Sorry, it doesn't seem to be working. I'm using a simple test vessel with a tank of liquid hydrogen, the engine, some large batteries and a command pod. The engine seems to be working fine then, but whenever I add solar panels to the craft, the problem I described happens. However, I tried another test vessel with a simple nuclear reactor setup for power and the engine actually produced around 0.6kn of thrust which is much more than before but still not viable for missions. To use this engine, do I need to use more advanced nuclear reactors?