Scratch - Extreme Paralyzer {Scratch} Original Design / Scratch Built

Contributed by Rick Dunseith

Manufacturer: Scratch
(by Rick Dunseith)

Note: This is a slightly condensed version of all the information that Rick has produced for his Level 3 project.

FinishedProject Overview:

The Extreme Paralyzer is a tube-finned rocket upscaled from a smaller rocket of the author’s own design. The author obtained his TRA Level 1 certification with his Paralyzer, an original-design tube-finned rocket. His Level 2 certification was made with the Ultra-Paralyzer, a 2X upscale of the original Paralyzer. So to continue the trend, the author will make his TRA Level 3 attempt with a 3X upscale of his original Paralyzer rocket.

The Paralyzer series of rockets has had many stable, successful flights on A through C motors (the Mini Paralyzer), G and H motors (the original Paralyzer) and I through K motors (the Ultra Paralyzer). Based on the dozens of successful flights these smaller rockets have had, the author is completely confident in the inherent stability and flight-worthiness of the tube-finned Paralyzer design for his Level 3 attempt.


General Specifications:

The general specifications for the Extreme Paralyzer are as follows:  

  Length: 120.00" Empty Weight: 37.9 lbs   (no recovery system; no motor)
  Diameter:    6.75" Prepped Weight: 47.2 lbs   (recovery system; no motor)
  Tube-Fin Span:   26.25" Liftoff Weight:  59.7 lbs*   (recovery system; full motor)
Burnout Weight: 52.1 lbs*   (recovery system; empty motor)

*based on an Aerotech RMS M1315W motor with a Dr. Rocket 75mm RMS-75/6400 motor casing

Recovery Electronics Schematics:

The following is the wiring schematic for the Extreme Paralyzer’s recovery electronics, shown within a cutaway view of the altimeter bay. Two different altimeters, an R-DAS Classic and a Transolve P5, trigger separate charges for apogee and main deployment charges. For safety, each ejection charge lead is shunted via terminals exposed on the altimeter bay airframe section. Arming of each altimeter is done by twisting together its power leads and pushing them through a static port in the altimeter bay’s airframe.

Electronics

Construction Materials List:
 

Nose Cone: Handmade with plywood forms and two-part expanding foam, fiberglassed with two layers of 6oz. cloth
Airframe: 6 ¾" (outside diameter) Sonotube, fiberglassed with two layers of 6oz. cloth
Motor Tube:  LOC Precision heavy-duty 98mm motor tube
Coupler Section:  6 ¼" (outside diameter) Sonotube, two layers laminated together with 6oz. fiberglass cloth sandwiched in between the layers
Fairings:  ¼"-thick plywood TTW fins, one between each pair of adjacent tube fins, covered with card-stock soaked with CA and then fiberglassed as part of the fin assembly
Tube Fins:  9 ¾" (outside diameter) Sonotube, individually fiberglassed inside with two layers of 6oz. cloth, then covered with another layer of Sonotube with 6 oz. fiberglass cloth sandwiched in between the layers
Bulkheads:  ½"-thick plywood
Centering Rings:  ½"-thick plywood
Misc. Hardware:  ¼" threaded steel rod; ¼" nuts and lock washers; ¼" U-bolts; ¼" T-nuts and threaded inserts; screws
Misc. Electronics:  Wire, two-terminal connectors for altimeter wiring harnesses; terminal strips for altimeter bay bulkheads; shunts and shunt plugs for altimeter bay airframe
Adhesives:  Elmer’s ProBond single-part polyurethane adhesive; Mastercraft 5-minute epoxy; NHP 30-minute epoxy; Flash cyanoacrylate adhesive (CA); PML two-part expanding foam
Fiberglass:  6oz. cloth
Recovery Attachment:  ¼" U-bolts for hard attachment points; ¼" quick-links for shock cord and parachute attachment
Shock Cords:  1" tubular nylon, with loops constructed using CA, epoxy and nylon thread (see HPR magazine, August 1999 issue, page 41 for a description of this technique); Nomex® shock cord protectors
Parachutes:  SkyAngle Cert-3 XXLarge main parachute in SkyAngle deployment bag; SkyAngle 60" parachute for nose cone; Nomex® sheet parachute protectors
Launch Guides:  ¼-20 T-nuts installed in the booster section will accommodate rail buttons for either an Extreme rail or a Unistrut rail

Construction Details:

The Extreme Paralyzer is a scratch-built rocket. The airframe, coupler section and tube fins are fashioned from Sonotube-brand concrete construction form tubes covered with two layers of fiberglass cloth. The nose cone is constructed using plywood forms and two-part expanding foam, carved to shape and covered with a fiberglass skin. Centering rings and bulkheads are cut from ½" plywood, and the fairing fins are cut from ¼" plywood. The fairing shrouds are fashioned from card stock soaked in CA and then covered with a single layer of fiberglass.

