Deployable Fins for Rotational Braking in Spin-Stabilized Projectiles
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Solution Overview
Problem
Current rotational braking systems for payloads ejected from gyrostabilized projectiles are inefficient, leading to prolonged braking times and unsynchronized rotational and translational braking, which can result in premature ignition of pyrotechnic compositions and reduced operational efficiency.
Innovation Solution
A device with deployable fins positioned at a non-zero angle relative to the axis of the cylindrical casing, fixed along helical lines, generates a lift force and torque to slow down the rotation, allowing for controlled and synchronized rotational braking, potentially eliminating the need for additional braking fins on the payload.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If traditional radial fins are used for rotational braking, then the braking mechanism is simple, but the braking time is too long and cannot be controlled
Solution Approach 1:
The invention changes the geometric parameters of the fins by introducing an inclination angle relative to the generator of the casing. This parameter modification transforms the aerodynamic characteristics of the fins, enabling them to generate both drag force (for braking) and lift force (for controlled deceleration), thereby reducing braking time from dozens of seconds to a controllable duration while maintaining structural simplicity
Solution Approach 2:
The fin configuration is designed to dynamically interact with the aerodynamic flow during flight. The inclined fins automatically adjust the braking effectiveness based on the rotation speed and flight conditions, providing controlled rotational deceleration without requiring complex active control mechanisms
2Reliability
If radial fins parallel to the axis are used, then the manufacturing is simple, but the braking effectiveness decreases with rotation speed
Solution Approach 1:
By modifying the angular parameter of the fins (inclining them relative to the generator), the invention maintains manufacturing simplicity while dramatically improving braking effectiveness across the entire rotation speed range. The inclined configuration ensures consistent aerodynamic interaction regardless of rotation speed variations
Solution Approach 2:
The fins are positioned asymmetrically relative to the radial direction, with an inclination angle that creates differential aerodynamic forces. This asymmetric positioning enhances the braking torque generation while remaining compatible with standard manufacturing processes
3Duration of action of moving object
If long braking time is accepted, then the fin surface area can be smaller, but the payload ignition is premature and illumination duration is reduced
Solution Approach 1:
The inclined fin configuration optimizes the aerodynamic efficiency, generating higher braking torque per unit area. This allows for shorter braking times that synchronize with the payload ejection and ignition sequence, maximizing illumination duration without requiring large fin surfaces
Solution Approach 2:
The enhanced braking effectiveness of the inclined fins enables the system to rapidly reduce rotation speed through the critical phase before payload ejection. This 'rushing through' of the high-speed rotation phase allows timely ignition of the payload, extending the useful illumination duration
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
This solution significantly reduces rotational speed within a shorter timeframe, enabling optimal payload deployment conditions and extending the operational range of pyrotechnic illumination by allowing earlier ignition of the illuminating composition.
Implementation Method 1
the aerodynamic flow during the flight of the envelope has the effect of slowing down the rotation of the latter
Implementation Method 2
generates a lift force and torque to slow down the rotation
Implementation Method 3
generates a lift force and torque to slow down the rotation
Data Source
Figure 1
Figure 2~4
Figure 3a~3b
AI summary
The invention relates to a device for braking the rotation of a cylindrical envelope (7) containing a payload ejected from a gyrostabilized projectile. This device comprises at least two deployable fins (8) regularly spaced angularly on an outer wall (11) of the envelope (7). The fins (8) are positioned relative to the envelope (7) such that their plane, in the deployed position, forms a non-zero angle (α) with the axis (10) of the envelope (7), oriented such that the aerodynamic flow (E) during the envelope's flight has the effect of braking its rotation.