Industry Standards for Commercial Spacecraft
Orbital flight places extensive demands on a spacecraft and its materials in ways designers must account for in order to achieve success. Just getting into space requires a vehicle that can tolerate the gravity loads of accelerating from a standstill to Mach 25 in a little more than 10 minutes, operate above Earth, where temperatures change by more than 500 degrees Fahrenheit every 45 minutes, and stand up to plasma heating of around 3,000 degrees F. High-frequency vibrations that simulate being inside an automatic paint can shaker for several minutes are another factor. And while all of this happens, the crew of astronauts must be kept healthy and safe.
Knowing those demands, the designers of Boeing’s CST-100 Starliner spacecraft have put years of work into making sure every tank, fitting, cable, and line is up to the challenge. This includes the pressure vessel itself, a two-piece design that gives the Starliner its capsule shape. It is the main structure of the vehicle; all of the spacecraft components, including the control system and life support for astronauts, brace to it in some way.
Each of the systems, subsystems, and their components require exacting detail in design and manufacturing before they are assembled into the complete unit.
Starliner was developed in partnership with NASA’s Commercial Crew Program (CCP), with the intention of creating a new spacecraft capable of safely, reliably, and sustainably taking astronauts to and from the International Space Station (ISS).
Unlike previous NASA programs, CCP called for the spacecraft design, operation, and even ownership to remain with its commercial partners rather than being government-owned and operated. NASA provided the requirements, but it was up to Boeing to determine how best to meet those requirements and deliver the desired capability. In response, Boeing drew upon industry standards developed by ASTM International for a host of materials and testing. Boeing also applied ASTM standards to guide its suppliers.
Boeing developed much new technology to fly the autonomous vehicle in orbit, connect it to a launch vehicle, and make connections between complex subsystems. But overall, the utilization of ASTM standards was an effective strategy that NASA selected for full development and operational services.
“For some parts of the system, we really didn’t need to drive up to the edge of new technology,” says Douglas Skinner, Boeing Systems Integration and Engineering lead for the Starliner program. “We assessed ASTM-developed standards, which are tried and true, and adopted those that allowed us to meet the requirements for a safe spacecraft system.
“For example, incorporating ASTM testing standards into our supplier requirements ensures our partners perform specific tests, and we know that what they’re delivering meets our expectations and specifications,” he adds..
Applying known standards saves resources ranging from employee time to supplier cost, so those resources can be deployed toward solving the unknown aspects of a spacecraft’s design. Using standards also helps ensure product safety.
A human-rated spacecraft crosses scores of industry standards throughout its design. Some relate to the digital systems: how a spacecraft’s computers talk to one another and then how they all talk to the systems aboard the ISS, for instance. Others focus on electrical systems. The standards that dictate best materials and how they are tested see significant scrutiny throughout development.
For example, the aluminum pressure vessel is made from two pieces of aluminum that are machined into the upper and lower domes and then bolted together to give Starliner its capsule shape. It contains the atmospheric conditions to sustain the astronauts during the mission and is built strong enough to survive the climb into orbit. It also provides a structure for all the thrusters, tanks, and flight computers the spacecraft uses, as well as a heat shield that can tolerate more than 3,000 degrees F on the way home.
Add in the stresses of operating in a vacuum for months at a time, where temperatures swing 16 times a day from 250 degrees F in the sunlight to -250 degrees F in Earth’s shadow, and it makes sense to evaluate the material as much as possible on Earth. That’s another area where ASTM standards come into play, this time with a dye penetrant to identify any flaws in the materials.
“We use these dye-penetrant examinations to make sure there are no cracks and the hardware will perform the way we designed it,” says Skinner.
When the first Starliner flew a test mission to orbit without a crew in December 2019 and returned to parachute to a landing in New Mexico, Skinner and the Starliner team got their first chance to see how the ASTM standards they’d applied so rigorously fared in the real demands of space.
“When we did post-flight inspections, we looked at the materials to see if they held up as expected,” he says. “They did, and the vehicle was in great shape to fly again and again.” ■
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