SPACE TECHNOLOGY
1.1 Types of Orbits
• There are many different satellite orbits that can be used depending upon satellite’s functions and area it is to serve.
• The lower the satellites orbit the Earth, the stronger the gravitational pull, and this means that the satellite must travel faster to counteract this pull. Further away the gravitational field is less and the satellite velocities are correspondingly less.
• A satellites orbit the Earth in one of two basic types of orbit such as Circular and Elliptical satellite orbit.
• For a circular orbit, the distance from the Earth remains the same at all times whereas the elliptical orbit
changes the distance to the Earth.
• Circular orbits are classified into Low Earth Orbit, Medium Earth Orbit, Geosynchronous orbit etc.
• Most satellites, the International Space Station, the Space Shuttle, and the Hubble Space Telescope are all in Low Earth Orbit.
• LEO is convenient for installing new instruments, fixing things that are broken, and inspecting damage.
• A geosynchronous orbit, located at 35,790 km has the same orbital period as the sidereal rotation period of the Earth.
• It allows satellites to synchronize with the
rotation of the Earth (only in time and not in direction).
• This makes geosynchronous satellites particularly useful for telecommunications and other remote sensing applications.
• One particular form of geosynchronous orbit is known as a geostationary orbit, in which the satellite rotates in the same direction as the rotation of the Earth and has an approximate 24 hour period.
• The satellite placed in geostationary orbit remains in the same position relative to the Earth.
• It is used by many applications including direct broadcast as well as communications or relay systems.
• While geosynchronous satellites can have any inclination, geostationary orbit lie on the same plane as the equator.
• Polar Orbit –Satellites placed in polar orbits have an inclination of about 90 degrees to the
equator and travels north-south over the poles at lower altitudes.
• A satellite in the polar orbit approx. takes 90 minutes for a full rotation. As a result, a satellite can observe the entire surface in the time span of 24 hours.
They are often used for applications such as monitoring crops, forests and even global security.
• Sun Synchronous Orbit –It is a special case of Polar Orbit moving from pole to pole allowing satellite to pass over any given point of the planet's surface at roughly the same local time each day.
• Since there are 365 days in a year and 360 degrees in a circle, it means that the satellite has to shift its orbit by approximately one degree per day.
• These orbits are used for satellites that need a constant amount of sunlight and are useful for imaging, spy, and weather satellites.
1.2 Types of Satellites
• Communication Satellitesprovides services to telecommunications, television broadcasting, satellite newsgathering, societal applications, weather forecasting, disaster warning and Search and Rescue operations.
• The Indian National Satellite (INSAT) series of satellites in Geostationary Orbit (INSAT-3A, 3C, 4A, 4B, 4CR) are used for communication purposes.
• GSAT series also joins the constellation of INSAT system in providing communication services.
• Earth Observation Satellitesare used for several applications covering agriculture, water resources, urban planning, rural development, mineral prospecting, environment, forestry, ocean resources and disaster management.
• Indian Remote Sensing (IRS) series of satellites in Sun-synchronous polar orbit are Earth observation satellites.
• Currently, 13 operational satellites are in Sun-synchronous orbit – RESOURCESAT-1, 2, 2A CARTOSAT-1, 2, 2A, 2B, RISAT-1 and 2, OCEANSAT-2, Megha-Tropiques, SARAL and SCATSAT-1.
• There are 4 satellites in Geostationary orbit - INSAT-3D, Kalpana & INSAT 3A, INSAT -3DR which is also used for resource mapping.
• Navigation Satellitesare used to meet the emerging demand of positioning, navigation and timing and also civil aviation requirements. GAGAN and IRNSS (NAVIC) are navigation satellite system in use.
• GPS Aided GEO Augmented Navigation (GAGAN), is implemented jointly by ISRO and Airport Authority of India (AAI).
• The main objectives of GAGAN are to provide Satellite-based Navigation services with accuracy and integrity required for civil aviation applications and to provide better Air Traffic Management over Indian Airspace.
• The GAGAN Signal-In-Space (SIS) is available through GSAT-8 and GSAT-10.
