YMMV? What does that mean?
Water has a mass per molecule of 18, Sodium has a mass per atom of 23. The lighter the molecule or atom of reaction mass, the higher the specific impulse, and hence final velocity for equal mass-ratios. The optimum reaction mass is Liquid Hydrogen, which was proposed for use in nuclear-powered space ships in the 1960's, where it was used both as reactor coolant and reaction mass. One reason the Shuttle was burning excess hydrogen in its engines was to reduce the average molecular weight of reaction mass to increase specific impulse. The other advantages of water is that it is a liquid at normal temperatures, has the ability to absorb a lot of heat, and can be used to cool the exhaust nozzle of your reaction engine.
That's assuming a pure chemical reaction with some heat for thrust. I read Traveller tech as a little higher order than that; some kind of controlled fusion release process where the nuclei are split, and the resulting energy is focused aft through induction.
Interesting side note; HE
3 rockets were supposed to be the "rockets of the future" with a very promising plasma reaction sustained in a magnetic field. It is a current technology. Regrettably, however, the mass of the magnet required to contain such a reaction makes current use highly impractical, as the magnets would weigh down said rocket too much to be of any use (at least as a measure of lifting against a severe gravity well, say the surface of the Earth). But there was lots of talk some 20 years back about using them for interplanetary exploration and travel, and allegedly, if the magnetic field issue can be solved, then we might have seen HE
3 rockets in our life time. Regrettably, again, I think the world's supply of HE is supposed to run out in the next 20 years (possibly earlier). However, lunar regolith is supposed to have pockets of the stuff frozen underneath the powdery surface.
Getting back to Traveller; the thrust issue, as I see it, and this is just going by what's shown in the drawings, is that thrust plates or "reactionless" drives are BS. You've got to have some kind of substance "to burn" and jet aft to push your craft forward. It seems, to me at least, that there's a turbine kind of mechanism involved. And, again just my personal opinion, the hydrogen nuclei are hypercharged to a plasma state, spun up, and the lateral momentum is directed aft through the nozzles.
Magnitude and containment fall into the handwave arena. But, such technology could be possible for one man to handle; i.e. maintain and fix without a lot of super tech and support crew to trouble shoot problems. Thereby making life aboard a scout ship that much more feasible.
