evidence for a reaction mass is uncertain.

So there you have it, NASA have considered the possibility of using virtual particles for propulsion and their conclusion - they just don't know /phpBB/images/smiles/icon_frown.gif.

Phobos

<font size=-1>[ This Message was edited by: Phobos on 2002-06-03 11:45 ]</font>

Kaptain K
2002-Jun-03, 04:06 PM
Phobos,

I think that what you are missing here is the incredibly short lifespan of virtual particles. The lifetime of a virtual pair of particles is on the order of Planck time (the quantum of time), a unit of time so short that if it was one second, one second would be a billion times the age of the universe. That is why they are called "virtual particles". Their life is so short that they have no time to interact with the rest of the universe. It is only in the weirdly warped space-time at the event horizon of a black hole that one of the virtual pair is allowed to become real.

Phobos
2002-Jun-03, 05:12 PM
On 2002-06-03 12:06, Kaptain K wrote:
Phobos,

I think that what you are missing here is the incredibly short lifespan of virtual particles. The lifetime of a virtual pair of particles is on the order of Planck time (the quantum of time), a unit of time so short that if it was one second, one second would be a billion times the age of the universe. That is why they are called "virtual particles". Their life is so short that they have no time to interact with the rest of the universe. It is only in the weirdly warped space-time at the event horizon of a black hole that one of the virtual pair is allowed to become real.


If lifespan of virtual particles is so short that they have no time to interact with the rest of the universe then how do you account for the Casimir Effect (http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/casimir.html).

If virtual particles are responsible for the Casimir effect, then they are capable of interacting with the real world.

So unless the Casimir effect only works in black holes then there must be something wrong with your statement.

Phobos

Argos
2002-Jun-03, 05:12 PM
Ok, Phobos. I think I understand your point of view. And thanks for the links.

I should add to what KK said about the life span of particles the fact that fluctuations in the vacuum allowing for detctable radiation (i.e. momentum), will only occur in large volumes of space (if i'm right). So, a spaceship benefiting from momentum generated by natural quantum fluctuation must have a huge dimension.

Of course you could - by technical means beyond our horizon - "speed up" the rate of the fluctuations, or compact the region of the space-time you want to use as propellant. It could be viable perhaps, to an ultra-developed civilization.



<font size=-1>[ This Message was edited by: Argos on 2002-06-03 13:30 ]</font>

informant
2002-Jun-03, 05:39 PM
page 20020603.5:4 aka Push{er}(sp)
On 2002-06-02 14:49, Phobos wrote: To:
MY baINdex
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1: of all the required
2: PUSHee's (sp)
3: would be greater than the = PROpellANTs
4: Just guessing
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hmm 40 pluss lines & time to get ready to GO 5:46 A.M. PST

Good guess...!

(Oh my goodness, I've just understood one of HUb's posts!)

Phobos
2002-Jun-03, 05:47 PM
I believe Hubs pushees are the virtual particals. Since the introduction of new virtual particles would be an ongoing process throughout the life of the spacecraft the total mass of them would not affect the design of the spacecraft in the same way that the total mass of propellant from conentional rocket propulsion does.

Phobos

informant
2002-Jun-03, 06:03 PM
I thought what he was saying was that the amount of virtual particles available in the vacuum might not be enough to "push" the ship...

Argos
2002-Jun-03, 06:12 PM
Fools rush in where angels fear to tread. So, here I go.

I think that indeed there's a *very* small probability that you could have particles lasting an adequate time span to interact with the universe, generating thrust. But I fear you wouldn't have enough particles, considering such small probability.

And there's the fact that, even if you could generate useful momentum in a reasonable volume of space, with particles lasting exactly the time you want them to, you'd still have every particle moving in a different direction, so that the sum of all directions possible would leave you with a resting spaceship. You'd just have to "arrange" the momentum, to "beam" the particles in a specific direction in order to obtain thrust. And this seems to me to violate the uncertainty principle, unless you'd arrange the particle after its formation. But arranging particles after their formation would require energy, so that the net result would be negligible.

Somebody help us! I really want to believe there are alternative ways to cross the stars!