• Indian Regional Navigation Satellite System (IRNSS), NavIC is an independent regional navigation satellite system to provide accurate position information service.
• Space Science and Exploration Satellites encompasses research in areas like astronomy, astrophysics, planetary and earth sciences, atmospheric sciences and theoretical physics.
• Eg – Mars Orbiter Mission, AstroSat, Chandrayaan -1,2.
1.3 Launch Vehicles
• Launch Vehicles are used to carry spacecraft to space.
• Following are the various launch vehicles used by ISRO
• Historic launchers - Satellite Launch Vehicle - 3 (SLV-3) and Augmented Satellite Launch Vehicle (ASLV).
• SLV was India's first experimental satellite launch vehicle with solid engines in all 4 stages. ASLV has 3 times augmented capacity of SLV-3.
• Operational launchers - Polar Satellite Launch Vehicle (PSLV) and Geosynchronous Satellite Launch Vehicle (GSLV) and Sounding Rockets.
• Future launchers – GSLV MK-III, Reusable Launch Vehicle (RLV-TD), Scramjet Engine – TD.
PSLV
• It is the3rd generation launch vehicle and first Indian launch vehicle to be equipped with liquid stages.
• PSLV emerged as the reliable and versatile workhorse launch vehicle of India with consecutively successful missions.
• It successfully launched two spacecraft such as Chandrayaan-1 in 2008 and Mars Orbiter Spacecraft in 2013.
• 3 variations in PSLV - PSLV-G (General), PSLV-XL variants and PSLV-CA (Core Alone).
• It has 4 stages in its operation to provide thrust in launching spacecraft to different orbits.
• Stage I: It uses solid rocket motor that is augmented by 6 solid strap-on boosters. Strap on boosters are used only in G and XL variation.
• Stage II: It uses an Earth storable liquid rocket engine, known as the Vikas engine.
• Stage III: It uses solid rocket motor that provides high thrust after the atmospheric phase of the launch.
• Stage IV: It comprises two Earth storable liquid engines.
• Capacity - 1,750 kg of payload to Sun-Synchronous Polar Orbits of 600 km altitude and to 1,425 kg of payload to Geosynchronous and Geostationary orbits, like satellites from the IRNSS constellation.
• PSLV launches in 2018/2019–PSLV - C44/Microsat, Kalamsat ; PSLV – C43/ Hysis ; PSLV – C42/foreign satellites; PSLV – C41/IRNSS-1I ; PSLV - C40/Cartosat-2 series.
GSLV
• It is the 4th generation launch vehicle, a three-stage vehicle with four liquid strap-on boosters.
• GSLV Mk II is the largest launch vehicle developed by India, which is currently in operation.
1. Stage I: It uses solid rocket motor with 4 liquid strap-ons.
2. Stage II: It uses liquid rocket engine (similar to vikas engine of PSLV stage II).
3. Stage III: It uses India’s first cryogenic engine (CE-7.5) in the upper stage. It enabled the launching of 2000 kg of communication satellites.
• Capacity - It can take up to 5000 kg of pay load to Low Earth Orbits, 2500 kg of payload to Geosynchronous Transfer Orbit (GTO) which are primarily INSAT class of communication satellites.
• GSLV Launches in 2018/19 – GSLV – F11/GSAT-7A and GSLV – F08/GSAT – 6A mission.
• The next variant of GSLV is GSLV Mk III, with indigenous high thrust cryogenic engine.
GSLV MK III
• GSLV Mk III is a three-stage heavy lift launch vehicle which has two solid strap-ons, a core liquid booster and a cryogenic upper stage.
• The cryogenic upper stage C25 is powered by CE-20 which is India's largest cryogenic engine.
• It is designed to carry 4000 kg classes of satellites into Geosynchronous Transfer Orbit (GTO) or about 8000 kg classes to Low Earth Orbit (LEO), which is about twice the capability of GSLV Mk II.
• Recent Launches - GSLV Mk III-D2 / GSAT-29, GSLV MK III D1/GSAT – 19 and LVM-3 /CARE (Crew module Atmospheric Re-entry Experiment) mission.
