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

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

Keep a black hole in the engine and use Hawking radiation as a propellant, maybe?

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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).

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

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).

So does a jet.

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 in order to catch the solar wind. So, in essence, these craft do not have to carry any propellant, just one big-a** sail.

Don't forget the current stuff:
http://www.planetary.org/solarsail/
[img]/phpBB/images/smiles/icon_smile.gif[/img]

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Judging from the direction of the commet tail, isn't the sail in the picture bulging in the wrong direction?

Thanks for the replies - I would like to add my comments to them:


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


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 - [img]/phpBB/images/smiles/icon_wink.gif[/img]



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>

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 [img]/phpBB/images/smiles/icon_biggrin.gif[/img] [img]/phpBB/images/smiles/icon_smile.gif[/img] [img]/phpBB/images/smiles/icon_rolleyes.gif[/img] [img]/phpBB/images/smiles/icon_confused.gif[/img] [img]/phpBB/images/smiles/icon_wink.gif[/img]

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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.

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Strictly we should be talking about Newton’s 3rd law 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.

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).

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.

True here are a couple of examples:

NASA's Breakthrough propulsion project.
Nasa investigating quantum vacuum energy

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>

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.


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.

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...And that, my liege, is how we know the Earth to be banana-shaped. --Sir Bedevere

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. [img]/phpBB/images/smiles/icon_biggrin.gif[/img]

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...And that, my liege, is how we know the Earth to be banana-shaped. --Sir Bedevere

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 [img]/phpBB/images/smiles/icon_biggrin.gif[/img])

Phobos

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

<a name="20020603.5:4"> page 20020603.5:4 aka Push{er}(sp)
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hmm 40 pluss lines & time to get ready to GO 5:46 A.M. PST

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

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

Phobos

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

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.

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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.

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

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>