Fusion Drive

 

A fusion rocket is a rocket that is driven by a fusion core. The process of nuclear fusion has traditionally required huge terrestrial facilities, but developments in the 22nd century of smaller and lighter fusion reactor, has led to the development of fusion powered spacecraft. For space flight, the main advantage of fusion is the very high specific impulse and the ability to use abundant materials such as hydrogen or water as propellant. In addition, a fusion rocket produces far less radiation than a fission rocket, reducing the mass needed for shielding and the amount of radioactive waste produced.

The Basic Fusion drive
The Fusion drive uses heat from a fusion reactor to heat and eject a fuel. Depending on the type and efficiency, that gives a specific impulse of anywhere from a few thousand to a hundred thousand or more. These ships really kick started the Interplanetary Age.
Fusion rockets are huge and heavy devices, but, they are the only drive systems that give enough Δv for truly practical for system-wide operations.
Basic Propulsion: Reaction
Specific Impulse [sec]: 10 4 to 10 5
Thrust-to-Weight Ratio: 10-5 to 10-2
Fuel: D-T or D-3He
Reaction Mass: hydrogen, water
Used for: Interplanetary transport
Construction Costs: high (bulky, precision materials)
Advantages: reasonably reliable, good performance, can be made with materials in most solar systems
Disadvantages: Interplanetary only, complexity & size
Normal Acceleration: 0.05 to 1.0 g
Normal Top/Cruising Speed: 100 - 150 km/sec (interplanetary haulers)
ElectroFusion Drive
Many spacecraft propulsion methods such as ion thrusters require an input of electric power to run and are highly efficient. Their maximum thrust is limited by the amount of power that can be generated. An electric generator that ran on fusion power can be installed purely to drive such a ion thruster ship for very prolonged periods.
It was an Electrofusion drive that powered the first interstellar spacecraft from Terra.