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Science and Technology for AP Exams · Chapter 3

Space Technology and Defence

What to remember

  • Launch vehicles: SLV and ASLV were early rockets; PSLV is the workhorse; GSLV uses a cryogenic upper stage; LVM3 (earlier GSLV Mk III) is the heaviest.
  • Satellites: communication satellites sit in geostationary orbit; remote sensing satellites use sun-synchronous polar orbit; NavIC is India's regional navigation system.
  • Defence: DRDO developed the Prithvi, Agni, Akash, Nag and BrahMos missiles. The nuclear triad means delivery from land, air and sea.

ISRO: a short history

The Indian National Committee for Space Research (INCOSPAR) was formed in 1962 under Vikram Sarabhai. India's first rocket launch took place from Thumba in Kerala, which became a rocket launching station for sounding rockets. ISRO was formed in 1969, and the Department of Space and the Space Commission were created in 1972. Aryabhata was India's first satellite, launched with foreign help. Rohini was the first satellite launched by an Indian rocket, the SLV-3. Later came the APPLE experimental communication satellite and Bhaskara remote sensing satellites.

ISRO centres: Vikram Sarabhai Space Centre (Thiruvananthapuram) for launch vehicles; U. R. Rao Satellite Centre (Bengaluru) for satellites; Space Applications Centre (Ahmedabad) for payloads and applications; Liquid Propulsion Systems Centre for liquid engines; National Remote Sensing Centre (Hyderabad) for remote sensing data; ISRO Telemetry, Tracking and Command Network (Bengaluru) for tracking. IN-SPACe (created 2020) authorises and promotes private space activity, and NewSpace India Limited is the commercial arm.

Sriharikota

The Satish Dhawan Space Centre, Sriharikota (SHAR) is India's main spaceport. It lies on an island off the Andhra Pradesh coast, near Pulicat Lake. Its location near the equator helps a rocket use the earth's eastward rotation, and the sea around it keeps populated areas safe. It has launch pads for PSLV, GSLV and LVM3. A second launch complex for small satellites is also being developed in Tamil Nadu at Kulasekarapattinam.

Launch vehicles

VehicleKey facts
SLVFirst Indian launch vehicle, four stages, solid fuel
ASLVAugmented version for heavier payloads
PSLVFour stages (solid, liquid, solid, liquid); puts satellites in polar sun-synchronous orbit; used for Chandrayaan-1, Mangalyaan, Aditya-L1
GSLV Mk IIThree stages with an indigenous cryogenic upper stage; for geosynchronous transfer orbit
LVM3Earlier called GSLV Mk III; three stages with two solid boosters, a liquid core and a cryogenic stage; used for Chandrayaan-3
SSLVSmall Satellite Launch Vehicle for small payloads on demand

A cryogenic engine burns liquid hydrogen and liquid oxygen at very low temperature and gives high thrust per unit of fuel. India developed its own cryogenic engine after earlier technology access was denied.

Satellites and orbits

  • Communication satellites: INSAT and GSAT series, placed in geostationary orbit at about 36,000 km above the equator. They carry TV, telephone, broadband and disaster warning services.
  • Remote sensing satellites: IRS series, Cartosat (high-resolution mapping), Resourcesat, Oceansat and RISAT (radar imaging that works through cloud and at night). They are placed in low polar sun-synchronous orbit, at about 500 to 900 km.
  • Navigation: NavIC (Navigation with Indian Constellation), earlier called IRNSS, is a regional navigation system covering India and nearby areas.
  • Science: AstroSat is India's first dedicated multi-wavelength space observatory.
  • Orbits: low earth orbit (LEO), medium earth orbit (MEO), geostationary orbit (GEO), sun-synchronous orbit (SSO).
OrbitHeightUse
LEOUp to about 2,000 kmEarth observation, space station
SSOAround 500-900 kmRemote sensing
GEOAbout 36,000 kmCommunication, weather

Space missions (milestones only)

