Safe and Arm Devices

Product Description

50 Years of Experience

A Safe and Arm Device (SAD) prevents any main charge explosive (military, oil and gas, or space vehicles) from accidental initiation prior to arming, while at the same time allowing the intended explosive train to detonate once it has been armed. Basically a safe arm device controls the initiation of a pyrotechnic train such that the energetic output is fired only when commanded and is safe at all other times. It’s a device that prevents inadvertent arming or firing of a pyrotechnic event and makes the system is insensitive to environmental stimulus, such as fires, electro-magnetic fields, stray voltages and  electro-static discharge

Pacific Scientific Energetic Materials Company (PacSci EMC) has over fifty years of experience providing highly reliable ordnance components and systems for space launch vehicles, missiles, tactical weapons, and aircraft, and is well known in the aerospace and defense industry as the leading supplier of Safe and Arm (S&sA) along with Arm-Fire Devices (AFD). S&A/AFDs are safety devices that provide electrical and mechanical interruption to prevent unintended functioning of an ignition train, predominantly in either a Flight Termination System (FTS) or Rocket Motor Ignition (RMI) System.

The terms S&A and AFD have been used interchangeably throughout history, but most commonly refer to the product’s end use. S&A devices are typically used by the Space Launch industry in Flight Termination Systems and in Solid Rocket Booster Ignition Systems. AFDs are typically used in Missile Systems for Rocket Motor Ignition. Both products act to protect the system and associated personnel from accidental Rocket Motor Ignition or Flight Termination System activation. There are some exceptions to this “rule”, primarily for missiles that require flight termination systems, e.g. during the missile’s development testing phase. Accordingly, there are several S&A configurations that appear more like traditional AFDs in design. PacSci EMC has been producing S&As and AFDs for over fifty years. The list of programs is extensive, with table below providing a sample of programs having extensive technical requirements and long term production. Many programs use multiple PacSci EMC S&A/AFD devices on the same platform.

A variety of PacSci EMC programs using Safe and Arm along with Arm Fire Devices

Our Safe and Arm Devices

• Arm Fire Device
• Electronic Safe & Arm Device
• Electronic Ignition Safety Device
• Electro-mechanical Safe & Arm Device
• Ordnance Safe & Arm Device

In the beginning…
In 1992, the Eastern Test Range advised the space launch community that imposition of EWR-127 would be mandatory for future spacecraft launch vehicles. Prior to that directive, each launch vehicle and contractor utilized a broad variety of different Safe and Arm Devices for Flight Termination and Ignition. These devices were from a variety of sources, varied widely in their designs, and did not comply with EWR-127.

The Atlas program made a decision to solicit a new S&A that would not only be EWR-127 compliant, but would also withstand increasingly severe environments of higher performance launch vehicles and provide a substantial cost reduction over existing S&A devices.

We presented a design and was selected after a competitive selection process. This design was based on a balanced single rotor design that met all of the Atlas criteria. Our design, aka, “The Red S&A Family”, was subsequently issued U.S. Patent 5,279,226 in 1994.

A generic design of the original Atlas S&A, shown in Figures 1 and 2, easily accommodated minor electrical circuit variations, mounting, safing key orientation, and other features. The Atlas unit was fully qualified for a Flight Termination System and Solid Rocket Motor Ignition to the requirements of MIL-STD-1576 and EWR 127.

Once the initial qualification program was approved, several other programs and customers adopted the PacSci EMC S&A design. Since its inception, this original qualified design, has been re-qualified and flown on almost all U.S. space launch vehicles. The list of customers and programs includes, Boeing’s Delta launch vehicles, Orbital Sciences Corporation’s Pegasus and Taurus launch vehicles, Lockheed’s Titan and Atlas launch vehicles, and Northrop’s SLS program in the near future.

To date, the Red S&A family is qualified to RCC 319-07T, adding to its extensive pedigree in both margin testing and qualification. We are extremely familiar with RCC 319 and the Range
Safety process through our delivery of over 1,500 S&As to meet the RCC 319-92, 99, and 07 requirements over the past 15 plus years on the following programs: SSST Coyote, Stormbraker,
JASSM, JASSM-ER and Targets and Countermeasures Program. Both Eastern and Western test ranges and the Aerospace Corporation have been involved in the evolution and details of the design. To date, we deliver approximately 200 S&As annually.

In 2002, Lockheed Martin approached us to provide a lighter weight and smaller size S&A. We originally qualified P/N 108800 S&A to support a Lockheed program in 2005 that met RCC 319-99 requirements with a subsequent delta-qualification series to RCC 319-07 in 2009. That design incorporated the pedigree of the Red S&A family in a smaller package.

Its all about decisions
Are the mission requirements clearly defined? Is redundancy a must? Visual or electrical monitoring? Permanent assembly or need to disassemble? Minimum Performance vs Operational vs Margin inputs? What about minimum Reliability? Since the initial days of S&A/AFD qualification, the complexity of mission needs and test requirements have grown significantly. As such, the initial assessment and selection can be overwhelming. Although most of the criteria will be mission dependent, the simplest method is to narrow the search by defining
the application industry, as shown in Table 2. Once the typical industry qualification requirements The right design for your application

Determining the type of S&A/AFD design to choose is directly dependent on intended use. Typical applications include Rocket Motor Ignition or Flight Termination. Occasionally, a variant S&A known as an Interrupter is used for energy transfer inhibit/enable applications. For any Aerospace or Defense application, size and weight matters, which is why we have such an extensive inventory of qualified S&A and AFD designs with dimensional envelope from a typical 1.3” diameter x 2.3” under 2lbs, up to 5” x 4.5” x 3.5” under 5lbs, with either a single or redundant output for higher reliability. Another example of one of our designs used for Rocket Motor Ignition or Flight Termination are shown in Figures 6. These designs and their variants come from our extended heritage in military applications.

If a customized solution is required, our New Product Development team can manage the full development cycle from Concept Design to Qualification, providing a seamless transition to continuous production.