29mm Mach Breaker is Almost Done

I have made decent progress lately on the 29mm mach breaker. This should be both the fastest and highest flight I will have done... if it all holds together. The plan is to do the high performance flight in Potter, NY during one of the days of LDRS 31 with clear skies. I decided on the I224 classic motor from Cesaroni. On this motor, the rocket sims to 12,300 feet, mach 1.8, and 73 G's.

At this point, the rocket is fully constructed. All that is left is to prime and paint it, and drill the air sampling holes for the altimeter. I'm excited to use the Pnut altimeter for the first time in this rocket. It's tiny, yet records all flight data, including altitude, velocity, and temperature, and plots it all out versus time with some simple software.

Getting both the tracker and altimeter mounted securely in the payload tube was the biggest challenge for this rocket. Here's how it was done:

The blue tube is the coupler tube, and houses the electronics. The tracker and altimeter both mount onto the assembly with the 2-56 threaded rods and bulkplates holding it all together. The altimeter mounts into the 18mm tube (left in the structure) and the tracker mounts above it between the rods. The forward end (on the right in the picture) of the assembly is retained with the larger bulkplate against the end of the coupler tube. Therefore, all of the force due to acceleration will be transferred through tension on the rods and into the forward bulkhead.

The tracker's support is a simple spruce brace that slides into position against the rubber pad.

The altimeter keys into the slot in the forward bulkplate at the end of the 18mm tube.

The aft bulkplate then goes on. The rubber pad will lessen the blow of 70+ G's. The Kevlar cord also attaches here.

The aft end of the assembled electronics bay. The tracker's antenna hangs down and gets curled on itself to fit into the airframe.

The assembled electronics bay with the nose cone. The nose is 6:1 conical, and solid urethane. The coupler tube plugs into the booster airframe about 3 inches. This will allow a very nice, stiff joint, aiding to eliminate potentially disastrous flex during the high G acceleration.

The Kevlar shock cord mounted deep in the booster airframe, as far back as possible to not interfere with the long motor casing. (the motor actually just touches the ring that the cord is epoxied into)

Next will be my usual prime, fill, sand, repeat, followed by a bright and simple paint scheme. I still need to build the launch tower as well.

Eclipse on a J360 Skidmark

I went to MARS's May 12-13 sport launch and had a beautiful flight with my PML Eclipse. This was the rocket I certified level 2 with in August of 2009. I had only flown it to 2500 feet or so and decided to go a bit higher. I flew a Cesaroni Pro54 3 grain J360 Skidmark. It's a 1016 Newton-second motor, and provides an exciting sound and trail of sparks (like all Skidmark motors).

It was just about out of site at apogee. It reached an altitude of 4078 feet. Despite the very breezy conditions, the rocket still landed very close due to a nice angle into the wind off the pad.

Jim Depape took some very nice photos of the flight:

The End of the Super Weasel

I attempted to launch to 10,000 feet with the Shortened Super Weasel on the Aerotech I59WN-P motor. The weather at URRG's May 5-6 weekend was absolutely perfect: clear skies and light winds from the west, so I was very excited for the chance to fly it.

When it left the launch rail, it immediately began corkscrewing. Rather than stabilize and and head straight up, the corkscrewing got much more violent as the airspeed built. At about 1 second into the flight, the corkscrew intensified to the point where the rocket was tumbling. By 1.5 seconds into the flight, the cardboard tube ripped apart right above the motor casing.

The forward tube with the recovery system and tracker fell and landed in between 2 cars (lucky). The booster section still tumbled violently with the endburning grain providing an entertaining 7 second fall. The booster ended up landing about 6 inches in front of the LCO table where there were about 10 people standing (also very lucky).

All in all, everything but the airframe survived. It turned out that the nozzle on the motor shifted when the motor came up to pressure, causing the unexpected flight pattern. It was a fun flight even though it only reached 1400 feet of the 10,000 I was expecting. It was actually my first in-flight airframe failure.