  • Chandrayaan-1: India's first lunar mission, an orbiter that carried the Moon Impact Probe; it helped confirm water molecules on the Moon.
  • Mangalyaan (Mars Orbiter Mission): India's first interplanetary mission, launched by PSLV. India became the first country to reach Mars orbit in its first attempt and the first in Asia to do so.
  • Chandrayaan-2: orbiter works; the lander did not complete a soft landing.
  • Chandrayaan-3: launched by LVM3; the lander (Vikram) and rover (Pragyan) made India the fourth country to land softly on the Moon and the first near the lunar south pole region.
  • Aditya-L1: India's first solar observatory, placed at the Sun-Earth Lagrange point L1.
  • Gaganyaan: India's human spaceflight programme to send astronauts to low earth orbit and bring them back.
  • SpaDeX: a mission to demonstrate docking of two satellites in orbit.

Defence technology

DRDO works through many laboratories. The Integrated Guided Missile Development Programme (IGMDP), led by A. P. J. Abdul Kalam, produced five missile systems.

MissileType
PrithviSurface-to-surface, short range
Agni seriesSurface-to-surface ballistic missiles, from intermediate to long range
AkashSurface-to-air, medium range
TrishulShort-range surface-to-air
NagAnti-tank guided missile
BrahMosSupersonic cruise missile, made with Russia; can be launched from land, sea, air
Sagarika (K-15) and K-4Submarine-launched ballistic missiles

Other defence projects: Tejas light combat aircraft (HAL), Arjun main battle tank, INS Vikrant (an indigenous aircraft carrier), and INS Arihant (nuclear-powered ballistic missile submarine, built at Visakhapatnam). Missile tests are often done at test ranges off the Odisha coast.

Nuclear triad

A nuclear triad is the capability to deliver nuclear weapons from land (ballistic missiles like Agni), air (aircraft) and sea (submarines such as INS Arihant with K-series missiles). It makes a second strike possible. India follows a policy of credible minimum deterrence and No First Use. India's tests at Pokhran took place in 1974 and 1998.

Missile classes and basic terms

A ballistic missile follows a high arc after a powered launch and then falls freely. A cruise missile flies at low level with its own engine and can change course. Range classes are short, medium, intermediate and long. Surface-to-air missiles defend against aircraft and missiles. Anti-tank guided missiles hit armoured vehicles. MIRV means one missile carries several warheads that can hit different targets. A solid-fuel missile can be launched quickly, while a liquid-fuel missile needs fuelling before launch. A ramjet engine, used in BrahMos, works at high speed by compressing air with the forward motion of the vehicle. Supersonic means faster than sound, and hypersonic means more than five times the speed of sound.

Uses of space technology

Satellites help in weather forecasting, cyclone tracking, fishing zone advice, crop and land mapping, groundwater study, telemedicine, tele-education, disaster management and navigation. Andhra Pradesh, with a long coast, depends on cyclone warnings and ocean information from satellites. Communication satellites bring TV, internet and banking to remote regions. Navigation signals guide ships, aircraft, farmers and vehicles. Remote sensing data from the National Remote Sensing Centre helps in land and water planning.

Space policy and private role

Space activity was long run only by the government. Reforms in 2020 opened the sector to private firms and start-ups. IN-SPACe gives authorisation, and NewSpace India Limited handles commercial services. Private companies now build small launch vehicles and satellites. This lowers cost and increases the number of launches. ISRO continues to focus on research, human spaceflight and exploration.

Defence organisation in brief

The Ministry of Defence manages the Army, Navy and Air Force. The Chief of Defence Staff coordinates the three services. The Strategic Forces Command looks after nuclear forces. DRDO designs systems, Hindustan Aeronautics Limited (HAL) builds aircraft, and Bharat Dynamics Limited builds missiles. The government encourages indigenous production under Make in India, through defence corridors and positive lists of items for local purchase. Visakhapatnam hosts the Eastern Naval Command and a naval shipbuilding centre.

Key terms in rocket science

Thrust is the force that pushes a rocket up. Payload is the satellite or instrument carried. Staging means dropping used stages to reduce weight. Escape velocity is the speed needed to leave the earth's gravity, about 11.2 km per second. Geostationary means the satellite appears fixed over one spot because its orbital period equals the earth's rotation period of about 24 hours. Polar orbit passes over the poles and scans the whole earth over time. Sun-synchronous means the satellite passes over a place at the same local solar time each day, so pictures have similar light.

