Where India reaches for the stars: Inside ISRO’s Sriharikota Centre
It was 6 am, and our SUV rushed at breakneck speed to the remote, spindle-shaped island of Sriharikota, around 20 kms from Sullurpeta town in Nellore district, Andhra Pradesh. On both sides stretched the Pulicat lake, which at places is no more than shallow pools of entrapped sea water this summer.
Pulicat is the second largest brackish water lake in India, after the Chilika in Odisha. We zipped past long-beaked pelicans, storks, cranes, kingfishers and other native and migratory birds as they crowd these orangey waters, swallowing their pick of fish. The breeze rising from the lake was strong and gushes against the windscreen. It made a powerful whizzing hum, and I wondered if it would be similar to what the rocket igniter would sound like in a few hours.
Sriharikota is India’s primary orbital launch site, with features like a good launch azimuth corridor, nearness to the equator and large uninhabited area as a safety zone. The facility consists of two launch pads for spacecraft. SHAR will also be the main base for the Indian human spaceflight program, for which a third launchpad will be built.
On launch day, Wednesday, the Polar Satellite Launch Vehicle (PSLV) C34 took off from the second launch pad. This was ISRO’s biggest launch ever at the Satish Dhawan Space Centre (SDSC) at Sriharikota Range (SHAR), where we witnessed the PSLV C34 fly to inject 20 satellites into a single sun synchronous orbit, at a height of about 505 km. Three of the satellites were Indian — one’s a Cartosat-2 satellite for earth observation, used for urban, rural, coastal land use, water distribution and other such applications; the other two were developed by Indian universities — while the rest are commercial satellites from US, Canada, Germany and Indonesia. ISRO has a commercial arm, Antrix Corporation Ltd, that launches foreign satellites into space. According to reports quoting the prime minister’s office, 28 foreign satellites launched on the PSLV between 2013 and 2015 and generated around $101 million in commercial launch fees. Several countries use ISRO’s services because its space missions are conducted at costs that are several times lower than that of other space agencies. Wednesdays’ launch cemented India’s place as a forerunner in global space programs.
According to ISRO, the PSLV is one of world’s most reliable launch vehicles, and its XL version has made the world’s major rocket powers appreciate the working being done in the organisation. It will be taking its 36th trip to space; it has been in service for over 20 years and has been used for the Chandrayaan-1, Mars Orbiter Mission, Space Capsule Recovery Experiment, and Indian Regional Navigation Satellite System (IRNSS). It has launched over 40 foreign satellites for 19 countries. In 2008, it created a record for the most number of satellites placed in orbit in one launch by launching 10 satellites into various Low Earth Orbits (the current record is by the Russian DNEPR rocket launching 37 satellites in 2014). Given its unfailing service and flexibility towards customisation, it is known as ‘ISRO’s workhorse’ and has the capability of injecting 1750 kg of payload (satellites) into the 600 km sun synchronous polar orbit.
Our SUV continued to rush as my host was in a hurry. At the main entrance of SDSC, the maroon wall announcing the name of this ISRO centre gleamed. The 48-hour countdown to Wednesday’s mission began at 9.25 am on Monday, June 20. The previous day, officials conducted a Mission Readiness Review to inspect all the processes, explain what would be expected from each team member and department, and clarify the general flow of work. Before a launch, every team is expected to be vigilant in both meeting its own targets and collaborating with others on the larger mission.
Everywhere you looked, the whole area was dotted with uniformed men moving about on two-wheelers and in jeeps. The security and safety measures here were beefed up several times ever since the launch countdown. There was a crowd in front of the Keepakah centre employee canteen. Many of the staff also brought along a guest or two for the historic occasion. Employees from the afternoon and night shifts had to roll in for special launch duties in the morning.
There was, of course, a launch day special breakfast menu: idly, vada, upma, pongal, coconut and tamarind chutneys, sweets and coffee, all in unlimited supply. There was an exuberance in the air, a feeling of festivity along with the kind of nervousness that you experience inside an exam hall.
