scales and drives was Re: [FTFB] Not ships, exactally. . .

[time to roll the subject field, i feel]

> On Sat, 13 Feb 1999, John M. Atkinson wrote:

> Keith Watt wrote:

a photon drive is within the understanding of modern physics, and pretty much
within the reach of modern engineering, too. it doesn't use extra reaction
mass at all. buzz aldrin and jonh barnes suggest in "Encounter
with Tiber" that such drives could be powered by zero-point energy
recovered through the Casimir effect (which is some freaked-up quantum
physics thing which sort of makes sense) - thus, not only would you not
need reaction mass, you'd not need fuel either.

> I strongly prefer

well, even at 0.01g, you only need to get from the planet to the jump point,
so you wouldn't need generation ships for interstellar travel. still, i get
your point.

> I havn't worked out the exact scales I'm using, but 1

eh?

thrust 1 for 1 turn gives speed 1. if thrust 1 is 10 m/s2 and 1 turn is
60
seconds, then final velocity is 600 m/s. 600 m/s over 60 s is 36000 m.
that's 36 km, not 1000. or have i just paid the price for forgetting to eat
today?

if the turn were 5 mins long, then 1 thrust = 10 m/s2 would get you 1 mu
=
900 km, which is close. if the turn were 5 minutes, 15 seconds and 260
milliseconds, i believe that we'd be bang on. or we could have 1 thrust
=
11.11 m/s2, 1 turn = 5 mins and 1 mu = 1000 km.

possibly the best option is 1 turn = 10 mins, 1 mu = 1000 km and 1 thrust
= 2.78 m/s2 (about 1/4 g), as has been suggested. thus, a standard heavy

warship accelerates at one gravity, and a fast scout at two. this is
convenient for cruising - if a ship cruises at full thrust (arguable),
the crew have a nice natural 1g to stand up in.

note that this analysis does not use Newtonian physics, but rather the
slightly modified Tuffleyan physics, where distance travelled is equal to time
multiplied by your final velocity, not your average velocity. that's how it
works in cinematic movement, anyway. not sure about this
new-fangled vector stuff.

it would be nice to fix this little bug in the movement system for those who
continue to use cinematic. how about saying that half the acceleration is
applied at the start of the turn, and half at the end? alternatively, that
acceleration is applied twice, once at the start and once at the end of the
turn. these two are basically equivalent.

another alternative would be to PSB our way out - say that ships in the
tuffleyverse use orion-type nuclear pulse engines, and apply all their
acceleration in one go, once every turn. the attractions of 1 thrust = 0.25 g
start to go away when you realise that you're actually getting 150g for one
second each turn. ouch.

Tom