--- /dev/null
+<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Goblin 10</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="id2481338"></a>Goblin 10</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="id2736747"></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 1.0</td><td align="left">15 November 2008</td></tr><tr><td align="left" colspan="2">Successful certification flight at Hudson Ranch</td></tr><tr><td align="left">Revision 0.2</td><td align="left">28 October 2008</td></tr><tr><td align="left" colspan="2">Revising during flight to DC</td></tr><tr><td align="left">Revision 0.1</td><td align="left">23 October 2008</td></tr><tr><td align="left" colspan="2">Initial content, derived from YikStik</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="#id2744045">1. Introduction</a></span></dt><dt><span class="chapter"><a href="#id2749934">2. Design</a></span></dt><dd><dl><dt><span class="section"><a href="#id2759790">Overview</a></span></dt><dt><span class="section"><a href="#id2737277">Rocksim File</a></span></dt><dt><span class="section"><a href="#id2763689">Drawing from Rocksim</a></span></dt><dt><span class="section"><a href="#id2744686">Motor Retention</a></span></dt><dt><span class="section"><a href="#id2754969">Nose Cone Electronics Bay</a></span></dt><dt><span class="section"><a href="#id2733689">Electronics</a></span></dt><dd><dl><dt><span class="section"><a href="#id2763384">Avionics</a></span></dt><dt><span class="section"><a href="#id2740504">Stability Evaluation</a></span></dt><dt><span class="section"><a href="#id2748086">Expected Performance</a></span></dt><dt><span class="section"><a href="#id2767164">Recovery System</a></span></dt></dl></dd></dl></dd><dt><span class="chapter"><a href="#id2768933">3. Construction Details</a></span></dt><dd><dl><dt><span class="section"><a href="#id2749141">Airframe</a></span></dt><dt><span class="section"><a href="#id2754017">Nose Cone</a></span></dt><dt><span class="section"><a href="#id2771414">Avionics Bay</a></span></dt></dl></dd><dt><span class="chapter"><a href="#id2745741">4. Recovery Systems Package</a></span></dt><dd><dl><dt><span class="section"><a href="#id2740673">Recovery System Description</a></span></dt><dt><span class="section"><a href="#id2752914">Recovery Initiation Control Components</a></span></dt></dl></dd><dt><span class="chapter"><a href="#id2748101">5. Checklists </a></span></dt><dt><span class="chapter"><a href="#id2750187">6. Flight Summary</a></span></dt><dt><span class="chapter"><a href="#id2764884">7. Analysis and Conclusions</a></span></dt></dl></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id2744045"></a>Chapter 1. Introduction</h2></div></div></div><p>
+ This is a rocket I'm building for my second attempt at a NAR Level 3
+ certification flight. It's basically a Polecat Aerospace Goblin 10 kit
+ augmented with an additional electronics bay in the nose cone, some
+ structural reinforcement, and incorporating a few personal build
+ preferences.
+ </p><p>
+ Preliminary analysis suggests that it should reach just under 7k feet
+ on the Aerotech M1297W reload, and could break two miles on the
+ Cesaroni M795W moon-burner. This means that a certification flight can
+ be supported at Hudson Ranch with the standing 8k waiver, at the Tripoli
+ Colorado site under their higher-altitude window, or at either of the
+ NCR launch sites under their standing waivers.
+ The smallest reasonable motor for this rocket would be a Cesaroni
+ K445 or equivalent, which would yield an apogee of about 2300 feet.
+ </p></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id2749934"></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="#id2759790">Overview</a></span></dt><dt><span class="section"><a href="#id2737277">Rocksim File</a></span></dt><dt><span class="section"><a href="#id2763689">Drawing from Rocksim</a></span></dt><dt><span class="section"><a href="#id2744686">Motor Retention</a></span></dt><dt><span class="section"><a href="#id2754969">Nose Cone Electronics Bay</a></span></dt><dt><span class="section"><a href="#id2733689">Electronics</a></span></dt><dd><dl><dt><span class="section"><a href="#id2763384">Avionics</a></span></dt><dt><span class="section"><a href="#id2740504">Stability Evaluation</a></span></dt><dt><span class="section"><a href="#id2748086">Expected Performance</a></span></dt><dt><span class="section"><a href="#id2767164">Recovery System</a></span></dt></dl></dd></dl></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2759790"></a>Overview</h2></div></div></div><p>
+ The Goblin 10 kit is a simple "four fins and a nose cone" rocket
+ that is short and squat, with a 98mm motor mount.
