REPORT ON INDUSTRIAL VISIT TO ISRO

 

The following is the report on the industrial visit to the SDSC, SHAR (Satish Dhawan Space Centre, Sriharikota Range), on the 18^th of February, 2009. There were a total of 65 students, 3 Staff members and 2 others.

 

The journey commenced at around 6.15 am from Kodambakkam. There were two buses and the students were seated comfortably. The bus stopped at Red Hills at around 7.30 for breakfast. We reached SDSC SHAR at around 9 am and after several security checks and administrative formalities, we were taken to a central building. In this place, we were shown a video – ‘Gateway to Space’ - on the ISRO, its history, and the current facilities available. After the video, questions were fielded to the official, and they were answered with ease.

 

THE ‘GATEWAY TO SPACE’ VIDEO

 

The GSLV and PSLV are the two launch vehicles used currently by ISRO to launch satellites into the geo synchronous and polar orbits respectively. The GSLV has 3 stages – the first is a solid (fuel) stage, the second a liquid (fuel) stage and the third is a cryogenic stage. The satellites launched so far have applications such as National development/infrastructure, telecom, disaster warnings, resource management, etc.

The PSLV can launch multiple satellites simultaneously at a low cost and high reliability. The various facilities at SDSC were listed and their functions explained in brief. Weather prediction is another important factor at the time of launch, and the SHAR boasts of this facility too. The latest addition to the SDSC was the S200 propellant plant.

 

The following technical details were given:

The strap on motors, their dimensions and use were elucidated.

The countdown begins at (t-57) hours. At this time, the liquid propellants are filled into the system. At (t-16) hours, the mobile service car is withdrawn and the system is connected to the Launch and Mission control centre (which are placed 6km from the launch site) through electrical wires only. The cryogenic fuel is set around the launch site. The mission director and other senior scientists assemble at the Mission Control Centre. The computer networks do the complex calculations, and other details like mission safety are all displayed. At (t-6) seconds, the strap on motors ignite, and the solid boosters ignite next at t=0.  The performance is monitored in real time. High precision radars are used to track the vehicle right from lift off to satellite injection. Such radars are present in Port Blair, Mauritius, and Indonesia for real time monitoring. At about 17 minutes after blast off, the GSLV completes the mission – puts the satellite in geosynchronous orbit. The following map shows the direction of launch of various types of launch vehicles.

 

The Sriharikota Range has been chosen for its proximity to the equator and to use the rotation of the earth. It is close to Lake Pulikat and is about 100 km north of Chennai and close to the Bay of Bengal.

 

 

Questions and Answers (extension of the ‘Gateway to Space’ video)

 

1.    What is LEO?

A: Low earth orbit, at 350-400km from earth’s surface.

 

2.    What is the difference between Liquid and Solid propellants?

A:  Liquid propellants have higher efficiency, but lesser thrust, while solid propellants have lesser efficiency but greater thrust.

 

3.    What can be the possible reasons for failure of launch?

A: Poor workmanship is the root of all failures of launch.

 

4.    What are the factors which are used to decide the location of a space centre?

A:  Proximity to equator, closer to water sources, lesser population (in case of untoward incident) are the main factors. Ideally, the equator will be best spot for launch of a satellite because it offers the shortest path. Also, the east coast is best suited to take advantage of earth’s rotation.

 

5.    What are the similarities and differences between GSLV and PSLV satellites?

A: Both the vehicles have similar electronics and same first and second stages. The PSLV has a maximum payload of about 1500kg and the orbit is at 800/900km. It has a third stage of solid propellant and fourth stage of liquid propellant. It has a propulsion system of 6 liquid propellant starters.

The GSLV has a maximum payload of about 2000kgs. It has a third cryogenic stage for better performance and has no fourth stage. It has 4 liquid propellant starters.

 

6.    What about the disposal of satellites after their lifetime?

A: Low earth orbit satellites decay by themselves after their lifetime. They enter the earth’s atmosphere and are burnt by friction. Geosynchronous satellites have reserve propellants which are used to push them out into deep space. Also, the retrieval of satellites which are damaged prematurely is being researched.

 

 

After this, we were taken to several locations within the SDSC, with a guide to explain the locations.

 

 

MISSION CONTROL CENTRE

 

After another round of security checks, we were taken to the Mission Control centre. We were seated in the visitor’s box where the VVIPs are seated during launches.

Here, we were told about the history and geographical features of SHAR. The SHAR was renamed SDSC after former ISRO chairman Prof. Satish Dhawan on the 5^th of September, 2002. The range is about 175 sq. km in area and has a coastline of 60km.

