--- /dev/null
+<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>YikStik</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="book" lang="en"><div class="titlepage"><div><div><h1 class="title"><a name="id2322390"></a>YikStik</h1></div><div><h2 class="subtitle">A NAR L3 Certification Rocket</h2></div><div><div class="author"><h3 class="author"><span class="firstname">Bdale</span> <span class="surname">Garbee</span></h3></div></div><div><p class="copyright">Copyright © 2008 Bdale Garbee</p></div><div><div class="legalnotice"><a name="id2577753"></a><p>
+ This document is released under the terms of the
+ <a class="ulink" href="http://creativecommons.org/licenses/by-sa/3.0/" target="_top">
+ Creative Commons ShareAlike 3.0
+ </a>
+ license.
+ </p></div></div><div><div class="revhistory"><table border="1" width="100%" summary="Revision history"><tr><th align="left" valign="top" colspan="2"><b>Revision History</b></th></tr><tr><td align="left">Revision 1.2</td><td align="left">12 January 2009</td></tr><tr><td align="left" colspan="2">
+ Document firmware bug in miniRRC2 and possible impact on flight.
+ </td></tr><tr><td align="left">Revision 1.1</td><td align="left">5 December 2008</td></tr><tr><td align="left" colspan="2">
+ Remove embedded images in favor of references to gallery.gag.com
+ </td></tr><tr><td align="left">Revision 1.0</td><td align="left">28 October 2008</td></tr><tr><td align="left" colspan="2">
+ Recording results of first, and only, flight attempt.
+ </td></tr><tr><td align="left">Revision 0.5</td><td align="left">27 September 2008</td></tr><tr><td align="left" colspan="2">
+ Building checklists
+ </td></tr><tr><td align="left">Revision 0.4</td><td align="left">17 September 2008</td></tr><tr><td align="left" colspan="2">
+ Documenting the build process as it happens
+ </td></tr><tr><td align="left">Revision 0.3</td><td align="left">29 March 2008</td></tr><tr><td align="left" colspan="2">
+ Incorporate ideas from James Russell during initial L3CC review
+ </td></tr><tr><td align="left">Revision 0.2</td><td align="left">27 March 2008</td></tr><tr><td align="left" colspan="2">Cleaned up for initial review</td></tr><tr><td align="left">Revision 0.1</td><td align="left">16 March 2008</td></tr><tr><td align="left" colspan="2">Initial content</td></tr></table></div></div></div><hr></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="chapter"><a href="#id2565537">1. Introduction</a></span></dt><dd><dl><dt><span class="section"><a href="#id2565574">Why "YikStik"?</a></span></dt></dl></dd><dt><span class="chapter"><a href="#id2557207">2. Design</a></span></dt><dd><dl><dt><span class="section"><a href="#id2557213">Overview</a></span></dt><dt><span class="section"><a href="#id2557231">Rocksim File</a></span></dt><dt><span class="section"><a href="#id2557244">Drawing from Rocksim</a></span></dt><dt><span class="section"><a href="#id2557261">Airframe Tubing</a></span></dt><dt><span class="section"><a href="#id2557277">Nose Cone</a></span></dt><dt><span class="section"><a href="#id2557288">Fins</a></span></dt><dt><span class="section"><a href="#id2608670">Centering Rings and Bulkheads </a></span></dt><dt><span class="section"><a href="#id2597438">Motor Retention</a></span></dt><dt><span class="section"><a href="#id2599532">Electronics</a></span></dt><dd><dl><dt><span class="section"><a href="#id2612550">Avionics</a></span></dt><dt><span class="section"><a href="#id2589090">Payload</a></span></dt></dl></dd><dt><span class="section"><a href="#id2581651">Stability Evaluation</a></span></dt><dt><span class="section"><a href="#id2581446">Expected Performance</a></span></dt><dt><span class="section"><a href="#id2599074">Recovery System</a></span></dt></dl></dd><dt><span class="chapter"><a href="#id2592234">3. Construction Details</a></span></dt><dd><dl><dt><span class="section"><a href="#id2599259">Airframe and Couplers</a></span></dt><dt><span class="section"><a href="#id2596433">Fins</a></span></dt><dt><span class="section"><a href="#id2606804">Centering Rings and Bulkheads</a></span></dt><dt><span class="section"><a href="#id2588775">Assembling the Booster Section</a></span></dt><dt><span class="section"><a href="#id2584973">Avionics Bay</a></span></dt><dt><span class="section"><a href="#id2606384">Payload Bay</a></span></dt><dt><span class="section"><a href="#id2607348">Recovery System</a></span></dt></dl></dd><dt><span class="chapter"><a href="#id2600260">4. Recovery Systems Package</a></span></dt><dd><dl><dt><span class="section"><a href="#id2595964">Recovery System Description</a></span></dt><dt><span class="section"><a href="#id2609782">Recovery Initiation Control Components</a></span></dt></dl></dd><dt><span class="chapter"><a href="#id2585586">5. Stability Evaluation</a></span></dt><dt><span class="chapter"><a href="#id2606777">6. Expected Performance</a></span></dt><dt><span class="chapter"><a href="#id2611290">7. Checklists </a></span></dt><dt><span class="chapter"><a href="#id2610811">8. Flight Summary</a></span></dt><dt><span class="chapter"><a href="#id2607490">9. Analysis and Conclusions</a></span></dt></dl></div><p>
+ Please note that I stopped adding photos to this document at some
+ point. I have many more photos of the YikStik build, but haven't
+ decided how best to present them yet... update coming someday!
+ </p><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id2565537"></a>Chapter 1. Introduction</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#id2565574">Why "YikStik"?</a></span></dt></dl></div><p>
+ This is the rocket I'm designing for my NAR Level 3 certification flight.
+ The general idea is to build a fairly cheap rocket capable of reliably
+ flying this year's Aerotech level 3 special, which is an M1297W reload.
+ I'd like to be able to fly the prototype of my own altimeter design, and
+ to be able to fly it often on smaller / cheaper reloads at launch sites
+ with modest waivers like Hudson Ranch.
+ </p><p>
+ I want to experiment with vacuum bagging carbon fiber reinforcements, and
+ intend to use my CNC milling machine to cut all the centering rings, etc.
