The GSLV launch vehicle D6 carrying GSAT-6 lifts off from the Satish Dhawan Space Centre, Sriharikota, Andhra Pradesh PTI
On the face of it, the August 27 successful
launch of the three-stage Indian launch vehicle GSLV(Geosynchronous
Satellite Launch Vehicle) seems yet another routine orbital mission
pulled off by the Indian Space Research Organisation (ISRO). The
flawless GSLV-D6 mission has helped the Indian space agency validate
the performance of the domestically made critical upper cryogenic
engine stage for the second time after the successful maiden test
flight of GSLV equipped with an indigenous cryogenic engine stage in
January 2014.
The technologically complex cryogenic propulsion system is the
zealously guarded preserve of only a handful of advanced space-faring
countries which are not willing to transfer the technology of this
crucial rocket propulsion system. India is the sixth country in the
world to have mastered the cryogenic propulsion system, which provides
more thrust for every kg of fuel burnt in comparison to the solid and
earth storable liquid propellants.
By successfully demonstrating the capability of the indigenous
cryogenic engine stage that is driven by liquid hydrogen and liquid
oxygen at extremely low temperatures, ISRO has overcome a major
technological barrier in so far as building a domestic heavy lift
launch capability is concerned. Indeed, the 630-tonne heavy lift
GSLV-MKIII capable of placing a 4-tonne class satellite payload into a
geostationary transfer orbit is now being subjected to a slew of
qualification trials as a prelude to its maiden flight in 2016. The
current Mark-II version of GSLV has been designed to orbitsatellite
payload weighing upto 2.5-tonne. The message of the successful GSLV-D6
mission is that no technology, however complex and challenging it might
be, is beyond India's capability to develop and deploy.
With a lift off weight of 416- tonne, the 49-metre-tall GSLV-MK II
showcases the painstaking endeavours of the Indian space agency spread
over two decades. It precisely injected 2,117-kg. GSAT-6
communications satellite designed for multi-media services into its
intended orbit. This satellite, equipped with an unfurlable, S-band
antenna, the largest so far deployed on an Indian satellite, will be
used by the Indian defence forces for “strategic purposes”. In addition,
it will also be deployed for search-and-rescue missions and disaster
mitigation and emergency response.
As it is, the routine deployment of GSLV would free India from its
dependence on the Ariane-5 vehicle of the European space transportation
company, Arianespace, for getting its two-tonne plus GSAT/INSAT
satellites off the ground. This “launch independence” would save Indian
exchequer the enormous cost involved in paying for a commercial launch
service. It costs around $90-million for launching a communications
satellite in 3.5-tonne weight class through a procured commercial space
vehicle. India can also consolidate its position in the global
commercial launch market by offering the services of GSLV-MKII for
launching the satellites of international customers on commercial terms.
Of course, India has made modest forays in the satellite launch market
by promoting its four-stage space workhorse PSLV(Polar Satellite Launch
Vehicle) as a cost-efficient space platform for launching light weight
satellites into a variety of orbits for a fee. PSLV has set an excellent
track record of reliability by launching as many as 45 satellites from
19 countries. However, it is only a heavy-lift vehicle like GSLV-MKIII
that could add “real muscle” to the Indian launch service business.
Clearly, a home-grown, high- performance launch vehicle capable of
meeting Indian needs for launching heavier class satellites makes for
strategic sense because it could insulate the country from “whims and
uncertainties” that the multi-billion dollar global space launch market
could face in the future due to shifting political, geo- strategic
priorities. Further, with a heavy-lift capability under its thumb, there
is no need for India to worry about the notorious technology denial
regime as exemplified by the US trade sanctions and technology embargo.
Despite the tall talk of Indo-US strategic cooperation, the US
continues to be suspicious about India's intention of mastering the
nuances of advanced technology elements. The success of GSLV clearly
reflects the Indian defiance of US sanction regime. The ISRO,which in
the 1980s, had carried out experimental studies on the feasibility of
developing a cryogenic propulsion system, deemed it prudent to acquire
the cryogenic engine technology from the erstwhile Soviet Union so that
the GSLV — the first two stages of which are derived from PSLV—will be
propelled by a home-grown upper cryogenic engine stage, without much
loss of time. Accordingly, in 1991 the ISRO signed an agreement with
Soviet space agency, Glavkosmos, for the supply of two flight-ready
cryogenic engine stages, along with the transfer of the sensitive
cryogenic engine technology. This was before the breakup of the USSR.
As it is, the cryogenic engine stage the erstwhile Soviet Union
agreed to provide was a modified version of the N-1 rocket stage.
Following the breakup of the Soviet Union, US found it rather easy to
blackmail a politically turbulent Russia into dropping its commitment of
transferring the cryogenic engine technology to India. The argument of
US was that the transfer of dual use technology of cryogenic engine
constituted the violation of the provisions of Missile Technology
Control Regime(MTCR). The US logic did not make any sense since
cryogenic propulsion is never a preferred choice for driving a strategic
missile system.
The Indo-Russian agreement was diluted down to the supply of
just seven flight-ready cryogenic engine stages to sustain the flights
of GSLV till such time as a home-grown cryogenic engine stage gets
ready. Out of these seven, six have already been used by ISRO for GSLV
flights. Out of the six GSLV flights with Russian-supplied upper
cryogenic engine stage, three have been a failure. Like its Russian
counterpart, the Indian cryogenic engine also works on “staged
combustion cycle” technique wherein hydrogen is partially burnt with a
little oxygen in the gas generator. The hot gases, which drive the
fuel-booster turbo pump, are injected at high pressure into the thrust
chamber where the rest of oxygen is introduced to facilitate the fuel
combustion. Before going to the gas generator, the incredibly chilly
liquid hydrogen is used to cool the thrust chamber whose temperature
rises abnormally high when the engine is fired.
The challenge involved is sustaining the functional efficiency of
the turbo pump that rotates at 40,000 rpm(revolution per minute) in
order to send upto 18-kg of propellant every second into the thrust
chamber in the face of the sharp temperature gradient. Not surprisingly,
for ISRO the development of cryogenic engine was really a tough and
painstaking job involving as it does the mastery of materials
technology, operation of turbo pumps that operate at cryogenic
temperature, along with the challenges involved in handling liquid
hydrogen and liquid oxygen.
ISRO is now developing cost-efficient and eco-friendly,
semi-cryogenic engine stage capable of developing 2,000-kN thrust. By
replacing the core stage of the existing launch vehicles with the
semi-cryogenic engine stage, it would be possible to considerably
enhance the payload carrying capability of the vehicle in a
cost-efficient manner. Such unified vehicles are considered ideal for
deep space probes, including sample return mission to moon. To render
orbital missions both affordable and routine, ISRO has now focussed its
attention on developing the advanced air-breathing propulsion system in
tandem with reusable space vehicle technology.
The writer is a Bangalore-based analyst, specialising in space technology, defence and terrorism-related issues.