 

The mission control is the focal point of the controlling the vehicle. There are 8 ‘hold buttons’ at different places around the range. In case of abnormalities in subsystems (affecting the health of the rocket), the hold button is used to terminate the countdown. In case the abnormality has been resolved, the vehicle director can arrange to resume the countdown.

 

The mission control centre has several rows of computers. The first row is used to supervise the control of the launch vehicle. This is the position of the directors and the chairman. The vehicle director is also seated with the other senior scientists. The second and third rows control the operations on the vehicle. Various chiefs of operations are seated in these rows. These computers are connected by Ethernet and fibre optics.

 

There is a separate ring safety server which is controlled by a senior scientist. In case of abnormalities in the path of the rocket, this person can detonate the rocket so that the rocket is blown up over the sea and does not affect neighbouring human population. There are 45 levels of information relating to the launch of the rocket. The supervisory row (first row) receives this information on multi-channel CCTVs. Also, 8 channel intercoms are available for voice communication.

 

The vehicle Director authorises the launch at (t-16) minutes. An automatic sequence program checks the health of the rocket(with respect to various parameters) and ensures that any deviations in the parameters are within specific limits.

 

 

ISRO TELEMETRY, TRACKING AND COMMAND NETWORK (ISTRAC) SHAR GROUND STATION

Various animations related to the tracking rockets and the orbiting of  satellites were shown. There was another animation of the Chandrayaan’s route to the moon. The MIP had to make 5 orbits around the earth and 4 around the moon before impact. Each orbit around the earth was of increasing height and each orbit around the moon was of decreasing height.

 

 

LAUNCH PAD II

 

This is the location that we see every time a launch is broadcast on television. The rocket is assembled and brought to the launch pad. The rocket is electrically insulated from lightning by 4 lightning protection towers. These towers also house high resolution cameras at several levels to monitor the various stages of the rocket. These cameras are protected by concrete enclosures. The launch pad itself is about 70m high. This means that the protection towers are even taller. An anchor is present to hold the rocket in place until the time of blast off. Separate pipes are present to deliver cryogenic fuels, which are supplied at (-) 180 degrees Celsius. Finally, there are exhaust deflection ducts which deflect the exhaust gases through underground tunnels to a place which is a few tens of metres away. In case the flame returns to the rocket, balance will be lost and the rocket may topple. The tunnels are filled with water to reduce pressure and temperature. Also, cryogenic fuel tanks are available in separate towers. Each floor in the launch pad is 4m high. This launch pad is called ‘umbilical’ due to the presence of the pipes which feed fuel to the rocket.

 

 

 

 

 

LAUNCH PAD I

 

Unlike the ‘umbilical’ type, this is a pedestal type. The whole tower moves away from the rocket just before the blast off. As a particular ‘fuel regulation’ process was taking place at the time, entry was denied.

 

 

ASSEMBLY AND STATIC TEST AND EVALUATION COMPLEX

 

This was the last location visited in the range. Two buildings constitute the complex - the assembly building and the test buildings which are placed adjacent to each other. Motors which are in excess of 2m dia are present and they are fabricated in Mumbai.

 

Several tests are done on a launch vehicle, such as vibration test, centrifugal test, and static test. Of these, only the static test is done in SHAR. There are two kinds of static tests - ballistic test and the other is to optimize insulation. After assembly, the motors are tilted horizontally and they are integrated to floating members. The floating members are in turn connected to fixed members. The floating members are made to undergo thrust from the motors and the strain is determined from them. From a calibration curve, the strain is converted to thrust and the motor is characterized. Flexible nozzles of the strap on motors are also tested on this test bed.

 

 

The overall experience was enthralling and inspiring. It helped us appreciate the complex working and tireless effort of the scientists who work to make each launch a success. The inspiration derived was well worth the time spent.

 

We returned with newly found patriotism filled within us, as the trip revealed India to be a superpower in Space Sciences.

(As compiled on the 19th of February 2009)

Introduction

Hi

I'm a student of Electrical and Electronics engineering with a passion!! I'm using this space to display reports of workshops or Industrial visits or seminars, which I have compiled by myself. Hope you find it as informative as it is fun to read. Please do not hesitate to comment on my posts and please feel free to correct me if I get a fact wrong.

As really good events do not fall periodically, i may not post for several weeks or even months, or i may end up giving in several reports in a week. Please bear with the irregularity.

Cheers!!

