Jerry Williams ([email removed]) writes:
> Adrian Hurt [email removed] writes:
> >
> > > On the other hand, GmM/r is the escape energy of Sol,
> > > which is the kinetic energy required to produce a velocity of ~30 km/s.
> > > For a ship weighing say, 1 T, that's 4.5e11 J, or 450 000 MJ. Not to
> > > be sneezed at.
> >
> > A ship accelerating at 1-G will achieve that velocity in less than an hour,
> > using just its manoeuvre drive.
>
> Perhaps that is one answer -- require all ships entering jumpspace to
> have enough kinetic energy (speed) to escape from the local star's
> gravity well. Then, a ship jumping from Sol to empty space would end
> up with (almost) no kinetic energy after the jump, then after jumping
> to Alpha Centauri it would gain as much kinetic energy as potential
> energy that it lost.
Of course, things don't balance out quite so neatly when the destination
star has more or less mass than the departure star. Maybe part of the jump
calculation involves arranging that you exit jump space at a distance such
that the escape velocity from the destination star at that distance, is equal
to the escape velocity from the departure star at the distance at which you
entered jump space. Using distance from the star to balance out the different
mass of the star ensures that the escape energy at each end is about the same,
and the jump drive doesn't get overloaded trying to compensate for the
different energies.
The jump drive would then convert the ship's kinetic energy into jump energy,
and back again when the ship exits jump space. Kinetic energy would probably
be meaningless or totally different in jump space.
> Of course, there will have to be extra energy expended for the jump
> itself. Probably that energy would be expended as lost heat energy
> or something.
That's accounted for by the huge amount of fuel which has to be burned by the
jump drive.
When you exit jump space ...
> As I mentioned, the energy could just as easily be transferred into
> kinetic energy. Or it could go into the jump capacitors. As long
> as you aren't getting free energy from the jump, I don't mind how
> it is modelled.
And now you know why you have to be at least 10 diameters away from the
planet before you jump, preferably 100 diameters. (And probably some
significant distance away from the star, too.) If you're too close to
a gravity source, the jump capacitors or jump drive get overloaded. Boom.
And now for something completely different:
James T Perkins [email removed] writes:
> Subject: (3337) Comment on Classic Traveller
>
> A funny thought. On my X-windows display, the configured icon image for
> my shell windows is an Imperial starburst, not a shattered sun ala
> MegaTraveller.
Use the shattered sun to indicate when something goes wrong. :-)
- --
"Keyboard? How quaint!" - M. Scott
Adrian Hurt | JANET: [email removed]
UUCP: ..!ukc!cs.hw.ac.uk!adrian | ARPA: [email removed]