Giant leap for ISRO

GSLV-Mark III puts a 3.75-tonne unmanned crew module into a sub-orbit as per plan, making it the perfect launch vehicle for India’s human spaceflight.

Published : Jan 07, 2015 12:30 IST

GSLV-Mark III  lifts off during a test flight carrying the CREW module on December 18.

GSLV-Mark III lifts off during a test flight carrying the CREW module on December 18.

THE year 2014 was a great year for the Indian Space Research Organisation (ISRO) with a row of successes that turned the world’s attention on it. On January 5, 2014, its 20-year old “tapas” to build an indigenous cryogenic engine ended on a triumphant note when its Geosynchronous Satellite Launch Vehicle (GSAT-5), powered by an indigenous cryogenic engine, put the communication satellite GSAT-14 into a precise orbit. On September 24, India became the first country in the world to put its spacecraft Mangalyan into Mars’ orbit in its very first attempt.

On December 18, ISRO’s GSLV-Mark III, the newest, heaviest and the most powerful launch vehicle it has built so far, put a 3.75-tonne unmanned crew module into a sub-orbit at an altitude of 126 kilometre. As per plan, the crew module started coming down immediately, sliced through the earth’s atmosphere at a perfect angle, surviving a fiery re-entry, decelerated and, with its three huge parachutes opening up, splashed down in the Bay of Bengal, about 700 km from Port Blair, Andaman and Nicobar Islands. The Coast Guard personnel from the vessel Samudra Pehereden recovered the module.

The spectacular event signalled that India had taken the first steps towards its ambition to send Indian astronauts into space. The mission demonstrated ISRO’s mastery of the re-entry technology and its ability to develop the braking techniques, deceleration technology and thermal protection systems for the crew module.

ISRO notched up two more successes in 2014. Its Polar Satellite Launch Vehicles (PSLVs) put into orbit two navigation satellites, the Indian Regional Navigation Satellite Systems, IRNSS-1B and 1C, on April 5 and October 16.

For ISRO Chairman K. Radhakrishnan, who retired on December 31, it must have been a professionally satisfying year.

Weighing 630 tonnes, the GSLV-Mk III is a new-generation launch vehicle. It is 43.43 metres long. Its core liquid stage, called L110, uses 110 tonnes of liquid propellants. Clinging on to the core stage are two strap-on, solid propellant booster motors, named S-200, each guzzling up 200 tonnes of solid propellants. They are the biggest solid motors built by ISRO. Above the core liquid stage is the indigenous cryogenic engine that will use 25 tonnes of liquid oxygen and liquid hydrogen. On December 18, ISRO did not fire the cryogenic engine. It was a dummy cryogenic stage that sat on top of L110. So the mission was an experimental, passive one. As the module was unmanned it neither had life-support system nor crew escape systems in case of an emergency.

The mission was remarkably smooth for a totally new vehicle. There were no holds in the countdown that lasted 24 hours and a half. The majestic vehicle, painted in white, stood on the launch platform of the second launch pad on Sriharikota’s beachfront. The legends “ISRO, LVM3–X” were prominently written on the vehicle. LVM-X stood for Launch Vehicle Mark III, Experimental Mission. It was titled, LVM3-X/CARE Mission. CARE stands for Crew Module Atmospheric Re-entry Experiment. On top of the dummy cryogenic stage was mated the unmanned crew module which, in itself, was sheathed in heat shields. The vehicle vaulted off the launch pad at the appointed time of 9-30 a.m. “Lift-off normal” came the announcement from the saucer-shaped Mission Control Centre, situated about 6 km from the second pad. Then came another announcement, “S-200 performance normal”

The L110 engine came to life at 114.71 seconds after the lift-off as planned. A novel aspect of the mission was that the two S-200 motors continued to fire for about 34 seconds after the L110 had ignited. So two solid motors and one liquid engine were firing together for about 34 seconds. The two solid motors fell away 148.98 seconds after the lift-off. About 84 seconds later, the payload fairing (the heat shield protecting the unmanned crew module from intense heat during the vehicle’s ascent into the atmosphere) parted in two and fell into the Bay of Bengal. About 317 seconds after the lift-off, the L110 engine shut down. It separated from the vehicle three seconds later. At T plus 325 seconds, at an altitude of 126 km, the unmanned crew module separated from the dummy cryogenic stage and went into a sub-orbit. It started coming down immediately and splashed down in the Bay of Bengal. The entire mission, from the vehicle’s lift-off to the module’s touchdown in the waters, lasted 20 minutes.