REPORT ON BASIC ELECTRONICS AND ROBOTICS WORKSHOP

(At College of Engineering, Guindy – on the 10^th and 11^th of January 2009)

(TOPIC: ‘ROBOTICS USING DISCRETE ELECTRONIC COMPONENTS’)

The following is the report on a workshop held at College of Engineering, Guindy on the 10^th and 11^th of January 2009. The workshop was conducted by two R & D employees of a Mumbai based electronics solutions company. The workshop had participants from various technical branches at varying levels – including electronics, Information technology, and Mechanical Engineering, right from 1^st to 4^th years. Besides students from Vishakapatnam, Bengaluru and Tirupati attended the workshop and a total of 20 teams (of twos and threes) participated.

The workshop was aimed at creating a practical approach towards electronics and creating some robots which had basic functionalities – such as sensing sound, light, obstacles, etc and reacting to them in different ways. Many concepts which were dealt with, in regular classes, were brought out alive in the workshop. As students from other branches of Engineering were also present, the instructor took us through the concepts at a slow pace.

THE KIT

The kit contained a collection of resistors and capacitors of different values, transistors, sensors (mic, photodiodes), visible and IR LEDs, a TSOP module, op-amp and 555 timer ICs, a chassis for the robot, a motor driver circuit, two motors and a breadboard which could be mounted on the robot. Also, a multimeter and a manual were supplied with the kit.

SUMMARY of TOPICS COVERED

INTRODUCTION

Robots are human designed machines which perform tasks that may be harder for humans and can be:

-teleoperated(operated from a remote location), or

-manually operated, or

-autonomous(self governing robots)

Teleoperated robots are further classified as wired or wireless. Autonomous robots can be PC controlled (for faster reaction in complex systems), Microcontroller controlled (when no high end calculations are required), or using discrete electronics components (without programming).

BASICS OF ELECTRONICS

THEORY:

The basics were dealt with in this session. The topics covered were – Ohms law, power equation, fixed and variable resistors and their types.

The identification of resistors and variable resistors (from the colour coding, and 3 digit codes) were skills that were put to use later in the workshop. Capacitors, their types (polar and non polar), identification (from 3 digit codes in case of non-polar capacitors) and applications (as timing element, filters and energy storage elements). Theoretical calculations were done to fix current limiting resistors in LED circuits, and potential divider arrangement of the photodiode. Pointers were given to debug circuits.

PRACTICAL:

Glowing LEDs.

TRANSISTORS

THEORY

The various applications of transistors were listed. However, their use in digital circuits is limited to switching. The transistor to be used is mainly decided based on the requirement, and some decisive parameters like V_ce, Ic, DC current gain and Transition frequency. The current limiter resistors, and fixed biasing resistors were fixed through theoretical calculations and data from the datasheet.

PRACTICAL

Transistor as a switch in glowing LEDs.

SENSORS

THEORY

Sensors are an integral part of the robot apart from actuators. The capability and complexity of a robot is directly dependant on the number of sensory inputs.

There are two types of sensors – Proximity/Range sensors and Environmental sensors. Proximity sensors are further classified as mechanical or Reflective. Environmental sensors include light, temperature, pressure, humidity, gases.

IR LEDs, mechanical obstacle sensors, and IR photodiode were studied in detail.

PRACTICAL

The potential divider arrangement of a photodiode, both in light and darkness; light activated robot.

OP-AMPS

THEORY

Operational amplifiers are used to perform various mathematical operations like integration, addition, subtraction, differentiation, etc. The characteristics and their use as a comparator was studied. The advantages and disadvantages of different op-amps were looked into. The dual op-amp LM 358 was used in the following practical work.

The algorithm for line sensor robots (with one and two sensors), two line sensor robots were learnt.

PRACTICAL

Line sensing robot – with one sensor, two sensors;

IC 555

THEORY

The application of the 555 timer was listed – timer, square wave generator, comparator, Schmitt trigger, etc. The various modes were listed, of which the monostable and astable modes and their connections were studied in detail.

The TSOP module was also studied after this topic.

PRACTICAL

Monostable state of LM555 – connection; Astable operation of LM555 – square wave generator, timer; Clap activated robot, obstacle sensing robot using TSOP.

- - - - - - - - - -

In addition, several other modifications were suggested in the manual that was provided, resulting in a large number of combinations of robots, making the kit ideal for most competitions.

We were also told about the ‘Micromouse’ competition, which is claimed to be the world’s most advanced robotics competition. We were inspired to develop our skills to that level to make it possible for us to participate in such competitions.

The total cost of the workshop was around Rs.5000 per team, which included the kit. The practical approach to electronics was very refreshing and unique. Indeed, the money spent on the training was worth it. The workshop was both enlightening and entertaining. And we would recommend such workshops to our classmates.

(As compiled on 18th of january, 2009. The workshop was attended with a classmate - Raghavan)