Silver
Jubilee of SLV-3
Launch Celebrated
The
successful launch of India’s first Satellite Launch Vehicle (SLV-3)
on July 18, 1980, was a historic landmark for the Indian space programme.
The
maiden national launch vehicle effort, SLV-3, gave ISRO a remarkable
insight into the conceptualisation, design, development and management
of a technically complex multi-disciplinary project as the young team
was experimenting with and learning the nuances of launch vehicle
technology. SLV-3 weighed just about 17 tonne at lift off and was
able to launch
only about 40 kg spacecraft into Low Earth Orbit compared to the present
GSLV which has a lift-off weight of 414 tonne and capability to place
about 5 tonne satellite into low earth orbit.
Yet SLV-3 laid the very foundation for the future generation heavy
lift vehicles enabling the country to aspire for the moon today.
It
was indeed fitting and nostalgic that Dr A P J Abdul Kalam, the President
of India, who was the Project Director of SLV-3, participated in the
Silver Jubilee Celebrations on July 23, 2005,
to reminisce the SLV-3 and to look to the future of space transportation
through a Symposium on Launch Vehicle Development at Vikram Sarabhai
Space Centre, Thiruvananthapuram, the
lead Centre of ISRO for launch vehicle technology, along with Astronautical
Society of India.
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From
right–Mr. G Madhavan Nair, Chairman, ISRO, His Excellency
Dr. A P J Abdul Kalam, President of India, Mr. Oommen Chandy,
Chief Minister, Kerala and Dr. B N Suresh, Director, VSSC
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To mark
the Silver Jubilee of SLV-3, Space India reproduces below an article
on SLV-3 authored by S/Shri A P J Abdul Kalam, E Janardhana
and D Narayana Moorthi, which had been published immediately following
the successful launch of SLV-3 in “the university herald”
the quarterly publication of the University of Kerala (July 1980).
The
Indian Satellite Launch Vehicle – SLV-3
A P J ABDUL KALAM, E JANARDHANA & D NARAYANAMOORTHI
1.
Introduction
Dr Vikram Sarabhai pioneered the space efforts in India at the picturesque
little Thumba near Trivandrum in 1963 with a small team of engineers
and scientists. This enthusiastic group who laid firmly the strong
foundation of this advanced technology in the country, firmly believed
that Space Science and Technology would, in due course, immensely
assist a developing nation like India in the field of mass education,
communication, meteorology, remote sensing and thereby uplift the
standard of our life. This line of thinking has been the main thrust
of all the major space programmes in India.
2.
Sounding Rockets
It was tense drama, anxiety and excitement
when the first sounding rocket was shot up from Indian soil in 1963.
Just four years there
after announcement could be made of the launching of our own maiden
sounding rocket-75 mm dia with 10 kg propellant. With this modest
beginning, we have today a series of sounding rockets ranging in diameter
from 75 mm to 560 mm, catering to maximum payload weights of 100 kg
and altitudes varying from 15 to 350 km.
3.
Satellite Launch Vehicle
Next logical corollary to Sounding rockets, was the development of
a satellite launch vehicle. Realisation of the launch vehicle is a
sophisticated technology by itself and the related infrastructure
was required to be built in the areas of propellant, propulsion, avionics,
materials, motor testing, vehicle assembly, vehicle checkout and ground
telemetry/tracking. ISRO establishments in the country (fig.1) were
geared to these mammoth efforts through time bound projects. Vikram
Sarabhai Space Centre (VSSC) is responsible for launch vehicle design,
development and management. Sriharikota is a launch base. It also
houses propellant production and rocket motor test facilities, ISRO
Satellite Centre (ISAC) specialises in building spacecrafts. Space
Application Centre (SAC), Ahmedabad, has the primary task of applying
the space technology for the socio-economic benefit of the nation.
The launching of 35 kg Rohini Satellite by SLV-3 on 18th July’80
is a major “Leap into Space”. In the process India became
the sixth nation to have indigenous launch capability. The other countries
who have achieved this feat are, USSR, USA, France, China and Japan.
Rohini Satellite is the 3rd Indian Satellite in orbit. The earlier
ones, Aryabhatta and Bhaskara were launched from USSR.
