Project Longshot

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Project Longshot is a design for an interstellar spacecraft, an unmanned probe intended to fly to Alpha Centauri powered by nuclear pulse propulsion. Developed by the US Naval Academy and NASA, Longshot was designed to be built at the Space Station Alpha, the much larger precursor to the existing International Space Station. Unlike the somewhat similar Project Daedalus, Longshot was designed solely using existing technology, although some development would be required.

Unlike Daedalus' closed-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 would rely on the fusion reaction being able to power the ship as well, whereas in Longshot the external 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 kilowatts. 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 dedicated to communications at about 1 kilobit per second.

Longshot would mass 396 Metric tonnes 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 mass around 30 tons.

A notable difference in the mission architecture between Longshot and the Daedalus study is that Longshot would go into orbit about the target star while Daedalus would do a one shot fly-by lasting a comparatively short time.

The journey to Alpha Centauri B orbit would take about 100 years and another 4.39 years would be necessary for the data to reach Earth.

[edit] Reference

Beals, K. A., M. Beaulieu, F. J. Dembia, J. Kerstiens, D. L. Kramer, J. R. West and J. A. Zito. Project Longshot: An Unmanned Probe To Alpha Centauri. U S Naval Academy. NASA-CR-184718. 1988.