Only three things have been constant about the FTL drive in my setting, Flat Black
. It has always functioned on ships in space. It has always destroyed planets if you used it wrongly. And it has always been called "the Eichberger drive".
In the first version of the material it was just the IS drive from the starship rules in ForeSight
. An instantaneous jump drive that worked best at a distance from all stars of 25AU times their mass in solar masses, which got more difficult and dangerous to use with increasing range, and which had its performance degrade after uses (especially long jumps) until it was overhauled using costly parts. Its characteristics implied the use of "outwell" ports, with non-interstellar ships shuttling passengers and cargo between up-port and out-ports as well as orbital lighters shuttling them between down-ports and up-ports. I didn't like the out-well facilities very much, it didn't lead naturally to the lost colonies that I wanted, and as I figured out how to optimise its use I found that most of the human sphere of settlement in "Flat Black" was within one Jump of the centre. The travel time to a colony depended on the mass of the original and destination stars, not on their relative location. That meant that no colony was as remote as I wanted some to be, and it led to government and manufacturing being too much dominated from the centre, with a hub-and-spoke arrangement.
The second version was another instantaneous jump drive, but it forced ships to go to a different place to get to each possible destination, and made the point of arrival uncertain, thus making out-well ports impractical. Ships had to put energy into their drives sufficient to overcome their gravitational binding energy to any nearby stars &c.; drives had limited storage capacity proportional to their mass, and were expensive. Thus a high-spec ship could jump from closer to a star than a cheap or lower-TL one could. On jumping, ships travelled instantaneously along lines of net gravitational force opposite to that they would have accelerated in, and re-appeared at the first point with equal gravitational potential to their starting point. Another reason for moving out into the Black before jumping was to reduce the significance of errors in position. That version did away with the out-well facilities, but when I crunched the numbers it turned out that navigational risk was nowhere near forcing prudent jumps to be short compared with the radius of settled space. Also, an astute reader pointed out that that made it much easier and safer to jump Coreward than Rimward, because of the Galaxy's gravitational field potential.
To make sure that I got the sense of astrography I want, to make the old worlds in the Core central and the new worlds on the Frontier remote, I decided to cut down drastically on the among of realspace travel at the beginning and end of each trip, and to make travel between the stars slow rather than instantaneous. I ran a planet generator over a star catalogue to figure out how big the sphere of settlement has to be to contain the number of worlds I want (one thousand worlds implies a radius of 180 light-years), then figured out how fast ships have to travel to make the frontier as remote as I want it to be. I reckoned that I want ships to travel at a speed in the ballpark of 1,000 times lightspeed to one parsec/day.
In the old days spaceships were designed using ForeSight
rules, and optimising the design of second-version ones meant adjusting the ratio of IS drive mass to ship mass to alter the duration of trips by controlling the minimum distance from a star that the ship had to be at to jump. Unfortunately, OS and software upgrades have left me unable to open the old design spreadsheets. Meh! Comparisons are odious, I guess. I'm going to investigate the new version of Eichberger Drive performance using the design rules in GURPS Spaceships
, and then see about adjusting things to suit my needs. The Eichberger Drive as currently imagined is a "hyperspace" drive in GURPS
terms, and the desired speed of 1,000c is close to FTL-1 (i.e. one parsec per day, 1,191c), not that that matters.
This is where I'm starting out from.
- An Eichberger Drive requires FTL-1, i.e. one stardrive system per ship. I'll adjust drive sizes if I need to after doing some investigations.
- I'll start with the drive costs suggested by GURPS Spaceships and adjust if I need to to get the effects I want.
- This is like the Quantum I/Quantum II hyperdrive in Niven's Known Space: all ships travel at the same speed in hyperspace: bigger drives and higher tech ones don't help that. I'll eventually make the cost or mass of drives a diminishing function of tech level, but fiddle with that after preliminary investigations.
- To operate its drive, a ship needs to be gravitationally un-bound from the nearby planet and star, i.e. travelling at the joint escape speed, but the direction of travel doesn't matter.
- Momentum is restored on arrival, meaning that the ship needs the drive performance to deal with differences in the stars' space velocity as well as orbital speeds of the planets. Total delta-vee requirements are in the tens of kilometres per second. Trading off before-jump velocity and after-jump deceleration requirements is a problem for starship navigators, not PCs.
Any comments? Am I overlooking something that is going to come back to bite me?