Motor Mount Assembly

The motor mount assembly is constructed around a standard 98mm LOC Precision motor tube, 34 inches long. Four ½" plywood centering rings are distributed along its length to center the motor tube within the airframe. One centering ring is placed ¼" from each end of the motor tube, with the other two centering rings 10" apart, centered on the middle of the tube.

Fairing the FinsAlthough the Extreme Paralyzer is a tube-finned rocket, the design includes flat ¼" plywood fairing fins between each pair of tube fins. These through-the-wall fins, which extend out from the airframe only as far as the point at which adjacent tube fins meet, are included to provide extra strength to the overall tube fin assembly and to help transmit thrust load from the motor tube to the airframe. Additionally, they provide structural support for the fairings that extend along the booster section airframe between each pair of adjacent tube fins.

The following steps describe the construction of the motor mount assembly:

Centering Rings
  • four centering rings are cut from ½" plywood, with an inside diameter to fit around the LOC Precision 98mm motor tube, and an outside diameter to fit inside the 6 ½" diameter (6 ¾" outside diameter) Sonotube
  • motor tube is sanded where centering rings are to be attached, ¼" from each end of tube, and 10" apart centered about the middle of the tube
  • centering rings are attached to motor tube using Pro-Bond polyurethane adhesive
  • attachment is reinforced with Pro-Bond fillets on both sides of each centering ring
Fairing Fins
  • five fairing fins are cut from ¼" plywood, with the following dimensions:
    • root chord - 26 ¼"
    • tip chord - 11 ¼"
    • sweep length - 15"
    • semi-span - 2 ½"
    • tab depth - 1 3/8"
  • motor tube is marked for five equally-spaced fins, ¼" wide
  • motor tube is sanded and re-marked where the fairing fins are to be attached
  • three notches are cut along the root edge of each fin, ½" wide and 1 ¼" deep, to fit over the three lower centering rings
  • using epoxy on the root edges of the fins, the five fins are attached to the motor tube at the marked positions
  • attachment is reinforced with Pro-Bond fillets on both sides of each fairing fin
  • fin tips are chamfered to a point to fit into joint between tube fins
Fiberglass between finsFiberglass Reinforcement
  • fairing fins are marked on each side by drawing a line 1 ¼" up from the root edge
  • one layer of 6 oz. fiberglass is applied between each pair of fairing fins
  • fiberglass strips run width-wise from the line marked on one fin, down to the motor tube, across the motor tube, and up to the line marked on the adjacent fin
  • fiberglass strips run length-wise from outside edge of one centering ring, down to the motor tube, along the motor tube, and then up to the outside edge of the adjacent centering ring
Hardware
  • three ¼" U-bolts are installed in the top centering ring, equally spaced around the motor tube; these will form the attachment point for the recovery system, and help to keep the booster section vertical during descent
  • three ¼" threaded rods run the length of the motor mount assembly, connecting each centering ring; they are each attached to one leg of one of the U-bolts in the top centering ring, and nuts and lock washers secure the rods from either side of each of the three lower centering rings; all nuts are coated with epoxy to prevent them from loosening
  • three ¼" T-nuts are installed in the rear centering ring to provide motor retention anchor points
  • one ¼" blind nut is installed in a wooden block screwed to the second centering ring from the rear of the motor tube assembly, to serve as an anchor for attaching the lower rail button to the booster section

Motor Mount Installed

Avionics Section

Two altimeters are mounted in an altimeter bay housed within a coupler that connects the booster and payload sections. To ensure a strong and robust coupler, the walls of the coupler are constructed of two layers of Sonotube laminated together, with a layer of 6 oz. fiberglass sandwiched in between. A 6" long section of airframe tube, cut from 6 ½" Sonotube, is centered on the coupler section. Static ports for the altimeters’ barometric sensors, as well as shunts for the ejection charges, are located in this airframe section.

