Chakat Firepaw

Fission-Fragment uses plutonium as both fuel and propellant. The whole idea is to fire the fission products right out the back. Using it to heat hydrogen would be an NTR-Plasma or NTR-Gas and be pretty much useless in a Bussard Ramjet. Then you are right back to the problem of every drive we know is physically possible to build being at best borderline for use in a Bussard Ramjet. Some types of Fission-Fragment rocket could actually get the ship going _faster_ than a Bussard Ramjet.

Even as is it would still be better than what you have, plus you could mount a nose cone to improve the aerodynamics further. As for turning it around: Perhaps a set of thrusters on each end which are solely there to do the flip and that you can ditch as soon as you are around.

They have the specific impulse, (some proposed designs hit 1.5Ms), but use the wrong fuel and propellant. Remember that a Bussard Ramjet has to use protium with small amounts of deturium and helium because that's what it's going to be scooping up. Fission-Fragment designs all use high-mass elements, (e.g. plutonium), as both fuel and propellant.

Only if one of the following conditions are true: The minimum velocity is near the lower end of the range, (it runs from 0.01-0.06c depending on scoop geometry and the density of the interstellar medium), and we can build a Fusion or AM-Thermal rocket near the top end of their possible performance, (they cap out in the 0.02-0.03c range). AM-Beam Core rockets actually work and we can build one. Put simply, any drive which we know to be physically possible and that can use a Bussard ram scoop is at best marginal for use in a Bussard Ramjet.

There are some things that would be hypergolic monopropellants, (e.g. monoatomic hydrogen), they have this tendency to confuse "storage tank" for "bomb casing".

Yes, it's the exhaust velocity of the drive. Once you combine it with the minimum velocity, you kind of have to toss it out as being that useful. The low end of the minimum velocity range is ~0.01c, which is already putting you near the top end of Fusion and Antimatter-Thermal drives. For a drive that would actually be useful to combine with a Bussard ramscoop you need to use something like a Antimatter Beam Core.

Because you don't want to overshoot your intended orbit?