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Fig 1. Establishments of the Department of
Space
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4.
Vehicle Description
SLV-3 is a four stage solid propulsive vehicle designed and developed
by VSSC. It has taken approximately seven years to realise the vehicle
from start. This vehicle with a lift off weight of
17 tonnes and total length of 22 meters can impart the required velocity
of 28000 km/hr to 35 kg satellite to inject the same into a low earth
elliptical orbit. SLV-3 consists of forty four major functional subsystems
which are indicated in the exploded view (fig. 2). The flight sequence
of the launch vehicle from lift off till orbital injection of satellite
is given in fig. 3.
The main constituents of the vehicle are:
- Vehicle propulsive system
- Rocket systems
- Guidance and control system
- Vehicle electronics.
4.1
Vehicle Propulsive System
This forms the main ‘muscle’ for achieving the required
altitude and velocity for orbital injection. The four stages are solid
propellant type. The first stage is of 1000 mm diameter and carries
8.6 tonnes of PBAN (Polybutadine Acrylo Nitrate) propellant developed
indigenously. The motor case fabricated from 15 CDV6 steel sheets
and forgings is in three longitudinal segments. Propellant is cast
separately in each segment and then joined together. The segmented
motor technology has been specifically developed for the first stage
motor. This motor develops an average thrust of 46 tonnes and burns
for 50 seconds. with a specific impulse value of 254 seconds (vacuum).
The second stage motor is of 800 mm diameter and carries 3 tonnes
of PBAN propellant in a single monolithic grain. This motor is also
made of 15 CDV6 steel sheets and forgings. The motor has an average
thrust of 20 tonnes and burns for 44 seconds and gives a specific
impulse of 268 seconds (vacuum). The third and fourth stage motors
use fibre reinforced plastic motor cases and high energy propellant
(HEF 20) developed inhouse. Third stage with a diameter of 800 mm
houses one tonne of propellant and gives an average thrust of 6.3
tonnes. Fourth stage has a diameter of 650 mm, carries 262 kg propellant
and provides a thrust of 2.4 tonnes. The specific impulse of fourth
stage is 284 seconds (vacuum). Numbers of tests have been carried
out both in scaled down size and in full scale to confirm the reliability
of performance of individual stage motors.
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Fig
2. Exploded view of SLV-3
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4.2
Rocket Systems
Rocket systems comprise stage separation systems, destruct system
and heat-shield.
The separation between the stages is carried out by initiating “Flexible
Linear Shaped Charge” (FLSC) system located between the stages
for the first two stages. Ball type separation system is employed
for third and fourth stages. Fibreglass honeycomb heatshield is provided
around satellite and fourth stage to protect them from aerodynamic
heating during atmospheric flight region. After the vehicle crosses
the dense atmosphere, the heat-shield is separated from the vehicle
at an altitude of about 85 km. Also FLSC type destruct systems are
housed in first three stages to destruct the vehicle based on ground
command in the event of vehicle deviating from specified flight path.
4.3
Guidance and Control System
Guidance and control system of the vehicle is responsible for
three axis stabilisation and for steering the vehicle along the preset
trajectory profile. The system mainly does three functions.
- Sense the inertial attitude of the vehicle.
- Generate suitable control function to actuate the control power
plants.
- Generate appropriate control forces to stabilise and steer the vehicle.
4.3.1
Guidance System
Four gimbal stabilised inertial platform is used to sense the
vehicle attitude. Autopilot compares attitudes with command angles
as given by pitch programme stored in vehicle attitude programmer
and with launch references for yaw and roll axes. The error signals
thus generated are mixed with vehicle body rates measured by rate
gyro package to generate command signals for control systems.
4.3.2
Control Systems
For the first stage, Secondary Injectant Thrust Vector Control system
(SITVC) in proportional mode has been employed (using strontium perchlorate
as injectant) for the first 17 seconds of flight, for pitch and yaw
control. For roll control throughout and pitch and yaw control beyond
17 seconds electrohydraulically operated aerodynamic control surfaces
(fin tip control) are used. For the second stage, bipropellant on-off
reaction control power plant (using RFNA and hydrazine) is used for
pitch, yaw and roll control, both in power and coast phase. The third
stage has monopropellant on-off reaction control system (using hydrazine
and indigenously developed catalyst), to generate control forces required
during third stage flight regime.
