[Moontanman]

For a very good description of a light sail and how it would work read Robert L. Forward's book Rocheworld. Not only is it a great but R. Forward is a scientist and insists his books follow the science as closely as possible. I think you'll find that a light sail and what it takes to make it work and how well it works is a little different than what you have in mind.

Rocheworld - Wikipedia, the free encyclopedia

[CraigD]

Originally Posted by Gardamorg

… I will say that the solar sail is going to, EVETUALLY be moving at C. …

I recommend you review special relativity before proposing that anything with nonzero rest mass will eventually be moving at c relative to anything else.

The problem you’ll find is that accelerating a mass to c requires an infinite amount of energy. As there’s only a finite amount of anything available to anything, the best any thrust-based propulsion system can do is accelerate a mass to near c.

From the perspective of the crew of a spaceship desiring only to get from one place to another within some amount of time (eg: here to the Andromeda galaxy in a day), this “cosmic speed limit” isn’t a significant restriction at all – special relativity also predicts a time dilation factor that makes it possible to travel any distance in as little time as desire (as measured by the traveler) given enough energy.

Getting enough energy, and avoiding engineering catastrophes along the way, is, or course, a major challenge.

[Gardamorg]

Originally Posted by CraigD

I recommend you review special relativity before proposing that anything with nonzero rest mass will eventually be moving at c relative to anything else.

The problem you’ll find is that accelerating a mass to c requires an infinite amount of energy. As there’s only a finite amount of anything available to anything, the best any thrust-based propulsion system can do is accelerate a mass to near c.

From the perspective of the crew of a spaceship desiring only to get from one place to another within some amount of time (eg: here to the Andromeda galaxy in a day), this “cosmic speed limit” isn’t a significant restriction at all – special relativity also predicts a time dilation factor that makes it possible to travel any distance in as little time as desire (as measured by the traveler) given enough energy.

Getting enough energy, and avoiding engineering catastrophes along the way, is, or course, a major challenge.

The mirrors reaching 20000 Kelvin will provide THOUSANDS of G's of thrust.

Is that not enough to move at C?

But thanks for the links and advice, I'm going to take advantage of them.

[freeztar]

Originally Posted by Gardamorg

The mirrors reaching 20000 Kelvin will provide THOUSANDS of G's of thrust.

Is that not enough to move at C?

No. To 'move at c', you would have to utilize all the mass in the universe. This simply isn't possible, and if it were, it would make the trip kinda pointless.

I *love* your creativity, Gardamorg! Do not get discouraged by refutations people make here. It's good to have a balance between that which is science and that which is sci-fi.

[Gardamorg]

Originally Posted by freeztar

No. To 'move at c', you would have to utilize all the mass in the universe. This simply isn't possible, and if it were, it would make the trip kinda pointless.

I *love* your creativity, Gardamorg! Do not get discouraged by refutations people make here. It's good to have a balance between that which is science and that which is sci-fi.

Forgive me, but, what do you mean by "Utilize all of the mass in the universe?" Can you explain that thoroughly, I think that would do me more good than Wikipedia's definitions.

Originally Posted by Moontanman

For a very good description of a light sail and how it would work read Robert L. Forward's book Rocheworld. Not only is it a great but R. Forward is a scientist and insists his books follow the science as closely as possible. I think you'll find that a light sail and what it takes to make it work and how well it works is a little different than what you have in mind.

Rocheworld - Wikipedia, the free encyclopedia

My Sail is set up completely deferently, it uses less powerful lasers, but thanks to the way they work, they are much more sufficent.

[Moontanman]

Originally Posted by Gardamorg

Forgive me, but, what do you mean by "Utilize all of the mass in the universe?" Can you explain that thoroughly, I think that would do me more good than Wikipedia's definitions.



My Sail is set up completely deferently, it uses less powerful lasers, but thanks to the way they work, they are much more sufficent.

It doesn't really matter, you could accelerate at millions of billions of gees and still not reach "C" Not going to happen my friend, not going to happen in this universe anyway.....

[Gardamorg]

Originally Posted by Moontanman

It doesn't really matter, you could accelerate at millions of billions of gees and still not reach "C" Not going to happen my friend, not going to happen in this universe anyway.....

Why not, if ten times less thrust can propel the craft at 1/10 the speed of light, why can't ten times more propel it AT the speed of light??

It doesn't make sense.

[InfiniteNow]

As you approach the speed of light, the amount of energy it takes to accelerate further increases.
The closer you get, the more energy it takes, and the more massive you become.
At some point, the amount of energy required to accelerate further exceeds all of the energy in the universe.
This is true for any object with nonzero mass.

This is explained by relativity, which is why it was suggested that you study it.

[freeztar]

Originally Posted by Gardamorg

Forgive me, but, what do you mean by "Utilize all of the mass in the universe?" Can you explain that thoroughly, I think that would do me more good than Wikipedia's definitions.

For a massive object to reach c, it must have infinite energy. Since mass and energy are related, and since we are speaking of infinite energy, infinite mass is implied.

In mathematical terms, when we give c a value of 1, the equation becomes . Thus, infinite m = infinite E. This paradox is resolved because only a particle with a rest mass of zero is permitted to travel at c. Thus, becomes, , which equals zero.

[Moontanman]

Originally Posted by Gardamorg

Why not, if ten times less thrust can propel the craft at 1/10 the speed of light, why can't ten times more propel it AT the speed of light??

It doesn't make sense.

You'll get no argument from me on that point, it doesn't make sense from a common sense stand point but relativistic travel seldom makes sense from our point of view. On way to look at it is this, the closer you to the speed of light the more massive your vehicle becomes. As you pour more energy into accelerating your craft more of that energy goes into making your craft more massive than it does into making it go faster until eventually almost none goes into speed and it all goes into mass. Personally I think your vehicle would collapse into a black hole of it's own making if it got massive enough but any way you look at it nothing made of mass can achieve "C" Not even something as small as a sub atomic particle.