Unlike Daedalus, which used an open-cycle
fusion engine, Longshot would use a long-lived
nuclear fission reactor for power. Initially generating 300 kilowatts, the reactor would power a number of
lasers in the engine that would be used to ignite
inertial confinement fusion similar to that in Daedalus. The main design difference is that Daedalus also relied on the
fusion reaction to power the ship, whereas in the Longshot design the internal reactor would provide this power. The reactor would also be used to power a laser for communications back to Earth, with a maximum power of 250 kW. For most of the journey, this would be used at a much lower power for sending data about the
interstellar medium; but during the flyby, the main engine section would be discarded and the entire power capacity dedicated to communications at about 1 kilobit per second. Longshot would have a mass of at the start of the mission including 264 tonnes of
helium-3/
deuterium pellet fuel/propellant. The active mission payload, which includes the
fission reactor but not the discarded main propulsion section, would have a mass of around 30 tonnes. A difference in the mission architecture between Longshot and the Daedalus study is that Longshot would go into orbit about the target star, while the higher-speed Daedalus would do a one shot
fly-by lasting a comparatively short time. A travel to Alpha Centauri with a Longshot spacecraft would take about one century. == See also ==