The following steps describe the construction of the altimeter bay / coupler section:

Lower Coupler Section
  • an 18" section of 6" Sonotube (6 ¼" O.D.) is cut to serve as the outer layer of the lower coupler section, which fits into booster section; this 18" section will also serve as the inner layer of the upper coupler section
  • a 12" section of 6" Sonotube is cut, and a vertical slice is removed so that this section of tube will fit as an inner layer within the 18" section
  • the inner layer is bonded to the inside of one end of the 18" section using Pro-Bondadhesive, with a single layer of 6 oz. fiberglass in between the layers
  • this end of the 18" section forms a 6 ¼" O.D. tube, to fit within the booster section
Upper Coupler Section
  • two 12" sections of 6" Sonotube are cut, and are then split lengthwise to yield two pieces such that each will form half of a 6 ½" O.D. tube; these two pieces will serve as the outer layer of the upper coupler section
  • the two halves of the outer layer are bonded to the outside of the other end of the 18" section using Pro-Bond adhesive, with a single layer of 6 oz. fiberglass in between the layers
  • this end of the 18" section forms a 6 ½" O.D. tube, to fit within the payload section
Airframe Section
  • a 6" section of 6 ½" Sonotube is cut to serve as the airframe section of the altimeter bay
  • the airframe section is fiberglassed with two layers of 6 oz. cloth
  • the airframe section is then bonded around the center of the 18" coupler assembly using Pro-Bond adhesive, with a single layer of 6 oz. fiberglass sandwiched in between
  • four equally-spaced 3/16" holes are drilled around the center of the airframe section, to serve as static ports for the barometric sensors of the altimeters
  • mounting holes are drilled into the airframe section to house the shunts for the four ejection charges
  • banana-plug sockets are mounted in the airframe section to serve as externally-exposed shunt sockets, into which banana-plug shunts will be installed when the electronics for the recovery system are prepped (see schematic in section 2.2)
Lower, Fixed Bulkhead
  • a bulkhead is cut from ½" plywood to fit within the lower coupler section
  • the bulkhead is permanently affixed within the end of the coupler section using Pro-Bond adhesive
  • attachment is reinforced with Pro-Bond fillets on both sides of the bulkhead
  • a ¼" U-bolt is attached to the center of the bulkhead
  • four ¼" holes are drilled in the bulkhead, one pair of holes on either side of the U-bolt; one pair of holes is spaced to correspond to the guide rods for the R-DAS mounting board, and the other pair is spaced for the guide rods for the Transolve mounting board
  • into each of these holes a ¼" threaded rod is inserted; each rod is attached to the bulkhead with nuts and lock washers, which are then coated with epoxy to prevent the nuts from loosening; the rods will serve as the guides for the altimeter mounting boards
  • a terminal strip containing terminals for two pairs of connections is attached to the bulkhead
  • after ejection charge leads are connected to the terminal strip through a small hole drilled in the bulkhead, the bulkhead is covered with a layer of 30-minute epoxy to strengthen it and to provide an airtight seal around the U-bolt, threaded rods and wires
Upper, Removable Bulkhead
  • a ring is cut from ½" plywood to fit within the upper coupler section to provide a ½" wide lip for the upper bulkhead
  • the ring is permanently affixed within the end of the coupler section using Pro-Bond adhesive; the ring is pushed up against the inside layer of the lower bulkhead
  • attachment is reinforced with a Pro-Bond fillet on the underside of the ring
  • a foam rubber gasket matching the shape and size of the plywood ring is cut from a computer mouse pad
  • a disc is cut from ½" plywood to fit within the plywood ring; a second ½" plywood disc is cut to fit within the upper coupler section
  • the two discs are bonded together using Pro-Bond adhesive to form a stepped bulkhead for the upper coupler section
  • a ¼" U-bolt is attached to the center of the bulkhead
  • a terminal strip containing terminals for two pairs of connections is attached to the bulkhead
  • after ejection charge leads are connected to the terminal strip through a small hole drilled in the bulkhead, the bulkhead is covered with a layer of 30-minute epoxy to strengthen it and to provide an airtight seal around the U-bolt and wires
  • four ¼" holes are drilled in the bulkhead, to fit over the four ¼" threaded rods that are permanently affixed to the lower bulkhead; lock washers and wing-nuts are used to tighten the upper bulkhead down against the plywood ring, with the rubber gasket in between to provide an airtight seal

Nose Cone

Nose Cone PartsThe Extreme Paralyzer’s nose cone is scratch-built, using a technique inspired by an article posted on the Rocketry Organization of California's web site entitled "Big Nose Cones" (see http://www.rocstock.org/wizards/bignose.pdf). Plywood profiles create the overall framework for the nose cone. A plywood base plate provides a firm surface to sit atop the payload section airframe. The nose cone shoulder is fashioned from a section of Sonotube and a plywood bulkhead. Two-part expanding foam is used to fill in the framework, and once the foam is carved to shape, two wraps of 6 oz. fiberglass complete the nose cone.

