Stranded Falcon 9 Booster in Decaying Lunar Orbit for March 4 Impact

A piece of an old Falcon 9 rocket is on a crash course with Luna, according to astronomers tracking debris in the Earth sphere.

A 7-year old booster set adrift in space years ago is headed for impact, first reported by a Bill Gray in a release from January 21st. His computations show the booster making an orbit around the moon again, eventually falling into the dark side of the moon on March 4.

Gray said his confidence in accuracy contains some variables in running the numbers: he is able to account for the gravitational effects of the Earth, Moon, Sun, and other planets, as well as the effect of the gentle push of sunlight on the mass. "I have a rough idea of how much sunlight is pushing outward on the object, gently pushing it away from the sun. This usually enables me to make predictions with a good bit of confidence. However, the actual effects of that sunlight are hard to predict perfectly. It doesn't just push outward; some of it bounces "sideways". The object is a long cylinder, spinning slowly; you can see the light from it vary as it tumbles," said Gray. 

The long, 3.6-ton rocket was a part of a 2015 test launch that did not have sufficient fuel burn to return back to ground, being left in orbit in a chaotic track ever since. The impact will be another interesting footnote of the new space era, possibly launching some debris that could help establish the composition of the moon's surface similar to a 2009 NASA launch that uncovered water there. Gray is optimistic about the impact, hoping that it could provide a show for those watching the skies. 

"I have particularly hoped for a booster to hit on the near side, in an unlit area, near the First or Last Quarter; that would presumably be visible from Earth. But we'd have to get very lucky for that... and when you think that this is the first unintended lunar impact we've had, period, the level of luck required increases," he said. 

"Better still, perhaps, would be for the folks launching these missions to think about where their boosters are going, and to leave them in orbits that will intersect the moon. I would be a big fan of this, but it does not seem to have been on the radar for either CNSA or NASA."

FMI: www.spacex.com