Covers developments in engineering materials selection, processing, fabrication, testing/characterization, materials engineering trends, and emerging technologies, industrial and consumer applications, as well as business and management trends
Issue link: http://amp.digitaledition.asminternational.org/i/466012
CAsE sTuDY oRion HEAT sHiElD HAnDlEs ExTREmE TEmps H ave you ever imagined how hot it would be at the Earth's core? What about stepping on molten lava? The Orion spacecraft built by Lockheed Martin endured those temperatures (and higher) when re-entering the terres- trial atmosphere late last year. Boosted to an altitude of 3604 miles, Orion fell back to Earth on December 5 at nearly 20,000 mph. During re-entry, Orion's heat shield protected the vehicle from external temperatures of 4000°F—nearly half the heat of the sun's surface. The heat shield is the forebody or wind-facing side of an aeroshell system. Due to its size, the aeroshell experiences tremendous entry loads as a result of dynamic pressures from the atmosphere and the high velocity of vehicle descent. Lock- heed Martin constructed all eight of the aeroshells that have protected NASA's Mars-bound space- craft—but Orion is unique. At 16.5 ft in diameter, it is the largest composite heat shield ever made. Orion is also designed for long-duration, human exploration of deep space. That means the shield will play a critical role in pro- tecting future astronauts on their return to Earth. Not only is the new heat shield the largest ever built, it also fea- tures a unique resin system that can withstand higher temperatures and landing impact. After testing in ex- treme environments and simulating re-entry, engineers verified that the thermal insulator on the outside of the composite material could be thinner, making the spacecraft lighter and allowing more payload to join the mission. The resin was developed by the Lockheed Martin Orion thermal protection system team in partnership with TenCate Advanced Composites, Morgan Hill, Calif. The heat shield is built around a titanium skeleton and carbon-fiber skin that gives the shield its shape and provides structural support for the crew module during descent and splashdown. A fiberglass-phenolic honeycomb structure fits over the skin, and each of its 320,000 cells is filled with a ma- terial called Avcoat. The surface is designed to burn away, or ablate, as the material heats up, rather than transfer heat back into the crew module. At its thickest, the heat shield is 1.6-in. thick, and about 20% of the Avcoat will erode as Orion travels through Earth's atmosphere. TEsT pARAmETERs During the high orbital test flight, Orion traveled a total of 60,000 statute miles and as far out as 3600 statute miles Fig. 1 — At 16.5 ft in diameter, the Orion heat shield is the largest composite version ever made. oRion HEAT sHiElD DETAils: • The Orion heat shield is the largest ever made. • The melting point for titanium is about 3000°F and the surface temperature of the sun is about 10,000°F. Orion can handle temperatures around 5000°F. • Orion must withstand landing loads of 300,000 to 400,000 lb, roughly equivalent to the mass of a school bus crashing into the ocean at 20 mph. a d v a n c e d m a t e r i a l s & p r o c e s s e s | F e B r U a r Y 2 0 1 5 | i T S S e 1 1 iTSSe | TSS Fig. 2 — Engineers attach the heat shield to the Orion spacecraft.