+ It supports dual-deploy by
+ using the forward end of the long motor mount tube to hold the main.
+ The primary electronics bay is between the forward two motor mount
+ centering rings, accessed by a side hatch. An additional payload bay
+ will be built inside the nose cone to carry experimental altimeters,
+ a tracking beacon, and possibly a GPS position reporting system.
+ </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2737277"></a>Rocksim File</h2></div></div></div>
+ This is the current working design in Rocksim format:
+ <a class="ulink" href="Polecat_Goblin_10.rkt" target="_top"> Polecat_Goblin_10.rkt </a></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2763689"></a>Drawing from Rocksim</h2></div></div></div><span class="inlinemediaobject"><img src="Polecat_Goblin_10.jpg" height="450"></span></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2744686"></a>Motor Retention</h2></div></div></div><p>
+ I will include 8-24 T-nuts in the aft centering ring spaced to allow
+ the use of an Aeropack 98mm retainer and associated 75mm adapter.
+ </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2754969"></a>Nose Cone Electronics Bay</h2></div></div></div><p>
+ Instead of using the supplied nose cone bulkhead, I intend to cut a
+ custom one that would support installing a length of 98mm motor mount
+ from the tip of the nose to the bulkhead. With a plate cut to cover
+ the aft end of the airframe tube, this would form an electronics bay
+ capable of holding a beacon transmitter, GPS system, or other custom
+ electronics.
+ </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2733689"></a>Electronics</h2></div></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2763384"></a>Avionics</h3></div></div></div><p>
+ The recovery system will feature dual redundant barometric altimeters
+ in the main avionics bay between the two forward motor mount
+ centering rings.
+ </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 rotary power switch.
+ A third rotary switch will be used as a SAFE/ARM switch configured
+ to interrupt connectivity to all ejection charges in accordance with
+ NAR certification requirements.
+ </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2740504"></a>Stability Evaluation</h3></div></div></div><p>
+ The Goblin 10 kit designers indicate
+ that the rocket is unconditionally stable with all motors that fit
+ the motor mount geometry. Since we're adding mass at both ends, by
+ putting a payload in the nose cone and by glassing the fins, the
+ overall stability of the design should be retained, but simulation
+ to confirm that seems prudent.
+ </p><p>
+ Thorough analysis using
+ <a class="ulink" href="http://www.apogeerockets.com/rocksim.asp" target="_top">
+ RockSim
+ </a>
+ with various motors ranging from the Cesaroni K445 through the
+ Aerotech M1939W always shows the stability as marginal.
+ This is typical of short fat rockets that don't meet normal length
+ to airframe diameter ratio expectations.
+ Given this, I take the fact that RockSim shows the stability as
+ marginal instead of unstable as strong evidence that the rocket
+ will in fact be stable in flight.
+ I also note that the simulated margin of stability
+ in my as-built configuration is fairly close to the margin of
+ stability of the as-designed model.
+ </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2748086"></a>Expected Performance</h3></div></div></div><p>
+ The Aerotech M1297W reload should carry this vehicle to just under
+ 7000 feet AGL from Colorado Front Range launch sites. It
+ should reach just over 2 miles on a Cesaroni M795 moon burner
+ or equivalent.
+ </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2767164"></a>Recovery System</h3></div></div></div><p>
+ The recovery system will use dual redundant barometric altimeters
+ firing 4F black powder charges using commercial e-matches.
+ At apogee, a drogue chute will deploy with separation of the nose
+ cone. A Giant Leap TAC-1 36 inch chute already in hand will serve
+ as the drogue.
+ At a preset altitude, a main chute will be deployed from the forward
+ end of the motor mount tube to achieve recovery of the bulk of the
+ rocket at approximately 20 ft/sec.
+ </p><p>
+ I intend to sew the main parachute from scratch with my wife's help
+ 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. The anticipated
+ build weight implies that a 10 foot parachute would be appropriately
+ sized.
+ </p><p>
+ The recovery system attachment points will all use 1/4 inch u-bolts
+ with nuts, washers, and backing plates through bulkheads.
