Princeton’s alumni magazine recently profiled Red Whittaker and team in an article featuring Princetonians in the Google Lunar X PRIZE competition.
Fly Me To The Moon
Kenneth Chang, Princeton Alumni Weekly
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By repeatedly taking small scoops, the rover experiences less push-back from the Moon.
The design review for Astrobitc’s Excavator rover was conducted with Robert Mueller from NASA’s Kennedy Space Center. The rover will prospect and recover resources from the Moon. The review analyzed the bucket-wheel prototype (left) designed to reduce the reactionary forces of digging felt by the rover.
The bucket-wheel’s actuator (below) is raised and lowered through the legs of the rover, which are made to carry 115kg of regolith, or lunar soil. Harmonic drives are used for higher gear ratios, higher torque, and higher resolution. A force/toque sensor is used to monitor the loads on the bucket-wheel to ensure that it does not break on a rock or large chunk of ice.
The force/torque sensor monitors inputs from the bucket-wheel’s operation.
Landing at a specific location on the moon requires orbiting around the moon over that spot. One of our landing options is the South pole, which would necessitate a polar orbit. The first step in acquiring a desired orbit is to determine the lander’s current orbit.
Orbits are defined by six parameters, which can be determined by taking pictures of the lunar surface. In fact, only three images of the lunar surface taken from the lander need to be analyzed. The application of Keppler’s laws with the time and position data is enough to determine the lander’s current orbit.
The key insight into determining orbits from known points is Keppler’s second law: An object in orbit sweeps over the same amount of area per unit time.
As the lander travels from the Earth to the Moon (also known as cruise stage), the gravitational effects of both the Moon and the Earth affect the motion of the lander. To determine the lander’s orbit and location during cruise stage a series of osculating or reference orbits are calculated assuming only two bodies are involved. Because the true orbit is a three-body system, the true or perturbed orbit deviates from the osculating orbits. After a point, a new osculating orbit is calculated using new position and velocity estimates. This process repeats so that a series of orbits assuming only two bodies are present represent the single, three-body true orbit.
A series of approximate orbits are used to calculate the true orbit of the lander during cruise stage.
This video shows a simulated traverse of computer generated lunar terrain by a rover. Team members Heather Jones and Kevin Peterson created the terrain model and simulation. The lunar terrain will aid development and testing of navigation and obstacle detection software.
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Settlement of the Moon requires access to resources, especially water for life support and the creation of propellant for spacecraft. In this video, NASA-Ames scientist Rick Elphic describes the polar volatiles sensed by orbital and impact probes, and how scientists are still searching for a consensus explanation of their origin and distribution. One theory is that a giant polar ice cap existed two billion years ago, and may still be there under several meters of mixed dirt and ice.
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Creating robots to explore and utilize the Moon requires attention to the reduced gravity, which is one-sixth that of Earth. The lower weight means robots require less power than on Earth to travel from place to place, but it also reduces the traction that machines get in the loose lunar soil. This video shows an initial component test for the Scalable Gravity Offload rig that Astrobotic is developing under a NASA contract.
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