I decided to team up with Dynacom and Kosdon for a TRA Level 3 attempt at this year's LDRS XVII Launch at the Bonneville Salt Flats, Utah. 

I will be building one of Dynacom's new 76mm motor mount-equipped Scorpions and will power it with one of Kosdon East's 76mm M1130 motors.

CONSTRUCTION:

The Scorpion is one of Dynacom's flagship kits, a 4.125" all fiberglass airframe standing 80" tall. Since 1987, Eric Haberman and Dynacom have produced high quality, extremely durable, all fiberglass high powered rocket kits.

Their airframes and motor mount tubes are manufactured from G-12 continuous wound E glass filament roving in a matrix of heat resistant epoxy resin and then machine ground to a 0.060" nominal wall thickness.

Their fiberglass tubing, nosecones and tailcones are machine-wound on mandrels and precision ground to provide a smooth running, close fit with mating surfaces -- each component is selectively fit to diametrically match the other.

Bearing surfaces are machined square for full cirumferential load distribution. Dynacom materials have inherently superior axial strength due to the filament winding process.

Dynacom tubing has exceptionally smooth bores that resist degredation from exhaust plume and ejection gases.

Precision ground OD's provide both close dimensional tolerances for structural integrity at coupler and airframe section interfaces and produce low body friction drag.

Their nosecones, tailcones, and transition sections, are hollow wound - a ridged one-piece construction allowing full length access from end to end.

Nosecones and tailcones are typically finished with a one (1) caliber length sleeve; transition sections have a one caliber sleeve on each end. The OD's are wet-sanded and primered, ready for paint.

Dynacom high powered rockets have become the standard in "all-fiberglass" kit construction. Given the materials of construction and the filament winding process, they are able to provide innovative solutions to a majority of structural airframe and dynamic load problems.

Construction of this particular Scorpion began with a careful review of the ultra-detailed instructions and their coordinating CAD blueprints.

These full sized mechanical drawings gives an insight to the incredible amount of detail and precision that goes into every Dynacom kit. Dynacom kits are the closest thing to a mail-order missile you can buy!

Once construction was underway, West Systems 5-to-1 epoxy was used to construct the motor mount and to attach the fins. Then using microballoons added to the epoxy, the fillets were built up and smoothed out.

A new feature on the Scorpion model is a telemetry platform, shown in the picture to the right. This platform runs from the tip of the nose to the back of the payload section coupler, providing more than enough room for mounting even the most complex electronic project or projects.

The telemetry platform is a single G-10 sheet that fits on circular G-10 'centering rings', locating it firmly and securely in the telemetry section. You can then mount components on the front *and* rear of the board!

In the photo to the left, you can see the electronics used to deploy and recover the Scorpion. I have selected an ALTACC accelerometer for primary recovery deployment and an Adept PST-941 timer for redundant backup.

The electronics are mounted to the telemetry board using standard electronics-style aluminum standoffs. You can find these at any large computer or electronics supply house, such as Altex in Dallas, TX. Standard sizes are number 4 and number 6 sizes.

Wire is done with standard Radio Shack stranded core copper wire, with soldered connections covered with heat shrink protective wrap. At juntion points, Dean's RC connectors are used to provide a strong, secure connection without sacrificing quality.

For this particular application, I am only using the primary apogee circuit of the unit, so the wiring harness only connects to the drogue connection. Both the accelerometer and the time are routed through a four conductor cable to the ejection charge in the recovery section of the main airframe, and fire separate flashbulbs located in a single ejection device. This allows for two opportunities to fire the same black powder charge rather than two separate charges that could over pressurize the airframe.

ELECTRONICS:

The Black Sky ALTACC combines an accelerometer and barometric pressure sensor into a single data acquisition systems. There are recovery system outputs based on acceleration integration minimum velocity peak and barometric low altitude (500 feet above ground level). ALTACC provides "pretty good data", for altitude and vehicle performance.

Black Sky Research ALTACC Accelerometer

Data is stored as 'sensor' voltage to allow flexible, unambiguous ground processing. An included software/cable package allows for easy downloading of data for analysis. Future options call for a "Field Data Unit" for easy processing of data in the field.

Acceleration measurement range is +/- 25 G's, where liftoff detection for arming, the unit must see greater than 1.0 G for .25 seconds.

