A new means of space propulsion... closed loop pulse propulsion... here's the idea

[Bernardo de La Paz]

64. Wrong perspective. To inject angular momentum into bullet, it sucks linear momentum

Angular momentum does not come for free.

Use vector analysis. Ideally (idealized analytical cases) the force curving the path of the bullet is at 90 degrees to the line of motion. Friction and such makes it less than ideal.

When the bullet leaves the chamber and enters the curved barrel, the force vector causing it to curve is at 90 degrees to the line of motion.

When the bullet is a quarter circle along the curve, it has to continue to be operated on by a force to keep it curving, but at that point the force is 180 degrees opposed to the original line of motion because the force vector has rotated along with rotating path. It is still 90 degrees to instantaneous velocity vector, but since at the quarter circle the instantaneous velocity vector is 90 degrees, the curving force is 90 deg plus 90 deg = 180 degrees opposed.

That retards the propulsion.

You aren't building an energy capture system. You are building a more complex system which introduces more opportunity for friction and energy loss. Your system would thus be slower than a straight up bullet rocket.

Another problem is that at the half circle, when the bullet is getting ready to escape the barrel, the force vector is now 270 deg from the original line of motion and 180 degrees from the first instance of the force vector as the bullet is leaving the chamber. Ideally this is good because the two would cancel out. But the real world is not ideal. The bullet leaving the barrel (at 180 deg from original velocity) would be travelling more slowly. So the two would not cancel out and you would have a spinning spacecraft. You would have to expend yet more energy to counteract the spin.

You could make a double barrelled gun with the two barrel curving away from you to counteract the spin, but now you have doubled your inefficiencies.

A railgun would not negate the vector analysis. Instead of friction and barrel strength, energy is used to bend the path even if the energy is imparted and transferred in different ways. Railgun or rifle, same failure.