Overview of Orion Crew Module and Launch Abort Vehicle Dynamic Stability (Invited)

Survey of Blunt Body Dynamic Stability in Supersonic Flow

“…This technique was matured during the Apollo program and is still in use today. It allows for explicit determination of the reduced frequency inherent to the vehicle (as opposed to sweeping through various possibilities as in forced oscillation technique) [20], is simple in its implementation, and requires only one measurement (oscillation amplitude as a function of time) [13]. Similar to the forced oscillation setup, free oscillation testing yields an average value of the damping over one oscillation cycle and suffers from the effects of having a sting present to modify the wake flow.…”

“…In order to capture the dynamic behavior, a motor attached to the sting imparts a one-degree-offreedom oscillatory motion to the vehicle at a wide range of frequencies and mode shapes. Sinusoidal motion is typically used [20]. The vehicle is inclined at a wide range of angles of attack and at each condition undergoes a series of small amplitude pitch oscillations.…”

“…American Institute of Aeronautics and Astronautics of this technique are its direct measurement of the dynamic aerodynamic coefficients [15], [20], controllability and repeatability [14], and its ability to match a wide range of reduced frequency parameters (also known as Strouhal numbers) [13]. Additionally, mass scaling is not generally required to obtain representative full scale behavior in the sub scale environment [20].…”

“…Drawbacks of forced oscillation tests are the sting effects on the damping and the inability to observe limit cycle behavior [15]. Also, due to the nature of the the test setup itself, only the average damping over a pitch cycle can be obtained [21] and the accuracy to which it can be obtained is reduced as the measurement techniques are reliant on three independent strain gauge force measurements [20].…”

“…Additionally, mass scaling is not generally required to obtain representative full scale behavior in the sub scale environment [20]. Drawbacks of forced oscillation tests are the sting effects on the damping and the inability to observe limit cycle behavior [15].…”