ISRO: Extreme Engineering
ISRO succeeds
in the cutting edge Cryogenic rocket technology to propel Indian space program
forward
(Excerpts appeared in Special Report, Business India, February 17-March 2,
2014)
Space Spectacle: The
successful launch of GSLV D-5 on Jan 5, 2014 from SatshDhawan Space Centre,
Shriharikota, Andhra Pradesh (Courtesy ISRO)
Why is a rocket technology developed by the Indian Space
scientists to operate at an extremely cold temperature of minus 250 °C, also
known as Cryogenic engine technology, very hot? Why did it take India nearly 20
years to successfully develop this? What does it hold for the future of ISRO?
These were some of the basic questions Business
India tried to get answers for after the recent much heralded success of
India’s GSLV D-5 (Geo-Stationary Satellite Launch Vehicle—see box Space Jargon Explained)
This success in Cryogenic rocketry at ISRO will soon allow
it to launch its own communication and weather satellites (which weigh 2 tons
and above). ISRO has been designing and building satellites for various
applications like communication, weather prediction, TV broadcasting, earth
observation and resource management, disaster management, distance education, navigation,
cartography, oceanography and reconnaissance for over three decades, while at
the same time developing the required rockets (Launch Vehicles –in space
jargon). However the Indian work horse for satellite launch—PSLV (Polar
Satellite Launch Vehicle)is capable of launching only the lighter satellites weighing
one ton or less onto 400-1000 km low earth orbits. The heavier communication
satellites which need to be put into geo stationary, 36000 km orbits, were
being launched by the French led European commercial launch company Arianespace
(
http://www.arianespace.com/index/index.asp).
Space Jargon Explained Geostationary orbit Any object placed in orbit at 36,000 km above the equator
will take the same amount of time as Earth does to complete one revolution.
This makes it stationary in relation to Earth. A dish antenna receiving signals
from the satellite does not need to move to continuously track it, which makes
tracking cheaper and less complex. Why multi-stage
rockets? The heavier the weight that is carried into space, the
larger must be the rocket ferrying it, because of the need for more fuel and
power. It costs approximately $30,000 to put one kilo into geostationary orbit.
In a multi-stage rocket the burnt out stages are detached one by one and drop
to Earth so that less and less weight is actually carried into orbit. Why should we use
liquid-fuelled rockets when solid-fuelled rockets are much simpler to make? Solid-fuelled rockets cannot be turned on or off at will;
once lit they burn till the propellant is exhausted. A liquid-fuelled rocket,
on the other hand, can be easily controlled like the ignition key and
accelerator of a car. Remote sensing Observing Earth from a distance and getting information
based on the reflective properties of different objects is known as remote
sensing. Remote sensing can also be done using aircraft, but satellite remote
sensing is far cheaper and more comprehensive. India achieved perhaps the best
Remote sensing satellite system in the world way back in 1995 with IRS 1-C. PSLVPolar Satellite Launch Vehicle (PSLV), commercialized since
mid ‘90s can launch a one-tonne satellite in a 400-1,000-km orbit. It has been
primarily used for launching India’s best in class IRS remote sensing
satellites. It has also been used innovatively for Chandrayaan and Mangalyaan,
India’s Moon and Mars missions. Communication
SatellitesThey are like a TV tower that can cover the entire Indian
subcontinent, positioned 36000 km up in the sky at the equator south of India.
India has launched many of them for telephony, TV broadcasting, weather
prediction, climatology, disaster management, Global Positioning and
Navigation, search and rescue etc.
GSLVGeostationary Satellite Launch Vehicle is a rocket which
uses for the first time a Cryogenic third stage that will give enough push to launch
a 2 ton communication satellite into a Geo Transfer Orbit eventually placing
the satellite in a 36000 km high orbit.
Cryogenic EngineRockets engines using liquid Oxygen and liquid Hydrogen as
oxidizer and fuel are called Cryogenic rockets as the fuels have to be
maintained at extreme cold temperatures of minus 250 °C.
Specific ImpulseThe thrust that the rocket will get for a given mass flow
rate of fuel is Specific Impulse. It is the lowest for Solid Propellant rockets,
followed by the earth-storable liquid fuels then semi-cryogenic and then fully
Cryogenic. The unit of Specific Impulse is seconds. In Cryogenic one gets 415
sec, in solid fueled it is 270-80 sec. in earth storable liquid fueled it is
300 sec and in Semi Cryo it is 315.
