Human spaceships use two major forms of propulsion, both based on fusion-powered direct thrust.

The ion engine breaks down common distilled water into a vapour of hydronium and oxide ions which have a strong electrical charge. The oxygen is recycled to life support. The hydronium is propelled by strong electric fields into a high-speed jet which thrusts the spaceship forward. Since the ions are expelled at relativistic (near-lightspeed) energies, the consumption of water is quite low. However, the accelerator requires large amounts of electricity which must be provided by a fusion power cell. Ion engines are similar to the diesel engines of the 20th century, being cheap, compact and efficient at the cost of relatively poor acceleration and low cruising speed. Most transport ships are powered by two or more ion engines.

The ion engine does not have enough power to land on, much less take off from, a major planet or moon. Those transports which land on planets use secondary chemical or grav-repulsor thrusters.

The fusion torch runs on deuterium (hydrogen-2) which is extracted from heavy water. Liquid heavy hydrogen droplets are compressed by powerful magnetic fields and superheated by laser igniters, causing a controlled nuclear fusion reaction. The shaped magnetic bottle releases a jet of superheated helium and hard radiation.

Fusion torches require strong magnetic containment and large bursts of power to the igniters and control magnets, so the engine itself is bulkier and more expensive. Deuterium fuel is also expensive, although civilian ships require the same fuel for their fusion generators. However, the fusion torch is the usual engine system for military vessels due to its much greater acceleration.

The exhaust of a fusion torch is much more dangerous than an ion stream, so most vessels will also have chemical or grav-repulsor thrusters to manoevre around space stations or land on planets. Gunships (Cutter or Scout-class hulls) do not have the space for thrusters. They are usually catapult-launched from a station or carrier and recaptured using tractor beams.

The Sony Ford Microsoft corporation has recently perfected a microfusion pulse engine for specialised military use. This complex but exceedingly powerful driver manoevres pellets of deuterium, compressed to a metallic state, into the centre of a magnetic shield behind the ship where they are pumped into an uncontrolled fusion reaction. The resulting stream of nuclear blasts hurls the ship forward. Since the magnetic containment is much simpler in shape and the deuterium is allowed to fuse freely, this engine can sustain impressively large fusion discharges.

The major drawbacks of the microfusion pulse engine are the high cost of the unit and its super-compressed deuterium fuel. Its exhaust is even more spectacular and dangerous than a fusion torch. The only design currently using a microfusion pulsar is Microsoft's elite High System Flamer interceptor gunship.

The Fifth Line of t'sa have developed magnetic sail technology. A magnetic sail generator creates a broad shaped magnetic field that meshes with the fields of astronomical objects and the galaxy, powering the ship through space. Magnetic sails require only a sufficiently large power supply. They create acceleration equalling a fusion torch within 5 AU of a star, some gas giant planets, or a Gate. In deep space, their performance is less impressive, but sufficient for transport ships. The highly developed star system of Honnar has a pair of magnetic beacon stations at the Lagrange points of its largest planet, extending the favoured zone for magnetic sails to 10 AU from Honnar's sun.

Because a magnetic sail does not use a hot direct-thrust exhaust, ships using this propulsion system are slightly more difficult to detect, giving a +1 penalty to System Operation-sensors checks.

A magnetic sail is useless within a planetary atmosphere, and dangerous to the electrical systems of other ships and space stations, so most Fifth Line spacecraft also carry grav-repulsor thrusters.

Some specialised t'sa spaceships, such as those used for comet mining, use ion engines similar to human types.