|K Motor Rocket|
You know the old adage, "If at first you don't succeed" . . .
In 1997 I flew a Cluster-R 4-inch Navy Strike on an Aerotech K250-20 at Blackrock. This was a six-pound rocket, flying on a long-burn K motor, and I hoped for a spectacular flight. This was one of Aerotech's last single-use K motors that included a delay and an ejection charge. The rocket started to lift off the pad, but before it reached the end of the rod, the motor exploded in red and black fire in all directions, incinerating the rocket and leaving a large burning mass. Pius Morizumi and Walter Walby handed me a fire extinguisher, and I ran out to the pyre and sprayed just about all of the foam on it. The foam reduced the flames slightly. The rocket was a complete loss. Everyone laughed and welcomed me deeper into high-power.
In 1998 I flew a K motor rocket at LDRS in the Great Salt Lake. My beautiful wife had given me a kit of a Cluster-R 5.5-inch Standard Arm. This had a core motor of 54 mm and a four cluster of 29 mm motor mounts, into which I inserted four H55-12s and a K250 plugged. I planned to use the classic system: igniting the K250 with a Magnalite and airstarting the four H motors with Thermolite. But, unfortunately, I was talked into trying Blackrock Systems' new ignition system to electrically start all five motors at once. The four H motors ignited perfectly--but the K motor sputted and lagged, so the rocket went up about two thousand feet, and then the whole thing ditched into the salt slag.
In 1999 I built a Rocketdyne Aries. I was impressed with the kit and felt that it was a good value: it was more expensive that the previous two rockets, but its materials were the most solid I'd ever used. I sealed it in finishing epoxy, and this made it seem indestructible (ha!). For some strange reason, I included back-motor hardware, fabricated out of nuts and bolts and a long screw column. In retrospect, this was totally useless because the rocket flew with a plugged motor (duh). The recovery system was a Transolve BUT timer that was supposed to fire a pyrotechnic charge eighteen seconds into the flight. It used a burn wire, which seemed like a fun and excellent way to initiate the event. I used a K1050 plugged motor, and the rocket flew perfectly off the pad in a beefy, authoritative way. My heart soared . . . As the rocket entered the coasting phase at about four thousand feet, it seemed to accelerate. Then the rocket shuddered, and so did I, as it exploded in all directions. What was left of the rocket was now whistling in from half a mile up, plowing straight down into the cruel Blackrock Desert. Everyone was afforded an excellent view as it landed only slightly beyond the away pads. What was recovered resembled an Acme rocket product from a Roadrunner and Coyote cartoon. A spectator commented, "That crash was worth the eight-hour drive up here."
In 2000 . . .
I considered building a rocket from scratch, but considering my dismal history with K motor flights, I decided that a kit from a reputable manufacturer was probably the best way to go. Before I bought a rocket, I had a phone conversation with Karl Baumann; he gave me a recommendation that was simple as well as cryptic: that the optimal length of a rocket is at least 84 inches (7 feet). The Rocketdyne Novastar came in at 90 inches, which was as close as I could find in a kit, and weighed about 8 pounds and had a 5.5 inch diameter. Voila! This met all the criteria that Prefect Baumann recommended. I had the Novastar shipped with a 54 mm mount. The kit was so big, that it was shipped in two parts--one of which came four days before the other.
I was determined to use the G-Whiz Accelerometer, and after inspection of the kit, decided to build the rocket "upside down." I put the motor mount fins and electronic unit into the three-foot-long payload tube and used the five-foot tube as a combined recovery and payload unit (see diagram). Obviously, the rocket separation point was very low, with the recovery chute stuffed up above in the five-foot tube.
I also installed a key switch from Radio Shack. When unlocked, the switch powered up the electronics, which I encased in a 24 mm cut-away rocket tube. I slipped the cut-away tube into a clear plastic 10-inch Lexan tube, so that I could see the arming lights through the plastic. A needed upgrade to the G-Whiz unit was a LED on a wire that could be built into the rocket so that when the ignition switch was thrown, I could see the LED status report.
My intention was to fly the Novastar, which I named "Mr. Green II," on my second day of Blackrock, Saturday July 29, 2000. I arrived on the playa at 9:30 in the morning and started prepping the rocket. I adhered closely to my checklist, going methodically and slowly to make sure everything was correct. At the last minute, I decided to use only one parachute--the standard 64-inch parachute supplied with the kit--tied in the middle of a 15-foot elastic shockcord and attached to a 450-pound-test swivel. All attachments were made with hardware-store quick links. For the recovery separation explosion, I used the WED-1 by Pratt, a small plastic canister with a fliptop and an electric match glued to its bottom. I filled the WED-1 cylinder three-quarters full with black powder and used a Robbie's Mandrill to tamp the powder down. For tracking, I used an entire bottle of OSH red chalk powder; I unscrewed the pointy cap, drilled about twenty 3/8-inch holes into the top of the plastic bottle, and put the bottle inside the rocket with everything else. All the recovery items fit very loosely into the large rocket.
I put in the motor: a K1050 plugged. The rocket weighed in at twenty and a half pounds.
After checking my watch, I was surprised that it was aleady 12:30. It sure was difficult to prep a large rocket!
I took the Novastar to the flight line, and my friend Ed Armani helped me carry it out to a rail pad. After I slipped the rocket onto the pad, I noticed a slight wiggle in the Black Sky Research metal rail guides, so I pulled it off the pad, returned to my Easy Up canopy, and replaced the ten-dollar metal rail guides with two-dollar plastic guides screwed directly into the airframe. I wasn't going to take any chances!
By then, it was 1:00 in the afternoon. I put the Novastar on the pad, and the moment of truth had arrived. This would be my fourth attempt, and I was fearing yet another failure that would put me back to square one . . . ridiculous at this late date. The milk I had for breakfast was curdling in my stomach. The heat was beating down on my head. My mouth was parched.
The countdown began: 5, 4, 3, 2, 1.
The mighty K1050 ignited, and the rocket came alive. It burst off the pad in a totally straight and beautiful liftoff. Within five seconds, it was out of sight completely, and the typical contrail of a slowly spinning screw was all that was left visible in the sky. The rocket had seemed to pick up incredible momentum four seconds into the burn.
We saw the tracking smoke arc waaaay way up there. And then I heard the report of the ejection. I saw a lot of red tracking powder make a thin smear in the heavens. Somebody yelled, "The chute's out!" A pencil dot of flourescent orange parachute could barely be seen. I grabbed my binoculars and watched, transfixed, as the rocket slowly turned on the shock cord attached to the swivel--floating gracefully down to the ground. It kissed the face of the playa about a quarter of a mile away.
I leaped into the Cadillac and drove to get the rocket. The rocket was perfect: all that expoxying paid off. Unfortunately, the G-Whiz unit in the Lexan tube had been thrown out of the rocket at apogee ejection (better mounting next time!), so I had no altitude reading--but later the altimeter was found by someone and turned into the RSO's table, so I got it back.
So what does this all mean?
After four long years, I accomplished my goal. I am now a Real Rocketeer, like the big boys, and will enshrine the Novastar near my worktable in the rocket lab: no more flights for "Mr. Green II." It's hard to say, where does one go from here? Not right to an M motor. No way am I ready for a Level 3 project!