Final Assembly and Flight

The completed booster and sustainer were mated up for the first time at about 9:00pm on October 12th, a mere 14 hours before the rocket was expected to fly. When you think about it, this was a moment that could have forced us to scrap the project if the components failed to join together properly. We held our breath, line up the two sections, and watched them slide together as perfectly as they were designed to do. It was a fine moment. Then we took them apart again and brought the booster back outside to finish painting.

The one last minute discovery we were unable to compensate for was weight. Not being experienced at rocket projects of this size, we underestimated the weight of the finished rocket and shot past our estimates by 30%. According to the computer simulations we ran, the K550 booster motor was adequate to provide a stable flight, provided we could find a long enough rail. We found an available twelve-foot rail with no trouble, and with projected speed at rail end of about 35 feet per second we knew we were on the edge. We decided to wait until the calmest moment possible to avoid any calamitous weather-cocking.

The liftoff was slow and majestic, and the flight stable. The Standard Missile climbed to about 1200 feet and we anxiously waited for the sustainer to light. And waited. It was quickly obvious that the sustainer motor was not about to ignite. The rocket reached apogee and started to descend. The booster ejection charge blew out the main booster chute, and both the sustainer drogue and sustainer main chutes deployed moments afterward.

After recovering the rocket, it was discovered that the booster ejection was provided by the backup charge in the motor (6 second delay), not by the electronics. We suspect that the slow ascent failed to generate the 4g's sustained over 0.5 seconds required to trigger the G-Wiz flight computers in both the booster and sustainer. We also speculate that the ejection charge was energetic enough to arm the G-Wiz in the sustainer. This is why the deployment charges blew but not the motor igniter. By design, the igniter wires are disconnected when the drogue chute is deployed, so we were spared the anxiety of watching a J135 burn for 7 seconds while floating under its parachutes.

The next anticipated flight will be at the December 22nd meeting of the Arizona High Power Rocketry Association (AHPRA) at the same Rainbow Valley location. Mark will be in Arizona visiting his in-laws, and Rick will be here in spirit. Cory has the task of tracking down an L1000 motor for use in the booster, and we already have the J135 for use in the sustainer. In the mean time we will be test flying our G-Wiz flight computers to make sure they are functioning properly.