The storage system samples data 16 times per second, with a total storage time of 4.25 minutes. The power requirements for those not using a 9 volt battery is from 7 to 14 volts. Output to the ejection charge is 1.5 amps at 8.5 volts, possible using a fresh 9 volt battery.

An included mounting decal provides accurate mounting locations and arming instructions. Additional labels are available from Black Sky Research to allow you to mount the ALTACC in more than one rocket.

Dimensions are 1.2" wide by 1.5" thick by 3.6" long. Fits inside a 1.5" ID tube and weighs 1.7 ounce with 9 volt battery.

The PST941 Very High Current Staging/Deployment Timer from Adept is used to control staging in multi-stage rockets, airstarting motors or controling drogue and/or main chute deployment in high power rockets. The time is adjustable is 1/10 second increments up to a maximum of 25.5 seconds. There is a special PST941X model which allows one second timing intervals with a maximum of 255 seconds.

Adept™ PST-941 Timer

It has a piezo buzzer to indicate its operational status as well as igniter or deployment charge continuity.

Using a fully charged GE/Sanyo NiCad 9 volt battery, the timer can provide in excess of 12 amps of load current for a two second time period, which is sufficient to fire a cluster of most igniters or a large cluster of electric matches. Using a fresh alkaline battery, the timer will provide one amp of current for two seconds.

Dimensions are 2.25" wide by 1.25" thick by 2.5" high. Fits inside a 2.35" ID tube and weighs 2.5 ounces with battery installed.

The photo to the left shows the side view of the telemetry platform with the mounted electronics. It is a simple, yet sturdy design — something I wanted to maintain in my Level 3 attempt, the KISS principle.

With the electronics completed, it was time to get the rocket ready for final finish. After filing and shaping the fillets on the fins and launch lugs, the rocket was sanded with 80 grit sandpaper in preparation for primer. This rocket has ZERO filler anywhere — it is 100% epoxy and G-10 fiberglass!

In the photo to the right, you can see the construction has been completed and the airframe sitting in primer, awaiting the final colors to be applied. PPG Delstar-brand acrylic enamel automotive finish with Delthane urethane hardener was chosen for its durability along with PPG Krondar acrylic primer.

I prefer automotive paints using a urethane hardener for several reasons: The finish is very tough, it is easy to repair damage without the underlying coats wrinkling up, and the overall quality of the finish is very high! The gloss is just so much better than you can get from a spray can. The investment of a regular automotive spray gun and an automotive touch-up gun to use with my Home Depot air compressor has been some of my best purchases in this hobby.

RECOVERY:

Recovery will be via one Rocketman RC9 parabolic parachute attached to the rocket with the standard Dynacom stainless steel aircraft cables, load-rated quicklinks, and connected to the telemetry section with 3/8" tubular nylon rated at 1000 pounds. All eyebolts have been brazed shut for safety.

PROPULSION:

Frank Kosdon is a pioneer in propulsion technologies, developing some of the highest thrusting motors certified to date. Paul Robinson represents Kosdon on the east coast as Kosdon East and is the sole supplier of 3" (76mm) Kosdon motors.

A new feature on Kosdon's 76mm motor hardware is an external thrust ring built into the motor casing. The ring is stainless steel and is of the Smalley-type continuous circle. Kosdon is currently working an awesome green-flamed reload for their 76mm casings as well as a killer purple, a pumpkin orange and a nice blue-flamed mixture.

The reload of choice for this particular flight is the Kosdon M1130, a 30.9" long motor capable of 5770ns of total impulse. With a 5.1 second burn time and packing 315 pounds of lift (37-to-1 power to weight ratio), the Scorpion is predicted to hit 13,968 feet according to wRASP, along the way hitting Mach 1.46! This should provide for an exciting flight on the Bonneville Salt Flats.

The wRASP data shown above has been corrected for the Bonneville altitude of 4320 feet above sea level.

For more information, Dynacom can be reached at http://www.Dynacom-Inc.com and Kosdon East may be reached by emailing Paul Robinson at This email address is being protected from spam bots, you need Javascript enabled to view it .

FLIGHT:

The flight and entire launch will be chronicled online in this article as it progresses with the final results posted for everyone to enjoy.