NASA Space Debris Chief Minimizes Phobos-Grunt Threat

Artist’s rendition of the Phobos-Grunt spacecraft, now in decaying Earth orbit. (Credits: stuff.co.nz)

The ill-fated Russian space probe Phobos-Grunt has been stranded in its parking orbit around the Earth since its launch in early November, and in spite of efforts by ground controllers with the support of the European Space Agency and NASA, the fate of the spacecraft has remained uncertain. Concerns have been raised that the spacecraft may present hazards both in surviving debris and the large quantity of propellant that remains on-board.

Phobos-Grunt not the same as USA-193

Nicholas Johnson, chief scientist for orbital space debris at Johnson Space Center in Houston, Texas appeared December 5th on the “The Space Show”, an internet and radio program hosted by Dr. David Livingston, which focuses on space-related activates and issues.  When asked by Dr. Livingston about the situation of USA-193 and Phobos Grunt, Mr. Johnson noted that USA-193 possessed a titanium hydrazine tank, which had the potential to survive reentry and spill its contents.  Mr. Johnson differentiated Phobos-Grunt with USA-193 in that the Russian Federal Space Agency has said that the fuel tanks on Phobos-Grunt are made of aluminum.  According to Mr. Johnson, aluminum has a lower melting point than titanium and that significantly reduces the chances of the propellant reaching the surface of the Earth.

Little concern about falling space debris

The issue of hydrazine aside, Mr.  Johnson also noted that people should not lose sleep over debris from Phobos-Grunt since the Earth is three-fourths water and the chances favor any surviving debris falling into it.  Large objects falling from orbit is not an uncommon occurrence, and typically there is one catalogued object that falls to Earth every day.  Mr. Johnson also reported that since the beginning of the Space Age, there has been no report of anybody being harmed or being hit by reentering space debris.

Lottie Williams holding the debris that hit her. (Credits: Tulsa World).

Contrary to Mr. Johnson’s assertion, there is one reported incident involving a person being hit by a piece of space debris.  In January 1997, Lottie Williams witnessed a fireball in the night sky while walking in the park with friends in Tulsa, Oklahoma.  Thirty minutes after witnessing what she thought was a meteor, Ms. Williams was struck on the shoulder by a metal fragment comparable in weight to an empty soda can.  Ms. Williams subsequently discovered through the National Weather Service that what she witnessed was the reentry of a Delta II rocket body.  She then took the fragment to the University of Tulsa where it was identified as the type of material NASA used to insulate fuel tanks.

Questions about Yinghou-1

Another uncertainty surrounds the Yinghou-1 orbiter, which was built by the People’s Republic of China (PRC) and is mated to Phobos-Grunt. There is little technical data publicly disclosed concerning this spacecraft and seemingly little willingness by the PRC to volunteer any. It is unknown whether the spacecraft contains any potentially hazardous or radioactive materials that might survive reentry and potentially impact land. The question is: in light of the impending reentry of Phobos Grunt, will the PRC disclose technical details surrounding it spacecraft to clarify the uncertainty and allay concerns?  When asked by a caller whether there has been communication with the People’s Republic of China about the technical details of  Yinghou-1 and any potential hazards aboard, Mr. Johnson stated that he had no knowledge about technical details of the orbiter and that questions surrounding the orbiter should be directed to Chinese authorities or the Russian authorities.

With the  reentry of Phobos Grunt determined to be sometime in early to mid-January it is uncertain whether further scrutiny surrounding the technical details of both spacecraft will be addressed.  The one certainty is that until reentry occurs, questions about the impact of its reentry will remain.