+ </p></div></div></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id2768933"></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="#id2749141">Airframe</a></span></dt><dt><span class="section"><a href="#id2754017">Nose Cone</a></span></dt><dt><span class="section"><a href="#id2771414">Avionics Bay</a></span></dt></dl></div><p>
+ I have collected all of my
+ <a class="ulink" href="http://gallery.gag.com/rockets/goblin10" target="_top">
+ build photos
+ </a>
+ in one place, they may show better than I can explain how various
+ aspects of the Goblin went together.
+ </p><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2749141"></a>Airframe</h2></div></div></div><p>
+ The airframe tubing provided in the Polecat kit is thick cardboard tube
+ with a thin exterior fiberglass wrap. To increase airframe strength,
+ and particularly to prevent zippers, additional reinforcement seemed
+ warranted.
+ </p><p>
+ The inner layer of paper was removed from the front 9" or
+ so of the tube. The tube was soaked with West Systems epoxy diluted
+ with about 20% by volume with acetone, and then a carbon fiber wrap was
+ applied to the interior front of the tube and held in place during
+ curing by an inflatable child's bounce toy inside a plastic garbage
+ bag. The result is a substantially strengthened tube, with carbon
+ fiber lining from the leading edge back past the first centering ring.
+ </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2754017"></a>Nose Cone</h2></div></div></div><p>
+ The provided nose cone bulkhead was replaced by a custom centering
+ ring cut from 3/8 inch birch plywood. The ring's outer diameter was
+ adjusted put place the ring approximately an inch forward of the end
+ of the motor mount tube, and the inner diameter was cut to fit Giant
+ Leap 98mm phenolic airframe tubing. A length of such tubing was cut
+ to fit inside the nose cone and extend back to flush with the trailing
+ edge of the ring. The centering ring was drilled and fitted with two
+ u-bolts for recovery system attachment and four 6-32 T-nuts to hold
+ a payload mounting plate in place over the aft end of the 98mm tube.
+ </p><p>
+ The airframe tubing was glued into the tip of the nose cone with West
+ Systems epoxy using both milled glass and microlite filler to thicken
+ the mix. The centering ring was then epoxied in place using a similar
+ mix around the outer edge to form a heavy fillet and 5-minute epoxy to
+ the piece of airframe tubing. After the epoxies cured, a rotary tool
+ was used to cut the airframe tubing off flush with the aft surface of
+ the centering ring.
+ </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2771414"></a>Avionics Bay</h2></div></div></div><p>
+ The avionics bay walls were installed approximately 90 degrees apart
+ prior to installation of the motor mount assembly in the airframe.
+ The airframe wall was marked for a 3.5 x 6.5" access hatch centered
+ over the bay 90 degrees from the rail button line. This allows
+ sufficient room to install the switches on one side of the hatch yet
+ still inside the bay, and to place the static vent on the other side
+ of the hatch so that there will be minimal effect from air disturbed
+ by movement over the hatch cover edges.
+ </p><p>
+ Rails were fabricated from 3/8" birch plywood and 6-32 blind nuts to
+ allow for a removable avionics sled, rectangular, with 4 screws to
+ hold the sled in place.
+ A suitably sized avionics sled should be possible to install and remove
+ through the avionics bay hatch allowing for possible future experiments
+ with alternative avionics.
+ </p></div></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id2745741"></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="#id2740673">Recovery System Description</a></span></dt><dt><span class="section"><a href="#id2752914">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="id2740673"></a>Recovery System Description</h2></div></div></div><p>
+ This rocket uses dual deployment.
+ </p><p>
+ The apogee event separates the nose cone from the
+ airframe. The nose cone is attached to the airframe with a length
+ of heavy-duty tubular nylon shock cord. A drogue chute protected
+ during ejection by a kevlar blanket is attached to the shock cord
+ close to the nose cone end.
+ </p><p>
+ The main is a 10 foot chute sewn from the design documented by
+ <a class="ulink" href="http://www.vatsaas.org/rtv/systems/Parachutes/Chute.aspx" target="_top">
+ Team Vatsaas.
+ </a>
+ It is held in place prior to ejection by a layer of paper taped over
+ the front of the motor mount tube. At ejection, a piston pushes the
+ chute forward through the paper and ejects it from the rocket.