+ The new Giant Leap "Dynawind" tubing feels like a good choice, and if we
+ stick to the 4 inch version we can use a cheap plastic nosecone to keep
+ the cost down.
+ </p><p>
+ Preliminary analysis suggests that a roughly 8 foot rocket made from 4 inch
+ airframe with a 75mm mount and three fins should fly to something around
+ 14k feet on the M1297W, could break three miles on the M1850W, and yet
+ could safely fly on reloads as small as a J for economical fun. Those
+ altitudes mean the certification flight will need to be at a site with a
+ high-altitude waiver like the NCR north site.
+ </p><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2565574"></a>Why "YikStik"?</h2></div></div></div><p>
+ I've always thought the high-gloss red paint job on one of my son's rockets
+ when out on a launch rod in the sun looks a lot like glistening wet
+ lipstick.
+ </p><p>
+ Combine that with the fact that my wife who isn't fond of the stuff
+ refers to lipstick as "yik stick"... and the rest should be obvious.
+ </p><p>
+ My planned paint scheme is a bright red nosecone, gold tube, and black fin
+ can, which is the mental image I have of what lipstick applicators look
+ like, most likely from a stick my mother or one of my grandmothers had
+ when I was a child.
+ </p></div></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id2557207"></a>Chapter 2. Design</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#id2557213">Overview</a></span></dt><dt><span class="section"><a href="#id2557231">Rocksim File</a></span></dt><dt><span class="section"><a href="#id2557244">Drawing from Rocksim</a></span></dt><dt><span class="section"><a href="#id2557261">Airframe Tubing</a></span></dt><dt><span class="section"><a href="#id2557277">Nose Cone</a></span></dt><dt><span class="section"><a href="#id2557288">Fins</a></span></dt><dt><span class="section"><a href="#id2608670">Centering Rings and Bulkheads </a></span></dt><dt><span class="section"><a href="#id2597438">Motor Retention</a></span></dt><dt><span class="section"><a href="#id2599532">Electronics</a></span></dt><dd><dl><dt><span class="section"><a href="#id2612550">Avionics</a></span></dt><dt><span class="section"><a href="#id2589090">Payload</a></span></dt></dl></dd><dt><span class="section"><a href="#id2581651">Stability Evaluation</a></span></dt><dt><span class="section"><a href="#id2581446">Expected Performance</a></span></dt><dt><span class="section"><a href="#id2599074">Recovery System</a></span></dt></dl></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2557213"></a>Overview</h2></div></div></div><p>
+ YikStik is a fairly simple "three fins and a nose cone" dual-deploy
+ rocket using a 75mm motor mount, 4 inch glass-wrapped phenolic airframe
+ with zipperless fin can, plastic nose cone, plywood fins,
+ and lots of glass and carbon fiber reinforcing.
+ The primary electronics bay will be designed to
+ hold two altimeters, and a distinct payload bay may carry an
+ experimental altimeter, GPS receiver, and downlink transmitter.
+ </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2557231"></a>Rocksim File</h2></div></div></div>
+ This is the current working design in Rocksim format:
+ <a class="ulink" href="YikStik.rkt" target="_top"> YikStik.rkt </a></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2557244"></a>Drawing from Rocksim</h2></div></div></div><span class="inlinemediaobject"><img src="YikStik.jpg"></span></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2557261"></a>Airframe Tubing</h2></div></div></div><p>
+ I intend to cut the airframe components from two 48 inch lengths of
+ 98mm Giant Leap Dynawind tubing. The 30 inch main bay and 18 inch drogue
+ bay will be cut from one length, while the 33 inches of fin can, 2 inches
+ of electronics bay, and 8 inches of payload bay will be cut from the
+ second.
+ </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2557277"></a>Nose Cone</h2></div></div></div><p>
+ I intend to use a Giant Leap "Pinnacle" 3.9 inch nose cone.
+ </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2557288"></a>Fins</h2></div></div></div><p>
+ The fins are designed from scratch, and I intend to build them up from
+ two layers of 1/8 inch birch plywood, three layers of carbon fiber, and
+ two layers of 6 oz glass. The stack will be glass, carbon fiber,
+ plywood, carbon fiber, plywood, carbon fiber, glass. The edges of the
+ plywood will be routed to give a modified airfoil shape to the finished
+ fins. The stack will be laminated using West Systems epoxy products
+ and vacuum bagged.
+ The shape is a compromise between mass, surviving Mach-transition stress,
+ optimal stability margin, and avoiding damage during handling and on
+ contact with the ground during recovery.
+ </p><p>
+ The fins will be locked in to milled slots in two of the centering rings,
+ and will be epoxied to the motor mount with glass reinforcing tape.
+ The airframe will be slotted to allow the completed motor mount / fin
+ assembly to be inserted from the rear, with fillets of epoxy applied
+ inside and outside the airframe after insertion.
+ </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2608670"></a>Centering Rings and Bulkheads </h2></div></div></div><p>
+ All centering rings and bulkheads will be custom machined from 3/8 inch
+ birch plywood using my 3-axis CNC milling machine. Some rings will use
+ laminated pairs of 3/4 inch total thickness to enable use of threaded
+ inserts for 1/4-20 rail button screws or deep routing for fin alignment
+ slots.
+ </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2597438"></a>Motor Retention</h2></div></div></div><p>
+ I will embed three 8-24 T-nuts in the aft centering ring spaced to allow
+ the use of home-made Kaplow clips to retain 75mm motors.
+ The same holes may be used to attach custom motor mount adapters for
+ smaller diameter motors.
+ </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2599532"></a>Electronics</h2></div></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2612550"></a>Avionics</h3></div></div></div><p>
+ The recovery system will feature dual redundant barometric altimeters
+ in an electronics bay similar to the LOC design located between the
+ drogue and main parachute bays.
+ </p><p>
+ A PerfectFlite MAWD will be flown as the primary altimeter and to
+ record the flight altitude profile.
+ A MissileWorks Mini-RRC2 will fly as backup altimeter and to
+ directly capture max velocity.
+ </p><p>
+ Each altimeter will have a separate battery and power switch. A 4PDT
+ slide switch will be used as a SAFE/ARM switch configured to interrupt
+ connectivity to the ejection charges.
