by Steven Siceloff
NASA’s John F. Kennedy Space Center
Workers recently began cutting and coating the first thermal protection system tiles – part of the heat shield that will protect an Orion spacecraft during an upcoming flight test which will simulate the re-entry speed and heating of returning from deep space.
The tiles are made of the same material and coating as those used on the space shuttle’s belly. On Orion, however, the tiles will be placed along the sides and top of the conical spacecraft. A separate heat shield akin to the ablative design used during Apollo is being developed to protect the bottom of the spacecraft, which will encounter the highest temperatures.
The manufacturing work at NASA’s Kennedy Space Center, Fla., marks an important time in the progression of the spacecraft following the shuttle’s retirement in 2011, said Thermal Protection System, or TPS, engineers Joy Huff and Sarah Cox.
“We’re making something that’s going to fly again, which is what we were doing for years,” Huff said.
There are about 40 people involved in the tile work: 20 to make the tiles and 20 to install them.
“We’re at the starting line,” Cox said. “It’s going to take some time to get all the parts fabricated.”
The same shop that manufactured space shuttle tiles will make the 1,300 tiles needed for the Orion flight.
It is not fast work. In fact, workers will spend about 11 months shaping the insulating blocks and laying on a heat-resistant, ceramic coating. They use a 5-axis mill loaded with precise dimensions to cut blank tiles to their shapes. So far, the shop has finished 33 tiles.
Many of the tiles will have special cutouts for instruments to collect data during the flight test. Many fewer cutouts will be needed for future missions.
In an advancement from the shuttle days, each tile’s dimensions are sent over digitally from Orion builder Lockheed Martin and the final tile is photographed with a 3-D camera so computers can fit the pieces together virtually before they are placed together physically, Huff said. The details are far more exact than in the past.
“They’ve had such good success that (technicians) are going to eliminate one pre-fit step,” Huff said.
The comparisons with the tile work for the space shuttles are plentiful. For example, the smaller Orion uses tiles that average 8-inches by 8-inches compared to the shuttle’s 6-inches by 6-inches. Also, Orion’s design allows for many of the tiles to be the same dimensions with the same part number, but each shuttle tile was a unique configuration unto itself, with individual part numbers.
“That’s a huge improvement over shuttle,” Huff said. “Even having nine or 10 of the same part is a big improvement.”
Perhaps the biggest comparison, though, is the sheer number of tiles involved. A space shuttle heat shield required more than 23,000 tiles to the Orion’s 1,300.
“It’s smaller, so there’s less parts,” Cox said.
However, Orion’s tiles will be used only once because the spacecraft will splashdown in the ocean, drenching the absorbent tiles. That means that technicians will make and install all 1,300 tiles between Orion missions. Shuttles required 100 to 150 new tiles between flights, Cox said.
Technicians who applied the tiles for the shuttle will bond Orion’s tiles, too. That work will start sometime in the summer. The tiles will be connected to nine panels that will be connected to the spacecraft to make the outer skin of the spacecraft.
Although it’s a new spacecraft with a new mission, it still calls for many of the same skills the work force at Kennedy used for 30 years of shuttle preparation.
Orion is expected to see significantly hotter re-entry temperatures because it will be slowing down from about 25,000 mph when returning from the moon or some other deep space destination. Space shuttles used their heat shields to slow down from about 17,000 mph, the speed required to stay in orbit around Earth.
“The heat shield has been a very technological challenge and it will continue to be,” said Huff, who has been working Orion’s TPS development since 2005.
To get to this point, when tiles are being cut that will be used on a mission in space, has given the project more of a sense of being real, the engineers said. They know there is plenty of hard work ahead, but they are happy to see it start.
Huff said, “It’s almost a sprint feeling, but it’s a marathon length.”