Cryogenic success

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In a major breakthrough that promises to make India self-reliant in space technology, an indigenised cryogenic engine powers the Geosynchronous Satellite Launch Vehicle GSLV-D5 to put the 1,982-kilogram communication satellite GSAT-14 into a precise orbit. By T.S. SUBRAMANIAN

AT 4:35 p.m. on January 5, India’s 20-year-long “tapasya” ended when its Geosynchronous Satellite Launch Vehicle GSLV-D5 put GSAT-14 into a perfect orbit. A welter of emotions—pride, joy, patriotism and, perhaps, anger—engulfed the rocket and satellite engineers seated in the Mission Control Centre (MCC) at the spaceport at Sriharikota in Andhra Pradesh. What was remarkable about the mission was that GSLV-D5 was powered by a cryogenic engine developed indigenously by the Indian Space Research Organisation (ISRO). It was this powerful, uppermost cryogenic stage, that imparted a velocity of 36,000 kilometres/hour to the three-stage vehicle to put the 1,982-kilogram communication satellite into a precise, geo-synchronous transfer orbit (GTO) with a perigee of 179.60 km and an apogee of 35,950 km against the targeted 180 km by 36,000 km. Of the 17 minutes of flight duration, the cryogenic stage fired for 12 minutes, a testimony to its importance in the mission.


The import of the success is manifold: ISRO needs no longer to depend on any country to put its communication satellites weighing more than two tonnes into orbit; India can build any type of rocket, be it propelled by solid fuel, liquid propellants or cryogenic fluids; and using these rockets, it can put any type of satellite into a variety of orbits, including low-earth, polar sun synchronous, and GTO. If ISRO repeats its success with the indigenous cryogenic engine in the next GSLV flight, it will also not have to depend on Arianespace’s Ariane-V rockets to put its (ISRO’s) three-tonne communication satellites into orbit. Two GSLV successes in a row with the indigenous cryogenic engine would also mean that ISRO can use the GSLV Mk-II vehicle to launch Chandrayaan-2, the mission to the moon with its own lander and rover, in 2017.

S. Ramakrishnan, Director, Vikram Sarabhai Space Centre (VSSC), Thiruvananthapuram, said: “It has been a great challenge to realise this cryogenic engine and master this technology. In my opinion, by just having one more successful flight with an indigenous cryogenic engine, the GSLV will reach a level of reliability as that of our PSLV [Polar Satellite Launch Vehicle].” The VSSC is ISRO’s nerve centre, which builds a variety of rockets. The PSLV has had 24 successful flights in a row, from 1994 to the November 5, 2013, mission which put India’s Mars orbiter into a precise initial orbit.

K. Radhakrishnan, ISRO Chairman, called the success a “culmination of 20 years of efforts”. “India has a working cryogenic engine now. We started from scratch to make the teams and build the testing facilities, which are complex in themselves. Cryogenic technology itself is complex in terms of fuel and in terms of their very low temperatures and when the engine works, there is a temperature of 2,000° Celsius, and the engine rotates at 40,000 rpm [revolutions per minute].”

Cryogenic engines are a class apart in terms of complexity and performance (see box on page 10). Of all types of rocket propulsion, cryogenic technology is the most complex to develop. Cryogenics is the science of dealing with super-cooled materials. It involves the use of oxygen at −183° C and hydrogen at −253° C. Handling, storing and pumping these cryogenic fluids demand advanced technology because they are volatile. In the cryogenic engine, liquid oxygen and liquid hydrogen should be mixed in the right proportion, temperature and pressure, and pumped into the combustion chamber by a turbo pump, which should run at a very high speed of 40,000 rpm. The difficulty lies in putting these fluids on fire when they are at such low temperatures.

Cryogenic engines are more efficient than engines that use liquid or solid propellants. A cryogenic rocket stage provides more thrust for every kilogram of propellant it burns compared with rocket stages using solid and earth-storable liquid propellants. Solid propellants provide brute force to an engine, but solid engines are not as efficient as cryogenic engines.

