A Long-Awaited Update to an Essential Standard for Military Procurement

MIL‑STD‑464D was released on December 24, 2020. This revision is in keeping with the routine five-year revision cycle applicable to many such standards, and MIL‑STD‑464 must keep in sync with MIL‑HDBK‑235, from which the electromagnetic field intensity tables are drawn. In this case, the routine five-year cycle took ten years to complete.

MIL‑STD‑464 is the U.S. Department of Defense (DoD) top-level E3 requirement set for the procurement of complete or modified systems. In this context, systems means an integrated platform of one type or another, such as a ground or air vehicle, a ship or submarine, a spacecraft, or launch vehicle. Note that some systems can be parts of other systems, such as an F-18 fighter aircraft that operates from an aircraft carrier.

The original release of MIL‑STD‑464 was in 1997. MIL‑STD‑464A (2002) and MIL‑STD‑464C (2010) provided minor, evolutionary changes to the original release.¹

Compared to MIL‑STD‑464C, the changes in MIL‑STD‑464D are very minor. This article serves as a laundry list of the substantive changes, including the EME tables, and indications of what values changed in the EME tables, so that the reader may see at a glance where the changes are, rather than checking each table row-by-row and cell-by-cell.

The purpose of this article is to inform and save the reader the time the author spent combing through MIL‑STD‑464D vs. MIL‑STD‑464C (referenced as D and C throughout the rest of this article). Entertaining the reader was not a practical goal.

New Definitions

3.1 All-up-round (AUR)

“The completely assembled munition as intended for delivery to a target or configured to accomplish its intended mission. This term is identical to the term all-up-weapon.” 

3.2 Bare devices

“Bare electrically initiated devices (EIDs) such as electrical initiators, exploding foil initiators, detonators, etc., in an all-up round that have either one or both pins accessible on an external connector.” 

3.3 Below deck 

Extended to include the pressure hull of a submarine.

3.7 Energetics 

“A substance or mixture of substances that, through chemical reaction, is capable of rapidly releasing energy. A few examples of energetics are: liquid and solid propellants such as in rockets and air bags, gun propellants, polymer bonded explosives (PBX) for warheads, pyrotechnics for flares and ignition systems.” 

3.8 Flight deck

“The upper deck of an aircraft carrier that serves as a runway. The deck of an air-capable ship, amphibious aviation assault ship, or aviation ship used to launch and recover aircraft.” 

3.12 Helicopter-borne electrostatic discharge (HESD)

“The sudden flow of electric charge between a helicopter or rotary winged aircraft and an object of different electrical potential. A buildup of static electricity can be caused by triboelectric charging or electrostatic induction generated from operating rotary wings.” 

3.13 High power microwave (HPM)

Deletes the frequency range.

3.18 Maximum no-fire stimulus

3.22 Ordnance (fewer words than C)

“Explosives, chemicals, pyrotechnics, and similar stores (e.g., bombs, guns, and ammunition, flares, smoke,
or napalm).” 

3.23 Personnel-borne electrostatic discharge (PESD)

“The sudden flow of electric charge between personnel and an object of different electrical potential. A buildup of static electricity can be caused by triboelectric charging or electrostatic induction generated by the movement of the person’s body.” 

3.27 Spectrum-dependent systems

Adds this statement at the end: 

“This includes transmitters, transceivers, and receive-only systems.“

3.34 Vertical replenishment (VERTREP)

“The transfer of ordnance and cargo using rotary winged aircraft.” 

3.35 Weather deck

“The topside of the ship that is exposed to the weather. The weather deck does not include the flight deck, hangar, well deck, man-aloft areas, or the ship’s mast.” 

Main Body Requirements

5.1 Margins (MIL‑STD‑464D)²

“Margins shall be established for safety and mission critical subsystems/equipment within the system. Margins shall be no less than 6 dB for safety critical subsystems/equipment, unless otherwise stated in the detailed requirements of this standard. Compliance shall be verified by test, analysis, or a combination thereof.” 