<font size=-1>[ This Message was edited by: Argos on 2002-06-03 14:21 ]</font>

Phobos
2002-Jun-03, 06:53 PM
On 2002-06-03 14:12, Argos wrote:
Fools rush in where angels fear to tread. So, here I go.

I think that indeed there's a *very* small probability that you could have particles lasting an adequate time span to interact with the universe, generating thrust. But I fear you wouldn't have enough particles, considering such small probability.

And there's the fact that, even if you could generate useful momentum in a reasonable volume of space, with particles lasting exactly the time you want them to, you'd still have every particle moving in a different direction, so that the sum of all directions possible would leave you with a resting spaceship. You'd just have to "arrange" the momentum, to "beam" the particles in a specific direction in order to obtain thrust. And this seems to me to violate the uncertainty principle, unless you'd arrange the particle after its formation. But arranging particles after their formation would require energy, so that the net result would be negligible.

Somebody help us! I really want to believe there are alternative ways to cross the stars!


<font size=-1>[ This Message was edited by: Argos on 2002-06-03 14:21 ]</font>


Ok let me try to simplify my argument. The Casimir effect tells us that quantum fluctuations in a vacuum can produce real world effects (in this case a force either attracting or repelling two plates placed near each other).

Since virtual particles seem to be able to affect the world of real particles, then the reverse would seem possible as well. However, virtual particles only exist for a very short period of time, so this dictates that we have to have a field in place waiting to impart momentum on the particles the instant they come into existance.

Now consider our thruster chamber. Virtual particle come in to existance at random locations with random velocies. If we are able to impart momentum into the particles then we would achieve our desired thrust (the net momentum in the particles would be in the direction of the applied external force).

Phobos

<font size=-1>[ This Message was edited by: Phobos on 2002-06-03 15:03 ]</font>

beskeptical
2002-Jun-03, 09:04 PM
On 2002-06-02 13:14, Espritch wrote:
Judging from the direction of the commet tail, isn't the sail in the picture bulging in the wrong direction?


Yes. /phpBB/images/smiles/icon_smile.gif It just seemed like someone should answer. /phpBB/images/smiles/icon_biggrin.gif

Tim Thompson
2002-Jun-03, 09:25 PM
Time to go back and re-read the Casimir Effect Page (http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/casimir.html). The emphasis in what follows is mine. ... "Casimir realised that between two plates, only those virtual photons whose wavelengths fit a whole number of times into the gap should be counted when calculating the vacuum energy." ... "Particles other than the photon also contribute a small effect but only the photon force is measurable."

Note that only the force exerted by photons is measureable. I don't know of any technology that would allow you to scoop up photons and use them as a propellant. Charged particles, perhaps, Even uncharged particles, perhaps. But not photons.

Also note that the force is felt only when the plates are an integral number of photon wavelengths apart. There is no force at all under other circumstances, because the close spacing cuts off other photon modes. If you just look at an exposed surface with "infinite" room above it, then there is no Casimir force (it's not that the force becomes too small to measure above the noise, but that the force actually is not there at all).

I think the value of the existence of the Casimir force is exaggerated, as to the possibility of using virtual particles as some form of propellant.

Now, assuming we set aside the photon question for a moment, look at the lifetime of a "virtual particle". The Planck time is about 5.4x10^-44 seconds. All you have to do, in principal, is invent a technology that will grab ahold of something in roughly 10^-44 seconds. That is something of a challenge for the amateur (or professional) tinkerers & inventors in the crowd, but may be possible, in the same sense that "quantum nondemolition" measurements are. However, i think it's safe to say that no existing technology will handle the problem, nor do i know of any existing theory that promises to fuel such a proposed technology.

But look at the theory, and consider one of the theoretical underpinnings of Hawking Radiation. The virtual pairs are particle antiparticle pairs. If your particle grabber grabs both of them, it will also have to separate them before they take each other out in mutual destruction. But if it does not grab both, what happens to the ungrabbed particle? It rams into the front of your spacecraft, slowing you down. And the amount of slowing down is probably comparable to the amount of speeding up, since we are talking about particle pairs, so the net result is probably something like "was this worth the effort in the first place?"

