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The 273W-hr battery pack for the rover was assembled this week from parts designed and created in-house, save for the cells procured from hybrid car battery maker A123.
This week the final parts came together for the rover's battery pack. A robot arm machined sleeve end pieces and inter-cell connectors that will accommodate thermal expansion and contraction in order to maintain electrical contact. The photo above shows end units being machined by a robot arm with a router (visible at the top center).
Beating the boiling temperatures of the lunar day requires both good insulation to reject exterior radiation and an internal system to wick heat away from the electrically powered components that generate heat inside the robot.
The team is progressing on the new technologies to be incorporated in the third prototype, fabricating composite parts and putting components through deep-freeze tests, as shown in this new overview video.
A reporter who visited CMU's Planetary Robotics Lab this week learned about the chief technical challenge of robotic lunar exploration: the heat. Roaming the Moon during the entire two-week daylight stretch is a tough job anywhere near the equator; solar radiation from above and heat radiating from the soil roasts a rover at 224 degrees Fahrenheit. Her story gives good insight into how Astrobotic and CMU have attacked the thermal challenge:
March 18, 2010 - by Battery pack gets teeth
The two composite sides of the rover's battery pack will interlock, using teeth on the upper portion to latch into openings in the base. This will clamp the lithium ion cells from A123 into position to provide the 273 W-hr capacity the rover will use when it passes through shadow (during flight to the Moon or on the surface) or when it needs a supplement to the power from its solar panels. The composite battery pack parts created earlier were this week robotically shaped to create the interlock structure.
Astrobotic Technology today announced that it has vastly increased the amount of payload that it can deliver to the Moon for researchers and marketers, as part of its maiden expedition in 2012 to win the Google Lunar X Prize. The company will be able to carry 240 pounds (109 kg) to the lunar surface for space agency technologists, academic researchers and marketers. The company previously had offered only 12 pounds of payload to third parties.
The rover will operate with a 273 W-hr battery pack to provide peak power as well as power when the rover's solar array is oriented away from the Sun. The pack is comprised of A123 lithium ion cells, which will be attached to one of the interior I-beams anchoring the radiator to the chassis. After designing and machining molds, the team laid up carbon composite materials over the molds this week to test production of the battery pack holder. In the photos, the cells are about the diameter of a U.S. quarter.
The third prototype rover from the Astrobotic Technology team recently gained a mock camera and antenna head, making it nearly complete and ready for high-end photography. Yesterday it was posed in front of a green screen so that it can later be combined via Photoshop in combination with actual Apollo surface imagery and a rendering of the new design for the Astrobotic spacecraft / lander.
The overriding technical challenge of operating a rover near the Moon's equator is the intense, prolonged heat produced by solar radiation and the hot regolith over which the rover travels. All powered equipment inside the robot generates its own heat as well, which must be routed to the radiator for release into space. In the photo below, the team has a key composite part sealed in vacuum to achieve better bonding of the layers. This part, the motor strap, connects the heat-generating 28v brushless motor to other high-conductivity composite straps leading up to the radiator.


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