Lunar Oxygen Propellant (LUNOX) or

What Beamed Energy Propulsion can do for our exploration of Moon.

by Don Johansen

How does Lunar Oxygen Propellant (LUNOX) used for Beamed Energy Propulsion (BEP) enable reduced cost of lunar exploration over full lunar surface?

The Apollo mission emphasized lunar material return and short duration exploration with limited science investigation and experiments. The current NASA Constellation lunar program envisions extended duration of science and engineering investigation following Apollo methodology. Advanced propulsion (cryogenic replaces hypergolic) and separate launch for crew and spacecraft are departures from the Apollo scenario. Beyond, it is expected that an exploration program might emerge which is similar to the international program of Antarctic exploration.

Exploration and scientific investigation of Antarctica provides a template for future lunar activities. The major obstacle at this time is the high cost of transport to and from the lunar surface. In situ production can address many issues of survival (food and shelter) on the lunar surface and thereby lower earth-to-moon transportation costs. Oxygen is a major constituent of lunar soil and can be processed into usable monopropellant to greatly lower the cost of return to earth.

Problems of earth-based BEP launch (atmospheric attenuation, vehicle drag, high gravity and high delta V) are missing or minimal in lunar environment. Lack of fuel in non-polar locations is currently a significant problem. Polar locations may find water too expensive to use for fuel and opt to use beamed energy to heat LUNOX. Use of in situ lunar oxygen extends low-cost exploration from the polar regions to the full lunar surface. This is orders-of-magnitude increase in explorable lunar surface.

Oxygen as beamed-energy-heated monopropellant offers storage advantage compared to hydrogen but has lower exhaust velocity. At chamber temperature of 4000K, LUNOX provides 3000 m/sec (specific impulse of 300 sec ) which is comparable to chemical propellants. Hydrogen offers four times increase in exhaust velocity (I_sp = 1200 sec) at this temperature.

As beamed power at fixed thrust is proportional to exhaust velocity, the power needed at burnout is reduced by a factor of four for oxygen compared to hydrogen.

Lower lunar gravity (comparing to earth) also means lower thrust which reduces power requirements. At lunar gravity = one-sixth earth gravity the indicated power reduction is 4 ´ 6 = 24 for lunar beamed energy using LUNOX vs hydrogen heated by earth-based beamed energy. This reduction is even better considering drag and atmospheric attenuation penalties for earth-based beamed-energy launches.

For lunar surface launch to LLO (low lunar orbit) the loaded propellant mass is slightly less than burnout mass. Due to simplicity of BEP thruster, the payload mass ratio is high and the loaded LUNOX mass is roughly equal to payload mass. Lunar Shuttle Vehicle (LSV), carrying earth return payload to Apollo-type command module, is thereby possible.

Avoiding the need to carry Lunar Excursion Module for orbit to surface transport (and back) reduces the launch mass by a factor of two. LLO refuel provided by the LSV reduces launch mass by a factor of three.

To summarize: Given lunar infrastructure supporting Antarctica-style exploration (fixed-base, year round deployment) with in situ resource development, LUNOX is a plentiful by-product which can be used for Beamed Energy Propulsion (BEP). BEP is favored over chemical heating due to high cost of transporting/producing fuel at the lunar site. Source power now is in 100 KW to 2 MW range approaching 1 mm wavelength, already capable of lunar point-to-point experiment or small payload to low lunar orbit.

Please, see the detailed publication of Dr. Johansen on the subject at:

Donald G. Johansen, Lunar Oxygen as Monopropellant, in Proceedings of the Fifth International Symposium on Beamed Energy Propulsion, Kailua-Kona, Hawaii, 12 - 15 November 2007, edited by Andrew V. Pakhomov, AIP Conference Proceedings Vol. 997, American Institute of Physics, Melville, New York, 2008, pp. 507 - 519.

About the author: Dr. Don Johansen participated in early design phase of Galaxy satellite and Hubble Space Telescope. Recently developed physical models and simulations of anti-missile defense systems. Dr. Johansen has BSEE, MSEE (minor in math/physics) from Oregon State University and Aero-Astro Ph.D. from Stanford University. He is member of AIBEP since 2008.

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