The wonder of the PSLV
The PSLV has four parts, each with its own set of motors, fuels and propellants. The lowest section (PS1) includes the core of the vehicle while the fourth (PS4) holds all the satellites that are to be injected in the orbit. There are six strap-on boosters containing 12.2 tonnes of solid propellant to augment the engines, four of which are at ground level. When the core is ignited, the propellant starts burning radially and these four grounded boosters are ignited along with the core to provide the massive thrust that is required for the giant vehicle to break its gravitational pull, and rise, gaining enormous velocity at every stage.
The solid propellants are made in-house at ISRO’s SHAR premises, while the 42 tonnes of liquid propellant for PS2 has to be procured from third party industrial collaborators. According to N Narayanamoorthy, an electronics and communications engineer associated with the PSLV’s development right from its formative years, special permission had to be obtained from the government in 1982 for this unique configuration of solid and liquid propellants. At some point, the scientists realised that increasing PS2 fuel from 33 to 37.5 tonnes was needed to increase its payload capability and carry heavier satellites to their relevant orbits.
Today, the PSLV is available in three configurations — the generic vehicle with six strap-ons, which is the earlier edition of PSLV (which will be discontinued soon), the core-alone version (without strap-ons), and the XL version with extended strap-ons. Other parts of the launch vehicle are manufactured separately at a Bangalore campus named after Vikram Sarabhai (VSCC) and then transported to SHAR for testing and launching.
After each part of the vehicle is tested, it is integrated and assembled. An umbilical tower connects to the integrated vehicle at different stages through wires and pipes, filling it with fuels and gases, charging its batteries, and coordinating other processes. The day before the launch, the fuel tanks get filled with propellant.
Beginning five hours before launch, GPS radiosonic balloons were released every hour into the atmosphere. These balloons send data to track parameters like wind speed and direction. An hour before launch, this data was programmed into the launch vehicle system to be able to harness the wind to its advantage. “Just as you avoid stepping on the puddles on the street after it has rained, the vehicle is programmed to avoid opposing forces,” explained one official on condition of anonymity.
Marine and air traffic commands gave their clearance an hour before, clearing the region of all other air and water vehicles. Next, the propellant, fuel and control tanks are topped up 30 minutes before launch to account for any liquid evaporation and ensure steady pressure on the propellants. “Imagine when the rocket lifts up and moves at such a high speed, everything inside it is supposed to move around. This is not acceptable in case of the propellants because air blocks will disrupt the free flow of propellants to the engines. To prevent this, and to ensure that steady pressures on the propellants are maintained, helium gas at a very high pressure of around 375 bars is bled into the fuel tanks,” said the official.
In these last 30 minutes, voices from the mission control room started pouring in through speakers to announce mission-readiness updates. The auditorium from where we were watching also started receiving live commentary, explaining many of the small and big aspects of the launch.
About 20 minutes before launch, the spacecraft was switched on using its internal power. Ten minutes to go, and the whole system moved to the Automatic Launch Signals (ALS) phase, which meant the reins were handed over to the hands of computers that receive and examine data from all parts of the PSLV, looking out for last minute glitches. If there is a leakage or a slowdown during any step, this is the stage at which it must be detected, and these computers have the power to decide to stop the launch if needed.
A senior employee told me on condition of anonymity that things have indeed gone wrong in the past before a launch; he told me about a situation in which a propellant leakage was identified in a GLSV vehicle hours before the launch. But cool-headed scientists followed protocols and safety norms to fix the leak, and the launch took place after all.
The roll control engine is the first to ignite just 3 seconds before the launch. Once the computers check if this has happened on schedule, it is the turn for the core and the four strap-on boosters to ignite at minute zero. Smoke thrusts down the rocket’s tail and, after all the anticipation, the quake of burning fuel comes like a relief. The thrust formed by the fuel at this stage lifts the vehicle along with its precious load of satellites. Within a fraction of a second, the rocket is in the air.
On the terrace of the MR Kurup auditorium, where relatives and personal guests of ISRO staff gathered to witness the launch, I looked at the faces around me. Many were smiling. Some were concentrating. Many of us didn’t comprehend all the moving parts of this highly technological event, but we understood that it was something very special. Some were in tears. Maybe it was the sun, or maybe it was just wonder and pride.
(This story has been published in arrangement with GRIST Media)