Subject: Space Technology

In a few weeks’ time, the Indian Space Research Organisation (ISRO) hopes to achieve a remarkable feat — the 200th successful launch of the Rohini RH-200 sounding rocket in a row.

Rohini RH-200

• RH-200 is a two-stage rocket capable of climbing to a height of 70 km bearing scientific payloads.
• The first and second stages of RH-200 are powered by solid motors. The ‘200’ in the name denotes the diameter of the rocket in mm.
• Other operational Rohini variants are RH-300 Mk-II and RH-560 Mk-III.
• For years, the RH-200 rocket had used a polyvinyl chloride (PVC)-based propellant.
• The first RH-200 to use a new propellant based on hydroxyl-terminated Polybutadiene (HTPB) was successfully flown from the TERLS in September 2020.
• The first and second stages of RH200 rocket are powered by solid motors.
• Since inception of RH200 rocket, both solid stages are processed using polyvinyl chloride (PVC) based propellant.
• As compared to PVC based propellants, HTPB based propellant is more energetic, higher mechanical & interface properties and has less defects due to lower processing temperature.

What basically is a Sounding Rocket?

• A sounding rocket is an instrument-carrying rocket designed to take measurements and perform scientific experiments during its sub-orbital flight.
• The rockets are used to launch instruments from 48 to 145 km above the surface of the Earth, the altitude generally between weather balloons and satellites.
• The maximum altitude for balloons is about 40 km and the minimum for satellites is approximately 121 km.

History of sounding rockets in India

• Sounding rockets have an important place in the ISRO story.
• The first sounding rocket to be launched from Thumba was the American Nike-Apache — on November 21, 1963.
• After that, two-stage rockets imported from Russia (M-100) and France (Centaure) were flown. The ISRO launched its own version — Rohini RH-75 — in 1967.
• The ISRO has launched more than 1,600 RH-200 rockets so far.
• Currently, the RH200, RH300 MkII and RH560 Mk-III rockets are operational which were developed during the early phase of our journey in rocketry.

 

UPSC 2023 countdown has begun! Get your personal guidance plan now! (Click here)

In the first-of-its kind NASA’s DART Mission is about to hit a small, harmless asteroid millions of miles away.

What is DART Mission?

• The main aim of the mission is to test the newly developed technology that would allow a spacecraft to crash into an asteroid and change its course.
• It is a suicide mission and the spacecraft will be completely destroyed.
• The target of the spacecraft is a small moonlet called Dimorphos (Greek for “two forms”).
• It is about 160-metre in diameter and the spacecraft is expected to collide when it is 11 million kilometres away from Earth.
• Dimorphos orbits a larger asteroid named Didymos (Greek for “twin”) which has a diameter of 780 metres.

Why Dimorphos?

• Didymos is a perfect system for the test mission because it is an eclipsing binary which means it has a moonlet that regularly orbits the asteroid.
• It is observable when it passes in front of the main asteroid.
• Earth-based telescopes can study this variation in brightness to understand how long it takes Dimorphos to orbit Didymos.

Collision course

• At the time of impact, Didymos and Dimorphos will be relatively close to Earth – within 6.8 million miles (11 million kilometers).
• The spacecraft will accelerate at about 24,140 kilometers per hour when it collides with Dimorphos.
• It aims to crash into Dimorphos to change the asteroid’s motion in space.
• This collision will be recorded by LICIACube, or Light Italian CubeSat for Imaging of Asteroids, a companion cube satellite provided by the Italian Space Agency.
• Three minutes after impact, the CubeSat will fly by Dimorphos to capture images and video.

Why such mission?

• Dimorphos was chosen for this mission because its size is relative to asteroids that could pose a threat to Earth.
• The spacecraft is about 100 times smaller than Dimorphos, so it won’t obliterate the asteroid.
• The fast impact will only change Dimorphos’ speed as it orbits Didymos by 1%, which doesn’t sound like a lot — but it will change the moon’s orbital period.

 

UPSC 2023 countdown has begun! Get your personal guidance plan now! (Click here)

In a first-of-its-kind initiative, the Department of Science & Technology (DST) has announced the setting up of India’s first dark sky reserve at Hanle in Ladakh in the next three months.

What is a Dark Sky Reserve?

• A dark-sky reserve is an area, usually surrounding a park or observatory that is kept free of artificial light pollution.
• The purpose of a dark sky preserve is generally to promote astronomy.
• Because different national organizations have worked independently to create their programs, different terms have been used to describe the areas.

How is it designated?

