Inter-satellite links (ISL) have great potential in orbital edge computing (OEC). We propose to use inter-satellite links for on-board intelligent task collaboration to cope with the new requirements. We model interplanetary networks and tasks and consider the energy consumption and latency parameters during task execution. The Lyapunov method is innovatively introduced in the Greedy method to realize the online unloading decision of the task. There is a trade-off between energy consumption and task latency. Compared with some traditional methods, the proposed strategy has outstanding performance in the overall task delay and energy saving.