It was Professor U.R. Rao, former ISRO Chairman, who initiated the steps to develop a cryogenic technology base in the early 1990s. On January 12, 1990, he explained to reporters in Chennai why it was important for India to build the cryogenic engine. “Without cryogenic technology, we cannot go in for geostationary satellite launches. Advanced countries took 15 years to attain cryogenic technology. We will do it in eight years but it will be quicker if we have the technology transfer,” he said (Frontline, June 5, 1992).

The anger that welled up in ISRO’s rocket technologists was not misplaced. There were subtle references in the speeches that ISRO’s top brass made at the MCC to the pressure on Russia in 1993 by the United States not to transfer cryogenic technology to India. Although the scientists did not mention the U.S. by name, the message was clear when they sought to clarify that ISRO took 20 years to master the technology because of “the denial of it to India”.

In January 1991, ISRO signed a Rs.235-crore contract with the Russian space agency Glavkosmos for the purchase of cryogenic engines and for subsequent transfer of know-how. It was a commercial contract without any defence/missile ramifications. But U.S. President Bill Clinton, quoting the Missile Technology Control Regime (MTCR) guidelines, pressured Boris Yeltsin, the then Russian leader, into cancelling the transfer of cryogenic technology to India.

Rao had said: “Until October-end of 1993, things went on very well notwithstanding the fact that we had been subjected to embargo by the U.S., which was totally uncalled for. First, nobody uses cryogenic engines for missiles, and secondly, if they [the U.S.] wanted to object, they could have done so earlier and they knew fully well that for the last five years people have been approaching us—and one and a half years after the contract was signed with the Russians, they [the U.S.] woke up. Anyway, commercial motives are behind all these. But the Russians reneged on the contract invoking the force majeureclause…” (Space India, October 1993-March 1994; and Frontline, March 17, 2000).

Remarkable comeback

So, it was no surprise then that ISRO scientists wore the January 5 success of GSLV-D5 on their sleeves.

“Today, I am proud to be an Indian and a member of the LPSC team which made this cryogenic stage,” said M.C. Dathan, Director, Liquid Propulsion Systems Centre (LPSC), Mahendragiri, near Nagercoil in Tamil Nadu. “For the past three years, we did an enormous amount of tests and repeated the tests to prove the reliability of the cryogenic stage. In fact, we got energy from the failures and re-bounded from them,” Dathan said.

K. Sivan, Mission Director, GSLV-D5, described the launch as a historic one, which established the fact that “India can demonstrate its indigenous cryogenic engine, which can put a two-tonne satellite into orbit.” He called the indigenous cryogenic engine “a naughty boy who has become obedient today”. This was a reference to the failure of ISRO’s maiden attempt with its indigenous cryogenic stage in GSLV-D3 to put GSAT-4 into orbit on April 15, 2010. The success capped a remarkable comeback within four months of a near disaster on August 19, 2013, and within four years of the failure of GSLV-D3. Besides, the GSLV-F06 mission with a Russian cryogenic stage had failed on December 25, 2010. It was as if the GSLVs were jinxed. Out of a total of seven GSLV flights beginning with the first in April 2001 and up to December 2010, four were failures: three with Russian cryogenic stages and one with the Indian version.

So it was with great expectations and trepidation that ISRO scheduled the GSLV-D5 liftoff at 4:28 p.m. on August 19, 2013, from the second launch pad at the Satish Dhawan Space Centre (SDSC) at Sriharikota. However, 75 minutes before the liftoff, the liquid fuel from the rocket’s second stage started leaking. The fuel cascaded down the rocket’s core first stage and the four strap-on motors around it. Clouds of fumes engulfed the vehicle. Mission Control quickly cancelled the launch.

