Detumbling is a crucial first step for on-orbit service and space debris removal. Recently, plume has become an efficient medium for detumbling failed spacecraft, which can avoid direct contact to improve operation safety. However, the traditional molecular plume may lead to an unaffordable fuel consumption, so it is necessary to propose a novel strategy to solve this problem. The Hall effect thruster is a common high specific impulse engine, which can generate high-speed plasma plume for contactless detumbling. The traditional plume models present difficulties for practical implementation due to the contradiction between the requirement of real-time computation and the limited computing capability of the spaceborne computer. To address the challenge of calculating the impact force, a fully analytical plasma plume model is proposed to substantially enhance the computing efficiency without loss of accuracy. A guidance law for optimal detumbling is proposed to mitigate the spin angular velocity while stabilizing nutation under multiple complex constraints. To facilitate the development of the detumbling control, a terminal non-singular sliding mode controller based on the saturation function (TSM-sat) is proposed, which can converge in finite time and avoid the chattering phenomenon. The Numerical results indicate that the proposed plasma plume model can significantly improve the computing efficiency and the optimal guidance law can stabilize the target within a reasonable time.