As humans expand their ambitions in deep space, energy-intensive missions can't afford to rely solely on combustion or solar power. They will need nuclear energy for propulsion and surface habitation.
Jake Hecla '17, who holds a dual appointment as assistant professor in the Department of Nuclear Science and Engineering (NSE) and Charles Stark Draper Career Development Professor of Aeronautics and Astronautics ( AeroAstro ), is researching ways to address one of the principal heat transfer challenges in such deployments of nuclear power in space: a lack of atmosphere. He is also working on technologies to enable the deployment of aerospace reactors, observe their operational signatures from long range, and create the technical basis for future arms-control agreements limiting the weaponization of these systems.
Thermal management in space
The next generation of space nuclear reactors demand considerably higher power than past missions, requiring the conversion of heat to power, typically using a Brayton or Rankine cycle. Such conversions deliver efficiencies of around 30-40 percent in terrestrial applications - and a lot of heat that needs to be removed. Because there is no atmosphere to rely on for convection, engineers use radiators instead. But traditional solid metal or composite radiator panels are mass-intensive, a significant impediment for space applications.
One of Hecla's research projects at MIT addresses the limitations of an alternate solution: the liquid droplet radiator (LDR). First proposed by researchers at the University of Washington in the late 1970s, the LDR could be just as effective as conventional radiators, especially because their considerably lower weight is an advantage, helping radiators constitute just a fraction of the spacecraft's mass.
In place of solid panels, LDRs use sheets of liquid droplets to radiate heat away. The LDR works by spraying coolant from an emitter to a collector as sheets of tiny droplets. As these droplets travel through space, they radiate and cool. They then impact a collector, which then pumps the coolant back to the heat source in a cyclical operation.
The principle sounds straightforward, but droplet retrieval is often complicated by drifts introduced by charging, splashing at the collector, and emitter misalignment. Engineers can't afford to lose too many of them - acceptable loss rates could be one droplet in every million for a 10-year mission - because that will increase the coolant load that will need to be transported to space. (The rate might be small, but the radiator cycles the coolant every few seconds, meaning even a minuscule loss rate adds up over time.) Hecla is investigating a variety of collection techniques including electromagnetic collectors that can improve retrieval efficiency, and even allow maneuverability while the radiator is in operation.
If successful, this could reduce the mass of the cooling system for a future nuclear electric power space reactor by an order of magnitude. The work will vastly improve the potential of nuclear power in space and potentially expand its utility to include low-Earth orbit projects as well.
An early interest in radiation detection - at MIT
With his appointment as an assistant professor, Hecla's career has come full circle since his undergraduate days as a student at NSE.
Early on, he was especially interested in radiation detection techniques because of their use in many practical applications.
That specific interest was seeded during a formative childhood trip to New Mexico, which included a visit to a shop selling rocks and minerals. Hecla remembers being fascinated by the goods, which included uranium ore. He was hooked. Hecla researched the field and bought and built a do-it-yourself Geiger counter. "Throughout high school I was buying and repairing radiation equipment in my home. I collected high-voltage equipment, built a homemade X-ray system, and it was all downhill from there," Hecla says.
That passion for measuring radiation spilled over to MIT. One of Hecla's undergraduate research projects involved developing a prototype of a photocathode-driven X-ray unit, in collaboration with Massachusetts General Hospital. The research team he worked with formed a startup called Advanced Tomography Systems . As part of another undergraduate research opportunities program (UROP), Hecla worked with Areg Danagoulian , associate professor at NSE, on a novel approach for treaty verification.
A visit to Chernobyl
While at MIT, another formative event would cement Hecla's deep commitment to measuring radiation: a friend, Carl Willis , now a professor at the University of New Mexico, invited Hecla to travel to Chernobyl. "It was to better understand the realities of living and working in a contaminated environment," Hecla says.
The experience shook him - and he visited several times more during his undergraduate years. Since 2017, Hecla has served as scientific adviser to Clean Futures Fund , a U.S.-based nonprofit that ensures activities in the exclusion zone and at the power plant are as well supplied as they can be, providing basic essentials, personal protective equipment, and detection equipment.
"Chernobyl has a lot to teach us, both about the necessity of a dedication to safety in nuclear power and about managing the consequences of radiation release," Hecla says. "It's an enormously challenging environment where a small amount of well-informed work can have an outsized impact."
Chernobyl also provided the context for Hecla's graduate studies at the University of California at Berkeley, where he studied radiation imaging techniques. For his master's, the goal was to use a free-moving radiation detector to reconstruct a three-dimensional image that would inform workers about radiation intensity so they could be judicious about exposure.
Another area of radiation detection, to detect antineutrinos as an indicator of nuclear fission, anchored his doctoral research - Hecla's PhD dissertation was titled "Optical Diagnostics for Antineutrino Detector Media" - advised by Kai Vetter . The goal was to use the particles as an essentially unshieldable signature of reactor operation.
Guarding against the misuse of nuclear energy
As Hecla's graduate research showed, using radiation signatures is an effective way to track when nuclear energy is being misused.
Hecla's work on aerospace applications of nuclear power extends to both improving the viability of space reactors and improving our ability to monitor orbital and sub-orbital applications of nuclear energy.
His current research focuses on understanding and tracking air-breathing nuclear propulsion, which is a technique in which heat from a reactor is used for propulsion. Hecla became especially interested in the project when, in 2018, the Russian government announced that they were developing a nuclear-powered, nuclear-armed missile, the 9M730 Burevestnik, that would pose a direct security threat to Europe.
The missile was said to be powered by an air-breathing nuclear engine, enabling extreme duration flight. In 2019, a mishap with the system killed at least five scientists, and generated a plume of radionuclides that drifted across the White Sea, indirectly confirming that the Russians were serious about developing the missile.
Between 2023-25, as a Stanton Postdoctoral Fellow at MIT's Laboratory for Nuclear Security and Policy, working with R. Scott Kemp , Hecla developed techniques through which he could understand the performance envelope and flight signatures of the nuclear propulsion system in the missile. That information could be used to limit or ban use of such military systems, or contribute to new countermeasures.
Along with colleagues at MIT, Hecla is devising techniques to detect the presence of nuclear weapons by studying the gamma-induced neutral field from satellites, which can share information about the presence of fissile material. Such a system is especially relevant given the Kosmos 2553, a satellite launched by Russia in 2022 that is believed by American intelligence to contain components of a nuclear weapon.
The threat of nuclear weapons in space is immense. "Someone may find it advantageous to destroy most assets in low and medium Earth orbit if it gives them an edge during combat," Hecla says. As part of this work, researchers are looking to develop a highly sensitive compact neutron telescope to detect and locate the source of neutrons as a way to detect nuclear activity.
Most of Hecla's work, including the space thermal management projects, sits at the intersection of nuclear and the aerospace or aeronautical fields.
Hecla is delighted to be back at MIT where it all started. "We have the right combination of talent here that is strong and growing," he says. "And between world-class facilities like the MITR-II ( MIT Nuclear Research Reactor ), the PSFC ( Plasma Science Fusion Center) , the people, this is absolutely the best place for research," Hecla says.