+ This chute is attached to the airframe through an additional length of
+ heavy-duty tubular nylon shock cord.
+ </p><p>
+ Depending on the results of ground testing, the main chute may be
+ packed in a Giant Leap kevlar deployment bag attached at the main
+ chute apex, with a smaller drogue chute deployed to pull off the bag
+ and cleanly deploy the main. The primary motivation for this is to
+ prevent the main chute shrouds from tangling during ejection.
+ </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2752914"></a>Recovery Initiation Control Components</h2></div></div></div><p>
+ The main avionics bay between the forward two centering rings is
+ populated with two commercial altimeters, a PerfectFlite MAWD
+ and a Missile Works miniRRC2.
+ Each is powered by a dedicated 9V alkaline 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>
+ Details of ejection charge design goes here.
+ </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.
+ The formula they suggest is diameter in inches squared times
+ length in inches times a coefficient in grams of black powder.
+ For the main charge, which will be in the 98mm motor mount tube, a
+ pressure of 15psi is appropriate giving a coefficient of 0.006.
+ For the drogue charge, which will be in the main airframe, a
+ pressure of 5psi is more appropriate, leading to a coefficient
+ of 0.002.
+ </p><p>
+ The drogue bay is 10 inches ID at the widest point, but contains
+ the protrusion of the main bay and a decreasing radius in the
+ nose cone. Thus some fudging on the length is appropriate, and
+ we will use 18 inches. That works out to 3.6 grams of BP. This
+ rocket will not fly high enough for there to be a significant
+ effect on BP burn characteristics, so no special compensation
+ should be required.
+ </p><p>
+ The main bay is 3.9 inches ID and perhaps as much as 24 inches long
+ depending on which motor is selected.
+ That works out to 2.2 grams of BP.
+ </p><p>
+ Ground testing yielded 3.5 grams for the apogee charge and 1.5 grams
+ for the main.
+ Backup charges will contain additional BP in accordance
+ with the "blow it off or blow it up" philosophy.
+ </p><p>
+ With a 10 foot Team Vatsaas design parachute and our
+ anticipated build weight, the descent rate under main
+ should be just over 20 feet per second.
+ </p></div></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id2748101"></a>Chapter 5. 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 and adapter parts
+ </li><li>
+ small nylon wire ties
+ </li><li>
+ cellulose wadding material
+ </li><li>
+ masking tape
+ </li><li>
+ screwdriver for phillips-head avionics bay screws
+ </li><li>
+ small straight-blade screwdriver for power switches
+ </li><li>
+ motor reload kit (or arrangements to procure at launch)
+ </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>
+ no mach delay
+ </li><li>
+ 1300 foot main deploy
+ </li></ul></div></li><li>
+
+ miniRRC2
+ <div class="itemizedlist"><ul type="circle"><li>
+ no 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)
+ </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>
+ build and install BP charges
+ <div class="orderedlist"><ol type="1"><li>
+ Drogue Primary Charge - 3.5 grams 4F BP
+ </li><li>
+ Drogue Backup Charge - 4.0 grams 4F BP
+ </li><li>
+ Main Primary Charge - 1.5 grams 4F BP
+ </li><li>
+ Main Backup Charge - 2.0 grams 4F BP
+ </li></ol></div></li><li>
+ fold main chute, connect recovery harness to piston and airframe,
+ install in MMT and tape paper over the front end
+ </li><li>
+ fold drogue chute into a kevlar pad, connect recovery harness to
+ nose cone and airframe, install in airframe
+ </li><li>
+ power up payload using switch on base plate in nose cone, then
+ install nose cone, using masking tape to adjust fit as required
+ </li><li>
+ safely power up altimeters, operate safe/arm switch,
+ and confirm e-match continuity
+ </li><li>
+ safe and power-down the altimeters
+ </li><li>
+ load motor per manufacturer instructions
+ </li><li>
+ install motor in motor mount
+ </li><li>
+ install motor retention
+ </li><li>
+ prepare igniter using e-matches, 1/8 inch 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>
+ confirm reception of signals from payload 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="id2750187"></a>Chapter 6. Flight Summary</h2></div></div></div><p>
+ A successful level 3 certification flight occurred on 15 November 2008
+ at the SCORE Hudson Ranch launch facility. The motor was an Aerotech
+ M1297W provided by Tim Thomas of Giant Leap Motors, the igniter was
+ assembled by James Russell using his special thermite mixture, and
+ numerious SCORE, COSROCS, and NCR members were present to assist with
+ the launch! Great weather for November... mostly clear and sunny,
+ light winds, dry ground, temps above freezing.
