Note: This is a slightly condensed version of all the information that Mike has produced for his Level 3 project. Visit his homepage to read the additional information and enjoy additional pictures.

Introduction:
This certification flight is scheduled to take place at the first available opportunity after an AeroTech M1315 reload motor can be obtained; most likely on or before July 11, 2002 (or at any other available date at LDRS XXI at Amarillo, Texas).

The rocket was constructed entirely by me using a PML ½ Scale Patriot Missile kit as the starting point. The original kit was designed to use piston ejection and standard motor deployment. Structural changes were made where needed to improve strength and stability and to allow for electronic dual deployment and a wider selection of motors.

Modifications:
Modifications to the original kit include:

• Replaced the 98 mm motor tube with a PML 98 mm extended quick switch.
• Applied two layers of 8.5 oz. fiberglass to the airframe tube for structural strength.
• Tip-to-Tip covering of the fins with 6.0 oz. carbon/fiberglass to lessen the likelihood of fin-flutter.
• Extended the nose cone shoulder to eliminate “cocking”. The original kit design called for the nose cone to be permanently fastened to the payload section, therefore, the shoulder on the kit nose cone was only 3.75 inches long. Because of the short shoulder, the nose cone cocked very easily and was not suitable for reliable ejection charge deployment. Extending the shoulder eliminated the cocking problem.
• Eliminated the piston ejection system.
• Replaced nose cone and payload bulk plates ( ½ inch birch plywood ) with ¾ inch birch plywood bulk plates.
• Replaced 1 inch elastic shock cord with 1 inch nylon strap shock cords.
• Replaced ¼ inch u-bolt shock cord mount(s) with 5/16 u-bolts.
• Replaced booster section shock-cord-to-centering-ring mount with ¾ inch birch plywood bulk plate and 5/16 inch u-bolt.
• Replaced 62 inch main parachute with 140” Rocketman R14C parachute.
• Added dual-deployment electronics bay and ejection baffle system.
• Added 20 ounces of steel shot to the nose cone to obtain proper Center of Gravity with M1315 motor.
• Replaced ¾ inch copper tube launch lugs with 3 delrin rail guides.

General Description

Airframe
The main airframe is constructed of 7.6 inch PML flexible phenolic airframe tube. This material is covered with two layers of 8.5 oz fine weave fiberglass cloth. West Systems 206 hardener and 105 resin were used to apply the fiberglass.

Dimensions Schematic

Booster
The stock .093 inch G10 fins are ¾ inch from the aft end of the airframe. Through-the-wall fin attachment was used. The fins are attached to the PML Quick Switch 98 mm “mother” tube using West Systems 205 hardener and 105 resin with microballoons for fillets and then a six inch wide strip of 5 mil. Kevlar® tape was added. The Kevlar® tape runs up each fin root 1 ½ inches, across the motor tube, and up the adjoining fin root 1 ½ inches. The top and bottom ends of the Kevlar® tape extend approximately one inch up each of the centering rings that lock the fins in place. 206 hardener and 105 resin were used to apply the Kevlar® tape.

Externally, a ½ inch thick fillet was laid down each side of each fin root using a mixture of 205/105 and microballoons. Then a 6.0 oz. layer of carbon/fiberglass cloth was applied tip-to-tip style across each fin using 206/105. Fin surfaces were prepared by roughing them up with 60 grit sandpaper before being covered with the carbon/fiberglass cloth.

The booster shock cord attachment is a 5/16 inch u-bolt attached to a ¾ inch 7-ply birch plywood bulk plate. This bulk plate is attached to the upper motor mount centering ring using three ¼ inch x 1 ½ inch bolts with flat washers, lock washers, and nuts. These bolts pass through the ¾ inch bulk plate and into ¼ inch blind T-nuts that are mounted in the upper motor mount centering ring. Additionally, the ¾ inch ply bulk plate is attached to the airframe using four #4 x 3/8 inch wood screws running through the airframe into the bulk plate.

