In microgravity, even seemingly indestructible materials degrade. Just look at the Hubble telescope, where its outer layer of insulation and thin layer of aluminum encasing have become so embrittled they are cracking and curling.
Without question, space is a harsh place where radiation, temperature extremes, orbital debris, and atomic oxygen (the presence of highly reactive single-oxygen atoms) flourish.
A new permanent test bed is now available on the exterior of the International Space Station (ISS) that allows investigators to analyze the durability of materials one sample or experiment at a time in the extreme space environment. The remotely controlled platform, the Materials ISS Experiment Flight Facility (MISSE-FF) from in-orbit commercial services provider Alpha Space Test & Research Alliance, LLC, aims to accelerate the testing of materials and components that have utility both in space and on Earth.
Building on NASA’s Legacy of Innovation
MISSE-FF, which launched on the 14th SpaceX commercial resupply services mission in April 2018, builds on two decades of innovation by NASA. When the space shuttle was operating, NASA flew eight MISSE missions to the ISS, the last of which returned to Earth in 2014. The new MISSE design uses carriers to hold the experiments, which are launched and returned with each mission. Carriers from the current mission, MISSE-9, using the new MISSE-FF platform, are currently scheduled to return to Earth in December 2018 and April 2019.
In contrast to earlier MISSE missions, in which astronauts installed MISSE payloads on the outside of the ISS during a spacewalk and then later retrieved the experiments the same way for return to the ground, MISSE-FF is a permanent fixture on the space station. The platform’s individual experiment carriers are installed and removed using the robotic Canadarm2. Approximately 40 percent of the platform is reserved for NASA experiments, with the remaining 60 percent available for commercial use.
“Our business model and the MISSE-FF platform significantly broaden access to space and enable commercial enterprises to get to low Earth orbit (LEO),” said Mark Gittleman, president and CEO of Alpha Space. “We make it inexpensive and easy to test new materials, components, and technologies in space with help from NASA and the ISS National Lab, which, together with Alpha Space’s great team, enable our business model.”
Research and development projects included in MISSE-9 will advance both space exploration and Earth-based innovations in solar technology, remote sensing, telecommunications, and other fields. MISSE-9 includes a suite of investigations, with samples including 3D-printed materials, sensors, sensor components, textiles, carbon-fiber laminates, paints, coatings, polymers, and composites. Within the first few weeks of MISSE-FF operation, Alpha Space had already received 1.2 million data packets (a unit of data made into a single package for transmission), including imagery of samples in various flight orientations.
“We built the MISSE-FF platform in less than three years, and now that it’s onboard the ISS, it’s running spectacularly,” said Alpha Space founder Stephanie Murphy, who brought together a team of engineers with prior MISSE experience to build the platform.
Murphy also leads MEI Technologies, a government contracting firm established in 1992 by Murphy’s father as Muñiz Engineering, Inc. MEI Technologies originally won the contract to privatize the MISSE platform, but it was Murphy’s idea to spin off Alpha Space into a standalone firm.
Driving New Understanding and Breakthroughs
Results from MISSE-9 investigations will not be fully realized until after the MISSE sample carriers housing the experiments return in winter 2018 and spring 2019 and samples or components are analyzed, but historical MISSE investigations have a legacy of advancing understanding and innovation in several industries on Earth.
For example, research on surface oxidation by atomic oxygen informs the design of fire-retardant and rust-resistant materials on Earth. Interactions between various materials and solar ultraviolet radiation could lead to better protective designs for communications and weather satellites and may help improve terrestrial structures, such as plastic siding for houses.
In addition, because true space environmental conditions are difficult to replicate on Earth, MISSE provides a valuable test platform that enables methods for correlating and extrapolating ground results. “That means that MISSE experiments can make ground testing more accurate and reliable,” said MISSE researcher Kim de Groh from NASA’s Glenn Research Center.
Most notably, of course, MISSE missions have provided space-environment durability data that enables the design of new, even more reliable spacecraft and innovative new structures for use in harsh environments both on and off Earth. Today’s satellites that are relied upon by hundreds of millions of people for Earth observation, weather, and communications were developed with materials tested in space on earlier NASA-led MISSE and related exposure missions.
These established benefits are appealing to a broad customer base. “We’ve attracted some really diverse initial clients,” said Murphy. “We’re in a lucky place where we can invite new users to the ISS National Lab, but our expenses are still being subsidized through the ISS National Lab and NASA. It’s a short-term incentive to bring entities and entrepreneurs into the fold that haven’t been there before.”
Besides traditional materials testing (e.g., paint, coatings, fabrics, and materials for 3D printing), Murphy noted that Alpha Space has had strong interest from customers studying “exobiology,” or the behavior of living things in the external space environment; for example, biological firms focused on medical applications.
“We’ve got people who want to fly biofilms and neurological cells for radiation testing,” Murphy said. “Others have interest in flying plants and seeds to test radiation exposures. They want to see if they grow plants on Mars and how radiation will affect their plant growth or seed germination.” This diversity of interest has led the company to embrace the slogan: “If it fits, it flies.”
