India Today - - UPFRONT - By Amar­nath K. Menon

On June 5, the In­dian Space Re­search Or­gan­i­sa­tion (ISRO) crossed a sig­nif­i­cant mile­stone—the flaw­less launch of the heav­i­est rocket it has ever em­ployed, par­tially pow­ered by an in­dige­nously de­signed cryo­genic en­gine. The rocket, GSLV Mk. III, weighs 640 tonnes, and is ca­pa­ble of car­ry­ing a max­i­mum pay-

load of 4,000 kg into or­bit. The most sig­nif­i­cant fea­ture of the launch was that the en­gine per­formed flaw­lessly be­fore eject­ing the satel­lite. It is the most pow­er­ful up­per stage de­vel­oped by ISRO, and uses a com­bi­na­tion of liq­uid oxy­gen and liq­uid hy­dro­gen, loaded in two in­de­pen­dent tanks, as a pro­pel­lant com­bi­na­tion. The devel­op­ment of a cryo­genic stage has unique de­sign chal­lenges, with liq­uid hy­dro­gen and oxy­gen stored in its tanks at (-)253 de­gree Cel­sius and (-)195 de­gree, re­spec­tively. To store th­ese cryo­genic flu­ids at th­ese ex­treme tem­per­a­tures, a special multi-layer in­su­la­tion is pro­vided for the tanks and other struc­tures.

In­de­pen­dence apart, an indige­nous ve­hi­cle means lower costs of putting space­craft into or­bit, says K. Si­van of the Sarab­hai fa­cil­ity

The Mk. III, says ISRO chair­man A.S. Ki­ran, will “in­crease our ca­pa­bil­ity to launch satel­lites man­i­fold. The pay­load will in­crease in fu­ture flights”. It could also be the launch ve­hi­cle used to send “In­di­ans into space, from In­dian soil, us­ing In­dian rock­ets”.

The en­gine, des­ig­nated CE-20, was de­vel­oped at the ISRO liq­uid propul­sion com­plex at Ma­hen­dra­giri, and is ca­pa­ble of gen­er­at­ing about 20 tonnes of thrust. “No tech­no­log­i­cal el­e­ment was bor­rowed or adapted from any other space or­gan­i­sa­tion,” em­pha­sises S. So­manath, di­rec­tor of the liq­uid propul­sion sys­tems cen­tre. The tech­no­log­i­cal chal­lenge in de­vel­op­ing such an en­gine is daunt­ing—hy­dro­gen, for in­stance, must be cooled to be­low (-)250 de­grees centi­grade be­fore it be­comes a liq­uid, which puts sig­nif­i­cant strain on the en­gine it­self. “In­de­pen­dence apart, an indige­nous launch ve­hi­cle means lower costs of putting space­craft into or­bit,” adds K. Si­van, di­rec­tor of the rocket de­sign fa­cil­ity, Vikram Sarab­hai Space Cen­tre, Thiru­vanan­tha­pu­ram.

LIFTOFF GSLV Mk. III takes off at the Sri­harikota fa­cil­ity on June 5

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