Objective
The Lunar Lander Demonstrator Project was undertaken to begin development of the landing system that will be required to deliver the International Lunar Observatory (ILO) to the surface of the Moon. The soft landing will be a very challenging aspect of the ILO mission, and building the landing system may take more time and resources than any other ILO hardware system. Therefore, it is important to begin this work as soon as possible.
SpaceDev’s hybrid propulsion technology would present a low-cost, rapid-development solution as compared to other potential lander propulsion technologies. The project aimed to demonstrate that hybrid propulsion can be adapted for a Lunar Lander, and particularly that applied throttling of the hybrid rocket motors can achieve take-off, hover, and landing. Toward this end, the main objective was to design, build, and test a prototype lander vehicle using hybrid motors.
Also included in the Lunar Lander Demonstrator project, was the delivery of a new 1/6th scale model of the full ILO spacecraft, updated to reflect the hybrid propulsion landing system, and a new concept for the astronomy and communication payload.
Method
The lander prototype vehicle was designed to accomplish not only the demonstration of applied throttling, but also to serve as a platform that could be readily enhanced in later development phases to incorporate more advanced functionality. The vehicle is propelled by four 98 mm rocket motors of a type that SpaceDev has used extensively in past work. The fuel is HTPB (synthetic rubber), and the oxidizer is nitrous oxide (N2O). The four motors share a single oxidizer tank, and are throttled together via a ball valve. The valve is actuated by a servo motor, which is driven by a wireless radio controller, allowing remote control by a human operator.
The vehicle test apparatus included two parallel guide cables strung vertically from top to bottom of a five-story structure. The cables ran through low-friction tubes attached to the vehicle, constraining its motion to only the vertical degree of freedom.
Results
On 2 November, 2007, the lander prototype vehicle was successfully flight tested. The motors were ignited and throttled up by radio control, causing the vehicle to ascend to ~35 feet in altitude. The throttling was further adjusted to bring the vehicle down to ~25 feet, hover there for a few seconds, and then descend to the ground for a soft landing. This was the inauguration of the first-ever hybrid rocket propelled lander vehicle.
Also, the new ILO model was delivered to International Lunar Observatory Association headquarters in Kamuela, Hawaii in time for the ILO Founders Meeting on 4-8 November 2007.
Conclusion
The Lunar Lander Demonstrator Project showed that hybrid propulsion is a viable option for the landing system needed by the ILO mission. Furthermore, the low-cost and rapid development and testing of the prototype vehicle are representative of the benefits to be conferred on the full lander development, by employing SpaceDev’s hybrid technology and responsive engineering practices. The prototype vehicle stands ready for further flight testing, and enhancement to achieve automatic control of altitude, attitude, and three dimensional position.