Wednesday, April 20, 2011

Shroud design to blame for GSLV failure ?

A picture showing the cryogenic stage shroud (of the ICUS)

First of all, congratulations to ISRO and the scientific community on the successful launch of PSLV-C16 carrying Resourcesat-2. ISRO has really put a lot of work into reviewing every aspect of the launch vehicles after the GSLV-F-06 failure. And the PSLV has again stood up to it's name as the the workhorse of ISRO.

Coming to GSLV-F06 flight. The failure analysis team had previously identified the cause of the snapping of connectors. Deformation in the cryogenic stage shroud was to blame. So as to what caused the deformation of the shroud, there was a difference of opinion between the Russians, who built the stage and the shroud, and ISRO.

The Russian side put the blame on the bigger payload fairing, which caused addition aerodynamic forces that led to excessive stress the shroud causing it to give way.

According to ISRO, the cause for deformation was not the bigger payload fairing but a design flaw in shroud (blaming Khrunichev, the manufacturer of stage).

This disagreement was causing the delay in the submission of the Failure Report. But, today's TOI has an article saying that the issue has been resolved. ISRO seems to have gone through with it's assessment on the cause for shroud deformation.

Link to article: Design flaw behind GSLV crash

"There is a need for correction in the design of the shroud. The shroud at the bottom of the cryogenic stage did not fulfill all service conditions during the flight, as a result of which the connectors linked to the shroud snapped. The connectors were linked to the shroud."

"The shroud was influenced by the pressure distribution that built up in the flight at around 46 seconds and was distorted. It is the distortion of the shroud that led to pulling out of the connectors, which shouldn't have happened before the separation of the stage. But since it did, the vehicle (GSLV) lost altitude and control as a signal to the strap-ons from the computer did not come, owing to the snapping of the connectors," Nair explained.

The space scientist said two key recommendations have been made for future course of action — either make the shroud stronger/tougher or do away with it altogether. "The second is a possibility which we need to work out. If that is possible, all other parameters of the GSLV are fine. A successful flight of the GSLV is not an impossibility."


The Failure report has been submitted to the Department of Space and we can expect the full report to be out in a week's time.

3 comments:

  1. Are you talking about D3 or F06 mission? ISRO identified the problem with shroud on first GSLV development flight. As I said earlier http://indianspaceweb.blogspot.com/2010/12/gslv-f06-launch-failure.html?showComment=1297058115893#c6616670890638403018), Modifying / Increasing 3rd stage engine beyond its capable limit is the primary reason for the mission failure.

    1.) Increased amount of fuel to burn in Russian supplied cryogenic engine. (only in F06 mission)
    2.) Increased Heat Shield (payload fairing) size (both in D3 and F06 missions)
    3.) Payload size is increased a little bit.

    "The space scientist said two key recommendations have been made for future course of action — either make the shroud stronger/tougher or do away with it altogether. "The second is a possibility which we need to work out. If that is possible, all other parameters of the GSLV are fine. A successful flight of the GSLV is not an impossibility."

    - This issue may effect MK3 flight test. What do you think?

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  2. Sorry, I was indeed referring to F06 flight.

    I don't think this issue will have any effect on the Mk-III program or even the Mk-2 program. But, ISRO will retest the strength of the shroud on the indigenous cryogenic stage too to make sure it doesn't carry a similar problem. AFAIK the ICUS is stronger structurally and has been designed to carry 15 tons of fuel from the start, so there should be any significant issues there.

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