Venus Analog Testbed for Rasp and Sample Acquisition Testing

Introduction: Similar in size Venus has been called Earth’s sister planet. However with an atmospheric pressure of 90bar and surface temperatures exceeding 460oC, the conditions on the surface of Venus are some of the most extreme in the solar system. Our desire to go to learn more about our neighboring planet is pushing the envelope for sample handling technologies. The Venusian environment is extremely hazardous to hardware. For in situ missions to Venus one of the main challenges will be acquiring samples, delivering and analyzing them before the spacecraft succumbs to the environment. During a RASP interaction with a solid sample, the high speed (1000+ rpm) RASP cutting bit imparts a large velocity component to RASPed particles that is approximately the tangential tool velocity at the RASP cutting interface. While RASPing in a vacuum or low pressure gas (i.e. Mars Phoenix ISAD RASP as shown in Fig. 1), the resultant cutting particle trajectories are very close to ballistic. In denser atmospheres, the atmospheric fluid can significantly alter particle flow characteristics. In fact, in preliminary RASP tests in water, the viscous fluid interactions with the RASP bit generated very strong fluid vortices in the vicinity of the RASP bit that dominated the transport of RASPed particles. Based on these preliminary results, we anticipate that in the viscous (high temperature CO2 near critical point) dense Venus atmosphere, the fluid interactions with the RASP bit will play a significant role in the collection and delivery of RASPed cuttings. In fact, RASP bit and sample collection housing designs that incorporate Venus atmospheric fluid dynamics considerations may likely augment the ability to collect sample including unconsolidated soils where the RASP is not actually performing significant cutting. In the absence of these considerations, there is a strong possibility that residual vorticity in the Venus atmosphere local to the RASP bit will complicate particle settling and collection in a desired collection region. Based on these observations, we are in the process of assembling a test facility for aiding in the design and testing of a RASP system under simulated Venus conditions. To support RASP sample handling testing in parallel with high temperature actuator development, we have identified a lower temperature fluid analog solution for simulating the RASP cutting particle trajectories and behavior in the Venusian environment. Figure 1 – RASP deployed on Mars Phoenix mission (Photo credit of NASA/JPL). Pneumatically actuated prototype RAPS system cutting into Basalt rock under earth atmospheric conditions. Left: Beginning the RASP cut. Right: After ~1 minute the RASP bit has plunged beyond 2cm depth.