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24 December 2011

What was that piece of space junk that fell in Namibia?

Image: This 30 kg titanium pressurant tank, which survived the reentry of a Delta 2 rocket second stage, looks very similar to the metal sphere found in Namibia.

The coolest thing about working at NASA’s Goddard Space Flight Center is that you are surrounded by people you can ask questions like, “Hey, what was that metal ball sphere that fell out of outer space into a lake in Namibia?

One such individual is my friend Scott Hull, who is an orbital debris engineer at Goddard. He helps scientists and engineers comply with NASA regulations regarding space debris, including how to minimize the volume of it in orbit and reducing the chance to nil that a chunk of it will bonk somebody on the head someday. (That’s never happened, by the way…)

I asked Scott about that mysterious sphere in Namibia, reported on and, among other places. He things the object in question looks like a propulsion tank — a tank that held fuel for rocket thrusters on a spacecraft. He says it’s “probably titanium, since it has no discernible rust or burn-through spots. Tanks like this survive reentry relatively frequently.”

Indeed, that is why NASA engineers have begun to develop “demisable” propellant tanks for satellites and spacecraft, which burn up on reentry. Think of demisable rocket fuel tanks as like “biodegradable” plastic of aerospace engineering. When you are done with them, they despose of themselves.

“If this technology can be adapted for other uses, we may see fewer of these tanks surviving reentry,” Hull emailed me. “Of course, the tanks that are already on-orbit will still be falling for decades, so there will always be some.”

He pointed out that the tank found in Namibia looks very similar to the third example on this NASA web site.

Why didn’t the tank burn up? One possibility is that it’s wrapped with graphite epoxy or glass fibers. That provides some resistance to heat, presumably.

There you have it, straight from the Orbital Debris Engineer’s mouth. If you want to learn more about space debris and Scott’s work, see past coverage in Geeked On Goddard  herehere, and here.

OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.