Framework
  • VCP (Visual Centre of Pressure) software is used to print out a full-size profile template of the nose cone
  • two ½" plywood profile forms are cut, using the profile template produced by VCP
  • the plywood forms are slotted so that they interlock at right angles to one another, forming the overall shape of the nose cone and providing a framework for the rest of its construction
  • a ½" plywood disc is cut to the outside diameter of the nose cone, and a cross is cut in the disc so that it can fit over the shoulder portion of the framework to form a base plate for the nose cone
  • holes are drilled throughout the plywood framework pieces to both reduce the weight of the nose cone and to allow the expanding foam to flow between the sections
  • profile forms and base plate disc are assembled with 5-minute epoxy into the framework that will later be foamed and fiberglassed
Nose Cone ShoulderShoulder and Bulkhead
  • a 6" section of 6" Sonotube is cut to serve as the inner layer of the nose cone shoulder
  • a second 6" section is cut to form the outer layer of the shoulder; this section is split lengthwise to allow it to fit over the inner layer, and an additional section of Sonotube is cut to fill in the gap
  • the two layers of the shoulder are bonded together using Pro-Bond adhesive, with a layer of 6 oz. fiberglass sandwiched in between
  • the shoulder is attached to the plywood framework using Pro-Bond adhesive
  • attachment is reinforced with Pro-Bond fillets on the inside of the shoulder, wherever it touches the plywood framework
  • a ½" plywood bulkhead is cut to fit within the shoulder tube
  • a ¼" U-bolt is attached to the center of the bulkhead, and the bulkhead is bonded to the plywood framework using Pro-Bond adhesive and screws
  • attachment is reinforced with Pro-Bond fillets on either side of the bulkhead
  • the bulkhead is covered with a layer of 30-minute epoxy to strengthen it
Nose Cone FoamFoam Core
  • PML two-part expanding foam is mixed and poured into the nose cone shoulder through holes in the nose cone’s base plate, filling the shoulder with polyurethane foam
  • the nose cone framework is inverted and placed within a PML 7 ½" fiberglass nose cone that has been lined with waxed paper to serve as a mould
  • two-part foam is mixed and poured into the fiberglass nose cone in a number of small batches until the entire plywood framework has been enveloped in polyurethane foam
  • the foam-covered framework is removed from the mould and roughly shaped using a utility knife and 60-grit sandpaper
  • lightweight spackle is applied to the foam core to fill in low spots
  • the nose cone is placed into a cradle so that it can be spun with a power drill; final shaping is done while the nose cone is spinning
  • the spinning nose cone is shaped in multiple passes, using first 60-grit sandpaper, then 120-grit sandpaper, and finally 200-grit sandpaper; spackle is applied as necessary between passes to fill in low spots
Glassing Nose ConeFiberglass Shell
  • VCP (Visual Centre of Pressure) software is used to print out a full-size skin template for the nose cone
  • two wraps are cut from 6 oz. fiberglass to the shape and size of the skin template
  • the fiberglass wraps are applied to the foam and spackle nose cone; once dry, excess fiberglass extending beyond the base plate is trimmed off
  • 30-minute epoxy is brushed onto the outside of the nose cone to fill in any low spots prior to final sanding
  • the fiberglassed and epoxied nose cone is spun in its cradle and sanded smooth to prepare it for priming and painting

Payload Section

The payload section is simply a 42" long section of airframe tube, cut from 6 ½" Sonotube (6 ¾" O.D.). The main recovery parachute, deployment bag and shock cord reside in this section, along with the nose cone’s parachute and shock cord. A pressure hole in this section prevents premature deployment caused by a pressure differential during flight, and holes for shear pins allow the nose cone to remain firmly attached to prevent premature deployment of the main parachute when the payload/avionics section is separated from the booster section at apogee. The payload section is attached to the avionics section during flight by bolts that fit into T-nuts in the forward coupler of the avionics section.

