Ejectable Aft Fin Housing for Projectile Stabilization
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Solution Overview
Problem
Small form factor aero-bodies face challenges in passive stabilization due to size and cost constraints, which are exacerbated by their high angle of attack and different stabilization forces compared to traditional missiles, resulting in longer stabilization times.
Innovation Solution
A projectile design featuring an ejectable aft fin housing assembly that alters the center of pressure to improve passive stabilization, combined with a control action system using maneuvering fins and motors for active stabilization, allowing for faster and more effective pitch rate reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If traditional passive stabilization methods are used for SFFA, then the structure remains simple and low cost, but the stabilization time is excessively long (approximately 5 seconds)
Solution Approach 1:
The stabilization system is divided into two distinct phases: passive stabilization using fixed fins for initial stabilization, and active stabilization using maneuvering fins with control motors for refined control. This segmentation allows each subsystem to be optimized for its specific function, reducing overall stabilization time while maintaining cost-effectiveness
Solution Approach 2:
The passive stabilization system with fixed fins is deployed first to rapidly reduce pitch rate during the critical initial phase. This preliminary action prepares the projectile for subsequent active stabilization by the control system, effectively breaking down the stabilization process into manageable stages
2Reliability
If active stabilization systems are used in SFFA, then pitch rate control is improved, but cost and weight increase significantly
Solution Approach 1:
The system transitions from static fixed fins to dynamic maneuvering fins with control motors only when needed. This dynamic approach allows the projectile to use passive stabilization for most of its flight, activating active stabilization only when pitch rate control is required, thereby minimizing weight and cost while maintaining reliability
Solution Approach 2:
The control system monitors pitch rate and dynamically adjusts the deployment and actuation of maneuvering fins based on real-time conditions. By changing operational parameters rather than maintaining constant active stabilization, the system achieves reliable pitch control with minimal weight penalty
3Ease of operation
If SFFA are launched at high angle of attack, then deployment capability is improved, but passive stabilization becomes more difficult with longer stabilization times
Solution Approach 1:
The fixed passive stabilization fins serve as an intermediary system that bridges the gap between high-angle-of-attack deployment and stable flight. These fins provide the initial stabilization needed to transition the projectile from its high-angle deployment state into a regime where active control can effectively take over
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables rapid passive stabilization of small form factor aero-bodies within four seconds of launch at high angles of attack, transitioning to active stabilization for sustained control, thus overcoming the limitations of traditional stabilization methods.
Implementation Method 1
Center of pressure is a point where resultant aerodynamic force act on the projectile
Implementation Method 2
passive stabilization in SFFAs is driven by lateral inertia (Iyy)
Implementation Method 3
altering the orientation of the maneuvering fins when the projectile is in flight in an atmosphere
Data Source
AI summary
A projectile including an ejectable aft fin housing assembly. The aft fin housing assembly includes aft fins that increase a distance between a center of gravity and a center of pressure of the projectile, improving passive stabilization of the projectile. Once the projectile has been passively stabilized, the aft fin housing assembly is ejected, decreasing a distance between the center of gravity and the center of pressure, improving active stabilization of the projectile.