GS-3, Science & Tech, Uncategorized

What is the difference between GSLV and PSLV?

Both PSLV (Polar Satellite Launch Vehicle) and GSLV (Geosynchronous Satellite Launch Vehicle) are the satellite-launch vehicles (rockets) developed by ISRO. PSLV is designed mainly to deliver the “earth-observation” or “remote-sensing” satellites with lift-off mass of up to about 1750 Kg to Sun-Synchronous circular polar orbits of 600-900 Km altitude.

The remote sensing satellites orbit the earth from pole-to-pole (at about 98 deg orbital-plane inclination). An orbit is called sun-synchronous when the angle between the line joining the centre of the Earth and the satellite and the Sun is constant throughout the orbit.

Due to their sun-synchronism nature, these orbits are also referred to as “Low Earth Orbit (LEO)” which enables the on-board camera to take images of the earth under the same sun-illumination conditions during each of the repeated visits, the satellite makes over the same area on ground thus making the satellite useful for earth resources monitoring.

Apart from launching the remote sensing satellites to Sun-synchronous polar orbits, the PSLV is also used to launch the satellites of lower lift-off mass of up to about 1400 Kg to the elliptical Geosynchronous Transfer Orbit (GTO).

PSLV is a four-staged launch vehicle with first and third stage using solid rocket motors and second and fourth stages using liquid rocket engines. It also uses strap-on motors to augment the thrust provided by the first stage, and depending on the number of these strap-on boosters, the PSLV is classified into its various versions like core-alone version (PSLV-CA), PSLV-G or PSLV-XL variants.

The GSLV is designed mainly to deliver the communication-satellites to the highly elliptical (typically 250 x 36000 Km) Geosynchronous Transfer Orbit (GTO). The satellite in GTO is further raised to its final destination, viz., Geo-synchronous Earth orbit (GEO) of about 36000 Km altitude (and zero deg inclination on equatorial plane) by firing its in-built on-board engines.

Due to their geo-synchronous nature, the satellites in these orbits appear to remain permanently fixed in the same position in the sky, as viewed from a particular location on Earth, thus avoiding the need of a tracking ground antenna and hence are useful for the communication applications.

Two versions of the GSLV are being developed by ISRO. The first version, GSLV Mk-II, has the capability to launch satellites of lift-off mass of up to 2,500 kg to the GTO and satellites of up to 5,000 kg lift-off mass to the LEO. GSLV MK-II is a three-staged vehicle with first stage using solid rocket motor, second stage using Liquid fuel and the third stage, called Cryogenic Upper Stage, using cryogenic engine.

GS-3, Science & Tech, Uncategorized

10 facts you about ISRO’s GSLV-Mk III

The Geosynchronous Satellite Launch Vehicle-Mark III (GSLV-Mk III), the heaviest rocket ever made by India and capable of carrying large payloads, is set for launch from the Satish Dhawan Space Centre in Sriharikota on June 5, 2017.

Here are a few facts you need to know about the rocket.

1. GSKV-Mk III is capable of launching four-tonne satellites in the Geosynchronous Transfer Orbit (GTO).

2. The rocket is also capable of placing up to eight tonnes in a Low Earth Orbit (LEO), enough to carry a manned module.

3. GSLV-Mk III’s first developmental flight, D1, will carry on June 5 the GSAT-19 satellite — developed to help improve telecommunication and broadcasting areas.

4. This is India’s first fully functional rocket to be tested with a cryogenic engine that uses liquid propellants — liquid oxygen and liquid hydrogen.

5. It took about 25 years, 11 flights and over 200 tests on different components of the rocket for it to be fully realised.

6. The 640-tonne rocket, equal to the weight of 200 fully-grown Asian elephants, is the country’s heaviest but shortest rocket with a height of 43 metre.

7. GSLV-Mk III is a three-stage vehicle with two solid motor strap-ons (S200), a liquid propellant core stage (L110) and a cryogenic stage (C-25).

8. ISRO successfully conducted the static test of its largest solid booster S200 at the Satish Dhawan Space Centre (SDSC), Sriharikota on January 24, 2010. The successful test of S200, which forms the strap-on stage for the GSLV, makes it the third largest solid booster in the world. The static test of liquid core stage (L110) of GSLV-Mk III launch vehicle was done at ISRO’s Liquid Propulsion Systems Centre test facility as early as March 2010.

9. C-25, the large cryogenic upper stage of the GSLV, is the most difficult component of the launch vehicle to be developed. ISRO successfully ground-tested the indigenously developed C-25 on February 18, 2017.

10. If successful, the GSLV-Mk III — earlier named as Launch Vehicle Mark-3 or LVM-3 — could be India’s vehicle of choice to launch people into space.

