He says that his hypothesis is based on Mach's principle that posits inertia, the resistance of mass to acceleration, is a result of the mutual gravitational attraction of all matter in the universe.
If a spacecraft engine could be designed to exploit it then acceleration could be produced without using rocket propellants.
No practical working devices have been publicly demonstrated, and other experiments have failed to corroborate these claims.
[4] He frequently contributes to articles on speculative space travel subjects,[5] especially wormholes.
[6] In 2012, he published a book on the application of the physical effects predicted by his hypothesis to space travel.