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Did Excessive Weight Doom ISRO’s GSLV Rocket?

By Doug Messier
Parabolic Arc
December 27, 2010
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Some interesting speculation on what caused the Christmas Day failure of India’s GSLV rocket:

Instability introduced by excessive payload weight was most likely responsible for the failure of an Indian rocket’s launch on Christmas day, an expert in the field and former scientist of the Indian Space Research Organization (ISRO) says.

The scientist, with over two decades of experience with rocket motors, who did not want to be quoted has disputed ISRO’s reasoning that the Rs.3 billion ($66 million) mission that was meant to launch an advanced communications satellite was brought down because some cables snapped during the ascent of the Geostationary Satellite Launch Vehicle (GSLV).

ISRO chairman K. Radhakrishnan said at a post-launch press conference Dec 25 that cables carrying control signals from the on-board computer to the first stage got snapped and, as the uncontrolled vehicle started deviating from its flight path, it had to be destroyed.

Radhakrishnan, however, did not say why the cables snapped. ISRO’s routine post-launch press release gave no details but only made a cryptic announcement that the “launch of GSLV-F06/GSAT-5P mission (was) not successful”.

This is an interesting theory because weight is a definite issue in space launches. Earlier this month, a Russian Proton rocket sent three navigational satellites to the bottom of the Pacific because the fourth stage was loaded with too much fuel, causing the first three stages to under perform. (Proton returned to flight on Sunday, putting a European communications satellite into orbit.)

Weight issues also reportedly factored in to ISRO’s previous GSLV launch in April. ISRO removed the Tauvex astronomical satellite as a secondary payload aboard the rocket. ISRO Chairman K Radhakrishnan said that the decision was based on scientific merit alone; the satellite wouldn’t perform as well in a geosynchronous orbit as it would in a lower orbit.

Officials from the Indo-Israeli team that built the satellite disputed the claim, saying they would be perfectly happy with the results from GEO. They told PTI that the decision related to GSLV’s payload limitations.

The Israeli official said the real reason for postponing the Tauvex launch has to do with GSLV boosters which are not powerful enough to carry additional weight. This month’s GSLV carries GSAT-4 experimental communication satellite, weighing 2200 kg. According to the official, the 80-kg Tauvex was removed after its integration with GSAT-4 because of the “weight problem.”

“We are ticked off because actually GSLV booster is not powerful enough (as GSLV already will carry its optimum capability with GSAT-4). It’s a problem with GSLV booster,” he said.

In the end, it was a fortuitous decision. The GSLV rocket fell into the Bay of Bengal after the Indian-built cryogenic third stage failed to ignite, sending the GSAT-4 communications satellite to the bottom of the Bay of Bengal.

GSLV’s second failure this year (and fourth in seven attempts) leaves ISRO in a challenging situation. The space agency has pinned its hopes on the rocket for making it a major player in the lucrative communications satellite launch market. Until the rocket is reliable, the country won’t be able to meet its own launch needs, much less attract any international business. It will continue to be dependent on foreign rockets for its launch needs, which is a blow to its goal of independent space access.

GSLV also is crucial to the 2013-14 launch of Chandrayaan-II, a joint Indo-Russian project to send an orbiter and a rover to the moon. A more powerful version of the booster is being designed to carry India’s human spacecraft into orbit, which is planned for around 2016.

One crucial problem involves GSLV’s cryogenic third stage. India purchased seven of these stages from Russia; it has one left. ISRO’s first effort to launch a satellite using a domestically-produced cryogenic third stage failed in April because of a problem with the turbo pump. ISRO will try again in 2011.

The space agency could purchase additional third stages from Russia. Or it could more resources into perfecting its own cryogenic engine. Either option has financial consequences for a space agency that is undertaking bold new initiatives to catapult it to the ranks of the major space powers.