Various people have been posting about manuver drives and how to make
them obey physics without changing the system too much. I spent a fair
amount of time working on this last January, and posted some of the
results. I'll summarize to conserve bandwidth. My basic feeling is
that conservation of energy is worth fighting for, even if other physics
violations are used.
It is IMPOSSIBLE to have a truly reactionless drive that does not
violate conservation of energy. This follows from the principle of
relativity and the fact that reactionless drives by definition violate
conservation of momentum. I can post a proof if there is sufficient
interest or disbelief. It is possible to have a "pseudo-reactionless"
drive similar to grav thrusters. The assumption needed is that the
vehicle with the drive is using it to push on the planet (or whatever)
just as if it had wheels and was in physical contact, conserving
momentum. In order to conserve energy, however, the energy required to
accelerate at a fixed rate is going to rise steadily as the vehicles
velocity increases.
Example: A grav car massing 1000 kg that starts at rest accelerates at
1 meter/sec^2 for 10 seconds, giving a speed of 10 meters/second and a
kinetic energy of 50,000 kg m^2/s^2 = 50,000 joules. This is the amount
of energy that must be provided to the drive assuming 100% efficiency.
Now assume it accelerates for another 10 seconds at 1 m/s^2 (same
acceleration for same amount of time). It is then is moving at 20 m/s
and has a kinetic energy of 200,000 joules for an increase of 150,000
joules, which must be provided to the drive.
A plausible way for the drives to work is assume that they have a
maximum power, and the acceleration thus drops as the vehicle's speed
increases. Also, some power input should be required to hover, even
though none is theoretically required, since the velocity is not
changing. This "coupling energy" could rise as the vehicle gets farther
away from the planet, since the gravitational field is getting weaker.
The starship thruster plates could have a coupling energy that would not
depend on distance, as before. Note also that braking would require NO
energy, and in fact you could get energy back (regenerative braking).
One point that has been raised is the potential playability problem if
the formulas for acceleration are "too complicated". Actually, they
will be much simpler than similar formulas for finding the acceleration
of an ordinary automobile (ever wonder why they give the acceleration as
0 to 60 in x seconds?), as well as being simpler than a rocket (mass
isn't changing).
I am working on a set of rules for manuver and grav drives based on the
"pushing against a planet/star" idea and I'll post them soon.
Sincerely,
Guardian of Energy Conservation
W. Dow Rieder
When the only tool you have is a hammer, all your problems
start to look like nails...