Laser-Assisted Nuclear Thermal Propulsion for Cislunar Logistics: A Monte Carlo Power-Closure Assessment

Manuscript prepared for the CEAS Space Journal (Springer), version 1.1.0, with supplementary information, title page and cover letter (docx and pdf). Revised after a pre-submission review: the performance targets are treated as hypothetical design targets; the thermochemical validation is harmonized at identical conditions; the energy buffers are stated with their units; the scope of the receiver mass and the heating of the hydrogen are discussed; the conventional tug with an optimized reactor is the primary benchmark; Sobol sensitivity, a technology-threshold map, node-phasing and independent-integration checks are added; the asteroid-deflection extension is in the Supplementary Information. Supersedes version 1.0.0. Abstract. Laser-assisted nuclear thermal propulsion (LANTP) would raise the specific impulse of a nuclear thermal tug by adding orbital laser power to the hydrogen. We take performance targets of this kind (specific impulse 1300–1500 s, thrust 50–120 kN, a 1–50 MW laser on a 100–500 MWt reactor, and an initial mass in low Earth orbit, IMLEO, 40% below that of conventional nuclear thermal propulsion, NTP) as hypothetical design targets and test them for Earth–Moon logistics with a coupled model: hydrogen thermochemistry checked against Cantera, a power chain from the wall plug to the propellant, Gaussian-beam capture, finite burns with occultation and link dropouts, tug and laser-node masses, and Monte Carlo and Sobol analyses over assumed ranges. Reaching 1300–1500 s needs a useful laser power of 2.2–3.6 times the reactor power, so a 1–50 MW laser gives at most 1,000 s, and 50–120 kN needs 0.7–1.6 GW of emitted power. Against a conventional tug whose reactor is sized for the payload, the laser-assisted tug has a median IMLEO ratio of 1.44 (5th–95th percentile 1.13–1.94); 0% of the draws are below 1 and none reaches 0.6. Receiver specific mass carries 73% of the variance. A technology-threshold map shows that a mass benefit needs a receiver below about 11 kg per MW absorbed. The laser nodes (about 18 kt) and the propellant reserve for a single laser fault remove the benefit. Results are conditional on the assumed ranges. Code and data: https://github.com/sandlerleon/lantp-cislunar-mc (archived at 10.5281/zenodo.24048703). All design inputs are assumed ranges, not measurements. A generative AI tool (Claude, Anthropic) assisted with drafting, code and figures; the author reviewed the content and takes full responsibility.