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July 18, 2021 Archives

Sunday, July 18, 2021

CONTEXT: NASA Chief Scientist James Green—Searching for Life in the Solar System and Beyond

Posted at 14:11 Permalink

TRACKING WITH CLOSEUPS: Demonstrating the Photoelectric Effect

Posted at 13:47 Permalink

CONTINUITY: Douglas DC-7—Nonstop Transcontinental Travel before the Jet Age

Posted at 12:51 Permalink

CONTINUITY: Is the Apollo 11 Lunar Module Ascent Stage Still in Lunar Orbit?

After delivering its crew back to the command module in lunar orbit, the ascent stage of Apollo 11's lunar module Eagle was jettisoned and left in lunar orbit. Unlike the ascent stage of Apollo 10, which was ejected into a heliocentric orbit, or those of subsequent lunar landing missions, which were deliberately crashed into the Moon to permit analysis of the Moon's interior by seismometers deployed on the surface, Eagle performed no further maneuvers after being discarded.

The Moon's gravitational field is substantially “lumpy” and objects in orbit around the Moon are perturbed by its variations and the influence of the Earth, Sun, and other planets' gravity. It has long been assumed that Eagle’s orbit must have at some time evolved until it intersected the lunar surface, resulting in the spacecraft's crashing at some unknown location.

Now, in a brilliant piece of independent science using publicly available data and open source analysis tools, James Meador finds, in a May 2021 paper, “Long-term Orbit Stability of the Apollo 11 Eagle Lunar Module Ascent Stage”, that long-term simulation of the evolution of Eagle’s orbit suggests it is possible it may still be in orbit around the Moon. Now, numerical integration over a period of more than half a century, taking into account the imprecisely-known gravitational field of the Moon, plus unknowables such as whether venting of propellants or pressurised and cryogenic fluids from the abandoned spacecraft, may have perturbed the orbit into one leading to an impact, is an uncertain business, but how cool would it be if radar monitoring the lunar limb could discover Eagle after all these years? If it's there, it certainly deserves a visit after humans return to the Moon once again so long after the false dawn.

And then…? “That belongs in a museum. ”

Posted at 12:06 Permalink