+ </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2589090"></a>Payload</h3></div></div></div><p>
+ I hope to fly
+ <a class="ulink" href="http://altusmetrum.org/" target="_top">
+ my own altimeter design
+ </a>
+ as a payload in a short payload section just behind the nose cone.
+ I have acquired the pieces to add a GPS receiver and RF downlink using
+ ham radio frequencies to the payload to track the rocket's position
+ during flight.
+ This is not essential to fly,
+ but could make recovery simpler and would just be fun to fly if I can
+ get it all working and suitably ground and/or flight tested in time.
+ </p></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2581651"></a>Stability Evaluation</h2></div></div></div><p>
+ This design has been thoroughly analyzed using
+ <a class="ulink" href="http://www.apogeerockets.com/rocksim.asp" target="_top">
+ RockSim
+ </a>
+ with motors ranging from the
+ Cesaroni J285 through the Aerotech M1850W and appears to be
+ unconditionally stable across that range. The lowest margin is around
+ 1.2 seen with the M1297W planned for my level 3 certification flight,
+ albeit with many masses still only roughly estimated.
+ </p><p>
+ These simulations will be refined as the build proceeds and as-built
+ stability verified before flight.
+ </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2581446"></a>Expected Performance</h2></div></div></div><p>
+ The Aerotech M1297W reload should carry this vehicle without ballast
+ to just over 14 thousand feet AGL. It should make over 16 thousand
+ feet AGL on an M1850W, and should fly stably to roughly 2.5k feet AGL
+ on a Cesaroni J285.
+ </p><p>
+ Hitting optimal mass on the largest motors may require
+ ballast, depending on final build weight.
+ My plan is to fly without ballast on the certification flight,
+ trading some altitude for a slower and softer recovery.
+ If the cert succeeds, then I might try an optimal mass
+ flight sometime later on an M1850W or equivalent "bigger M"
+ reload to join the "three mile club".
+ </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2599074"></a>Recovery System</h2></div></div></div><p>
+ The recovery system will use dual redundant barometric altimeters firing
+ black powder charges.
+ At apogee, a drogue chute will deploy from just forward of the fin can,
+ with size selected for an approximately 100 ft/sec descent rate.
+ At a preset altitude, a main chute will be deployed to achieve recovery
+ of the bulk of the rocket at under 20 ft/sec.
+ The main chute will be packed in a deployment bag, configured as a
+ "freebag" and pulled out of the airframe by a second drogue chute. This
+ drogue will recover the nosecone and deployment bag separately from the
+ remainder of the rocket which will recover under the main.
+ </p><p>
+ I intend to sew the parachutes from scratch using a design documented by
+ <a class="ulink" href="http://www.vatsaas.org/rtv/systems/Parachutes/Chute.aspx" target="_top">
+ Team Vatsaas
+ </a>
+ using 1.9oz rip-stop nylon and 550 lb parachute cord.
+ If time runs short, equivalent chutes from SkyAngle,
+ Rocketman, or Giant Leap could be substituted (at significantly higher
+ cost).
+ </p><p>
+ The deployment bag will probably be purchased from Giant Leap. The
+ recovery harness will probably use tubular kevlar, also from Giant Leap.
+ </p><p>
+ The recovery system attachment points will all use 1/4 inch u-bolts with
+ nuts, washers, and backing plates through bulkheads except for the fin
+ can. The fin can has insufficient room between the motor mount and
+ the airframe inner wall for nuts and washers, so an alternative means of
+ recovery system attachment is required. The fin can will be equipped
+ with either a 3/16 inch stainless steel aircraft cable loop, or a loop
+ of 1/2 inch tubular kevlar, bonded to the motor mount.
+ If available, a screw-eye attached to the forward motor closure may be
+ used instead of or in addition to this recovery attachment loop.
+ </p></div></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id2592234"></a>Chapter 3. Construction Details</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#id2599259">Airframe and Couplers</a></span></dt><dt><span class="section"><a href="#id2596433">Fins</a></span></dt><dt><span class="section"><a href="#id2606804">Centering Rings and Bulkheads</a></span></dt><dt><span class="section"><a href="#id2588775">Assembling the Booster Section</a></span></dt><dt><span class="section"><a href="#id2584973">Avionics Bay</a></span></dt><dt><span class="section"><a href="#id2606384">Payload Bay</a></span></dt><dt><span class="section"><a href="#id2607348">Recovery System</a></span></dt></dl></div><p>
+ I have collected all of my
+ <a class="ulink" href="http://gallery.gag.com/rockets/yikstik" target="_top">
+ build photos
+ </a>
+ in one place, they may show better than I can explain how various
+ aspects of YikStik went together.
+ </p><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2599259"></a>Airframe and Couplers</h2></div></div></div><p>
+ The tubing for the airframe, couplers, and motor mount was all cut
+ using a carefully aligned and adjusted power mitre saw, and the ends
+ lightly sanded to remove rough spots.
+ The main and drogue bays were cut from one 48 inch length of Giant
+ Leap 98mm Dynawind tubing, the fin can, electronics bay, and payload
+ bay were cut from the second. The three couplers for the fin can,
+ electronics bay, and payload bay were cut from Giant Leap 98mm phenolic
+ coupler stock. And the motor mount was cut from Giant Leap 75mm
+ phenolic airframe stock.
+ Note that the motor mount is the longest piece because of
+ the zipperless design with full-length motor mount.
+ </p><p>
+ The airframe tubing selected includes a wrap of 10oz glass in epoxy
+ over the base phenolic tubing (visible in some photos as a
+ shine on the outside of the tubing),
+ but the coupler stock is unreinforced.
+ To ensure the couplers can handle the anticipated loading, I reinforced
+ each with one layer of interior carbon fiber, using the "kitchen
+ vacuum bagging" technique documented by
+ <a class="ulink" href="http://www.jcrocket.com/kitchenbagging.shtml" target="_top">
+ John Coker.
+ </a>
+ </p><p>
+ This was my first hands-on experience working with carbon fiber. The
+ end of the coupler nearest the unit during bagging experienced some
+ crushing of the fibers right at the end. It doesn't matter for this
+ project because each of the couplers will have at least one end fitted
+ with a bulkhead or centering ring, but in the future I'll be tempted
+ to cut the coupler stock a bit long before bagging and trim to length
+ after reinforcing to get "perfect" ends. The technique worked
+ marvelously otherwise, and the resulting couplers look and should work
+ great!
