Choosing 4E Spaceship Propulsion

[gruundehn]

Seneschal, the A. Bertram Chandler drive system required that real time passed whie travelling. The plot of one story involved a ship where the forward and backward time rates were the same and the ship became trapped. So as the ship travelled forward in space there was a period of time that elapsed between the start and end of the voyage. The "backwards in time" rate was never mentioned that I recall so the time of a voyage was whatever was required by the plot I guess. Combat could not take place when a ship was under the drive since firing a weapon would affect the ship's mass and thus upset the drive.

[Seneschal]

Originally Posted by gruundehn

Seneschal, the A. Bertram Chandler drive system required that real time passed whie travelling. The plot of one story involved a ship where the forward and backward time rates were the same and the ship became trapped. So as the ship travelled forward in space there was a period of time that elapsed between the start and end of the voyage. The "backwards in time" rate was never mentioned that I recall so the time of a voyage was whatever was required by the plot I guess. Combat could not take place when a ship was under the drive since firing a weapon would affect the ship's mass and thus upset the drive.

Heh, with the precursor alien supertechnologies I'd like to have all over the setting, something like this would be a nice dungeon to throw the players into, just to see them panic when they realize the ship is time-travelling. Then in harmlessly dumps them halfway across the galaxy.

Also, I've decided to utilize something along the lines of Fred Brackin's boost drives, and wrote a short description. I realize there must be a scientific blunder in there somewhere to allow for a reactionless drive at all, but I'd rather put it up here to be corrected than to be mercilessly savaged by my nitpicky players. So, if anyone could kindly savage me beforehand, I'd greatly appreciate it!

Pseudovelocity (PV) drives are essential for quick intra-system travel since they circumvent classical rocketry and Newton’s laws of motion by moving the ship without consuming reaction mass. Once engaged, their strip the ship of its rest mass, making it immune to acceleration effects and unable to accumulate any kinetic energy; it can instantly achieve light-speed, maintain it as long as it has power (every PV system requires a Power Point to function), and come to a full stop just as quickly; applying any kinetic force to it will only harmlessly stop it in its tracks, making projectiles and missiles completely useless. Radiation and energy (including lasers and massless particle weapons) can still cross the field.

As a massless, inertialess object, the ship should travel at light-speed as easily as a photon, however, it is stopped several thousand times per second by colliding with the interstellar medium (by default 1 atom of hydrogen per cubic centimetre), but "recovers" quite quickly by engaging the drive again. This "stuttering" limits its actual speed to 400-1000 mps. Multiple PV drive systems and high-quality ones have higher response times, which in turn increase overall speed. Atmospheric pressures above Trace (e.g. 200 km above Earth’s surface) completely prevent the drive from functioning. Once the PV drive is turned off or loses power, the ship loses all its pseudovelocity and regains the speed it had before engaging the drive.

How the drive goes about stripping rest mass from stuff I'd basically handwave. Maybe it blocks all Higgs bosons or turns half the ship into negative matter with negative inertia or something.

The stuttering effect is essentially bollocks to prevent everyone from always traveling at c. ~500 mps is a nice casual speed, and it can be improved to allow for "fastest ships in the galaxy" and stuff.

I'm not sure about the no-kinetic-weapons thing, though I like the implications that Fred mentioned - lasers, maybe some particle beams, EMP torpedoes and nuke-pumped x-ray lasers become essential, and massive-scale kinetic bombardment is averted; plus, ships become more like battleships and less like kamikaze. But I'm having trouble imagining how this scenario would unfold: a projectile collides with a massless ship with, let's say, 100 KJ of energy - and then what? Does it do damage? Does the ship just lose all its velocity? Does it go careening off cartoonishly to the side?

[Fred Brackin]

Originally Posted by Seneschal

But I'm having trouble imagining how this scenario would unfold: a projectile collides with a massless ship with, let's say, 100 KJ of energy - and then what? Does it do damage? Does the ship just lose all its velocity? Does it go careening off cartoonishly to the side?

I just say that collision is impossible. The "mass" of the PV ship has been shifted out of the normal universe with only a partial interface with the normal universe left behind. The thing the nomarl matter object would collide with isn't there. At most the PV ship deflects just enough to pass around the object.

[Seneschal]

Originally Posted by Fred Brackin

I just say that collision is impossible. The "mass" of the PV ship has been shifted out of the normal universe with only a partial interface with the normal universe left behind. The thing the nomarl matter object would collide with isn't there. At most the PV ship deflects just enough to pass around the object.

Yeah, I guess if I introduce a phlebotinum mass-altering field, I might as well give it properties like that.

I also realized that kinetic projectiles wouldn't be useful against boost drives anyway - they all have a flat +3 to Handling and can turn on a dime, making all precision shooting useless. Also, when a projectile leaves the inertia-cancelling field, I don't see how it would retain the pesudovelocity, and would probably be left behind floating in space behind the ships.

[gruundehn]

In the Lensman series E.E. Smith said that physical weapons like missiles and slugs would not affect an inertialess ship unless the firing ship and the target ship were rigidly held together. This was in Galactic Patrol I believe. I'd give a specifif reference but I loaned my books and the guy moved to Flordia with them. I haven't replaced them yet. Damn, I hate it when that happens.