So their task now was to stabilize Ymir ’s attitude by using her thrusters to push back against the unwanted rotation. And, as they had discovered the first time they’d tried it, her thrusters were small and weak compared to the momentum of the big ice shard. In aerospace lingo, they lacked control authority. Ymir was like a truck skidding on a patch of oil, responding only faintly to the steering wheel. That problem had been alleviated somewhat by the large expenditure of mass during the burn. Many tons of ice had been hurled out the nozzle in the form of steam. Ymir was lighter and more wieldy as a result. Calculating exactly how much more wieldy she was, and what it meant for the thrusters’ control authority, was, in itself, a significant task that consumed another half an hour just for a rough estimate.