• It is the designated launch vehicle for India’s upcoming second moon mission and the first human space flight scheduled for 2022.
Cryogenic Engine
• Cryogenics is the science that addresses the production and effects of very low temperatures.
• A cryogenic rocket engine uses a cryogenic fuel or oxidizer, which are gases liquefied and stored at very low temperatures.
• Notably, these engines were one of the main factors of NASA's success in reaching the Moon.
• Amongst all rocket fuels, hydrogen is known to provide the maximum thrust.
• But hydrogen, in its natural gaseous form, is difficult to handle, and, therefore, not used in normal engines in rockets like PSLV. However, hydrogen can be used in liquid form.
• The problem is hydrogen liquefies at very low temperature, nearly 250 degrees Celsius below zero.
• To burn this fuel, oxygen also needs to be in liquid form, and that happens at about 90 degrees Celsius below zero.
• Creating such a low-temperature atmosphere in the rocket is a difficult proposition, because it creates problems for other material used in the rocket.
RLV-TD
• Reusable Launch Vehicle – Technology Demonstrator (RLV-TD) is a fully reusable launch vehicle to enable low cost access to space.
• The configuration of RLV-TD is similar to that of an aircraft and combines the complexity of both launch vehicles and aircraft.
• The winged RLV-TD has been configured to act as a flying test bed to evaluate various technologies, namely, hypersonic flight, autonomous landing and powered cruise flight.
• In future, this vehicle will be scaled up to become the first stage of India’s reusable two stage orbital launch vehicle.
• Objectives of RLV-TD - Hypersonic aero thermodynamic characterisation of wing body, Evaluation of autonomous Navigation, Guidance and Control (NGC) schemes, Integrated flight management and Thermal Protection System Evaluation
• It was successfully flight tested in 2016 from Sriharikota.
Scramjet Engine - TD
• Usually, launch vehicles carry oxidiser along with the fuel for combustion to produce thrust to launch satellites into orbit.
• Nearly, 70% of the propellant (fuel – oxidiser) by weight consists of oxidiser which makes it to carry only 2-4% of their lift-off mass to orbit.
• Therefore, air-breathing propulsion system which can utilise the atmospheric oxygen during their flight and reduce the total propellant required to place a satellite in orbit is being developed by various space agencies.
• Ramjet, Scramjet and Dual Mode Ramjet (DMRJ) are the three concepts of air-breathing engines.
• A ramjet is a form of air-breathing jet engine that uses the vehicle’s forward motion to compress incoming air for combustion without a rotating compressor.
• Fuel is injected in the combustion chamber where it mixes with the hot compressed air and ignites.
• It works most efficiently at supersonic speeds around Mach 3 (three times the speed of sound) and can operate up to speeds of Mach 6.
• However, the ramjet efficiency starts to drop when the vehicle reaches hypersonic speeds.
• A scramjet engine is an improvement over the ramjet engine as it efficiently operates at hypersonic speeds and allows supersonic combustion. Thus, it is known as Supersonic Combustion Ramjet, or Scramjet.
• A dual mode ramjet (DMRJ) is a type of jet engine where a ramjet transforms into scramjet over Mach 4-8 range, which means it can efficiently operate both in subsonic and supersonic combustor modes.
• ISRO’s Advanced Technology Vehicle (ATV), which is an advanced sounding rocket, was the solid rocket booster used for test of Scramjet engines at supersonic conditions.
• ATV is a two- stage solid launch vehicle capable of carrying Scramjet engines weighed 3277 kg at lift-off.
• India is the fourth country (after USA, Russia and European Space Agency ) to demonstrate the flight testing of a Scramjet Engine.
Small Satellite Launch Vehicle
• ISRO has completed the design of baby rocket “Small Satellite Launch Vehicle (SSLV)”.
• SSLV can place a 500 kg payload at a height of 500 km in the Low Earth Orbit (LEO).
• It has three solid motor stages with a lift off mass of 120 tonnes.
• It is shorter in length than the PSLV and GSLV.
• It can accommodate multiple satellites like the PSLV and GSLV, albeit smaller ones.
• Unlike the PSLV and GSLV, the SSLV can be assembled both vertically and horizontally.