Big Picture, Uncategorized

ISRO test firing Scramjet Rocket Engine.


The first experimental mission of ISRO’s Scramjet Engine towards realisation of Air Breathing Propulsion System was carried out successfully. It is a new technology which is not available with many countries. India is the fourth country to demonstrate the flight testing of scramjet engine. Many countries have tested a Scramjet but no country has mastered a Scramjet.

The development of a supersonic combustion Scramjet Engine is a mile stone for ISRO and India. To give a simple analogy, it is trying to light a candle when there is a super cyclone blowing through. This is what ISRO has done. Lighting the rocket engine when it is travelling six times the speed of sound and to sustain the fire for a sufficient time is a big leap forward. ISRO is continuing its Innovation spree.

How is Scramjet Rocket different from Conventional Rocket

  • Conventional rockets have to carry fuel as well as oxidising agent because no fuel can burn without oxygen and in space there is no oxygen. Scramjet rockets draw oxygen from the air and use a compressor to compress the air, ignite it and burn the fuel.
  • The uniqueness of the Scramjet Engine is that it draws oxygen from the air. Here the compression is done during the movement of the rocket itself. Therefore it moves very fast, 6 times the speed of sound.

ISRO’s scramjet engine launch

  • Scramjet was tested with Rohini Rocket, which is a conventional sounding rocket used regularly for scientific studies.
  • Scramjet was fixed to the second stage, the first being conventional rocket which fell off at 11 kms and then the Scramjet was ignited and started.
  • The test-flight is maiden short duration experimental test of ISRO’s scramjet engine with a hypersonic flight at Mach 6 (six times the speed of sound).
  • Scramjet engines designed by ISRO uses hydrogen as fuel and the oxygen from the atmospheric air as the

Uses of Scramjet Engine

  • Scramjet can be used in Rocket Engine and to make more efficient missiles. In the long run in four to five decades we can have planes powered by Scramjets which would make travel faster and cheaper.
  • Services from space will become cheaper and more people will be able to access space services. Banking industry, television broadcasting, and connectivity is dependent on satellites. Launching cost will come down. It will take a long time to have a full fledged Scramjet rocket.
  • Scramjet and Reusable launch vehicle will be of great use because the launch cost will come down.
  • Essentially the endeavour is to lower the cost of rocket launcher. Carrying oxidiser is an unnecessary weight for the rocket during atmospheric phase if we can use the oxygen around it.

Limitations of Scramjet Rocket Engine

  • Scramjet cannot be used to launch the rocket. We have to use the conventional fuel and oxidiser to launch the rocket. We know that oxygen is available till 50 kms from the ground. Scramjet will be into operation till that distance, beyond that it will not work.
  • It has a limited role. Normally in the first or the second stage is when a Scramjet can be deployed.

Scramjet Engine is different from Cryogenic Engine. Cryogenic Engine functions in the space in near vacuum condition and it provides a specific impulse which is very high.

ISRO says there was the challenge of making the right materials so that at high velocity the engine ignites. Right now it is the mastery of materials which is required for Scramjet.


  • The desire of ISRO is to place the Scramjet below the Reusable Launch Vehicle while launching. This will reduce the launch cost drastically. In Reusable Launch Vehicle 85% of the material cost is saved and by using the oxidiser from the atmosphere would further reduce the cost drastically.
  • The next step is to make it a bigger test flight, make it a prototype, then take it to an experimental flight, and finally to an operational flight. This is a matter of next 20 to 25 years of development and will be an ultra futuristic rocket engine. This is a first step towards realisation of a complex technology and a step in the right direction.
GS-3, Science & Tech, Uncategorized

China launches world’s first quantum communications satellite to develop hack-proof tech

China recently launched the first-ever quantum satellite. The satellite is named “Micius“.

  • Many countries are working on quantum communications, including fiber-optic quantum key distribution networks in the United States, Europe, and China. However, China is the first one to launch a satellite to develop the complex technology.
  • The 500 kg satellite contains a quantum key communicator, quantum entanglement emitter, entanglement source, processing unit, and a laser communicator. A rocket named the Long March-2D launched the satellite into space. The launch site was in China’s northwest Gobi Desert.
  • The satellite is built to circle Earth at an altitude of around 310 miles (500 km) and complete one lap every 90 minutes.


Aims of this mission:

  • It is a proof-of-concept mission designed to facilitate quantum optics experiments over long distances to allow the development of quantum encryption and quantum teleportation technology.
  • The satellite’s two-year mission will be to develop ‘hack-proof’ quantum communications, allowing users to send messages securely and at speeds faster than light.
  • The scientific goals are to implement a series of science missions between Quantum Science Satellite and quantum communication ground stations.