Exam traps

  • Aryabhata was launched with foreign help; Rohini was launched by India's own SLV-3.
  • PSLV serves polar orbits; GSLV serves geostationary transfer orbits.
  • LVM3 is the new name for GSLV Mk III.
  • Geostationary satellites are far higher than sun-synchronous satellites.
  • Mangalyaan is Mars; Chandrayaan is Moon; Aditya-L1 is Sun.
  • Chandrayaan-3 landed near the south pole region, and India is the fourth country with a soft landing.
  • NavIC is regional, not global.
  • BrahMos is supersonic cruise; Agni is ballistic.
  • Nag is anti-tank; Akash is surface-to-air.

One-liners

  • 1. ISRO was formed in 1969.
  • 2. Aryabhata was India's first satellite.
  • 3. Sriharikota is ISRO's main launch base.
  • 4. PSLV has four stages.
  • 5. A cryogenic stage uses liquid hydrogen and liquid oxygen.
  • 6. LVM3 launched Chandrayaan-3.
  • 7. NavIC is India's regional navigation system.
  • 8. AstroSat is India's first dedicated astronomy satellite.
  • 9. Mangalyaan reached Mars orbit on the first attempt.
  • 10. Kalam led the IGMDP.
  • 11. BrahMos is made by an India-Russia partnership.
  • 12. The nuclear triad covers land, air and sea.

Practice questions

  1. Which was India's first satellite?

    1. Rohini
    2. INSAT-1A
    3. Bhaskara
    4. Aryabhata
    Answer

    D. Aryabhata

    Aryabhata was India's first satellite and was launched with foreign help.

  2. Which vehicle launched the Rohini satellite, the first satellite put in orbit by an Indian rocket?

    1. LVM3
    2. PSLV
    3. GSLV
    4. SLV-3
    Answer

    D. SLV-3

    SLV-3 was India's first satellite launch vehicle.

  3. How many stages does the PSLV have?

    1. Three
    2. Four
    3. Five
    4. Two
    Answer

    B. Four

    PSLV has four stages with solid, liquid, solid and liquid fuels.

  4. The cryogenic stage of the GSLV uses which propellants?

    1. Solid fuel only
    2. Liquid hydrogen and liquid oxygen
    3. Kerosene and air
    4. Petrol and oil
    Answer

    B. Liquid hydrogen and liquid oxygen

    Cryogenic engines burn liquid hydrogen with liquid oxygen.

  5. LVM3 was earlier known by which name?

    1. ASLV
    2. PSLV-XL
    3. SSLV
    4. GSLV Mk III
    Answer

    D. GSLV Mk III

    LVM3 is the renamed GSLV Mk III.

  6. Where is India's main spaceport located?

    1. Ahmedabad
    2. Thumba
    3. Sriharikota
    4. Bengaluru
    Answer

    C. Sriharikota

    The Satish Dhawan Space Centre is at Sriharikota in Andhra Pradesh.

  7. NavIC is what?

    1. A Mars mission
    2. A military tank
    3. A weather satellite
    4. India's regional navigation satellite system
    Answer

    D. India's regional navigation satellite system

    NavIC gives navigation over India and nearby areas.

  8. Which mission made India the first to reach Mars orbit in its first attempt?

    1. Aditya-L1
    2. AstroSat
    3. Mangalyaan
    4. Chandrayaan-1
    Answer

    C. Mangalyaan

    The Mars Orbiter Mission succeeded in its first attempt.

  9. Aditya-L1 is a mission to study which body?

    1. Venus
    2. The Sun
    3. Mars
    4. The Moon
    Answer

    B. The Sun

    Aditya-L1 is India's solar observatory.

  10. Which mission carried the lander Vikram and rover Pragyan?

    1. Chandrayaan-1
    2. Mangalyaan
    3. Gaganyaan
    4. Chandrayaan-3
    Answer

    D. Chandrayaan-3

    Chandrayaan-3 made a soft landing near the lunar south pole region.

