The Grand Ol' Ride

The Polar Satellite Launch Vehicle, or the PSLV to you and me, is an interesting piece of machinery. It's significance, utility and the tremendous service that it has rendered so far to the Indian space programme has been taken for granted, purely due to its near-impeccable record. So much so that a failed launch of a PSLV would garner more attention than its past successes, but then that, I believe is the way our heroes are always treated. 

With the journey of Mangalyaan close to being initiated (the slated date of launch being October 28, 2013) and the PSLV yet again acting as the ferrying service to the hitch-hiking orbiter, it would pay to glance over the life and times of the highly functional and widely respected PSLV...

A slingshot into space

The PSLV is basically an expendable launch vehicle (ELV), which means that it is operated on a use-and-throw basis in each launch. Typically it consists of more than one component, aka stages, which drop off one by one to the earth after being launched, except the last stage, which catapults the hitch-hiker, aka the payload, into its orbit around the earth. The other kind is the Reusable Launch Vehicle (RLV), almost of the kind that NASA used to maintain till 2011 in the form of its Space Shuttle fleet (comprising of four orbiters Enterprise, Columbus, Challenger, Discovery and Atlantis). These Shuttles consisted of three components - the orbiter vehicle (OV) which carried the payload, the external tank (ET) and the solid rocket boosters (SRB)- of which two, viz. the OV and the SRB return to the good earth, and after some polishing-up, could be reused for subsequent flights. 

So what is this ride made of ?

Plenty of parts, it seems; the most basic components being the several stages of rockets and a set of SRB. Now let us remember that a rocket is just a vehicle, with a potent mixture of fuel/propellants splashing inside it, which when ignited, belch a massive exhaust backwards/downwards. The exhaust, in full deference to Newton's Third Law of Motion, pitches the vehicle forward/upward. This is the guiding principal of each of the four rocket stages used in the PSLV. 

Speaking of propellants, they are of five kinds: Solid, liquid, gaseous, hybrid and gels. The PSLV use only the solid and liquid kind, so we shall temporarily forget about the other three varieties. Both solid and liquid propellants are basically one big mixture of oxidising (one that yields oxygen) agents and reducing agents (the fuel which starts crackling when it meets the oxygen), the difference being only in their respective states of existence. The underlying principle is that of the good old combustion: the oxidising agent meets the reducing agent, and a merry bonfire erupts, only a few thousand times stronger than the one in your backyard.

So every PSLV comprises of four stages: PS1 to PS4. A brief summarisation of each stage is as given below:

Source: www.isro.org
Figures indicate values averaged over the respective number of successful launches, based on publicly available information with ISRO

SOM (or PSOM) stands for Strap-on Motors,which is another way of addressing the SRB. The PSLV is armed with 6 PSOM, four of which are fired on the ground and two are air lit.
The PSLV has completed 22 successful flights, in addition to the first ever launch of the PSLV D1 which filed 700 seconds into its flight, while another launch was at best only a partial failure as in the satellite was launched, albeit at a different orbit than previously decided. As the table indicates, ISRO currently uses three variants of the PSLV: the Regular (which is just called the PSLV), the Core-Alone (CA) configuration and the PSLV-XL. The initial launches of ISRO have all been made through the Regular PSLV, which has been comprises all the four rocket stages and the additional PSOM.
The typical PSLV stands nearly 44 meters tall, and has a liftoff mass of 295 tonnes, with a capability to carry payloads of about 1678 kilogrammes to a 622 kilometres sun-synchronous orbit (viz. this orbit has a particular altitude and inclination to it, so that the satellite passes over the same point on the earth at approximately the same local time daily.
The CA configuration, as the name suggests, is the bare rocket stages, with no add-ons. It weighs around 230 tonnes and is currently designed to catapult a 1100 kilogramme payload into a 622 kilometres sun-synchronous orbit.
What we should actually focus on, is the PSLV-XL. The first time this juggernaut of a vehicle was used (in the form of PSLV C-11) happened to be that historic day of October 22, 2008, when the Chandrayaan - I was launched towards our only natural satellite. This brute is 44.4 metres tall and has a lift-off mass of 320 tonnes. Though the first stage, which was taller by 0.20 metres for C11, holds the same mass of propellants as the other variants, each of the six,extended and more powerful  PSOM carry 12 tonnes of the solid propellant (as compared to only 9 tonnes in the other variants), capable of producing a maximum thrust of 720 kilonewtons. The fourth stage of the launch vehicle with a twin-engine model, is powered by 2.5 tonnes of liquid propellant. The PSLV-XL is capable of launching payloads as heavy as 1800 kilogrammes. The C11 had launched the 1380 kilogramme moon orbiter and impactor in the 2008. Chandrayaan mission. Subsequent PSLV-XL have been used to launch progressively heavier payloads upto 1850 kilogrammes.