• A dark sky reserve is a designation given to a place that has policies in place to ensure that a tract of land or region has minimal artificial light interference.
• The International Dark Sky Association is a US-based non-profit that designates sites as international dark sky places, parks, sanctuaries and reserves, depending on the criteria they meet.
• Several such reserves exist around the world but none so far in India.

Dark Sky Reserve at Hanle

• Hanle, which is about 4,500 metres above sea level, hosts telescopes and is regarded as one of the world’s most optimal sites for astronomical observations.
• However, ensuring that the site remains well-suited for astronomy implies keeping the night sky pristine, or ensuring minimal interference to the telescopes from artificial light sources such as electric lights and vehicular lights from the ground.
• The site will have activities to help in boosting local tourism and economy through interventions of science and technology.

The Himalayan Chandra Telescope, High Energy Gamma Ray Telescope, Major Atmospheric Cherenkov Experiment Telescope and GROWTH-India are the prominent telescopes located at the Hanle observatory.

Ideal conditions in India

• The Indian Astronomical Observatory, the high-altitude station of the IIA, is situated to the north of Western Himalayas, at an altitude of 4,500 metres above mean sea level.
• Located atop Mt. Saraswati in the Nilamkhul Plain in the Hanle Valley of Changthang, it is a dry, cold desert with sparse human population.
• The cloudless skies and low atmospheric water vapour make it one of the best sites in the world for optical, infrared, sub-millimetre, and millimetre wavelengths.

 

UPSC 2023 countdown has begun! Get your personal guidance plan now! (Click here)

NASA’s Artemis 1 mission has sought unexpected delay due to fuel leakages issue.

What is the Artemis I Mission?

• NASA’s Artemis mission is touted as the next generation of lunar exploration, and is named after the twin sister of Apollo from Greek mythology.
• Artemis is also the goddess of the moon.
• Artemis I is the first of NASA’s deep space exploration systems.
• It is an uncrewed space mission where the spacecraft will launch on SLS — the most powerful rocket in the world — and travel 2,80,000 miles from the earth for over four to six weeks during the course of the mission.
• The Orion spacecraft is going to remain in space without docking to a space station, longer than any ship for astronauts has ever done before.
• The SLS rocket has been designed for space missions beyond the low-earth orbit and can carry crew or cargo to the moon and beyond.

Key objectives of the mission

• With the Artemis Mission, NASA aims to land humans on the moon by 2024, and it also plans to land the first woman and first person of colour on the moon.
• With this mission, NASA aims to contribute to scientific discovery and economic benefits and inspire a new generation of explorers.
• NASA will establish an Artemis Base Camp on the surface and a gateway in the lunar orbit to aid exploration by robots and astronauts.
• The gateway is a critical component of NASA’s sustainable lunar operations and will serve as a multi-purpose outpost orbiting the moon.

Other agencies involved

• Other space agencies are also involved in the Artemis programme.
• The Canadian Space Agency has committed to providing advanced robotics for the gateway.
• The European Space Agency will provide the International Habitat and the ESPRIT module, which will deliver additional communications capabilities among other things.
• The Japan Aerospace Exploration Agency plans to contribute habitation components and logistics resupply.

 

UPSC 2023 countdown has begun! Get your personal guidance plan now! (Click here)

 

The Indian Space Research Organisation (ISRO) has said that the satellite onboard its’ maiden Small Satellite Launch Vehicle “are no longer usable” after the SSLV-D1 placed them in an elliptical orbit instead of a circular one.

What is SSLV?

• The SSLV is a small-lift launch vehicle being developed by the ISRO with payload capacity to deliver:

1. 600 kg to Low Earth Orbit (500 km) or
2. 300 kg to Sun-synchronous Orbit (500 km)

• It would help launching small satellites, with the capability to support multiple orbital drop-offs.
• In future a dedicated launch pad in Sriharikota called Small Satellite Launch Complex (SSLC) will be set up.
• A new spaceport, under development, near Kulasekharapatnam in Tamil Nadu will handle SSLV launches when complete.
• After entering the operational phase, the vehicle’s production and launch operations will be done by a consortium of Indian firms along with NewSpace India Limited (NSIL).

Vehicle details

(A) Dimensions

• Height: 34 meters
• Diameter: 2 meters
• Mass: 120 tonnes

(B) Propulsion

• It will be a four stage launching vehicle.
• The first three stages will use Hydroxyl-terminated polybutadiene (HTPB) based solid propellant, with a fourth terminal stage being a Velocity-Trimming Module (VTM).