  11. AstroSat is best described as what?

    1. A navigation satellite
    2. A military satellite
    3. A multi-wavelength space observatory
    4. A weather satellite
    Answer

    C. A multi-wavelength space observatory

    AstroSat is India's first dedicated astronomy observatory in space.

  12. At about what height above the equator is a geostationary satellite placed?

    1. About 500 km
    2. About 36,000 km
    3. About 2,000 km
    4. About 100 km
    Answer

    B. About 36,000 km

    Geostationary orbit is at about 36,000 km above the equator.

  13. Which orbit is commonly used for remote sensing satellites?

    1. Escape orbit
    2. Transfer orbit
    3. Sun-synchronous polar orbit
    4. Geostationary orbit
    Answer

    C. Sun-synchronous polar orbit

    They pass over a place at the same local time each day, giving even light.

  14. Which satellite series is mainly used for communication in India?

    1. Cartosat
    2. RISAT
    3. IRS
    4. INSAT and GSAT
    Answer

    D. INSAT and GSAT

    INSAT and GSAT carry communication and broadcast payloads.

  15. Which satellite can image the earth through clouds and at night?

    1. Oceansat
    2. RISAT
    3. AstroSat
    4. Cartosat
    Answer

    B. RISAT

    RISAT uses radar for all-weather imaging.

  16. Which programme is India's human spaceflight mission?

    1. Mangalyaan
    2. Shakti
    3. Gaganyaan
    4. Aditya
    Answer

    C. Gaganyaan

    Gaganyaan plans to send astronauts to low earth orbit.

  17. Which body authorises and promotes private space activities in India?

    1. HAL
    2. DRDO
    3. BEL
    4. IN-SPACe
    Answer

    D. IN-SPACe

    IN-SPACe is the promotion and authorisation centre for the private sector.

  18. Which was the first Indian lunar mission?

    1. Chandrayaan-3
    2. Chandrayaan-1
    3. Chandrayaan-2
    4. Mangalyaan
    Answer

    B. Chandrayaan-1

    Chandrayaan-1 was an orbiter with a Moon Impact Probe.

  19. Which programme led by A. P. J. Abdul Kalam produced Prithvi, Agni, Akash, Trishul and Nag?

    1. Gaganyaan
    2. Mission Shakti
    3. Integrated Guided Missile Development Programme
    4. Operation Flood
    Answer

    C. Integrated Guided Missile Development Programme

    IGMDP developed these five missile systems.

  20. Which missile is an anti-tank guided missile?

    1. Agni
    2. Nag
    3. BrahMos
    4. Prithvi
    Answer

    B. Nag

    Nag is designed to destroy armoured vehicles.

  21. Which missile is a supersonic cruise missile developed with Russia?

    1. BrahMos
    2. Agni
    3. Prithvi
    4. Akash
    Answer

    A. BrahMos

    BrahMos is a joint India-Russia supersonic cruise missile.

  22. Which missile is a surface-to-air missile of medium range?

    1. Nag
    2. Prithvi
    3. Agni
    4. Akash
    Answer

    D. Akash

    Akash is designed to hit aircraft and missiles in the air.

  23. INS Arihant is what type of vessel?

    1. Destroyer
    2. Aircraft carrier
    3. Nuclear-powered ballistic missile submarine
    4. Survey ship
    Answer

    C. Nuclear-powered ballistic missile submarine

    INS Arihant is India's nuclear-powered ballistic missile submarine.

  24. Which policy is part of India's nuclear doctrine?

    1. No First Use
    2. First strike always
    3. Total disarmament
    4. Unlimited stockpiling
    Answer

    A. No First Use

    India follows no first use and credible minimum deterrence.

  25. The nuclear triad refers to delivery from which three platforms?

    1. Army, police and navy
    2. Land, air and sea
    3. Rail, road and air
    4. Sun, moon and earth
    Answer

    B. Land, air and sea

    The triad is land-based missiles, aircraft and submarines.

  26. Where are most missile tests held on the Indian coast?

    1. Goa coast
    2. Gujarat coast
    3. Kerala coast
    4. Odisha coast
    Answer

    D. Odisha coast

    Many missile test ranges lie on the Odisha coast.

