Antimatter Propulsion

Propulsion using antimatter rockets

Robert Frisbee antimatter ship
Image from Steve Bowers
The Robert Frisbee, an antimatter ship of the middle Federation age. The drive system is located as far as possible from the crew section, because of the dangerous gamma rays emitted by the antimatter reaction; shielding at this time was relatively inefficient.
These drives are the ultimate possible for unassisted modosophont technology. All practical antimatter drives are internal drives, as antimatter is far too expensive to use in a wasteful manner.

Antimatter production

Can be gathered from the magnetic fields of planets and stars, where it is formed by natural high energy processes; alternately it can be creted in vast amat farms.
More on antimatter production
dragonfly
Image from Steve Bowers
The Dragonfly Ship, with its large wing-like radiators and rows of massive Penning Traps, demonstrates the difficulties of using Antimatter as a power source.
It was not until the First Federation period that the advances in ultratech made it possible to replace the inefficient early amat rockets with a far more efficient augmented design, in which much more of the energy of annihilation could be used for thrust.

These so-called Beamed Core drive ships, although widely used for both military and commercial purposes during the first federation era, were hopelessly outclassed by the development of the transapient Conversion Drive. However, the high-tech requirements and great cost of these drives, mean that many impoverished or luddite groups and clans are unwilling or unable to use Conversion technology. Hence there are still more than a few minor empires and clans in the outer volumes which retain the old style amat rocket, not to mention those isolated worlds that do not have access to the Conversion drive, and there the Matter-Antimatter drive is often still in use.

Performance

Almost any boosted fusion drive can be run in a pure antimatter mode, and almost any antimatter drive can be augmented with some fusion fuel or other reaction mass. In general, boosting or not boosting a drive involves trading Isp for thrust. Drives used in gravity wells are usually heavily boosted, while drives used for deep space travel are usually run as pure antimatter drives. Boosted drives usually have Isps between 1,000,000 and 10,000,000 seconds, a thrust to weight ratio of 20 to 1 or better, and a total delta-v of 10,000 to 80,000 km/sec.

True antimatter drives include a number of different types, which are superficially similar to the various types of Fission drive in that they are determined by the state of matter in the reaction chamber. Types include solid core, gas core, plasma core and beam core- the last of which is the most powerful and has the most rapid exhaust.

An antimatter drive can have an Isp close to the maximum physics allows, 30,000,000 seconds, a thrust to weight ratio of 100 to 1 or more, and a total delta-v of 150,000 km/sec. These last figures lead to the classic specifications for the ancient "AMAT Clippers", namely, for a launch mass that was one quarter antimatter and one quarter reaction matter, you could reach 0.25c on both legs of a round-trip journey without refuelling. Adding a ramscoop to such a design improves the range and performance considerably, and such designs are the earliest ones to break out of the Low Speed flight regime and into the High Speed flight regime.

Timeline

291 AT- First manned Solid Core Antimatter drive spacecraft (pursuit vehicles)
580 AT - First manned Gas Core Antimatter drive spacecraft
1020 AT - First manned Plasma Core Antimatter drive spacecraft
1120 AT - First manned beamed core Amat Propulsion drive spacecraft with gamma reflection system
 
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Development Notes
Text by M. Alan Kazlev, Mark Mcamuk, Chris Shaeffer
some comments by Steve Bowers
Initially published on 08 December 2008.