Payload
The electronics are housed inside the 12 inch phenolic coupler. The coupler is bonded to the payload section using West Systems 206/105. It is further secured by four #4 x 3/8 inch wood screws through the airframe and coupler into the forward ¾ inch plywood bulk plate. That bulk plate is also the mount for 5/16 inch u-bolt shock cord attachment for the main parachute.

Electronics Bay Schematic

The aft bulk plate in the coupler assembly ( ¾ inch plywood ) is removable to allow the two independent electronics bay “pods” to be installed. This bulk plate is attached with three ¼ inch nuts, flat washers, and lock washers to the three 12.5 inch long sections of ¼ inch all-thread that run through the coupler assembly. This bulk plate provides the anchor point for the 5/16 inch u-bolt that connects to the forward end of the apogee deployment shock cord. It is also the attach point for the 44 inch drogue chute.

The two independent electronics pods provide redundant dual deployment. This provides an extra layer of security to help ensure that safe deployment occurs.

The pods share apogee and main deployment baffle chambers but each has its own separate apogee and main deployment system. Each pod supplies its own power and arming switch. Arming for each pod is accomplished with individual two-position key switches that can be accessed externally at the launch pad.

Pod “A” contains a Transolve P6 altimeter and Pod “B” contains an Adept Alts25 altimeter. The P6 will have its SID set for 10 seconds to lessen the possibility that any near-sonic pressure disruption will cause a malfunction. The Alts25 has no need for SID.

Both the P6 and Alts25 arm at 300 ft AGL The P6 is set to deploy at apogee and deploy the main chute at 800 feet AGL. The Alts25 is set to deploy at apogee and at 600 ft. AGL.

When the apogee ejection charge fires, the booster and payload will separate but remain tethered by a 40 foot long 1 inch wide nylon shock cord. A PML 44 inch parachute attached to the aft end of the payload section will act as a drogue chute and is deployed at this time.

When the main deployment charge fires, the nose cone will break the no. 2 nylon screw shear pins and separate from the payload section. The main parachute, a RocketMan R14C, will deploy. The nose cone will separate completely from the main rocket assembly and descend separately on a 45 inch TopFlight parachute.

The RocketMan R14C main parachute is rated for weights from 20 to 35 pounds. The suspended weight at main deployment time ( booster/payload/motor non-consumables ) is estimated to be 28 pounds.

Recovery Schematic

Apogee ejection charges will be 2 grams of 4F black powder each.

Main ejection charges will be 3 grams of 4F black powder each.

Flight Estimates

• The finished dry weight of this vehicle is 28.5 pounds.
• Loaded, pad-ready weight is 41.1 pounds.
• Diameter is 7.6 inches.
• Length is 99 inches.
• Estimated altitude using an AeroTech M1315 motor is from 8,882 feet AGL (wRasp) to 9371 feet (RockSim 4.00).
• Initial thrust-to-weight will be 7.2 to 1.
• Maximum velocity will be approximately 900 feet per second.
• Launch rod velocity on a six foot rail will be 62.1 feet per second; on a 12 foot rail 84.2 feet per second.

SUCCESSFUL LEVEL 3 FLIGHT!

July 11, 2002
LDRS XXI near Amarillo, Texas
Rocket - Modified PML ½ Scale Patriot Missile
Weight - 41.1 lbs
Motor - Aerotech M2400
Altitude 9226 - 9800 Feet

This certification flight took place on July 11, 2002 at LDRS XXI near Amarillo, Texas.

The flight was on an Aerotech M2400 instead of an M1315 as previously indicated. It was the first M motor launched at this year's LDRS.

The flight was successful and reached an altitude between 9226 and 9800 feet, depending on which altimeter you believe. The chutes came out on cue and performed exactly as hoped - drogue at apogee and main at 1200 feet. Then I could breath again.

The nose cone on a separate five foot chute came to rest about 50 feet from the payload/booster on an R14C chute. A little mud, a few scratches, but otherwise no damage at all.