Compare this with the text in C, as follows:

“Margins shall be provided based on system operational performance requirements, tolerances in system hardware, and uncertainties involved in verification of system-level design requirements. Safety critical and mission critical system functions shall have a margin of at least 6 dB. EIDs shall have a margin of at least 16.5 dB of maximum no-fire stimulus (MNFS) for safety assurances and 6 dB of MNFS for other applications. Compliance shall be verified by test, analysis, or a combination thereof. Instrumentation installed in system components during testing for margins shall capture the maximum system response and shall not adversely affect the normal response characteristics of the component. When environment simulations below specified levels are used, instrumentation responses may be extrapolated to the full environment for components with linear responses (such as hot bridgewire EIDs). When the response is below instrumentation sensitivity, the instrumentation sensitivity shall be used as the basis for extrapolation. For components with non-linear responses (such as semiconductor bridge EIDs), no extrapolation is permitted.”

5.2 Intra-system electromagnetic compatibility (EMC)

5.2.2 Shipboard internal electromagnetic environment (EME)

The very last sentence in C section 5.2.2.b after the listing of the individual device and total EIRP is not found in D. This sentence in C that is not in D reads:

“Additionally, no device shall be permanently installed within 1 meter of safety or mission critical electronic equipment.”

Also, whereas verification in C is by test in all cases, in D, for submarines an analysis consisting of a summation of all individual device EIRP into total radiated power (TRP) is allowed.

(See Tables I – VI)

-464D values first, -464C values second, where different. Red fill means level has increased. Yellow fill means change is less than 3 dB, either higher or lower, and blue fill means -464D level is lower than for -464C. * means no emitters in that frequency range.

TABLE I: Maximum external EME for deck operations on Navy ships vs. -464C Table 1. Maximum external EME for deck operations on Navy ships

‡ The EME levels in the table apply to shipboard operations in the main beam of systems in the 2700 to 3600 MHz frequency range on surface combatants.  For all other operations, the unrestricted peak EME level is 12667 V/m and the unrestricted average level is 1533 V/m. 

TABLE II: Maximum external EME for ship operations in the main beam of transmitters vs. -464C TABLE 2. External EME for shipboard operations in the main beam of transmitters

NOTE: *denotes no emitters in that frequency range. 

TABLE III: Maximum external EME for space and launch vehicle systems vs. -464C TABLE 3. External EME for space and launch vehicle systems

TABLE IV  Maximum external EME for ground systems vs. -464c TABLE 4. External EME for ground systems

TABLE V: Maximum external EME for rotary-wing aircraft, excluding shipboard operations vs. -464C Maximum external EME for rotary-wing aircraft, including UAVs, excluding shipboard operations

TABLE VI: Maximum external EME for fixed-wing aircraft, excluding shipboard operations vs. -464C TABLE 6. External EME for fixed wing aircraft, including UAVs, excluding shipboard operations

-464D values first, -464C values second, where different. Red fill means level has increased. Yellow fill means change is less than 3 dB, either higher or lower, and blue fill means -464D level is lower than for -464C. * means no emitters in that frequency range.

5.5 Lightning 
Has some expanded wording about near strikes and slightly different wording describing Figure 2 and Table VII.

5.7 Subsystems and equipment electromagnetic interference (EMI)
Now includes new wording (in non-italicized text in the excerpt that follows):

“Individual subsystems and equipment shall meet interference control requirements (such as the conducted emissions, radiated emissions, conducted susceptibility, and radiated susceptibility requirements of MIL‑STD‑461) so that the overall system complies with all applicable requirements of this standard. This includes permanent, temporary, and portable electronic equipment. Compliance shall be verified by tests that are consistent with the individual requirement (such as testing in accordance with MIL‑STD‑461).” 

5.7.1 Portable electronic devices and carry-on equipment requirements
Newly added in D, as follows:

“Portable electronic devices and carry-on equipment containing electronics which are not permanently installed or integrated into platforms and require airworthiness certification shall meet, as a minimum, the following EMI interface control requirements: 

• • Safety Critical: All platform emissions and susceptibility requirements (such as those defined in MIL‑STD‑461) that are defined for safety critical equipment. 
  • Non-Safety Critical: All platform emissions requirements (such as those defined in MIL‑STD‑461). 

