Burn-through Blamed in China Long March Mishap

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PARIS — China’s Long March 3A series of rockets is expected to return to flight before the end of this year following the conclusion of a state-run board of inquiry into the Aug. 31 failure of the vehicle’s upper stage, the vehicle’s operator said Nov. 19.

The investigation into the underperformance of one of two upper-stage engines during the flight, which placed Indonesia’s Palapa-D satellite into a useless orbit, concluded that failure was caused by a burn-through of the engine’s gas generator.

The board of inquiry into the vehicle’s first failure in 13 years concluded that the most likely cause of the burn-through was foreign matter or humidity-caused icing in the engine’s liquid-hydrogen injectors. To prevent a recurrence of the problem, the liquid hydrogen gas-feed system on future rockets will be fitted with a filter to prevent the passage of ice or other foreign objects.

In addition, the gas generator in the third-stage engine’s liquid hydrogen cavity will be purged before launch to prevent ice buildup.

The Long March 3 rocket family includes the 3A, 3B and 3C vehicles, which differ only in the number of fueled strap-on boosters.

Long March launch services provider China Great Wall Industry Corp. of Beijing said in a Nov. 19 statement that the board of inquiry has reproduced the failure on the ground and concluded that it “was solely caused by the underperformance” of one of the two identical third-stage engines.

The board was made up of officials from the China Academy of Launch Vehicle Technology (CALT), which is the rocket’s prime contractor, and from the Academy of Aerospace Propulsion Technology, which builds the Long March 3’s upper-stage engines. The China Aerospace Science and Technology Corp. (CASC) established a special committee to review the inquiry board’s findings.

The affected engine was found to have delivered 38 percent less thrust than it should have for 43 percent of its total working time, China Great Wall said in the Nov. 19 statement.

China Great Wall said the new upper-stage engine filter has been qualified for flight and will be flight-tested before this year using otherwise identical engines.

Responding to Space News inquiries, China Great Wall General Manager Fu Zhiheng on Nov. 19 said the demonstration launch will feature the Long March 3C, fitted with two strap-on boosters. The mission is intended to carry a domestic Chinese satellite into geostationary-transfer orbit, the destination of most telecommunications satellites.

Meanwhile, Palapa-D prime contractor ThalesAlenia Space of France and Italy announced Nov. 16 that the satellite, which was guided into its intended orbit by a series of firings of its on-board engines, has completed its in-orbit acceptance review and is ready for use at 113 degrees east longitude by its owner, PT IndosatTbk of Jakarta.

The satellite’s in-orbit service life is now estimated at more than 10.5 years, instead of 15 to16 years if it had not used fuel to correct the defective orbit, ThalesAlenia Space said.