Radhakrishnan hailed the GSLV-Mk III mission “a great event” and said “this was the largest launch vehicle programme that ISRO undertook”. He promised the country that the first developmental launch of GSLV-Mk III, with its own cryogenic engine fuelled by 25 tonnes of liquid oxygen and liquid hydrogen, would take place in two years.

Flourishing a golden-hued replica of the GSLV-Mk III, S. Somanath, Project Director, GSLV-Mk III, declared: “India has a new launch vehicle now. We have done it again.”

Both Radhakrishnan and Somanath stressed that the GSLV-Mk III’s two booster motors, each powered by 200 tonnes of solid propellants, were the biggest motors built by ISRO. Somanath said the indigenous cryogenic stage had “simulated” propellants, which had the same mass, density and temperature of the liquid oxygen and liquid hydrogen. The simulated propellants, which filled the liquid oxygen and liquid hydrogen tanks, were liquid nitrogen and gaseous nitrogen respectively. It was the liquid engine, fired by 110 tonnes of liquid propellants, that catapulted the unmanned crew module into a sub-orbit at a velocity of 5.4 km a second

S. Unnikrishnan Nair, Project Director, Human Spaceflight Project, ISRO, called the mission “a grand success” “and “a dream come true for us”. After the module separated from the vehicle, “it [the module] performed as expected,” he said. Its re-entry into the earth’s atmosphere at an altitude of 80 km was perfect. Three parachutes opened in sequence and the module’s velocity of descent was reduced. The braking systems and the deceleration technology worked to perfection. The mission was so precise that the module splashed down just five nautical miles from the expected area, Unnikrishnan Nair said.

M.C. Dathan, Director, Vikram Sarabhai Space Centre, (VSSC), Thiruvananthapuram, said: “Once GSLV-Mark III is reliably proved, it will be launch vehicle for India’s Human Spaceflight Programme,” he said. Besides, a lot of countries “will be in a queue” to launch their satellites, using GSLV-Mk III, he added. Dathan made a pitch for more allotment of funds from the Centre for ISRO’s Human Spaceflight Programme. A.S. Kiran Kumar, Director, Space Applications Centre, Ahmedabad, said: “This is the first step for GSLV-Mk III and CARE mission. ISRO is now looking forward to its manned mission to space,” Kiran Kumar added.

In the assessment of M.Y.S. Prasad, Director, Satish Dhawan Space Centre (SDSC), Sriharikota, the mission’s primary objective of proving the vehicle’s flight through the atmospheric phase was fully met in the mission. He was proud that the 200-tonne solid motors were assembled at Sriharikota. A massive plant for manufacturing the solid propellants for them had been built at Sriharikota, Prasad said.

S. Ramakrishnan, former VSSC Director and former Project Director, GSLV-Mk III, was happy that it was such a trouble-free mission for a newborn vehicle. It was akin to the PSLV missions, which have had 27 successes in a row from 1993, he said.

ISRO cleverly made use of the current two-year delay in developing the indigenous 25-tonne cryogenic engine for GSLV-Mark III in sending the unmanned crew module into a sub-orbit. Since ISRO had not built a satellite weighing four tonnes to put into orbit using this experimental mission in which the cryogenic engine did not fire, it decided that it would build an unmanned crew module and put it into a sub-orbit at an altitude of 126 km and recover it when it returned to the earth. Indeed, the very first forerunner to India’s manned mission to space was when the PSLV put a satellite called Space Capsule Recovery Experiment (SRE) into orbit on January 10, 2007. The SRE splashed down in the Bay of Bengal 12 days later and was recovered.

“It [GSLV-Mk III experimental mission] was a chance for us to take the unmanned crew module on it and recover it because its overall shape and mass will be simulated,” said Dathan. (The VSSC, which he leads, was the key agency for building both the vehicle and the module.) “The re-entry technology—the temperature and turbulence that the module will experience when it re-enters the earth’s atmosphere—will be proved. The thermal protection systems will be proved,” he added.

