Removable Optical Sensor Cap Ejection for Rain-Eroded Missiles

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Solution Overview

Problem

The front lens of optronic assemblies in missiles is susceptible to rain erosion, degrading optical performance and potentially impairing aerodynamic performance during flight.

Innovation Solution

A removable sensor protection cap is mounted on the fuselage, held by retaining members and ejected using a pyrotechnic device controlled by the electronic guidance circuit during the terminal phase of flight, ensuring the sensor's performance and maintaining aerodynamic integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If the front lens is exposed during flight, then aerodynamic performance is improved, but the sensor is subjected to rain erosion degrading optical performance

Engineering Contradiction:
Improverain erosion on sensorVSAvoidaerodynamic drag
Core Design Contradiction:
Object-affected harmful factorsVSObject-generated harmful factors

Solution Approach 1:

The protection system is segmented into a removable cap that can be separated from the fuselage. The cap is retained during most of flight to protect the sensor, then ejected during the terminal phase to expose the sensor for optimal aerodynamic performance and detection capability.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The protection cap transitions from a static attached state to a dynamic ejected state. The retaining members hold the cap against aerodynamic forces during flight, then the inactivation member releases the retaining members allowing the cap to eject under aerodynamic pressure during the terminal phase.

Inventive Principle:
Principle #15Dynamics

2Reliability

If a protection cap is attached during terminal phase, then sensor protection is maintained, but aerodynamic drag increases and detection performance is impaired

Engineering Contradiction:
Improvesensor detection performanceVSAvoidaerodynamic drag
Core Design Contradiction:
ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The sensor calibration is performed preliminarily with the cap in place using the uniform internal surface, ensuring detection performance is established before the cap is ejected during the terminal phase.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The protection cap is discarded (ejected) when no longer needed for protection, allowing the sensor to operate without aerodynamic interference during the terminal phase while maintaining detection performance.

Inventive Principle:
Principle #34Discarding and recovering

3Strength

If the retaining member is made stronger to hold the cap, then cap retention against aerodynamic forces is improved, but the ejection mechanism becomes more complex

Engineering Contradiction:
Improveretaining member strengthVSAvoidejection mechanism complexity
Core Design Contradiction:
StrengthVSDevice complexity

Solution Approach 1:

The mechanical retention system is supplemented with a pyrotechnic inactivation member that chemically initiates release. The retaining members are designed to be breakable or releasable through the pyrotechnic action, simplifying the ejection mechanism while maintaining strong retention during flight.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The retaining members transition from a high-strength state during flight to a low-strength state during ejection. The inactivation member changes the physical or chemical parameters of the retaining members, allowing them to fail or release under controlled conditions.

Inventive Principle:
Principle #35Parameter changes

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 protects the sensor from rain erosion while ensuring optimal detection performance and minimal aerodynamic disruption, with the cap being ejected at the right moment to avoid drag and maintain missile control.

Implementation Method 1

an inactivation member for the retaining member and an electronic control circuit arranged to control the inactivation member in flight so as to allow ejection of the cap

Methodology Applied
Scientific EffectExplosion: Explosion

Data Source

PatentEP4558780B1Air vehicle having a protected front optical element
Publication Date: 2026.04.22 SAFRAN ELECTRONICS & DEFENSE (FR)
  • EP4558780B1 patent drawingFigure 1~2
  • EP4558780B1 patent drawingFigure 3~4

AI summary

The invention relates to an aerial vehicle comprising a fuselage (1) having a front portion (2) provided with an optronic sensor (10) and a cover (11) for protecting the sensor, the cover being removably mounted and held on the fuselage by at least one retaining member (14) arranged to protect the cover against aerodynamic forces exerted on the cover during flight, the air vehicle comprising a member (16) for deactivating the retaining member and an electronic control circuit (7) arranged to control the deactivation member in flight so as to allow the cover to be ejected.