GS Paper 3

Context: Plasma Analyser Package for Aditya (PAPA) payload onboard Indian Space Research Organisation’s (ISRO) Aditya-L1 has detected the impact of coronal mass ejections (CMEs) on solar wind. 

• Aditya-L1 is India's first solar mission aimed at studying the sun from a distance of about 1.5 million km from the Earth. It has seven payloads, including Plasma Analyser Package for Aditya. 
• CMEs can disrupt the solar wind and cause disturbances in Earth's magnetic field, leading to geomagnetic storms that can damage systems on Earth's surface and near-Earth. 

Plasma Analyser Package for Aditya (PAPA):

• PAPA is an energy and mass analyser designed for in-situ measurements of solar wind electrons and ions in the low energy range.
  • Solar wind is a stream of charged particles (protons, electrons, and alpha particles) flowing outward from the Sun at high speeds. 
• It has two sensors which can measure the mass, energy distribution, and even the direction of arrival of solar wind particles.
  • Solar Wind Electron Energy Probe (SWEEP, measuring electrons in the energy range of 10 eV to 3 keV)
  • Solar Wind Ion Composition Analyser (SWICAR, measuring ions in the energy range of 10 eV to 25 keV and mass range of 1-60 amu). 

Coronal Mass Ejections (CME):

• CMEs are large bursts/expulsions of plasma and magnetic fields that can erupt from the Sun’s corona and cause significant disturbances in the solar wind.
• Compared to solar flares (bursts of electromagnetic radiation that travel at the speed of light), CMEs travel at a more leisurely pace with their highest speeds reaching 3,000 kilometres per second. These relatively slower travel times may give more time to prepare for such an arrival.
• Impacts of CMEs on Earth: 
  • CMEs can produce a geomagnetic storm which in turn can disrupt power grids, telecommunication networks and orbiting satellites, disrupt radio communication and expose astronauts to dangerous doses of radiation.
  • Charged particles from CMEs can interact with Earth's atmosphere near the poles, and produce colourful displays of light known as auroras or the northern and southern lights.

Key Terms:

• Solar Flares: Solar flares are intense bursts of energy and light that originate from the Sun's surface. They are caused by the release of magnetic energy stored in the Sun's atmosphere.
• Solar Wind/Storm: Solar wind is created by the outward expansion of plasma (a collection of charged particles) from the Sun's corona (outermost atmosphere). This plasma is continually heated to the point that the Sun's gravity cannot hold it down. It then travels along the Sun's magnetic field lines that extend radially outward.
• Geomagnetic storms: A geomagnetic storm is a disturbance in the Earth's magnetic field caused when a solar wind shock wave or cloud of the magnetic field interacts with the Earth's magnetic field. 

Comparison between Solar winds, Solar flares and Coronal Mass Ejections: 

Context: In a major milestone for India’s space sector, Indian Space Research Organisation (ISRO) has accomplished the human rating of its cryogenic engine (CE-20), which powers the cryogenic stage of the human-rated LVM3 launcher for India’s first human space flight mission Gaganyaan.  

• Human-rating refers to rating a system that is capable of safely transporting humans.

Major Highlights: 

• The ground qualification tests for the human rating of the CE-20 engine involved life demonstration tests, endurance tests and performance assessment under nominal operating conditions as well as off-nominal conditions with respect to thrust, mixture ratio and propellant tank pressure. 
• ISRO has also successfully completed the acceptance tests of the flight engine identified for Gaganyaan mission, tentatively scheduled for the second quarter of 2024. The engine will power the upper stage of the human-rated LVM3 vehicle and has a thrust capability of 19 to 22 tonnes with a specific impulse of 442.5 seconds.

Gaganyaan Mission: 

• The Gaganyaan project envisages demonstration of human spaceflight capability by launching a crew of three members to an orbit of 400 km for a three-day mission, and bring them back safely to the Earth, by landing in the sea. 
• Launcher: Launch Vehicle Mark-3 (LVM3/ GSLV Mk III).

Launch Vehicle Mark-3:  

• Launch Vehicle Mark-3 or LVM3 (previously referred as the Geosynchronous Satellite Launch Vehicle Mark III or GSLV Mk III) is a three-stage medium-lift launch vehicle developed by the Indian Space Research Organisation (ISRO).
• Stages: GSLV Mk III is a three-staged launch vehicle.
  • First stage- Solid fuel S200 stage. Two rocket boosters use 200 tonnes of solid fuel to lift off the rocket.
  • Second stage- Liquid fuel L110 stage. 
  • Third stage- Cryogenic fuel C25 stage uses 25 tonnes of a mixture of liquid hydrogen and liquid oxygen.
    • This upper stage, developed entirely in India, uses the CE-20 cryogenic engine. 
    • This high-thrust engine burns liquid hydrogen and liquid oxygen at very low temperatures for exceptional efficiency and payload capacity.
• Primarily designed to launch communication satellites into geostationary orbit. It is also due to launch crewed missions under the Indian Human Spaceflight Programme (Gaganyaan Mision).
• The LVM3 is one of the most powerful rockets in ISRO's fleet, and it is capable of launching heavier payloads than its predecessors (GSLV-MKII).
  • Payload capacity:
    • 4,000 kilograms to geosynchronous transfer orbit (GTO).
    • 10,000 kilograms to low Earth orbit (LEO).

