Standard Missile Sustainer

The most difficult tasks related to the completion of the sustainer were the beveling of the dorsal fins and the aft control surfaces. This labor intensive effort is described under the Fins and Internal Components section and Brad is very grateful that Mark signed up for this task instead of having to do it himself. Still, there were several design features that are fairly unique to this project. The first two are cosmetic. The third is structural, required to mate the booster and sustainer.

Nose Cone Modification

The LOC Precision stock nose cone, prior to any modification, looks like this (picture from the LOC Precision website of the Mini Magg shown):

The finished Standard Missile nose cone comes to a sharp point and looks like this:

I used the Nose Cone Modification methodology described on the Construction Tips page to reshape the nose cone to look more like the actual missile.

Aft Pivot Fin

The aft fins on the actual missile are two pieces. There is a section that attached to the airframe (pivot fin) and a section that moves to steer the missile (control surface). Mark provided the aft fin is one piece, so Brad cut out eight cardboard silhouettes of the pivot fin and attached them to both sides of the aft fin. This creates the illusion of a two-piece fin.

Coupler Receiver Sleeve

As described on the Booster page, a fiberglass reinforced section of 4" tube extends six inches beyond the upper frustum of the booster assembly. This extension slides inside a fiberglass sleeve in the tail end of the sustainer to connect the two halves of the rocket.

Here's how this sleeve is constructed:

A 6" section of 4" PVC coupler was slit lengthwise and a 1/2" strip (approximately) was removed so that it could be clamped down tight onto a section of 4" Kraft tube using hose clamps. Waxed paper was then wrapped around the Kraft tube. Three wraps of 6 ounce fiberglass and resin were applied to the waxed paper, then the PVC coupler was clamped on tight. After this piece hardened, centering rings were attached and the whole assembly was inserted into the aft end of the sustainer. The motor tube extends into the cavity created by the mating of the Coupler Receiver sleeve and the extension off the Interstage Coupler. Motor retention is provided by a 54mm Slimline retention system.

Wiring

Holes were drilled through the motor tube centering rings and an aluminum tube was run from one tube to the other. During prep, the igniter wires are fed through this tube from the aft end and into the drogue parachute compartment, then taped to the inside of the airframe. The exposed leads are attached to speaker wire connectors from Radio Shack that are installed in the aft payload bay bulkhead. Simple and reliable. Click Here to view the configuration of the avionics and the avionics bay.