The
fourth stage is spin stabilised. SITVC control system has been evaluated
in the static test of first stage motor. Second and third stage control
systems have undergone a number of system level ground tests. In addition
to computer simulation, the total guidance and control chain has also
been tested in the hardware in the loop simulation checks.
4.4
Vehicle Electronics
The telemetry, telecommand, tracking and sequencing system constitute
the vehicle
electronics systems.
During
flight the health and performance of vehicle systems are monitored
by telemetry system. This employs two schemes – one FM/FM and
the other PCM/FM – accommodating about 400 vehicle parameters
like motor pressures, temperature, guidance commands, attitude errors.
Onboard tracking subsystem includes C-band transponder and tone range
receiver. Vehicle
sequencer generates actuation commands for stage ignition, separation
and control system gain change. Redundant telecommand receivers are
provided onboard to execute ground commands for destruction, if required.
The
equipment bay – the brain of the vehicle housing most of the
guidance and electronic subsystems is located just above third stage.
4.5
The stages are interconnected by aluminium alloy interstage housing
instruments, control system and separation system.
5.
Mission Software
Major strides have been made in this field during the course of
SLV-3 development. They include trajectory studies, heat transfer
analysis, control system design/analysis, structural design, rocket
motor design, separation disturbance studies error analysis, digital/hybrid/hardware
in loop simulation, checkout software, range safety studies, orbit
studies, visibility calculation, post flight software and several
others.
6.
Support from Industries and Academic Institutions
Apart from various units, a number of institutions and industries
have participated in SLV-3 programme. Institutions like ADE, DLRL,
GTRE, IITs, IISc, NAL have contributed towards hybrid simulation studies,
antenna testing, heatshield evaluation tests, heat transfer studies
and wind tunnel testing. Major industries like WIL, Poona, L &
T, Bombay, HAL (Kanpur, Bangalore, Nasik, Lucknow and Koraput), R
& C, Bombay; BHPV, Vizag; HSL; Rourkela; RFC, Hyderabad; Anup,
Ahmedabad and HMT, Kalamassery have played major roles in fabrication
of components like motor cases, interstages, launcher, etc. A number
of small scale industries, specifically in and around Trivandrum have
remarkable contributions towards SLV-3 programme.
7.
Rohini Satellite (RS-1)
SLV-3 flight on July 18, 1980 carried an experimental satellite
(RS-1) instrumented to monitor the performance of the fourth stage
motor and satellite in orbit. It carried with it, magnetic aspect
sensor, velocity encoder, pulse code modulation, telemetry and solar
panels including indigenously developed solar cells.
8.
Integration and Checkout
8.1 At Thumba
The integration of nearly one lakh individual parts of the vehicle
into components, subsystems, subassemblies, stages and vehicle is
an arduous task, spanning over more than a year. The four rocket motors
are processed at VSSC/SHAR. The other eight interstage subassemblies
housing control systems, equipment bay, separation system, electronic
monitoring/interface circuits are integrated and checked out at Vehicle
Integration Laboratory/Electronic Checkout Laboratory, VSSC, before
being transported to SHAR. The checkout process, conceived in four
phases, is carried out for components, individual subassemblies, electrically
interfaced stages and fully integrated vehicle.
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Fig
3. SLV-3-E-02 Trajectory
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The
computerised checkout system for the above is also developed at VSSC.
This has been built around two small computers and individual test
sets for powering various onboard subsystems, checkout, simulation
of signals and monitoring.
Satellite,
which is built at ISAC, Bangalore, is brought to Trivandrum, checked
for its electrical/mechanical compatibility with vehicle, dynamically
balanced and then taken to SHAR.
8.2
Launch Campaign at SHAR
The various subassemblies and rocket motors are brought to SLV-3
Complex which consists of a Vehicle Integration Building, Block House,
Launcher and other facilities such as pneumatic sources. During this
period, commonly known as launch campaign, the vehicle is built up
in stages, with a concurrently running checkout from Block House.