+ </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2596433"></a>Fins</h2></div></div></div><p>
+ Six pieces of 1/8 inch birch plywood were stacked, edge-aligned on what
+ would be the fin root edge, and clamped. The outline of the fin design
+ was marked in pencil, and three 1/8 inch holes drilled through the
+ stack inside the fins to allow using 4-40 screws and nuts to hold the
+ blanks together while making the initial cuts, so that they would all be
+ matched in size. The clamps were removed to avoid interference
+ during cutting. The fin outline was then cut using a radial arm saw.
+ </p><p>
+ A router table with 1/8 inch
+ roundover bit was then used to round over the outer edge, 3 blanks on
+ one side and three on the other. This edge might have been left square,
+ but I prefer the look and feel of rounding. The router table with a 1/2
+ inch diameter straight cutting bit and a fin beveling jig was used
+ to impart a 10-degree bevel on the leading and trailing edge of each fin
+ blank, again 3 on one side and three on the other. The resulting 6
+ blanks thus form 3 pairs of fin components with a modified
+ airfoil shape.
+ </p><p>
+ The fin assembly started with a simple lamination of two layers of ply
+ sandwiching a layer of carbon fiber. Each fin used "one pump" of West
+ Systems epoxy and the stack was vacuum bagged using the Foodsaver with
+ wide bagging material. To keep everything flat while the epoxy cured,
+ the stack of fins was sandwiched between two unused extra shelves for
+ a storage cabinet I had on hand
+ (particle board covered in laminate, very
+ flat and smooth, nearly inflexible at this loading), and stacked with
+ about 75 lbs of loose barbell weights.
+ </p><p>
+ On one of the three fins, the plywood layers are out of alignment by
+ 1-2mm in the longest axis. The other two are nearly perfect. Light
+ sanding should allow me to match them before laminating the outer layers
+ of carbon fiber and glass.
+ </p><p>
+ After the fins cured, they were bulk sanded with medium and fine
+ sandpaper and an electric palm sander. Final sanding of the leading
+ and trailing edges was done using 400 grit paper on a flat surface,
+ holding the fin the way you'd sharpen a knife against a stone. The
+ results seem good, all three fins match pretty closely.
+ </p><p>
+ A fin holding jig was cut from 1/8" hardboard using my rotary tool
+ with a fiber cutoff wheel. The fin slots were made to be a snug fit.
+ A small batch of epoxy was used to apply a bead to the root edge and
+ tab at the leading edge, then the fins were installed against the
+ motor mount and locked into place with the jig to cure. The centering
+ ring that locks the aft edge of the fins was dry-fit during this
+ operation to ensure proper alignment, but was not glued yet. It will
+ go on after the airframe and internal fin filets are installed.
+ </p><p>
+ The fins were reinforced with fiberglass and epoxy. Masking tape was
+ used to carefully delineate where the airframe ID will be, then 6oz
+ glass 14.25" by 3.5" was epoxied fin-fin across the MMT. Strips of
+ 8.6oz "boat tape" fiberglass were worked into the joints with more
+ epoxy, and a sheet of plastic covered by ziplog bags of water were
+ used to hold things in place during the initial curing. The three
+ sides were done one at a time and allowed to cure before proceeding.
+ The results look good, and in combination with internal and external
+ airframe filets should yield a super-strong fin can.
+ </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2606804"></a>Centering Rings and Bulkheads</h2></div></div></div><p>
+ Pairs of 3/8 inch birch plywood blanks were laminated using Titebond
+ wood glue and clamped while curing to form 3/4 inch blanks for centering
+ rings. From a strength perspective, 3/8 inch should suffice, but there
+ are two reasons for going with thicker blanks in some places. The first
+ is that the rail buttons chosen use 1/4-20 mounting screws, and threaded
+ inserts in that size are nearly 3/8 inch outside diameter
+ (and thus would
+ tear up a ring only 3/8 inch thick on insertion). The second is that I
+ like to mill slots in the centering rings on each end of the fins to
+ "lock" the fins into position. Doubling the blanks used to cut those
+ rings will allow me to cut 1/4 inch deep fin slots and still have a half
+ inch of unmolested wood in the rings for strength.
+ </p><p>
+ The aft centering ring and the one just aft of the zipperless
+ coupler section were edge-drilled for the installation of brass
+ 1/4-20 threaded inserts to hold rail buttons. The inserts were
+ locked in place with epoxy, then ground down until nothing protruded
+ beyond the OD of the ring.
+ </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2588775"></a>Assembling the Booster Section</h2></div></div></div><p>
+ The forward two centering rings were installed on the MMT using
+ JB Weld high-temperature epoxy, and incorporating an aircraft cable
+ loop for recovery system retention since there just wasn't room for
+ u-bolts.
+ </p><p>
+ The ring at the leading edge of the fins was initially installed
+ assuming the aft ring would be nearly flush with the rear of the MMT
+ and equipped with Kaplow-clip style retainers, but before the fins
+ were installed a Giant Leap Slimline Tailcone Retainer for 75mm motor
+ in 98mm airframe became available thanks to Tim Thomas, and so this
+ ring was cut out and replaced with another one inch farther forward
+ to allow installation of the tailcone at the rear of the MMT. I
+ really like the tailcone on my Vertical Assault kit, and think it'll
+ work out to be a great addition for this rocket!
+ </p><p>
+ An alignment jig for the fins was carefully marked out and then cut
+ from 1/8 inch hardboard using my rotary tool and abrasive cutoff wheel.
+ The fins were then epoxied at the root and short leading edge to the
+ motor mount tube and into the slots in the forward centering ring,
+ and held rigidly aligned by the jig until the epoxy set. The fins
+ were then masked at what would be the ID of the airframe tube, and
+ reinforced with 6oz glass fin-fin across the motor mount tube between
+ each fin pair, further reinforced with strips of 1 inch glass "boat
+ tape" at each fin root joint.
