Sustained cislunar logistics operations, including recurring support of the Lunar Gateway at EML1 and EML2, impose demanding propulsion requirements, including high ΔV budgets, restart capability, and long-duration propellant storage, which conventional propulsion approaches struggle to meet efficiently at scale. This study presents a novel cislunar mission architecture based on nuclear thermal propulsion (NTP), operating at a specific impulse of 900 s with liquid hydrogen as propellant and a hydrazine Reaction Control System (RCS) for proximity and docking maneuvers. The architecture is evaluated analytically through sequential application of the Tsiolkovsky rocket equation across two mission scenarios: a direct logistics transfer to EML1 (Scenario A) and a two-burn Gateway staging transfer from EML1 to EML2 (Scenario B), using a launch mass of 9000 kg, a 5% ΔV margin, and deterministic ΔV values of 3164 m/s for LEO→EML1, 160 m/s for EML1→EML2, and 37.36 m/s for RCS operations. The proposed architecture achieves a total propellant mass below 3044 kg and a total delivered mass between 5956 kg and 6071 kg across both scenarios. These results establish NTP as a technically credible foundation for scalable and sustainable cislunar transportation, with broad implications for the development of a permanent lunar economy.

Nuclear thermal propulsion (NTP) offers a specific impulse of approximately 900 s — roughly double that of chemical rockets — yet remains constrained by peak fuel temperatures, convective heat transfer limitations in solid cores, and chamber pressures typically below 100 bar. This conceptual study proposes three modular hybrid NTP architectures that leverage established physics from adjacent domains to achieve substantial performance improvements while retaining high thrust-to-weight ratios suitable for crewed interplanetary missions. The Electrostatic-Augmented Nuclear Thermal Rocket (EANTR) adds downstream partial ionization (10–30 %) and electrostatic acceleration (10–50 kV grids) within an extended magnetic nozzle, augmenting thermal exhaust velocity without fully transitioning to low-thrust electric propulsion. The Acoustic Resonance-Enhanced Nuclear Thermal Propulsion (ARENTP) incorporates propellant-cooled acoustic drivers to generate resonant standing waves (10–100 kHz) in fuel-element channels, enhancing convective heat transfer by 2–5× and enabling higher core temperatures or reduced fuel mass. The Supercritical-Fluid Nuclear Thermal Rocket (SF-NTR) maintains the hydrogen (or H₂/CH₄) propellant supercritical throughout the flow path, eliminating phase-change instabilities, supporting chamber pressures of 300–500 bar, and exploiting heat-capacity peaks for improved cooling and expansion efficiency. Mission analyses for trans-Mars injection, mid-course correction, and Novel Hybrid Nuclear Thermal Propulsion Concepts for Enabling Affordable, Routine Human Mars Missions: The Electrostatic-Augmented Nuclear Thermal Rocket (EANTR), Acoustic Resonance-Enhanced Nuclear Thermal Propulsion (ARENTP), and Supercritical-Fluid Nuclear Thermal Rocket (SF-NTR) | Zenodo Skip to main You are using an outdated browser. Please upgrade your browser to improve your experience. Published February 28, 2026 | Version v1.0 Preprint Open Novel Hybrid Nuclear Thermal Propulsion Concepts for Enabling Affordable, Routine Human Mars Missions: The Electrostatic-Augmented Nuclear Thermal Rocket (EANTR), Acoustic Resonance-Enhanced Nuclear Thermal Propulsion (ARENTP), and Supercritical-Fluid Nuclear Thermal Rocket (SF-NTR) Authors/Creators de Beer, Riaan 1 Show affiliations 1. Independent Researcher Description Nuclear thermal propulsion (NTP) offers a specific impulse of approximately 900 s — roughly double that of chemical rockets — yet remains constrained by peak fuel temperatures, convective heat transfer limitations in solid cores, and chamber pressures typically below 100 bar. This conceptual study proposes three modular hybrid NTP architectures that leverage established physics from adjacent domains to achieve substantial performance improvements while retaining high thrust-to-weight ratios suitable for crewed interplanetary missions. The Electrostatic-Augmented Nuclear Thermal Rocket (EANTR) adds downstream partial ionization (10–30 %) and electrostatic acceleration (10–50 kV grids) within an extended magnetic nozzle, augmenting thermal exhaust velocity without fully transitioning to low-thrust electric propulsion. The Acoustic Resonance-Enhanced Nuclear Thermal Propulsion (ARENTP) incorporates propellant-cooled acoustic drivers to generate resonant standing waves (10–100 kHz) in fuel-element channels, enhancing convective heat transfer by 2–5× and enabling higher core temperatures or reduced fuel mass. The Supercritical-Fluid Nuclear Thermal Rocket (SF-NTR) maintains the hydrogen (or H₂/CH₄) propellant supercritical throughout the flow path, eliminating phase-change instabilities, supporting chamber pressures of 300–500 bar, and exploiting heat-capacity peaks for improved cooling and expansion efficiency. Mission analyses for trans-Mars injection, mid-course correction, and orbit capture (Δv ≈ 4.5–6 km/s) indicate that these concepts can reduce propellant mass fractions from ∼65 % (contemporary solid-core NTP) to 35–45 %, enabling crewed transit times of 80–120 days in single heavy-lift configurations or fully in-situ resource utilization (ISRU)-fueled return legs from Mars. Comprehensive searches of public literature, patents, and technical reports (through February 2026) reveal no prior integration of these specific mechanisms into NTP systems, thereby distinguishing them from ongoing bimodal, centrifugal, or gas-core efforts. Key engineering challenges, feasible development pathways (leveraging existing hot-hydrogen test infrastructure), and implications for cost-effective, sustainable human presence on Mars are discussed. Files Hybrid Nuclear Thermal Propulsion Concepts.pdf Files (442.6 kB) Name Size Download all Hybrid Nuclear Thermal Propulsion Concepts.pdf md5:a8f4205af1f2c798d8ea5e7cc68f3409 442.6 kB Preview Download Additional details Software Repository URL https://github.com/infinityabundance/EANTR-ARENTP-SFNTR Programming language Rust , Python Development Status Concept 53 Views 12 Downloads Show more details All versions This version Views Total views 53 53 Downloads Total downloads 12 12 Data volume Total data volume 7.1 MB 7.1 MB More info on how stats are collected.... Versions External resources Indexed in OpenAIRE Communities Keywords and subjects Keywords nuclear thermal propulsion hybrid NTP Mars propulsion specific impulse augmentation electrostatic augmentation acoustic resonance enhancement supercritical propellant in-situ resource utilization ISRU graceful degradation variable-mode propulsion affordable Mars missions routine Mars access EANTR ARENTP SF-NTR Details DOI DOI Badge DOI 10.5281/zenodo.18809245 Markdown [](https://doi.org/10.5281/zenodo.18809245) reStructuredText ..

