Reason for rubber ball idea. - Initial idea.

chat · 2003-10-24 08:34:06

It seems that conservation of momentum no matter how hard you try to cheat is not going to allow a way to gain forward thrust.

In my initial idea for space travel i thought that a force gained in throwing and loosing momentum no matter how small could gain a velocity.

My initial idea was to make a tube inside a spacecraft that accelerated particles down one end of the spaceship, and decelerated them on the return trip.

But since conservation of momentum won't allow this, then couldn't you simply use a particle accelerator inside the spacecraft in a semi circular magnetic tube.?

Accelerate the particles as close to light speed as the magnets will drive them.
Then release them out the back of the spaceship?
Now you should have a net thrust at very high velocities.

fermilab does this with current technology to about 99% the speed of light.

I bet the electricity bill will be nasty for this though

Euler · 2003-10-24 12:12:53

I bet the electricity bill will be nasty for this though

Yes. A high exhaust velocity means that the spaceship is fuel-efficient. However, it also means that more power is necessary to produce the same amount of thrust.

chat · 2003-10-24 18:49:24

Thanks euler,

So in theory we have something here that can go some % the speed of light with current technology?
And the only factor stopping this from being done right now is the amount of energy required to do it.?
And money of course

The electricity costs might not be as much you would think.

In space you can have super cooled magnets that are very efficient, an acceleration tube filled with only the vacuum of space so very little resistance for the accelerating particle.
And no need to try and brute force the acceleration as the conservation of momentum allows you to slowly accelerate particles to the fastest the acceleration circle can take before releasing them out the back as thrust.

I think a small nuclear reactor might fill the bill for electricity requirements.

At this point i bet a math wizz would come in handy

Euler · 2003-10-24 23:33:09

Your particle accelerator engine works in a similar way to an ion engine, though ion engines usually use a short linear accelerator that does not accelerate ions above .001c.

The kinetic energy of the particles (and therefore the energy used to accelerate them) is equal to (1/2)mass*velocity^2. The momentum is equal to mass*velocity. Power is equal to energy/time, and force(thrust) is equal to the change in momentum/time. Therefore power/thrust = velocity/2. So if the exhaust has a velocity of .33c, it would require 50 Mw to produce 1N of force.

chat · 2003-10-25 07:54:28

Hi Euler,

Thanks for the calculations.
I just knew a math wizz was here somewhere

Now all we need is a 50mw nuclear generator and plutonium, a launch vehicle, some expensive magnets and acceleration tube, a super computer to control the acceleration and release, a few tons of particle accelerant, and a few good astronauts to assemble it in space.
And maybe a good politician to let the nuclear activists know about the plutonium heading into space.

You don't happen to know anyone with these things just sitting around in the garage collecting dust, other than the politician?

Any ideas on developing such an idea?
I did propose this exact idea to JPL about 12 years ago with a very poor response.
So i put the idea away and went to study more on it.
Not sure if i stepped on toes with the idea, or that my lack of any science degree made them immediately dismiss it before considering it.

I seek no monetary gains from the idea.
Just that the idea gets out and gets going.

Nick

Shaun Barrett · 2003-10-26 02:32:21

Please excuse this intrusion into your discussion but I have a question for Euler:-
Just browsing through your equations and the example you gave at the end, I noticed that producing 1 newton of thrust appears to require less and less power as you reduce exhaust velocity.
This sounds counter-intuitive, at least to me!
What am I missing here?

Euler · 2003-10-26 14:06:05

Please excuse this intrusion into your discussion but I have a question for Euler:-
Just browsing through your equations and the example you gave at the end, I noticed that producing 1 newton of thrust appears to require less and less power as you reduce exhaust velocity.
This sounds counter-intuitive, at least to me!
What am I missing here?

Just because it seems counter-intuitive does not mean it is not true! The momentum of an object is proportional to its velocity, but the kinetic energy is proportional to the square of the velocity. If you throw a heavy object (e.g. a bowling ball) at a low speed, you will notice a significant amount of recoil. However, if you use the same amount of energy to throw a light object (e.g. a baseball) at a high speed, you will hardly notice the recoil.

chat · 2003-10-27 19:56:06

Euler,

Just thinking out loud here.
And hoping for a few replies about my noisy thoughts.

If a 50mw nuclear generator can produce .33c.
If the initial mass of the spaceship is 1/3 and the particle accelerant is 2/3 the total mass.
It should be able to obtain a maximum speed of .22c ?

Obviously for interstellar distances nuclear is the way to go.
And if no humans are on board then why not 100mw or 500mw?

But if you reduce the thrust to say .02c, then the mw requirements also reduce proportionally.
I calculate that to produce thrust of .02c will require about 1mw or less?
In the above formula of 1/3 ship 2/3 fuel.
We should be able obtain a maximum speed of .015c ?