+ </p><p>
+ The airframe tubing section was carefully marked for fin slots, which
+ were then cut using my rotary tool with abrasive cutoff wheel. Epoxy
+ was applied ahead of the center two rings as the frame was slid into
+ place, and the frame left standing upright until the epoxy set to
+ hopefully form ring-fin fillets on those two rings. The interior
+ fin to airframe joints were reinforced one fin at a time using West
+ Systems epoxy will milled glass as a filler. A long 3/8" dowel was
+ used to place and smooth these interior filets. The aft centering ring
+ was installed by pouring West Systems epoxy in the three fin-fin gaps,
+ placing the ring, then standing the airframe up to allow the epoxy to
+ flow over the forward surface of the ring and into the gaps between it,
+ the motor mount, and the airframe tubing. After it set, the booster
+ was placed nose-down, the airframe gaps behind the fins were taped,
+ and more epoxy was applied to seal the aft of the ring to the tubes.
+ Before this epoxy set, JB Weld was used to glue the tail cone retainer
+ in place on the MMT.
+ </p><p>
+ The exterior fin to
+ airframe joints were filleted using 5-minute epoxy thickened with
+ baby powder and smoothed with the tip of a plastic spoon, which I
+ learned about building the Vertical Assault kit. Gives great results,
+ and allowed all 6 joints to be done in one session. The space
+ above the top surface of the forward centering ring and between the
+ motor mount and zipperless-design coupler tubing was filled with epoxy
+ and milled glass. Minor gaps in the airframe behind each fin were
+ filled with epoxy clay.
+ </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2584973"></a>Avionics Bay</h2></div></div></div><p>
+ The avionics bay contains the two commercial altimeters used to
+ record information about the flight and deploy the drogue and main
+ recovery systems. It is constructed of a piece of Giant Leap 98mm
+ coupler tubing reinforced with an interior wrap of vacuum-bagged
+ carbon fiber, and a 2 inch length of Giant Leap 98mm DynaWind airframe
+ tubing.
+ </p><p>
+ The bulkheads are custom-milled from 3/8 inch birch plywood
+ milled so that about 3/16" fits inside the coupler and the remainder
+ seals the end of the coupler and just fits inside the airframe. Each
+ bulkhead has a u-bolt for attaching the recovery harnesses, and dual
+ CPVC end caps as ejection charge holders with screw terminal blocks
+ from Missile Works to attach the igniters. Two lengths of 1/4 inch
+ all-thread with nuts and washers tie the bulkheads together, with
+ wing-nuts used on one end to allow for easy disassembly.
+ </p><p>
+ A sled was fabricated to hold the altimeters and batteries. It
+ consists of 1/8 inch birch ply laminated with 6oz fiberglass on each
+ side, epoxied to cardboard tubes taken from the packaging for Aerotech
+ igniters that slide over the all-thread, further reinforced with nylon
+ ties at each end. The tubes are staggered one on either side so that
+ the sled goes right up the center of the airframe tubing.
+ </p><p>
+ Two "centering rings" containing three each 6-32 threaded inserts are
+ epoxied inside the bay to provide hard points for attaching the
+ airframe tubes for the drogue and main recovery bays. The inside
+ diameter of these rings is notched for the avionics sled, and thus
+ these rings also provide physical support for the sled.
+ </p><p>
+ Three rotary switches from Missile Works are installed through the
+ short airframe tubing section, drilled such that they end up
+ essentially flush with the outside of the airframe, clamp the coupler
+ tubing, and project inside the bay. Two are wired as SPST switches
+ for power to the two altimeters, the third is wired as a DPST switch
+ that open-circuits the igniters for the required "safe/arm" function
+ called for in the NAR L3 certification requirements.
+ </p><p>
+ The wiring of the avionics bay is documented in the attached
+ schematic diagram. Connectors were used to allow each bulkhead and
+ the switches in the housing to be quickly detached from the sled.
+ The connectors are 9-pin D shells for the switch wiring, and 4-pin
+ Molex connectors like those used on older PC hard drive power cables
+ for the bulkheads. To allow use of a single switch pole for the
+ safe/arm function for each altimeter, the two igniters attached to
+ each altimeter are safed by interrupting the common return lines as
+ shown in the schematic.
+ </p><p>
+ Sizing the static port for the avionics bay was done by applying the
+ formulas suggested by PerfectFlite and Missile Works for their
+ respective altimeter products, then comparing the results with each
+ other and with information found on the web. I've personally had
+ better luck with single ports than with multiple holes, perhaps because
+ I've been working with relatively small rockets. Regardless, I'm
+ sticking with what I know and will use a single static port hole here.
+ </p><p>
+ The measured dimensions
+ of the avionics bay as constructed are 95mm ID and approximately 250mm
+ between bulkheads. This works out to 108.73 cubic inches before
+ accounting for the volume of the sled, electronics, and wiring and
+ other components inside the bay. By the PerfectFlight formula, the
+ static port should be 0.221 inches in diameter. By the Missile Works
+ formula for a bay over 100 cubic inches the answer is 0.261 inches.
+ The closest standard drill size, which happens to split the difference,
+ is 0.250 inches. Easy enough!
+ </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2606384"></a>Payload Bay</h2></div></div></div><p>
+ The construction of the payload bay is very similar to the avionics
+ bay, except that there is a hard-epoxied rear bulkhead, and only one
+ screw ring to hard-mount the nose cone. The forward end of the
+ payload bay is open to the open interior volume of the nose cone in
+ anticipation of extending downlink antennas above the carbon fiber
+ reinforcement in the coupler and into the nose cone, since carbon
+ fiber is opaque to RF.
+ </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2607348"></a>Recovery System</h2></div></div></div><p>
+ Pre-sewn 1/4 inch tubular kevlar harness sections were purchased
+ from Giant Leap, along with a small kevlar deployment bag and two
+ kevlar chute protectors.
+ </p><p>
+ For an apogee drogue, I plan to fly a Public Missiles 4 x 144 inch
+ nylon streamer. It will be protected with one of the kevlar blankets
+ and attached to one of the kevlar harness sections holding the booster
+ to the avionics bay.
