Isro on last-minute glitch that forced them to abort Chandrayaan-2 lift-off
Helium is used in cryogenic engines that use oxygen and hydrogen as fuel, such as the Geosynchronous Satellite Launch Vehicle (GSLV) Mark III that will carry Chandrayaan-2, in pressuring the propellant tank to keep it from collapsing and to prevent the formation of bubbles.Updated: Jul 17, 2019 13:26 IST
A second attempt to launch Chandrayaan-2 may be possible by the end of July with scientists discovering that the glitch that led to an aborted lift-off an hour before scheduled on Monday morning can be fixed without the entire launch vehicle having to be disassembled, according to people familiar with the matter.
“The fuel from the launch vehicle has already been emptied out. There was a helium leak from the propellent team. The problem has now been discovered. A nipple joint valve in the plumbing malfunctioned. This can be repaired on the launch pad and there will be no need for disassembling the launch vehicle,” an ex-scientist at the Indian Space Research Organisation (Isro), who is still involved with the project, said on condition of anonymity.
Helium is used in cryogenic engines that use oxygen and hydrogen as fuel, such as the Geosynchronous Satellite Launch Vehicle (GSLV) Mark III that will carry Chandrayaan-2, in pressuring the propellant tank to keep it from collapsing and to prevent the formation of bubbles.
Helium is the only gas that can be used as its normal boiling point is lower than that of hydrogen; any other gas would freeze, producing particles that could clog the propulsion system, a scientist said.
GSLV Mark III, India’s most powerful launch vehicle with a capacity of carrying 4-tonne satellites, derives power from the cryogenic engine upper stage that uses oxygen liquified at -183 degrees Celsius and Hydrogen at -253 degrees Celsius. The first stage of GSLV Mark III uses two solid fuel rocket boosters for lift-off and the second core stage uses two liquid fuel engines.
In 2016, a “large breach” in the helium system led to an explosion destroying Space X’s Falcon 9. A similar helium leak in 2014 was detected early, and the mission was scrapped.
The early detection in the deviation of launch vehicle parameters on Tuesday morning saved the ₹978 crore mission at the eleventh hour. “This system performed precisely in the way it was designed to and we managed to save the nearly ₹1,000 crore mission in time. We were lucky that the mission did not enter the automatic launch sequence, else all would have been lost. All things are in our control,” a senior official from Isro said on condition of anonymity after the launch was aborted.
“Once the valve is fixed, Isro will refuel and check whether there is any leak. If not, the mission can proceed,” said the scientist quoted in the first instance.
There is a launch window for Chandrayaan-2 during the new moon on July 29 and 30. After that, the next such window will open only in September.
Chandrayaan-2 will make India the fourth country after the US, Russia and China to land a spacecraft on the moon. It will also be the first mission in the world to explore the South Pole of the moon, looking for traces of water.
“If Isro pushes the launch to next month, then the inclination of the orbit will have to be changed, leading to more fuel consumption, reducing the payload capacity of the vehicle,” the scientist said.
When contacted, a second Isro official said: “This is an internal process. There will be no updates for the public as of now. We will let you know once all the procedures are completed.”