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Re: Summarry of the momentum wars and idea.
On Sat, 2 Dec 1995, Steve VanDevender wrote:
<long discussion about gravity, work and power deleted. sorry kelly, got
to side with steve on this one.>
> > S >> My intention was to prove that Kevin's parasail design
> > S >> couldn't absorb photons without absorbing their
> > S >> momentum.
i now accept this point as proven.
> You can reflect different parts of the beam in different
> directions to produce sideways components of momentum that cancel
> over the entire structure. You cannot take forward momentum and
> turn it into sideways momentum without giving the forward
> momentum completely to something else. When I say that momentum
Okay, let's think about that for a moment. Is it possible to absorb the
photons into the Reaction Mass (RM), giving all of the energy _and_
momentum to the exhaust stream. since the exhaust stream consists of
(ideally) the recieved photons and extra mass, would this slow the system.
Half formed idea follows: (modifications/analysis welcomed)
ship's core /"/
Power from Sol ______________/"/________
~~~~~~~~~~~~~~~~~~~~~~============"="="="="="="="="="" exhaust and power
~ Photons going one way
= photons going both directions (canceling? hope not)
" Reaction Mass
Of course this assumes we can aim a maser straight up the butt of the
ship over light years, which of course we cant. But, numerous
reflections could collect the energy over square kilometers, and focus it
in the required manner, producing the same net result. If your objection
is to this paragraph, then hold your horses, because I'm dubious about
this part myself. remember, I just thought this up about 20 miuntes ago
(as I'm writing this) so there may be a few bugs
my question is this:
does the ship slow down?
I think it should. (but I've been wrong before) before the interaction,
the ship and the RM were traveling to the right with some speed V. after
the interaction, the RM is traveling at a greatly increased speed to the
right, and the photon beam is traveling to the left. (complete reflection
-- don't ask me how, just assume it for the moment.)
Now absorb the photon beam and convert it to electricity.
(the ship should act as though the photons came from Tau Ceti, slowing
even more.) -- again, we either need a magical one-way absorber at the
~/= interface (~ photons enter from the left, = photons are absorbed from
the right), or a complicated series of reflectors. or we have to abandon
the photons capture and just let all that lovely energy zing back to earth.
the electricity (if we can capture it) can then be used to power a lineac,
acellerating the plasma stream even more. which definitly would slow the ship
I think this is what Kelly was trying to get at with his plasma mirror,
but this puts the mirror inside the ship. I realize that I'm talking
about some very very complicated twists and turns, but just answer the
following question. is this system physically possible? does it
preserve momenergy, and does the ship slow down. we can worry about the
merely difficult engineering tasks later.
> is a vector quantity and is conserved as a vector quantity, what
> I mean is that if you have a quantity of momentum, its direction
> is as important as its magnitude, and although you can divide the
> momentum up however you like, even split zero components into
> complementary non-zero components aimed in opposite directions,
> the sum of all the momenta of all the things you divide it up
> among sums to momentum in the same direction with the same
here's how I see it breaking down,
1 photons reflecting off RM:
Momenergy (very dangerous of me to toss a word around that I don't fully
understand.) conserved by acceleration of RM. Ship slows down a little or
not at all (photons momentum equals RM momentum and ship stays the
same??? but ship now has less mass <very confusing>)
2 reflected photons absorbed:
Momenergy conserved by ship slowing down.
3 electricity used to further accelerate RM. ship slows down even more.
I cannot begin to solve the math showing how much the ship slows down, or
how much energy is required, or how much RM is required. I'm not even
sure the physical model is correct.
PS, I do appreciate your kind tutuledge Steve, I know it must be
frustrating trying to pound knowledge into a head as thick as mine,
especially through such a small bandwidth channel like this.