Tubular Piston Projectile Peripheral Thrust Design
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Solution Overview
Problem
Conventional captive piston projectiles are inefficient in generating thrust due to susceptibility to rupture and restricted high-pressure gas flow, which limits their ability to reduce noise and visibility during launch, posing safety concerns for the user.
Innovation Solution
A captive piston projectile design featuring a tubular piston member attached around the periphery of the payload housing, allowing a larger surface area for pressurized gases to act upon, with collapsible bellows or telescoping sections for increased stroke length and compact storage, and stabilization fins for enhanced stability and aerodynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a thin piston is used inside the payload housing, then the projectile can be compact, but the surface area for gas action is limited reducing thrust efficiency
Solution Approach 1:
The piston is reconfigured from a linear inside-the-housing arrangement to a tubular peripheral arrangement around the payload housing. This dimensional repositioning allows the piston surface area to expand significantly while maintaining a compact overall projectile volume, as the piston now utilizes the circumferential space around the payload rather than competing for internal housing volume.
Solution Approach 2:
The tubular piston is designed to collapse around the payload housing in the stowed configuration, nesting the piston structure within the available peripheral space. During launch, the piston expands outward from this nested state, increasing its effective surface area for gas action while maintaining a compact pre-launch profile.
2Productivity
If the piston is housed within the centre of the projectile, then payload volume is maximized, but gas flow is restricted making thrust generation inefficient
Solution Approach 1:
The piston transitions from a central internal position to a peripheral tubular position around the payload housing. This spatial reconfiguration opens up the central area for unrestricted gas flow while positioning the piston surface optimally for gas action, allowing both efficient thrust generation and maximum payload volume.
Solution Approach 2:
The projectile is segmented into distinct functional zones: the central payload housing area for maximum payload volume, and the peripheral tubular piston area for thrust generation. This segmentation allows gas to flow freely through the central region while acting efficiently on the peripheral piston surface, resolving the conflict between gas flow efficiency and payload volume.
3Force
If a long piston stroke is required, then thrust is increased, but the projectile becomes less compact
Solution Approach 1:
The tubular piston is designed to collapse around the payload housing during stowage, with the piston walls folded or compressed radially inward. This nested configuration minimizes the projectile's overall length and diameter before launch. During operation, the piston expands radially outward from this compact nested state, achieving a long effective stroke length for high thrust while maintaining a compact pre-launch profile.
Solution Approach 2:
The piston structure transitions dynamically between two states: a compact collapsed state for storage and transport, and an extended state during launch. The bellows-like or collapsible tube structure allows this dynamic transformation, enabling long stroke length when needed while minimizing dimensions when not in use.
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 design enhances thrust generation, reduces noise and visibility, and improves user safety by containing pressurized gases within the projectile, while maintaining a compact and aerodynamic profile, and stabilizing the projectile during flight.
Implementation Method 1
The bellows portion is inflated by pressurised gases within the piston assembly to cause the piston member to move towards the extended position
Data Source
AI summary
A captive piston projectile (40) comprising a payload housing (43), a piston assembly attached to the payload housing (43), and actuation means (46) for urging the piston assembly from a stowed configuration to an extended configuration. The piston assembly comprises a tubular piston member (41) attached around the periphery of the payload housing (43), the attachment optionally being in the form of a circumferential groove (42) within which the piston member (41) can slide. This provides increased thrust whilst maintaining payload volume. Particularly suited to use with barrelled weapons, and also relates to a method of manufacture.