Torque and Forces: Exploring the World of Aerospace Engineering

What Can We Learn from SV Magnetorquers, Viscous Flow, Aerodynamics, and SV Manufacture and Test?

Let's dive into the world of aerospace engineering with some intriguing questions:

1. What are the false statements about SV magnetorquers, and which one is not true?

A. Magnetorquers operate on the principle of Lorentz forces and are controlled by the amount of current passing through a coil.

B. Magnetorquers create a magnetic moment to apply a torque to the 5 V.

C. In the CubeSat lab, both "Educational" Satellite (ESAT) magnetorquers intentionally produced torques around all 3 ESAT's axes.

D. Magnetorquers can be used to desaturate reaction wheels.

E. All the above statements are true.

2. What is the truth about the SV Lab using the Educational Sat (ESAT)?

A. ESAT uses sun sensors and a magnetometer as actuators to control its attitude.

B. ESAT uses magnetorquers to measure the magnetic field.

C. Net momentum is only conserved between the SV and reaction wheel (RW) when the SV is spinning at a constant rate.

D. Accelerating a RW one direction causes ESAT to accelerate in the same direction.

E. All the above statements are false.

3. Which statement is false concerning viscous flow?

A. Magnus effect is an observable phenomenon commonly associated with a rotating object moving through a fluid.

B. Vortex shedding is a fluid dynamics phenomenon in which low-pressure vortices shed from either side of the body creating a wake behind the body.

C. Boundary layer thickness is defined as the "y" or vertical distance from the surface at which the local velocity is the same as the freestream velocity.

D. Unequal shear forces within the boundary layer cause turbulent flow to begin to transition to laminar flow.

4. In terms of aerodynamics, which statement holds true?

A. Subsonic, transonic, supersonic refer to speed of sound (a) at different altitudes.

B. Speed of sound in air does not vary with air temperature.

C. Speed of sound in air does not vary with air density.

D. Mach Number M = v / c is the ratio of flow velocity v in the boundary layer relative to the local speed of sound.

5. What is true regarding SV Manufacture and Test?

A. Qualification Tests ("Qual Testing") provides formal proof that the design meets specification requirements + margin and all parameters in the interface Control Documents (icDS).

B. "Proto-flight" Tests are the same as Qual, except you will fly the proto-fight unit.

C. Acceptance Tests (aka "Workmanship" Tests) proves unit, subsystem, or 5 V are free of manufacturing defects and meets requirements.

D. Acceptance Tests (aka "Workmanship" Tests) are less severe than proto-qual tests.

E. All the above statements are true.

Answers:

Let's uncover the truths and falsehoods behind these aerospace engineering concepts:

11. The statement that is false about SV magnetorquers is option B: Magnetorquers create a magnetic moment to apply a torque to the 5 V. Magnetorquers operate on the principle of Lorentz forces and are controlled by the amount of current passing through a coil. They create a magnetic moment to apply a torque to the satellite, not to the 5 V power source. In the CubeSat lab, the "Educational" Satellite (ESAT) magnetorquers intentionally produce torques around all three ESAT's axes. Magnetorquers can also be used to desaturate reaction wheels. Therefore, the false statement is option B.

12. The statement that is true about the SV (CubeSat) Lab that used the Educational Sat (a.k.a. "ESAT") is option D: Accelerating a reaction wheel in one direction causes ESAT to accelerate in the same direction. ESAT uses sun sensors and a magnetometer as sensors to control its attitude, not actuators. It does not use magnetorquers to measure the magnetic field. Net momentum is conserved between the SV and reaction wheel (RW) when the SV is spinning at a constant rate. Accelerating a reaction wheel in one direction causes ESAT to accelerate in the opposite direction due to conservation of angular momentum. Therefore, the true statement is option D.

13. The statement that is false regarding viscous flow is option C: Boundary layer thickness is defined as the "y" or vertical distance from the surface at which the local velocity is the same as the freestream velocity. The boundary layer thickness is defined as the distance from the surface at which the flow velocity reaches 99% of the freestream velocity, not the same as the freestream velocity. The Magnus effect is an observable phenomenon associated with a rotating object moving through a fluid. Vortex shedding is a fluid dynamics phenomenon where low-pressure vortices shed from either side of the body, creating a wake. Unequal shear forces within the boundary layer cause turbulent flow to transition to laminar flow. Therefore, the false statement is option C.

14. The statement that is true in terms of aerodynamics is option D: Mach Number M = v / c is the ratio of flow velocity v in the boundary layer relative to the local speed of sound. Subsonic, transonic, and supersonic refer to speeds of the flow relative to the speed of sound. The speed of sound in air does vary with air temperature and density. The Mach Number (M) is defined as the ratio of flow velocity (v) to the local speed of sound (c). Therefore, the true statement is option D.

15. The statement that is true in terms of SV Manufacture and Test is option A: Qualification Tests provide formal proof that the design meets the specified requirements with additional margin. "Proto-flight" Tests are similar to Qualification Tests, but they involve flying the proto-flight unit. Acceptance Tests (also known as "Workmanship" Tests) ensure that the unit, subsystem, or 5 V are free of manufacturing defects and meet the specified requirements. Acceptance Tests are typically less severe than proto-qualification tests. Therefore, the true statement is option A.

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