How NASA's Astronauts will Survive Earth Re-Entry from Deep Space

Overview

The Orion spacecraft will extend NASA's human presence in space beyond low Earth orbit for the first time since the Apollo era (1961-1972). Currently in design, the capsule will be launched atop the new Space Launch System (SLS), which will be the most powerful rocket ever built-capable of 9.2 million pounds of thrust at liftoff. Orion will carry the crew for deep space missions, provide emergency abort capability, and safely return the astronaut crew to Earth.

Project Details

Orion's thermal protection system (TPS) protects the vehicle and crew from the extreme heating environment experienced during re-entry. The TPS consists of both a heat shield on the forebody similar to that used in the Apollo missions, and tiles on the afterbody similar to those used on the space shuttle. The TPS is being designed largely through computational analysis, including an aerothermal database—composed of 1,200 computational fluid dynamics (CFD) solutions—that was used to define the convective and radiative heating environments. The CFD solutions were computed using freestream conditions (velocity, altitude, and angle of attack) that span the possible flight space of re-entry trajectories. Together with ground test data and flight data from previous missions, the database is being used to select the TPS materials and their varying thicknesses over different parts of the vehicle.

CFD was also used to simulate ground tests of complex flow phenomena such as protruding radiometers, firing reaction control system (RCS) plumes, and cavities caused by micrometeroid and orbital debris (MMOD).

Results and Impact

The aerothermal database was used to design the TPS for the Exploration Flight Test-1 (EFT-1) mission, which flew December 5, 2014. During the successful flight, the TPS performed perfectly. Post-test comparisons of predicted and measured temperatures showed good agreement. The results have been used to update the database, which is now being used to design the TPS for the uncrewed Exploration Mission-1 (EM-1), which will return to Earth after orbiting the moon.

Comparisons of the ground test simulations and the measured data validated the accuracy of the computational tools, providing confidence that the simulations of the flight vehicle were also accurate. The ground test simulations also provided quantities that were difficult to measure, such as boundary layer thickness and surface shear. These quantities were used to correlate the measured heating values and develop heating augmentation models that were applied to the aerothermal database.

Why HPC Matters

The 1,200 CFD solutions comprising the aerothermal database, along with the ground test CFD simulations, were run on the Pleiades supercomputer at the NASA Advanced Supercomputing (NAS) facility. The database solutions were computed on grids with 16.4 millions points, and each solution required 48-plus hours of wall time using 300 processors. Large datasets were transferred among various NASA centers throughout the country using high-speed networks, and the solutions are archived in the NAS facility's mass storage system.

What's Next

After the completion of EM-1, the aerothermal database will be updated again to verify the TPS design of EM-2-the first SLS/Orion flight that will carry a crew.