Glassing Payload SectionThe following steps describe the construction of the payload section:

  • a 42" section of 6 ½" Sonotube is cut to serve as the payload section airframe
  • the payload section is fiberglassed with two layers of 6 oz. cloth
  • the forward coupler of the avionics section is inserted into the payload section and four equally-spaced ¼" holes are drilled through both, 3" from the end of the payload section tube
  • ¼-20 T-nuts are installed in the holes in the forward coupler of the avionics section, and then short ¼-20 bolts are used to attach the payload section to the avionics section during flight
  • a single 3/16" hole is drilled through the payload section tube 7" from the nose cone end to permit pressure equalization within the payload section during flight
  • the nose cone is inserted into the payload section and four equally-spaced 3/32" shear pin holes are drilled through both, 3" from the end of the payload section tube
  • 3/32" brass tubing is installed into the holes in both the payload section and nose cone shoulder using 5-minute epoxy, and the brass tubing is ground down to be level with the surfaces

Booster Section

First Mock UpThe booster section is the most complex part of the Extreme Paralyzer. Its main component is a 48" long section of airframe tube, cut from 6 ½" Sonotube (6 ¾" O.D.). The motor mount assembly is installed within this section of the airframe, and the tube fins and fairings are attached to the outside of the airframe and to the through-the-wall fins extending through the airframe. The combined avionics and payload sections are connected to the booster section with a shock cord that resides within the booster section during flight. A pressure hole in this section prevents premature separation of the booster and avionics/payload sections caused by a pressure differential during flight, and holes for shear pins allow the avionics/payload sections to be firmly attached to the booster to prevent drag separation at motor burnout.

The following steps describe the construction of the booster section:

Airframe
  • a 48" section of 6 ½" Sonotube is cut to serve as the booster section airframe
  • five evenly-spaced ¼"-wide slots, each 26 ¼" long, are cut from the rear end of the airframe tube; these will accommodate the motor mount assembly’s through-the-wall fins
  • the booster section airframe is fiberglassed with two layers of 6 oz. cloth; when dry, the fiberglass overlapping the slots previously cut in the airframe is cut out
  • a ¼" hole is drilled through the airframe section between two adjacent fin slots, lining up with the location of the lower rail button T-nut installed in the motor mount assembly
  • a 14 ¼" section of 6 ½" Sonotube is cut, and a lengthwise slice is removed so that so that this section of tube will fit as an inner liner within the front end of the booster section
  • the inner layer is bonded to the inside of the front end of the booster section using Pro-Bond adhesive, with a single layer of 6 oz. fiberglass in between the layers
  • the front end of the booster section forms a 6 ¼" I.D. tube, to accommodate the rear coupler of the avionics section
  • a single 3/16" hole is drilled through the booster section tube 7" from the front end to permit pressure equalization within the booster section during flight
  • the rear coupler of the avionics section is inserted into the booster section and four equally-spaced 3/32" shear pin holes are drilled through both, 3" from the end of the booster section tube
  • 3/32" brass tubing is installed into the holes in both the booster section and avionics section rear coupler using 5-minute epoxy, and the brass tubing is ground down to be level with the surfaces
  • a ¼" hole is drilled through the airframe section 7" from the front end, in line with the lower rail button hole; a ¼-20 T-nut is mounted in a ¼" hole drilled through a wooden block, which is then installed within the airframe to serve as an anchor for attaching the upper rail button to the booster section
Installation of Motor Mount Assembly
  • Pro-Bond adhesive is spread on the inside of the airframe at the centering ring positions to fix the motor mount tube within the airframe
  • the motor mount assembly is then inserted into the booster section, with the through-the-wall fins fitting within the slots cut into the airframe tube, and with the front centering ring butting up against the inside layer of the front of the booster section
  • five screws are driven through the airframe and into the top centering ring, evenly spaced around the airframe in line with the TTW fins
  • screws are driven through the airframe and into each of the three lower centering rings, one screw on either side of each TTW fin
  • attachment is reinforced with Pro-Bond fillets on the front of the front centering ring and on the back of the rear centering ring
  • the front of the front centering ring and the back of the rear centering ring are covered with a layer of 30-minute epoxy to strengthen them
  • fillets of Pro-Bond adhesive are applied along the airframe on either side of the through-the-wall fins
  • 5/16" holes are drilled through the airframe beside each through-the-wall fin, adjacent to each centering ring; PML two-part foam is mixed and poured through these holes to expand within the cavities between the motor mount tube and the airframe; foam that expands through the holes is cut off with a sharp knife
Atttaching FinsAttachment of Tube Fins and Fairings
  • five tube fins, each 11 ¼" long, are cut from 9 ½" Sonotube (9 ¾" O.D.)
  • the inside of each tube fin is fiberglassed with two layers of 6 oz. cloth; a balloon blown up within each tube fin holds the fiberglass to the walls of the tube during this step
  • a strip of fiberglass 1" wide and 11 ¼" long is sanded off of the booster section between each pair of adjacent through-the-wall fins to provide a bonding point for the tube fins
  • a tube fin is attached to the booster section airframe between each pair of adjacent through-the-wall fins using Pro-Bond adhesive
  • attachment is reinforced with Pro-Bond fillets on either side of each tube fin where it meets the airframe; additional fillets are applied where each tube fin meets its neighbour, and where each tube fin meets a through-the-wall fin
  • an 11 ¼" long section is cut from 9 ½" Sonotube to serve as an extra layer applied to the exposed outside surface of each tube fin; the extra layer is added to strengthen the tube fins and to reduce recovery damage
  • the two layers of each tube fin are bonded together using Pro-Bond adhesive, with a layer of 6 oz. fiberglass sandwiched in between
  • fairing shrouds are cut from card stock to cover the exposed through-the-wall fins extending up between each tube fin
  • the spine of each fairing shroud is bonded to the edge of a through-the-wall fin using 5-minute epoxy
  • the edges of each fairing shroud are bonded to the airframe, and to the top edges of the two adjacent tube fins, using CA; each fairing is then soaked with CA to harden it
  • each fairing is covered with a single layer of 6 oz. fiberglass to strengthen it
  • PML two-part foam is mixed and poured down into the cavities between the tube fins and their corresponding through-the-wall fins, to expand within the fairings and the cavities around the tube fins; excess foam is trimmed back with a sharp knife and coated with a layer of 30-minute epoxy to protect it from the heat of the motor exhaust

