BE/B Eng Bachelor of Engineering Bachelor of Aerospace Engineering 5 โ Questions and Answers
Question 1: What is the significance of the Prandtl-Glauert singularity in transonic aerodynamics?
- It predicts wing flutter at subsonic speeds
- It is a mathematical divergence in the linearized compressibility correction near Mach 1 (Correct answer)
- It marks the onset of boundary layer transition
- It defines the maximum lift coefficient achievable
Correct answer: It is a mathematical divergence in the linearized compressibility correction near Mach 1
The Prandtl-Glauert correction factor (1/โ(1-Mยฒ)) diverges as Mโ1, indicating that linear theory breaks down in the transonic regime where nonlinear effects dominate.
Question 2: Which type of satellite orbit provides continuous coverage of the polar regions and is ideal for Earth observation?
- Geostationary orbit (GEO)
- Molniya orbit
- Sun-synchronous orbit (SSO) (Correct answer)
- Geosynchronous inclined orbit
Correct answer: Sun-synchronous orbit (SSO)
Sun-synchronous orbits have near-polar inclinations (~98ยฐ) that precess to maintain a constant angle with the Sun, providing consistent lighting conditions for repeat imaging of all latitudes.
Question 3: In structural analysis, what does the term 'margin of safety' (MS) represent?
- The factor by which the applied load exceeds the allowable load
- The fractional reserve strength beyond the design limit condition (Correct answer)
- The ratio of ultimate to yield strength of the material
- The percentage reduction in weight from the original design
Correct answer: The fractional reserve strength beyond the design limit condition
MS = (Allowable Load / Applied Load) - 1, so MS = 0 means the structure is exactly at its limit and any positive value indicates reserve strength.
Question 4: What is the primary function of a thermal protection system (TPS) on a re-entry vehicle?
- To maintain structural integrity under launch vibration loads
- To protect the vehicle from aerodynamic heating during atmospheric entry (Correct answer)
- To insulate cryogenic propellant tanks from solar radiation
- To reduce radar cross-section for stealth applications
Correct answer: To protect the vehicle from aerodynamic heating during atmospheric entry
During re-entry, aerodynamic deceleration converts enormous kinetic energy into heat; the TPS (tiles, ablators, or TUFI coatings) absorbs or reradiates this heat to keep the structure intact.
Question 5: In propulsion, what does the term 'specific impulse' (Isp) fundamentally measure?
- The thrust produced per unit engine mass
- The thrust produced per unit weight flow rate of propellant (Correct answer)
- The total impulse delivered over the burn duration
- The combustion efficiency relative to theoretical maximum
Correct answer: The thrust produced per unit weight flow rate of propellant
Isp = Thrust / (แน ร gโ) in seconds, representing how efficiently a propellant produces thrust โ higher Isp means more thrust per pound of propellant consumed per second.
Question 6: Which aerodynamic phenomenon is responsible for the induced drag on a finite wing?
- Skin friction along the wing surface
- Pressure differential between upper and lower surfaces causing spanwise flow and trailing vortices (Correct answer)
- Shock waves forming at the wing tips at high speed
- Boundary layer separation near the trailing edge
Correct answer: Pressure differential between upper and lower surfaces causing spanwise flow and trailing vortices
Spanwise pressure gradients cause air to flow around the wingtips, creating trailing vortices that tilt the lift vector rearward, producing drag โ this is induced (vortex) drag.
Question 7: What does the term 'specific excess power' (Ps) indicate in aircraft performance?
- The thrust available beyond what is needed to maintain level flight at a given airspeed
- The rate at which an aircraft can simultaneously increase both speed and altitude (Correct answer)
- The excess lift over weight during a pull-up maneuver
- The difference between installed and uninstalled engine thrust
Correct answer: The rate at which an aircraft can simultaneously increase both speed and altitude
Ps = (T-D)V/W in ft/s, representing the energy rate available to increase kinetic or potential energy, enabling simultaneous acceleration and climb.
BE/B Eng Bachelor of Engineering Bachelor of Aerospace Engineering 5
What is the significance of the Prandtl-Glauert singularity in transonic aerodynamics?