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Aaron Morris
Aaron Morris
PhD Candidate, Aerospace Engineering


David Goldstein
David B. Goldstein
Hayden Head Centennial Professor
in Engineering


Philip Varghese
Philip L. Varghese
Stanley P. Finch Centennial Professor
in Engineering







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Preparing for a Return to the Moon

Apollo 11 lunar lander

Above: The Apollo 11 Lunar Module is seen here on the surface of the Moon. Researchers in the ASE/EM Department are working on developing accurate models to solve the problem of rocket plume impingement, a problem that all spacecraft face when landing on the surface of the Moon.
Photo credit: NASA

Aaron Morris, a PhD candidate in the Department of Aerospace Engineering and Engineering Mechanics (ASE/EM) and his faculty advisors, Professors David Goldstein and Philip Varghese, are working on a project that should ensure a much safer landing when astronauts return to the Moon.

The trio has been working with Dr. Laurence Trafton in the Astronomy department on developing accurate models for rocket plume impingement for the last four years. Rocket plume impingement is a problem that all space vehicles face when landing gently on an unimproved planetary surface. When a spacecraft descends over the surface, the plume from the rocket engine erodes the dust from the ground, sending particles flying in a high velocity spray (due to the absence of a lunar atmosphere). This substantially reduces visibility during landing and makes it difficult for astronauts to control the spacecraft. It can also cause problems with false instrument readings, clogging of seals or mechanical joints and abrasion of nearby surfaces.

The dust sprays resulting from rocket plume impingement proved to be a problem during the Apollo missions. As the Apollo 12 Lunar Module descended to the surface of the Moon, the surface was nearly completely obscured by the dust and the astronauts were forced to land blindly, with no way to see whether the landing surface was safe. The risk of landing on a crater rim or large boulder was a major concern because the result could have been catastrophic.

Accurate modeling of this problem could eventually pave the way for NASA’s goal of establishing a permanent structure on the Moon. Scoured dust particles in the spray can travel up to 1,000 m/s, which could cause considerable damage to the surfaces of a nearby lunar outpost – the solar panels, antennae, inflatable domes, etc.

dust modeling

Modeling example of rocket plume impingement: A 1.4m tall berm placed 20m from the lander is used to deflect the dust spray and protect downstream structures. Dust particle streaks, colored by particle speed, are plotted over background grayscale contours of dust number density. The lander is hovering 5m above the surface. Note that many of the particles are deflected upwards as they strike the berm.

Understanding the risks of rocket plume impingement will also help to protect space history – including preservation of the flags and footprints left behind from previous Apollo landing sites.

In fact, several planned missions associated with the Google Lunar X-Prize may land near the old Apollo sites. The competition offers up a total of $30 million in prizes to the first privately funded teams “to safely land a robot on the surface of the Moon, have that robot travel 500 meters over the lunar surface, and send video, images and data back to the Earth.”

Morris came to UT for his graduate studies in 2006 after receiving his undergraduate degree in mechanical engineering from Rensselaer Polytechnic Institute. Once he completed his MS in 2009, Morris began working on his PhD. He decided to pursue his doctoral degree after interning at the NASA Jet Propulsion Laboratory (JPL).

 “Many of the more interesting projects at JPL had teams of engineers and scientists with doctoral degrees,” Morris said. “One of them was launching probes through sheets of ice to explore the subsurface oceans of Europa. I knew I needed a higher degree to work on those kinds of exciting projects.”

Morris attributes his great experience at UT to the dedicated and experienced faculty.

“I couldn’t have asked for better advisors,” Morris said. “Drs. Goldstein and Varghese have held me to a high standard, but they have also given me the freedom to take my research in directions that interest me most. They always look out for their students’ interests and help them reach their highest goals.”

Upon graduation this December, Morris plans to complete a post-doctoral fellowship in the UT ASE/EM Department before entering academia.