Recovery System

N2000 PrepThe Extreme Paralyzer utilizes a dual-deployment recovery system. The rocket is broken down into three main sections: the booster section, the avionics/payload section, and the nose cone. The avionics section is connected to the payload section during flight, and houses two altimeters, an R-DAS classic and a Transolve P5, to provide redundant electronic deployment functions.

  1. Prepping the Recovery System

    When prepping the vehicle for flight, two ejection charge canisters containing approximately 1.5 grams of black powder are placed in the booster section, below the recovery gear (see Appendix B for a description of the canisters). These are securely taped to the inside of the airframe, resting on the centering ring at the top of the motor mount. These charges are fired by Le Maitre electric matches, which are connected to the apogee deployment terminals of the two altimeters. A Nomex® sheath on the shock cord, as well as a large Nomex® sheet around the shock cord bundle, prevent the apogee ejection charges from burning and damaging the booster section’s recovery harness.

    Ejection CanisterSimilarly, two ejection charge canisters containing approximately 5 grams of black powder are placed in the payload section, again below the recovery gear. These are securely taped to the inside of the upper coupler of the avionics section, resting on the avionics section bulkhead. These charges are also fired by Le Maitre electric matches, which are connected to the main deployment terminals of the two altimeters. A Nomex® sheath on the shock cord, as well as a large Nomex® sheet around the shock cord bundle, prevent the main ejection charges from burning and damaging the payload section’s recovery harness. Similarly, a Nomex® deployment bag protects the main parachute and a large Nomex® sheet protects the nose cone parachute, both of which are packed into the payload section during flight.

    When packed, each shock cord is folded back and forth against itself in one-foot sections in a zig-zag pattern, with each "zig" and "zag" pair taped together with masking tape. The breaking of the masking tape absorbs some of the kinetic energy when two sections of the vehicle are separated by a deployment event.

    Recovery Events During Flight

    Whichever altimeter first detects apogee fires the primary apogee deployment charge. The second altimeter to detect apogee fires a backup ejection charge.

    The first apogee deployment charge to be fired breaks the 1/16" styrene shear pins and separates the booster section from the rest of the vehicle, and a 40’ tubular nylon shock cord keeps the sections connected. A sonic locator beacon attached to the shock cord is activated at this time as well.

    The rocket falls drogueless from apogee to a height of approximately 1200’ before the first of the main deployment charges fires. The R-DAS altimeter is programmed to fire its main charge at 1200’, as detected by a barometric pressure sensor. As a backup to the R-DAS, the Transolve P5 altimeter is configured to fire its main charge at 800’. The airframe of the avionics section contains static ports to allow the altimeter bay pressure to be equalized with the external atmospheric pressure, permitting the two altimeters to trigger their main deployment events at pre-determined altitudes.

