Stewart has published more than 100 papers, gained renown in the academic world and helped bring about engineering feats that make space expeditions viable today — but none of that is obvious from talking with him.
Stewart’s wife, Faith, said he would never have agreed to an interview if she hadn’t pushed him into it.
“He’s way too humble for what he’s done in life,” she said. “The mementos or awards that he has that are signed by the head of NASA, or by astronauts and that kind of thing, are really impressive. There’s just a room full of these things.”
Stewart recently added a prestigious achievement to his collection. He and colleague Daniel Leiser won the 2011 NASA Government Invention of the Year prize for a scientific breakthrough that is heating things up — and cooling them back down — in space travel.
High-tech thermal gear
Stewart and Leiser developed a lightweight, two-piece thermal protection system for use on space vehicles as they re-enter Earth’s atmosphere at supersonic speeds.
The invention is called the Toughened Uni-piece Fibrous Reinforced Oxidation-resistant Composite, shortened to TUFROC.
TUFROC tiles are attached to the leading edge of wings to ensure that the wing retains its shape when exposed to the searing temperatures of re-entry into Earth’s atmosphere. The surface of the system heats up and radiates much of the heat back into space, rather than allowing it to harm the spacecraft.
That is important, Stewart explained, because changes to the surface of the wing could mean disaster.
The tiles can also be used on other areas of the vehicle, including the nose, fuselage and other surfaces that are exposed during re-entry.
The invention is a low-cost, flight-proven, reusable thermal protection that can operate at temperatures hotter than 3,000 degrees Fahrenheit, Stewart said. In the past, much more expensive thermal protection systems with built-in cooling devices were the only way to keep wing surfaces stable during re-entry.
The invention was successfully demonstrated on the robotic X-37B Reusable Launch Vehicle, which returned to Earth on June 16 after 15 months in orbit.
Stewart will head to Washington, D.C., in February to formally accept the prestigious award and said he didn’t expect to win, but it was nice to be recognized.
He said the TUFROC wasn’t the type invention one walks into the office one day and thinks up, but the product of more than 30 years of experiments, discussions, trial and error.
Error, he added, was perhaps the most important part of the process.
“You learn more from what didn’t work than you do from what works,” he said. “I think you learn more from your failures than from your successes. You want to know why. I always like to test things until they fail, and then I know why they fail.”
Still going strong
Stewart, who turns 80 in September, commutes 35 miles to the NASA Ames Research Center in Moffett Field each day for work, as he has done since 1967. He said he is continually fascinated with his job.
“I’ve covered a lot of different areas,” he said. “I am still completely interested and very fortunate that I've worked this long.”
He remembers the “olden days” when a roomful of women used slide rules to complete calculations.
“Computers really sped that process up,” he said with a smile. “But the physics are still important to understand.”
Like any engineering breakthrough, TUFROC remains a work in progress.
“We’re improving it as much as we can,” he said. “We just started on this type of technology, and I don’t know if I’m gonna be here, but somebody will pick it up and carry it on.”
April Short is a freelance writer. She can be reached by sending email to firstname.lastname@example.org.