Nuclear thermal propulsion offers significant improvements in rocket engine specific impulse over rockets employing chemical propulsion. The computer code ATHENA (Advanced Thermal Hydraulic Energy Network Analyzer) was used in a parametric analysis of fuelpipe. The fuelpipe is an annular particle bed fuel element of the reactor with radially inward flow of hydrogen through it. The outlet temperature of the hydrogen is parametrically related to key effects, including the effect of reactor power at two different pressure drops, the effect of the power coupling factor of the Annular Core Research Reactor, and the effect of hydrogen flow. Results show that the outlet temperature is linearly related to the reactor power and nonlinearly to the change in pressure drop. The linear relationship at higher temperatures is probably not valid due to dissociation of hydrogen. Once thermal properties of hydrogen become available, the ATHENA model for this study could easily be modified to test this conjecture.

The Space Exploration Initiative requires the development of nuclear thermal and nuclear electric technologies for space propulsion for future Luna and Mars missions. Sandia National Laboratories has proposed a new nuclear thermal propulsion concept that uses fission fragments to directly heat the propellant up to 1000 K or higher above the material temperatures. The concept offers significant advantages over traditional solid‐core nuclear rocket concepts because of higher propellent exit temperatures, while at the same time providing for more reliable operation due to lower structure temperatures and lower power densities. The reactor can be operated in either a steady‐state or pulsed mode. The steady‐state mode provides a high thrust and relatively high specific impulse, as compared to other nuclear thermal concepts. The pulsed mode requires an auxillary radiator for cooling, but has the possibility of achieving very high specific impulses and thrust scaleable to the radiator size. The propellant temperatures are limited only by thermal radiation and transient heat conduction back to the substrate walls.

Various propulsion systems are considered for a split-mission piloted exploration of Mars in terms of reducing total initial mass in low earth orbit (IMLEO) as well as trip time. Aerobraked nuclear thermal propulsion (NTP), multimegawatt (MMW) nuclear electric propulsion (NEP), and MMW solar electric propulsion (SEP) are discussed and compared to a baseline aerobraked chemical propulsion system. NTP offers low IMLEO, MMW NEP allows both low IMLEO and a short trip time, and both nuclear systems offer better mission characteristics than the chemical system. The MMW SEP is concluded to be less efficient in spite of a lower IMLEO because of the system's higher specific mass and nonconstant power production. It is recommended that MMW NEP and SEP systems be considered for application to Mars cargo missions. The NEP system is concluded to be the most effective propulsion configuration for piloted Mars missions and lunar base missions.

Abstract Fission power systems have demonstrated higher thermal energy density per unit mass than chemical systems. High mass specific energy density offers advantages in space thermal propulsion applications. In the 1960s, nuclear thermal propulsion (NTP) development included the ROVER/NERVA program, in which full-scale prototype reactors were tested on the ground using hydrogen as the reactor coolant and propellant. NTP systems are being revisited, with expectations of improved performance resulting from improved fuel materials, allowing propellant temperatures near 2,800 K and over 20 thermal propulsion cycles. An apparatus has been developed to test NTP fuel materials in a research reactor at temperature and in a radiation environment typical of the NTP application. This paper presents the design constraints, preliminary scoping thermal analysis, and basic thermal qualification testing for the out-of-pile experiment set apparatus, or OUTSET.

Space exploration enables humans to not only explore unknown worlds but also to satisfy the curiosity about the contents and origins of the Universe. The last and only extraterrestrial body to be explored by humans is the Moon. The next natural step is human exploration of Mars and beyond. The long trip times associated with space exploration beyond low Earth orbit pose many risks to humans such as psychological effects associated with confinement and isolation, cancer and disease associated with increased radiation dose, and deleterious effects of extended exposure to microgravity which affects a range of physiological systems such as ocular and cardiac. One approach to overcoming these challenges is limiting exposure time via high-speed transit. This requires advanced propulsion beyond conventional systems that feature high thrust and high fuel efficiency. A propulsion system that can enable such quick trip times to destinations throughout the solar system is the gas core nuclear rocket concept. The gas core nuclear rocket offers substantial advantages over chemical or electric or even solid core nuclear propulsion systems. Operating at high temperatures, the gas core nuclear rocket achieves high specific impulse and high thrust, essentially eclipsing conventional solid-core nuclear thermal rockets. Indeed the core itself is in the gaseous state and thus conventionally can operate at temperatures so high that the core itself is in the plasma state – thereby enabling the pro