My Ignorant/Curious Speculation about Negative Mass and Spacecraft

[DanHalen]

Assuming that negative mass is indeed real, would it be theoretically possible to create a spacecraft that had negative mass 'counter weights' almost equal in mass to the positive mass, making the spacecraft extremely light (and thus giving it more delta-V from the same amount of fuel)?

[Bill Phil]

You need the energy to make it first. And depending on the location of the masses, you might accidentally fly off at a significant fraction of C...

[K^2]

Assuming that negative mass is indeed real, would it be theoretically possible to create a spacecraft that had negative mass 'counter weights' almost equal in mass to the positive mass, making the spacecraft extremely light (and thus giving it more delta-V from the same amount of fuel)?

Lets start from perspective of classical mechanics. The first thought would be yes, it should help. You want to bring ship to some velocity v. So you take some big mass M, add some smaller amount of negative mass (-m), and now total momentum you need is (M-m)v. Requiring less thrust and less fuel.

But consider the actual interactions between chunks of mass and negative mass. Imagine that you have a big block of negative mass sitting in front of you. You try to push it out of the way. You apply a force forward, but F = ma, and the mass is negative. The block tries to accelerate towards you instead. If you want it to move forward, you have to pull on it instead! I cannot imagine how one would build a structure out of this stuff. At best, it'd probably rip itself apart.

Now, from perspective of Quantum Mechanics. What you are really suggesting is that part of the matter in the ship has forward velocity but reversed momentum. This is, indeed, possible. Virtual particles do this routinely. However, such particles cannot propagate freely. They can only hold on to that momentum for a brief time, and then mast pass it on to other matter. Any stable matter must propagate in direction of the momentum. And so you end up with no way to create negative mass. Which might be for the best, keeping the above paragraphs in mind.

[Skyler4856]

Have you ever heard of an alcubierre drive?

http://en.wikipedia.org/wiki/Alcubierre_drive

[vger]

Maybe I'm misinterpreting what negative mass is, but IF this were possible, wouldn't a combination of positive and negative mass elements potentially produce a "perfect" machine? Like a radiometer, but without the need for sunlight?

[Bill Phil]

Lets start from perspective of classical mechanics. The first thought would be yes, it should help. You want to bring ship to some velocity v. So you take some big mass M, add some smaller amount of negative mass (-m), and now total momentum you need is (M-m)v. Requiring less thrust and less fuel.

But consider the actual interactions between chunks of mass and negative mass. Imagine that you have a big block of negative mass sitting in front of you. You try to push it out of the way. You apply a force forward, but F = ma, and the mass is negative. The block tries to accelerate towards you instead. If you want it to move forward, you have to pull on it instead! I cannot imagine how one would build a structure out of this stuff. At best, it'd probably rip itself apart.

Now, from perspective of Quantum Mechanics. What you are really suggesting is that part of the matter in the ship has forward velocity but reversed momentum. This is, indeed, possible. Virtual particles do this routinely. However, such particles cannot propagate freely. They can only hold on to that momentum for a brief time, and then mast pass it on to other matter. Any stable matter must propagate in direction of the momentum. And so you end up with no way to create negative mass. Which might be for the best, keeping the above paragraphs in mind.

Wouldn't adding a negative mass accelerate the craft in question?

[K^2]

Wouldn't adding a negative mass accelerate the craft in question?

Depends on how you add it. But if it's in the drag mode, like you're flying through it, and it sticks to the ship, yeah, drag would have to be negative. Which is just one more reason that I'm glad stable negative mass matter doesn't exist and I don't have to think about it.

[DanHalen]

But consider the actual interactions between chunks of mass and negative mass. Imagine that you have a big block of negative mass sitting in front of you. You try to push it out of the way. You apply a force forward, but F = ma, and the mass is negative. The block tries to accelerate towards you instead. If you want it to move forward, you have to pull on it instead! I cannot imagine how one would build a structure out of this stuff. At best, it'd probably rip itself apart.

What if the negative mass object did not actually touch the positive portion of the vessel, but was 'towed' along with magnets?

In other words:

> Rocket gives thrust

> Magnet attached to positive mass part 'pushes' against magnet on negative mass part, which in turn moves towards the first magnet (because of its negative mass)

Now obviously, I am no physicist, and I understand that I may be making some fundamental mistake or misunderstanding that sticks out like a sore thumb to those who are educated experts in the field. This seems so simple, that I have a 'feeling' that I'm missing/forgetting something that invalidates the entire idea, but I can't see it myself. My best guess would be that there is something that makes this 'perpetual motion' (impossible, I know).

I made a quick illustration of this - If my sketch is correct, then the bottom arrow would be the overall motion of the vehicle:

[Bill Phil]

The magnet setup may be an equal mass investment as not having the negative matter in the first place. Which would make it hard to use or even useless. Which isn't a bad thing per se...

[stupid_chris]

What if the negative mass object did not actually touch the positive portion of the vessel, but was 'towed' along with magnets?

In other words:

> Rocket gives thrust

> Magnet attached to positive mass part 'pushes' against magnet on negative mass part, which in turn moves towards the first magnet (because of its negative mass)

Now obviously, I am no physicist, and I understand that I may be making some fundamental mistake or misunderstanding that sticks out like a sore thumb to those who are educated experts in the field. This seems so simple, that I have a 'feeling' that I'm missing/forgetting something that invalidates the entire idea, but I can't see it myself. My best guess would be that there is something that makes this 'perpetual motion' (impossible, I know).

I made a quick illustration of this - If my sketch is correct, then the bottom arrow would be the overall motion of the vehicle:

https://fbcdn-sphotos-b-a.akamaihd.net/hphotos-ak-xfp1/v/t1.0-9/s720x720/11016724_10204292283241478_7747538170026620393_n.jpg?oh=17a59b2e45ad57511275ab04369e97e1&oe=55968992&__gda__=1435949163_54e40714d00e0f16b2b557e0d45ea01f

To start with, that kinda implies your magnet is made of negative mass, else, it needs to have negligible positive mass else the point is moot. I don't think a magnet made of negative mass would even hold itself together, but let's pretend it does. Well to start with, magnets are dipoles, and in this configuration, it would want to flip around so that both poles attract each other, and then once it does, the negative mass will be repulsed away. If you find a way to not make it happen, things are getting intereresting. The biggest problem is that this whole vessel is not really in a stable equilibrum.

[Tommygun]

Well if gravitons do exsist, maybe they could be used to "lighten" a ship?

[helaeon]

How about creating a field that changes the way the matter making up the ship interacts with the Higgs field? Mass is essentially how viscous the Higgs field is in relation to a given particle. So... what if you made it less so. Make the particles that make up your ship blind to the Higgs field (really the other way around so Higgs field doesn't recognize the particles on the ship). Kind of like a photon which doesn't interact with the Higgs field (or if it does so only incredibly weakly).

[Bill Phil]

How about creating a field that changes the way the matter making up the ship interacts with the Higgs field? Mass is essentially how viscous the Higgs field is in relation to a given particle. So... what if you made it less so. Make the particles that make up your ship blind to the Higgs field (really the other way around so Higgs field doesn't recognize the particles on the ship). Kind of like a photon which doesn't interact with the Higgs field (or if it does so only incredibly weakly).

Not only would you need a lot of energy, you would have to be smart about how you do it. you might just kill the crew.