The SHERPA system provides the capability for delivering payloads to within the proximity (~5 km) of a location above a mission target over a range of high altitudes (up to 2.5 km above the reference geoid). The performance provided by SHERPA would open up thousands of landing sites for targeted science investigation over a whole range of latitudes and seasons, providing a major improvement over conventional ballistic unguided Mars entry vehicles.

The main innovation in SHERPA lies in tailoring the system elements to the unique attributes of Mars EDL. We exploit the phasing and intervals within the short duration of the EDL timeline to develop a sensing strategy that overcomes errors in delivery and knowledge of the vehicle, and minimizes system cost. An innovative moving-mass configuration allows for generation of aerodynamic lift (through variation of the vehicle trim angle-of-attack) and results in a non-propulsive, high-control authority, responsive, aero-lifting method of vehicle control with fail-safe features.

SHERPA can be mounted within the traditional blunt-body-aeroshell entry-vehicle configurations, leading to a low-cost, low-risk approach that could be used on a variety of Scout missions. The guidance and control approach takes into account the landing ellipse geometry, and exploits the cumulative effect of integrating over a series of control actions to minimize the final terminal error from the target. The SHERPA electro-mechanical elements are tailored for one-time sensing and actuation, and take advantage of opportunities provided by scaling laws as applied to the Scout vehicle size regime.

We are developing the system concept, designing the strap-on sensor and moving-mass actuators, and developing the proof-of-concept algorithms for guidance and control of the system. We are validating the feasibility of our approach through a combination of simulation and prototyping of key mechanical elements.