Vikas Engine
• Vikas is a family of liquid fuelled rocket engines that powers India’s launch vehicles PSLV and GSLV.
• It is aimed at improving the payload capability of PSLV, GSLV and GSLV Mk-III launch vehicles.
• It is used in second stage of PSLV which consists of four stages in its operation (Solid-Liquid-Solid-Liquid) and in second stage and four strap-on stages of GSLV.
• GSLV is a three-stage vehicle (Solid-Liquid-Cryogenic Engine) with four liquid strap-on boosters.
• ISRO has recently improved the thrust of the Vikas engine which is expected to boost the rocket engine.
• The main beneficiary of the high-thrust Vikas engine is GSLV-Mark III launcher, which is expected to lift 4,000-kg satellites to space.
• GSLV-Mark III uses twin engine core liquid stage (L110).
• GSLV – Mark III with upgraded Vikas engine would be the third Mk-III and the first working one to be designated MkIII Mission-1 or M1.
Indian Missions
1.4 PSLV C-44/Kalamsat
• PSLV C-44 has successfully injected Microsat-R and Kalamsat-V2 satellites into their designated orbits from Sriharikota.
• It is a new variant of PSLV called PSLV-DL (D standing for demonstration).
• In its normal configuration, the rocket will have six strap-on motors in the first stage.
• However, PSLV-DL will have just two strap-on motors for the first time.
• In a normal launch vehicle, each stage falls off after fuel completes burn-off.
• However, stage four, after releasing the payload, wanders around in space as junk.
• PSLV-DL will follow the same pattern, except that the fourth stage (PS4) won’t fall off.
• It will serve as a platform for the satellite like deploying solar panels or other tools to aid the satellite.
• Kalamsat is the first satellite to use PS4 as an orbital platform, thus reducing space debris.
• It is a 10cm cube communication nano-satellite weighing about 1.2kg designed by students.
• Its life span is about two months and its cost is about Rs. 12 lakh.
• A 64-gram version of the Kalamsat nicknamed "gulab jamun" was launched by NASA in 2017. But it never reached orbit.
• Microsat-R is a 130-kg military imaging satellite.It was put together by a handful of DRDO laboratories.
1.5 PSLV C-43/HysIS
• It has successfully launched India’s first Hyper spectral Imaging Satellite (HysIS) and 30 international co-passenger satellites.
• PSLV-C43 is the Core Alone version of PSLV, without the six strap-ons.
• HysIS is an earth observation satellite, weighing about 380 kg and configured around ISRO’s Mini Satellite-2 (IMS-2) bus.
• The goal is to study the earth’s surface in the visible, near infrared and shortwave infrared regions of the electromagnetic spectrum.
• It has a mission life of about 5 years.
• A hyperspectral imaging camera in space can provide well-defined images that can help to identify objects on Earth far more clearly than regular optical or remote sensing cameras.
• The technology will be an added advantage of watching over India from space for a variety of purposes such as defense, agriculture, land use, minerals and so on.
1.6 HySIS
• Hyperspectral Imaging Satellite (HySIS) is a full-fledged earth observation satellite, going to be launched by ISRO.
• Hyperspectral or Hyspex imaging enables distinct identification of objects on earth by reading the spectrum for each pixel of a scene from space.
• The satellite has the Hyperspectral imager which can identify 55 spectral or colour bands from 630 km above ground.
• It can be used for monitoring of environment, finding oil and minerals apart from military surveillance.
• Hyspex was first tried out in Chandrayaan-1 mission which mapped the lunar mineral resources.
1.7 PSLV C-42
• It has launched two foreign satellites - NovaSAR and S1-4 of United Kingdom.
• PSLV C-42 is also a Core Alone version of PSLV, without the six strap-ons.
• Both satellites are earth observation systems and injected in Sun Synchronous Orbit.
• NovaSAR is a S-Band Synthetic Aperture Radar satellite intended for forest mapping, land use & ice cover monitoring, flood & disaster monitoring.
• S1-4 is a high-resolution Optical Earth Observation Satellite, used for surveying resources, environment monitoring, urban management and for the disaster monitoring.
