Lunar CubeSat: "Cislunar Explorers"

The Cislunar Explorers are a pair of streamlined, sustainable spacecraft on a mission to orbit the Moon. They act as self-propelled engineering demonstrations, proving the technology readiness of water as rocket fuel, simple optical navigation, and more. Key subsystems complement each other in a symbiotic design aimed at reducing the cost and complexity of space exploration.

The NASA Centennial Challenges program announced the results of the fourth and final Ground Tournament in the CubeQuest Challenge. The Cislunar Explorers spacecraft won first place and were selected fly as a secondary payload on the Artemis 1 mission. This will allow us to compete in the Lunar Derby and become among the first CubeSats to depart Earth orbit. Success will prove the viability of water electrolysis propulsion and interplanetary optical navigation, both of which will contribute to expanding the capabilities of the CubeSat platform.

Both spacecraft launch mated together as a “6U” sized-box that could fit in a briefcase. They hitchhike into space alongside a larger spacecraft as a secondary payload; our intended ride is NASA’s EM-1 test of the Space Launch System, on which spots are available via the CubeQuest Challenge.

The Cislunar Explorers spacecraft leverage simple physics and symbiosis between several subsystems. The concept is a single rectangular 6U structure that splits into two L-shaped spinning spacecraft with a spring loaded separation mechanism. Each Explorer has a tank of water in the bottom of the “L,” off-center from the spin axis. That water is electrolyzed, using power generated from solar panels, into a mixture of hydrogen and oxygen gas–excellent rocket propellant. The spacecraft spin helps separate the combustible gas from the inert water like a centrifuge.

That spin also gives the spacecraft angular momentum, just like a top or gyroscope. In the event of any wobbling of the spacecraft spin axis, the water in the propellant tank will slosh around and serve to passively damp away these unwanted oscillations. Therefore, the spin that is necessary for our propulsion subsystem to function turns out to be kept steady by that very same subsystem!

The water tank helps and is helped by another key item, our avionics package. Our spacecraft will navigate by taking pictures of the Sun, Moon, and Earth using and applying image recognition using their onboard computers. We will mount these and other spacecraft electronics on the faces of the propellant tank, which will serve as a heat sink for waste energy produced during the mission. This helps keep our electronics from overheating and our water from freezing. Either would cause the end of the mission.

Symbiotic subsystems greatly simplify the design and operation of the spacecraft: key aspects of the mission work for each other’s benefit instead of needing to be solved independently. Synergy reduces complexity, and a streamlined spacecraft is a safe and inexpensive spacecraft.