Either that, or all of the particles not grabbed wind up flying forward and appear to be emitted forward by your spacecraft. So the net result is that your spacecraft launches as many particles forwards as backwards, and we are in the net zero energy realm again. That's sort of the cheap explanation for how Hawking radiation works, with the antiparticle going backwards in time entering the black hole and decreasing its mass, while the matter particle going forwards in time appears to carry the mass away (not a good explanation, but it works on the mean streets; see "What is Hawking Radiation? (http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/hawking.html)" for a better but less comprehensible explanation).

So, all you need to do is grab & separate the virtual pair with some technique that operates comfortably on time scales of 10^-44 seconds or less (it has to work faster than the time scale of the particle you want to grab, which is initmately connected to the energy of the particle through the uncertainty relation). Then you have a tank of matter and a tank of antimatter, all sucked out of the "vacuum", and maybe you can use their later mutual annihilation as an energy source.

But there is one big theoretical problem. the Planck time scale of about 10^-44 seconds is fundamental, and applies to absolutely everything (matter or energy) which exists, including the particle grabber machine, whatever it is. So you can't grab a pair in any "classical" sense at all, and we are back to the profoundly correct comment from Argos that quantum propulsion implies some statistics. You'll grab some, you'll miss some, and you'll grab half of some. That means that some of the particles will take energy away from the ship, just as aome add energy. In the absence of a formal calculation (left as an exercise for the student), I can't say what the fraction of each would be. However, it seems likely to me that the return may not be up to the investmaent standards.

Cheers.

Phobos
2002-Jun-03, 10:52 PM
On 2002-06-03 17:25, Tim Thompson wrote:
Time to go back and re-read the Casimir Effect Page (http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/casimir.html). The emphasis in what follows is mine. ... "Casimir realised that between two plates, only those virtual photons whose wavelengths fit a whole number of times into the gap should be counted when calculating the vacuum energy." ... "Particles other than the photon also contribute a small effect but only the photon force is measurable."


Ok, so your quote confirms that virtual particle can affect the states of real particles.



Note that only the force exerted by photons is measureable. I don't know of any technology that would allow you to scoop up photons and use them as a propellant. Charged particles, perhaps, Even uncharged particles, perhaps. But not photons.


No scooping has been requested - we are only interested in the particles that have been created in the thruster chamber. We are not going to separate the particles or process them in any way, but we must impart momentum on them. That is why our thruster chamber must have a field awaiting them (it is our intention to impart momentum on all created matter & antimatter).



Also note that the force is felt only when the plates are an integral number of photon wavelengths apart. There is no force at all under other circumstances, because the close spacing cuts off other photon modes. If you just look at an exposed surface with "infinite" room above it, then there is no Casimir force (it's not that the force becomes too small to measure above the noise, but that the force actually is not there at all).


True, but remember the effect plays no part in the propulsion system. I only mentioned it becuase it demonstrates that virtual particles do have an effect on real particles (and therefore it may be possible to impart momentum onto them as a reverse of this process)

What I am proposing may be loosely thought of as a reverse of the Casimir efffect - We apply a force to a quauntum vacuum field in order to impart momentum on virtual particles.



I think the value of the existence of the Casimir force is exaggerated, as to the possibility of using virtual particles as some form of propellant.


That may be true. I am only proposing a possible technology, but it seems we already have solutions for propellantless propulsion (http://jnaudin.free.fr/html/omptv1.htm) so I doubt the technology will ever be used.



Now, assuming we set aside the photon question for a moment, look at the lifetime of a "virtual particle". The Planck time is about 5.4x10^-44 seconds. All you have to do, in principal, is invent a technology that will grab ahold of something in roughly 10^-44 seconds. That is something of a challenge for the amateur (or professional) tinkerers & inventors in the crowd, but may be possible, in the same sense that "quantum nondemolition" measurements are. However, i think it's safe to say that no existing technology will handle the problem, nor do i know of any existing theory that promises to fuel such a proposed technology.


As stated earlier, that is not the proposal. If the technique can be made to work it will overcome these objections in two ways;

1) The field which is going to impart momentum in the virtual particles does not wait for them to arrive. Despite their brief existance, once they exist they will be subjected to all the forces of the space they occupy. Since one of those forces will be our momentum transfer force the job will be done at the moment of their arrival.

