Reliable & Flexible Electronic Safe and Arm Device

Electronic Safe and Arm Device

An Electronic Safe and Arm Device (ESAD) is designed for mission critical applications where a reliable arming and firing sequence with precise timing events is vital. Used for flight termination systems and rocket motor ignition, our ESADs meet the stringent requirements of RCC-319 and MIL-STD-1901A. Utilized with our bulk Destruct Charge or Linear Shaped Charge, our fully electronic device interfaces with a flight termination receiver, or mission controller, through a customizable input connector. This device outputs a high voltage firing current to initiate single or dual Low Energy Exploding Foil Initiators (LEEFIs). Our ESADs can be integral with the LEEFI energetic output or can initiate the LEEFIs through a high voltage flex tip. Also referred to as a high-energy electronic initiator firing unit, this device meets safety board requirements by incorporating two unique inhibits that must be satisfied prior to firing. Both “armed on the ground” and “armed after safe separation” approved variants are available.

Electronic High Voltage Safe and ArmsThe most recent pyro-technology type is the High Voltage Safe and Arm Device (HV SAD). Unlike all other safe and arm devices, it is an inline safe and arm, meaning, there is no physical block between the firing energy and the output pyrotechnic device. The output pyrotechnics for a HV SAD is an exploding foil initiator. For a high voltage safe and arm system to be considered a safety system, there are few requirements it must meet. It can only utilize insensitive secondary explosives. These are listed in MIL-STD-1316. And its initiator must require greater than 500 volts DC for initiation of the output. The two requirements are achieved by using what we call an exploding foil initiator (EFI). And the EFI is the fundamental enabling technology for the high voltage, safe and arm.

Sandia developed this enabling technology in the 90s, which does not depend on heat to ignite the pyrotechnic. Instead it uses an insensitive secondary explosive which is directly initiated with a high velocity detonation impact. The high velocity flyer is generated by discharging very high current (>1000A) through a small reactive semiconductor which then explodes and propels a tiny flyer at velocities greater the 3000m/s into the explosive pellet. Due to the insensitivity of this technology and the very specific electrical impulse required to fire it, the U.S. Safety Board community allowed for the use of an all-electronic firing system without the need for mechanical/physical barriers. Arming requires 3 MOSFETs to close in order to charge the
high voltage capacitor:
► Two Static
► One Dynamic

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How A High Voltage In-Line Electronic Safe & Arm Device Works

This is the only Safe and Arm Device (SAD) considered to be an “In-Line” SAD. Sandia developed an enabling technology in the 90s called an “Exploding Foil Initiator” which does not depend on heat to ignite the pyrotechnic.  Instead it uses an insensitive secondary explosive which is directly initiated with a high velocity detonation impact. The high velocity flyer is generated by discharging very high current (>1000A) through a small reactive semiconductor which then explodes and propels a tiny flyer at velocities greater the 3000m/s into the explosive pellet. Due to the insensitivity of this technology and the very specific electrical impulse required to fire it the US safety board community allowed for the use of an all electronic firing system without the need for mechanical/physical barriers.

Arming requires 3 MOSFETs to close to charge the high voltage capacitor.

Benefits

There are several design benefits to using a HV In-line Safe and Arm Device including:

  • 2-3x reduction in size and weight compared to Electromechanical Safe and Arms
  • Cheaper than Laser Safe and Arms
  • Flexible
  • Modular features and inhibits
  • HV Safe and Arms do not include verification of the EFI bridge
  • Smaller and lighter than Electromechanical SADs (2-3x)
  • HV SADs are more customizable
  • Internal FPGA allows for more system logic states, unique behavior and control and has modular features than can be added or removed
    • Accelerometers
    • G switches for launch or impact detection
    • Temperature/pressure sensors
    • Keep alive capacitors to weight by eliminating FTS batteries
    • Single or multi output
    • Built in digital timing
    • Power on self test (POST)

Features

  • 2 static and 1 dynamic switch
  • Internal redundant bleed resistors
  • RCC319 Qualified
  • Laser welded hermetic 304L stainless package
  • Power on self test and arm status outputs
  • Actel Antifuze Mil Spec FPGA
  • Reverse bias protected input and output pins
  • Proper sequence and signal filtering
  • Built in hardware timers for safe separation
  • (Range of Timing)
  • Several available external inhibit inputs

All the device nomenclatures listed below are “In-Line” electronic safe and arms which utilize high voltage EFI technology. On the left is a list of acronyms to help clarify some of the confusion around the naming of these devices. All HV safe and arms use very similar internal circuitry and logic but tend to have different acronyms assigned based on what function they are preforming. There are three common ways the safe and arm can be configured.

#1. Close coupled EFI system. This should be a single package that has the safe and arm circuitry and logic, the high voltage generation circuitry and the firing switch all co-located in a single package. The EFI is either directly mated with are welded into that package.

#2. Remote EFI and high voltage flex configuration. This has a single unit which contains the safe in our logic, the safe and arm circuitry, the high voltage generation, and the firing switch. But the EFI is now connectorized and in place on the end of a strip line. These are a special configuration because the fire pulse passes through the strip line and the inductance and losses in that strip line must be considered, thus the distance must be kept as short as possible. These types of devices are common in a flight termination system where the exporting furniture can be detached up to 12 inches from the safe and arm.

