The-thing-next-door wrote:GarryB wrote:
Other ideas could revolve around gravity... is it a field or is it a wave, or something else. If you could find a way of making the mass of a space ship effectively almost zero, then using the same technology to make a grain of sand enormously massive and ejecting it out the back of the ship at reasonable speed should propel that ship forward very efficiently... or a gravity beam could be directed and the planet you launch from to push you into space and towards your destination and attractor gravity beams pull yourself forward like Spiderman uses his webs to "Fly" through a city of tall buildings...
Well if any nation can get create gravity generators it is Russia, but I doubt they will do it within the next 100 years.
A more "reasonable" approach would be to convert energy to matter (theoretically this is possible) and then accelerate that matter out the back of the craft.
Bussar ramjet fusionate the interstellar protons, and getting energy from them, it doesn't need propelant.