Fusion "Torch" USVs

"Single stage fusion rockets will be able to achieve velocities of 30,000 kps and more. At even a fraction of this velocity, the solar system will be a very small place." - Marshall T. Savage, The Millenial Project

Fusion Torch USV

Fusion “torch” drives differ from the fusion-pulse (Daedalus) drive featured elsewhere on this site in that a fusion reactor is used to super heat reaction mass (water, liquid hydrogen, methane, etc.), producing very high exhaust velocities. Specific impulse for a fusion torch in GURPS: Transhuman Space is around 14,400 seconds for a “high thrust” drive and 36,000 seconds for a “high impulse” drive. Researchers at the University of Michigan have suggested that a specific impulse in excess of 100,000 seconds may be obtainable with future fusion rockets.

Not Very Compact: Small fusion drive spacecraft designs are more science-fiction than the other propulsion systems discussed in GURPS: Transhuman Space. While fusion drives are certainly in the realm of possibility, "small" fusion-driven vessels like the Mudlark probably aren't likely to be available anytime in the foreseeable future. Actual fusion drives - and the vessels they propel, will most likely be very large. For example, the mirror magnets for a fusion rocket would weigh around 400 tonnes (metric tons), about 16 times a single Space Shuttle payload. The heat radiators would add another 240 tonnes. A "compact" fusion rocket engine would be a whopping 144 feet long - larger than an entire Mudlark USV! Hopefully, future technological advances will eventually allow much smaller fusion drives to be constructed. You can learn more about ongoing antimatter and fusion propulsion research at Reaching for the Stars.

The following tabletop gaming model is intended to represent a fusion torch USV. Note that the drive is mounted at the end of a boom away from the propellant tanks to protect the vessel from the enormous heat generated by the fusion reactor. The design was inspired by some of the conceptual spacecraft drawings featured on the Transhuman Space “Concept Art” page and Win Barker’s site. Win did the wonderful profile view of a hypothetical fusion torch USV at the top of this page.

Small USV