Pondering Marshall Eubanks’s concept of quark nuggets for making antimatter and hunting for such inside NEOs and comets, I thought of what an antimatter starship would require. The difficulty of storing anti-hydrogen led to me reason that carrying an antimatter source, like a quark nugget, made more sense than refining the stuff, then trying to store it safely. Make it as you use it seems the best approach.
That does imply that starships will mass millions of tons, to match the quark nugget. Depending on how the antimatter is mixed into the propellant stream, I suspect an antimatter rocket will be a comet adapted to the purpose, blasting out a jet of energised water as the main reaction drive. I’d hazard to guess the efficiency of such a rocket, since mixing annihilation energy into a reaction stream is incredibly difficult. However an exhaust velocity of 0.1 to 0.2 c seems reasonable.
When drives are power limited, based on the endurance of the engine rather than the energy of the fuel, there’s a simple relationship between the mission velocity, exhaust velocity and cruise velocity, with an overall mass ratio of ~4.42. The cruise velocity – the speed at which the vehicle coasts – would be somewhere between 0.075 c to 0.15 c, while the mission velocity would be 0.05 c – 0.1 c.
In the Oort Cloud there’s about 100 billion comets in far-flung orbits. One for every star in the Galaxy. If each formed around a quark nugget, then that would be 100 billion potential starships. Launching forth to every star in the Milky Way at 0.1 c, they would take ~750,000 years to reach the stars on the opposite side of the Milky Way to us. To reach every Globular Cluster in the Milky Way’s vast halo might take 1.5 – 3 million years.
Not every star has an Oort Cloud, ours being one of the few to keep its Cloud, as passages through Molecular Clouds and tight star clusters can lure the far-flung comets away with their gravity. Yet there are enough Oort Clouds that Others might have done the same before us. If Other Civilizations came to the same conclusion, as my musings above, and launched forth thus-like, what would a Galaxy in the throes of such a “Life Burst” look like from far away? Would we see the unique signs of antimatter annihilation spraying forth from that Galaxy? Could we see it with the right gamma-ray telescopes?