When NASA's Orion deep space capsule makes its next unmanned flight, it will be a bit shinier thanks to a new thermal coating. The new coating and an improved heat shield will protect the spacecraft against the extremes of heat and cold that it will encounter on its journey, as well as from the heat of reentry when it returns to Earth.
The next Orion mission, Exploration Mission-1 (EM-1), is scheduled for late 2018. After launching atop the Space Launch System rocket, Orion will spend three weeks on a circumlunar mission before returning at speeds faster than those of the previous first test flight in December 2014 when the capsules reentered at 30,000 ft/s (9,100 m/s) and generated temperatures of 4,000° F (2,200° C). During EM-1, Orion will strike the Earth's atmosphere at 36,000 ft/s (11,000 m/s) and generate exponentially greater temperatures.
According to the space agency, the new silver coating is needed to help protect the capsule not only during reentry, but also from the the wide variations in heat and cold that it will encounter on its short mission.
NASA says that the silver, metallic-based thermal control coating will be bonded to the crew module's back shell tiles. Its purpose is keep the capsule shell at a temperature between minus 150° and 550° F (minus 101° and 288° C). The coating is needed because in the vacuum of space sunlight heats the exposed side of a spacecraft while heat radiates away from the dark side. The silvery coating cuts down this radiation while reflecting away sunlight. In addition, it helps to prevent the capsule from picking up a dangerous electric charge.
"You're trying to hit this sweet spot because when you're looking at the sun, you don't want to get too hot, and then when you're not looking at the sun and instead in darkness, you don't want to lose all the heat that the spacecraft generates," says John Kowal, NASA's thermal protection system lead for Orion.
Along with the new coating, NASA is improving the main heat shield. Based on lessons learned from Orion's first flight, the new shield has a lighter support structure made of a titanium skeleton and carbon fiber skin. An analysis of the pressures on different areas of the shield allowed engineers to optimize the thickness of the skeleton and the skin.
Another development is a new streamlined manufacturing process aimed at reducing the labor needed to build the heat shield. Instead of building the plastic shield in a single monolithic outer layer, it will be divided into about 180 cell blocks that can be constructed simultaneously.
NASA says that Lockheed Martin has completed a test version of the shield, and that the shield that will fly on EM-1 is currently under construction.
"Orion's thermal protection system is essential to successful future missions," says Kowal. "As we move toward building the system for EM-1, we've been able to take advantage of what we learned from building and flying Orion to refine our processes going forward."
Source: NASA