1.1 Types of Orbits
• There are many different satellite orbits that can be used depending upon satellite’s functions and area it is to serve.
• The lower the satellites orbit the Earth, the stronger the gravitational pull, and this means that the satellite must travel faster to counteract this pull. Further away the gravitational field is less and the satellite velocities are correspondingly less.
• A satellites orbit the Earth in one of two basic types of orbit such as Circular and Elliptical satellite orbit.
• For a circular orbit, the distance from the Earth remains the same at all times whereas the elliptical orbit
changes the distance to the Earth.
• Circular orbits are classified into Low Earth Orbit, Medium Earth Orbit, Geosynchronous orbit etc.
• Most satellites, the International Space Station, the Space Shuttle, and the Hubble Space Telescope are all in Low Earth Orbit.
• LEO is convenient for installing new instruments, fixing things that are broken, and inspecting damage.
• A geosynchronous orbit, located at 35,790 km has the same orbital period as the sidereal rotation period of the Earth.
• It allows satellites to synchronize with the
rotation of the Earth (only in time and not in direction).
• This makes geosynchronous satellites particularly useful for telecommunications and other remote sensing applications.
• One particular form of geosynchronous orbit is known as a geostationary orbit, in which the satellite rotates in the same direction as the rotation of the Earth and has an approximate 24 hour period.
• The satellite placed in geostationary orbit remains in the same position relative to the Earth.
• It is used by many applications including direct broadcast as well as communications or relay systems.
• While geosynchronous satellites can have any inclination, geostationary orbit lie on the same plane as the equator.
• Polar Orbit –Satellites placed in polar orbits have an inclination of about 90 degrees to the
equator and travels north-south over the poles at lower altitudes.
• A satellite in the polar orbit approx. takes 90 minutes for a full rotation. As a result, a satellite can observe the entire surface in the time span of 24 hours.
They are often used for applications such as monitoring crops, forests and even global security.
• Sun Synchronous Orbit –It is a special case of Polar Orbit moving from pole to pole allowing satellite to pass over any given point of the planet's surface at roughly the same local time each day.
• Since there are 365 days in a year and 360 degrees in a circle, it means that the satellite has to shift its orbit by approximately one degree per day.
• These orbits are used for satellites that need a constant amount of sunlight and are useful for imaging, spy, and weather satellites.
1.2 Types of Satellites
• Communication Satellitesprovides services to telecommunications, television broadcasting, satellite newsgathering, societal applications, weather forecasting, disaster warning and Search and Rescue operations.
• The Indian National Satellite (INSAT) series of satellites in Geostationary Orbit (INSAT-3A, 3C, 4A, 4B, 4CR) are used for communication purposes.
• GSAT series also joins the constellation of INSAT system in providing communication services.
• Earth Observation Satellitesare used for several applications covering agriculture, water resources, urban planning, rural development, mineral prospecting, environment, forestry, ocean resources and disaster management.
• Indian Remote Sensing (IRS) series of satellites in Sun-synchronous polar orbit are Earth observation satellites.
• Currently, 13 operational satellites are in Sun-synchronous orbit – RESOURCESAT-1, 2, 2A CARTOSAT-1, 2, 2A, 2B, RISAT-1 and 2, OCEANSAT-2, Megha-Tropiques, SARAL and SCATSAT-1.
• There are 4 satellites in Geostationary orbit - INSAT-3D, Kalpana & INSAT 3A, INSAT -3DR which is also used for resource mapping.
• Navigation Satellitesare used to meet the emerging demand of positioning, navigation and timing and also civil aviation requirements. GAGAN and IRNSS (NAVIC) are navigation satellite system in use.
• GPS Aided GEO Augmented Navigation (GAGAN), is implemented jointly by ISRO and Airport Authority of India (AAI).
• The main objectives of GAGAN are to provide Satellite-based Navigation services with accuracy and integrity required for civil aviation applications and to provide better Air Traffic Management over Indian Airspace.
• The GAGAN Signal-In-Space (SIS) is available through GSAT-8 and GSAT-10.