1mw could be produced with conventional non nuclear means.
And if we are very sneaky we could use the waste product from the production or electricity as the particle accelerant.?

.015c gets us around the solar system in short times.
With a nice protective magnetic field for the people inside.
Well actually .0075c because you will need to turn the ship at whatever the 1/2 way point is.

I haven't done any calculations in change of velocity/time.
That is beyond my math skills.

That might be the un doing of this idea, and may drastically alter power requirements.
If the times are to long to obtain any useful speed.

As for deep space 1 as i understand, it has a pretty slow velocity/time.

Nick

Euler · 2003-10-27 20:58:42

If a 50mw nuclear generator can produce .33c.
If the initial mass of the spaceship is 1/3 and the particle accelerant is 2/3 the total mass.
It should be able to obtain a maximum speed of .22c ?

I think the relavent equation is velocity=exhaust velocity*ln(initial mass/final mass), which should give a final velocity of .36c.

Obviously for interstellar distances nuclear is the way to go.
And if no humans are on board then why not 100mw or 500mw?

Part of why I chose 50 Mw was becuase there is a thread in the New Discoveries forum about a "small" nuclear reactor that generates 50 Mw. The core is about 20m long, 2.5m diameter, and weighs 60 tons.

But if you reduce the thrust to say .02c, then the mw requirements also reduce proportionally.
I calculate that to produce thrust of .02c will require about 1mw or less?

Yes it reduces proportionally. So with an exhaust velocity of .02c, it would take (.02/.33)*50Mw = 3Mw to produce 1N of force.

chat · 2003-10-28 06:09:48

Euler,

I guess at some point the weight of the nuclear reactor as it is sized up will limit it's reason to be there.
At 50mw with a thrust of .36c no real need to go any faster exists.

The real question seems to be, will it be a Ferrari or a slow golf cart.

And i just knew i should have broken out my calculator for the math

Anyone have any thoughts on producing say 3mw of conventional power in space .?
The waste product from the production of the electricity needing to be used as particle accelerant.

Nick

Euler · 2003-10-28 11:33:43

The real question seems to be, will it be a Ferrari or a slow golf cart.

Slow golf cart. But if you let it run for a long time, eventually you will be going at a very high speed.

chat · 2003-10-28 14:17:58

Euler,

I had a feeling it would be golf cart like.

So it looks like a great vehicle for getting un manned probes to the nearby stars.

But not much of a vehicle for traveling around the solar system, unless you have a gigantic nuclear reactor and a lot of fuel.

Now wouldn't that be unusual if we had machines visiting the stars, but still had trouble with visiting our own solar system.

streety · 2003-10-28 17:50:02

I'm not really a physicist but wouldn't relativity begin to act at these sorts of speeds, throwing out all these equations?

Euler · 2003-10-28 20:24:06

Relativity does have some affect at these speeds, but it is not enough to overwhelm the Newtonian equations yet. Most relativistic quantities are multiplied or divided by a factor of (1-v^2/c^2)^.5. For .33, this would come out to about 5% difference. Enough to have a measurable effect, but not enough to be too preoccupied with at this stage.

chat · 2003-10-28 21:03:12

Euler,

I have a solution to the solar system travel problem.

50 mw nuclear reactor , thrust at .02c, and 17 acceleration tubes all producing 1 newton of thrust.
A tech nightmare for sure, but a simple solution.

Now we have a 17n power golf cart

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#1 2003-10-24 08:34:06

Re: Reason for rubber ball idea. - Initial idea.

#2 2003-10-24 12:12:53

Re: Reason for rubber ball idea. - Initial idea.

#3 2003-10-24 18:49:24

Re: Reason for rubber ball idea. - Initial idea.

#4 2003-10-24 23:33:09

Re: Reason for rubber ball idea. - Initial idea.

#5 2003-10-25 07:54:28

Re: Reason for rubber ball idea. - Initial idea.

#6 2003-10-26 02:32:21

Re: Reason for rubber ball idea. - Initial idea.

#7 2003-10-26 14:06:05

Re: Reason for rubber ball idea. - Initial idea.

#8 2003-10-27 19:56:06

Re: Reason for rubber ball idea. - Initial idea.

#9 2003-10-27 20:58:42

Re: Reason for rubber ball idea. - Initial idea.

#10 2003-10-28 06:09:48

Re: Reason for rubber ball idea. - Initial idea.

#11 2003-10-28 11:33:43

Re: Reason for rubber ball idea. - Initial idea.

#12 2003-10-28 14:17:58

Re: Reason for rubber ball idea. - Initial idea.

#13 2003-10-28 17:50:02

Re: Reason for rubber ball idea. - Initial idea.

#14 2003-10-28 20:24:06

Re: Reason for rubber ball idea. - Initial idea.

#15 2003-10-28 21:03:12

Re: Reason for rubber ball idea. - Initial idea.

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