Chemical rockets are the simplest, shortest range, but also most reliable and easiest to fabricate of the spaceships.
Chemical rockets combine oxygen and hydrogen, or other substances, to create a flammable mixture that pushes the rocket forward. They have very high thrust (even higher per weight than most torchships apart from Conversion Drive) , but very low isp (fuel economy). They are safe (if regularly well maintained), cheap, low tech (humans have used them since the days of Old Earth), can be safely used near space habitats, and are perfect for small short range craft like shuttles, as well as tugboats, and steering rockets on large ships. Fuel is cheap, they can use the elements of ordinary water. On the down side they are temperamental, all the valves and pumps can be fidgety and wear out after a while, if not regularly maintained they will go wrong at the worst possible time.