Smallsat developers focus on improving reliability
August 8, 2018 | Space News
LOGAN, Utah — As cubesats and other smallsats transition from technology demonstration and student projects to operational missions supporting a growing array of applications, companies large and small are working to improve their reliability. Those efforts, outlined in a session of the AIAA/Utah State University Conference on Small Satellites here Aug. 7, reflect as much the philosophical differences of the companies involved as the specific technical issues that affect satellite reliability.
The on-orbit performance of cubesats has long been a sore point. In a presentation at a pre-conference workshop Aug. 4, Lee Jasper of the Space Dynamics Laboratory noted that, historically, 22 percent of cubesats were never heard from after launch. That figure is significantly higher in special cases, such as some classes of university-built cubesats.
Companies developing constellations of cubesats, though, have much lower failure rates. Spire, which operates a cubesat constellation that provides weather and vessel tracking data, launched 47 satellites in 2017 using a cubesat design developed internally and incrementally improved over the last several years.
“We’ve learned the hard lessons over the last six years or so,” Jeroen Cappaert, a co-founder of Spire, said. “We’ve built a robust satellite bus that is flexible and can be integrated with a variety of payloads.”
Those improvements, he said, are enabled by vertical integration. Spire controls every part of the satellite product chain from manufacturing through the provision of data and services, with the exception of launch. That allows the company to iterate designs quickly, improve reliability and control costs.
Cappaert said Spire is now considering providing mission services to companies, who they would fly their payloads on Spire satellites. “We think of Spire today as a data provider, but we’re also a mission provider,” he said. “We’ve built all this infrastructure and we think we can provide value to other companies that don’t necessarily want to spend the time and capital building all this from scratch.”
NanoRacks subjects the cubesats it deploys from the International Space Station to an additional set of reviews to meet NASA human safety requirements, said Henry Martin, senior external payloads mission manager at the company. Those requirements address a variety of issues, from toxicity of materials to the design of batteries on those cubesats, to ensure the safety of crews on the station, but in many cases can also improve mission reliability.
The company has, to date, deployed 223 satellites from the ISS, and Martin said that those technical issues usually aren’t a major problem for developers compared to regulatory issues like FCC licenses. “The largest issue as to why they miss [their launch date] is that they don’t have a license,” he said.
Companies moving from large satellites to smaller ones face a different set of challenges. James Loman, senior distinguished engineer at Space Systems Loral, noted his company has extensive lessons learned from developing large geostationary orbit communications satellites that has improved their reliability. He said that 20 years ago, the average satellite the company built had two “unit failures” of various components in the first year after launch. Today that failure rate is 10 times lower.
He acknowledged, though that those lessons can’t be directly applied to smaller satellites that are intended to be less expensive and built more rapidly. “We will continue to use some of our heritage processes that ensure high reliability and quality, but we’ll need to be scaling back to meet ‘new space’ expectations,” he said.
Among those trade-offs is the use of commercial off-the-shelf (COTS) components for some low Earth orbit smallsats versus radiation-hardened, but more expensive, items. “COTS parts are probably OK for LEO short-duration missions,” he said, but urged radiation testing of those components for the given mission profile. “Otherwise that will cause problems.”
“We need to transition from ‘old space’ to ‘new space,’” he said, “but we need to do it in a manner so we do not forget all the lessons learned and meet the expectations of commercial customers.”