Path: utzoo!attcan!uunet!nuchat!steve
From: steve@nuchat.UUCP (Steve Nuchia)
Newsgroups: sci.space.shuttle
Subject: Re: Explosive Bolts
Message-ID: <16890@nuchat.UUCP>
Date: 2 Dec 89 14:50:55 GMT
References: <14459@boulder.Colorado.EDU>
Reply-To: steve@nuchat.UUCP (Steve Nuchia)
Organization: Houston Public Access
Lines: 38

In article <14459@boulder.Colorado.EDU> loughry@tramp.Colorado.EDU (J. Loughry) writes:
>How do "explosive bolts" actually work?  Do they contain an internal charge
>with a detonator (sounds like a recipe for a fragmentation grenade--not a good
>thing to have bouncing around the pad during a launch), or is it an external
>shaped charge (like a bolt cutter)?  How do they contain fragments?

I found a book on industrial pyrotechnics in a used bookstore a while
back -- lots of space stuff in it.  It's on loan at the moment though...
check your library.

Anyway, the technical term is "frangible" bolts and nuts.  The mechanical
part is designed with a cavity for the explosive charge and a controlled
weak spot.  Frangible nuts, which seem to be used more than bolts, have
two or more charges and fracture zones.  They thread onto a stud like a
regular nut, then when the charges detonate the nut breaks into pieces
and (falls, flies) out of the way.

Frangible bolts are generally designed to break near the shear line,
although one may want to have the weak spot farther inside one
of the structures.

Anyway, the charges are sized to make the part stop functioning as
a fastener, and the fastener is designed to make that take as little
energy as is practical.  Hardly a recipe for a grenade -- they do
not fragment and the exit velocities are controlled.

And besides, with a few million pounds of SRB thrust in the neighborhood,
who's going to notice a couple of grenades?

Other interesting pryo devices described in the book include the
guillotine (sp?) used to sever the cables between the Apollo CM and
CSM and the linear charge installed in the first few shuttle flights to
open up the sunroof for the ejection seats.
-- 
Steve Nuchia	      South Coast Computing Services      (713) 964-2462
"Man is still the best computer that we can put aboard a spacecraft --
 and the only one that can be mass produced with unskilled labor."
					- Wernher von Braun