BE/B Eng Bachelor of Engineering Bachelor of Aerospace Engineering 2 — Questions and Answers
Question 1: Which boundary layer transition phenomenon is most critical for hypersonic vehicle design?
- Laminar-to-turbulent transition
- Shock-boundary layer interaction (Correct answer)
- Flow separation at leading edge
- Boundary layer reattachment
Correct answer: Shock-boundary layer interaction
Shock-boundary layer interaction at hypersonic speeds causes extreme local heating and pressure fluctuations that dominate vehicle design constraints.
Question 2: In orbit determination, what is the primary purpose of the state transition matrix?
- To convert between coordinate frames
- To propagate the covariance matrix forward in time (Correct answer)
- To compute gravitational perturbations
- To transform velocity to orbital elements
Correct answer: To propagate the covariance matrix forward in time
The state transition matrix maps how uncertainties in the initial state propagate over time, enabling Kalman filter covariance updates.
Question 3: What does the Knudsen number indicate in gas dynamics?
- Ratio of inertial to viscous forces
- Ratio of mean free path to characteristic length (Correct answer)
- Ratio of thermal to kinetic energy
- Ratio of compressibility to viscosity
Correct answer: Ratio of mean free path to characteristic length
The Knudsen number (Kn = λ/L) determines whether continuum fluid mechanics applies or whether rarefied gas dynamics must be used.
Question 4: Which rocket engine cycle achieves the highest theoretical specific impulse among conventional chemical propulsion systems?
- Gas generator cycle
- Staged combustion cycle (Correct answer)
- Expander cycle
- Pressure-fed cycle
Correct answer: Staged combustion cycle
The staged combustion (full-flow) cycle burns all propellant in the main chamber and uses preburner exhaust to drive turbopumps, maximizing efficiency.
Question 5: In composite laminate design, what is the purpose of a quasi-isotropic layup?
- To maximize strength in one direction
- To achieve equal stiffness in all in-plane directions (Correct answer)
- To minimize interlaminar shear stress
- To reduce manufacturing complexity
Correct answer: To achieve equal stiffness in all in-plane directions
A quasi-isotropic layup (e.g., [0/±45/90]s) distributes fiber orientations so the laminate has uniform in-plane stiffness regardless of loading direction.
Question 6: What is the significance of the L/D ratio in gliding flight performance?
- It equals the glide angle in degrees
- It determines the maximum glide range for a given altitude (Correct answer)
- It sets the stall speed of the aircraft
- It controls the rate of turn in banked flight
Correct answer: It determines the maximum glide range for a given altitude
The maximum L/D ratio directly equals the maximum range-to-altitude ratio in a glide, so a higher L/D means the aircraft travels farther per unit altitude lost.
Question 7: Which astrodynamics concept describes the transfer between two circular orbits using the minimum total delta-V?
- Patched conic approximation
- Hohmann transfer (Correct answer)
- Bi-elliptic transfer
- Gravity assist maneuver
Correct answer: Hohmann transfer
The Hohmann transfer uses two engine burns at opposite ends of an elliptical transfer orbit and is delta-V optimal for most orbit-raising scenarios.
BE/B Eng Bachelor of Engineering Bachelor of Aerospace Engineering 2
Which boundary layer transition phenomenon is most critical for hypersonic vehicle design?