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Full Version: Bussard Pulse Jet?
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I was thinking the other day, and an idea wandered through my mind for possibly overcoming some of the deficiencies of the Bussard Ram Jet. 

The main issue with the Ramjet, as I understand it, is that all that hydrogen that gets scooped up has significant inertia which gets transferred to the ship, counteracting the thrust.

My idea was, is it possible to selectively capture the hydrogen that has low velocity relative to the ship?

The Bussard Ram Jet scans ahead with a laser to ionize the hydrogen, then scoops up the hydrogen with its magnetic scoop.

My Pulse Jet idea would be to de-energize the magnetic scoop while energizing the laser, wait a few milliseconds for the hydrogen ions at high velocity relative to the ship to get the hell out of the way, then energize the magnetic scoop.  You suck up the hydrogen ions that you can have for a discount price in inertia, letting the rest go, and then fire up the laser again, repeating the cycle.

Can the scoop be switched off and on fast enough (and cheaply enough in energy) for this to be viable?  And would it help? Reducing the relative velocity of hydrogen ions captured by half should reduce the energy penalty by a factor of four.  Is this a thing that we can do?

And about halfway between relevant and non-sequitur, an observation:  The ideal environment for any Bussard Ramjet to operate at an energy profit is in the exhaust stream of another Bussard Ramjet going the opposite direction.
I'm not entirely sure I'm understanding this correctly, so I could be off base here but...

Given that a ramjet is intended to pretty quickly start moving at a significant fraction of the speed of light, isn't it going to rapidly reach a point where no interstellar H2 is moving with low velocity relative to the ship since the ship is moving at a much higher velocity than any drifting interstellar H2 is going to be able to manage?

On a different note - Your final observation comes close to the principle beyond beamed matter propulsion systems, I think.

My initial 2c worth,