The major tasks are as follows:

Quantum Key Distribution from Satellite to Ground: To set up an ultra-long-range quantum channel between ground and satellite with the assistance of high-precision acquisition, tracking and pointing system, implement a quantum key distribution between the satellite and the ground stations, and carry out unconditional secure quantum communication experiments.

Global Scale Quantum Communication Network: To set up a real wide-area network for quantum communication using the satellite repeater and two arbitrary quantum ground stations and their auxiliary local-area fiber quantum networks.

Quantum Entanglement Distribution from Satellite to two ground stations: Distribution of quantum entangled photons from the satellite to two distant ground stations whose distance is larger than one thousand kilometers; test of the entanglement properties at a large scale and nonlocality of quantum mechanics.

Quantum Teleportation from Ground to Satellite: as a totally new way of communication, quantum teleportation is the fundamental process of quantum networks and quantum computing. A high quality quantum entanglement source on the ground will be built to achieve ground-to-satellite teleportation experiments based on photon entanglement.


Significance of this launch:

This is an attempt to develop a hack-proof communications system. During its two-year mission the space object will transmit un-hackable encryption keys from outer space to the Earth’s surface. If the experiment works it could solve the main problem of distributing encryption keys that cannot be stolen. That would result in hack-proof communications.

It will also provide new knowledge about quantum entanglement. That happens when pairs or groups of very tiny particles are made or work together so the quantum state of each particle is part of a whole system.


How the satellite operates?

QUESS will use entangled photons via a special laser to transmit messages to ground stations in China and Austria. In theory such systems are safe from hack attacks. An attempt to intercept an encryption key would cause a change in the photons’ state that could be picked up.

  • The special kind of laser has several curious properties, one of which is known as “the observer effect” – its quantum state cannot be observed without changing it.
  • So, if the satellite were to encode an encryption key in that quantum state, any interception would be obvious. It would also change the key, making it useless.
  • Highly complex attempts to build such a “hack-proof” communications network are based on the scientific principle of entanglement.


What Is Quantum Entanglement?

Quantum entanglement is one of the central principles of quantum physics. In short, quantum entanglement means that multiple particles are linked together in a way such that the measurement of one particle’s quantum state determines the possible quantum states of the other particles.

  • This connection is independent of the location of the particles in space. Even if you separate entangled particles by billions of miles, changing one particle will induce a change in the other. Even though quantum entanglement appears to transmit information instantaneously, it doesn’t actually violate the classical speed of light because there’s no “movement” through space.
  • It is hence difficult to wiretap, intercept or crack the information transmitted through it.


So what exactly is a quantum-enabled satellite?

It contains a laser that transmits a pair of entangled photons – minuscule sub-atomic particles of light – down to two separate base stations.

  • One half of the pair goes to one base station, the other to the second.
  • These photons suffer from something known as the ‘observer effect’, which means that the moment anyone tries to intercept them, their quantum state is immediately changed.

What are the applications?

In the face of ever more powerful hacking and surveillance – which could one day also include powerful quantum computers – the security of commercial communications is also increasingly important. Hence, Quantum computing is largely seen as the next big thing in communications. The technology has applications for precision in everything from healthcare to industrial production.



Cybersecurity has been a major focus in recent years for China. Quantum messaging could become a major defense against hackers and have applications ranging from military and government communications to online shopping.

Editorials, GS-3, Science & Tech, Uncategorized

India’s eye in the sky

NAVIC (Navigation with Indian Constellation), India’s indigenous global navigation satellite system, is expected to become fully operational from this month.

What is NAVIC?

NAVIC is an independent regional navigation satellite system designed to provide position information in the Indian region and 1500 km around the Indian mainland.

What all services are provided?

Its applications include:IRNSS would provide two types of services, namely Standard Positioning Services available to all users and Restricted Services provided to authorised users.

  • Terrestrial, Aerial and Marine Navigation.
  • Disaster Management.
  • Vehicle tracking and fleet management.
  • Integration with mobile phones.
  • Precise Timing.
  • Mapping and Geodetic data capture.
  • Terrestrial navigation aid for hikers and travelers.
  • Visual and voice navigation for drivers.

How is India going in a global context?

India has been making great progress in space and research fields. Indian GPS would certainly boost country’s credentials in this field. India becomes only the fifth entity to have a GPS system of their own. Apart from India, US has Global Positioning System (GPS), Russia has Glonass, Europe has Galileo and China has BeiDou as their navigational systems. NAVIC will reduce the dependencies on the other systems for the country. That means that even in a war-like situation there would be no interruption of the information.

How many satellites does NAVIC consist of? When were they launched?

