bussard

This was also the opinion of the late Robert Bussard, inventor of the Bussard ramjet and the polywell fusor.

As such, the theoretical upper-bound speed limit relative to the interstellar medium of a Bussard ramjet is also ~0.12c.

Unfortunately, $10M is 1/20th what Robert Bussard wanted to try and build a break-even demo reactor.

If you crunch the numbers, it turns out the bad news is a Bussard ramjet won't work as an engine.

The classic example of a system which does something like this is the Bussard ramjet.

And Bussard claimed that the polywell skirted around Rider's assumptions, though I don't know the details.

A Bussard ramjet will never work, even assuming we get the scoop part figured out.

Most notional implementations of the Bussard Ramjet depend upon some sort of heretofore undiscovered force field rather than a physical structure to collect hydrogen, because size matters.

Flash crowds, tides around neutron stars, Bussard ramjets, organ transplants gone wild, direct brain stimulation as a drug, ring worlds...

(Besides, it might be possible to launch a running Bussard reactor, jumpstarted on the ground.

Solar sails, bussard ramjets, space elevators.

That is what prompts the imagining of alternate propulsion technologies, such as the Orion nuclear rocket, solar/laser sails, Bussard ramjets, slingshot orbits, and magnetic braking loops.

Starting up a Bussard reaction does require a certain amount of energy, but not to a "requires a fission reactor" extreme.

There was a sci fi book where a ship's Bussard Ramjet got stuck in the "on" position and they kept accelerating until time dilation allowed them to survive a great crunch and another Big Bang.

(Although in practice your maximum speed is largely dictated by "melting the engine is considered shortsighted".) The theoretical upper-bound exhaust velocity of a Bussard ramjet is something like ~0.12c, assuming you start with 4 hydrogen and end with 1 helium.

Most scientists working on imaginary spacecraft projects therefore eschew the Bussard, correctly anticipating the moment when, shortly after the leader gives a speech on the deck of a starship in front of a huge "Hydrogen Accomplished" banner, the price of hydrogen rises to over $5 a gallon and starships are all left to rust in the front yard.

Bussard is by no means a crank, he IS from a different era for sure.

I wonder about a fusion rocket drive, like Larry Niven wrote about (not the Bussard, the reaction drives).

This would seem to be an upper limit for Bussard-type propulsion systems.