A biofilm is an assemblage of microbial cells attached to a surface and enclosed in a self-produced matrix of compounds that protect the microbes from the environment.
An Unparalleled Platform for Tech Demo
Firms wishing to demonstrate or test their space technology components and equipment in LEO are particularly drawn to the MISSE-FF platform. Two such technology demonstration experiments on MISSE-9 involve testing glass-free packaging for solar cells and assessing the robustness of optical receivers for communication in the harshness of space.
One experiment is from New Jersey-based Discovery Semiconductors, Inc., which makes fiber-optic modules and receivers for telecommunications, the military, and now LEO space applications.
“Demand for data bandwidth, which has been strong for terrestrial applications for many years, has started to migrate to space platforms,” said Abhay Joshi, owner of Discovery Semiconductors.
Joshi previously flew his fiber-optic components on MISSE-7 and has continued with the current MISSE-9 mission. He hopes the latest tech demo—involving two indium gallium arsenide high-end space receivers—will enhance the technology readiness level (TRL) of his company’s components.
Technology readiness level (TRL) is a system used to rate the maturity level of a technology on a scale from one to nine, with TRL-1 being observation of basic principles and TRL-9 being proven through successful operations
“The MISSE-FF platform is highly desirable because it allows me to get some of my components up in space and see how they withstand vibration, shock, rocket launch, and re-entry, as well as the extreme vacuum and temperatures of space,” said Joshi, whose receivers are used for communications and remote-sensing applications. “MISSE-FF is an ideal platform to check the space worthiness of new devices.”
The materials of the future and the component systems in which they are used are going to need to pass even more rigorous testing in extreme environments in order to operate and remain functional as they shrink in size and power consumption but increase in complexity and capability. The small satellite revolution is driven by advances in material performance and technologies proven in the harshness of space.
Like Joshi, Aarohi Vijh also sees value in the MISSE-FF platform for his technology components. Vijh heads new product definition and technical marketing for Alta Devices, a solar technology company in Sunnyvale, California. The company was founded 10 years ago by two researchers: Harry Atwater, of the California Institute of Technology, and Eli Yablonovitch, of the University of California, Berkeley.
Vijh and his team are studying a special kind of solar cell based on gallium arsenide (GaAs). GaAs solar cells were first developed in the early 1970s and have several unique advantages. GaAs is naturally robust to moisture and radiation, making it very durable. It has a wide and direct band gap allowing for more efficient photon absorption and high-output power density.
To create glass-free packaging for these solar cells so that they are lighter, less fragile, and better able to operate in space, Alta Devices tapped into years of NASA performance data on various plastics and polymers flown in space on MISSE missions. “In developing our own packaging solution, it made it a lot easier to look at what had already been done and proven,” Vijh said.
Alta Devices already supplies its thin and flexible solar cells to the automotive sector and to the unmanned aerial vehicle market, especially for single-junction solar-powered aircraft. Alta Devices holds the world record for solar efficiency, generating very high power per unit area. For small, unmanned systems, Alta Device’s AnyLight™ power technology provides unmanned systems as much as five times more daytime endurance, and at one gram per watt of power, it has virtually no impact on weight or aerodynamics.
Vijh plans to continue to use the MISSE platform to evaluate his firm’s innovative solar arrays. “It’s a very powerful statement to make to our customers that our solar panels and packaging have actually been on a space flight with a credible provider,” he said.
Vijh sees applications on the ground as well. “The solar cells receive very high environmental exposure in space—ultraviolet rays and temperature cycling,” Vijh said. “The materials and our manufacturing techniques that we’re qualifying on MISSE will carry over to applications on the ground in the automotive industry and near-space applications such as high-altitude aircraft.”
Looking to the Future
On the NASA side, both de Groh and Sheila Thibeault, a member of the Advanced Materials and Processing Branch in the Research Directorate at NASA’s Langley Research Center, have experiments not only on MISSE-9 but also on MISSE-10, which recently launched to the ISS on Northrop Grumman CRS-10.
Thibeault served as an original founder of the MISSE project back in 1999, building the initial hardware used on MISSE-1 through MISSE-8. She also assisted with the redesign of MISSE to be remotely controlled, eliminating the need for spacewalks, and she and de Groh both advocated for a permanent MISSE platform on the space station.
“I’m really excited about MISSE missions continuing under Alpha Space leadership,” said Thibeault. She recalls how her team often had to take the machining of the carriers to NASA Langley’s machine shop, which was time consuming and involved some cost, and had to oversee quality control for incoming specimens from external partners, which also took time and resources.
“Alpha Space is making our life easier,” Thibeault said. “I can focus on my materials and the science and don’t have to worry about the platform or the specimen holders, which is all being taken care of for me.”
While it is still early in the platform’s performance history, Alpha Space executives believe the future is bright for MISSE-FF as a permanent test bed that will have a lasting impact on the quality of life at home and in space.
“Space represents a crucial economic sector for the United States, and Alpha Space is leading the way to help NASA and the country achieve the very important policy of commercializing LEO,” said Gittleman. “We are doing it alongside traditional NASA space science, which I think will enable improvements to the U.S. space industry supply chain while simultaneously making LEO more accessible than ever before.”