MOSCOW (Reuters) - A senior Russian space official said delays in U.S. shuttle launches to the International Space Station (ISS) meant extra work for Russian rocket crews without any financial compensation, RIA news agency reported.
Russia and the United States are the main contributors to the 16-nation $100 billion ISS project, but Russia has borne the brunt of sending crews and cargo there since the U.S. Space Shuttle Columbia disintegrated in 2003, killing seven astronauts.
"We are most concerned by the unpredictability of shuttle launches," RIA quoted Russian mission control flight coordinator Valdimir Solovyov as saying.
The Endeavour shuttle blasted off earlier this month after repeated delays. U.S. space agency NASA said it would hold off launching any more space shuttles until it better understands a problem with the craft's insulation.
Solovyov said the uncertainty about the U.S. launch dates meant Russian rocket staff have had to re-calculate ballistic parameters of flights by the Progress spacecraft, an automated Russian cargo vehicles used for the ISS.
"This is a big strain on the staff which is not financially compensated," he said.
Delays in shuttle launches are often caused by concerns over foam insulation shedding from the fuel tank, which caused the 2003 accident.
NASA plans seven more shuttle launches to complete construction of the International Space Station. Its next flight is due to launch on August 18.
Writing by Oleg Shchedrov; Editing by Ingrid Melander