SatnavA Satnav or Satellite Navigation system is a system that
allows small electronic chips on the ground (in your car, bus, airplane, ship
or a battle tank) to determine their location (longitude, latitude, and
altitude) to high precision (within a few metres) using signals transmitted by
a constellation of satellites.So far the United States NAVSTAR Global Positioning System
(GPS), the Russian GLONASS are global operational Satnav systems. China is in
the process of expanding its regional Beidou navigation system, whose services
are being offered to Pakistan and other Asian countries into a global Compass
navigation system with a constellation of 35 satellites. The European Union's
Galileo positioning system is in initial deployment phase. France has set up a
rudimentary regional system called DORIS which is less accurate than GPS. Japan
is in the process of developing its regional navigation systems, QZSS (Quasi
Zenith Satellite System) of four satellites. The Indian SatnavIRNSS (Indian Regional Navigational Satellite System) consists of 7 satellites. One
satellite IRNSS-1 was launched in July 2013 and four more are being launched in
2014. All the segments (space, ground and user recievers) are being built in
India and will be in Indian control. Sovereign control is essential in war like
situations when the signals from other systems may be turned off. It is intended to provide an all-weather
absolute position accuracy of better than 7.6 meters throughout India and within
a region extending approximately 1,500 km around it.
GAGANA satellite and ground based system GAGAN (GPS-Aided Geo-Augmented
Navigation) has been developed by ISRO in collaboration with the Airport
Authority of India to help Indian Civil Aviation using existing GPS signals
from NAVSTAR and making them more reliable for aviation purposes. A GAGAN
transponder has already been placed in orbit and the system is undergoing final
certification for safety and accuracy.
It is to the credit of ISRO that the Indian Moonshot
(Chandrayaan ) and the Mars-shot (Mangalyaan ) were launched by this less
capable rocket (PSLV),thereby gaining respect and admiration amidst the
space faring world, for ISRO’s ingenuity, innovation and frugal engineering.
After the successful launch of GSLV D-5 there will be some
more developmental flights before it is declared a commercial launch vehicle.
Till then GSLV will be used to launch some experimental or domestic
developmental satellites including India’s own Satnav systems GAGAN and IRNSS (see
box Space Jargon Explained ). GSLV
would have adequate power to put the current class of INSAT Communication
Satellites which weigh around 2 tons to Geostationary orbits.However, for the
next generation heavier satellites or even the more ambitious exploratory
missions to Moon, Mars and beyond, ISRO is already working on the GSLV Mark
III—a rocket with a two times more powerful Cryogenic stage under development.
It can then put a 4-5 ton satellite into geostationary orbit or have more
substantial Moon and Mars missions and perhaps even a manned space flight.
What are the commercial possibilities of these developments?
According to Dr K Radhakrishnan, Chairman, ISRO, “India has already launched 35
foreign satellites for 18 countries using PSLV. Three of them were dedicated
launches while others were piggy rides on our own missions. We are going to
have one more in 2014, when we launch Spot-7,a 712 kg Earth Observation
satellite from France, identical to Spot-6 that we launched in 2012. There will
also be 3 foreign co-passenger payloads in that PSLV flight. Germany has 800 kg
satellite which we will launch with PSLV in 2014-15. There will also be one
dedicated flight for 3 satellites of 300 kg each from UK for science, remote
sensing etc. There will be one more for a Singapore satellite. These four
flights of PSLV are already on the table. There are other smaller ones. Antrix is
marketing our capabilities to foreign customers. We have 7-9 of our own
satellites to be launched for communications, navigation (GPS), meteorological
purposes using GSLV.”
As for the high profile Moon and Mars missions Radhakrishnan
who is the first Engineer-MBA (IIM,B 1976) to head ISRO, adds, “So far we have
received generous applause from all international space agencies for both the
complex maneuvers of Mangalyaan and the success of GSLV. I am sure new
commercial deals will follow with many countries.Certainly its success in the Mars
Orbiter Mission (Mangalyaan) has raised PSLV’s profile. It is considered novel
since we used a comparatively low powered vehicle, to put 350 kg fuel in the
satellite to go to exit point for Mars orbit. One could also use a very
powerful rocket as NASA did with MAVEN recently. Our frugality also meant that it
took more time to reach the Mars exit point and several complex maneuvers were
involved. To each lift off time a new trajectory design and new steering
program had to be prepared. If GSLV were available we could have put a bigger
satellite or the same satellite with a larger orbit”.
This is great news but what is so complex about Cryogenic
technology that it has taken over 20 years for development whereas the earlier
successful rockets both solid and liquid fueled were developed in less than a
decade? To understand this first of all we need to understand what is
Cryogenics and then what is Cryogenic rocketry. When scientists talk of
Cryogenics or the “science of the extreme cold” they start at roughly minus 150
°C.
How cold is Cryogenics?
- ·
We might start using our woolens when the
temperature starts going below 20 °C.
- ·
Ideally the refrigerators we use at home cool
the contents to about 4 °C and about minus 18 °C in the freezer.