• Indian Regional Navigation Satellite System (IRNSS), NavIC is an independent regional navigation satellite system to provide accurate position information service.
• Space Science and Exploration Satellites encompasses research in areas like astronomy, astrophysics, planetary and earth sciences, atmospheric sciences and theoretical physics.
• Eg – Mars Orbiter Mission, AstroSat, Chandrayaan -1,2.
1.3 Launch Vehicles
• Launch Vehicles are used to carry spacecraft to space.
• Following are the various launch vehicles used by ISRO
• Historic launchers - Satellite Launch Vehicle - 3 (SLV-3) and Augmented Satellite Launch Vehicle (ASLV).
• SLV was India's first experimental satellite launch vehicle with solid engines in all 4 stages. ASLV has 3 times augmented capacity of SLV-3.
• Operational launchers - Polar Satellite Launch Vehicle (PSLV) and Geosynchronous Satellite Launch Vehicle (GSLV) and Sounding Rockets.
• Future launchers – GSLV MK-III, Reusable Launch Vehicle (RLV-TD), Scramjet Engine – TD.
PSLV
• It is the3rd generation launch vehicle and first Indian launch vehicle to be equipped with liquid stages.
• PSLV emerged as the reliable and versatile workhorse launch vehicle of India with consecutively successful missions.
• It successfully launched two spacecraft such as Chandrayaan-1 in 2008 and Mars Orbiter Spacecraft in 2013.
• 3 variations in PSLV - PSLV-G (General), PSLV-XL variants and PSLV-CA (Core Alone).
• It has 4 stages in its operation to provide thrust in launching spacecraft to different orbits.
• Stage I: It uses solid rocket motor that is augmented by 6 solid strap-on boosters. Strap on boosters are used only in G and XL variation.
• Stage II: It uses an Earth storable liquid rocket engine, known as the Vikas engine.
• Stage III: It uses solid rocket motor that provides high thrust after the atmospheric phase of the launch.
• Stage IV: It comprises two Earth storable liquid engines.
• Capacity - 1,750 kg of payload to Sun-Synchronous Polar Orbits of 600 km altitude and to 1,425 kg of payload to Geosynchronous and Geostationary orbits, like satellites from the IRNSS constellation.
• PSLV launches in 2018/2019–PSLV - C44/Microsat, Kalamsat ; PSLV – C43/ Hysis ; PSLV – C42/foreign satellites; PSLV – C41/IRNSS-1I ; PSLV - C40/Cartosat-2 series.
GSLV
• It is the 4th generation launch vehicle, a three-stage vehicle with four liquid strap-on boosters.
• GSLV Mk II is the largest launch vehicle developed by India, which is currently in operation.
1. Stage I: It uses solid rocket motor with 4 liquid strap-ons.
2. Stage II: It uses liquid rocket engine (similar to vikas engine of PSLV stage II).
3. Stage III: It uses India’s first cryogenic engine (CE-7.5) in the upper stage. It enabled the launching of 2000 kg of communication satellites.
• Capacity - It can take up to 5000 kg of pay load to Low Earth Orbits, 2500 kg of payload to Geosynchronous Transfer Orbit (GTO) which are primarily INSAT class of communication satellites.
• GSLV Launches in 2018/19 – GSLV – F11/GSAT-7A and GSLV – F08/GSAT – 6A mission.
• The next variant of GSLV is GSLV Mk III, with indigenous high thrust cryogenic engine.
GSLV MK III
• GSLV Mk III is a three-stage heavy lift launch vehicle which has two solid strap-ons, a core liquid booster and a cryogenic upper stage.
• The cryogenic upper stage C25 is powered by CE-20 which is India's largest cryogenic engine.
• It is designed to carry 4000 kg classes of satellites into Geosynchronous Transfer Orbit (GTO) or about 8000 kg classes to Low Earth Orbit (LEO), which is about twice the capability of GSLV Mk II.
• Recent Launches - GSLV Mk III-D2 / GSAT-29, GSLV MK III D1/GSAT – 19 and LVM-3 /CARE (Crew module Atmospheric Re-entry Experiment) mission.
• It is the designated launch vehicle for India’s upcoming second moon mission and the first human space flight scheduled for 2022.
