Re: [Spaceships] Can't find the right propulsion system
 

I would honestly go with a higher delta-v system. A nuclear thermal rocket provides 0.5g and 0.45 mps per fuel tanks at TL9+. It could even be used for shuttle taxis from the surface to orbit and back.

Re: [Spaceships] Can't find the right propulsion system
 

In general the more delta-V per tank, the more destructive the exhaust. Depending on the details of how it's to be used, it might be better to not use a reaction drive at all (use something like tethers, or something that interacts with EM fields created by a larger vehicle).

Re: [Spaceships] Can't find the right propulsion system
 

Well, destructive potential is a related to thrust and delta-v. Doubling thrust usually means doubling mass flow or doubling exhaust velocity. Increasing mass flow will decrease delta-v proportionally to the increase in thrust while increasing exhaust velocity will increase delta-v proportionally to the increase in thrust. Energy is proportional to the square of exhaust increase.

For example, compare the TL9 HEDM rocket (2g/0.5 mps) to the TL9 fission thermal rocket (0.5g/0.45 mps). The former possesses ~2x the exhaust velocity, burns twice as much reaction mass per second, so it is putting out ~8x the energy of latter. While a TL9+ HEDM rocket has exhaust with a temperature of over 26,000 K, the fission rocket is only running at around 6,500 K. While dangerous to unprotected systems, a TL9+ fission thermal rocket is much safer than the TL9 HEDM rocket, dealing ~1/3 as much damage to anything caught in its exhaust flow.

Re: [Spaceships] Can't find the right propulsion system
 

No it doesn't. The TL9 HEDM rocket has 11% higher exhaust velocity and 4x greater thrust, and thus is putting out 4.44x as much energy, but since you only have to burn it for 1/4 as long the net hazard is 11% higher. It's also running at about a 23% higher temperature (temperature varies with the square of exhaust velocity and not correlated with thrust). In any case, HEDM is also a bad choice, most thrusters intended for purposes like this are things like cold gas thrusters with exhaust velocities up to maybe 1 km/sec and thus delta-V per tank of .03mps or so.

Re: [Spaceships] Can't find the right propulsion system
 

Of the rockets available in Spaceships, the ones that seem to produce decent thrust without too much burning doom or issues with casual anti-matter ownership seem to me to be the basic chemical rocket and a nuclear thermal rocket using water as reaction mass (or hydrogen if delta-vee is more important than thrust). One means having highly volatile fuel and oxidant sitting round, the other having fissile materials readily available to all and sundry.

Re: [Spaceships] Can't find the right propulsion system
 

Might want to just tune down your concept of decent thrust. For comparison, a NASA MMU has a total acceleration of about 0.009G with a total burn duration of 450s for a total delta-V of about 40 meters/sec. You might want a tad more performance, but reaching a safe walking speed of 1 yard per second takes 0.09s at 1G, so 0.05G is probably plenty.

Re: [Spaceships] Can't find the right propulsion system
 

Even 0.05G if you don't want a large fraction of the module's mass to be rocket gives fairly limited choices using Spaceships. Chemical, HEDM, NTR, light-bulb, fusion torch if available. I'm not counting nuclear pulse drives or nuclear salt-water because if anti-matter isn't desirable I very much doubt they would be either.

A smaller-system (1/3 size) NTR with a single 1/3rd size fuel tank would give 0.167G and 0.15 mps DV using hydrogen or 0.5G and 0.05 mps DV with water. I think you could probably make a pretty simple, reliable, and failsafe NTR unit at TL10, especially if getting optimal thrust/weight and specific impulse out of it wasn't the priority.

Re: [Spaceships] Can't find the right propulsion system
 

The basic power output of a rocket is 0.5 * thrust * exhaust velocity; for a 1 ton ship managing 0.167G, the thrust is 1480N, at 0.45mps/tank exhaust velocity is 14,400m/s, and thus your 'small' system is still belching out more than ten megawatts.

If you want something that isn't ridiculously dangerous, accept low performance; something like 0.05g at 0.09mps/tank is within the reach of storable liquid rockets.

Re: [Spaceships] Can't find the right propulsion system
 

Hmm... suggestion: Spaceships... 9?: Work Pods and Smallcraft?

Re: [Spaceships] Can't find the right propulsion system
 

Hm... Low thrust rockets:

Remote Heated Hydrogen: Hydrogen heated by laser/solar power to 5800 K. 0.3 mps per tank/0.01g
Microwave Water Rocket: Water heated using microwaves to 3100 K. High Power System. 0.3 mps per tank/0.06g