Harnessed Star Fuel

On January 5th 2014 the Indian Space Research Organisation (ISRO) successfully demonstrated its indigenous cryogenic rocket engine by sending a two-ton satellite into geostationary orbit. Linde Kryotechnik and Linde Engineering India co-developed and constructed a test facility, which helped achieve this national milestone.
It is the fuel of stars: hydrogen. Our sun burns by fusing its atoms into helium. Hydrogen is also the most abundant chemical substance in the universe. And it is the preferred fuel for rocket-powered flight. But harnessing this element for sending payload into space comes with a very complex challenge: it must be cooled to its liquid state in order to fit into reasonably sized fuel tanks – at under minus 253° Celsius. “Were it not for this cryogenic requirement, hydrogen would be used exclusively as a rocket propellant”, says Ernst Adler, COO of Linde Kryotechnik. Thus, although several alternative fuels have been developed to propel payload into space, cryogenic rocket engines remain the pinnacle of aeronautic engineering.

The newest addition to the exclusive club of countries that have mastered cryogenic rocket technology is the nation of India. After one partially-successful attempt in the past, the Indian Space Research Organisation (ISRO) succeeded at placing a two-ton satellite into geostationary orbit, 36.000 kilometres above the earth’s surface, on January 5th 2014. The cryogenic upper stage needed to achieve this feat was developed entirely in India and has been 20 years in the making. One of the major stepping-stones in ISRO’s mastery of this cryogenic technology was its rocket engine test facility at Mahendragiri in Tamil Nadu State. For its construction, ISRO commissioned experts from Linde Kryotechnik in Switzerland and Linde Engineering India. “The test facility was surely one of the key elements in optimizing our engine design to make it a reliably functioning piece of equipment”, says the Chairman of ISRO, K. Radhakrishnan.

After receiving the test facility’s proposed layout and process design in early 2005, the first step for Ernst Adler and his colleagues was to review the layout and process design and carry out detail engineering. “The major challenges were the required pressure stability of 400 bars and nominal pipe sizes up to DN 250”, he remembers. In order for cryogenic technology to function within these parameters, the tolerances are minimal: “We had to employ highest grade transfer pipes and valves for the super cooled fuels to supply efficiently at this pressure and in this quantity”, says Adler. Because the fuel travels distances of several dozen meters on the 9’200 square-meter test facility, shrinking and expansion of the pipes and other involved components is increased to several centimetres. “This project was one of our biggest so far and looking back, we are all very proud it worked out the way ISRO had envisioned it”, Adler says. “The exceptional cooperation with our partners at Linde Engineering India played a key role”, he adds.
“The January launch was a landmark achievement for our nation”, said ISRO Chairman, K. Radhakrishnan. It is a pivotal point for the country’s future plans of sending humans to the moon and beyond. To Ernst Adler, ISRO’s success also signifies a milestone for Linde Kryotechnik: “It demonstrates that we can deliver high end cryogenic technology for even the most advanced application – testing of cryogenic engine.”