Lunar oxygen, beamed energy propulsion and exploration of the moon.
Our exploration of the moon requires new ideas of space transportation. This article is about Lunar Oxygen Propellant (LUNOX) and how Beamed Energy Propulsion based on LUNOX will allow us to explore full lunar surface.
The original Apollo mission focused on getting lunar rock samples, with very limited scientific program and tests performed right there. The new Constellation mission, to be conducted by NASA, anticipates longer-term scientific experiments on the moon. As a new step comparing to Apollo mission, there will be use of advanced propulsion techniques, thus cryogenic engines will replace hypergolic. In addition, separate launches of spacecraft and crew modules will be substantial departures from Apollo mission. In general, Constellation exploration program will be similar to an Antarctic expedition.
The experience of our exploration of Antarctica will serve as a role model for development of our new frontier: the moon. In this case the major limitation comes from the cost of transportation to and from our natural space satellite. Moving certain life-supporting facilities to the moon will be the key step in cutting the transportation costs. Oxygen is one of the most abundant elements of lunar soil. It can be converted into propellant for earthbound transport.
Comparing to earth, beamed-propelled launches will be much easier to conduct from lunar surface, because there will be no air drag, no turbulence, no atmospheric scattering, no need for high delta V. This, of course, follows from the absence of atmosphere on the moon and small lunar gravity (six times smaller than ours). Hydrogen, the most efficient propellant and available everywhere on Earth can be developed only from water-rich poles of the moon. As a result, our exploration of the moon will be limited mostly to those regions. Unlike hydrogen, LUNOX can be mined everywhere and by means of beamed-energy propulsion provide earthbound transport. Therefore, LUNOX allows expansion of explored areas of the moon to non-polar regions!
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 (Isp = 1200 sec) at this temperature.
At four times reduced exhaust velocity oxygen propellant will consume four times less beamed power in order to generate the same thrust as hydrogen propellant.
Comparing hydrogen BEP on earth with oxygen BEP on moon, oxygen power requirements will reduce by 4 times! Indeed, taking into account difference in gravity we will get factor of 4 x 6 = 24. It will be even better if we recall that BEP on moon has no losses due to atmosphere (in view of its absence).
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.
Use of LSV makes unnecessary lunar landing (and take-off) of the Lunar Excursion Module. This will reduce initial launch mass two times for lunar mission from Earth. If LSV could provide on-orbit refueling to Earth return Command Module, then the launch mass could be reduced threefold.
In conclusion, we can state that development of Antarctica-like research stations over all lunar surfaces can be facilitated by use of LUNOX as a monopropellant for Beamed-Energy Propulsion (BEP). Comparing to chemical propulsion, BEP provides unique launch and de-orbit capabilities on the moon. Using existing power-beaming sources in the power range of 0.1 - 2.0 MW and wavelength near 1 millimeter, initial experiments can be conducted for small payload launches at the very start of lunar renewed exploration.