Reasons ISRO called off Chandryaan-2 Launch

Launch rehearsal of GSLVMkIII-M1 / Chandrayaan2 mission has been completed, and performance is normal

Reasons ISRO called off Chandryaan-2 Launch
Image Courtesy- ISRO

Reasons ISRO called off Chandryaan-2 Launch

Chandrayaan-2, an ISRO mission was about to launch on July 15 but due to a technical snag, was cancelled 56 minutes before the scheduled take-off. 

The possible reason for the cancellation 

According to a tweet from ISRO, a technical snag was observed in launch vehicle system one hour before the launch, and as a measure of abundant precaution, Chandrayaan2 launch was called off. ISRO tweet didn't elaborate further. 

According to two retired officials of ISRO, the reason was non-building of sufficient pressure in the helium tanks in the 'Bahubali' rocket. There should be proper pressure in the liquid fuel tanks so that there is a continuous flow of fuel to the combustion chamber. A drop in pressure was detected after helium was filled into the tank. The pressure drop indicated a leak in the fuel tank.  

Finally, the team pinpointed the leak in the GSLV-MKIII cryogenic engine from a 'nipple joint' of the helium gas bottle which supplies pressure to the fuel and oxidizer.

This leak was bringing down the pressure by four bars per minute. The helium gas bottle having a capacity of 34 litres was to be pressured up to 350 bars before regulating the output to 50 bars.

Oxidizer tank stores liquid oxygen at minus 183 degree Celsius, and if the joint was closed at such a low temperature, the result would be micro shrinkage of the joint. This condition further requires insulation or shifting of the joint away from the coldest point. 

This fault could also have resulted in the rocket spinning out of control.  

During a ground test, a similar oxygen leakage was detected in the cryogenic engine on June 22. Former ISRO chief K Madhavan Nair said, "A similar leak took place ahead of Chandrayaan-1 mission too, but it was rectified, and the mission was a success." 

"These Glitches were not uncommon, and a catastrophe was avoided as the anomaly was detected in time", he adds further.

Next Launch date

ISRO wants to try the launching again on July 21-22. These are the earliest dates which are suitable for launch as it will get a chance to navigate the lunar craft to the Moon's orbit. If this chance is missed, the next possible window will open up only in September. 

There is an optimal window for every launch and July 15 had the longest window of 10 minutes to achieve desired results. But now we are left with a window of at least one minute every day this month. 
"Chandrayaan-2 launch is now rescheduled on July 22, 2019, at 2.43 pm, from the second Launchpad at the spaceport in Sriharikota". 

According to a senior scientist of ISRO, nothing in the initial approach is changing. ISRO will take 22 days to insert Chandrayaan-2 into the lunar orbit because they will need 17 days around Earth for five orbit raising manoeuvres, and then five days for the lunar craft to travel close to Moon. 

"There may be a slight change in strategy, but it won't affect the actual day of landing," said a senior scientist associated with the mission.  In the previous plan, the spacecraft was to go around in 100Km X 100 Km orbit for 28 days before separation, and now it will go around for 21 days. Hence the total number of days of the mission is now 47 instead of 54. 

The second lunar mission of ISRO is worth Rs 978 crore. Its succession will make India the fourth country to land a rover on the Moon. Online registration to witness the launch live from viewer's gallery at Satish Dhawan Space Centre, Sriharikota has started from July 19, 2019.   

Watch Video: Chandrayaan-2 Mission- Know All About GSLV MK-III Rocket