    The first main deployment charge to be fired breaks the 1/16" styrene shear pins securing the nose cone, separating the nose cone from the avionics/payload section. A 15’ shock cord connects the nose cone to the main parachute’s deployment bag. A 60" SkyAngle parachute is attached to the nose cone shock cord, five feet from the nose cone end.

    Upon deployment the nose cone parachute acts like a drogue chute, pulling the deployment bag and main chute clear of the payload section and releasing the large SkyAngle Cert-3 XXL main parachute. A 40’ tubular nylon shock cord connects the main parachute to the payload section, and is attached to a U-bolt in the avionics section’s forward bulkhead.

    The nose cone is then recovered separately on its own chute, dangling the deployment bag at the end of its shock cord, while the remaining sections of the vehicle – namely the booster section and the avionics/payload section – are recovered tethered together under the large Cert-3 parachute.

Finishing

All exposed surfaces of the Extreme Paralyzer are covered with at least one layer of fiberglass cloth during the vehicle’s construction.

The finishing of the vehicle is begun by first spraying multiple coats of Krylon-brand sandable primer over all exposed surfaces, sanding between each coat with 120-grit sandpaper. The final coat of primer, once a uniform and smooth surface has been achieved, is sanded with 200-grit sandpaper to prepare it for painting.

The airframe and nose cone are spray-painted with two coats of Krylon-brand "Regal Blue" paint. The airframe is then masked and the fairings and the outsides of the tube fins are spray-painted with two coats of Krylon-brand "Banner Red" paint. Finally, the insides of the tube fins are lightly sanded and then brush-painted with flat black acrylic enamel paint.

The stylized "Paralyzer" decal, upscaled 3X from that created for the original Paralyzer, is printed on an inkjet printer and applied to the payload section with spray adhesive. Three coats of Krylon "Crystal Clear" gloss coating are then sprayed over the entire vehicle to protect its finish and to permanently affix the decal.

Level 3 Flight Day

SUCCESSFUL LEVEL 3 FLIGHT!

Level IIIOctober 12, 2002
Geneseo, NY
Rocket - Scratch Extreme Paralyzer
Weight - 60 lbs
Motor - 75mm Animal Motor Works M1850 Green Gorilla
Altitude - approximately 3500’

My Level 3 attempt took place on Saturday October 12, 2002. It was conducted at a MARS (Monroe Area Rocket Society) launch held at their Geneseo, New York launch site.

The day was perpetually overcast, and although the cloud ceiling prohibited my attempt in the morning, by early afternoon I had the ceiling I needed. It was a cool fall day that kept threatening rain, which luckily never materialized.

I arrived at the field at about 9:00am, and began to unload my gear and set up my prep area. My motor, a 75mm Animal Motor Works M1850 Green Gorilla reload and casing, was delivered to the launch site later that morning.

Preparation of the rocket, its electronics and its recovery system took me until nearly noon, as I slowly and carefully worked my way through my check list, with my Tripoli TAP advisor Ray Halm overseeing and videotaping the process. I then built what was at that time the biggest motor I’d ever seen, and by about 1:00pm I’d secured the motor in the booster section and I was ready for the traditional pickup-truck ride out to the distant launch pad.

I had a lot of help that day, in addition to that provided by my TAP advisor Ray. My wife managed my checklist and made sure I stuck to it. Kathy Miller, fellow BRS and NAPAS member, drove me and my rocket out to the pad in her pickup truck. Bob Quance and his wife Pat documented my entire flight day activities, one using a digital camera and the other using traditional film (their pictures are a cherished record of that wonderful day). Andy Schecter, until that day a stranger to me, helped me get my rocket sections aligned and my shear pins installed. Andy and I then carried the rocket to the pad and, with yet more help from yet more people, we got the rocket on the rail and raised it to its liftoff position.

Based on my simulations I expected a maximum altitude of approximately 3500’, give or take a little. The cloud ceiling had risen to about 4000’ by mid-afternoon, and so the flight was cleared for liftoff. The count down was a very suspenseful 10 seconds indeed.