“If any part of the portable electronic device/carry-on equipment contains radio frequency transmission capability, then transmitter emissions characteristics shall be measured (such as in MIL‑STD‑461 Test Method CE106), in addition to the applicable requirements stated above. An aircraft EMC evaluation per 5.2 shall also be required to demonstrate platform compatibility of the portable electronic devices/carry-on equipment which have radio frequency transmitting capability.

“If any part of the portable electronic device/carry-on equipment contains ordnance or is integrated into an ordnance system, then the HERO requirements stated within this standard shall also be met. Compliance shall be verified by test per the applicable requirements.” 

5.7.3 Shipboard DC magnetic field environment. (5.7.2 in C) 
In the C revision, this requirement could only be verified by test. In the D revision, the ubiquitous phrase, “Compliance shall be verified by test, analysis, or a combination thereof,” is used.

5.8.1 Vertical lift and in-flight refueling 
Slightly reworded, but the same overall requirement with one significant deletion. The C applicability to “any man portable items that are carried internal to the aircraft” has been deleted.

5.8.3 Ordnance subsystems
Rewritten with two brand new sub-paragraphs that break out separately the pre-existing C requirement to withstand a 25 kV personnel ESD and adds a separate new requirement to withstand helicopter ESD (300 kV). 

5.8.4 Electrical and electronic subsystems 
Rewritten to refer to MIL‑STD‑461G (CS118) for test, whereas previously they had to point elsewhere.

5.9.3 Hazards of electromagnetic radiation to ordnance (HERO) 
Rewritten to include ordnance safety margins that were struck from general margin paragraph 5.1.

NOTES: 

*It must be noted that on certain naval platforms, there are radar systems (and unique modes of operation) that may produce fields in excess of those in Table IX, and MIL-HDBK-235 must be consulted to identify specific EME test requirements.

** In some of the frequency ranges for the “Restricted Average” column, limiting the exposure of personnel through time averaging will be required to meet the requirements of 5.9.1 for personnel safety.

TABLE IX: Maximum external EME levels for ordnance vs. -464C TABLE 9. Maximum external EME levels for ordnance.

5.14.2 Platform radiated emissions 

Renamed from the same paragraph in C labeled 5.14.2 Inter-system EMC. The requirement has both greater generality and is more specific about what parameters need to be controlled. New sub-paragraph in D.

6.2 Acquisition requirements

Acquisition documents should specify the following: a. Title, number, and date of this standard. 

6.3 DIDs

Not updated.

6.5 Key Words 

Adds two new terms, electrostatic and HESD.

6.6 International standardization agreement implementation.

Rewritten slightly in D from the previous similar section 6.5 in C.

6.7 Acronyms 

Replaces “EMRADHAZ” with “RADHAZ.” Also, PESD and HESD are added.

6.8 Technical points of contact 

Air Force and Army points-of-contact have been updated.

Appendices and Guidances

A.1.1 Scope 

Includes extra language emphasizing that appendix is guidance only, not mandatory.

A.2.1.1 Specifications, standards, and handbooks 

Slightly different wording. Also, the following additions, changes, and deletions:

• MIL‑STD‑1576, Electroexplosive Subsystem Safety Requirements and Test Methods for Space Systems—removed from applicable documents
• MIL‑STD‑3023 HEMP Protection for Military Aircraft—added
• MIL‑STD‑4023 HEMP Protection for Maritime Assets—added
• MIL‑HDBK‑83578 Criteria for Explosive Systems and Devices Used on Space Vehicles—deleted

A.2.1.2 Other Government documents, drawings, and publications

• Army, ATPD-2407 Electromagnetic Environmental Effects (E3) for U.S. Army Tank and Automotive Vehicle Systems Tailored from MIL‑STD‑464C—added
• TOP 01-2-511A US Army Test and Evaluation Command Test Operations Procedure—added

A.2.2 Non-Government Publications

• Institute of Electrical and Electronics (IEEE) Transactions on Electromagnetic Compatibility 
• DOI:10.1109/TEMC.2016.2575842 Effect of Human Activities and Environmental Conditions on Electrostatic Charging—added
• Franklin Applied Physics 
• F-C2560 RF Evaluation of the Single Bridgewire Apollo Standard Initiator—deleted

A.3 Acronyms

• AMITS air management information tracking system—deleted
• EMRADHAZ—deleted
• HESD helicopter-borne electrostatic discharge—added
• PESD personnel-borne electrostatic discharge—added
• RADHAZ Radiation hazards—added

A.4.1 Requirement Guidance

Adds Army ATPD-2407 and TOP 01-2-511A is EMC guidance and test procedures.

