Spherical Blast Impulse Recorder Using 3-Axis Acceleration
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Solution Overview
Problem
Existing acceleration measurement devices, such as unconfined momentum traps (UMTs), are less than accurate and unreliable in measuring blast impulse due to limitations in survivable magnitude, orientation sensitivity, and interference from secondary effects like shrapnel and projectile impacts, leading to measurement uncertainty and difficulty in extracting test results.
Innovation Solution
The Solid Instrumented Spherical Blast Impulse Recording Device (SISBIRD) features a machined reusable metallic spherical shape with a high-resolution 3-axis accelerometer, temperature, pressure, and GPS sensors, providing a consistent surface area to the blast wave regardless of orientation, and is designed to withstand higher blast forces and projectiles, enabling more accurate and reliable impulse measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If unconfined momentum traps (UMTs) are used to measure blast impulse, then blast impulse measurement is achieved, but measurement accuracy and reliability deteriorate due to limitations in survivable magnitude, orientation sensitivity, and interference from secondary effects
Solution Approach 1:
The patent employs a spherical housing design for the blast impulse recording device. The spherical shape provides consistent surface area presentation to the blast wave regardless of device orientation, eliminating orientation sensitivity issues. The curved spherical form also better withstands blast forces compared to flat or block-shaped UMTs, improving both measurement accuracy and reliability in high-magnitude blast environments.
Solution Approach 2:
The patent replaces traditional mechanical measurement systems (such as inverted ballistic pendulums and cantilever plates) with modern electronic sensors including 3-axis accelerometers, pressure sensors, and temperature sensors. This substitution eliminates mechanical connection losses, material deformation uncertainties, and friction effects, thereby significantly improving measurement accuracy and reliability.
2Measurement precision
If traditional UMT shapes (disk, cone, hemisphere) are used, then blast impulse measurement is possible, but measurement uncertainty increases due to changing projected area and drag effects
Solution Approach 1:
The spherical housing maintains a constant projected area and consistent aerodynamic characteristics throughout the blast event, regardless of device rotation or orientation. This eliminates the drag coefficient variations and projected area changes that plague traditional UMT shapes, thereby reducing measurement uncertainty and improving impulse measurement accuracy.
Solution Approach 2:
The spherical design provides uniform surface properties and consistent interaction with the blast wave across all orientations. This homogeneity in geometric presentation to the blast ensures that measurement characteristics remain constant throughout the impulse event, eliminating the variability introduced by changing projected areas in traditional UMT designs.
3Measurement precision
If block-shaped UMTs are used with reinforced sides, then blast impulse measurement is achieved, but device complexity increases due to orientation requirements and placement constraints
Solution Approach 1:
The spherical housing eliminates orientation sensitivity entirely, as the sphere presents identical surface area and geometric properties to the blast wave from any direction. This allows the device to be placed in any orientation without affecting measurement accuracy, significantly reducing placement constraints and operational complexity compared to block-shaped UMTs with reinforced sides.
Solution Approach 2:
The patent inverts the traditional approach by using perfect symmetry (sphere) rather than asymmetric block shapes with reinforced sides. This symmetric design eliminates the need for careful orientation and placement, as no particular side or direction is privileged, thereby reducing device complexity and easing deployment requirements.
4Measurement precision
If older impulse measurement methods (inverted ballistic pendulum, cantilever plate) are used, then total impulse calculation is achieved, but measurement uncertainty increases due to material restitution coefficients and energy losses
Solution Approach 1:
The patent replaces mechanical impulse measurement systems (inverted ballistic pendulums and cantilever plates) with direct electronic sensing using 3-axis accelerometers and pressure sensors. This substitution eliminates the need to account for material restitution coefficients, friction losses, and energy dissipation in mechanical connections, thereby significantly reducing measurement uncertainty and improving total impulse calculation accuracy.
Solution Approach 2:
The patent uses modern electronic sensor technology to directly capture blast impulse data without relying on intermediate mechanical transformations. The accelerometers and pressure sensors directly measure the physical quantities of interest (acceleration, pressure) and convert them to electrical signals for digital recording, eliminating the chain of mechanical energy transformations that introduce uncertainty in traditional methods.
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
SISBIRD achieves higher accuracy and repeatability in blast impulse measurement, supporting the validation and optimization of explosive device designs and extending its application to commercial industries like fluid flow measurement, with improved durability and faster data analysis capabilities.
Implementation Method 1
The spherical shape provides for a predictable aerodynamic response to explosive impulse that is not sensitive relative rotation with respect to explosive impulse. The spherical shape also mitigates impact by shrapnel or projectiles
Implementation Method 2
measuring the acceleration of a known shape when accelerated by a blast wave generated by a high explosive detonation
Implementation Method 3
blast wave generated by a high explosive detonation
Implementation Method 4
explosive impulse that is not sensitive relative rotation with respect to explosive impulse
Data Source
AI summary
A Solid Instrumented Spherical Blast Impulse Recording Device (SISBIRD) includes a spherical housing formed of material that is resistant to an explosive blast wave from a test weapon. A test payload bore shaft is accessible through an opening in the spherical housing. A door is fastened over the opening in the spherical housing. A test data module is received in the test payload bore shaft. The test data module includes: (i) a three-axis acceleration sensor; (ii) a memory; and (iii) a controller. The controller is communicatively coupled to the three-axis acceleration sensor and the memory. The controller executes a data acquisition utility to record, in the memory, acceleration data in three-dimensions from the three-axis acceleration sensor during exposure of the spherical housing to the explosive blast wave.