NASA Uses ORNL Supercomputers to Plan Smooth Landing on Mars

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A U.S. mission to land astronauts on the surface of Mars will be unlike any other extraterrestrial landing ever undertaken by NASA. 

Although the space agency has successfully landed nine robotic missions on Mars since its first surface missions in 1976 with the Viking Project, safely bringing humans to Mars will require new technologies for flight through the Martian atmosphere. But these technologies and systems can’t be comprehensively tested on Earth beforehand. 

Since 2019, a team of NASA scientists and their partners have been using NASA’s FUN3D software on supercomputers located at the Department of Energy’s Oak Ridge Leadership Computing Facility, or OLCF, to conduct computational fluid dynamics, or CFD, simulations of a human-scale Mars lander. The OLCF is a DOE Office of Science user facility located at DOE’s Oak Ridge National Laboratory.

The team’s ongoing research project is a first step in determining how to safely land a vehicle with humans onboard onto the surface of

Composite animation showing autonomous flight trajectory using closed-loop flight control computed on Frontier. The vehicle descends from approximately seven kilometers altitude to one kilometer and decelerates from Mach 2.4 to approximately Mach 0.8 during this 35-second period. The top inset shows the RCS firing sequence and associated roll angle, which can also be observed as a subtle +-1-degree vehicle rotation in the main image. The top-right inset shows a farfield view of the trajectory, where the Martian surface is indicated by a Cartesian grid with a 1-kilometer spacing. The middle-right inset shows the throttle settings for each of the eight main engines, which decelerate the vehicle and also control pitch and yaw. The bottom-right image shows the vehicle pitch angle, which can also be observed in the main image. The main engine plumes are visualized using density weighted by the H₂O mass fraction, while the RCS jets are shown using density weighted by the N2 mass fraction with separate red/green colormaps depending on thrust orientation. Credit: Patrick Moran/NASA

“By its very nature, we don’t have validation data for this. We can do valuable but limited tests in ground facilities like a wind tunnel or on a ballistic range, but such approaches cannot fully capture the physics that will be encountered on Mars. We can’t flight-test in the actual Martian environment — it’s all or nothing when we get there. That’s why supercomputing is so critically important,” said Eric Nielsen, a senior research scientist at NASA’s Langley Research Center and principal investigator for the 5-year effort at the OLCF. 

Unlike in recent Mars missions, parachutes are not part of the operation. Instead, the leading candidate for landing humans on Mars is retropropulsion — firing forward-facing rockets built into the craft’s heat shield to decelerate. 

“We’ve never flown anything like this before. The fundamental question from the outset was, ‘Are we going to be able to safely control this vehicle?’” Nielsen said. 

The reason that NASA is investigating retropropulsion rather than conventional parachutes is a matter of physics. Previous Mars landers have weighed about 1 ton; a vehicle carrying astronauts and all their life-support systems will weigh 20 to 50 times more, or about the size of a two-story house. Mars’ thin atmosphere — about 100 times less dense than Earth’s — won’t support a parachute landing for such a large craft. 

“With a conventional vehicle, we fly through a very clean, predictable environment. All of that goes out the window with this concept, where we will be traveling through an extremely dynamic environment consisting of high-energy rocket exhaust,” said NASA team member and CFD expert Gabriel Nastac.

With guidance from NASA mission planners, the team formulated a multiyear plan consisting of increasingly sophisticated simulations aimed at the key question of controllability.

In 2019, the team conducted CFD simulations on the Summit supercomputer at resolutions up to 10 billion elements to characterize static vehicle aerodynamics at anticipated throttle settings and flight speeds ranging from Mach 2.5 down to Mach 0.8, conditions in which the vehicle’s rocket engines will be required for initial deceleration.