What is the MIL-DTL-901E?
MIL-DTL-901E is a detail specification defining the high-impact shock testing requirements for machinery, equipment, systems, and structures aboard surface ships and submarines. Adopted 20 June 2017, MIL-DTL-910E supersedes MIL-S-910D as the standard for verifying the ability of shipboard installations to withstand the shock of nuclear and conventional weapons, as well as environmental mechanical shock during operation.
What is the difference between MIL-DTL-901E and MIL-S-901D?
MIL-DTL-901E, like its MIL-S-901D predecessor, is designed to help ensure the survivability and availability of critical shipboard systems under normal operating conditions, as well as when in combat or while under attack.
MIL-S-901D had been the de facto standard for shock testing and qualification of maritime systems, including mission- and safety-critical computer systems and electronic equipment, for nearly 30 years. The 82-page MIL-S-901D document, composed on a typewriter and published on 17 March 1989, described the functional requirements for a system, including its capabilities and the environment in which it must operate, and the criteria for verifying compliance, but it provided flexibility in how required results were achieved.
MIL-DTD-901E goes beyond MIL-S-901D with the addition of detailed production and testing procedures, extensive diagrams and examples, and provisions for testing on land to help field needed equipment faster and more cost-effectively.
What do I need to know about MIL-DTL-901E?
Mission- and safety-critical systems should be built, tested, and proven to work reliably, especially in harsh or combat environments. To help ensure the survivability and reliability of shipboard systems, MIL-S-901D has been updated, expanded, and revised into a detail specification, which are intended to limit ambiguity or uncertainty.
MIL-DTL-901E standard shock test methods include: lightweight and medium weight shock machine tests, the heavyweight shock test performed on a floating shock platform, and medium weight deck simulating shock test on deck-mounted equipment or deck simulating shock machine (DSSM).
The detail specification classifies items under test into one of two shock grade categories. Grade A is applicable to items that are essential to the safety and continued combat capability of the ship. Grade B applies to items that are not essential to the safety and combat capability of the ship, but which could become a hazard to personnel or to the ship as a whole as a result of exposure to shock.
MIL-DTL-910E further categorize items to be tested by type – as a principal unit, subsidiary component, or subassembly – and equipment class. Tests are then classified according to the item type: a Type A test applies to a principal unit, Type B test to a subsidiary component, and Type C test to a subassembly.
How do I ensure equipment is compliant to MIL-S-901D or MIL-DTL-901E?
When evaluating solutions for mission- and safety-critical applications, look for products that are specifically designed to be rugged and reliable. Crystal Group products are meticulously engineered, manufactured, and assembled specifically to withstand challenging applications, harsh elements, and extreme environments. (Take a closer look at how Crystal Group builds rugged products, from material selection through parts stabilization during assembly, thermal management, and more.)
It is always advisable to confirm that a particular solution complies with MIL-S-901D or, preferably, the more detailed MIL-DTL-901E before investing in and fielding it. Verify the test methods and test parameters used, and whether an internal or independent test facility was employed. (Read more about common standards and requirements, which Crystal Group products are designed to meet or exceed.)
By Jim Shaw, Executive Vice President of Engineering, Crystal Group Inc.
Growing global tensions and threats, compounded by deadly collisions, are bringing a renewed focus on sea power. The goal is to increase the readiness, capabilities, and capacity of Sea Services through increased investment in advanced systems and platforms able to address a wide range of operations.
Government and defense leaders are calling for urgent modernization and growth to help maintain an advantage in advanced technologies, including weapons and systems to enhance the reliability and survivability of capabilities, systems, and networks. Military standards are key to meeting these objectives, and ensuring the reliability and survivability of mission- and safety-critical systems.
MIL-S-901D has been the de facto standard for shock testing and qualification of maritime systems, including mission- and safety-critical computer systems and electronic equipment, for nearly 30 years. The 82-page MIL-S-901D document, composed on a typewriter and published on 17 March 1989, described the functional requirements for a system, including its capabilities and the environment in which it must operate, and the criteria for verifying compliance.
