PSLV notches up another success

The launch of PSLV-C17 Credit:ISRO

The PSLV has added another success in it's list after than the successful launch of the GSAT-12A on-board the PSLV-C17. This was the PSLV's 19th flight and it's 15th consecutive successful launch. The satellite was launched into a sub geostationary transfer orbit.

The 53 hour countdown started at 11:48 hours (IST) on July 13, 2011. ISRO has been generous enough to provide us with videos of launch vehicle integration which happened during the months and weeks leading upto the launch.


The integration of Solid rocket boosters with first stage. Credit:ISRO




Integration of the third and fourth stages. Credit:ISRO




Integration of the satellite and heat shield. Credit:ISRO



The GSAT-12A itself is a communications satellite of the INSAT-family, a replacement for the INSAT-3B. It was launched to address the ever-growing demand for transponders. This particular satellite carries 12 C-band transponders.

The launch window for this flight opened at 16:48 hours for 20 minutes. The weather was gloomy but there was no rain leading-up to the launch. The mission director gave the go-ahead for the launch at the scheduled launch time (16:48 hours IST). During the last 15 minutes, the onboard mission computer takes over the launch control. It is also important to mention that this particular flight was the first PSLV flight with the indigenous flight computer Vikram (which was previously used on the GSLV-D3 flight).

Due to this being a launch to sub-GTO orbit, the normal flight profile of the PSLV was altered slightly to obtain the large apogee. The configuration used here was the PSLV-XL with 13.5 meter long strap on solid boosters that each carried nearly 12 tonnes of propellant instead of the standard version were they are 11.3 meters long and carry 9 tonnes of propellant. At liftoff the vehicle stood 44 meters tall and weighed about 320 tonnes.

The altered fight profile meant that the fourth stage coasted for 2 minutes 25 seconds before ignition and fired for about 9 minutes. After about 20 minutes of the flight, the satellite was inserted into a sub-Geosynchronous Transfer Orbit (sub-GTO) with a perigee of 284 km and an apogee of 21,020 km with an orbital inclination of 17.9 deg. This was almost equal to the planned 284 km perigee and 21,000 km apogee orbit.

The satellite will be placed into Geostationary orbit by firing of it's onboard thrusters during the coming weeks.

Flight Brochure: Link
Image Gallery: Link

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.

GSLV-F06 Launch Failure

The GSLV-F06 flight was unsuccessful following an explosion at around T+60 seconds.



The S139 does have a very good record flying on both the PSLV and the GSLV, so it would come somewhat as a surprise if it did cause the failure. The strap-on boosters would be another suspect having previously failed on one of the GSLV flights.

It would be too early to debate the exact cause until there some official response from ISRO into what caused the failure.

GSLV-D3 Failure Analysis Report

The GSLV-D3 Failure Analysis Report is out. Posting the report in full:

The third developmental flight of Geosynchronous Satellite Launch Vehicle (GSLV-D3) conducted on April 15, 2010 from Satish Dhawan Space Centre SHAR, Sriharikota, primarily for the flight testing of indigenously developed Cryogenic Upper Stage (CUS), could not accomplish the mission objectives. Consequently, ISRO had instituted a two-tier process to carry out an in-depth analysis of the flight performance, identify the causes of failure and recommend corrective measures. The Failure Analysis Committee comprising multi-disciplinary experts completed the analysis and its findings were further reviewed by a National Group of Eminent Experts. These reviews have brought out that: Following a smooth countdown, the lift-off took place at 1627 hrs (IST) as planned. All four liquid strap-on stages (L40), solid core stage (S139), liquid second stage (GS2) functioned normally. The vehicle performance was normal up to the burn-out of GS-2, that is, 293 seconds from lift-off. Altitude, velocity, flight path angle and acceleration profile closely followed the pre-flight predictions. All onboard real time decision-based events were as expected and as per pre-flight simulations. The navigation, guidance and control systems using indigenous onboard computer Vikram 1601 as well as the advanced telemetry system functioned flawlessly. The composite payload fairing of 4 metre diameter inducted first time in this flight, also performed as expected. Performance of all other systems like engine gimbal control systems and stage auxiliary systems was normal. The initial conditions required for the start of the indigenous Cryogenic Upper Stage (CUS) were attained as expected and the CUS start sequence got initiated as planned at 294.06 seconds from lift-off. Ignition of the CUS Main Engine and two Steering Engines have been confirmed as normal, as observed from the vehicle acceleration and different parameters of CUS measured during the flight. Vehicle acceleration was comparable with that of earlier GSLV flights up to 2.2 seconds from start of CUS. However, the thrust build up did not progress as expected due to non-availability of liquid hydrogen (LH2) supply to the thrust chamber of the Main Engine. The above failure is attributed to the anomalous stopping of Fuel Booster Turbo Pump (FBTP). The start-up of FBTP was normal. It reached a maximum speed of 34,800 rpm and continued to function as predicted after the start of CUS. However, the speed of FBTP started dipping after 0.9 seconds and it stopped within the next 0.6 seconds. Two plausible scenarios have been identified for the failure of FBTP, namely, (a) gripping at one of the seal location and seizure of rotor and (b) rupture of turbine casing caused probably due to excessive pressure rise and thermal stresses. A series of confirmatory ground tests are planned. After incorporating necessary corrective measures, the flight testing of Indigenous Cryogenic Upper Stage on GSLV is targeted within a year. In the meantime, the next two GSLVs would fly with the available Russian Cryogenic Stages.

Launch Report: D3 flight Unsuccessful

The GSLV-D3 flight that lifted-off from SDSC at 16:47 IST was unsuccessful. This led the vehicle to lose altitude and splash down into the Bay of Bengal. The exact reason for the failure is ascertained but the ISRO Chairman, Dr. K Radhakrishnan told the press that the problem could have with vernier engines of the upper stage.

The vehicle lifted-off at 16:47 IST and from here there are numerous reports of the vehicle terminating data transmission just after 505 seconds. The flight is said to have progressed normally upto the planned shut-down of S2 (2nd Stage) 293 seconds. Normally the S2 stage shut-downs at T +310 seconds at an altitude of 120 km and is jettisoned 4 seconds later at an altitude of 127 km. This is also when the cryogenic engine ignition takes place. But the parameters of the vehicle is said to have veered-out after T +293 seconds following a failure of the 2 vernier engines used to control the vehicle.

The vehicle is said to have got a velocity of 4.9 km per second as planned and the cryogenic stage ignition command was issued as planned by the on board computer. The terminal velocity (ie at the end third stage shut-down) of the GSLV is 10.2 km/sec at an altitude of 195 km.

The Chairman of ISRO told the press that, ”Indications are that the cryogenic engine got ignited”. But the vehicle started tumbling, due to loss of control, lost altitude and finally splashed down into the sea. This could have been caused by the ignition failure of the two vernier engines. These small thrusters are used for altitude control and adjustments in velocity.

The flight was the maiden one for the new Chairman of ISRO. The Chairman indicated at failure of vernier engines but he said that detailed analysis of the flight data is being carried out to find out the exact reasons for the failure and that corrective measures would be taken for the next test flight, scheduled to take place within a year.

Here is ISRO's official press release on the flight.