Auburn rocket plume research to aid future spacecraft landings
Published: Jan 15, 2025 2:30 PM
By Mike Jernigan
Landing a space vehicle on an interplanetary body has always been a tremendous challenge. In most cases, powerful retrorockets must fire at just the right moment — with just the right amount of thrust — to slow the vehicle sufficiently to prevent damage and successfully deliver the payload to the target’s surface. That’s why touchdown is always a hold-your-breath moment for the scientists and engineers involved.
Even so, landing successfully is only one part of the battle. The other part is ensuring the dust and debris kicked up by the retrorocket’s thrusters do not damage the vehicle itself or any other important hardware nearby. But a team of Auburn researchers are working to reduce some of the stress during landings by studying these thruster-induced plume-surface interactions (PSI) to better predict their outcomes.
David Scarborough, an associate professor in the Department of Aerospace Engineering at Auburn University, is the principal investigator for two NASA grants — one for $538,789 and a second for $650,000 — to study PSI, along with a team that also includes co-investigators and fellow faculty, associate professor Vrishank Raghav, assistant professor Nek Sharan and the W. Allen and Martha Reed Professor and department chair Brian Thurow. In addition, the research team also includes postdoctoral fellow Vikas Bhargav and graduate students, Murphy Mitchell, Srijan Satyal and Brandon Fulone. In the past, graduate students, Trevor Crane, Daniel Stubbs and Lokesh Silwal were also actively involved in the experimentation work.
NASA’s interest in PSI dates back as far as the lunar missions of the Apollo Program in the 1960s. Research into the issue gained urgency after the Apollo 12 mission in November 1969. On that mission, the lunar module set down adjacent to the lander from a previous 1967 unmanned mission called Lunar Surveyor Three, which had sent back data critical to planning the Apollo landings. The Apollo 12 astronauts brought back pieces of the Surveyor craft, which showed pitting and scorch marks caused by the retrorockets fired during the lunar module’s descent.
With NASA now planning a return of manned missions to the moon in the near future, better understanding plume-surface interactions will be critical to ensuring such damage can be predicted and perhaps mitigated.
“In the next decade,” Scarborough said, “NASA is prioritizing returning humans safely to the moon, deploying scientific instruments on a variety of extraterrestrial bodies and ultimately enabling human exploration of Mars. One of the most significant obstacles to achieving these objectives is our limited understanding of plume-surface interactions leading to crater evolution and dust formation during descent and touchdown.”
In order to improve our understanding of PSI, experimental facilitates have been constructed in the Auburn University Combustion Physics Laboratory (AUCPL) to emulate conditions of extraterrestrial environments that future landers might encounter.
For instance, the vacuum-chamber experimental facility is used to simulate lunar atmospheric conditions, while the drop-tower facility can generate reduced gravity conditions. These facilities were used to record the crater evolution and track ejecta particles using high-speed cameras, to investigate the effects of the thruster operating conditions and the ambient environment.
In spring 2024, Crane and Stubbs took the research even further, designing and conducting experiments on board NASA’s modified Boeing 727 aircraft — nicknamed “the Vomit Comet” — that flies parabola patterns designed to briefly produce lunar, Martian and zero-gravity conditions.
“Depending on the angle at which the plane falls, different gravity levels are simulated inside the cabin,” Crane explained, noting that the aircraft really lives up to its nickname. “In the airplane, we are able to run our PSI experiments in simulated Martian, lunar and micro-gravity conditions. Research using the parabolic flights is ongoing, with future flights planned to gather more data.”
In the recent past, NASA also conducted an experimental campaign called physics-focused ground tests to fundamentally characterize plume-surface interactions. These tests generated substantial datasets, which require a long-term, dedicated effort to deduce important physics involved in the interactions. The team at Auburn also aims to leverage the experimental and numerical capabilities in-house to facilitate the development and validation of predictive tools using the datasets generated by NASA.
Eventually, the team hopes to provide NASA with data that will allow the space agency to confidently predict and make allowances for plume-surface interactions on the moon, Mars and beyond.
“The overall goal of our PSI research is to be able to develop physics-based models for rocket landers that can be used for future missions,” Scarborough said. “These models will be able to relate to parameters like rocket size, engine thrust and dust or particle size of the planetary surface to predict the cratering and debris effects caused by a lander. Future simulations will be able to use these models to better inform lunar and Martian missions and reduce the risks associated with their landing vehicles.”
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David Scarborough, an associate professor in the Department of Aerospace Engineering at Auburn University (middle) stands with graduate students Daniel Stubbs (left) and Trevor Crane (right).
