Moon Mission Tackles Burning Days and Freezing Nights
Japan's future SELENE-2 mission will deploy a lander and rover along with scientific instruments protected by insulated covers.
CREDIT: JAXA/Kazunori Ogawa
Keeping experiments alive can prove tricky on the harsh surface of the moon, where temperatures rise and fall by hundreds of degrees over the long lunar days and nights. Japanese scientists, planning for an unmanned lunar landing, have come up with a cone-shaped insulator that could safeguard their experiments by harnessing the stable temperature of the lunar regolith soil.
Such a "lunar survival module" would represent a possible science savior for the SELENE-2 lunar landing mission being proposed by the Japan Aerospace Exploration Agency (JAXA). That mission's geophysical experiments aimed at studying the moon's interior would have to withstand temperatures that reach 212 degrees Fahrenheit (100 degrees Celsius) during the lunar day and plunge to as low as -328 F (-200 C) at night.
"In a severe temperature environment, our goal is to maintain the operational temperature of the batteries in the lunar survival module," said Kazunori Ogawa, a JAXA scientist at the Institute of Space and Astronautical Science in Sagamihara.
The lightweight, reflective insulator has a cone shape with a flattened top to help the underlying regolith hold onto heat in the daylight. It could also keep scientific devices warm during lunar nights lasting two Earth weeks, a time when solar panels prove useless and devices must rely upon batteries protected against the temperature extremes on the lunar surface.
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Early results from heat-modeling tests regarding the insulator were presented by Ogawa at the International Academy of Astronautics' ninth Low-Cost Planetary Missions Conference, held in Laurel, Md., last month. He and his colleagues also ran real-life vacuum chamber tests with a simulated lunar surface for comparison.
"The temperature difference was held to approximately 40 degrees C [72 F] in the model," Ogawa said. "There was no major difference in the lunar survival module's survivability."
The insulator as currently designed measures 31.5 inches (80 cm) in diameter and stands 20.5 inches (52 cm) tall. Its multiple layers of insulation aim to protect possible mission instruments such as a seismometer, magnetometer, heat flow meter and radio astronomy device. A heat radiator and an antenna for communicating with other devices sit on top.
One extra challenge comes from the determination of JAXA researchers to avoid using nuclear radioisotope batteries for space missions. Such nuclear batteries could have acted as an extra heat source to keep science instruments from becoming too cold during the lunar nights.
That makes the lunar survival module even more important for protecting the regular batteries that would power SELENE-2 mission instruments.
"The primary battery life is three or six months with very low power," Ogawa told InnovationNewsDaily. "Because the solar panels can't generate energy during night, we also have secondary batteries."
For now, more work is needed to figure out how to best deploy the expandable lunar survival module, which resembles a shiny foil cube when packed. SELENE-2 would have a rover along with its main lunar lander, but such a moon rover could struggle to carry a 66-pound (30 kilograms) device and its insulator to the different deployment spots.
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