Trouble with a new cryogenic engine is delaying India's plans to debut an updated all-Indian version of its Geosynchronous Satellite Launch Vehicle, the most powerful rocket in the country's inventory.

The GSLV's new cryogenic third stage undergoes testing in 2007. Credit: ISRO

Officials with the Indian Space Research Organization tell Spaceflight Now the delay is to give engineers time to complete a thorough review of a new indigenous third stage fueled by cryogenic liquid oxygen and liquid hydrogen chilled to about -400 degrees Fahrenheit.

The long-delayed stage include a new engine that will fire for up to 12 minutes during a typical GSLV mission. Engineers finished flight acceptance ground testing of the engine in December 2008, according to ISRO.

But the debut of the cryogenic stage, already postponed several years, may not occur until this spring or summer.

ISRO officials confirm they are reviewing the rocket's performance and test results, but they are not discussing what triggered the analysis.

Senior officials, quoted in Indian news outlets, have said they expect to decide on the next GSLV launch in January, but there has been no announcement so far.

Called GSLV Mk.II, the new version of the medium-lift launcher is slated to deploy the 4,800-pound GSAT 4 satellite in geosynchronous orbit about 22,300 miles above Earth.

The launch is codenamed GSLV D3 in the Indian launch manifest.

GSAT 4 will carry an experimental Ka-band communications payload, a navigation instrument to augment GPS signals and an Israeli ultraviolet imager with three telescopes to survey the sky for astronomers.

The GSLV has flown five times since 2001 with a Russian hydrogen-fueled third stage originally built for the Proton rocket. The Russian third stage is blamed for two minor mishaps in 2001 and 2007 that resulted in an underperformance of the rocket, leaving its payloads in slightly different orbits than planned.

File photo of a GSLV launch. Credit: ISRO

India has been developing the new upper stage for nearly 14 years to decrease the reliance on Russia and make the GSLV booster an all-Indian rocket, an ISRO spokesperson said.

The cryogenic engine is rated for more than 16,000 pounds of thrust in vacuum. An ISRO statement in 2008 said the the new upper stage can hoist about 4,850 pounds to a standard elliptical geosynchronous transfer orbit, a capacity very close to the estimated launch mass of GSAT 4.

In the December 2008 press release, ISRO predicted the GSLV Mk.II would make its first flight by the middle of 2009.

The GSLV is designed to launch Indian weather and communications satellites to geosynchronous orbit. The three-stage rocket also includes a solid-fueled first stage motor, four liquid-fueled strap-on boosters and a hypergolic second stage that consumes hydrazine.

India is also developing a heavy-lift model of the rocket called the GSLV Mk.III, which would consist of two massive solid rocket boosters, a restartable second stage and a more efficient third stage.

On Sunday, Indian engineers successfully tested the three-segment solid rocket booster. The 72-foot-long booster, which produces up to 1.1 million pounds of thrust, is the third most powerful solid-fueled motor in the world, after the boosters used on the space shuttle and the Ariane 5 launcher.