Follow-Up on Phobos-Grunt

Following up on a previous story about the failed Russian space probe, Phobos-Grunt, all hope of reviving the craft has been eliminated. Phobos-Grunt is expected to fall back to Earth by the end of this month. The only real questions remaining are when, where, and what might survive re-entry.


Phobos-Grunt / Image Credit: ESA

It is not uncommon for spacecraft to re-enter Earth’s atmosphere, even uncontrolled (which to a degree, they all are). Disintegration upon re-entry is one of the space industry’s most popular disposal methods for decommissioned and defunct satellites and spacecraft. However, they generally aren’t carrying the amount of fuel that Phobos-Grunt has on board. Most of its 13 tons of weight is fuel — hydrazine and nitrogen tetroxide stored in aluminium tanks. Since fuel tanks are generally specifically designed to withstand extreme pressure and heat, they often survive re-entry; however, the Phobos-Grunt tanks were constructed out of aluminium, which is not only cheaper, but has a lower melting temperature than other common materials. Aside from the fuel, there is also a small amount — less than 10 micrograms — of radioactive Cobalt-57, but such a small amount does not pose any significant problems.

According to Holger Krag, deputy head of the European Space Agency’s Space Debris Office, at the European Space Operations Center in Darmstadt, Germany, the chances of anyone seeing the re-entry, let alone be impacted by any of the debris from Phobos-Grunt, is very low.  With more than 70% of our planet covered in water,  odds are that any debris surviving re-entry will end up in an ocean.

“Relax,” Krag said. “The likelihood of somebody being hit is enormously low. It is way smaller than to be struck by lightning. If you have a thunderstorm above your city you would also not worry too much.”

To sort of sum it all up, Phobos-Grunt will soon be toast. If you’re very lucky, you might see a spectacular light show. It will probably not land on your head.

Though, there were some positive aspects to come from the failure. For example, the re-entry is a new target for the Inter-Agency Space Debris Coordination Committee, which is “an international governmental forum for the worldwide coordination of activities related to the issues of man-made and natural debris in space”.  The more debris we add to Earth orbit, the more important it is to be able to track and deal with the potentially-devastating material; so any “practice” that Phobos-Grunt will provide would be useful.

Additionally, the failure of Phobos-Grunt provided an opportunity for various nations and agencies, as well as professionals and amateurs, to work together on trying to revive the craft, track its orbit, and now chart its re-entry. Information was shared between all of the interested parties and there was much collaboration and cooperation; all of which is important if we are to have a global recognition of the importance of space exploration and the global initiative to work together to continue exploring.

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