BE/B Eng Bachelor of Engineering Bachelor of Aerospace Engineering 4 — Questions and Answers
Question 1: In the context of GPS navigation, what is dilution of precision (DOP)?
- The error introduced by ionospheric signal delay
- A geometric factor describing how satellite geometry amplifies ranging errors (Correct answer)
- The difference between GPS and inertial navigation estimates
- Signal attenuation caused by atmospheric scintillation
Correct answer: A geometric factor describing how satellite geometry amplifies ranging errors
DOP quantifies how the spatial arrangement of visible satellites magnifies individual pseudorange errors into position uncertainty; low DOP means well-spread satellites and better accuracy.
Question 2: Which failure mode is most associated with thin-walled cylindrical pressure vessels under compressive loading?
- Yielding at the inner surface
- Buckling instability (Correct answer)
- Fatigue crack initiation at welds
- Creep at elevated temperature
Correct answer: Buckling instability
Thin-walled cylinders under axial compression are susceptible to shell buckling, which can occur well below the material yield stress.
Question 3: What is the purpose of staging in multistage rockets?
- To reduce aerodynamic drag by changing the nose shape during flight
- To jettison empty propellant mass so remaining engines propel a lighter vehicle (Correct answer)
- To allow different propellants to be used at different altitudes
- To enable thrust vector control at each phase of flight
Correct answer: To jettison empty propellant mass so remaining engines propel a lighter vehicle
By discarding empty tankage and engines, staging continuously reduces the mass that must be accelerated, dramatically increasing the achievable delta-V per the Tsiolkovsky rocket equation.
Question 4: In aerodynamics, what distinguishes attached flow from separated flow?
- Attached flow has a higher Reynolds number
- In attached flow, boundary layer fluid has enough momentum to follow the surface contour (Correct answer)
- Separated flow only occurs at supersonic speeds
- Attached flow always produces lower drag than separated flow
Correct answer: In attached flow, boundary layer fluid has enough momentum to follow the surface contour
In attached flow, the adverse pressure gradient has not overcome the boundary layer momentum, keeping the flow hugging the surface; separation occurs when the fluid can no longer maintain contact.
Question 5: Which orbital element defines the tilt of an orbit's plane relative to Earth's equatorial plane?
- Argument of perigee
- Right ascension of the ascending node
- Inclination (Correct answer)
- Eccentricity
Correct answer: Inclination
Inclination (i) is the angle between the orbital plane and the equatorial plane, ranging from 0° (equatorial) to 180° (retrograde).
Question 6: What is the role of flutter analysis in aircraft structural design?
- To compute fatigue life under gust loading
- To identify the critical airspeed at which aeroelastic oscillations become self-sustaining (Correct answer)
- To optimize wing twist for minimum induced drag
- To assess panel buckling under aerodynamic pressure
Correct answer: To identify the critical airspeed at which aeroelastic oscillations become self-sustaining
Flutter is a dynamic aeroelastic instability where structural and aerodynamic forces couple to produce diverging oscillations; the flutter speed must exceed the aircraft's maximum operating speed with margin.
Question 7: In a turbojet engine, what process occurs in the combustion chamber?
- Isentropic compression of air
- Constant-pressure heat addition to the airflow (Correct answer)
- Adiabatic expansion of combustion gases
- Isothermal mixing of fuel and oxidizer
Correct answer: Constant-pressure heat addition to the airflow
The Brayton cycle models the combustor as a constant-pressure heat addition process, raising the total temperature of the airflow before it enters the turbine.
BE/B Eng Bachelor of Engineering Bachelor of Aerospace Engineering 4
In the context of GPS navigation, what is dilution of precision (DOP)?