Sport Rocketry

Well, she hit it exactly on the mark. Once she finished, I glued thin plastic sticks on to create the door and other details. I took my Dremel tool and created the win- dow portal. Once I had the details that looked good, I created a mold from this. The finished mold was flexible, so I used a large tub and put dirt in it and dug out a hole the shape of the BPC and placed the mold in the hole. Once it was secured from bending or bulging, I mixed two-part epoxy and poured it into the mold. This created a solid CM/BPC that is practically indestructible. The result is shown in Figure 16. I used more Plastruct plastic sticks to create the tower section of the Launch Escape System. The LES booster is made from basswood carved to shape. Now back to the business end of the Saturn V. The motor re- tainers were made from PVC screw-on pieces that I purchased at the local hardware store. They just happened to be a good fit for 38mm and 54mm motor tubes. As I mentioned earlier, the motor tubes go all the way through the airframe and end at the bottom of the parachute chamber. Each motor tube was glued to all of the bulkheads throughout to give more strength. Only one motor tube was open to the inside of the parachute chamber. I used this one tube for a motor ejection charge for de- ployment as backup. The motors (one K700 in the center, two I211, and two H123) flown in my Saturn V do not take her to a height that is too high for an apogee deployment. So I used a Magnetic Apogee Detector (MAD) to trigger deploy- ment. The MAD measures the Earth's magnetic field and since the magnetic field has a large vertical compo- nent, the MAD uses the field direction as a reference to sense a rocket's orientation and to set off an ejection charge when the rocket tips over at apogee. For recovery, the upper section used a 10-foot diameter para- chute and the bottom section used a 15-foot diameter parachute. The upper section had one end of the recovery system's Kevlar cord tied to the bottom and the other end tied to a bolt that is screwed into the Service Module (SM). This balanced and held the upper section horizontal during descent to minimize damage to the LES tower as it landed. The lower section parachute cord was tied to the parachute chamber bulkhead in two places to keep that section vertical during descent. The entire rocket weighed in at about 57 pounds. Not bad for a 14-foot-tall model rocket. SPORT ROCKETRY MAY/JUNE 2017 17 Figure 17. Motor end of the Saturn V (one 54mm and four 38mm motor tubes). The motor retainers are screw-on PVC fittings. The bulkhead label pattern is visible here. Figure 19. The completed 1:25-scale Saturn V and launcher alongside the 1:48-scale version for comparison. Figure 18. The Magnetic Apogee Detector. The MAD is located in a chamber below the parachute chamber, accessed through a side hatch in the rocket's body.

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