Abstract DGP2026-58

Introduction

The Hayabusa2 and OSIRIS-REx missions successfully returned material from near-Earth asteroids (NEA) Ryugu and Bennu using Touch-and-Go (TAG) manoeuvres [1,2]. Hayabusa and Hayabusa2 collected material mobilised by the impact of a projectile. OSIRIS-REx released pressurized nitrogen gas to eject surface material into a container. In contrast, other programs (e.g., Chang’e) utilise landers that are equipped with sampling devices like drills or scoops [3]. As part of the MarcoPolo-R mission study [4], a Brush Wheel Sampler (BWS) was considered for TAG sampling of a NEA. The idea was to brush surface material into a canister. The basic principle of a BWS is applicable for both TAG sampling as well as lander-based sampling. This is why, we are adapting this mechanism from previous studies [5–7] and optimise it for sampling a broad range of grain sizes in both lunar and asteroidal environments.

Sampler Design

In collaboration with DLR and MPS Göttingen, a BWS concept was developed as the APOphiS SUrface saMpler (APOSSUM) during two concurrent engineering studies at DLR Bremen in 2024 [8,9]. Based on this design, several iterations of laboratory setups were constructed to test sampling efficiency. The current setup consists of two cylindrical brushes that are 100 mm in length and diameter. Each brush is rotated individually with up to 400 rpm by BLDC motors. Material with grain diameters up to 50 mm is captured and lifted through a tube into a container. Potential jamming is undone by rotating brushes in reverse direction. A linear stage simulates the sampling process during a TAG manoeuvre. Potential flight instruments will incorporate three cameras to overview the brush-surface interaction and sampling process.

First Test Results

The BWS is undergoing extensive vacuum testing to determine the importance of parameters like gravity, brush rotation speed, grain size/shape, bristle hardness, and motor torque for the sampling efficiency. Soil simulants used for testing include lightweight clay aggregates (LECA), Ytong, sand (WF34), and lunar simulant (TUBS-M). Test results indicate an importance of brush rotation speed for sampling efficiency. Faster rotation speeds enhance efficiency, especially for larger grain sizes. Under laboratory conditions, the BWS proved robust under Earth gravity and has shown satisfactory efficiency. In DropTower and GraviTower experiments at the ZARM Bremen, the BWS has shown improved sampling efficiency under reduced gravity and microgravity.

Outlook

The BWS is a payload for the PRIAMOS mission proposal aiming to sample a D-type NEA. Ongoing development focuses on an improved concept to combine brushes with their motors, especially considering redundancy. Also, a shutter mechanism between brushes and sampling tube that traps material is under consideration.

Acknowledgement

This project is supported by DLR with funds provided by the Federal Ministry of Education and Research under grant number 50OO2511.

References

[1] Watanabe S. I., et al. (2017) Space Science Reviews, 208, 3-16.

[2] Lauretta D. S. et al. (2024) Meteorit. Planet. Sci., 59, 2453-2486.

[3] Xiao et al. (2021), Sample return missions, 195-206.

[4] Barucci M. A. et al. (2012) Exp. Astron., 33, 645–684.

[5] Bonitz R. (2012) IEEE Aerospace Conference, Big Sky, MT, USA, pp. 1-6.

[6] Zhang J. et al. (2022) Acta Astronautica, 198, 329-346.

[7] Luo H. et al. (2023) Front. Mech. Eng., 18, 16.

[8] Grundmann J. T. et al. (2025) Apophis T-4 Workshop.

[9] Goldmann M. et al. (2025) Apophis T-4 Workshop.