Side boosters like SpaceX dragon capsule. It can be helpful for landing on Mars or moons. And it should have powers like Real life, these engines should be able to be attached in side of command pods. or capsule. Example: when you land on Mars, it has thin atmosphere, so landing on it, it would be impossible with small engine with weaker thrust. So We need those engines. Small and strong. And I need it because of landing a rover. Like Curiosity landing.