GSLV-Mk III is the third generation launch vehicle of ISRO to use a cryogenic engine. The first-generation GSLV rockets used Russian cryogenic engines, which were plagued by failures. GSLV-Mk II, with its indigenous cryogenic engine, tasted its first success on January 5, 2014, and put into orbit GSAT-14.

New design

The Union government approved the GSLV-Mk III project in 2002 with an outlay of Rs.2,500 crore. “We were able to complete the project with Rs.2,500 crore. Besides, we reached a stage where we could have this first flight,” said Somanath. “GSLV-Mk III’s design is totally new. It is not like that of the PSLV or the earlier generation GSLVs,” he added. While the PSLV’s solid motors have a diameter of 2.8 metres, GSLV-Mk III’s S-200 motors have a diameter of 3.2 metres each. Its flight on December 18, 2014, was to prove the vehicle’s design and the maturity of the S-200 motors. “The purpose of the flight was to make the launch vehicle experience the rigours of the actual flight,” he added.

The two solid motors, together burning up 400 tonnes of solid propellants, and the liquid engine, burning 110 tonnes of propellants, fired simultaneously for 34 seconds before the two solid motors fell away. “This has not been done before. It is a complex thing to do,” said Somanath. Since the cryogenic stage was passive, the velocity that was imparted to the module was only half of what a regular vehicle would give it, he explained.

The velocity of 5.4 km a second imparted to the module was not sufficient for it to stay in orbit unless the cryogenic stage fired and gave it sufficient velocity. So it started coming down immediately. As the module de-mated from the dummy cryogenic stage and started coming down, it experienced severe disturbances. But the control systems, that is, the six thrusters on board the module, re-oriented the module for a proper re-entry into the earth’s atmosphere.

The module re-entered the earth’s atmosphere at an altitude of 80 km at a velocity of 11 Mach, surviving about 1,000° Celsius of heat generated during the re-entry, said Unnikrishnan Nair. The angle of attack at the point of re-entry was 0°. The ablative carbon-phenolic tiles plastered around the module’s bowl-shaped outer surface enabled the module to survive this agni pariksha [test by fire]. It was like a shuttle-cock, with the cock facing the floor and coming down. From 80 km down, it was flying like a ballistic body. This velocity was reduced by aero-braking.

At an altitude of 15 km, the parachutes came into play. The parachutes developed by the Aerial Delivery Research and Development Establishment (ADRDE) in Agra. The ADRDE is a premier Defence Research and Development Organisation (DRDO) laboratory and only one of its kind in the country that specialises in the design, development and production of para-drop systems for a comprehensive range of military applications. A variety of parachute systems, such as Combat Free Fall Systems, Free Fall Systems and those that are capable of dropping battle tanks and infantry combat vehicles weighing between seven tonnes and 16 tonnes from aircraft, have been realised by the ADRDE. Big aerostats, for surveillance, have been developed by the ADRDE.

In the December 18 mission itself, three parachutes helped to arrest the speed of descent of the module. One was a drogue parachute while the other two were the main parachutes. The main parachutes were massive contraptions with a diameter of 31 m each. As a measure of redundancy, there was another set of these three parachutes in case the first set failed to deploy.

When the parachutes opened up at a height of 15 km, the beacon aboard the unmanned crew module started beaming data about the module’s latitude and longitude to ISTRAC, Bangalore. ISTRAC sent the data to Sriharikota which, in turn, transmitted the coordinates to the Coast Guard vessel.

Once the parachutes opened up and the velocity of the module’s descent came to 7.2 metres a second, the module splashed down. Sensing the impact, the parachutes disconnected autonomously. The module hit the waters about 700 km from Port Blair. Soon, dye-markers from the module sprayed the waters with a fluorescent green-coloured dye, which could be seen from an aircraft. The Coast Guard vessel, which received the coordinates of the splash-down point, reached the area soon to recover the module.

ISRO engineers belonging to its Human Spaceflight Programme are happy that the mission supplied them with enormous data on the module’s aerodynamics, the performance of the control thrusters and the thermal protection systems, and the unfolding of the parachutes, among other things. The Human Spaceflight Programme team includes P. Sunil, its Deputy Project Director, P. Damodaran, B. Anzar and S.S. Vinod.

If the space suits the VSSC has developed are any indication, ISRO’s dream of sending astronauts into space will be realised sooner than expected.

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