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NASA, in its mission to send a craft to explore Titan, one of Saturn鈥檚 many moons, faced a dilemma. Dragonfly, the rotorcraft that will explore Titan, needed a heat shield to survive a two-hour descent.

Heat shields used on previous spacecraft were made of PICA-D, or Phenolic Impregnated Carbon Ablator-Domestic, developed by NASA鈥檚 Ames Research Center in California. But one of the precursors that goes into the material was not in production anymore, said Milad Mahzari, an aerospace engineer for NASA at the Ames Research Center.

鈥淚t鈥檚 really hard to make that material sustainable because there鈥檚 a lot of different ingredients that come from different sources, and if one of the companies goes out of business and they stop producing things, you鈥檝e got to reformulate it,鈥� Mahzari said.

So they turned to Sandia National Laboratories鈥� National Thermal Test Facility, a 10-acre site first commissioned in 1978 that includes a field of heliostats 鈥� essentially tracking mirrors that can reflect sunlight toward a fixed target. When scientists point the heliostats to concentrate sunlight in an area atop the solar tower, temperatures from the pulse can reach up to 4,500 degrees. That is well above the conditions predicted for Dragonfly鈥檚 entry, Sandia officials said.

Mahzari said the team not only had to test whether the newly constituted material could withstand extreme heat, but also had to test how a large-enough surface area of the shield reacts under heat, because when Dragonfly enters Titan鈥檚 atmosphere, 鈥渢here鈥檚 mechanical stress that you鈥檙e putting on the material.

鈥淪o the combination of those two things is what really worried us,鈥� he said. 鈥淎nd we wanted to be able to test that, and the only place we were able to test that is at Sandia.鈥�

Testing turned out to be a multiyear effort that began in 2023. During each visit, the teams conducted up to eight tests, rigging tiles of the heat shield material onto a 24-inch area on top of the 200-foot solar tower. The team also flowed inert gas over the heat shield samples to better replicate Titan鈥檚 atmosphere.

The NASA team said it selected Sandia鈥檚 National Solar Thermal Test Facility because it is the only ground qualification facility that can reproduce the predicted amount of heat Dragonfly will face on a test article large enough to generate flight-like stresses in the material, Sandia officials said.

Ken Armijo, Sandia鈥檚 lead engineer and test director for the campaign, said there are only five solar test towers in the world, adding that Sandia鈥檚 is the only one in the western hemisphere that does this type of work.

鈥淲e did a lot of tests spanning about three years with NASA,鈥� Armijo said. 鈥淲e鈥檝e got a lot of good lessons learned and best practices. We even did upgrades to our solar tower to facilitate this ground-based testing campaign.鈥�

Titan, discovered by a Dutch astronomer in 1655, is Saturn鈥檚 largest moon, about 50% wider than Earth鈥檚. It is the only place besides Earth to have liquids on its surface, according to NASA.

NASA plans to launch Dragonfly in July 2028. It is set to arrive on Titan in late 2034.

鈥淚t has clouds, rain, rivers, lakes and seas of liquid hydrocarbons like methane and ethane,鈥� . Measurements taken by flights that have passed Saturn, in fact, 鈥渞evealed that the moon is hiding an underground ocean of liquid water鈥� likely mixed with salts and ammonia.

Mahzari said the tiles for the heat shield are complete and that Lockheed Martin will install the tiles.

鈥淜en (Armijo) and his team did a lot of good work with just pointing the heliostats because we were really pushing them to their limits,鈥� Mahzari said. 鈥淲e basically needed all of the juice that they could get out of this field to get to our conditions.鈥�

Justin Horwath covers tech and energy for the Journal. He can be reached at jhorwath@abqjournal.com.