Near-disaster

M.Y.S. Prasad, Director, SDSC, was the first person to notice the leak. About 800 kg of liquid fuel called unsymmetrical dimethyl hydrazine and dinitrogen tetroxide had leaked out of the propellant tank made out of an aluminium alloy called Afnor 7020. As the fuel rained down on the vehicle’s sides, it reacted with the paint and generated clouds of fumes. Had the fumes and the temperature exceeded a certain level, a fire would have broken out engulfing the rocket and the umbilical tower in the launch pad. Realising the gravity of the situation, Prasad took immediate steps to pump about 170 tonnes of water to cool the fumes and the leaked propellants, and spray the launch vehicle. Another 200 tonnes of water was sprayed around the umbilical tower to neutralise the fuel that had leaked out. “It was a very critical time for us that day. About 500 people worked for 24 hours a day from August 19 to 26 to neutralise the leaked fuel, de-mate the connections from the umbilical tower and bring the vehicle safely back to the vehicle assembly building [VAB] and clean the stages,” Prasad said.

GSLVs are three-stage vehicles measuring 49 metres in length and weighing 414 tonnes. The core first stage uses solid propellants. Four strap-on booster motors, which use liquid fuel, are strung around the core stage. The second stage uses liquid fuel. The third, upper stage uses cryogenic propellants. The satellite is married up with the third, cryogenic upper stage. The three stages and the satellite are stacked up vertically on a mobile launch pedestal, or MLP, in the 18-storey-tall VAB. One week before the launch date, with the rocket standing it, on the MLP, which is equipped with 16 wheels and four jacks, is wheeled to the umbilical tower/launch pad, one kilometre away, on a twin-rail track. It takes many hours for the vehicle to inch its way to the launch pad. After the rocket reaches the launch pad, the MLP is anchored there. After the catastrophic situation was averted in August 2013, GSLV-D5 standing on the MLP was taken back on the rail track to the VAB.

Rocket's restoration

The rocket’s restoration began under the supervision of K. Narayana, former Director of the SDSC. GSAT-14, which was encapsulated in the heat shield, was preserved and tested periodically. The cryogenic upper stage was preserved and tested several times. The rocket’s second stage received a new propellant tank made of the aluminium alloy AA 2219. Radhakrishnan said: “We had to refurbish the strap-on booster motors. All the components and parts that had come in contact with the leaked propellant were replaced. The electronic packages residing in the strap-on stages were replaced. The rocket’s core first stage, which uses solid propellants, was replaced.”

After the failure of the GSLV-D3 flight in April 2010 when the fuel-booster turbo pump (FBTB) ignited but the ignition failed to sustain, ISRO took no chances. Radhakrishnan said ISRO did a series of ground tests on the subsystems and the cryogenic engine at the LPSC after making the necessary changes in the design of the FBTP and the oxidiser turbo pump. An important test was devised to test the FBTP in operating conditions at cryogenic temperatures. After this test, ISRO wanted to simulate the ignition of the cryogenic engine in high-altitude conditions. In actual flight, the cryogenic engine ignites in the vacuum of space and this had to be simulated in a facility called HAT (High Altitude Test) of the LPSC at Mahendragiri, where a vacuum chamber was created to simulate the conditions. ISRO made use of the HAT facility being established for GSLV Mk-III. It successfully simulated the firing of the indigenous cryogenic engine in vacuum in the HAT facility in March and April 2013.

A committee of experts analysed the failure of the previous seven GSLV flights. After the December 2010 flight with the Russian cryogenic stage failed, ISRO changed the design so that the connectors were mounted in the stage. Wind tunnel tests on a GSLV model were done at the National Aerospace Laboratories, Bangalore, and in Russia. Prasad said: “We had an exciting time when we had to refurbish the vehicle. This is proof that we have mature technology and mature leadership.” Ramakrishnan added, “A tremendous effort was put in to realise the vehicle within the shortest possible time. I am proud to be part of the team.”

So it was a refurbished vehicle with new second and first stages and new strap-on motors that was used in the reattempted GSLV-D5 launch on January 5. The previous day, Dathan told Frontline that “we have done everything humanly possible” to ensure that the GSLV-D5 mission would be a success.