+ </p><p>
+ The main parachute will be sewn from 1.9 oz rip-stop nylon purchased
+ from the
+ <a class="ulink" href="http://www.milloutletfabric.com/" target="_top">
+ Mill Outlet Fabric Shop
+ </a>
+ in Colorado Springs. Using the spreadsheet from
+ <a class="ulink" href="http://www.vatsaas.org/rtv/systems/Parachutes/Chute.aspx" target="_top">
+ Team Vatsaas
+ </a>
+ I calculate that we want an 8 foot chute to keep the airframe less
+ nose cone and payload bay below 20 feet per second at touch-down.
+ </p><p>
+ To extract the main chute and recover the nose cone and payload bay,
+ a 3 foot parachute from BSD Rocketry will be packed in a kevlar
+ blanket ahead of the main chute deployment bag, attached by kevlar
+ harness to the nose cone and payload bay assembly, and to the top of
+ the deployment bag. This assembly will recover separately from the
+ rest of the rocket.
+ </p><p>
+ The altimeters are programmed such that the MAWD fires its drogue
+ charge at apogee and its main charge at 1100 feet. The miniRRC2
+ is programmed to fire its drogue charge two seconds past apogee,
+ and its main charge at 900 feet. Thus the MAWD is primary and the
+ miniRRC2 is the backup. Since the M1297W has a burn time of about
+ 5 seconds, mach inhibit is programmed on both altimeters to 8 seconds.
+ </p></div></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id2600260"></a>Chapter 4. Recovery Systems Package</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="#id2595964">Recovery System Description</a></span></dt><dt><span class="section"><a href="#id2609782">Recovery Initiation Control Components</a></span></dt></dl></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2595964"></a>Recovery System Description</h2></div></div></div><p>
+ This rocket uses dual deployment.
+ </p><p>
+ The apogee event separates the
+ airframe between the zipperless-design booster section and the
+ drogue bay. These two sections are linked by a Giant Leap 20 foot
+ pre-sewn 1/4 inch tubular kevlar assembly, attached to which is a
+ Public Missiles 4 x 144 inch red nylon streamer packed in a Giant Leap
+ kevlar chute protection pad.
+ </p><p>
+ The main event separates the airframe between the forward payload bay
+ and the main bay. Attached to the nose cone and payload bay assembly
+ is a Giant Leap 15 foot pre-sewn 1/4 inch tubular kevlar assembly,
+ attached "free bag" style to the top of a Giant Leap deployment bag
+ containing the main chute. A 36 inch BSD Rocketry nylon parachute
+ packed in a Giant Leap kevlar chute protection pad serves to pull the
+ deployment bag off the main chute, after which it allows for safe
+ recovery of the nose cone and payload assembly at just under 20 feet
+ per second.
+ </p><p>
+ The 8 foot main chute is home-made from 1.9 oz rip-stop nylon using
+ the design documented by
+ <a class="ulink" href="http://www.vatsaas.org/rtv/systems/Parachutes/Chute.aspx" target="_top">
+ Team Vatsaas.
+ </a>
+ It is attached to the remainder of the rocket using another Giant Leap
+ pre-sewn 1/4 inch tubular kevlar assembly.
+ </p><p>
+ The anchor points are all 5/16 inch u-bolts, except for on the booster
+ which is equipped with an embedded loop of 3/16 inch stainless aircraft
+ cable. All connections are made with suitable quick-links.
+ </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2609782"></a>Recovery Initiation Control Components</h2></div></div></div><p>
+ The LOC-style avionics bay between the main and drogue bays is
+ populated with two commercial altimeters, a PerfectFlite MAWD
+ and a Missile Works miniRRC2.
+ Each is powered by a dedicated 9V battery, and has a
+ dedicated on/off power switch mounted for access from outside the
+ rocket. Additionally, a single safe/arm switch with two poles is used
+ to interrupt the return circuits from the igniters to each altimeter.
+ See the attached schematic of the avionics bay contents for more
+ details.
+ </p><p>
+ The bulkheads at each end of the avionics bay have two CPVC end caps
+ for ejection charge holders, and two-terminal screw blocks for
+ attachment of electric matches purchase from Giant Leap used to ignite
+ Goex 4F black powder ejection charges. Each charge holder and terminal
+ block pair is labelled as to main or backup since the charges will be
+ different for each.
+ </p><p>
+ The
+ <a class="ulink" href="http://www.info-central.org/recovery_powder.shtml" target="_top">
+ Info Central Black Powder Sizing
+ </a>
+ page is the most authoritative site I've found on this topic.
+ Each of the main and drogue bay interfaces will use 2 2-56 nylon screws
+ as shear pins, each of which needs 35 pounds of force or so to shear.
+ Designing for 15psi puts us between 150 and 200 pounds total force in
+ a 4 inch airframe. The formula is thus 0.006 grams times diameter
+ squared in inches times length in inches.
+ </p><p>
+ My drogue bay is 3.9 inches ID and 8 inches long, or 95.52 cubic
+ inches. That works out to about 0.73 grams. However, there will be
+ some volume in the motor mount tube above the motor that also must
+ be accounted for, enough to nearly double the total volume when flying
+ on the M1297W certification motor. Also, since this charge must fire
+ reliably at 15-18k feet above ground level of around 5k feet, such
+ that combustion is likely to be incomplete, we need to add some margin.
+ </p><p>
+ My main bay is 3.9 inches ID and about 25 inches between bulkheads,
+ or about 298.50 cubic inches. That works out to 2.28 grams.
+ </p><p>
+ Sanity checking, PerfectFlite recommends that a 4F black powder charge
+ be sized by multiplying the volume of the bay in cubic inches by 0.01
+ grams. That yields about 1.8 grams for the drogue bay and 3 grams for
+ the main bay.
+ </p><p>
+ That suggested to me that a good starting point for ground testing is
+ 1.5 grams for the drogue bay and 2.5 grams for the main bay. Ground
+ tests were done using the PC interface cable for the MAWD routed in
+ through the static test port to manually trigger ejections. Testing
+ of the apogee bay showed that 1.5 grams was sufficient for deployment
+ and 1.8 grams was more authoritative. A single test of main deploy
+ with 2.5 grams gave a nearly perfect result.
+ Given the altitude of our expected apogee, we should be generous with
+ the apogee charge, perhaps using 2.0 grams for the primary. The main
+ will deploy at an altitude below where the tests were performed, so
+ no adjustment in charge size should be required.