Cryogenic Engine
• Cryogenics is the science that addresses the production and effects of very low temperatures.
• A cryogenic rocket engine uses a cryogenic fuel or oxidizer, which are gases liquefied and stored at very low temperatures.
• Notably, these engines were one of the main factors of NASA's success in reaching the Moon.
• Amongst all rocket fuels, hydrogen is known to provide the maximum thrust.
• But hydrogen, in its natural gaseous form, is difficult to handle, and, therefore, not used in normal engines in rockets like PSLV. However, hydrogen can be used in liquid form.
• The problem is hydrogen liquefies at very low temperature, nearly 250 degrees Celsius below zero.
• To burn this fuel, oxygen also needs to be in liquid form, and that happens at about 90 degrees Celsius below zero.
• Creating such a low-temperature atmosphere in the rocket is a difficult proposition, because it creates problems for other material used in the rocket.
RLV-TD
• Reusable Launch Vehicle – Technology Demonstrator (RLV-TD) is a fully reusable launch vehicle to enable low cost access to space.
• The configuration of RLV-TD is similar to that of an aircraft and combines the complexity of both launch vehicles and aircraft.
• The winged RLV-TD has been configured to act as a flying test bed to evaluate various technologies, namely, hypersonic flight, autonomous landing and powered cruise flight.
• In future, this vehicle will be scaled up to become the first stage of India’s reusable two stage orbital launch vehicle.
• Objectives of RLV-TD - Hypersonic aero thermodynamic characterisation of wing body, Evaluation of autonomous Navigation, Guidance and Control (NGC) schemes, Integrated flight management and Thermal Protection System Evaluation
• It was successfully flight tested in 2016 from Sriharikota.
Scramjet Engine - TD
• Usually, launch vehicles carry oxidiser along with the fuel for combustion to produce thrust to launch satellites into orbit.
• Nearly, 70% of the propellant (fuel – oxidiser) by weight consists of oxidiser which makes it to carry only 2-4% of their lift-off mass to orbit.
• Therefore, air-breathing propulsion system which can utilise the atmospheric oxygen during their flight and reduce the total propellant required to place a satellite in orbit is being developed by various space agencies.
• Ramjet, Scramjet and Dual Mode Ramjet (DMRJ) are the three concepts of air-breathing engines.
• A ramjet is a form of air-breathing jet engine that uses the vehicle’s forward motion to compress incoming air for combustion without a rotating compressor.
• Fuel is injected in the combustion chamber where it mixes with the hot compressed air and ignites.
• It works most efficiently at supersonic speeds around Mach 3 (three times the speed of sound) and can operate up to speeds of Mach 6.
• However, the ramjet efficiency starts to drop when the vehicle reaches hypersonic speeds.
• A scramjet engine is an improvement over the ramjet engine as it efficiently operates at hypersonic speeds and allows supersonic combustion. Thus, it is known as Supersonic Combustion Ramjet, or Scramjet.
• A dual mode ramjet (DMRJ) is a type of jet engine where a ramjet transforms into scramjet over Mach 4-8 range, which means it can efficiently operate both in subsonic and supersonic combustor modes.
• ISRO’s Advanced Technology Vehicle (ATV), which is an advanced sounding rocket, was the solid rocket booster used for test of Scramjet engines at supersonic conditions.
• ATV is a two- stage solid launch vehicle capable of carrying Scramjet engines weighed 3277 kg at lift-off.
• India is the fourth country (after USA, Russia and European Space Agency ) to demonstrate the flight testing of a Scramjet Engine.
Small Satellite Launch Vehicle
• ISRO has completed the design of baby rocket “Small Satellite Launch Vehicle (SSLV)”.
• SSLV can place a 500 kg payload at a height of 500 km in the Low Earth Orbit (LEO).
• It has three solid motor stages with a lift off mass of 120 tonnes.
• It is shorter in length than the PSLV and GSLV.
• It can accommodate multiple satellites like the PSLV and GSLV, albeit smaller ones.
• Unlike the PSLV and GSLV, the SSLV can be assembled both vertically and horizontally.