Nearly four years of innovation, hard work and team effort paid off. The 29-hour countdown progressed smoothly. GSLV-D5 roared out of the second launch pad on the dot at 4:18 p.m, with GSAT-14 on-board. It thundered into the sky, riding on orange-yellow flames. Five minutes after liftoff, when Mission Control announced “Cryo ignited”, applause erupted from the MCC. However, there was palpable tension about how the next 12 minutes would go. There were rounds of applause every time Mission Control declared with aplomb, “All cryo parameters normal one minute after cryo ignition, cryo operating at normal conditions plus seven minutes, vehicle accelerating, vehicle performance normal plus 14 minutes, cryo shut-off, injection conditions normal.” At the end of 12 minutes of the cryogenic engine firing out of a total flight duration of 17 minutes, when Range Operations Director M.S. Panneerselvam announced, “GSAT-14 separation successfully accomplished”, extended applause rang out. There were hugs and handshakes, and Sivan’s elated colleagues even carried him on their shoulders.

Besides Radhakrishnan, Ramakrishnan and Dathan, the core team behind the cryogenic achievement included Sivan; N.R.V. Kartha, Project Director, Cryogenic Upper Stage Project (CUSP); V. Narayanan, Group Director, Cryogenic Engine Group; M. Uma Maheswaran, Vehicle Director; and R. Mohan, Associate Project Director, GSLV-D5. M. Nageswara Rao was Project Director, GSAT-14.

Radhakrishnan said: “The Indian cryogenic engine has performed as expected and injected GSAT-14 precisely into orbit. This is a big achievement for the GSLV programme. It is the result of 20 years of effort and three and a half years of excruciating pain to understand and master cryogenic technology.” He paid tributes to U.R. Rao, who declared in 1992 that “we will have the indigenous cryogenic engine”, and to all former ISRO Chairmen and Project Directors who put their “heart and soul” into developing the engine.

The pressure in the engine chamber, the turbo pump speed, temperature and all other parameters were exactly as predicted. The engine burned for 720 seconds, developed the required thrust and unleashed the correct velocity needed for the satellite injection. Dathan called it “a kind of miraculous performance”, which meant that the engine’s design, quality and reliability were perfect.

Ramakrishnan called it “a memorable launch”.

Soon after GSAT-14 went into orbit, its solar arrays, one on each side, with two panels each, unfolded, like an accordion, and ISRO’s Master Control Facility (MCF) at Hassan in Karnataka took charge of the satellite. On January 6, 7 and 9, ground controllers at the MCF beamed commands to the propulsion system called Liquid Apogee Motor (LAM) on-board the satellite to fire, taking GSAT-14 into a near-circular geostationary orbit with a perigee of 35,462 km and an apogee of 35,742 km. The satellite was expected to reach its final geostationary orbit at a height of 36,000 km above the earth on January 19 and to become operational by January 27.

The Space Applications Centre, Ahmedabad, headed by A.S. Kiran Kumar, provided the 12 transponders to GSAT-14. The satellite was built at the ISRO Satellite Centre, Bangalore, headed by K. Shivakumar. GSAT-14, which will have a mission life of 12 years, will be used for telecasting, telecommunication, tele-medicine and tele-education. With this success, ISRO has planned a series of GSLVs powered by indigenous cryogenic stages. It plans to launch the next GSLV a year from now to put GSAT-6 into orbit. Thereafter, more GSLVs will carry on-board GSAT-7A, GSAT-9, Geo-Imaging Satellite and a few more communication satellites of the two-tonne class.

Thereafter, it will be GSLV-MkIII, the “powerhouse” that ISRO is building. The rocket, which will weigh 600 tonnes and be 50 metres in height, will feature a cryogenic engine with 25 tonnes of propellants. GSLV-MkIII can put a four-tonne satellite into a GTO.

http://www.frontline.in/cover-story/cryogenic-success/article5596536.ece?homepage=true