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NASAの月面懐中電灯が消えたが、成功の兆しもあった

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NASA 月面懐中電灯

この図は、NASA の月面上の懐中電灯を示しています。 月の南極にある表面の氷を見つけることを目的として2022年12月に打ち上げられたNASAの月懐中電灯ミッションは、小型推進システムが月周回軌道に達するのに十分な推力を生成できないため終了した。 この挫折にもかかわらず、推進システム、グリーン燃料、Sphinx フライト コンピューター、アップグレードされた Iris 無線機など、ミッションに関するいくつかの技術デモンストレーションは期待を上回り、将来のミッションに貴重な洞察をもたらしました。 クレジット: NASA

CubeSat は、氷を探すために月の南極に到達することはできませんでしたが、人類の利益のために将来のミッションを可能にするいくつかの技術目標を達成しました。

NASA’s Lunar Flashlight launched on December 11, 2022, to demonstrate several new technologies, with an ultimate goal to seek out surface ice in the permanently shadowed craters of the Moon’s South Pole. Since then, the briefcase-size satellite’s miniaturized propulsion system – the first of its kind ever flown – proved unable to generate enough thrust to get into lunar orbit, despite months of effort by the operations team. Because the CubeSat cannot complete maneuvers to stay in the Earth-Moon system, NASA has called an end to the mission.

NASA relies on technology demonstrations to fill specific knowledge gaps and to test new technologies. Used for the first time beyond Earth’s orbit, Lunar Flashlight’s propulsion system and green fuel were such demonstrations. Although the propulsion system was unable to produce the desired thrust – likely because of debris buildup in the thruster fuel lines – newly developed propulsion system components exceeded performance expectations.

Also surpassing expectations were Lunar Flashlight’s never-before-flown Sphinx flight computer – a low-power computer developed by NASA’s Jet Propulsion Laboratory in Southern California to withstand the radiation of deep space – and the spacecraft’s upgraded Iris radio. Featuring a new precision navigation capability, the radio can be used by future small spacecraft to rendezvous and land on solar system bodies.

NASA's Lunar Flashlight Illustration

This illustration shows NASA’s Lunar Flashlight, with its four solar arrays deployed, shortly after launch. The small satellite, or SmallSat, will take about three months to reach its science orbit to seek out surface water ice in the darkest craters of the Moon’s South Pole. Credit: NASA/JPL-Caltech

“Technology demonstrations are, by their nature, higher risk and high reward, and they’re essential for NASA to test and learn,” said Christopher Baker, program executive for Small Spacecraft Technology in the Space Technology Mission Directorate at NASA Headquarters in Washington. “Lunar Flashlight was highly successful from the standpoint of being a testbed for new systems that had never flown in space before. Those systems, and the lessons Lunar Flashlight taught us, will be used for future missions.”

The mission’s miniaturized four-laser reflectometer, a science instrument that had never flown before, either, also tested successfully, giving the mission’s science team confidence that the laser would have been able to detect ice if it were present at the lunar surface.

“It’s disappointing for the science team, and for the whole Lunar Flashlight team, that we won’t be able to use our laser reflectometer to make measurements at the Moon,” said Barbara Cohen, the mission’s principal investigator at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “But like all the other systems, we collected a lot of in-flight performance data on the instrument that will be incredibly valuable to future iterations of this technique.”

Propulsion System Performance Challenges

Despite the mission’s technological wins, Lunar Flashlight’s miniaturized propulsion system struggled to provide sufficient thrust to put the CubeSat on course for the planned near-rectilinear halo orbit that would have given the spacecraft weekly flybys of the Moon’s South Pole.

The team suspects that debris obstructed the fuel lines, causing the diminished and inconsistent thrust. The miniaturized propulsion system included an additively manufactured fuel feed system that likely developed the debris – such as metal powder or shavings – and obstructed fuel flow to the thrusters, limiting their performance. Although the team devised a creative method for using just one thruster to maneuver the spacecraft, Lunar Flashlight needed more consistent thrust to reach its planned orbit.

The operations team calculated a new orbit that could be reached using the spacecraft’s small amount of potential remaining thrust. The plan called for putting the CubeSat on a path that would place it in orbit around Earth rather than the Moon, with monthly flybys of the lunar South Pole. While this would have meant fewer flybys, the spacecraft would have flown closer to the surface.

With the mission running out of time to arrive at the needed orbit, the operations team tried to dislodge any debris from the fuel lines by increasing the fuel pressure well beyond the propulsion system’s designed capacity. Despite limited success, the required trajectory correction maneuvers couldn’t be completed in time.

“The student operations team at Georgia Tech, with assistance from JPL and NASA’s Marshall Space Flight Center, rose to the challenge and came up with an incredible array of inventive techniques to utilize what tiny amount of thrust Lunar Flashlight’s propulsion system could deliver,” said John Baker, Lunar Flashlight project manager at JPL. “We learned a lot and honed new methods and strategies for working with tiny spacecraft.”

After having traveled out past the Moon, Lunar Flashlight is now moving back toward Earth and will fly past our planet with a close approach of about 40,000 miles (65,000 kilometers) on May 17. The CubeSat will then continue into deep space and orbit the Sun. It continues to communicate with mission operators, and NASA is weighing options for the future of the spacecraft.

More About the Mission

Lunar Flashlight is managed for NASA by JPL, a division of Caltech in Pasadena, California. The CubeSat is operated by Georgia Tech, including graduate and undergraduate students. The Lunar Flashlight science team is led by NASA Goddard and includes team members from the University of California, Los Angeles; Johns Hopkins University Applied Physics Laboratory; and the University of Colorado.

The CubeSat’s propulsion system was developed by NASA Marshall in Huntsville, Alabama, with development and integration support from Georgia Tech. NASA’s Small Business Innovation Research program funded component development from small businesses including Plasma Processes Inc. (Rubicon) for thruster development, Flight Works for pump development, and Beehive Industries (formerly Volunteer Aerospace) for specific 3D-printed components. The Air Force Research Laboratory also contributed financially to the development of Lunar Flashlight’s propulsion system. Lunar Flashlight is funded by the Small Spacecraft Technology program based at NASA’s Ames Research Center in Silicon Valley and within NASA’s Space Technology Mission Directorate.





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