  27. Which centre of ISRO mainly develops launch vehicles?

    1. Space Applications Centre
    2. Vikram Sarabhai Space Centre
    3. National Remote Sensing Centre
    4. U. R. Rao Satellite Centre
    Answer

    B. Vikram Sarabhai Space Centre

    VSSC at Thiruvananthapuram designs launch vehicles.

  28. Why is Sriharikota a good launch site?

    1. Near the equator and next to the sea
    2. Located in a desert
    3. Located in a large city
    4. Close to the poles
    Answer

    A. Near the equator and next to the sea

    The equator-near location helps use the earth's rotation, and the sea keeps people safe.

  29. Where was India's first rocket launched from, starting the sounding rocket programme?

    1. Sriharikota
    2. Pokhran
    3. Ahmedabad
    4. Thumba
    Answer

    D. Thumba

    Thumba in Kerala was the first launching station for sounding rockets.

  30. Which launch vehicle is made for small satellites on demand?

    1. LVM3
    2. GSLV Mk II
    3. SSLV
    4. PSLV
    Answer

    C. SSLV

    The Small Satellite Launch Vehicle suits small payloads.

  31. A satellite appears fixed over one place on the earth. Which orbit is it in?

    1. Sun-synchronous orbit
    2. Geostationary orbit
    3. Polar orbit
    4. Low earth orbit
    Answer

    B. Geostationary orbit

    A geostationary satellite orbits once in about 24 hours above the equator.

  32. A cruise missile differs from a ballistic missile because it does what?

    1. Follows a high arc and falls freely
    2. Never uses an engine
    3. Is launched only from a ship
    4. Flies at low level with continuous engine power
    Answer

    D. Flies at low level with continuous engine power

    Cruise missiles fly with powered flight within the atmosphere.

  33. Which Andhra Pradesh city has the Eastern Naval Command?

    1. Visakhapatnam
    2. Tirupati
    3. Guntur
    4. Kurnool
    Answer

    A. Visakhapatnam

    The Eastern Naval Command is based at Visakhapatnam.

  34. Consider these statements on launch vehicles. 1. PSLV is used mainly for polar sun-synchronous orbits. 2. GSLV is built with a cryogenic upper stage.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both statements are correct.

  35. Consider these statements on Chandrayaan-3. 1. It was launched by LVM3. 2. It landed near the lunar south pole region.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both statements are correct.

  36. Consider these statements on NavIC. 1. It is a regional navigation system. 2. It is a global system covering the whole world.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    NavIC covers India and nearby areas, not the whole world.

  37. Consider these statements on Aryabhata and Rohini. 1. Aryabhata was India's first satellite. 2. Rohini was launched by an Indian-made rocket.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both statements are correct.

  38. Consider these statements on orbits. 1. Geostationary satellites are higher than sun-synchronous satellites. 2. Remote sensing satellites are usually in geostationary orbit.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Remote sensing satellites are usually in low polar sun-synchronous orbit.

  39. Consider these statements on missiles. 1. Nag is an anti-tank missile. 2. BrahMos is a ballistic missile.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    BrahMos is a supersonic cruise missile.

  40. Consider these statements on the nuclear triad. 1. It includes submarine-based delivery. 2. It makes a second-strike capability possible.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both statements are correct.

  41. Consider these statements on Mangalyaan. 1. It was launched by PSLV. 2. It is a mission to study the Sun.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Mangalyaan went to Mars; Aditya-L1 studies the Sun.

  42. Consider these statements on Sriharikota. 1. It lies on an island off the Andhra Pradesh coast. 2. It has launch pads for PSLV and LVM3.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both statements are correct.

  43. Consider these statements on IGMDP. 1. It was led by A. P. J. Abdul Kalam. 2. It developed the Agni missile.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both statements are correct.

  44. Consider these statements on cryogenic engines. 1. They use liquid hydrogen and liquid oxygen. 2. They use solid fuel only.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Cryogenic engines use liquid propellants at very low temperatures.

  45. Consider these statements on IN-SPACe. 1. It promotes private participation in space. 2. It is a missile test range.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    IN-SPACe authorises private space activity; it is not a missile range.

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