Indigenous cryogenic engine technology in India: 

• India has managed to develop its own cryogenic engine, a result of decades of research and development. This engine has an entirely Indian design, developed within ISRO, and uses a different process to burn the fuel. 
• This indigenously developed cryogenic engine is deployed in LVM3, ISRO’s most powerful rocket so far, which carried the Chandrayaan-2 and Chandrayaan-3 missions, among others. LVM3 has had seven flights till now, without any trouble. 

Some important reasons why cryogenic engines are used in rockets:

• High specific impulse: Cryogenic engines use liquid hydrogen and liquid oxygen as propellants. These propellants are stored at extremely low temperatures (around -253°C for hydrogen and -183°C for oxygen), which gives them a high energy density, i.e, they pack a lot of energy in a small amount of mass.
  • When these propellants burn, they release a lot of energy compared to their mass, or have high specific impulse. 
  • High specific impulse means more thrust per kilogram of propellant (High thrust to weight ratio). This allows rockets to carry less fuel, reducing their overall weight and allowing them to carry heavier payloads or travel further. Higher thrust is beneficial for:
    • Overcoming Earth's gravity: Launching a rocket out of Earth's gravity well requires immense thrust. Cryogenic engines provide the necessary power to achieve this initial escape velocity.
    • Manoeuvring in space: Once in space, cryogenic engines allow for precise manoeuvring and course corrections due to their high thrust and controllability. 
• Throttling Capability: Cryogenic engines are designed to be throttleable, i.e., they have the ability to vary or adjust their thrust levels during flight. This capability is essential for precise control during ascent, orbit insertion, manoeuvring, controlled reentry and other critical phases of a rocket’s journey.
• Greater fuel efficiency: The combustion process in cryogenic engines is cleaner and more complete, releasing more energy and generating more thrust. Rockets with cryogenic engines need less fuel to achieve the same results, making them more cost-effective.

Challenges: 

• Complexity: They require complex and expensive infrastructure to store and handle extremely cold propellants.
• Cost: The initial development process of cryogenic engines is generally more expensive than other types.

Context: Astronomers have finally found a unique class of stars (Helium stars) they had been looking for, for a decade.

How do stars sustain? 

• Stars are giant balls of hot gas – mostly hydrogen, with some helium and small amounts of other elements. Every star has its own life cycle, ranging from a few million to trillions of years, and its properties change as it ages.
• Newton’s law of gravity says all objects with mass attract each other. This should mean the Sun’s outer and inner layers should be attracted to each other, so the star should continuously fall inwards, and eventually simply collapse. However, the sun does not collapse as the nuclear fusion prevents the Sun from shrinking.
  • In the heart of the star, two hydrogen nuclei (protons) ultimately combine to form one helium nucleus, releasing enormous amounts of heat and energy in the form of gamma rays and neutrinos.
  • This energy endows all particles in the star with random motion, or pressure, which then fights against the pull of gravity and maintains the star in a state of equilibrium.
• The fusion energy pushes the star out while gravity pulls it in, and they hold the balance for billions of years. Such stars are said to be in the main sequence. 

Hydrogen devoid stars (Helium stars): 

• When a star no longer fuses material and allows gravity to gain the upper hand, it blows up in an explosion called a supernova when it is massive enough.
  • The light from supernovae contains signatures of the various elements it has passed through near the dying star’s surface.
  • Scientists have observed that some supernovae have shown no signs of hydrogen. (Hydrogen, the lightest of elements, makes up the outer layers of main-sequence stars). The only explanation is that the outer layers of some stars are stripped away before the supernova explosion. 
• An interesting mechanism happens if the star is part of a binary system — i.e. as one of two stars that are orbiting each other. (Most stars heavier than the Sun are in such binaries). Many binary systems start out with two main sequence stars. The gravitational attraction of one star can peel away the hydrogen layer off the other, resulting in one helium star and one main sequence companion. 
• Helium stars are Hydrogen depleted stars. They have a core of helium and their outer layers are stripped of Hydrogen. They are roughly 8-20 times the mass of our Sun and their surface gravity is about 1,000-times that of the earth. Helium stars are expected to be so hot that they emit more of their energy as ultraviolet radiation, which lies beyond the visible range.
  • These Helium stars will end their lives as hydrogen-poor supernovae that leave behind ultra-dense balls called neutron stars. 
  • And these neutron stars may ultimately smash into each other in powerful kilonova explosions, releasing gravitational waves.