A sweeping and grinding combined hybrid sampler for asteroid sample return mission

Abstract

Successful sampling on asteroids is challenging due to their weightless environment and unknown material mechanical properties. This work presents a sweeping and grinding combined hybrid sampler (SGHS) to improve the sampling success rate. The SGHS has two working modes, i.e., using two brush wheels to collect regolith and rock pieces and employing a drill bit to grind rocky surfaces into particles suitable for sweeping. We investigated the sampler-regolith interaction and sample particles contact model and designed the adaptive sampling control method. Numerical simulation and prototypical experiments at different structural parameters and speeds of the brush wheels, mechanical properties of the sample, and asteroid surface gravities, were conducted to validate the proposed methods and estimate the amount and speed of sample collection. The 280 g sampler can acquire 24.12 g regolith simulant in 8 s with the “weight on bit” (WOB) of 0.2 N. The drill bit can enhance the sampling efficiency by 151% in rocky sample simulant acquiring. The results also indicate that sample collection on asteroids is more challenging than sampling on Earth. Moreover, the rotational speed of the SGHS should be carefully controlled to avoid sample particles with too high a speed spilling out of the sampling site. The sampler has the advantages of small size, light weight, low WOB, and high adaptability and can be used for future asteroid sample return missions.