Try this primitive balloon model attached. Well, it is an early form of flight 😛
The next step is to add more thrusters for sideways motion and ruby controllers to adjust the thrust in flight, but the balloon model floats around quite nicely with a nudge. Select the balloon and open the UI to see the thruster parameter. One limitation is that the thruster will not work if the thrust object is grouped with anything else so that is why I have connected the "basket" with a joint and a gyro was added for stability. The altitude can be changed while the simulation is running by holding shift and giving it a nudge up or down, or by slightly adjusting the thrust parameter in the UI and putting the cursor back over the simulation window again.