A.4.1.e Requirement Guidance 

Includes additional guidance and a slightly different approach than C. Margin Requirement Guidance A.5.1 adds the non-italicized statement in the following excerpt:

“Margins need to be viewed from the proper perspective. The use of margins simply recognizes that there is variability in manufacturing and that requirement verification has uncertainties. The margin ensures that every produced system will meet requirements, not just the particular one undergoing a selected verification technique. Smaller margins are appropriate for situations where production processes are under tighter controls or more accurate and thorough verification techniques are used. Smaller margins are also appropriate if many production systems undergo the same verification process, since the production variability issue is being addressed. Margins are not an increase in the basic defined levels for the various electromagnetic environments. The most common technique is to verify that electromagnetic and electrical stresses induced internal to the system by external environments are below equipment strength by at least the margin. This approach is similar to the test methodology described in A.4.1 (e). While margins can sometimes be demonstrated by performing verification at a level in excess of the defined requirement, the intent of the margin is not to increase the requirement.”

This paragraph is deleted from this section in D (look for it in the EID section):

“MNFS values for EIDs are normally specified by manufacturers in terms such as DC currents or energy. Margins are often demonstrated by observing an effect during the application of an electromagnetic environment that is the same effect observed when applying a stimulus level in the form under which the MNFS is defined. For example, the temperature rise of a bridgewire can be monitored in the presence of an EME relative to the temperature rise produced by a DC current level that is 16.5 dB below MNFS. The space community has elected to use MNFS levels determined using RF rather than DC. This approach is based on Franklin Institute studies, such as report F-C2560. Outside of the space community, the use of DC levels has provided successful results.”

A.5.2 Intra-system EMC

Under Requirements Rationale, the final sentence in C:

“To ensure EMC is achieved in Navy ships, a MIL‑STD‑1605(SH) survey should be performed.”

is replaced by a more descriptive version in D:

“For surface ships, MIL‑STD‑1605(SH) provides test methods used to verify compliance with the requirements of this standard for intra- and inter-system EMC, hull generated intermodulation interference, and electrical bonding.”

A.5.2 Verification Guidance 

The following and final line item is modified in D to read:

“For portable electronic devices and carry-on equipment, EMI requirements are defined in 5.7.1.” 

In C, line item h reads:

“TABLE A- 1 identifies what kind of EMI/EMC testing is required when new, modified, or carry-on equipment will be used on military aircraft.”

Table A-1 Type of EMI/EMC testing doesn’t exist in D.

A.5.3 Requirement Guidance

These words added to the very end of this section:

“A platform design, while descriptively fitting the title of an external EME table (e.g., Fixed Wing or Rotary Wing), may not coincide with the platform’s operational EME definition. Strict attention must be paid to the assumptions used in deriving the tables to ensure appropriate EMC compliance.”

A.5.4 Requirement Guidance (HPM) 

Eliminates Tables A-4 – A-10 from C and also calculation of some example problems using these tables.

A.5.4 Requirement Rationale (HPM) 

Eliminates some wording questioning the effectiveness of HPM.

A.5.4 Verification Guidance (HPM) 

Eliminates reference to these deleted examples in D.

A.5.6 Requirement Guidance (EMP) 

Contains some extra description of HEMP composite environment. It also adds descriptions of EMP-related military standards for dealing with EMP, including effects on spacecraft.

A.5.6 Requirement Lessons Learned 

Has this sentence in common with C:

“Hardening against ground-burst nuclear radiation environments is often not cost effective because a burst near enough to produce a radiation and electromagnetic threat is also close enough for the blast to disable the facility.” 