+ </p><p>
+ Descent rate of the nose cone and payload bay which mass just under
+ 1kg will be less than 20 feet per second with a 36 inch chute based
+ on manufacturer recommendations and Rocksim v8 simulation.
+ Descent rate of the remainder of the rocket under the 8 foot chute
+ should be about 18 feet per second by the spreadsheet provided by
+ the designers of this chute pattern, sanity checked using the descent
+ rate tables of similar commercial parachute designs, like those from
+ The Rocketman.
+ </p></div></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id2585586"></a>Chapter 5. Stability Evaluation</h2></div></div></div><p>
+ Simulation using Rocksim v8 with a variety of motors showed that the
+ rocket is unconditionally stable with all motors likely to be flown.
+ The worst-case stability among 75mm motors is actually with the
+ M1297W chosen for the certification flight, at margin 1.05. This is
+ because the front of this motor falls almost exactly at the CP. Using
+ a longer motor like the M1850W raises the initial stability margin to
+ 1.10 because the front fuel grain is ahead of the CP, and lesser
+ motors also increase the stability because less mass is behind the CP.
+ The smallest motor I can conceive of flying in this rocket (a Cesaroni
+ J285) would leave us overstable with margin 3.79 on the way to about
+ 1800 feet apogee.
+ </p></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id2606777"></a>Chapter 6. Expected Performance</h2></div></div></div><p>
+ On the certification flight, using an Aerotech M1297W reload and
+ associated hardware, the anticipated apogee is round 14,700 feet. This
+ is just under 75% of the NCR North Site standing waiver of 20,000 feet.
+ </p><p>
+ The highest altitude simulated would be achieved with an Aerotech
+ M1850W reload at nearly 18,000 feet. The lowest altitude simulated
+ is with a Cesaroni J285 and Slimline adapters to just over 1800 feet.
+ </p><p>
+ add description of anticipated flight profile here, including launch
+ weight, estimated drag coefficient, velocity leaving the rail, max
+ expected velocity, altitude, and acceleration
+ </p></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id2611290"></a>Chapter 7. Checklists </h2></div></div></div><div class="orderedlist"><ol type="1"><li>
+ Planning
+ <div class="orderedlist"><ol type="1"><li>
+ Pick a club launch with suitable waiver and facilities to
+ support flight.
+ </li><li>
+ Confirm L3CC member(s) available to attend selected launch.
+ </li><li>
+ Confirm that required loaner motor hardware will be available at launch.
+ </li><li>
+ Notify launch sponsor (club president) of intended flight.
+ </li><li>
+ Notify interested friends of intended flight.
+ </li><li>
+ Perform final pre-flight simulation with as-built masses, etc.
+ </li><li>
+ Gather consummables and tools required to support flight
+ <div class="orderedlist"><ol type="1"><li>
+ fresh 9V batteries
+ </li><li>
+ black powder
+ </li><li>
+ e-matches
+ </li><li>
+ motor retainer snap rings
+ </li><li>
+ small nylon wire ties
+ </li><li>
+ cellulose wadding material
+ </li><li>
+ masking tape
+ </li><li>
+ screwdriver for phillips-head airframe screws
+ </li><li>
+ small straight-blade screwdriver for power switches
+ </li><li>
+ motor reload kit
+ </li><li>
+ high temperature grease
+ </li><li>
+ long small diameter dowels for igniter insertion
+ </li></ol></div></li></ol></div></li><li>
+ Before Leaving Home
+ <div class="orderedlist"><ol type="1"><li>
+ program altimeters for suitable mach delay and recovery deployment
+ <div class="itemizedlist"><ul type="disc"><li>
+ MAWD
+ <div class="itemizedlist"><ul type="circle"><li>
+ 8 seconds mach delay
+ </li><li>
+ 1500 foot main deploy
+ </li></ul></div></li><li>
+
+ miniRRC2
+ <div class="itemizedlist"><ul type="circle"><li>
+ 8 seconds mach delay
+ </li><li>
+ 1000 foot main deploy
+ </li><li>
+ 2 seconds apogee delay
+ </li><li>
+ no main delay
+ </li><li>
+ dual deploy
+ </li><li>
+ ops mode 16 (default)
+ </li></ul></div></li></ul></div></li><li>
+ assemble all recovery system components and ensure everything fits
+ </li><li>
+ confirm wiring and operation of altimeter power and safe/arm switches
+ </li><li>
+ Ground test recovery system to confirm suitable black powder
+ charge sizing
+ </li></ol></div></li><li>
+ Pre-Flight
+ <div class="orderedlist"><ol type="1"><li>
+ confirm payload batteries in good condition, bay loaded, power switch works
+ </li><li>
+ confirm reception of signals from transmitter(s) in payload bay
+ </li><li>
+ install fresh 9V batteries for altimeters on avionics bay sled
+ </li><li>
+ inspect altimeters and associated avionics bay wiring for visible faults
+ </li><li>
+ close up avionics bay
+ </li><li>
+ install e-matches, confirming resistance of 1-2 ohms and fit in charge cups
+ </li><li>
+ power up altimeters, operate safe/arm switch, and confirm e-match continuity
+ </li><li>
+ load BP charges into charge cups
+ <div class="orderedlist"><ol type="1"><li>
+ Drogue Primary Charge - 2.0 grams 4F BP
+ </li><li>
+ Drogue Backup Charge - 2.5 grams 4F BP
+ </li><li>
+ Main Primary Charge - 2.5 grams 4F BP
+ </li><li>
+ Main Backup Charge - 3.0 grams 4F BP
+ </li></ol></div></li><li>
+ connect recovery harnesses and install recovery bay airframe sections
+ </li><li>
+ power up altimeters, operate safe/arm switch, and confirm e-match continuity
+ </li><li>
+ safe and power-down the altimeters
+ </li><li>
+ load main recovery bay, attaching nosecone and payload bay assembly
+ </li><li>
+ install nylon 2-56 screws as shear pins between main bay and payload bay
+ </li><li>
+ load drogue recovery bay, feeding harness end through fin can motor tube
+ </li><li>
+ install nylon 2-56 screws as shear pins between drogue bay and fin can
+ </li><li>
+ load motor per manufacturer instructions
+ </li><li>
+ attach forged eye-bolt to forward closure if not already present
+ </li><li>
+ attach drogue harness to eye-bolt on forward motor closure
+ </li><li>
+ install motor in motor mount
+ </li><li>
+ install motor retention snap rings
+ </li><li>
+ prepare igniter for later installation by attaching to long 1/8" dowel
+ </li><li>
+ confirm all screws in place, avionics off and safe
+ </li><li>
+ fill out a launch card