#3 Remote EFI and firing circuitry. More common for the distributed fusing systems, where the inductance and the short distance is not a concern. In this case, the Safe and Arm contains the safe and arm logic, the safe and arm circuitry, and the high voltage generation. We move the firing switch and the high voltage capacitor to a remote location with the EFI. We can connect those with a simple high voltage twisted pair. In this configuration, the EFI is moved much further away from the safe and arm logic.

All the device nomenclatures listed below are “In-Line” electronic safe and arms which utilize high voltage EFI technology. This list of acronyms can be confusing due to their similarity. To better understand each one, please see below. The high voltage portions use very similar internal circuitry and logic, but the devices tend to have a different acronym used to define them based on the function they perform. Even though all the systems are very similar, if it’s being used for rocket motor ignition, its often called an EISD. If its used for fuzing, it’s often called an Electronic Safe and Arm Fuze (ESAF). If its a Flight termination system, or a hand-emplaced ordnance system, it is sometimes called an Electronic Safe and Arm Device (ESAD) or Electronic Arm Fire Device (EAFD). Essentially, they’re all variations of the same thing, simply different acronyms based on the system in which they are being used.

Acronyms

  • eISD/EISD – Electronic Ignition Safety Device
  • eSAD/ESAD – Electronic Safe and Arm Device
  • eSAF/ESAF – Electronic Safe and Arm Fuze
  • eAFD/EAFD – Electronic Arm Fire Device

Three Common Implementations

There are also serval ways to implement a HV SAD in a system and each is convenient for different reasons

High Voltage In-Line Electronic Safe and Arm Device Configurations

Electrical Characteristics

Logic power
Wide voltage input range options 5v – 36v

Arming power
Internal regulation of power inputs for logic andarming circuits

Power requirements
Pre-Armed quiescent current <70mA
Arming peak current variable from (100mA @ 100ms arming time) to (1.2A @ 10ms arming time)
Post-Armed quiescent current <100mA

Inhibit Options

Two static switches & one dynamic switch:
• Factory selectable separation timers
• Accelerometers
• Breakwire (umbilical disconnect)
• Event sequence and timeout
• Flight battery switch detection
• Additional custom configurations available

Envelope/Interface Design

Electronic Safe & Arm Device Single and Dual Outputs

Quite often we are asked “Which of these ESADs do you have off the shelf and are already qualified to MIL-STDs?” Although we’ve sent many devices through those mil specs and qualified them to those mil specs. It’s a difficult question to answer due to the fact the high level military specifications don’t get into the details of what signals you have available on your vehicle, what interfaces are available or the environments of your particular vehicle. And that’s not to mention the different opinions of the various safety boards will have on one of these devices depending on it’s use.

Questions to Consider

►What is your application, to help us understand what the device is meant to accomplish?
► Which one of our devices is closest to your application?
► Do you already know which specification applies, and what’s the platform of the vehicle?
► Do you know whether pyrotechnic output is deflagrating or detonating?
► Is it a bulk destruct charge?
► Do you require transfer lines?
► What are your envelope and power restrictions do you need to keep live batteries in this design doesn’t need to be extremely low power?
► Do you need the ability to co-locate the entire device in one area?
► Does it need to be separated in one of those other configurations?
► When is the arming occurring? Before launch or arm after launch? On a rocket motor ignition it’s always before or prior to launch. On things like fuses and FTS it is usually arm after launch and changes the types of inhibits we use.
► Do you have redundancy requirements?
► Does this need to be a dual output, or will it be multiple SADs?
► Do you know the environmental requirements?
► Do we know the max predicted environments to temp, shock, vibe, or any EMI, EMP, radiation?
► Are there any special qualification time requirements or time frame?

With this information when discussing options, we can help to chose a device that would have the largest “Qualification by Analysis” or “Qualification by Similarity” as possible to minimize the scope of the qualification effort.

Flight Termination Electronic Safe & Arm Device (FTS ESAD)

As a leader in the design, test and manufacturing of Safe and Arm devices, our Electronic Safe and Arm Devices (ESAD) and detonators for safe compliant requirements of both legacy and next-generation IM-compliant munitions. Our talented team of scientists and engineers use the latest advances in technology to design meet harsh launched weapon systems requirements. Count on our shock-hardened designs, proven to survive and function post launch. We include options for multipoint initiation configurations while also designing for proximity, impact, and timed self-destruct detonation. All of our ESADs are manufactured in a state-of-the art ISO 9001 facility.

Description
The FTS ESAD is a single or dual output high voltage flight termination safe and arm which initiates exploding foil initiators (EFI) after the receipt of all valid arming and firing conditions.
Input Connector
The input connector is a MIL-DTL-83513 female Micro-D with either a 51 pin or 21 pin configuration depending on the required number of inputs and telemetry outputs. The pin out configurations are shown below with an example of the 21 pin signal assignments.
Out Connector
The output connector is a glass to metal hermetic high voltage 2 pin bulk head design which mates with a low inductance HV flex circuit in order to interface with a detonating EFI.

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