- ·
Right now Indian army jawans are facing
temperatures around minus 40°C at their outposts in Siachen Glacier, and as we
know hundreds of them have died due to inclement cold weather at high altitude
and not enemy bullets.
- ·
The coldest places on earth like parts of
Northern Canada, Alaska and Greenland have recorded temperatures in the minus
60 °C range while recently minus 90 °C was recorded in a research station in
the Antarctic.
- ·
We import LNG (Liquefied Natural Gas) which is
kept below minus 163 °C
- ·
Oxygen liquefies at minus 183 °C
- ·
Nitrogen and Air liquefy at minus 196 °C
- ·
Hydrogen liquefies at minus 253 °C
- ·
Helium at minus 269 °C
- ·
Minus 273 °C is called the Absolute Zero and
according to modern physics atoms and molecules cease their incessant motion
and almost stand still.
Gases reduce in volume enormously on liquefaction.Hence the
preferred way to transport them in a vessel is in the liquefied state; be it
Natural Gas, Oxygen, Nitrogen or Hydrogen. Liquid Oxygen and liquid Hydrogen
provide the best combination to burn in outer space and get the biggest kick
for the rocket to propel forward, what is called Specific Impulse in rocket
scientists jargon (see box Space Jargon
Explained ). However as it has been dramatically picturised in many
Hollywood fantasies like “Terminator” sequels, Batman and Superman sequels,
most things living and non-living including the toughest metals become brittle
at these extreme cold temperatures and can be pounded to powder easily.
Creating materials that can be engineered into machinery to
withstand and reliably operate at these temperatures is a challenge to modern
Material Scientists. The problem is further compounded in rocketry when the
liquid Oxygen and Hydrogen kept at minus 250 °C
in the fuel tanks then come down through pumps and valves and burn in
another part of the engine called the combustion chamber producing extremely
high 3000 °C where most materials
themselves would melt away !
That is why a nation mastering Cryogenic Rocketry is highly
respected in the technological world.No wonder the number so far was only five;
US, Europe, Russia, China and Japan. On Jan 5, 2014 the sixth kid on the block;
India, joined the exclusive club.
However the road to success has not been smooth. ISRO
started working on a 1 ton Cryogenic engine way back in 1982 to become familiar
with the basics. Then a serious attempt to leap frog by buying Russian
Cryogenic technology after the collapse of the Soviet Union and when it was in
financially dire straits, was done in the early 90’s. However US brought
pressure on Russia not transfer the Cryogenic technology to India citing
violation of MTCR (Missile Technology Control Regime). Obviously it was a US
show of raw power against the weakened Russia and the “nonaligned” India,
because no country uses Cryogenic engine in any missile whatsoever for the
simple reason that it takes a lot of time to prepare the rocket for launch and
then it takes a complex process taking even longer to restore the rocket if the
launch is aborted. It was clear that India was still being punished by
sanctions imposed after the 1974 Pokharan nuclear test and for not being an
enthusiastic supporter of the Gulf War launched by US against Iraq after the
collapse of the bipolar world in 1990-91. Yeltsins’s Russia was too weak to
resist this blatant arm twisting and rescinded from the agreement and instead made
a deal to sell 6 cryogenic stages to India without transferring the technology.
India then had to restart its own R&D and ISRO took up the design of a 12.5
ton Cryogenic stage for the new GSLV in 1994.
Radhakrishnan explained the tortuous journey littered with
disappointments, which finally succeeded on Jan 5, 2014 after going through
several rigorous reviews analyzing the failures and corrective measures and
redesign.
“GSLV Mark III would
have ingested the lessons from the learning curve of GSLV” says a confident Dr
K Radhakrishnan, Chairman ISRO
“When it comes to Cryo because we are
operating at very low temperatures, simple handling of the fluids and providing
all the plumbing at those temps is the first problem. Secondly the materials
that we use should have their properties in tact both at those low temperatures
and also at high temperatures of combustion. Third there are rotating parts at
least three major ones: fuel booster turbo pump; oxidizer booster turbo pump
and the main turbo pump. These pumps operate at speeds like 30-40 k rpm. One
needs to have bearings, seals of these pumps working at those extremes of temp.
The control components which we use like sealants, valves should also work
there. In the GSLV design we used the staged combustion cycle, where we get
slightly higher Specific Impulse but the system is far more complex. For
testing we should have the entire system. There is no modular testing and there
is no restart.”
Radhakrishnan added, “In GSLV Cryo engine there are four
ignitions to take place. Once we give a command the booster pump actions have
to start and 4 ignitions have to be maintained. All four have to be ensured in
a sequence in the first 3 secs. The temperature and pressure conditions at that
point in upper space with near vacuum conditions are crucial for 4 ignitions to
take place. That is the complexity.We had to set up the special test facility
in Mahendragiri and fabricate the engine, turbo pumps etc and the industry had
to be brought in and handheld from the beginning.”
