Reversible Airbrake for Projectile Path Correction

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Solution Overview

Problem

Existing fuses with extendable airbrakes for projectiles face challenges in overcoming centripetal acceleration during flight, requiring powerful drive arrangements and large batteries, and cannot correct flight path errors after extension.

Innovation Solution

A reversible airbrake system with controllable brake surfaces arranged behind protective devices, allowing extension and retraction in a rotational direction via a twist shaft, enabling path corrections by controlling the braking effect.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the airbrake is extended laterally from the fuse to correct flight path, then path correction capability is improved, but the force required to retract the airbrake increases due to centripetal acceleration

Engineering Contradiction:

Improvepath correction capabilityVSAvoidretraction force

Core Design Contradiction:

Adaptability or versatilityVSForce

Solution Approach 1:

Instead of extending the airbrake radially outward from the fuse (conventional approach), the patent extends it axially in the direction of flight. This inversion of the extension direction allows the airbrake to be deployed along the flight path where it can still affect trajectory but reduces the radial component that creates excessive retraction resistance against centripetal acceleration.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The airbrake is designed with dynamic extension and retraction capability along the axial direction, allowing it to be deployed when needed for path correction and retracted when not needed. The twist shaft mechanism provides dynamic control of the airbrake position, enabling adaptation to different flight conditions while managing the force requirements for deployment and retraction.

Inventive Principle:

Principle #15Dynamics

2Reliability

If a powerful drive arrangement is used to overcome centripetal acceleration, then retraction capability is improved, but the weight and storage space requirements increase

Engineering Contradiction:

Improveretraction capabilityVSAvoiddrive arrangement weight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The drive mechanism is inverted from a radial extension system to an axial extension system. This changes the force vector requirements, allowing the drive arrangement to work with rather than against the projectile's rotation and flight dynamics, reducing the power and weight needed for reliable retraction.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent replaces a complex high-power mechanical drive system with a simpler twist shaft mechanism that utilizes the projectile's rotational motion and aerodynamic forces to assist in the retraction process, reducing the need for heavy motors and power systems.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Loss of time

If the airbrake is extended after maximum height is passed, then late path correction is improved, but the ability to correct errors diminishes

Engineering Contradiction:

Improvecorrection timingVSAvoidpath correction accuracy

Core Design Contradiction:

Loss of timeVSManufacturing precision

Solution Approach 1:

The airbrake system provides dynamic control throughout the entire flight path, allowing correction actions to be taken at any point from launch to impact. The ability to extend and retract the airbrake at different phases of flight enables continuous adjustment of the trajectory, maximizing correction effectiveness even when maximum height has been passed.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The airbrake can be deployed and adjusted continuously during flight rather than being limited to a specific time window. This continuous controllability ensures that path correction capability is maintained throughout the entire flight duration, including the critical later phases after apex, thereby preserving correction accuracy despite extended timing.

Inventive Principle:

Principle #20Continuity of useful action

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 reversible airbrake reduces longitudinal spread and allows for real-time path corrections during projectile flight, improving accuracy in artillery firing by reducing the need for powerful drive arrangements and large batteries.

Implementation Method 1

The protective device reduces the air resistance on the brake surfaces behind it

Methodology Applied

Scientific EffectAir resistance (Drag): Drag

Implementation Method 2

the effect of centripetal acceleration caused by the rotation of the projectile during its flight

Methodology Applied

Scientific EffectCentripetal acceleration:

Data Source

PatentUS11378367B2Fuse with reversible airbrake

Publication Date: 2022.07.05 BAE SYSTEM BOFORS AB

AI summary

A fuse is provided with a reversible airbrake intended for a projectile, wherein the airbrake is arranged such that errors which occur in the flight path of the projectile can be corrected by performing one or more extensions and retractions of the airbrake. The airbrake includes at least two braking surfaces symmetrically arranged each behind a respective protective device arranged on the casing surface of the fuse, wherein the brake surfaces can be extended and retracted in a rotational direction behind the at least two protective devices via a twist shaft arranged centrally in the fuse.