Block House is nearly midway between vehicle integration building
and launcher and connected with them through 1000 lines of checkout
cable. After integration and checkout of the vehicle at integration
building, it moves to launch pad. The final count down of the vehicle,
in conjunction with ground stations spans over more than 23 hrs, preceded
by a rehearsal. The last 11 minutes of operations are entirely taken
over by checkout computer at Block House. Nearly 600 parameters are
checked during this phase and the computer clamps down a hold if the
monitored parameters do not fall within
set limits.
9.
SLV-3 mission
For a successful completion of SLV-3 launch, a close coordination
among elements of the mission viz., vehicle, satellite, ground stations,
tracking networks and mission software, is essential. The ground stations
at SHAR include telemetry receiving station, telecommand transmitter,
tone range interferometer system, radars (medium and long range -
a total of
three numbers), real time system employing IRIS 55 computers, closed
circuit TV network and photography. The mission control during the
final phase is done from control centre where real time information
on vehicle performance is displayed. Range safety decision, if needed,
is also taken from control centre. The ground stations have been checked
out as integrated system during sounding rocket flights and special
aircraft sorties. They are also used in vehicle check out during launch
campaign.
The
tracking network includes the telemetry tone range interferometer
stations at SHAR, telemetry tone range, S-band tracking systems at
Car Nicobar and Telemetry receiving stations at Trivandrum and Ahmedabad.
10.
Project Management
In addition to the technology development, production, integration
and launching of SLV, the programme has been a landmark for developing
a planning and management methodology itself.
SLV-3 is a unique combination of multi-disciplines functional areas
such as aerodynamics, structure, propulsion, control system, guidance,
electronics, materials, quality assurance and each area has a gamut
of functions varying from design, development, facility establishment,
production and operation. Added to this are the critical – time
bound nature of the programme, stringent resources, conflicting decision
situations. A management methodology enveloping all these constraints
had to be evolved, the highlights of which have been:
- a matrix type of management structure
- a thorough design review methodology
- configuration and weight control
- a closed loop failure safe mechanism involving on-line quality control,
waiver boards, tests and
evaluation, quality assurance teams
- Flight, mission readiness review
- Periodical review meetings
- PERT scheduling
- Budget control.
11.
Future Goals
The successful performance of SLV-3 giving the required velocity
for the orbital injection of Rohini Satellite, is the forerunner of
the ‘India’s major space programme’ ahead. Heavier
application satellites in low-earth orbits as well as in geosynchronous
orbit are to be launched to derive the full benefit of the technology
to our nation. The “Satellite Instructional Television Experiment
(SITE)” programmes carried out by ISRO during 1976-77, using
an American ATS-6 (Application Technology Satellite) for a period
of one year is good demonstration as to how the space technology can
improve the life style of people in remote areas by way of education,
and by flow of information regarding agriculture, hygiene and health
problems, and also how the national integration process can be accelerated.
In addition, launching of remote sensing satellites would help faster
survey of our national agriculture, mineral and forest resources.
Weather forecasting is a boon to the agriculturist. The technology
infrastructure and management methodology developed within the country,
in the process of making SLV-3 is very valuable to proceed confidently
to build larger launch vehicles of the future to put application satellites
of larger size, both in low earth orbit and in synchronous orbits.
Ten years profile projected for ISRO, Department of Space, for the
development of larger launch vehicles and satellites is on the anvil
and expected to be carried out by improving and adding on the base
created by SLV-3. India is poised for having a launch vehicle capability
of putting 600 kg class spacecraft in 1000 km sun-synchronous orbit.
“Well,
it is time for starting countdown to go upward from the Sixth Nation
Classification.”
Note:
ADE
- Aeronautical Development Establishment, Bangalore
DLRL - Defence Electronic Research Laboratory, Bangalore
GTRE - Gas Turbine Research Establishment, Bangalore
NAL - National Aeronautical Laboratory, Bangalore
WIL - Walchand Nagar Industries Limited, Poona
R & C - Richardson & Cruddas, Bombay
BHPV - Bharat Heavy Plates and Vessels Limited, Vishakapatanam
HSL - Hindustan Steel Limited, Roorkela
RFC - Republic Forge Company, Hyderabad