MIL-S-901D specified the performance requirements, but intentionally provided some flexibility in how those required results were achieved. That flexibility led to ambiguity over the years and, many argue, resulted in some suppliers taking too much latitude in testing and reporting test results. As a result, defense customers and contractors had to be cautious and confirm suppliers’ claims of compliance with MIL-S-901D, by verifying the test methods, test parameters, and internal or independent test facility employed.
System survivability should not be open to interpretation; rather, mission- and safety-critical systems should be built, tested, and proven to work reliably, especially in harsh or combat environments. To that end, MIL-S-901D has been updated, expanded, and revised into a detail specification, known for leaving little open to interpretation.
MIL-DTL-901E, like its predecessor, details high-impact shock testing requirements for machinery, equipment, systems, and structures aboard surface ships, including carriers and submarines, to “verify the ability of shipboard installations to withstand shock loadings due to the effects of nuclear or conventional weapons or environmental mechanical shock during operation.”
MIL-DTL-901E outlines the test procedures for high-impact shock testing, specifying lightweight, medium weight, and heavyweight standard shock test methods. Lightweight and medium weight tests are performed on shock machines on land. The lightweight and medium weight “hammer test” involves a moving weight that is dropped from various heights, imparting transient shock to the test article that is affixed to an anvil plate.
In contrast, the heavyweight shock test is performed on a floating shock platform in a body of water. Also known as the barge test, the heavyweight shock test is easily one of the most visually impressive qualification procedures. It involves explosives, after all.
For the barge or heavyweight test, a large floating platform is positioned in a body of water, oftentimes the ocean, with the test article fastened to a test fixture. Explosives are positioned at various underwater depths and distances from the barge, and you can guess what happens next: BOOM. The explosives are detonated, delivering a shock to the barge, after which systems under test are studied to determine deficiencies and given a pass/fail grade.
MIL-DTL-901E, like its MIL-S-901D predecessor, is invaluable to ensuring system survivability and availability under normal operating conditions, as well as when in combat or while under attack – the worst possible time for mission- and safety-critical systems to fail. MIL-DTD-901E goes beyond MIL-S-901D with the addition of detailed production and testing procedures, extensive diagrams and examples, a table of contents with links, and provisions for testing on land. In the interest of fielding equipment faster, while saving time and money, MIL-901E adds the ability to test certain systems’ susceptibility to shock and compliance with the specification on an approved Deck Simulating Shock Machine (DSSM) on land.
Little has been written about MIL-DTL-901E to date, but much is being done to implement the detail specification. My colleagues and I were privileged to attend a barge test in Rustburg, Virginia, last November that put Crystal Group’s all-new RS1.533S18G Rugged 1.5U Server through its paces. It was an impressive sight to see the Crystal Group RS1.533S18G successfully operate through four shots under barge shock testing and pass.
Engineered to provide high-performance, highly reliable computing in even the most extreme operating environments, the Crystal Group RS1.533S18G Rugged 1.5U Server features an all-aluminum chassis with internal cross-braces and stabilized components to withstand high shock and vibration. It is MIL-S-901 certified to Grade B and Class III, and can be upgraded to Grade A and Class III with an optional shock kit and solid-state drives.
About the author:
Jim Shaw is the Executive Vice President of Engineering at Crystal Group. Since 2006, Jim has led the engineering department and the new product development team.
Jim’s revolutionary design prowess led to the birth of the rugged series (RS) chassis for the military and industrial computing markets. During Jim’s tenure at Crystal Group the company has expanded its rugged product lines with embedded, storage, displays, switches, carbon fiber options, and custom power supply designs.
Jim holds a Bachelor of Science degree in Mechanical Engineering from Iowa State University and a Master of Business Administration from the University of Iowa. Prior to joining Crystal Group, Jim held a management position in engineering at Rockwell Collins in Cedar Rapids, Iowa. While at Rockwell Collins, he was honored three times as an Engineer of the Year nominee for his work in high performance electronics packaging. He has authored or co-authored eight international patents.
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