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Tamil Nadu Board of Secondary EducationSSLC (English Medium) Class 8

Revision: Universe and Space Science Science SSLC (English Medium) Class 8 Tamil Nadu Board of Secondary Education

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Key Points

Key Points: Satellite Launch Vehicles
  • Satellite launch vehicles work on Newton’s third law—expelling gas creates thrust to lift the rocket.
  • Launch vehicles use multiple stages to reduce weight and increase speed as they rise.
  • Fuel type and structure of launch vehicles depend on the satellite’s weight and target orbit.
  • PSLV (by ISRO) is a multi-stage launch vehicle used to place satellites in orbit.
  • Unlike rockets, reusable space shuttles (such as NASA's) can return and be reused.
Key Points: Space Missions
  • Space missions are of two types: launching satellites around Earth and exploring space objects beyond Earth.
  • Yuri Gagarin was the first human in space (1961), and Neil Armstrong was the first on the Moon (1969).
  • Indian space explorers include Rakesh Sharma, Kalpana Chawla, and Sunita Williams.
  • Space technology enables fast global communication, internet access, and early warning of natural disasters.
  • Satellites support defence, surveillance, weather forecasting, and the location of natural resources, making space tech vital for national development.
 
Key Points: Moon Missions
  • Since the Moon is the closest celestial body, it became the first target of space missions in the solar system.
  • The Soviet Union’s Luna‑2 (1959) was the first spacecraft to reach the Moon; later Luna missions studied its composition, gravity, and radiation.
  • Some unmanned Soviet missions successfully landed on the Moon and returned rock samples to Earth.
  • The USA conducted manned Moon missions, and in 1969, Neil Armstrong became the first human to walk on the Moon.
  • India’s Chandrayaan‑1 (2008) discovered the presence of water on the Moon, making India the first country to do so.
Key Points: Mars Missions
  • Mars Mission (Mangalyaan) by ISRO was launched in 2013 and successfully entered Mars orbit in 2014.
  • It was a low-cost mission that provided important data on Mars' surface and atmosphere.
  • Rakesh Sharma was the first Indian in space (1984), and stayed 8 days under the Indo-USSR program.
  • Kalpana Chawla spent 336 hours in space but died in 2003 during the Columbia shuttle disaster.
  • Sunita Williams worked 29 hours outside the space station and spent 192 days in space, setting a record.
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