thoughts - the source of all problems and disbalances

[capnq]

consider how a comet's tail always faces away from the sun because of the solar wind (i.e. light) pushing the recently-melted ice particles directly away from the sun

The solar wind is made up of charged particles, not photons.

Momentum transfer from photons is how solar sails work.

[oleg]

Originally posted by Suicide Junkie:
Oleg, your gun could fire two shells in opposite directions and end up recoilless.

Or it could have a really quick-acting thruster on the back to counteract the recoil, maybe along with a sliding mount to give the thruster more time to complete its job.

The trick is to dump the recoil force into some throwaway matter.

Wow ! You can also tie two AK-47 to fire in opposite dirrections. That will make very handy weapon. I think we should patent it and sell for big $$ to Osama.

[oleg]

Originally posted by capnq:

quote:

---

consider how a comet's tail always faces away from the sun because of the solar wind (i.e. light) pushing the recently-melted ice particles directly away from the sun

The solar wind is made up of charged particles, not photons.

Momentum transfer from photons is how solar sails work.

---

The fact that a beam of light has a momentum which is transfered to solid objects upon reflection/absorbtion of light has been established by Russian scientist Lebedev in the end of 19th centuary. The discovery ressurected Newton's theory of particle nature of light and ultimately led to the modern quantum theory.

[Suicide Junkie]

LIM is essentially a circular motor opened out flat. The magnetic field, instead of rotating, now sweeps across the flat motor face.

And magnetism works both ways

In my mind it is hard to imagine it is working in such a fasion that it generates a Recoil

I find it hard to believe anything is recoilless, due to the laws of physics

[ December 08, 2002, 14:45: Message edited by: Suicide Junkie ]

[geoschmo]

The main consideration with recoil isn't going to be it moving the ship around anyway. The vast differences in mass between the projectile and the ship says that the counter force isn't going to move the ship all that much. Certainly nothing that thrusters designed to move the ship around to begin with can't handle.

The main problem is the stresses that are placed on whatever mounting points you have for the gun. Before the force is applied to the mass of the ship as a whole it has to be transfered through the mounting hardware, and it would be very dificult to design a rigid system that could handle those level of loads.

That is the reason the 15in guns on the WWII battle ship recoil like they do. Not because the ship would roll over or anything, but because the counter force would break stuff the first time you shot it if you tried to mount it rigidly.

Geoschmo

[Gryphin]

geoschmo, SJ, and kamog,
Thanks, that all makes sence.
Apriciate the edification.

[ December 08, 2002, 16:15: Message edited by: Gryphin ]

[Baron Munchausen]

Originally posted by Wanderer:
A photon in a laser-bLast (for example) may not have any mass but it still has momentum. Beacuse of conservation of momentum you'll get recoil.

EDIT: For example, consider how a comet's tail always faces away from the sun because of the solar wind (i.e. light) pushing the recently-melted ice particles directly away from the sun.

This page might or might not help:
Link

Actually, 'solar wind' really is a wind. There is a stream of super-hot gas coming from the sun and streaming out into deep space at all times. It's very, very thin compared to the atmosphere that we live in but it still exerts far more force than light. This is the main reason for comet tails.

There was a discussion thread here about solar sails some time back that covered the two different types, too. The shiny/silvery ones are indeed relying on light, but there is also a 'magnetic' sail in development that uses the pressure of solar wind on a cloud of plasma. This has the double advantage of not being degraded by micro-meteor punctures and not losing effectiveness with range from the sun! The density of light is of course reduced at a considerable rate as you get further from the sun (hmm, there's an exact formula that I've spaced). The solar wind also gets less with greater distance from the sun, but the magnetic sail expands as you get further away. It reaches it's 'equilibrium point' based on the pressure of the solar wind itself and produces the same force no matter where you are in the solar system! It would only become ineffective at the 'heliopause' where the solar wind fails completely and you hit interstellar space (which is far beyond pluto).

[ December 08, 2002, 19:27: Message edited by: Baron Munchausen ]

[Wanderer]

Ta, BM. Sometimes I wish I'd studied physics at university rather than copmuter science. Then I remember how much time my physicist friends had to spend in labs whilst I was messing about playing SE3/4.

Geo wrote:

The main consideration with recoil isn't going to be it moving the ship around anyway. The vast differences in mass between the projectile and the ship says that the counter force isn't going to move the ship all that much. Certainly nothing that thrusters designed to move the ship around to begin with can't handle.

That depends - a small ship will only have small thrusters. You'll not veer the ship around crazily with recoil, but you might throw off the aim of the next shot. I guess it depends how quickly your computer/thrusters/aiming system (or SJ's opposite-firing gun) can adapt.

That is the reason the 15in guns on the WWII battle ship recoil like they do. Not because the ship would roll over or anything, but because the counter force would break stuff the first time you shot it if you tried to mount it rigidly.

Yes - very good point. Why didn't I think of that?

Another point is that very large energy weapons will require a lot of power. Would you want a large weapon on a destroyer if you had to turn off shields and life-support to recharge it?

[Gryphin]

Kamog,
Ok, I will accept your statement that there is an opposite and equal reaction in a Linear Induction Motor. Where is the "Opposite" energy being applyed. What is assorbing it? In my mind it is hard to imagine it is working in such a fasion that it generates a Recoil. I also admit that I have no concept of the ammount of energy being used or the mass of the object.
Sidebar: I do know that Linear Induction is used to move Hanger Doors which are masive but very slow.
Here is a link to a site that might explain them. I have to admit I don't follow the explanation of the motors. I guess I have a much more abstract understanding (or lack there of).
Can anybody translate this for me?
http://www.theproductfinder.com/motors/linind.htm
< hmm, I thought I was more technical than this >

[ December 08, 2002, 12:40: Message edited by: Gryphin ]

[PvK]

Well, if you're talking about putting a 90-kT projectile weapon on a 150-kT escort, I think there might really be some recoil problems, especially if the 90-kT weapon is turretted and can face in arbitrary directions. Just rotating the weapon, if it has a non-circular turret or a long barrel, could change the center of gravity of the whole ship.

That was a side-point, though. Again, engineering is about finding efficient solutions to problems, and every decision generally has a tradeoff. It seems reasonable to assume that a huge weapon will be more efficient on a similarly-huge starship design, compared to a small one. Take the opening scene of Star Wars (episode IV) for example. Remember how the Imperial Star Destroyer had engines which appeared larger than the whole Rebel Blockade Runner it was chasing? Looks like those could also generate an immense amount of power which the small ship, given equivalent tech, could never hope to generate. Even if you assume some fantasy-tech devices which generate more power than engines, there is a lot more space, mass, and expense available in the design of the massive ship, compared to the tiny one. It seems pretty likely that the largest and most powerful weapons available will probably make a lot more sense, and work better, on the massive ship design. Not, perhaps, in ALL fantasy-tech, but in general, one would expect it to work out that way. If you want to model a tech that makes that untrue, SE4 of course allows it (woo-hoo! ), but all else being equal, I think if a single weapon is becoming a major percentage of the whole ship design, it's going to present some engineering disadvantages of one sort or another.

PvK