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Old 07-22-2018, 01:21 PM   #1
cptbutton
 
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Default Drives IMTU

This is how I am planning to do ship drives IMTU. Yes, I am changing canon. Or cherry-picking from it to suit my sensibilities. Benefits are: A reduction in the level of screaming from my inner physicist. Keeping any spaceship from being a WMD, or at least making it harder to manage. Justification for the nozzles on the back of ships.

(I am writing this largely to organize my own thoughts, but I figured I'd put it up here for comments and discussion. Mostly interested in comments about implications I have overlooked, or suggestions for tweaks.)

Most ships are powered by Fusion+ sealed units (TL10). The Imperium and many other societies intentionally sell these cheap. They can't be made to explode easily.

Jump drives (J-drive) (TL10) use jump "fuel" that is slowly released over the course of a week in jumpspace. It maintains a tenuous hydrogen atmosphere between jumpspace and the ship. Bad things happen if the ship structure touches jumpspace. Think of it as a protective lubricant.

This means you don't have jump capacitors or drop tanks IMTU. You can have strap-on tanks that you take through jump with you and then jettison, but that is expensive since the tanks need their own jump grids to connect to the jump drive, and the ship's jump drive is bigger and more expensive that it would otherwise be.

Artificial gravity is done with grav plates which create gravity within the enclosed volume (TL8). Standard units provide anything from 0-2Gs, with relatively slow changes (a minute or two). Sudden total loss of gravity is caused by serious damage to the equipment, or by deliberate override which causes serious damage. For higher Gs or to play grav pong you need substantially more expensive equipment installed.

Anti-gravity (TL10) is just weight negation (but not mass negation). To move you need a source of thrust.

Maneuver drive (M-drive) (TL9) moves a ship through space without perceived acceleration. It does not create kinetic energy. If the drive field around the ship hits large amounts of matter the breakers pop or the drive explodes or melts down. Any increase in potential energy is provided by the ship's power plant. Any decrease in potential energy turns into heat. When the drive turns off the ship resumes the intrinsic velocity it had before the drive turned on*.

To change your intrinsic velocity you need a source of thrust, or to play games with M-driving into a gravity field, turning off the M-drive while you fall, turning it back on to climb up, etc.

Thrust engines (T-drives) exists in a myriad of forms at different tech levels, but most starships use a standard type which uses power from the ship's power plant to heat up reaction mass and shoot it out a nozzle in the desired direction. The reaction mass is usually the surrounding atmosphere, or onboard hydrogen, although other onboard types of reaction mass can be used. This exhaust is often very hot, but a cooler mode is available so you can land in the bush without starting a forest fire.

The acceleration from T-drives is experienced normally, there is no easy way to counteract it.

(Air rafts and such also need a source of thrust besides their anti-gravity.)

Yes, these means ships have three kinds of drives, not two. For purposes of skills, feats, etc, any of them apply equally to M-drives and T-drives.


* Yes, I know I am creating a preferred reference frame, and time travel. I have a waiver here signed by Aristole, Newton, Einstein, Hawking, Cochrane, and both Popes. Go away.

(Yes, it is somewhat like the stutterwarp from 2300 AD, though I am largely cribbing from Poul Anderson.)

P.S. IMTU t20 ru ge 3i c jt-- au ls pi+ ta- he+ kk? hi+ as- va- dr Ith Vir+ ne so- zh da+ sw- sy
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Old 07-22-2018, 01:56 PM   #2
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Default Re: Drives IMTU

Any practical interplanetary ship is inherently also a potential WMD. You cannot escape that and still be realistic. Crash a 2nd stage from a Falcon 9 into a major or semi-major city, and thousands will be injured from the blast and resulting fires. Even if it were filled with only water, it's going to have a nasty load of kinetic energy, simply to overcome gravity for a suborbital path like the 1st stage has.

Hit a small town, it may only be hundreds, but it's still going to do damage much like an FAE, and those are now banned as WMDs.
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Old 07-22-2018, 02:17 PM   #3
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Default Re: Drives IMTU

Quote:
Originally Posted by ak_aramis View Post
Any practical interplanetary ship is inherently also a potential WMD. You cannot escape that and still be realistic. Crash a 2nd stage from a Falcon 9 into a major or semi-major city, and thousands will be injured from the blast and resulting fires. Even if it were filled with only water, it's going to have a nasty load of kinetic energy, simply to overcome gravity for a suborbital path like the 1st stage has.

Hit a small town, it may only be hundreds, but it's still going to do damage much like an FAE, and those are now banned as WMDs.
True, but a WMD that can destroy a small town or badly damage a city is not nearly as bad as a WMD that devastate continents and cause ice ages.
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Old 07-26-2018, 03:20 PM   #4
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Default Re: Drives IMTU

Where does the heat from dropping potential energy with the M-drive end up? In a specific location? In the ship's drive?


Anti-grav only between enclosed plates is a nice touch.
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Old 07-26-2018, 09:32 PM   #5
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Default Re: Drives IMTU

Quote:
Originally Posted by ericthered View Post
Where does the heat from dropping potential energy with the M-drive end up? In a specific location? In the ship's drive?


Anti-grav only between enclosed plates is a nice touch.
It ends up in the M-drive machinery. The usual practice is either to have radiators out on the hull or use it to heat reaction mass and shoot it out the nozzles. This does change the ship's intrinsic velocity. The pattern of distribution of the reaction mass as it leaves the drive field can be a bit odd.
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