As previously described: if you can get within ten to hundred times the cost of regular power, you would still have huge uses for nuclear fusion. You could revolutionize space travel even if it costs more for nuclear fusion than it does for regular power. You can also combine fusion with fission to make fission clean burning. There are actually several fusion/fission hybrid reactor proposals, but mostly design work.
General Fusion, IEC Bussard Fusion, Tri-alpha energy are all start ups that are shooting for pure fusion that is more economical than current power generation. If they succeed space travel is revolutionized as part of the energy success. If they get close energy would still be revolutionized with fusion/fission, but with redesign to maximize neutrons for the fission blanket.
Popular Science has step by step diagrams of how the sonic waves driven by pistons hitting a metal sphere would drive fusion.
Shockwave already on the way in
As I noted before: M Simon over at IECfusion Tech has come around to thinking it could work, although it will be very tough.
Later version will have 200 big pistons.
General Fusion has $7 million of a $10 million second round raised.
Previous update: General fusion had completed proof of concept experiments and performed full scale computer simulations.
First article by this site on General Fusion's and magnetized target approach