Engineering Next-Generation Heat Shields for Spaceships

By Teya Vitu –

Travel does not get more extreme than flying at Mach 5 or faster in an aircraft with sleek edges for daring maneuverability.

Passengers are rendered to crispy critters if every square inch of the aircraft surface cannot withstand 2,800 degrees Celsius.

Spacecraft re-entering the atmosphere for the past 50 years have dealt with the extreme heat with very rounded surfaces that can ablate the fiery blast.

“You have to have vehicle shapes that are not very maneuverable,” said Erica L. Corral, a University of Arizona materials science and engineering assistant professor. Think of space capsules or even the Space Shuttle. They aren’t exactly making wild turns while re-entering the atmosphere.

“There’s an aerospace need for a vehicle that can be maneuverable and fly at hypersonic speed.”

Corral is among a handful of scientists around the world collaborating to come up with the next-generation thermal protection systems for hypersonic flight exceeding five times the speed of sound – more than 3,200 miles per hour.

Since coming to the UA in 2008, Corral has worked with transitional metal borides and carbides to come up with ceramic coatings and discs that can best ward off oxidation in high-temperature, oxygen-rich environments at very high speed.

This entails concocting ceramic powder mixes, firing the powder up for a few minutes at 2,200 degrees Celsius in a spark plasma sintering furnace – and out emerge small, densified ceramic discs.

Withstanding extreme heat is not the challenge. The puzzle is how oxidation would affect the heat shields while flying at very high speed in the high atmosphere.

“We still need to understand how they behave at temperature. How does it react to oxygen at temperature?” Corral said. “We need to understand more about how they oxidize. We need to find the ceramic that’s best for oxidation.”

Corral and compatriots around the world are trying to simulate the flight environment of traveling at very high speeds high in the atmosphere. That cannot be replicated in a lab.

The hypersonic aircraft creates three atmospheric layers. Corral’s focus is on the oxygen-rich boundary layers nearest the aircraft. Other scientists are researching the shock layer and atmospheric layer. The trick is replicating all three layers simultaneously with an aircraft traveling at Mach 5. “There’s no way to do that on Earth,” she said.

Corral’s research focuses on providing thermal protection systems for the sharp maneuverable edges of the aircraft – the most vulnerable area to high heat.

“For everything else, there are materials ready to go,” Corral said.

A test flight vehicle should be ready by 2015 to give a real-life test for the next generation of heat shield panels.