ISRO’s twin win for India’s space sector

ISRO successfully tested the GSLV and added a satellite to its network of navigation tools

The textbook launch of the Geosynchronous Satellite Launch Vehicle (GSLV)-F12 that carried India’s navigation satellite, NVS-01, into a Geosynchronous Transfer Orbit around Earth is significant for more than one reason.

The 2.2-tonne satellite is an important cog in the constellation of eight satellites launched earlier, and now wheeling around Earth to make up the Navigation with Indian Constellation (NavIC) network. The NVS-01 belongs to a new generation of satellites that are equipped with indigenously-developed rubidium atomic clocks to give precise positional data, and joins the cluster as its ninth member. The Indian Space Research Organisation (ISRO) plans to launch four more similar satellites to complete the NavIC, making it one of the best regional satellite navigation networks in the world.

The NavIC network covers the subcontinent and over 1,500 km beyond India’s borders, including parts of China. This satellite array will work with ground stations to generate unprecedented position and timing accuracy. This will have key applications in land and marine transportation, and in India’s burgeoning civil aviation sector where state-of-the-art navaids (navigation aids) depend on satellites. Besides providing Standard Position Service (SPS) for civilian users, the Restricted Service (RS) of the NavIC has enormous value for India’s armed forces which could access critical navigation information and timing data for military operations. The SPS signals of the NavIC are reportedly compatible with the US Global Positioning System (GPS), Russia’s Glonass, the European Union’s Galileo, and China’s BeiDou.

The successful launch on May 29, however, was not just about the NVS-01. The GSLV’s flight, in a sense, was a redemption of sorts for ISRO which was eager to send the big booster aloft after the GSLV-F10’s launch failure in August 2021 when one of the booster engines failed, and the rocket crashed into the Indian Ocean. Investigators later found that a faulty valve had led to low pressure in the liquid hydrogen tank in the indigenously-built cryogenic upper stage (CUS) of the rocket. ISRO has put that setback behind as the GSLV’s latest mission validated all its flight parameters. As ISRO chief S Somanath told the media after the launch, “The corrections and modifications in the cryogenic stage that we have done in this stage and the lessons that we learnt out of it to make the cryogenic stage more reliable have paid benefits.”

Cryogenic engines use fuels such as oxygen and hydrogen in liquid form stored at extremely low temperatures — oxygen at below -183 degrees Celsius and hydrogen at below -253 degrees Celsius — to produce enormous thrust per unit mass (engineering parlance for the mass of fuel the engine needs to provide maximum thrust for a specific period such as, say, pounds of fuel per hour per pound of thrust). Developing a cryogenic engine from such propellants is a huge challenge that only a few countries have overcome, and the technology remains a zealously guarded preserve.

The development of the GSLV was plagued by many delays that observers even nicknamed it ‘ISRO’s naughty boy’. Since its prototype first test-flew in 2001, the GSLV has had an unflattering six failures in 15 launches. Its first stage comprises a solid rocket motor (proven on the Polar Satellite Launch Vehicle), while liquid propellants make up the second stage; the all-important CUS completes its three-stage configuration. Rockets such as the GSLV are the workhorse launchers for satellite launching agencies of the United States, the EU, Russia, China, and Japan. But India took more than three decades to get its first GSLV off the drawing board as New Delhi dragged its feet over a policy decision: whether to buy the all-important cryogenic engine technology off-the-shelf, or to develop it on its own.

India’s cryogenic pursuit began in January 1991 when ISRO sealed a deal with the Russian Space Agency Glavkosmos on the transfer of cryogenic technology. But exaggerated US jitters about India using its space launch capabilities for military purposes — along with India’s potential to become a leading space power — pressured Moscow to renege on the deal. This forced New Delhi to eventually buy cryogenic engines from Russia. For ISRO, though, this turned out to be a blessing in disguise as it spurred Indian engineers to develop cryogenic engine technology on their own. In 1994, the CUS project was launched to build a cryogenic engine and rocket stage based on the Russian design.

But there is a twist in the tale of ISRO’s homegrown cryogenic technology — and it comes from the Liquid Propulsion Systems Center (LPSC) in Thiruvananthapuram, which has developed the propellant for a semi-cryogenic engine. The LPSC’s answer to the risky liquid hydrogen is the humble kerosene, which can be stored at normal temperatures. Using oxygen as an oxidiser, the kerosene pumps up rocket thrust almost three times. In fact, NASA used kerosene and oxygen in the first stage of its mighty Saturn rocket to beat the Soviets — who were still undecided about hydrogen and kerosene — to the Moon in the 1960s. Even today, SpaceX’s Falcon 9 uses rocket-grade kerosene and liquid oxygen in its Merlin engines.

Chances are that a semi-cryogenic engine will power the GSLV in its new avatar, the LVM 3, as it carries India’s first crewed space mission, Gaganyaan, into orbit.

(Prakash Chandra is former editor of the Indian Defence Review. He writes on aerospace and strategic affairs.)

Disclaimer: The views expressed above are the author's own. They do not necessarily reflect the views of DH.