Eleni Mowery, MIT NSE <etmowery@mit.edu>
Several MIT students, Prof. Shirvan, and staff scientist Nesrin Cetiner attended the ANS Nuclear and Emerging Technologies for Space (NETS) conference last week, hosted by NASA’s Marshall Space Flight Center in Huntsville, AL. NETS has been held yearly since 2013, and this year hosted several hundred attendees from government, academia, and industry to discuss space nuclear propulsion and power.
The overall attitude at the conference reflected both the funding uncertainty and drive to establish a presence on the Moon and Mars established by new administration. NASA administrator nominee Jared Isaacman’s speech to Congress, in which he highlighted the need to prioritize the “practical application of nuclear propulsion” to further space exploration was frequently quoted. Probably the biggest themes of both the plenaries and technical sessions were:
- Nuclear power is essential to establishing any sort of significant presence on the Moon or Mars.
- Dr. Bhavya Lal gave a great talk on this (including the quote in the title!) in one of the Monday technical sessions. 60kW of power could be considered as a bare minimum for establishing a lunar outpost—a power output infeasible with RTGs, which produce 100s of W, or solar. She also mentioned that a regolith processing plant would require at least 400kW. She ended her talk with: “Technology is not the bottleneck. Resolve is”, a great reminder that nuclear in space is nothing new. The US tested fission power in space in sixty years ago with SNAP-10A.
- It is true that technological development is required to bring FSP to the scale required to make large space colonies viable, and much of this was discussed in detail at NETS, with lander mass capacity, power transmission (cables are heavy), and low-mass shielding (effective photon shielding is even heavier) being some of the most critical concerns.
- As a note, FSP shielding and power transmissions were both heavily discussed at NETS, including both a novel concept proposed by DARPA to use a fungus with melanin to grow shielding in-situ, and laser-based power transmission from the reactor to lunar bases.
- Dr. Dale Thomas gave a talk in the same session about the potential for FSP to be used not only stationary power plants on the Moon and Mars, but as power systems in long-range rovers. He emphasized the potential of FSP to remove really any limitations imposed by a lack of power on the research and exploration capabilities of space colonists. This applies to surface and space travel, as well as long-range data transmission, which is exceptionally difficult with only Watts of power (RTG-powered space probes often have transmission capabilities on the order of hundreds of bits/s).
- To make anything SNP-related a reality, we need to get out of “analysis paralysis” and start testing (both on the ground and in space) ASAP
- Outside of materials testing, SNP efforts have been almost entirely computational for the past several decades. While several facilities are either operational, or under construction for NTP fuel testing in the presence of hydrogen flows, several speakers in both plenaries and technical sessions were adamant that this was not enough to truly make progress: we need to start large-scale ground testing efforts, and build up to launches and in-space tests. Several comparisons were drawn between SpaceX’s iterative testing and rapid prototyping and the recent precedent set by the space nuclear community. Given the additional safety and regulatory requirements imposed by nuclear, it’s impossible to adopt a similar approach, but the general consensus was that we needed to find a realistic middle ground to make real progress.
- From the Monday plenary: “Slow doesn’t mean safe” -Dr. Kurt Polzin
- NASA, working with Analytical Mechanics Associates presented on their efforts to come up with ground test CONOPS, utilizing a facility concept that captures and filters NTP exhaust before releasing it to the atmosphere. Several other ground test facility designs have been brought up at previous NETS conferences, including exhaust capture in a borehole, but this seems to be the leading concept.
- Several speakers brought up the challenges imposed by the relatively de-centralized organizational structure of past NEP and NTP efforts. Roger Lenard, a former manager of Project Timberwind, emphasized the need for a simple organizational structure, with few “levels” between those leading the project and those doing the bulk of the technical work. The need for a single decision-maker was also discussed as means of keeping SNP projects on-time and on-budget.
- Outside of materials testing, SNP efforts have been almost entirely computational for the past several decades. While several facilities are either operational, or under construction for NTP fuel testing in the presence of hydrogen flows, several speakers in both plenaries and technical sessions were adamant that this was not enough to truly make progress: we need to start large-scale ground testing efforts, and build up to launches and in-space tests. Several comparisons were drawn between SpaceX’s iterative testing and rapid prototyping and the recent precedent set by the space nuclear community. Given the additional safety and regulatory requirements imposed by nuclear, it’s impossible to adopt a similar approach, but the general consensus was that we needed to find a realistic middle ground to make real progress.
- The United States space presence required to meet national security needs is only possible with SNP
- The national security benefits of SNP were a much more central focus of this year’s NETS than the previous. Both the maneuverability and high, continuous power availability offered by SNP enable a more significant, constant US space presence. As China and Russia pursue space nuclear technology, it’s critical that the US does the same to maintain its leadership in the field.
- A regulatory framework for launching space reactors exists, but a precedent has yet to be set for actually using it
- Susan Voss (GNNA) presented a technical talk on how an agency might use the existing regulatory framework (primarily NSPM-200 and SPD-6) to obtain project, and eventually launch approval for a non-LEU-fueled space reactor. While most recent SNP concepts have utilized HALEU fuel, it is anticipated that the mass savings from an HEU-fueled reactors may make them the only viable option for certain missions. Should that be the case, the regulatory framework exists such that approval is still possible.
Outside of these main themes, numerous talks were given on developments in SNP modeling techniques, advanced NTP concepts, the merits of bi-modal NEP/NTP systems, mission analysis, RTGs, power conversion and management, and RTGs (including their commercial development!).
MIT’s presence at the conference was significant:
- Prof. Shirvan gave an invited talk during the Tuesday opening plenary on MIT’s growing experimental capability for SNP materials testing with the MITR, using both the 3GV6 position in the graphite reflector to conduct materials fuel tests at temperatures up to 3000K in the presence of both high-pressure hydrogen and neutron flux, and the M3 facility, which would have the capability to test an assembled NTP core in the presence of neutron flux and hydrogen.
- Patrick Riley (AeroAstro) gave a lightning talk on the development of the MITR facility for NTP-relevant testing: Design Activities of In-Situ Hydrogen Loops at MIT Reactor
- Taylor Hampson (NSE) gave a lightning talk on his work developing transient modeling capability for the CNTR in the same session: Progress Toward Transient System Modeling of the Centrifugal Nuclear Thermal Rocket
- Haeseong Kim (NSE) presented Ensemble Kalman Smoothing for Estimating Unknown Heat Source in a Transient Thermal System in the NTP Modeling II technical session
- Eleni Mowery (NSE) presented NTP Transient Reactor Modeling and Uncertainty Propagation in the NTP Modeling I technical session
Overall, NETS 2025 provided valuable insight into the state of SNP, and enforced the need to begin testing and deploying these technologies as soon as reasonably achievable: SNP is essential for achieving our space exploration goals.
