UPSC Prelims Practice Questions — DRDO Conducts Flight Trial of High-Altitude Platform

Q1. With reference to how lighter-than-air platforms such as stratospheric airships stay aloft, consider the following statements: Which of the statements given above is/are correct?

  1. A lighter-than-air platform can stay airborne without moving forward through the air, whereas a fixed-wing aircraft generates no lift unless air flows past its wings.
  2. Because air thins with height, each cubic metre of lifting gas gives less lift higher up, so a stratospheric airship needs a much larger envelope than a low-altitude craft carrying the same payload.
  3. Since buoyancy keeps it up, a lighter-than-air platform needs no control system to hold a chosen altitude once it has been launched.
  • A. 1 and 2 only
  • B. 1, 2 and 3
  • C. 1 only
  • D. 2 and 3 only

Q2. Consider the following statements: Which of the following is correct in respect of the above statements?

  1. A stratospheric airship can remain aloft for long periods without its propulsion system having to generate the lift that keeps it up.
  2. In the stratosphere, air temperature rises with increasing altitude.
  • A. Both Statement-I and Statement-II are correct and Statement-II explains Statement-I
  • B. Both Statement-I and Statement-II are correct, but Statement-II does not explain Statement-I
  • C. Statement-I is correct, but Statement-II is incorrect
  • D. Statement-I is incorrect, but Statement-II is correct

Q3. With reference to the vertical structure of the Earth's atmosphere, consider the following statements: Which of the statements given above is/are NOT correct?

  1. In the stratosphere, warmer air lies above cooler air, which suppresses convection and vertical mixing.
  2. The warming of the stratosphere with height is caused mainly by heat radiated upward from the Earth's surface.
  3. The tropopause lies lower over the equator than over the poles, so a platform at 20 km over the tropics is more likely to be in the troposphere than one over the poles.
  • A. 1, 2 and 3
  • B. 1 only
  • C. 2 and 3 only
  • D. 2 only

Q4. Consider the following statements: Which of the following is correct in respect of the above statements?

  1. The altitude band of about 18–20 km is considered attractive for long-endurance high-altitude platforms partly because it lies above almost all weather.
  2. Air in the lower stratosphere is denser than air in the upper troposphere, so a buoyant platform gains lift on entering the stratosphere.
  • A. Both Statement-I and Statement-II are correct and Statement-II explains Statement-I
  • B. Both Statement-I and Statement-II are correct, but Statement-II does not explain Statement-I
  • C. Statement-I is correct, but Statement-II is incorrect
  • D. Statement-I is incorrect, but Statement-II is correct

Q5. With reference to tethered aerostats and free-flying stratospheric airships, consider the following statements: Which of the statements given above is/are correct?

  1. A tethered aerostat can receive power and send data through its tether, whereas a free-flying airship must carry its own power and navigation systems.
  2. Both are lighter-than-air systems that need some means of managing the pressure of the gas in their envelopes.
  3. Because it is anchored to a ground winch, a tethered aerostat typically operates at a much lower altitude than a free-flying stratospheric airship.
  • A. 1 and 3 only
  • B. 2 and 3 only
  • C. 1 only
  • D. 1, 2 and 3

Q6. With reference to the navigation systems carried on aerospace platforms such as DRDO's High-Altitude Platform, consider the following statements: Which of the statements given above is/are correct?

  1. An inertial measurement unit fixes the platform's position by receiving signals from ground-based radio beacons.
  2. Since an inertial measurement unit builds its estimate by integrating measurements over time, small sensor errors accumulate and the estimate drifts unless corrected.
  3. A satellite-navigation receiver makes an inertial unit unnecessary, because satellite signals cannot be lost or degraded in flight.
  • A. 1 only
  • B. 2 only
  • C. 2 and 3 only
  • D. 1 and 2 only