NIAC was one of the projects I worked on in grad school in my Advanced Planetary Sciences class. My proposal was a combination of 3-body gravity assits (i.e. slingshot effects) and solar sails. It got you to the outer solar system in about 3 years and to the ISM in about 15.
This idea though, seems exceedingly clever and takes the solar sail idea up a notch. The basic idea is to build a sail embedded with fissile uranium, build an antimatter source and then throw antiprotons at the sail to cause the uranium to undergo fission. Total amount of antimatter needed to reach the ISM? 30 milligrams. (that seems small, but truthfully it's an enormous amount. 30 milligrams is ~ 2x10^21 antiprotons, and a typical accelerator will produce 10^5 or so per reaction).
The primary question relative to the performance of this concept is the momentum delivered to the sail by the fission of the uranium. If just the two fission products are released then the momentum is determined by the velocity and mass of one of the products. The antimatter induced fission of uranium produces a spectrum of masses. The width of this distribution, however, is relatively narrow and can be approximated by using palladium-111 as the average fission product. The energy released in the fission is taken to be 190 MeV. Thus, the velocity of the fission product is 1.39x10^7 m/s and the mass is 1.85x10^-25 kg/atom. The velocity would equate to a specific impulse of 1.4 million seconds.
It's actually more complicated than that, and the proposal goes into much more detail. I have some questions though about the secondary particle decay chains.
It's an interesting concept.
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