In the early hours of July 14, 2019, at precisely 6:51 am, the customary 20-hour
countdown for the launch of the Chandrayaan-2 began, raising the hopes of Indian
spacecraft reaching the moon and soft landing on it. Until now only Russia, USA and
China have landed on the Moon, and the efforts by Israel, Japan, and European space
agency have met with failure.
With the start of the countdown, the clock in the mission control room commenced ticking
backwards, signalling the scheduled launch at 2:51 am on July 15, 2019. The control panel
in the launch control room came alive and displayed the vitals of the launch vehicle. One
by one, various steps of the launch sequence were initiated. The last significant step in the
launch sequence was to fill up the fuel tanks of the third stage cryogenic rocket with liquid
hydrogen and liquid oxygen.
T-156 minutes, 12:15 AM on 15th July, Indian Space Research Organisation (ISRO)
announced filling of Liquid oxygen. Images of the launch pad, the nozzle of the GSLV, the
launch tower splashed on the screens on the wall. At T-77 minutes, 1:34 AM, ISRO
tweeted filling of Liquid Hydrogen was also complete and asked the followers stay tuned
for more updates. Anticipated vapours from the third stage could be seen in the screens.
The clock kept ticking. The excitement was in the air. Anticipation thick.
Boom! Display screens went blank. The clock stopped ticking, stopping at T-56:24. ISRO
officials quietly rushed away from the room. Power outage? Perplexed media guessed
something was amiss.
A few minutes later, B R Guruprasad, Public Relations Executive of ISRO walked towards
the podium and read out an official statement in a grim voice “A technical snag was
observed in launch vehicle system at T-56 minute. As a measure of abundant precaution
Chandrayaan2 launch has been called off for today. The revised launch date will be
announced later.” Silence fell. Gloom spread.
K.Sivan, Chairperson of ISRO had claimed earlier, that the launch window was open for
tomorrow if weather played a spoilsport today. Nevertheless, as the ISRO subsequently
has made clear that the next launch date will be announced only after ten days, the glitch,
it is clear is considerable, requiring perhaps an overhaul of the whole launch vehicle.
Incidentally, the Chandrayaan-2 launch was to be the third flight for the GSLV Mk III,
popularly nicknamed ‘Bahubali’ of ISRO.
GSLV Mk III launchers
ISRO developed powerful Geosynchronous Satellite Launch Vehicle (GSLV) Mk III
launcher to place 4-ton class payload in the Geostationary orbit. The three-stage launch
vehicle uses solid fuel for first stage, liquid fuel for the second stage and cryogenic rocket
engine in its third stage.
Lacing adequate technology, during the late 1980s, ISRO obtained the cryogenic engines
and know-how from the Glavcosmos a Soviet space agency. After the fall of the Soviet
Union, buckling under the pressure of the USA, Russia backed out from transferring the
duel use cryogenic rocket technology, forcing ISRO to develop its own indigenous cryogenic engine. After years of strenuous research and development, ISRO came up with
its own CE-7.5 cryogenic rocket engine fitted in all the GSLV Mk III launchers. The ISRO
established the Propulsion Complex (IPRC), located at Mahendragiri of Tamil Nadu, for
research, development and production of the cryogenic engines.
After the successful development of cryogenic rocket engine, the first experimental flight of
GSLV Mk III took place on December 18, 2014, and the successful developmental flights
GSLV Mk III D1 and GSLV Mk III D2n took place on June 05, 2017 and November 14,
2018, respectively. Chandrayaan 2 mission was the first operational mission and third flight
for the GSLV Mk III.
What could have gone wrong
While the solid stage and the second stage of the GSLV rockets are filled well before the
rocket is assembled in the launch pad, the cryogenic propellent kept in sub-zero
temperatures are filled about an hour before the launch. From the reports emanating from
various sources, we know that as the fuel was being injected into the cryogenic fuel tank a
snag was noticed by an alert ISRO scientist and the mission control aborted the launch.
The fault at the fuelling of the third stage implies that the ISRO engineers would have to
first drain the loaded fuel before they can approach the rocket. The ISRO in the next few
days would dismount the assembly and investigate all the components before they attempt
a launch again. ISRO has announced that it would take at least ten days before the source
of the snag is detected and that the revised launch date would be announced later. For a
mission to Moon, a suitable launch window with the desired orientation of Earth, Sun and
Moon is imperative. Hence the next launch cannot be undertaken before a month. The
detection of the snag, removal of the fault, reassembly, suitable launch window all makes
postpone the mission even by many months.
Not the first time
The very first developmental flight of the GSLV D1 was scheduled on March 28, 2001, 3.47 pm. The countdown for the lift-off proceeded smoothly till about 1 second before liftoff when the automatic launch process system found that the four liquid propellant strap-on rockets have not developed the required thrust. The countdown was immediately stopped and the launch aborted. The GSLV was taken once again to the drawing table, and the fault was removed. After many improvements, the GSLV Mk III D1 was finally launched in 2017 successfully.
How long we have to wait for the launch of the Chandrayaan 2? Only the fault report from the ISRO will tell.
(T V Venkateswaran is science communicator with Vigyan Prasar, New Delhi.)