To develop spacecraft that can "maneuver without regret" the U.S. Space Force is providing $35 million to a national research team, including Cornell engineers, that will be the first to bring fast chemical rockets together with efficient electric propulsion powered by a nuclear microreactor.

Credit: Provided

The newly formed Space Power and Propulsion for Agility, Responsiveness and Resilience Institute, led by the University of Michigan, involves eight universities and 14 industry partners in one of the nation's largest efforts to advance space power and propulsion, a critical need for national defense and space exploration.

Most spacecraft propulsion comes in one of two flavors: chemical rockets, which provide a lot of thrust but burn through fuel quickly, and electric propulsion powered by solar panels, which is slow and cumbersome, but fuel-efficient. 

To power faster, efficient electric propulsion, one of the institute’s subteams is developing a concept for a nuclear microreactor, exploring the early feasibility of a new path for safe, reliable and sustainable nuclear power for space. Others subteams will build technologies to turn the heat from a microreactor into usable electricity, and electric engines to turn the electricity into thrust.

Each piece of the prospective system, and the way the pieces connect, presents intriguing challenges for the research teams, which combine academic and small business partners to pave the way for commercial manufacturing. 

Sadaf Sobhani, assistant professor of mechanical and aerospace engineering at Cornell and principal investigator for the institute’s heat rejection subteam, is leading the development of lightweight, deployable and modular radiators. These radiators are equipped with embedded heat pipes, made possible through cutting-edge ceramic additive manufacturing techniques. In partnership with Advanced Cooling Technologies and Ultramet, the team aims to utilize low-density, high thermal conductivity ceramics such as aluminum nitride, optimized working fluids, and ultra-high-emissivity coatings to maximize heat rejection efficiency.

“Our goal is to create a system that’s not only efficient but also adaptable, providing future missions with the flexibility they need to operate in diverse environments,” said Sobhani, whose Architected Thermofluidics Lab specializes in thermal management and energy conversion technologies. “This project pushes the boundaries of what’s possible in spacecraft thermal management by integrating innovative design and advanced materials and manufacturing.”

Fabien Royer, assistant professor of mechanical and aerospace engineering and co-investigator for the heat rejection substeam, brings critical expertise in deployable space structures. His Cornell Space Structures Laboratory is developing the lightweight deployable structural backbone that supports the ceramic radiator tiles. “This structure combines three seemingly contradicting characteristics: extremely low-mass, high-packaging efficiency when folded inside the rocket fairing, and high stiffness when deployed on orbit,” Royer said. 

Elaine Petro, assistant professor of mechanical and aerospace engineering at Cornell, is principal investigator for the institute’s propulsion modeling subteam, which consists of collaborators across the universities of Michigan and Colorado Boulder. Together they will develop comprehensive numerical models of the operation of the electric thrusters.

The outcome of this research will include models that accurately capture the complex plasma chemistry and transient dynamics in the thrusters, which use new throttle ranges and novel propellant mixtures like water and ASCENT – an advanced monopropellant formulation developed by the Air Force Research Laboratory. These tools will enable researchers to diagnose and mitigate inefficiencies in the propulsion systems that are difficult to detect experimentally and help to optimize engine performance across a range of operating conditions.

“We are thrilled to be a part of this research institute and to lead in these key areas of propulsion modeling and heat rejection,” said Petro, who directs the Advanced Space Technology Research and Architectures Lab at Cornell. “Space power and propulsion architectures had not changed very much since the 1970s up until now. The new ideas and operations concepts that will be developed by the SPAR team could enable radically new approaches and capabilities for space exploration.”

Benjamin Jorns, University of Michigan associate professor of aerospace engineering is serving as the institute’s director.

Other universities involved include the University of Washington, University of Colorado Boulder, Princeton University, University of Wisconsin, Western Michigan University, Colorado State University, and Pennsylvania State University. Industry partners include Ultrasafe Nuclear Corporation, Antora Energy, Spark Thermionics, Ultramet, Cislunar Industries, Champaign Urbana Aerospace, Benchmark Space Systems, Advanced cooling Technologies, NuWaves Inc., and Analytical Mechanics Associates. Northrop Grumman, Lockheed Martin, Westinghouse and Aerospace Corp. form the advisory board.

This article was adapted with permission from a version written by Katherine McAlpine and published by the University of Michigan.