The NASA Standard Initiator (NSI) is a

pyrotechnic Pyrotechnics is the science and craft of creating fireworks, but also includes safety matches, oxygen candles, explosive bolts (and other fasteners), parts of automotive airbags, as well as gas-pressure blasting in mining, quarrying, and demol ...

device used to set off other pyrotechnic devices. It is the central multi-purpose component of a modular system of

detonating cord Detonating cord (also called detonation cord, detcord, detacord, blasting rope, or primer cord) is a thin, flexible plastic tube usually filled with pentaerythritol tetranitrate (PETN, pentrite). With the PETN exploding at a rate of approximat ...

pyrotechnics Pyrotechnics is the science and craft of creating fireworks, but also includes safety matches, oxygen candles, Pyrotechnic fastener, explosive bolts (and other fasteners), parts of automotive airbags, as well as gas-pressure blasting in mining, q ...

and various other

explosive charge An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An exp ...

s with many different uses. The ignition charge of the device is a blend of

zirconium Zirconium is a chemical element; it has Symbol (chemistry), symbol Zr and atomic number 40. First identified in 1789, isolated in impure form in 1824, and manufactured at scale by 1925, pure zirconium is a lustrous transition metal with a greyis ...

potassium perchlorate Potassium perchlorate is the inorganic salt with the chemical formula K Cl O4. Like other perchlorates, this salt is a strong oxidizer when the solid is heated at high temperature, although it usually reacts very slowly in solution with reducin ...

, Viton B and

graphite Graphite () is a Crystallinity, crystalline allotrope (form) of the element carbon. It consists of many stacked Layered materials, layers of graphene, typically in excess of hundreds of layers. Graphite occurs naturally and is the most stable ...

, often abbreviated as ZPP. Uses of the device include: * Setting off pressure cartridges, pocket sized

gas generator A gas generator is a device for generating gas. A gas generator may create gas by a chemical reaction or from a solid or liquid source, when storing a pressurized gas is undesirable or impractical. The term often refers to a device that uses a ...

s which in turn

pneumatic Pneumatics (from Greek 'wind, breath') is the use of gas or pressurized air in mechanical systems. Pneumatic systems used in Industrial sector, industry are commonly powered by compressed air or compressed inert gases. A centrally located a ...

ally activate other systems. * Setting off the NASA standard detonator, which itself activates other systems

explosive An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An ex ...

ly. * Triggering Pyrotechnic Circuit Interrupters, severing bundles of

electrical cable Electricity is the set of physical phenomena associated with the presence and motion of matter possessing an electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by Maxwel ...

s. * Triggering explosive valves to open/close pressurization lines or fuel lines. * Triggering a pyrotechnic pin puller which opens a

Marman clamp A Marman clamp is a type of heavy-duty band clamp; it allows two cylindrical objects to be clamped together end-to-end with a ring clamp. It is sometimes also known as a "Marman ring". It consists of a circular strap with an interior V-shaped gr ...

, separating two spacecraft. * Acting as an igniter.

Development

The NASA Standard Initiator (NSI) was developed from the Single-Bridgewire Apollo Standard Initiator (SBASI) which was itself based on the Apollo Standard Initiator (ASI). To provide additional redundancy and thus make the spacecraft more reliable, a double- bridgewire design was utilized, but during development of the Apollo Standard Initiator it was found that the original design responded unfavorably to RF frequencies. This resulted in a redesign with a single bridgewire which was approved in 1966. This new design introduced several other changes to improve resistance and give the device a longer shelf life, such as switching the material of the body from 17-4 PH steel to Inconel 718.
After the

Apollo program The Apollo program, also known as Project Apollo, was the United States human spaceflight program led by NASA, which Moon landing, landed the first humans on the Moon in 1969. Apollo followed Project Mercury that put the first Americans in sp ...

ended, the Initiator was renamed and re-used on other

spacecraft A spacecraft is a vehicle that is designed spaceflight, to fly and operate in outer space. Spacecraft are used for a variety of purposes, including Telecommunications, communications, Earth observation satellite, Earth observation, Weather s ...

, such as the

Space Shuttle The Space Shuttle is a retired, partially reusable launch system, reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. ...

Development

References

See also