SSLV vs. PSLV: A comparison

• The SSLV was developed with the aim of launching small satellites commercially at drastically reduced price and higher launch rate as compared to Polar SLV (PSLV).
• The projected high launch rate relies on largely autonomous launch operation and on overall simple logistics.
• To compare, a PSLV launch involves 600 officials while SSLV launch operations would be managed by a small team of about six people.
• The launch readiness period of the SSLV is expected to be less than a week instead of months.
• The SSLV can carry satellites weighing up to 500 kg to a low earth orbit while the tried and tested PSLV can launch satellites weighing in the range of 1000 kg.
• The entire job will be done in a very short time and the cost will be only around Rs 30 crore for SSLV.

Significance of SSLV

• SSLV is perfectly suited for launching multiple microsatellites at a time and supports multiple orbital drop-offs.
• The development and manufacture of the SSLV are expected to create greater synergy between the space sector and private Indian industries – a key aim of the space ministry.

---

Back2Basics: Various Orbits of Satellites

[1] Geostationary orbit (GEO)

• Satellites in geostationary orbit (GEO) circle Earth above the equator from west to east following Earth’s rotation – taking 23 hours 56 minutes and 4 seconds – by travelling at exactly the same rate as Earth.
• This makes satellites in GEO appear to be ‘stationary’ over a fixed position.
• In order to perfectly match Earth’s rotation, the speed of GEO satellites should be about 3 km per second at an altitude of 35 786 km.
• This is much farther from Earth’s surface compared to many satellites.
• GEO is used by satellites that need to stay constantly above one particular place over Earth, such as telecommunication satellites.
• Satellites in GEO cover a large range of Earth so as few as three equally-spaced satellites can provide near-global coverage.

[2] Low Earth orbit (LEO)

• A low Earth orbit (LEO) is, as the name suggests, an orbit that is relatively close to Earth’s surface.
• It is normally at an altitude of less than 1000 km but could be as low as 160 km above Earth – which is low compared to other orbits, but still very far above Earth’s surface.
• Unlike satellites in GEO that must always orbit along Earth’s equator, LEO satellites do not always have to follow a particular path around Earth in the same way – their plane can be tilted.
• This means there are more available routes for satellites in LEO, which is one of the reasons why LEO is a very commonly used orbit.
• It is most commonly used for satellite imaging, as being near the surface allows it to take images of higher resolution.
• Satellites in this orbit travel at a speed of around 7.8 km per second; at this speed, a satellite takes approximately 90 minutes to circle Earth.

[3] Medium Earth orbit (MEO)

• Medium Earth orbit comprises a wide range of orbits anywhere between LEO and GEO.
• It is similar to LEO in that it also does not need to take specific paths around Earth, and it is used by a variety of satellites with many different applications.
• It is very commonly used by navigation satellites, like the European Galileo system of Europe.
• It uses a constellation of multiple satellites to provide coverage across large parts of the world all at once.

[4] Polar Orbit

• Satellites in polar orbits usually travel past Earth from north to south rather than from west to east, passing roughly over Earth’s poles.
• Satellites in a polar orbit do not have to pass the North and South Pole precisely; even a deviation within 20 to 30 degrees is still classed as a polar orbit.
• Polar orbits are a type of low Earth orbit, as they are at low altitudes between 200 to 1000 km.

[5] Sun-synchronous orbit (SSO)

• SSO is a particular kind of polar orbit. Satellites in SSO, travelling over the polar regions, are synchronous with the Sun.
• This means they are synchronised to always be in the same ‘fixed’ position relative to the Sun.
• This means that the satellite always visits the same spot at the same local time.
• Often, satellites in SSO are synchronised so that they are in constant dawn or dusk – this is because by constantly riding a sunset or sunrise, they will never have the Sun at an angle where the Earth shadows them.
• A satellite in a Sun-synchronous orbit would usually be at an altitude of between 600 to 800 km. At 800 km, it will be travelling at a speed of approximately 7.5 km per second.

[6] Transfer orbits and geostationary transfer orbit (GTO)

• Transfer orbits are a special kind of orbit used to get from one orbit to another.
• Often, the satellites are instead placed on a transfer orbit: an orbit where, by using relatively little energy from built-in motors, the satellite or spacecraft can move from one orbit to another.
• This allows a satellite to reach, for example, a high-altitude orbit like GEO without actually needing the launch vehicle.
• Reaching GEO in this way is an example of one of the most common transfer orbits, called the geostationary transfer orbit (GTO).

 

UPSC 2023 countdown has begun! Get your personal guidance plan now! (Click here)