IRNSS is a regional system and so its constellation will consist of seven satellites. Three of these will be geostationary over the Indian Ocean, i.e., they will appear to be stationary in the sky over the region, and four will be geosynchronous – appearing at the same point in the sky at the same time every day. This configuration ensures each satellite is being tracked by at least one of fourteen ground stations at any given point of time, with a high chance of most of them being visible from any point in India. IRNSS satellites are numbered from 1A to 1G.

Why it is necessary to have indigenous global navigation system?

Having a global navigation system bolsters the ability of a nation to serve as a net security provider, especially through the guarantee of such assurance policies. It can also play a significant role in relief efforts post disasters such as the tsunami in the Indian Ocean region in 2004 and the Pakistan-India earthquake in 2005.

Through land-area mapping, yield monitoring and precision-planting of crops, NAVIC allows for the development of civic capabilities in food and livelihood security.Potential applications of NAVIC:

  • NAVIC also arrives as an instrument for environmental and meteorological monitoring, as well as climate research. These capabilities can be leveraged to design reliable and efficient response mechanisms for natural disasters, alleviating the devastation they wreak through well-managed disaster relief.
  • NAVIC’s interoperability with GPS can ensure the minimization of technical snags when used complementarily with existing GPS-enabled solutions.
  • Chief beneficiary of Navic is the military, which now has access to an encrypted and completely secure service. The forces will no longer have to depend on the US service, a weakness that was exposed during the Kargil conflict of 1999, when accurate GPS data on the region was not forthcoming in real time.
  • Navic will offer public access to an unsecured service for civilian applications like logistics, transportation, vehicle automation, robotics, disaster management, prospecting, the tracking of vehicles, people, pets and the Internet of Things. This could trigger a boom in GPS applications tuned to Navic.
  • This could also provide an occasion for hardware manufacturers to turn protectionist and urge government to force manufacturers of GPS products to patronise the Indian service.

How this would improve bilateral relations?

Building on India’s offering of assistance to Pakistan during the floods in Pakistan-occupied Kashmir and other areas in 2014, NAVIC could establish a tradition of regional monitoring whereby India leverages its technological edge to safeguard citizens across the subcontinent. Such gestures could blunt the adversarial nature of Indo-Pakistan relations in the long run, signalling to the region and the globe alike that India values human security despite prevailing gridlock in strategic relations. NAVIC might even go some way to mend and meliorate relations with a guarded Islamabad.

Charting out growth routes for South Asian economies, South Asian Association for Regional Cooperation (Saarc) governments can also welcome the launch of NAVIC as an opening shot to accelerated innovation. NAVIC should also propel technological innovations and spin-offs that render South Asia progressively less reliant on technological imports from the West and elsewhere.


Now, India should work to shift the regional frame of mind from defence thinking to subcontinental cooperation, pushing back against isolationist impulses that stand in the way of realizing the civilian and commercial promise of NAVIC. An ability to integrate space infrastructure into the Indian state apparatus has fortunate ripple effects beyond Indian borders. In dedicating itself to exploring and actualizing the civilian and commercial potential of NAVIC, India can signal to its regional partners that its rise is not only passively peaceful but also directly beneficial to those it can lift up in its tide.

GS-3, Science & Tech, Uncategorized

Launching Aditya-L1 satellite for solar study underway- ISRO chairman

ISRO chairman Kiran Kumar recently revealed that the scientific mission of launching Aditya-L1 satellite for solar studies is underway. Aditya-L1 is slated for lift-off in 2018-2019.

About the mission:

  • It is India’s first solar mission. It will study the sun’s outer most layers, the corona and the chromospheres and collect data about coronal mass ejection, which will also yield information for space weather prediction.
  • The project costs approximately Rs 400 crores and is a joint venture between ISRO and physicists from Indian Institute of Astrophysics, Bengaluru; Inter University Centre for Astronomy and Astrophysics, Pune; Tata Institute of Fundamental Research, Mumbai, and other institutes.
  • The data from Aditya mission will be immensely helpful in discriminating between different models for the origin of solar storms and also for constraining how the storms evolve and what path they take through the interplanetary space from the Sun to the Earth.
  • In order to get the best science from the sun, continuous viewing of the sun is preferred without any occultation/ eclipses and hence, Aditya- L1 satellite will be placed in the halo orbit around the Lagrangian point 1 (L1) of the sun-earth system.



What are Lagrangian points and halo orbit?

Lagrangian points are the locations in space where the combined gravitational pull of two large masses roughly balance each other. Any small mass placed at that location will remains at constant distances relative to the large masses. There are five such points in Sun-Earth system and they are denoted as L1, L2, L3, L4 and L5. A halo orbit is a periodic three-dimensional orbit near the L1, L2 or L3.