“In 2003 the engine was qualified, where we did several
tests for several seconds and we got the performance we needed. This was engine
testing. After that we started testing the stage which includes fuel tanks and
all other paraphernalia along with the engine, in 2007. The flight stage was
prepared and tested in 2010 April on GSLV D-3. However ignition did not sustain
beyond 800 milli secs. The fuel booster turbo pump just stopped. We had a
detailed analysis for the failure that took place in vacuum conditions.”
Why did the fuel booster turbo pump stop? Had it worked are
we sure the rest would have worked? This ignition is taking place in vacuum how
are we sure that in those conditions the mixture will be correct were the
doubts that started plaguing ISRO after this failure.
“We generated all the scenarios and 2-3 points came out very
clearly. We had not tested this pump in Cryo conditions. When we use dissimilar
materials in a welded joint the contraction will be different in them. There
are three bearings in that pump where the tolerances may not have been
sufficient to take in the dissimilar contractions. So we revisited all those
tolerances. The second possibility of stoppage was a casing that could have
separated as a weld yielded. So we redesigned it. Third was the possibility of
a contaminant, a speck of corroded material somewhere coming into the fuel that
could have led to stoppage.We were setting up a high altitude test facility for
the next generation GSLV Mark III. We decided to use it for this engine. That
was a cardinal decision that we took in 2012 February. In 2013 March-April we
conducted two tests in high altitude conditions in a given sequence and this
gave us confidence. Then we committed for the flight” explained Radhakrishnan.
In August 2013 GSLV flight was scheduled then minutes before
launching, ISRO found a heavy leak of liquid fuel UH 25. In the late 90s Ariane had
the same problem due to corrosion of the Aluminum alloy used for the tanks and ISRO
had also found the problem in 2002 and it started using another slightly heavier
alloy which does not have this problem. However the transition to new alloy had
to take place in a phased manner. As if Murphy’s law was clearly operating lo
and behold, and the last old tank was used in that flight which gave ISRO the
problem.
The restoration after aborting the flight was another major
issue. Nearly 450 people worked for a week to save the cryogenic stage, the
satellite etc. “We had to drain nearly 350 tons of toxic propellants like UH-25
without causing pollution and disarm all the pyro devices. Remove all the 36 hoses
of Cryo engine and so on. The vehicle was brought back and destacked. The
second stage and L-40 had to be redone. It was more than defusing a bomb”, says
Radhakrishnan with a lot of pride in his team.
Thus the ground was laid for the success of GSLV D-5. ISRO
is now confident of testing this vehicle further in a couple of more
development flights and also developing the next generation GSLV Mark III which
will be begin its flights tests in 2014.
Recognising the potential of space technology for
developmental and societal purposes in a developing country like India was the contribution of Sarabhai. The program started very modestly with a little help from
the French and the Americans in terms of a few sounding rockets and weather
balloons to study various phenomena in the upper atmosphere. In the archives of
ISRO there exists by-now-famous photograph of a rocket being brought to the
launch pad in Thumba on the back of the bicycle.
After his premature death, a quintessentially professorial
Satish Dhawan shouldered the responsibility to drive this program. And lo and
behold with Mrs Gandhi’s quiet backing as Prime Minister and Dhawan’s
leadership ISRO started designing satellites and launching them courtesy the
Russians and the French and even the Americans (in the pre-Pokharan world, of
course!). Simultaneously a vigorous program was taken up to develop the launch
vehicles. Vasant Gowarikar, Abdul Kalam etc toiled to make a success of the solid
fueled rocketry. The strategic implications of the technology were very clear
and Mrs Gandhi moved Kalam to the newly formed Integrated Guided Missile
Program of DRDO that eventually led to Prithvi and Agni.
Meanwhile the liquid
engine technology offered by the French was diligently pursued till India
attained mastery of it and developed its Vikas engine surprising their French
Gurus too. Together the solid and liquid fueled rocketry led to the design and
success of PSLV which has been the work horse of ISRO in the last two decades.
The current hard earned success of GSLV takes ISRO’s capabilities to the next
level. “We have learnt our lessons from GSLV and the next generation GSLV Mark
III which will really mark India emerging as a major space technology power with
its own heavy launch capability would have ingested all the lessons from the
learning curve. No doubt other countries like US, Russia, EU and China have
developed even heavier Cryo stages but GSLV Mark III suits our plans just fine
and we are not in any megalomaniacal race with anyone” says a quietly confident
Radhakrishnan.
The success of GSLV has been a fitting tribute in the Golden
Jubilee year of Indian space program that started in 1963 in Thumba, a fishing
village near Tiruvananthapuram, Kerala and we hope to see more technological
and commercial successes from this jewel among government funded R&D in
India.
END