Moon Express, a privately held company driven by a short-term goal of winning the Google Lunar X PRIZE competition, and a longer-term strategy of mining the Moon, last week revealed its MX-1 lunar lander at the closing session of Autodesk University in Las Vegas. Not a one-trick pony, the MX-1 is being designed as the first of a series of robotic spacecraft that can carry out a multitude of tasks in Earth orbit as well as in deep space.
About the size of a large coffee table, the MX-1 is a spacecraft that has the self-contained capability to reach the lunar surface from a geosynchronous transfer orbit, such as those commonly followed by communications satellites on their way to geosynchronous orbit. The delta-v required to move from a geosynchronous transfer orbit through low lunar orbit to a lunar landing is about 3.2 km/sec (7,160 mph). This requirement places rather strong conditions on the makeup and effectiveness of the lander's propulsion system.
When fully fueled and ready to launch, the MX-1 will weigh about 600 kg (1,320 lb), its small weight and dimensions making it suitable as a secondary payload, traveling for example in the wake of a new communications satellite. The result will be far smaller launch costs than if a dedicated launch vehicle were required to send the MX-1 on its journey, perhaps as small as US$6-8 million – not pocket change, but a tiny cost compared to historical numbers.
Three-quarters of the launch mass of the MX-1 will be fuel for its main rocket engine, which has been given the joint tasks of propelling the spacecraft toward the Moon, and to then achieve a soft landing on the lunar surface.
The main engine for the MX-1 is a bipropellant liquid fuel rocket designed to use high concentration hydrogen peroxide as a monopropellant, assisted by injections of kerosene when breaking out of Earth orbit. The engine will use hydrogen peroxide alone for most maneuvers, with kerosene only being used to enter the Earth-Moon transfer orbit.
This choice of fuel, or rather of multiple fuels, is quite unusual. Hydrogen peroxide (H2O2) is a water molecule with an extra oxygen molecule forced on. Best known for its use in the Bell Rocketbelts and their descendents, propellant-grade H2O2 is quite a hazardous substance.
As a monopropellant, when H2O2 comes into contact with a catalyst, it converts into a mixture of steam and oxygen at a temperature of about 600° C (1,100° F). When directed through a rocket nozzle, these decomposition products yield a rather small specific impulse of about 150 seconds, indicating a performance level midway between black powder and the composite propellants used in large-scale booster rockets.
When combined with kerosene (RP-1 fuel), the specific impulse jumps to about 300 seconds. There is currently no information on how much kerosene is in the fuel tanks of the MX-1, but presumably enough to push the MX-1 into lunar orbit. However, the descent from orbit and landing maneuvers will be carried out using H2O2 alone, a feat only practical owing to the Moon's low gravity.
One reason mentioned by Moon Express for using H2O2 as a propellant is the discovery of considerable quantities of water on the Moon, particularly near the poles which are the tentative landing site for the MX-1. Given water and electricity, the MX-1 would also have hydrogen and oxygen available. As there do exist methods of making hydrogen peroxide based on electrolysis, it appears that Moon Express is placing a sizable bet on being able to manufacture extra rocket fuel at the landing site. This is what is sometimes known in the English civil service as a courageous decision.
The MX-1 is not intended simply to serve as a lunar lander. It is the basis for a flexible spacecraft that can support multiple missions ranging from acting as a smart upper stage for existing launch systems, satellite servicing missions, serving as a space tug, returning lunar samples to Earth, and, perhaps in modified form, taking on an important role in deep space exploration.
"The MX-1 is the ‘iPhone of space’; a platform capable of supporting many apps including our core plan of exploring the Moon for resources of benefit to humanity," says Bob Richards, founder and CEO of Moon Express. "Moon Express will utilize the MX-1 in its maiden technology demonstrator flight in 2015, delivering a number of commercial and government payloads to the Moon and pursuing the $30 million Google Lunar XPRIZE."
The design of the MX-1 does show considerable ingenuity in its aggressively modular design, which seems well suited to its immediate and future tasks. We wish them well with this immensely challenging project.
Source: Moon Express, Inc.