ISRO can now restart its cryogenic engine ‘CE20’ in space

Recently, the Indian Space Agency (ISRO) successfully conducted a crucial test that will enable its largest rocket LVM3 to launch satellites into orbits at different altitudes – all in a single mission. This restart capability is made possible through the development of a “multi-element igniter” that can help restart the “CE-20” cryogenic engine on the LVM3 rocket. In this test both Engine and plant performance were normal and required engine performance parameters were achieved as expected, ISRO said.

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As the final stage of the LVM3 rocketit is the cryogenic engine is responsible for placing satellites into various designated orbits (altitudes) in space. This ability improves The operational flexibility and commercial potential a rocket.

When transporting multiple satellites, it is crucial to be able to restart the power stage engine. This allows a single missile to be placed several To transport satellites in different orbits in an efficient manner, eliminating the need several Rockets and multiple launches. In this case, ISRO tested only the first element of the multi-element igniter and simultaneously monitored the condition of the other two Elements. Finally, ISRO would be able to Perform two or three restarts of the cryogenic engine.

PSLV has carried out several missions in which it has placed multiple satellites in different orbits. For example, India’s Polar Satellite Launch Vehicle (PSLV) launched EMISAT, the main satellite, and 28 international customer satellites in April 2019 as part of its 47th mission (PSLV-C45). The primary satellite was launched into a 749 km orbit, followed by two fourth stage restarts to reach a 504 km orbit in which all customer satellites were injected. The fourth stage was then relaunched to reach a 485 km orbit and serve as an orbital platform carry out Space experiments.

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Significantly, this latest cryogenic engine restart test was carried out using a special test device. Normally, ISRO tests the cryogenic engine at a Altitude test Facility that simulates space-like vacuum conditions. However, that is Altitude test is a highly developed process and it has that certain technical limitations.

“While the cryogenic engine is designed to fire for 200-300 seconds in space, we have can only Test it for a maximum of 25 seconds at the ISRO High Altitude Test Facility. These 25 seconds are only a fraction of the engine’s time actually Burn time. For this reason, we developed a unique method to test the actual burn time of the cryogenic engine. This method, known as sea level testing, is not normally suitable for testing cryogenic engines, but we introduced some new techniques that helped us successfully test the cryogenic engine under normal Earth-like conditions,” says Dr. V. Narayanan, Director of ISRO’s Liquid Propulsion Systems Center told WION.

We have developed a nozzle protection system that paves the way for a cost-effective and less complex process for acceptance testing of cryogenic engines.

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How ISRO launched 36 satellites with LVM3 before it was launchable again

In October 2022 and March 2023, the LVM3 conducted commercial missions for the private company OneWeb (now Eutelsat OneWeb), launching 36 satellites on each mission. Although ISRO had not yet developed the cryogenic engine restart technology at that time, ISRO used Cold gas thrusters deftly move the rocket’s cryogenic stage to safely place all satellites into their respective slots.

“The remaining liquid hydrogen in the cryogenic fuel tank was used to maneuver the upper stage so that we could eject all 36 satellites into their designated orbital slots. This is known as a cold gas thruster because There are No fuel combustion is required. This method provides small amounts of thrust that can help achieve small changes in the orbit and attitude (orientation) of the rocket stage. This is also used in some satellites due to its safe and easy operation,” explained Dr. S. Unnikrishnan Nair, Director of ISRO’s Vikram Sarabhai Space Center told WION.

Previously, only the SSLV (smallest rocket) and the PSLV (work rocket) had the upper stage restart capability. Now the LVM3 also has this capability, further increasing the commercial potential of our largest rocket, he added.

About the cryogenic engine “CE 20”.

A cryogenic engine is one of the most efficient and complex rocket propulsion systems. Typically cryogenic engines to use liquid oxygen (LOX) and liquid hydrogen (LH2). The former liquefies at -183 degrees Celsius, the latter at -253 degree Celsius. The complex storage requirements for these supercooled propellants make cryogenic engines more difficult to design and operate compared to conventional engines.

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The indigenous CE20 cryogenic engine developed by Liquid Propulsion Systems Center of ISRO is powerful the upper stage of the LVM3 launch vehicle and was qualified to operate at a thrust of 19 tons.

This engine has successfully powered the upper stage of six LVM3 missions to date. Recently, the engine was qualified for the Gaganyaan mission with a thrust of 20 tonnes to an upgrade Thrust level of 22 tons for the future C32 stage, towards Improving the payload capacity of the LVM3 launch vehicle.