But I had little to fear. The liftoff and the rest of the flight were picture perfect. The Green Gorilla’s long, bright green flame looked beautiful under the overcast skies. The rocket rode the rail and then proceeded to rise straight and true, thanks to the incredible stability offered by the tube fins. I held my breath, and then exhaled a sign of relief when at motor burnout she held together – the shear pins had done their job, and prevented drag separation (tube fins are very draggy).

Two more tense moments – apogee separation preceding a drogueless descent and then main chute deployment – came and went without a hitch, and the rocket settled softly to the ground under its big SkyAngle Cert-3 XXL chute. The deployment bag configuration for my recovery system worked flawlessly, and I will never be flying big rockets any other way.

After loading the rocket back into the pickup truck, it was a wonderful ride back to the prep area to clean the motor and pack up the rocket. It had been a wonderful day, following nearly a year of design and construction. As Ray signed my Level 3 form, I was finally able to take a moment and realize “I did it; I really did it.” I’m a firm believer in the saying “The journey is the reward.” And although my journey had indeed been very rewarding, the destination was pretty sweet, too.

Subsequent Flights

Carrying it to the Pad

Another M1850

The following year, 2003, saw the Extreme Paralyzer fly three more times. Its second flight was on another AMW M1850 75mm motor at the April 2003 launch in Three Oaks, Michigan. As with the Level 3 flight this one went without a hitch, and Marc Klinger of Big Kid Productions got a beautiful sequence of clear, sharp photographs, documenting the flight from the first sign of smoke on the pad through to the rocket’s graceful descent under its perfectly deployed main and nose cone chutes.

M1419My First 4” Motor

The Extreme Paralyzer’s third flight was back in Geneseo, at the BRS (Buffalo Rocket Society) Invitational launch in May of 2003. I had planned to fly still another 75mm M1850 motor, but at the last minute I was able to secure a 98mm Aerotech M1419. I jumped at the chance to push the rocket a little further on the more powerful 4” motor. This flight was not as straightforward as the first two had been, though. After a beautiful liftoff, boosting straight and true as always, there was a loud bang and then the motor suddenly shut down and went silent only a few hundred feet up – my first high-powered CATO. The rocket began coasting, and I was sure it was going to be destroyed, not having gained enough altitude to properly deploy its chutes.

But after coasting for a few seconds the motor came back to life, although with a drastically-reduced, off-centre thrust. The rocket laboured to gain altitude under the reduced thrust, and was corkscrewing as it went. As a testimony to the stability of a tube finned design, though, the rocket continued to climb until the motor burned out, gaining enough altitude to correctly and fully deploy the recovery system. The rocket was recovered undamaged.

A post mortem revealed that the motor’s nozzle had failed, and almost half the nozzle was missing. That explained the off center thrust, and also severely damaged the casing I’d rented from a vendor. Aerotech has acknowledged the failure and will be replacing the vendor’s reload and casing.

N2000My first ‘N’ Motor

The fourth flight of the Extreme Paralyzer was powered by an Aerotech N2000, a 4" diameter, 42" long, six-grain, 27 lb., 13,452 Ns White Lightning motor. I had not really intended to fly an ‘N’, it just sort of happened. When I was talking to my motor vendor about motors for the BRS BuffRoc launch planned for August, 2003 in Geneseo, I jokingly asked if he had any ‘N’ motors. When he said he did have an Aerotech N2000, I though “Hmmmm, why not?”

By reverse-engineering a reasonable Cd value from the altimeter data of my first few flights I was able to determine a Cd of 1.68 (like I said, tube fins are very draggy). Using that Cd I was able to run simulations that showed my rocket would stay under the Geneseo waiver even on an N2000 motor.

Preparing for the N flight was straightforward. I merely had to alter my recovery configuration in the booster section and build a three-inch thrust ring to accommodate the motor’s 42” length. But let me tell you, building a motor that big, with its six huge fuel grains, was a remarkable experience.

After a small group of fellow flyers helped me get the rocket out to the launch pad and assembled and racked, the N2000 did not disappoint. On a huge flame nearly as long as the rocket, it propelled the 80 lb. Extreme Paralyzer to a height of approximately 7225’, and it did it as effortlessly as an A8-3 lifts an Estes Alpha. After descending drogueless for more than a mile, the main chute was deployed almost right overhead, and the rocket settled to the ground not more than a few hundred feet from the prep area.

The N2000 flight was certainly the highlight of my rocketry career, and every so often I just sit for a while and replay that flight over and over in my head. It was an incredible experience.

Photos are from Rick Dunseith, Bob Quance, Bob Taylor and Rob French

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