Page:Project Longshot - Advanced Design Program Project Report.pdf/36

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The Matter Anti-matter Annihilation could potentially be capable of producing the necessary specific impulse of a million seconds, but it was not considered to be feasible to create a system adequate for storing the anti-matter for 100 years under the limited power constraints of a spacecraft.

The ideal rocket equation was used to determine the potential specific impulse of an extremely high temperature expansion of gas through a nozzle. (See calculations and assumptions in appendix.) Using the critical temperature for sustained Deuterium fusion (3.9E8 degrees Kelvin) a specific impulse of 39000 seconds was calculated (1/300th the specific impulse desired). Since this specific impulse is insufficient for the mission requirements (using an extremely optimistic temperature under ideal conditions), this candidate was dropped.

Advances in technology for an accelerated ion drive (using a magnetic/electric field to fire charged particles out a nozzle) have brought the specific impulse to 3500 seconds. Although this is a current technology that could be implemented now at a relatively low cost, it is felt that the two remaining orders of magnitude will remain out of reach in the near future. Therefore, this candidate was also discarded.

In determining the feasibility of a Laser-pumped Light Sail, another method besides comparing specific impulse becomes necessary, since the drive is external. The single impulse required to reach the designated system in 100 years was determined to be 13,500 km/sec.