The PSLV C-11 at the Vehicle Assembly Building
Image: Courtesy ISRO

PSLV C-11 liftoff
Image: Courtesy ISRO

Needless to say, there are sceptics all over the place, writing off this mission even before it has begun, but Mangalyaan, if successful, would be a tremendous boost to the Indian Space Programme. More than anything else, it would be a nod to the strides that are being taken in the field of science, which frankly, hasn't been quite something to boast about. It is no doubt going to be a momentous step for ISRO, and one of the numerous components this mission depends on is this particular vehicle, which has had quite an enviable reputation. The 'wokhorse' of ISRO is still, proudly, in service. 

Sources: www.isro.org/www.spaceflight101.com/www.nasa.gov
Images courtesy ISRO

A rocket from the church...

Call it humble beginnings. That is how our Indian space programme was born. To put everything into a proper perspective, let me lay the ground first...

India's interest in the atmosphere and its microscopic innards can be definitively traced back to the 1920s, when, still under the British domination and buffeted by strong scepticism from his Western counterparts , physicist Shishirkumar Mitra took a fancy to all things wireless, and made landmark discoveries about the presence of the C and E layers of the ionosphere. While the occasional genius of Sir C.V. Raman (with whom Shishirkumar Mitra often collaborated) and Meghnad Saha continued to make ripples in the scientific domain, which was still swelling with pride over the achievements of it unsung heroes Jagadish Chandra Bose, Prafulla Chandra Ray and Srinivasa Ramanujan, it was really the twilight of Indian science. The brutal First World War had left little time or resources to explore things which existed above the ground, and while Great Britain reeled under the massive losses, both financial and human, space science as a symbol of national pride began crumbling. In India meanwhile, the long due nationalist movement was well underway, pushing science into a category of expendable luxury. 

After nearly two decades of unintentional neglect, it wasn't before 1945, that space research began in earnest under the stewardship of Vikram Sarabhai and Homi Jehangir Bhabha.  By this time, the National Aeronautics and Space Administration (NASA) of the USA had already successfully launched the V2 rocket (basically a short-range ballistic missile developed during the WW II in Germany and sporting a dubious/notorious history; this one has the credit of being the first man-made contraption to breach into  space), snapped photos of the Earth from without and were on the verge of sending fruit-flies (yes,fruit-flies) and monkeys into space, to test its habitability.  In 1957, the erstwhile Russia gloriously launched the 184 pound Sputnik into a 560-mile high orbit above the Earth and the space-race was thus tacitly flagged off. The rest, as we know it, is history.

Having a ball in space: The Welch Daily News reporting the successful launch of the Sputnik 1
(Image courtesy of www.coalwoodwestvirginia.com)

In 1962, the Indian National Committee for Space Research (INCOSPAR) was set up as the means to formally inaugurate India's space research programme. Shortly after the Sputnik launch, the United Nations proactively constituted the Committee on the Peaceful Uses of Outer Space, and passed resolutions recommending the launch of sounding rockets to explore the intricacies of the atmosphere. 'Sounding' is a nautical term, meaning to take measurements. These projects would be UN-sponsored, and focussed on the equatorial regions and the Southern hemisphere. This was the moment INCOSPAR had been waiting for all along. NASA provided the Nike-Apache rocket. It was the most popular sounding rocket used by NASA between 1960 to 1964: a two-stage, solid propellant vehicle, with a Nike booster and an Apache upper stage. A group of Indian scientists were sent to be trained at the Langley Research Centre, Goddard Space Flight Centre and Wallops Island Facility in USA. The six(?)scientists (A.P.J. Abdul Kalam was one of them !), all in their twenties, were trained to assemble imported rockets, launch and track them and handle data acquisition. This was essentially a case of partial technology transfer, as there were no lessons into building an actual, operational rocket. 

When the scientists returned home, the next roadblock was to find a suitable launch site. The site had to be close to the magnetic equator and strategically close to the sea to deal with the re-entry phases of the rockets. Additionally, the place would have to be accessible and as far as possible from the densely populated areas. After extensive scouting, the fishing villages of Thumba and Pallithura in Kerala seemed to fit the bill. 

Thumba's location at 8°32’34”N and 76°51’32”E, just shy of the the magnetic equator was deemed ideal for low-altitude, upper atmosphere and ionosphere studies. Rockets launched from this site could be used to probe numerous delicate phenomena, such as the electrojet, associated with the magnetic equator. But the lure of science apart, getting the land inducted for something as untested as space research was predictably, a tough business. 

