Controlled separation joint
A joint that is separable by detonating a detonating cord within an expanding tube. The joint is held together with a set of bolts. Each bolt is retained on one side of the joint with a lever. The expanding tube is retained under an arm of each lever. When the detonating cord is activated, the tube expands and exerts a force against an arm of each lever, thereby breaking the set of bolts, and allowing the joint to separate. In one example, the separable joint is used to retain a payload fairing on a launch vehicle so that the fairing can be jettisoned during flight.
1. A payload fairing comprising:
a plurality of fairing sections, at least two fairing sections attached to each other with a separable joint, the separable joint comprising:
a plurality of bolts including a bolt that holds the separable joint together, the bolt having a first end retained by a first side of the separable joint;
a lever that retains a second end of the bolt to a second side of the separable joint;
a first channel joined to a second channel by the plurality of bolts, each bolt of the plurality of bolts retained by the first channel with an individual lever of a plurality of levers; and
an expanding tube assembly arranged to exert a force on an arm of the lever, the force capable of causing the bolt to be broken and allowing the at least two fairing sections to be separated, the plurality of levers retaining the expanding tube assembly.
2. The payload fairing of claim 1 , wherein:
the separable joint includes a first U-shaped channel attached to a second U-shaped channel with the bolt;
the lever and the expanding tube assembly are contained within the second U-shaped channel; and
the first end of the bolt is retained in the first U-shaped channel.
3. The payload fairing of claim 2 , wherein:
the bolt is one of a set of bolts that attach the first U-shaped channel to the second U-shaped channel; and
breaking each bolt in the set of bolts allows the first U-shaped channel to be separated from the second U-shaped channel.
4. The payload fairing of claim 1 , wherein separating the separable joint allows the payload fairing to be detached from a launch vehicle.
5. The payload fairing of claim 1 , wherein:
the separable joint includes a plurality of bolts;
each bolt of the plurality of bolts is retained by a corresponding lever of a plurality of levers; and
the plurality of bolts is capable of being broken as a result of activating the expanding tube assembly.
6. A joint assembly, comprising:
a bolt having a first end and a second end, the first end to be retained by a first structure;
a lever to retain the second end of the bolt to a second structure; and
an expanding tube assembly capable of exerting a force on an arm of the lever to cause the bolt to be broken to stop the bolt from preventing separation of the first structure from the second structure, wherein:
the bolt is one of a plurality of bolts;
the joint assembly further comprises a first channel joined to a second channel by the plurality of bolts each bolt of the plurality of bolts retained by the first channel with an individual lever of a plurality of levers;
the expanding tube assembly is positioned along a length of the first channel;
the plurality of bolts are positioned on alternating sides of the expanding tube assembly; and
the plurality of levers retain the expanding tube.
7. The joint assembly of claim 6 , wherein:
the bolt holds the joint assembly together primarily in tension; and
the joint assembly includes a keyway that carries shear loads of the separable joint.
8. The joint assembly of claim 6 , wherein:
the bolt is retained by a threaded hole in the lever; and
the expanding tube is retained by the arm of the lever.
9. The joint assembly of claim 6 , wherein the expanding tube includes flattened portions that are retained by the plurality of levers.
10. The joint assembly of claim 6 , wherein the first channel and the second channel are substantially enclosed to retain pieces of the joint assembly after the bolts are broken.
11. The joint assembly of claim 6 , wherein:
the bolt is a rivet, cap head screw, a hex-head bolt, a pin, a screw, or a section of all-thread; and
a shaft of the bolt includes a narrowed section that is intended to break if the expanding tube is activated.
12. The joint assembly of claim 6 , wherein:
the bolt is retained by a threaded hole in the lever; and
threads of the threaded hole are not counterbored.
13. A method of separating a joint comprising:
detonating an energetic material inside an expanding tube assembly, the expanding tube assembly retained by a lever;
breaking a set of bolts as a result of a force exerted on the lever; and
releasing the joint as a result of breaking the set of bolts, the joint comprising a first channel joined to a second channel by the set of bolts with at least a first bolt of the plurality of bolts retained by the first channel with the lever.
14. The method of separating the joint of claim 13 , further comprising separating the joint.
15. The method of separating the joint of claim 13 , wherein:
the bolt is in the set of bolts that hold the joint together; and
each bolt in the set of bolts is broken to release the joint.
16. The method of separating the joint of claim 13 , wherein:
the force is exerted by detonating the energetic material within the expanding tube assembly; and
the energetic material is made from detonating cord.
17. The method of separating the joint of claim 13 , wherein:
the first channel and the second channel include a keyway; and
a key is located in the keyway to carry shear loads across the joint.
18. The method of separating the joint of claim 13 , wherein the bolt is broken in shear by a force transmitted by the lever.