Workers to add structural braces to Orion spacecraft
BY STEPHEN CLARK
Posted: January 23, 2013
Engineers plan to beef up the structure of the first space-bound Orion spacecraft after discovering cracks in testing last year, but officials say the extra work should not delay preparations for the capsule's first orbital test flight in 2014.
NASA is developing the Orion spacecraft, also called the multipurpose crew vehicle, for future human voyages into deep space to destinations such as the moon, asteroids and Mars.
The first Orion spacecraft built for spaceflight is undergoing assembly and testing inside the Operations and Checkout Building at NASA's Kennedy Space Center in Florida. It will launch in September 2014 on a United Launch Alliance Delta 4-Heavy rocket, reaching a top altitude of 3,600 miles on an unmanned test flight to test the capsule's avionics, heat shield and other systems.
The Orion test flight, named Exploration Flight Test-1, will culminate with a parachute-assisted splashdown in the Pacific Ocean.
In November, during a test of the capsule's pressure integrity, three small cracks appeared in the aft bulkhead on the lower half of the vehicle's pressure shell. The cracks materialized in three adjacent radial ribs of the aluminum bulkhead.
Technicians overseeing the pressure test stopped the procedure after hearing noises attributed to the cracking, according to Bill Gerstenmaier, NASA's associate administrator for human exploration and operations.
"It turns out there was an area in the crew module where we underestimated some things like shrinkage of the welds and behavior of some of the materials," Geyer said Jan. 16. "In that case, we didn't realize we were closer to the margins than we expected in one area of the vehicle. We had cracks that were maybe half of an inch big. They never penetrated the pressure vessel, but you don't want cracks and that's why we did the test."
"We've come up with a great plan to basically bridge over those cracks to distribute the load so we don't see any issues on orbit," Geyer said.
The fan-shaped doubler will distribute loads across a wider area of the spacecraft's structure. Workers will install the doubler ahead of a planned pressurization and loads test in mid-February, according to Geyer.
"We have the design," Geyer said. "We're finalizing the analysis now to make sure we're not making the stress load worse in other areas as we bolt these things on. That's normal when you do a doubler on an aircraft or spacecraft."
The February loads test will ensure the repair works before engineers add avionics boxes, parachutes, a heat shield and other systems later this year.
The schedule calls for the heat shield, which will cover the blunt end of the 16.5-foot-diameter Orion spacecraft, to be installed this summer. The first power-up of the capsule's avionics is also expected around the middle of the year, according to Geyer.
Workers are also fabricating a mock service module and a partially-inert launch abort system for the 2014 test flight.
Geyer said preparations are on track to complete assembly and testing of the Orion spacecraft by the end of 2013. There are several months of margin in Orion's schedule before the launch opportunity in September 2014.
"Toward the end of the year, we'll finish and get ready to deliver the element to the launch vehicle folks," Geyer said.