Vikas Engine
• Vikas is a family of liquid fuelled rocket engines that powers India’s launch vehicles PSLV and GSLV.
• It is aimed at improving the payload capability of PSLV, GSLV and GSLV Mk-III launch vehicles.
• It is used in second stage of PSLV which consists of four stages in its operation (Solid-Liquid-Solid-Liquid) and in second stage and four strap-on stages of GSLV.
• GSLV is a three-stage vehicle (Solid-Liquid-Cryogenic Engine) with four liquid strap-on boosters.
• ISRO has recently improved the thrust of the Vikas engine which is expected to boost the rocket engine.
• The main beneficiary of the high-thrust Vikas engine is GSLV-Mark III launcher, which is expected to lift 4,000-kg satellites to space.
• GSLV-Mark III uses twin engine core liquid stage (L110).
• GSLV – Mark III with upgraded Vikas engine would be the third Mk-III and the first working one to be designated MkIII Mission-1 or M1.
Indian Missions
1.4 PSLV C-44/Kalamsat
• PSLV C-44 has successfully injected Microsat-R and Kalamsat-V2 satellites into their designated orbits from Sriharikota.
• It is a new variant of PSLV called PSLV-DL (D standing for demonstration).
• In its normal configuration, the rocket will have six strap-on motors in the first stage.
• However, PSLV-DL will have just two strap-on motors for the first time.
• In a normal launch vehicle, each stage falls off after fuel completes burn-off.
• However, stage four, after releasing the payload, wanders around in space as junk.
• PSLV-DL will follow the same pattern, except that the fourth stage (PS4) won’t fall off.
• It will serve as a platform for the satellite like deploying solar panels or other tools to aid the satellite.
• Kalamsat is the first satellite to use PS4 as an orbital platform, thus reducing space debris.
• It is a 10cm cube communication nano-satellite weighing about 1.2kg designed by students.
• Its life span is about two months and its cost is about Rs. 12 lakh.
• A 64-gram version of the Kalamsat nicknamed "gulab jamun" was launched by NASA in 2017. But it never reached orbit.
• Microsat-R is a 130-kg military imaging satellite.It was put together by a handful of DRDO laboratories.
1.5 PSLV C-43/HysIS
• It has successfully launched India’s first Hyper spectral Imaging Satellite (HysIS) and 30 international co-passenger satellites.
• PSLV-C43 is the Core Alone version of PSLV, without the six strap-ons.
• HysIS is an earth observation satellite, weighing about 380 kg and configured around ISRO’s Mini Satellite-2 (IMS-2) bus.
• The goal is to study the earth’s surface in the visible, near infrared and shortwave infrared regions of the electromagnetic spectrum.
• It has a mission life of about 5 years.
• A hyperspectral imaging camera in space can provide well-defined images that can help to identify objects on Earth far more clearly than regular optical or remote sensing cameras.
• The technology will be an added advantage of watching over India from space for a variety of purposes such as defense, agriculture, land use, minerals and so on.
1.6 HySIS
• Hyperspectral Imaging Satellite (HySIS) is a full-fledged earth observation satellite, going to be launched by ISRO.
• Hyperspectral or Hyspex imaging enables distinct identification of objects on earth by reading the spectrum for each pixel of a scene from space.
• The satellite has the Hyperspectral imager which can identify 55 spectral or colour bands from 630 km above ground.
• It can be used for monitoring of environment, finding oil and minerals apart from military surveillance.
• Hyspex was first tried out in Chandrayaan-1 mission which mapped the lunar mineral resources.
1.7 PSLV C-42
• It has launched two foreign satellites - NovaSAR and S1-4 of United Kingdom.
• PSLV C-42 is also a Core Alone version of PSLV, without the six strap-ons.
• Both satellites are earth observation systems and injected in Sun Synchronous Orbit.
• NovaSAR is a S-Band Synthetic Aperture Radar satellite intended for forest mapping, land use & ice cover monitoring, flood & disaster monitoring.
• S1-4 is a high-resolution Optical Earth Observation Satellite, used for surveying resources, environment monitoring, urban management and for the disaster monitoring.
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