Frangible nut
Encyclopedia
The frangible nut, commonly confused with an explosive bolt, is a component used in many industries, but most commonly by NASA
to sever mechanical connections. It is, by definition, an explosively-splittable nut
. The bolt
remains intact while the nut itself is split into two or more parts.
, which are bolted to the mobile launcher platform
(MLP) until liftoff. On the shuttle, they are separated using a NASA standard detonator
or NSD. The space shuttle uses two NSDs for the frangible nut atop each of the four 28" long, 3.5" diameter bolts holding each SRB to the MLP. Once detonation occurs, the shuttle lifts free of the MLP. The broken nut and any shrapnel from detonation is captured by energy absorption material, such as metal foam
, to prevent damage to the shuttle. In case of NSD failure, or incomplete clearance of the nut from the bolt, the SRB has ample thrust to break the bolt itself and launch unhindered.
Frangible nuts are also used for separation of the two aft structural attachments of the external tank prior to orbital insertion. The attach bolts are driven by the explosive force of the NSDs and a spring into a cavity in the tank strut. The nuts and all residual pieces of the NSDs are caught in a cover assembly within the shuttle.
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
to sever mechanical connections. It is, by definition, an explosively-splittable nut
Nut (hardware)
A nut is a type of hardware fastener with a threaded hole. Nuts are almost always used opposite a mating bolt to fasten a stack of parts together. The two partners are kept together by a combination of their threads' friction, a slight stretch of the bolt, and compression of the parts...
. The bolt
Screw
A screw, or bolt, is a type of fastener characterized by a helical ridge, known as an external thread or just thread, wrapped around a cylinder. Some screw threads are designed to mate with a complementary thread, known as an internal thread, often in the form of a nut or an object that has the...
remains intact while the nut itself is split into two or more parts.
Shuttle usage
Frangible nuts secure the solid rocket boosters (SRB) of the space shuttleSpace Shuttle
The Space Shuttle was a manned orbital rocket and spacecraft system operated by NASA on 135 missions from 1981 to 2011. The system combined rocket launch, orbital spacecraft, and re-entry spaceplane with modular add-ons...
, which are bolted to the mobile launcher platform
Mobile Launcher Platform
The Mobile Launcher Platform or MLP is one of three two-story structures used by NASA to support the Space Shuttle stack during its transportation from the Vehicle Assembly Building to Launch Pad 39-A at the Kennedy Space Center as well as serve as the vehicle's launch platform...
(MLP) until liftoff. On the shuttle, they are separated using a NASA standard detonator
NASA standard detonator
The NASA Standard Detonator is a device used by NASA for applications where a charge must be detonated, usually in conjunction with frangible nuts as a release mechanism. NSDs have been used since the Gemini program, and were used for the Space Shuttle program, including the Solid Rocket Booster ...
or NSD. The space shuttle uses two NSDs for the frangible nut atop each of the four 28" long, 3.5" diameter bolts holding each SRB to the MLP. Once detonation occurs, the shuttle lifts free of the MLP. The broken nut and any shrapnel from detonation is captured by energy absorption material, such as metal foam
Metal foam
A metal foam is a cellular structure consisting of a solid metal, frequently aluminium, containing a large volume fraction of gas-filled pores. The pores can be sealed , or they can form an interconnected network . The defining characteristic of metal foams is a very high porosity: typically...
, to prevent damage to the shuttle. In case of NSD failure, or incomplete clearance of the nut from the bolt, the SRB has ample thrust to break the bolt itself and launch unhindered.
Frangible nuts are also used for separation of the two aft structural attachments of the external tank prior to orbital insertion. The attach bolts are driven by the explosive force of the NSDs and a spring into a cavity in the tank strut. The nuts and all residual pieces of the NSDs are caught in a cover assembly within the shuttle.