Re: Gravitic focussing

[email removed] (Stephen Camp) writes:
>
> My gripe or gripes mainly has to do with 'gravitic focusing' of lasers.
> ....
> Now I went futzing around with some basic physics equations:
>
> Law (?) of Gravity
>
>                (m1)(m2)
>       F  = -G ---------  where G = 6.672E-11 Nm^2/(kg^2)
>                  r*r
>
>
> Einsteins Equation  :   E = mc^2
>
> I wanted to see how much energy (E) it would take to replace m1 by E/(c^2)
> to create a gravity point source that would exert 1g acceleration at 1m
> distance.  I came up with 5.09 x 10^21 (!!!) Joules.  That becomes Watts
> if it's over time.

I don't know how the analysis should go, but that looks *extremely* dodgy.
For one thing, that figure doesn't seem to take any account of the mass of
the object being accelerated, and the day someone figures out how to
supply 1G acceleration to 10,000,000 kg of mass for the same amount of
energy as it takes to supply 1G acceleration to 0.0000001 kg of mass is the
day that someone is going to figure out how to make free energy.  For another
thing, you can't interchange Joules and Watts that easily, as someone found
out a few threads ago (remember the stuff about computer power consumption? :-)

> However, how much gravity (mass -> energy) does it take to bend light?  All
> I can recall is Mr. Spock telling Cpt. Kirk that the selective bending of
> light is extraodinarily expensive.

True, mainly because light moves very fast, so to do anything significant to
its path you need a lot of acceleration, i.e. a lot of gravity.  I for one do
not intend to be in a spaceship anywhere near a gravity well capable of doing
something useful to a light beam!

> However, since they stated they can "create an intense point source of
> gravity", then why not have 'impulse drive' for system travel.  It's the old
> idea of space being a fabric, that a gravity well is like pushing a finger
> down in the fabric thus creating a 'well'.  Put a marble on the fabric, close
> enough to your finger and the marble will fall into the well.  Now, since
> we can "create an intense point source of gravity", why not just project
> it out in front of the ship.  By shifting the gravity point source around
> the ship, we can change our direction.  By intensifying or lessening the
> source, we change the  magnitude of our acceleration.  And if we can
> do this, why the need for all that reaction mass?

Newton's 3rd law puts a stop to that.  If the gravity generator is exerting
a force on the ship, then the ship is exerting the same force on the gravity
generator.  Whatever is holding them apart is going to have to be pretty
tough if it isn't going to get squashed.  And if it doesn't get squashed,
then neither the ship nor the gravity generator are going anywhere.  You
don't need a hefty gravity generator to play this trick, anyway - an iron
hull and a large magnet will behave the same way.

> If gravitic focusing really throws their system out of whack, I guess I'd
> rather have beam weapons restricted in range to tens of thousands of
> kilometers.  Then you'd have to get close to do some damage, or you'd
> have to rely on missiles more.

Delete everything before "I guess" in the above paragraph, and you get my
preference. :-)

- --
 "Keyboard?  How quaint!" - M. Scott

 Adrian Hurt			     |	JANET:  [email removed]
 UUCP: ..!uknet!cee.hw.ac.uk!adrian  |  ARPA:  [email removed]