2) No grabbing or manipulation takes place - just momentum transfer (particle and antiparticle alike).



But look at the theory, and consider one of the theoretical underpinnings of Hawking Radiation. The virtual pairs are particle antiparticle pairs. If your particle grabber grabs both of them, it will also have to separate them before they take each other out in mutual destruction. But if it does not grab both, what happens to the ungrabbed particle? It rams into the front of your spacecraft, slowing you down. And the amount of slowing down is probably comparable to the amount of speeding up, since we are talking about particle pairs, so the net result is probably something like "was this worth the effort in the first place?"


Both virtual particle pairs will recieve a transfer of momentum. When you transfer momentum to the antiparticle it should behave exactly as the particle (ie both types should obey newtons 3rd law and help produce thrust in our spacecraft).

Since both particles are shortlived they will probably not travel very far before the self anyalate, but provided a momentum exchange has taken place then we should receive the accelaration force we require.




Either that, or all of the particles not grabbed wind up flying forward and appear to be emitted forward by your spacecraft. So the net result is that your spacecraft launches as many particles forwards as backwards, and we are in the net zero energy realm again. That's sort of the cheap explanation for how Hawking radiation works, with the antiparticle going backwards in time entering the black hole and decreasing its mass, while the matter particle going forwards in time appears to carry the mass away (not a good explanation, but it works on the mean streets; see "What is Hawking Radiation? (http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/hawking.html)" for a better but less comprehensible explanation).

So, all you need to do is grab & separate the virtual pair with some technique that operates comfortably on time scales of 10^-44 seconds or less (it has to work faster than the time scale of the particle you want to grab, which is initmately connected to the energy of the particle through the uncertainty relation). Then you have a tank of matter and a tank of antimatter, all sucked out of the "vacuum", and maybe you can use their later mutual annihilation as an energy source.



Again this is covered by the fact that we are not separating the particles.



But there is one big theoretical problem. the Planck time scale of about 10^-44 seconds is fundamental, and applies to absolutely everything (matter or energy) which exists, including the particle grabber machine, whatever it is. So you can't grab a pair in any "classical" sense at all, and we are back to the profoundly correct comment from Argos that quantum propulsion implies some statistics. You'll grab some, you'll miss some, and you'll grab half of some. That means that some of the particles will take energy away from the ship, just as aome add energy. In the absence of a formal calculation (left as an exercise for the student), I can't say what the fraction of each would be. However, it seems likely to me that the return may not be up to the investmaent standards.

Cheers.


No particle grabbing, and the momentum transfer should apply to all particles. We do not need to "treat" the particles because we apply our force to all.

Phobos

Espritch
2002-Jun-04, 04:28 AM
Both virtual particle pairs will recieve a transfer of momentum. When you transfer momentum to the antiparticle it should behave exactly as the particle (ie both types should obey newtons 3rd law and help produce thrust in our spacecraft).

I should probably stay out of this one since my knowledge of quantum mechanics could be typed on the back of a postage stamp in a large font (something to the effect of "It's really really hard to understand."), but I've never let mere ignorance stop me before, so why start now?

Unless I am mistaken, the charges of particle/anti-particle pairs are opposite. So if you used an electromagnetic field to "push" them, the push on the particle would be opposite to the push on the anti-particle so your net gain would be zero.

And if electromagnetic fields will not do the job, what is left?

Phobos
2002-Jun-04, 10:53 AM
On 2002-06-04 00:28, Espritch wrote:

Both virtual particle pairs will recieve a transfer of momentum. When you transfer momentum to the antiparticle it should behave exactly as the particle (ie both types should obey newtons 3rd law and help produce thrust in our spacecraft).


I should probably stay out of this one since my knowledge of quantum mechanics could be typed on the back of a postage stamp in a large font (something to the effect of "It's really really hard to understand."), but I've never let mere ignorance stop me before, so why start now?

Unless I am mistaken, the charges of particle/anti-particle pairs are opposite. So if you used an electromagnetic field to "push" them, the push on the particle would be opposite to the push on the anti-particle so your net gain would be zero.

