Pyrotechnic Shock Testing, Measurement

This is a three- day introduction course to the theoretical and practical aspects of high frequency shock testing, commonly called “pyroshock” or “pyrotechnic shock” testing.

The basic physics involved in pyroshock, including meaningful measurement and analysis of the environment, will be presented and discussed. The presentation encourages attendees (having varied structural dynamic backgrounds and experience) to contribute their personal experiences and observations, and thus to collaborate with the teaching staff and their fellow attendees. Their experience, if any, might range from the quantification of the flight environment to test simulation and/or qualification and flight acceptance of flight articles.

Test simulation and methodologies will be presented and demonstrated in the laboratory. Relevant sections from Wayne Tustin’s text will be reviewed and will be extended into applicable current technical papers and guidelines. This material will be supplemented by the instructor’s pyro-shock measurement, SRS analysis, calibration and pyro-shock testing techniques handouts.

This short course is intended for a wide range of technical people, ranging from test technicians to test engineers to design engineers to senior scientists, who need to understand and conduct tests utilizing (or at least simulating) explosions. They also need to measure, record and analyze what happens to test hardware during and immediately after those brief events. Real world pyro shocks occur during explosions and explosive discharges, such as rocket engine ignition, stage separation, etc.

The objective of this course is to introduce the designer, technician and/or engineer to the phenomena of high intensity, short duration field and test laboratory transients and the possible deleterious effects on equipment.

Overview

Definition of pyro shock

Sources

• High order explosives (PETN, RDX, detonation, etc.)
• Low order explosives (gas generators, pressure generators, deflagration etc.)

Physics

• Stress wave propagation
• Structural response

Data acquisition system

• Source
• Instrumentation
• Accelerometer – various types
• Signal conditioning
• Filtering, high pass and low pass
• Data storage
• Analog (recall Honeywell RTR recorders – long extinct)
• Digital
• Analog to digital conversion
• Sigma delta converters
• Low pass filtering requirements
• Calibration of data acquisition system
• Data integrity – verification and analysis
• Time history examination
• Frequency domain
• FFT
• Shock Response Spectrum

Ordnance Testing Methodologies

• Gathering and storing flight data
• Full scale structure simulation
• Sub scale structure simulation
• Surrogate structure simulation
• Testing real hardware that is later to fly

Simulation testing methodologies

• Electrodynamic Shaker
• Enhanced electrodynamic shaker
• Resonant Fixturing
• Mechanical Impact
• Gravity Driven Impact
• Testing hardware that is later to fly

Testing Examples

• Ordnance pyroshock test demonstration by NTS
• Electrodynamic shaker pyroshock simulation test demonstration by NTS
• Mechanical impact pyroshock simulation test demonstration by NTS

Vladimir Valentekovich teaches about pyrotechnic and other forms of shock testing, measurement, analysis and calibration and consults in these fields. He is a graduate of UCLA with his Bachelor and Masters of Science in Mechanical Engineering. He worked as a Senior Test Engineer in Structural Dynamics, specializing in pyrotechnic shock, at Wyle Laboratories, El Segundo.

Vladimir was responsible for quantifying and publishing the high velocity, short duration stress wave resultant in near-field pyroshock, as referenced in the IES Recommended Practice 012.1 Handbook for Dynamic Data Acquisition and Analysis, Appendix A, Pyroshock and the 5th ed. Harris and Piersol Shock and Vibration Handbook, Chapter 26 Part II. Vladimir received the SAVIAC 64th Symposium Henry Pusey Award for this work in 1994.

Wyle Laboratories then was the first independent contractor to do pyroshock qualification testing using the Tomahawk Cruise Missile U/RGM-109D flight structure: from instrumentation, specifying the data acquisition system, placing the charge, to acquiring and analyzing the resultant data.

Valentekovich developed many pyrotechnic shock test methods still used at Wyle. He continues to develop alternate pyro shock methods and test equipment including mechanical impact and ballistic shock simulations.

Vladimir currently consults for aerospace and defense firms who seek to design, perform and complete meaningful dynamics test programs.

Field Testing Can Be a Blast

Posted on November 12, 2021 by Bob McLeod

As discussed in last week’s ATI Blog, Model Based Systems Engineering is a great way to accomplish goals cheaper, faster, and better.  MBSE alleviates the need to verify your design and construction with frequent and expensive field testing.  Unfortunately, however, there is still a need to occasionally conduct field testing.  Field testing may be required to verify the validity of models which feed your MBSE. Additionally, it is sometimes critically important to conduct field tests, even though Models suggest that the system will work as designed.  One example of this would be when human lives are at stake, and the designer is unwilling to put full trust in the MBSE.

The design of the US’s newest Aircraft Carrier, The Gerald Ford Class Carrier, is an excellent example of how Field Testing may be used in conjunction with MBSE.

The US Navy explains that “The Navy designed the Ford-class carrier using advanced computer modeling methods, testing, and analysis to ensure the ships are hardened to withstand harsh battle conditions.” Although MBSE assured engineers that the ship would be safe in battle conditions, field testing was ordered in order to verify the MBSE.  Such verification is not performed for every design.  In fact, the last time field testing was used by the Navy to verify MBSE was in 2016 for Littoral Combat Ships.

Pyrotechnic Shock Testing on August 8, 2021 in water off the coast of Florida.  This testing  validated the ship’s ability to sustain operations in a simulated combat environment.  40,000 pound underwater explosions were released at distances progressively closer to the Carrier, which was heavily instrumented to record the amount of shock that was experienced onboard.

The Navy explains that “These shock trials have tested the resiliency of Ford and her crew and provided extensive data used in the process of validating the shock hardness of the ship.”

Engineers should always use MBSE, but must also be familiar with Pyrotechnic Shock Testing which is sometimes required in addition to MBSE.

To read the US Navy’s reporting of this Pyrotechnic Shock Testing, and to see pictures and videos of the testing, you can go here.

To read about and register for ATI’s upcoming Pyrotechnic Shock Testing course, you can go here.

And, as always, to see a full listing of all ATI courses, you can go here.