Thumba was a tiny fishing village on the Malabar coast comprising of a few hundred thatched huts. It had gradually risen to fame with the mystique of St. Mary Magdalene's Church. In 1544, St. Francis Xavier constructed the thatched roofed St. Bartholomew church on the seaside. In time the structure was expanded and solidified in stone. In the 1900s, the local fishermen, most of whom were Christians, sighted a beautiful, sandalwood statue of Mary Magdalene on the beach. The statue was blessed and consecrated in the church and St. Bartholomew's was henceforward known as St. Mary Magdalene Church. Soon after, a long wooden log was washed ashore, which was carved into a flag mast and erected in front of the church. 

Given the religious inclination of the village, and the general headache associated with acquiring land in India, getting the project to move forward was becoming a tall order. No other site seemed to meet INCOSPAR's requirements, and it was with some trepidation that the officials proceeded to talk the villagers into sacrificing their holy plot. To gather the site, INCOSPAR was granted no more than 100 days. 

Predictably, the initial discussions did not go well. The villagers saw little sense in handing over their land and the church for the development of science. As compensation, INCOSPAR offered to build another identical church but headbutting religious beliefs has never been the best way out. Though I have found no records of how our scientists actually managed to talk the adamant occupants into it, but much has been credited to the then District Collector K. Madhavan Nair and the Right Reverend Dr. Peter Bernard Pereira, who ultimately permitted the transfer of the sacred church and its estates to what was later institutionalised as the Thumba Equatorial Rocket Launching Station (TERLS). And thus began India's space programme, as affectionately termed by one of our dailies (Jaimon Joseph, CNN-IBN, September 9, 2012), as having been born in a cow-shed !

Bishop's house/workshop

Records have it that the newly constructed rocket launching pad was situated on the beach, in the midst of a clearing in a coconut grove; the church was the main office building for the scientists and several 'generations of pigeons' according to R. Aravumudan; a cow-shed and a cattle feed store was given over to furnish the laboratories,where the young scientists started work on the rocket. The bishop's office functioned as a workshop. Legend has it that the young group of scientists travelled everyday from Thiruvananthapuram, the nearest city, by bus, subsisting on lunch bought off the railway station. 

Boys' toys: A.P.J. Abdul Kalam (left) and R. Aravumudan assembling a rocket

Static test stand at Thumba; more like a beach resort !

With the launch date approaching, there was concern brewing over the delay in the delivery of the payload: a sodium vapour experiment set-up from France's Center Nationale d'etudes Spatiales (CNES). It was a simple enough structure, basically a box filled with sodium, which would simple ignite, leaving a sodium trail that was required to be photographed and analysed. When the payload did arrive though, there was more trouble. The French payload would not fit into the American rocket and hence required an additional welding, something that the Indian scientists were wary of, considering the pyrotechnic nature of the payload. Finally, the scientists decided to scrape the payload with a hand tool, so it could mate successfully with the rocket ! 

November 21, 1963 dawned with clear skies. A bicycle carrying a cone-shaped device wobbled into the beach. Nobody must have batted an eyelid as this was common fare in the sprawling campus of Thumba. With bare minimum facilities in the form of a single jeep and a solitary manually operated hydraulic crane, bullock carts would often ferry rocket parts from one point to another. 

Hold tight, bump ahead !

The scientists got down to business. When time came for the rocket to be placed on the launcher, the crane developed a leak, and the ~700 kilogramme contraption was lifted manually. Soon after, however, the Nike Apache was launched successfully as it tore through the skies. The twilight sky shone with the orange trail. The Kerala Legislative Assembly was apparently adjourned for a few minutes to let the members witness this rare spectacle. The rocket climbed to an altitude of 208 kilometres and releases a trail of sodium vapours in the sky....

Into the glorious sunset !
(Images courtesy of ISRO)

Thumba inspired a whole generation of the scientifically inclined and has caught our fancy ever since. St. Mary Magdalene church, meanwhile has been converted into a museum, as Indian space research has launched more professionally through bigger and flashier facilities close by. But it remains in India's legacy and in the true spirit of the country where success has been traditionally cloaked in modesty, of how a small group of young, starry-eyed scientists dreamt of the wide beyond from the confines of a coconut grove in a little fishing village, and how they successfully lent the nation the promise of a brighter future...

Sources: 

www.isro.org/www.bhaskarastro.org/articles published by The Hindu dated December 2, 2002/www.nasa.gov/www.vigyanprasar.gov.in/www.iisc.ernet.in/www.spacechronology.com/www.astronautix.com/www.willylogan.com/thiruvananthapuramupdates.wordpress.com/'Reaching Out to the Stars' by T.S. Subramanian in The Hindu