And if electromagnetic fields will not do the job, what is left?


Photons carry momentum but have no mass (http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/960731.html). I suspect one solution may be to bombard our virtual particles with a stream of photons and let them perform the necessary momentum transfer.

That may be one way, but I will leave it to others with greater expertise in this field to confirm/repute if momentum transfer to virtual particle/antiparticle pairs is achievable with present day technology.

Phobos

Kaptain K
2002-Jun-09, 11:47 AM
Phobos.

Virtual pairs are (as you have been told before) particle-antiparticle pairs. If you seperate them, their momentum cancels (i.e. half go forward and half go backward). If you do not seperate them, they will destroy each other before you can shove them anywhere.

_________________
When all is said and done - sit down and shut up!

<font size=-1>[ This Message was edited by: Kaptain K on 2002-06-09 07:49 ]</font>

Phobos
2002-Jun-09, 12:59 PM
On 2002-06-09 07:47, Kaptain K wrote:
Phobos.

Virtual pairs are (as you have been told before) particle-antiparticle pairs. If you seperate them, their momentum cancels (i.e. half go forward and half go backward). If you do not seperate them, they will destroy each other before you can shove them anywhere.


From the first post on this thread I have specified the temporary nature of the particles. There is no need to repeat information of which we are not in dispute.

As I see it the issue boils down to the question "Are we able to prepare in advance of the arrival of the particles, a field which will transfer momentum".

I do not question that the particles are only present for a very short time. But in the brief time that they are present the following statements can be reasoned;

1. They are capable of creating effect in real particles (Casimir effect).

2. Whilst they are present they are subjected to the forces of the environment that they briefly occupy.

Logic is not always correct (especially when dealing with quantum effects), but it would seem that due to the first fact above it should be possible to affect virtual particles using fields that already exist when the particles are created.

I do not claim to know how (or even if) momentum could be transfered to virtual particles. But if it is possible then this would seem to be a candidate for a possible propellantless propulsion system.

Phobos

<font size=-1>[ This Message was edited by: Phobos on 2002-06-09 09:06 ]</font>

Richard J. Hanak
2002-Jun-10, 04:15 PM
/phpBB/images/smiles/icon_wink.gif /phpBB/images/smiles/icon_wink.gif

Here is a better use for the vacuum in space. Build a giant smokestack reaching into outer space. Then put all noxious gases into it and the vacuum of space will pull them out and get rid of them where they can't do any harm. Have a valve at the bottom of the stack, though, so the vacuum won't suck all the air from the earth.

Don't wory about the smokestack collapsing, since its centrifugal force (as it orbits the Earth, so to speak)will pull against the gravity that wants it to fall to Earth.

P.S. At one time I was an air-pollution control engineer, but I couldn't sell this idea!

(Only a joke, folks. /phpBB/images/smiles/icon_smile.gif

Phobos
2002-Jun-10, 04:29 PM
On 2002-06-10 12:15, Richard J. Hanak wrote:
/phpBB/images/smiles/icon_wink.gif /phpBB/images/smiles/icon_wink.gif

Here is a better use for the vacuum in space. Build a giant smokestack reaching into outer space. Then put all noxious gases into it and the vacuum of space will pull them out and get rid of them where they can't do any harm. Have a valve at the bottom of the stack, though, so the vacuum won't suck all the air from the earth.

Don't wory about the smokestack collapsing, since its centrifugal force (as it orbits the Earth, so to speak)will pull against the gravity that wants it to fall to Earth.

P.S. At one time I was an air-pollution control engineer, but I couldn't sell this idea!

(Only a joke, folks. /phpBB/images/smiles/icon_smile.gif


I wonder if your device would qualify as a vacuum cleaner ?

Phobos /phpBB/images/smiles/icon_biggrin.gif

Kaptain K
2002-Jun-11, 07:12 AM
Why?
Is your vacuum dirty?

Fast Eddie
2002-Jun-12, 03:21 AM
What ever happened to Bob Lazar's Element #115 ... the atomic weight of which is so heavy that it leaks gravity waves ... which can be directed to repel or attract in the direction you wish to retreat from or go to ??