The Thunderbolt series of rockets was started as a project to build a high performance two stage rocket for LDRS 10 at Black Rock. The first Thunderbolt was a fiberglass airframe using Dynacom parts with a Kosdon L1350 booster and an Aerotech K250 sustainer. We have no decent picture of this rocket.
With the tremendous thrust of the O10,000 motor Frank Kosdon and Mark Clark saw the potential for a great altitude using it for a booster. For the Thunderbolt 2 the O10,000 was the first stage and an M3700 was to be the second. The M was not the optimum motor but was 2.5" in diameter and had proven to have reliable ignition.
With simulations predicting and altitude of 70,000 plus feet, tracking of apogee was to be a problem. Tests were done with several materials for tracking powder. The most effective was to be Blaze Orange paint pigment from the Day-Glo Company, it is also the most expensive. To be visible a dense cloud would have to be at least one minute of arc, about one inch at 100 yards or 21 feet at 75,000 feet.
To determine the amount of powder to produce a cloud of this size flights were made using a modified LOC EZI-65. Canisters containing the powder and a dispersing charge in a configuration similar to what would be used were launched. Observers were a known distance from the launch site and measured the apparent size if the cloud produced. Actual size was calculated from this.
EZI-65 with an I65 motor and a fin less booster containing an Aerotech I357. The sustainer was ignited by an electric match and sheathed Thermolite. There was 1.5 seconds of the fuse unsheathed and wrapped in fiberglass insulation to provide the necessary delay. Robin Meredith is hooking up the leads at the test at Vicksburg Arizona. Lift off, the I357 produces little smoke.
After the initial tests components were made. The nose cone and transition were machined from aluminum bar stock. Shown here is the original configuration used in the Thunderbolt 2. The cone is nearly solid and the transition is not vented. The same parts were reused in the Thunderbolt 2B however the cone was lightened one pound by hollowing. The transition was vented with six 3/4" holes and lightened 2.5 pounds by removing material from the outside between the O-ring grooves.
The fin cans for both stages were made by Frank. A tube with the correct outside diameter and a very thick wall is used. The fins are welded to the tube and then the inside diameter is cut on a lathe. This is done to prevent the tube from warping during welding and not fit the on motor casing. Welds are filled with Bondo and sanded.
There was concern the stages may drag separate at booster burnout. The timers for the sustainer ignition needed to be in the upper stage. Several options were looked at including external wires and head end ignition. The final solution was to place the timers in the nozzle with the actual igniter on a long dowel. When the motor lights the timers are destroyed. Redundant timers were used as well as a sheathed Thermolite backup.
Thunderbolt 2 being stood up in the tower. All three Thunderbolts were beautifully painted by Brandy Bruce-Sharp. In the picture is Steve Peterson, Jim Cornwell and Mark Clark. The complete rocket stands 16 feet tall and weighed 85 pounds. The many wires which are seen are for starting the timers and for the backup ignition which was wired parallel to the booster motor.
Thunderbolt 2's second stage motor failed at ignition due to the interstage/transition not being vented. It was mistakenly thought the motor would pressurize slowly enough to allow the stages to separate before full thrust.
Recovered parts of the Thunderbolt 2 laid out. The upper stage was on the surface, the booster was in the ground so that only 2 feet stuck out. It was dug by Steve Peterson in about 6 hours.
Upper stage motor casing failed at the forward end splitting the tube. Scratches on the motor casing show the booster fins slide forward at impact until they actually strike the ground and then are pushed back to the position seen here. Nose cone and transition/interstage were unharmed.
It was decided to try again the following year with a similar design, the changes being to vent the interstage and to lighten where ever possible. We went home with the motor casings from Frank.
Thunderbolt 2b in the transport rack at Black Rock with Mark Clark. Assembled rocket with the motors not yet loaded being examined by Ky Michaelson, Pius Morozumi, Judy and Robin Meredith and Dan Hawrylkiw. This rocket was the same size but weighed 75 pounds. The timers used were all Black Sky units. They were in the same locations as before. The back up upper stage motor ignition was still the Thermolite but was ignited as the rocket passed the top of the launch tower. Both rockets used an 80 second delay from liftoff.
Dan, Mark, Robin and Judy. Judy was one of the most valued members of the team as she cooked three meals a day for eleven people. Thunderbolt 2b in the tower. Using the Black Sky timers made for a simpler rocket to setup in the launcher. Vent holes for the interstage can be seen in the photos as well as the wires for the backup ignition at the top of the rails.
Lift Off, booster burn, sustainer burn and tracking powder at 75,000 feet. The booster failed to deploy and impacted the ground 80 feet from the launcher. It was tracked to more than 23,000 feet! After the burn out of the sustainer motor, the rocket was going too fast to leave a visible smoke trail for until forty seconds into the flight. The tracking powder canister formed two distinct clouds; the third is the rocket itself. It was watched through LARGE binoculars and acted as if under parachute for a while. When recovered the parachute was in tatters. The flight was to be visually tracked. Just before the launch the trackers said they were on a three mile baseline. This is to close to track at this altitude. It was decided to launch the rocket anyway with no chance of a track since it was at the end of the waiver and we did not want to wait a year for another chance.
Booster partially dug up. It was decided that it would take forever to dig it all the way out and we cut it 2 feet below grade. Nose cone was found a half a mile from the launch site. It was undamaged after a long fall. The upper stage tumbled after losing the parachute, bent fins and bend at the motor closure can be seem. Threads on the closure stripped on striking the ground. The upper stage peak velocity was just under mach 4, note the paint on the leading edges of the fins is still there. The paint on the tube was burned off by the motor tracking smoke. This is not how it was found! Nose cone was put back on and rocket was balanced on it's nose for the picture.
A video of the Thunderbolt 2b
And the owner of a machine shop who will let us make anything as long as we do not use his name.
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