Indian engineers plan to return the country's largest rocket, the Geosynchronous Satellite Launch Vehicle, to its assembly building for checks and repairs after the launcher's second stage sprung a fuel leak during a countdown Monday.

Credit: ISRO
 
Officials called off the launch about an hour and 15 minutes before liftoff, which was scheduled for 1120 GMT (7:20 a.m. EDT) from the Satish Dhawan Space Center at Sriharikota Island on India's east coast.

Indian Space Research Organization managers said engineers observed the leak in the hydrazine fuel system on the GSLV's second stage during the pre-launch pressurization phase on the vehicle about two hours before the scheduled liftoff.

"The propellants are being drained from the cryogenic stage, liquid second stage and the four liquid strap-ons of GSLV-D5," ISRO said in a statement. "The vehicle will be moved back to the vehicle assembly building for further actions."

Officials said a new launch date will be announced after a detailed assessment, but the time required for a rollback to the vehicle assembly building, tests and repairs, and the return of the GSLV to the launch pad would indicate a delay of at least a week.

When it launches, the GSLV will haul the GSAT 14 communications satellite to orbit to bolster India's Ku-band and C-band broadcasting services.

The 161-foot-tall rocket was supposed to take off for its first mission since 2010, when back-to-back failures grounded the GSLV and prompted Indian officials to redesign the launcher's hydrogen-fueled third stage.

One of the top objectives of the mission, known as GSLV-D5, is to demonstrate the third stage in flight. The Indian-built cryogenic upper stage replaces a Russian engine used on the GSLV's early missions, but its first test flight in April 2010 ended in failure when the Indian cryogenic engine shut down less than a second after ignition, dooming the launch.

Another GSLV launch in December 2010 disintegrated in a fireball less than a minute after liftoff, when cables between the launcher's computer and strap-on boosters inadvertently disconnected in flight, causing the GSLV to lose control.

The GSLV is India's largest satellite launcher, capable of carrying larger payloads than India's Polar Satellite Launch Vehicle, which has amassed 23 straight successes.

But the GSLV has a worse record. ISRO has declared four failures in the GSLV's seven launches since 2001.

The success of the all-Indian GSLV, known as the GSLV Mk.2, will give India an independent route to space for its communications satellites and planned interplanetary probes. India currently launches its largest communications payloads on foreign rockets, such as Europe's Ariane 5.

The GSLV Mk.2 configuration can loft payloads weighing more than 5,000 pounds to geosynchronous transfer orbit, the drop-off point for most communications satellites.

An upgraded version of the GSLV, known as the GSLV Mk.3, is under development to launch 9,000-pound communications satellites.