What Happens after the International Space Station is Retired: the Future of Space-based Microgravity Research

As plans for the end of ISS are being made, Aerospace Chief Technology Officer, Dr. David Miller, looks at the progress and the future of space-based microgravity lab facilities.

The Aerospace Corporation
4 min readJun 3, 2021
The International Space Station has served as a critical laboratory for microgravity research. (Credit: NASA)

Technology research is no longer solely a terrestrial endeavor. Crucial interactions between the zero gravity environment and the physics of spacecraft can’t be replicated in a 1-G environment on Earth. A benefit of human space exploration has been the ability to test space innovations in the environment where they will eventually operate.

Critical space-enabling technologies have been developed in the microgravity labs aboard space stations including Mir, the Space Shuttle, and most notably the International Space Station (ISS). Long-duration microgravity experiments, impossible to perform by traditional means, have been successful only because of the modular hardware and software design of these facilities.

In the same way researchers might use a wind tunnel, the microgravity environment in on-orbit facilities permit early phase technology to be tested to its limits without harm to the testbed, the operator, or the human-rated vehicle under the conditions expected in space — an essential step to identifying the limits of knowledge and capabilities and to focus future investment in space technology.

The Middeck 0-g Dynamics Experiment (MODE), developed through NASA support, helped pioneer the use of the Shuttle middeck as a research laboratory and was among the first US experiments in the Shuttle-Mir program. MODE flew on two Shuttle missions, STS-48 in 1991 and STS-62 in 1994. (Credit: NASA)

In my career, I’ve had the opportunity to help develop three micro-gravity technology research facilities, studying the dynamics of the physical structures of spacecraft and the control actuators used for spacecraft stabilization and maneuvering.

The primary mirror of the James Webb Telescope (Credit: NASA)

Testing in a real microgravity environment has led to numerous critical and highly visible advancements, such as understanding the structural stability during temperature changes associated with the large primary mirror on the James Webb Space Telescope. Fuel slosh testing in microgravity has been essential for understanding the stability of spinning launch vehicle upper stages. The Middeck Active Control Experiment (MACE) developed spacecraft attitude and vibration control systems that learn from measurements taken on orbit in order to autonomously improve spacecraft pointing and steering performance.

The NASA-funded Middeck Active Control Experiment (MACE) added high-speed active control, used to develop high bandwidth robust control of multi-instrument pointing systems on a flexible structure. MACE was the first experiment inside the ISS in collaboration with the AFRL, Space Vehicle Division. (Credit: NASA)

As the first free-flyer experiment inside ISS, SPHERES is a national facility supporting dozens of researchers from academic, industrial, and governmental organizations. SPHERES free-flyer dynamics allow astronauts on the ISS to collaborate directly with researchers on the ground.

The SPHERES facility includes remotely-operated robots capable of conducting Intra-Vehicle Activity (IVA) inside the space station. (Credit: NASA)

The SPHERES lab not only serves as a research facility but as a tool to inspire the next generation. For over a decade, SPHERES has been host to Zero Robotics, an international STEM robotics and coding challenge for over 20,000 middle and high school students worldwide. Student teams learn to program the SPHERES robots and compete against each other virtually on board the ISS.

As the ISS is expected to be retired later this decade, the next generation of Low Earth Orbit facilities is currently in development. These will likely be funded, at least in part, by commercial space entities in partnership with government. The Defense Department recently awarded study contracts to three companies to analyze small, unmanned space stations, or “orbital outposts” in Low Earth Orbit.

NASA has opened up next-generation station planning to industry, allowing the space agency to prioritize its requirements in the development of privately-owned space stations. In these scenarios, NASA could operate as a station tenant rather than an owner, which could both accommodate agency budget priorities and serve the commercial desire for research facilities, potentially driving entirely new markets for space services.

Our work in space has only just begun.

Dr. David W. (Dave) Miller was vice president and chief technology officer (CTO) at The Aerospace Corporation, from 2018–2022, providing vital leadership for the company’s growing prototyping efforts through his supervision of Aerospace’s Experiments Lab (xLab), Aerospace’s innovation laboratory, the Engineering, Science & Technology Hubs; and the Tech Fellows program. Prior to joining Aerospace, Miller was director of the Space Systems Laboratory and the Jerome C. Hunsaker Professor in the Department of Aeronautics and Astronautics at the Massachusetts Institute of Technology.