Khrunichev Cites Overheating in Proton Upper-stage Mishap
PARIS — Overheated fuel oxidizer on the launch pad combined with an engine that ran at the higher end of the allowed temperature regime caused the Dec. 9 failure of the Russian Proton rocket’s Breeze-M upper stage during launch of the Yamal-402 commercial telecommunications satellite, according to a Russian board of inquiry report that was validated by ( ), Proton’s commercial sales arm.
The overheating caused the nitrogen tetroxide oxidizer to turn to gas in volumes that overwhelmed the engine’s oxidizer turbopump, leading to a bearing failure and the shutdown of the Breeze-M stage about four minutes earlier than planned.
The Yamal-402 satellite, owned by Gazprom Space Systems of Moscow, was left in a too-low orbit. The satellite’s manufacturer,of France and Italy, was able to raise it into its planned geostationary orbit 36,000 kilometers over the equator, but at a cost in fuel that reduced Yamal-402’s operating life to 11 years from up to 19 years.
In a Feb. 12 interview, officials with Reston, Va.-based ILS said the corrective actions to be taken following the failure will require no hardware modifications. Instead, ILS and Proton prime contractor — and ILS owner — Khrunichev State Research and Production Space Center of Moscow will impose stricter limits on the permitted temperatures under the Proton’s fairing as it awaits launch.
The corrective actions are straightforward enough for ILS and Khrunichev to have planned a late-March return to flight for Proton. As was the case following the vehicle’s August Breeze-M failure, which had different causes, the vehicle will be returning to flight with a commercial mission.
ILS said satellite fleet operator Satmex’s Satmex 8 satellite will be launched March 27. Satmex is perhaps the most anxious of ILS’s customers to get its satellite launched as it will replace the Satmex 5 satellite, which is expected to end its commercial life later this year.
Insurance underwriters covering Satmex 8 and other ILS customers will be briefed on the ILS/Khrunichev inquiry’s findings the week of Feb. 18. In the past, insurers have accepted the relatively quick returns to flight of Proton after failures without forcing ILS customers to pay substantially higher insurance premiums. The vehicle has failed three times in the past 18 months.
Whether the underwriters will be as understanding this time around is unclear. Many of them participated in the $400 million insurance coverage of theIS-27 commercial telecommunications satellite, which was destroyed in the Jan. 31 failure of a Russian-Ukrainian Sea Launch rocket.
It is not the ambient temperature at the Proton launch pad at the Baikonur Cosmodrome in Kazakhstan in December that caused the Breeze-M cryogenic fuel tanks to warm up. It was the normal heating that occurs to keep the satellite within specified temperatures.
ILS Chief Technical Officer John L. Palme said Proton’s telemetry duly recorded the temperature under the fairing. He said that while 1 or 2 degrees higher than the average prelaunch temperature, it was still within the specified limits.
“It’s only 1 or 2 degrees, but as we all know if these differences occur around freezing level, it is the difference between rain or snow,” Palme said.
Compounding the problem was that the particular Breeze-M engine used for the Dec. 9 flight operated at slightly higher temperatures than the average engine — again, within specifications.
With the turbopump now receiving a larger-than-acceptable volume of oxidizer gas, it began to show signs of stress during the third of four burns planned to carry the Yamal-402 to its prescribed transfer orbit.
A bearing in the overworked turbopump failed, and the Breeze-M engine shut down completely some four minutes earlier than specified before releasing the Yamal-402, which suffered no damage.
Palme and ILS Chief Engineer Jim Kelly said the data provided in the abundant telemetry sent by Proton leave little doubt about the sequence of events and the root cause of the problem.
“It is very, very evident from all the telemetry that the engine was operating in a way it was not designed and qualified to do,” Kelly said. ILS relied on a copy of the Russian board of inquiry report that was passed on from Khrunichev after being scrubbed of information on technologies that may not be transferred under Russian technology-export regulations.