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.