Future spacecraft bound for the Moon or beyond will benefit from high-powered computer simulations that model the particulate mayhem set in motion by rocket thruster-powered landings. During descent, exhaust plumes fluidize surface soil and dust, forming craters and buffeting the lander with coarse, abrasive particles. This action presents a host of variables that can jeopardize a landing. A current understanding of those millions of interactions is based on data that is, in some cases, 40 to 50 years old. Much of the available data used in the design stage, including for the Mars 2020 mission, is based on Apollo-era data.
Landing-relevant data is very difficult to generate because such an experiment cannot be run on Earth. Existing mathematical models break down in these more extreme conditions when particles approach supersonic speeds. The new numerical algorithms enable such simulations.
The team is developing physics-based models that can be incorporated into codes used by NASA to help predict what will happen when a spacecraft attempts to land millions of miles from home. These include “messy turbulent flows” and simulating the behavior of fluids made of two phases of matter — in this case, solid particles suspended in a gas.
Apollo-era landings showed that disturbed surface material can spread up to half a mile, posing hazards not only to the lander itself, but also for neighboring vehicles or landing sites. Despite advances made in the years since, landings remain fraught with potential hazards. Eight years ago, a wind sensor on the Curiosity rover was damaged during its Mars landing. As NASA moves toward new crewed missions under the Artemis Program, this work becomes more vital. Not only do humans onboard raise the stakes, they mean larger payloads and subsequently, stronger exhaust plumes interacting with the planet’s surface.
The team uses models — best guesses based on all available data — to provide a framework NASA can use to better predict how different designs will impact the ground and the landing and adjust.