Considering the notion of ion thrust as being one of the most likely saviors of fusion-powered propulsion, it seemed a good idea to review the state of that tech. The wiki site (1) gives useful data on the results of current ion-drives for light-weight spacecraft.
From the wiki site (1), we see that :
"The Deep Space 1 spacecraft, powered by an ion thruster, changed velocity by 4.3 km/s (9,600 mph) while consuming less than 74 kg (163 lb) of xenon. The Dawn spacecraft broke the record, with a velocity change of 11.5 km/s (26,000 mph), though it was only half as efficient, requiring 425 kg (937 lb) of xenon."
The three ion thrusters for Dawn were running for over 200 days to obtain that velocity (2). They are slow but efficient. Humans are neither, and for good reason. We do not want to spend a lot of time in space getting hammered by cosmic radiation, etc.
It appears that Xenon based thrusters is the current tech (1) :
"Ion thrusters in operational use have an input power need of 1–7 kW (1.3–9.4 hp), exhaust velocity 20–50 km/s (45,000–112,000 mph), thrust 25–250 millinewtons (0.090–0.899 ozf) and efficiency 65–80% though experimental versions have achieved 100 kilowatts (130 hp), 5 newtons (1.1 lbf)."
It reminds us that thrust is measured in Newtons (a measurement of force), and gives some interesting details and how ion thrust may apply to our fusion-based spaceship, with so much energy from so little mass. There must be a way to make it work, right?
It is clear from the above details one would have to ionize a lot mass of some element(s) and feed it into a "Thrust Plasma Stream" heated by our fusion reactor, which then exhausts it at relativistic speeds to get our spaceship moving quickly, to an acceptable velocity, and slow it quickly, such as for an orbital insertion.
Still, what is the "fuel" that is to be ionized and exhausted, and how would that be done considering the temperatures involved? We must form the ultra-super-heated "drive plasma" from fusion energy, and then vent these ionized particles at relativistic speeds. It would seem to present a substantial design effort, to say the least.
Alternatives are more then welcome!