+ </li><li>
+ notify RSO/LCO of readiness for inspection and launch, obtain a rail
+ assignment and permission to move rocket to launch pad for final prep
+ </li><li>
+ coordinate readiness with support team members, photographers, observers
+ </li></ol></div></li><li>
+ Final Prep
+ <div class="orderedlist"><ol type="1"><li>
+ move rocket to launch area
+ </li><li>
+ clean and lubricate launch rail if necessary
+ </li><li>
+ power up payload and confirm reception of signals from transmitter(s)
+ </li><li>
+ mount rocket on launch rail, rotate to vertical
+ </li><li>
+ power up primary altimeter, confirm expected beep pattern
+ </li><li>
+ power up backup altimeter, confirm expected beep pattern
+ </li><li>
+ arm ejection charges
+ </li><li>
+ confirm altimeters both giving expected beep patterns for igniter continuity
+ </li><li>
+ install igniter and connect to launch control system
+ </li><li>
+ capture GPS waypoint for rail location
+ </li><li>
+ smile for the cameras, make sure we have enough "foil Murphy!" shots taken
+ </li><li>
+ retreat to safe area behind LCO
+ </li><li>
+ confirm continued reception of transmitter signal(s) from payload bay
+ </li><li>
+ confirm photographers and observers are ready and know what to expect
+ </li><li>
+ make sure binoculars and backpack with water and recovery tools are at hand
+ </li><li>
+ tell RSO and LCO we're ready to launch
+ </li><li>
+ try to relax and enjoy watching the flight!
+ </li></ol></div></li><li>
+ Recovery
+ <div class="orderedlist"><ol type="1"><li>
+ track rocket to landing site
+ </li><li>
+ capture GPS waypoint of landing site, take lots of photos
+ </li><li>
+ note any damage
+ </li><li>
+ gather up and roughly re-pack recovery system for return to flight line
+ </li><li>
+ bring the rocket to observers for post-flight inspection
+ </li></ol></div></li></ol></div></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id2610811"></a>Chapter 8. Flight Summary</h2></div></div></div><p>
+ YikStik was flown on an M1297W on Saturday morning at NCR's Oktoberfest
+ 2008. The boost was beautiful. Unfortunately, we lost visual as the
+ rocket climbed into high clouds near apogee. Radio tracking signals
+ remained strong for several minutes, then disappeared. We were
+ confused by viewing what we thought was YikStik descending before
+ signals were lost in about the right direction, but now believe we
+ were actually watching a previously launched rocket and did not see
+ YikStik descend. This confusion prevented location of any of the
+ rocket until Sunday evening, after I had left the launch area.
+ </p><p>
+ After an extensive search, the nose cone assembly was finally found
+ with the Walston tracking gear nearly 3.5 miles down range. The
+ remainder of the rocket has not been found despite extensive searching
+ on the ground and from the air.
+ </p><p>
+ Reward if returned posters were placed in the area during the week
+ following the launch but have elicited no useful reponses yet.
+ </p></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id2607490"></a>Chapter 9. Analysis and Conclusions</h2></div></div></div><p>
+ Consideration of how the nose cone ended up where it did suggests
+ we may have had an apogee deployment of the main, perhaps due to
+ stress on the shear pins before launch, during boost, or during
+ apogee drogue deployment causing them to break early.
+ </p><p>
+ It is unfortunate that we were confused by seeing another rocket
+ descending about the expected amount of time after YikStik's launch
+ in approximately the right direction. This caused us to believe that
+ the rocket was much closer than the nose cone turned out to be, causing
+ us to waste a lot of time searching in an area too close to the launch
+ site.
+ It also caused us to assume something really weird had happened to the
+ transmitters, such that the tracking signal was suddenly lost long
+ after the rocket was on the ground, instead of what seems to really
+ have happened, which is that the rocket was farther away descending
+ after a main deployment at apogee, and the loss of signal was simply
+ due to dropping below a ridge line a couple miles from the launch site.
+ I can't help but think that if we'd been
+ looking in the right area sooner after the launch that we might have
+ found the rocket before someone else apparently picked it up.
+ </p><p>
+ I regret the decision to use a "free bag" configuration of the
+ deployment bag.
+ Since both tracking transmitters were in the payload bay behind
+ the nose cone, and we were eventually able to recover that portion
+ of the rocket, it is possible that if the deployment bag were tethered
+ to the main that we might have recovered the remainder of the rocket.
+ </p><p>
+ If the rocket is recovered and able to fly again, the two changes I
+ would like to make are to tether the deployment bag to the apex of the
+ main, and to move from 2-56 nylon screws to 4-40 nylon screws for the
+ main deployment shear pins, ensuring the holes through the airframe
+ are a loose enough fit to avoid stresses on the pins during boost. I
+ have no way to know what happened for sure, but believe this might
+ solve the assumed problem of main deployment at apogee.
+ </p><p>
+ All in all, the design and build process was educational, and a lot
+ of fun! I'm looking forward to fabricating more custom parts using
+ carbon fiber and vacuum bagging in the future.
+ The beautiful boost and obvious survival of the rocket airframe
+ through the expected mach transitions confirms my design and
+ construction skills are adequate to attain an L3 cert.
+ While I hope to recover the remainder of YikStik someday, I won't
+ waste any time before trying again with a new airframe!
+ </p><p>
+ [update] We have learned that one of the altimeters used in this
+ flight, the Missile Works miniRRC2, was subject to a fault in
+ firmware that could cause premature ejection of the main
+ in flights above 10k feet. Thus, it now seems even more likely
+ that we sustained an apogee ejection of the main, but that it
+ may well have been through no fault of the rocket's design,
+ construction, or preparation. Frustrating!
+ </p></div></div></body></html>
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