NASA Standard Initiator
The NASA Standard Initiator (NSI) is a pyrotechnic device used to set off other pyrotechnic devices.
It is the central multi-purpose component of a modular system of detonating cords, pyrotechnics and various other explosive charges with many different uses.{{cite book
|date=1 October 1963
|title= Proceedings of Electric Initiator Symposium - 1963
|url=https://apps.dtic.mil/sti/pdfs/AD0440764.pdf
|location= Franklin Institute, Philadelphia, Pennsylvania
|publisher= U.S. Army Materiel Command
|pages= 3-1 - 3-22
|archive-url=https://archive.org/details/DTIC_AD0440764/mode/2up
|archive-date=28 May 2018
}}
The ignition charge of the device is a blend of zirconium, potassium perchlorate, Viton B and graphite, often abbreviated as ZPP.{{cite book
|first1=Thomas L.
|last1=Seeholzer
|first2=Floyd Z.
|last2=Smith
|first3=Charles W.
|last3=Eastwood
|first4=Paul R.
|last4=Steffes
|date=1 January 1995
|title= Applications catalog of pyrotechnically actuated devices/systems
|url=https://ntrs.nasa.gov/api/citations/19950011972/downloads/19950011972.pdf
|location= Cleveland, OH
|publisher= NASA Lewis Research Center
|pages= 66–67
|archive-url=https://web.archive.org/web/20220822092153/https://ntrs.nasa.gov/api/citations/19950011972/downloads/19950011972.pdf
|archive-date=22 August 2022
}}
Uses of the device include:
- Setting off pressure cartridges, pocket sized gas generators which in turn pneumatically activate other systems.
- Setting off the NASA standard detonator, which itself activates other systems explosively.
- Triggering Pyrotechnic Circuit Interrupters, severing bundles of electrical cables.
- Triggering explosive valves to open/close pressurization lines or fuel lines.
- Triggering a pyrotechnic pin puller which opens a Marman clamp, 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).{{cite book
|date= 1 January 2009
|title= Apollo Spacecraft and Saturn V Launch Vehicle Pyrotechnics/Explosive Devices
|url=https://ntrs.nasa.gov/api/citations/20090015395/downloads/20090015395.pdf
|location= Houston, TX
|publisher= NASA, Johnson Space Center
|archive-url=https://web.archive.org/web/20220106185435/https://ntrs.nasa.gov/api/citations/20090015395/downloads/20090015395.pdf
|archive-date=6 January 2022
}}
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.{{cite book
|date= 1 March 1973
|title= Apollo Experience Report - Spacecraft Pyrotechnic Systems
|url=https://ntrs.nasa.gov/api/citations/19730011151/downloads/19730011151.pdf
|location= Houston, TX
|publisher= NASA, Lyndon B. Johnson Space Center
|archive-url=https://web.archive.org/web/20201212011306/https://ntrs.nasa.gov/api/citations/19730011151/downloads/19730011151.pdf
|archive-date=12 December 2020
}}
After the Apollo program ended, the Initiator was renamed and re-used on other spacecraft, such as the Space Shuttle.
References
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See also
Category:Pyrotechnic initiators
Category:Spacecraft pyrotechnics
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