But D adds this last sentence not in C: 

“Buried facilities such as ICBM launch sites are an exception.”

A.5.6 Verification Rationale (EMP) 

D replaces this C paragraph:

“For many systems, the cost of EMP verification is a major driver. Therefore, the procuring activity should decide what level of verification is consistent with the risk that they are willing to take.”

with this paragraph:

“High-altitude EMP protection standards have been developed for fixed ground-based facilities, transportable ground-based systems, aircraft and ships. Each of these standards contains detailed verification testing protocols and pass/fail criteria. Use of these standards is mandatory for DoD military system procurements that have a HEMP requirement.”

Note the emphasis on the cost of EMP design has been replaced with wording more conducive to getting EMP designs installed.

In the same section, this new D wording:

“MIL‑STD‑3023 and MIL‑STD‑4023 for HEMP protection of military aircraft and ships, respectively provide a similar verification test approach except that these standards require illuminating the aircraft and ships with a simulated plane wave HEMP threat environment and measuring the induced stresses at each MCS equipment interface. Each MCS must be tested to MIL‑STD‑461 CS116 to establish its immunity before being installed into the platform. A user selectable margin is then applied to the measured current stress which is then pulse current injected (PCI) at the same interface used in the MIL‑STD‑461 CS116 testing. This enables direct stress to immunity comparisons at common interfaces for each mission critical equipment throughout the system. Monitoring for upset and damage is also performed at this time.”

has been appended to this existing C wording:

“MIL‑STD‑188-125-1 and MIL‑STD‑188-125-2 contain verification test methods for demonstrating that C⁴I fixed ground-based facilities and transportable ground-based systems meet HEMP requirements. The test methods describe coupling of threat-relatable transients using pulse current injection to penetrating conductors at injection points outside of the facility shield.”

A.5.7 Requirement Guidance (Subsystem & Equipment EMI)

Eliminates wording about DO-160 section 22 now that CS117 is available.

A.5.7.1 Portable Electronic Devices and Carry-On Equipment Requirements

All new appendix material. Basically refers to A.5.2. Intra-system EMC.

A.5.8.1 Vertical lift and in-flight refueling 

Slightly rewritten, no changes.

A.5.8.3 Ordnance Subsystems 

Greatly expanded and also includes the following new sections:

• A.5.8.3.1 Personnel-borne ESD (PESD) for ordnance and ordnance systems
• A.5.8.3.2 Helicopter-borne ESD (HESD) for ordnance and ordnance systems

A.5.9.3 Requirement Rationale (Ordnance RADHAZ (HERO)).

This section is rewritten with substantive changes.

A.5.9.3 Requirement Guidance (Ordnance RADHAZ (HERO))

This section is rewritten with substantive changes. MIL-STD-464C was:

“OD 30393 provides design principles and practices for controlling electromagnetic hazards to ordnance. MIL‑STD‑1576 and MIL‑HDBK‑83578 (USAF) provide guidance on the use of ordnance devices in space and launch vehicles. For space applications using ordnance devices, an analysis of margins based on the RF threshold determination of the MNFS should be performed.”

The last sentence refers to measuring the rf TOS of bridgewires, and that has been completely debunked.  This section now reads:

“NASA document TP2361 provides design guidelines for space and launch vehicle charging issues. Subsystems and equipment installed aboard space systems should be able to meet operational performance requirements during and/or after being subjected to representative discharges simulating those due to spacecraft charging.”

A.5.14.2 Requirement Rationale (Platform Radiated Emission) 

Rewritten with added information.

A.5.15 Requirement Guidance (EM Spectrum Compatibility) 

Completely rewritten.

A.5.15 Verification Rationale (EM Spectrum Compatibility) 

Completely rewritten.

A.5.15 Verification Guidance (EM Spectrum Compatibility) 

Added information. 

Endnotes

1. MIL-STD-464C is really MIL-STD-464B, but there was a release cycle error, and MIL-STD-464B was replaced after just a few months. The content didn’t change.

2. Author’s note: The significant truncation is due to moving ordnance-related margins to their own separate section. The ordnance margins haven’t changed – this just represents a reorganization of the standard.