Somewhere between 5 and 6am on Monday morning (Sydney time), Russia’s ill-fated Fobos-Grunt space probe disintegrated on re-entry into the Earth’s atmosphere, most likely over the southern Pacific Ocean off the coast of Chile (a summary of information about the Fobos-Grunt re-entry can be found on the Planetary Society blog . This was the third re-entry of a large defunct spacecraft since last September (the other two being NASA’s UARs and the German ROSAT), all of which attracted considerable media attention due to their size and potential to cause serious property damage or injury if their debris impacted in a populated area.
The danger from space debris to any individual is actually quite low, since a re-entering satellite is more likely to disintegrate over the oceans than over the land, and large tracts of the Earth’s land masses are very sparsely inhabited. In fact, dead satellites, spent rocket stages and other items of space debris regularly re-enter and burn up without creating any hazard, although fragments of space debris large enough to survive re-entry and reach the ground are not uncommon, with a handful of finds reported every year. These pieces of space junk are often found in remote areas or washed up on beaches after impact in the sea and can be quite perplexing for their discoverers. The Powerhouse receives a couple of enquiries every year from people who think they may have found a piece of space debris, or are just not sure what the strange piece of burnt material or slagged metal they have discovered might be. I recall one enquiry from a person who thought they had found a piece of space junk in the bush-but it turned out to be a dumped chunk of catalytic converter from a car engine!
In its collection, the museum holds a piece of the Skylab space station, which re-entered over the Indian Ocean and Western Australia in 1979. I’ve written about this artefact and the unusual story of its discovery in a previous post. Another piece of space debris is currently in display in the Space exhibition, one of two fragments that the museum acquired as a donation from the finder in 1972. This partly-melted metal sphere is one of three similar objects that were found on Dobikin merino stud, near Bellata in northern NSW, in 1972. Two spheres were found in late September of that year, with the third being discovered in mid-October. At two of the impact sites, scorched and burned grass testified that the spheres were extremely hot when they landed.
In the 1960s and early 70s there were several finds of space debris in Australia. A report on the Bellata spheres from the Weapons Research Establishment (which is part of the documentation provided to the museum by the donor, Dobikin stud manager Mr. J. T. Vickery), lists seven ‘space objects’ that had been found and reported between 1963 and 1973. This is perhaps not surprising as Australia’s landmass covers a wide horizontal swath of the Earth’s surface. All these items were spherical pressure vessels, their shape better suited aerodynamically to survive the stresses of re-entry, and showed varying degrees of melting and other re-entry damage. They would have originally contained gases or cryogenic liquids.
When the first ‘space ball’ was found on Boullia Station in far western NSW in 1963, media speculation as to its origins ranged from evidence for an advanced ancient lost civilisation in Australia, to debris from a damaged UFO and “Boullia Ball” became a nickname for this type of spherical object found in Australia and New Zealand (some were found across the Tasman in 1972). However, investigations of the Boullia Ball and later space debris finds by the Weapons Research Establishment (WRE), Australia’s defence science agency and forerunner of today’s Defence Science and Technology Organisation (DSTO), demonstrated that they were of definite terrestrial origin, mostly from US launch vehicles.
The first two “Bellata Balls” were sent to the WRE for examination and it was established, on the basis of the type of weld used in their construction, and lettering on one ball in the Cyrillic alphabet, that the pressure vessels had originated in the USSR. In the Cold War environment of the time, the Embassy of the USSR in Canberra declined the WRE’s invitation to inspect the balls and confirm their origin, but there is little doubt about the identification. After examination, the WRE forwarded the two balls to the museum in 1973, in accord with Dobikin manager Mr. Vickery’s wish to donate them to the Museum of Applied Arts and Sciences. The third ball discovered remained in Mr. Vickery’s possession.
The two Bellata balls donated to the museum are made of a titanium/vanadium/aluminium alloy, a relatively light but strong metal. The sphere on display in the Space exhibition is the most complete of the two, although it was partially melted away and shows a jagged rim slagged with congealed metal. The body and interior of the ball are spattered with other blobs of metal slag, but it is otherwise reasonably intact. The other sphere was burned through in two places, so the WRE decided to cut it into pieces for examination and analysis: only a segment of the original now remains, stenciled with lab markings.
Finds of space debris, tangible items that have been in space and thus are imbued with the mystique of space exploration (however mundane their actual role) continue to fascinate the public and the media. They are also important reminders of an issue that is assuming increasing significance-the dangers to operational satellites from the remnants of old satellites littering the most useful orbits. This is a topic that I’ll address in a future blog post.