Watching Out for Flying Debris
Everyone knows that Space Shuttle safety is a top priority at NASA, but few people know that one of the world's fast supercomputers plays an important role in mission safety. Behind the scenes at every shuttle launch over the past seven years, a team of NASA scientists and engineers monitor flying debris that could jeopardize the safety of the launch vehicle and crew.
Using the combined power of modeling and simulation tools and supercomputers, this team has supported the Space Shuttle Program through a series of prelaunch, inflight, and post-flight debris risk assessments that have helped ensure successful shuttle missions.
Before each launch, the team employs their custom numerical simulation tools to determine whether unusual ice formations and insulating foam defects pose a threat to the vehicle. During the prelaunch countdown, they perform on-the-spot simulations to ensure ice accumulation on the shuttle's external tank does not reach potentially dangerous levels.
Simulation of the impact conditions of a thermal protection tile plug during reentry. (Reynaldo Gomez, NASA /Johnson)
"Identifying and predicting the wide range of possible debris sources and damage that could impact the shuttle and astronauts is a huge responsibility and challenge," said Reynaldo Gomez, a senior aerospace engineer who leads the debris trajectory assessment effort at Johnson Space Center in Houston.
Gomez, working with a team of computational fluid dynamics (CFD) experts at the NASA Advanced Supercomputing (NAS) Division of NASA Ames Research Center, uses solutions from the OVERFLOW CFD code, along with a NASA developed debris trajectory simulation code, to predict debris paths and damage. Modeling the many possible debris trajectories, and comparing mock conditions to the shuttle thermal protection system's real-world ability to withstand impact, requires hundreds of high-fidelity simulations that must be run in a short time. This is where NASA's powerful high-end computers come in.
Running on the NAS facility's reliable production supercomputers, Pleiades and Columbia, high-fidelity CFD simulations of the complex flowfield around the launch vehicle consume 600,000 processor-hours and churn out hundreds of gigabytes of data to simulate a typical Shuttle ascent trajectory.
In addition, team members must also evaluate damage or protruding pieces of insulation detected on the vehicle to determine whether astronauts and robotic assistants need to complete on-orbit repairs. To make time-critical decisions about possible fixes, simulations are postprocessed through a set of automated tools running on the supercomputers so that debris experts can view results in near real time.
With the countdown to NASA's final two Space Shuttle launches rapidly approaching - Discovery is currently set to launch November 30, 2010 and Endeavor in February 2011-Gomez and partners at NASA Johnson and Ames are gearing up for their next set of mission challenges. The team is already applying their shuttle debris experience and sophisticated CFD tools to assessing design risks for future vehicles that will carry our next generation of explorers into space.
"The real payoff for all of our efforts to understand and reduce the debris risks," said Gomez, "will be seeing the Orbiter safely land after the final mission."
More information:
+ Space Shuttle Debris Transport Assessments (PDF 135 KB)+ The Impact of High-End Computing on the Space Shuttle Program (PDF 1.9 MB)
Contact information:
Reynaldo J. Gomez
Aerospace Engineer
Aerosciences and Flight Mechanics Division, NASA Johnson Space Center
reynaldo.j.gomez@nasa.gov
(216) 433-5586