+ </p><p>
+ The motor came up to pressure very quickly and the rocket leapt off
+ the pad, climbing smoothly under power and then doing about two slow
+ rolls during the coast phase. Deployment of the nose cone and drogue
+ occurred as planned when the primary apogee charge fired.
+ Unfortunately, the main deployed around the time the backup apogee
+ charge fired, so the descent was under main from apogee. Fortunately,
+ the winds were low enough and the descent rate high enough that the
+ rocket touched down without damage within the waiver area for a
+ successful certification!
+ </p><p>
+ The rocket weighed 25.2 pounds prepared for launch without the motor.
+ The motor weighed about 10.25 pounds, which included about 6 pounds
+ of propellant. Thus the descent mass under chute was just over 29
+ pounds.
+ The miniRRC2 altimeter reported 5949 feet apogee, 980 feet per second
+ max velocity, and 19 seconds to apogee. The MAWD reported 5953 feet
+ apogee.
+ </p><div class="itemizedlist"><ul type="disc"><li><a class="ulink" href="http://picasaweb.google.com/jamesr2/StealeyMemorialLaunchSiteHudsonRanch" target="_top">
+ Photos of the launch taken by James Russell
+ </a></li><li><a class="ulink" href="http://cosrocs.org/all%20other%20videos/2008videos/11-15hudson/bdale_L3.mov" target="_top">
+ Video of the launch taken by Jeff Lane
+ </a></li><li><a class="ulink" href="http://www.youtube.com/watch?v=xaJnl89wfWU" target="_top">
+ Video of the launch taken by Jason Unwin
+ </a></li></ul></div></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="id2764884"></a>Chapter 7. Analysis and Conclusions</h2></div></div></div><p>
+ The ascent was straighter than expected... very smooth during
+ the motor burn, then a couple slow rolls during coast. The two
+ altimeters agreed within 4 feet on the apogee. The max
+ velocity recorded is a little higher than predicted by simulation,
+ but the accuracy of that measurement is likely limited since it is
+ based on pressure data.
+ </p><p>
+ I was able to watch the apogee events through binoculars, and could
+ clearly see the main deploy as the backup apogee charge fired. I saw
+ some evidence of tearing of the paper taped over the motor mount to
+ retain the main chute during ground testing, so assume this was the
+ root cause of the early deployment. When the backup apogee charge
+ fired, the shock cord was not yet in tension, and thus the charge
+ probably kicked the airframe backwards hard enough to allow the main
+ chute to slide out through the torn paper and deploy. The best fix
+ for this might be
+ to fabricate a second piston to use as a cap and retain it with two
+ shear pins. This would be much less likely to prematurely deploy than
+ the current taped paper approach.
+ </p><p>
+ The most significant variance from expectation was the descent rate.
+ The spreadsheet provided by the Team Vatsaas folks for their design
+ suggested we'd see around 21 feet per second. Analysis of the flight
+ profile from the MAWD shows that our actual descent rate was about
+ 32 feet per second. There are three possible sources of error to
+ consider.
+ </p><div class="orderedlist"><ol type="1"><li>
+ The first is descent mass. Pre-flight calculations used
+ 25 pounds.
+ The actual flight weight was 25.2 pounds plus the burn-out
+ weight of the M1297W, which should be about 4.5 pounds.
+ That yields 29.5 pounds total. All pre-flight calculations
+ were done using 25 lbs, with the thought that the motor mass
+ might cancel out against the drag provided by the drogue.
+ In flight, it appeared the drogue supported the nose and the
+ main supported the fin can with very little interaction between
+ the two.
+ </li><li>
+ Second, the dimensions given by Team Vatsaas' spreadsheet
+ for the pattern grid seem small. For a 10 foot chute, they
+ suggest a grid size of 5 inches, which looks more like an 8.5
+ foot finished chute size to me.
+ </li><li>
+ Finally, the Cd in the spreadsheet is 1.5, which may be overly
+ optimistic.
+ </li></ol></div><p>
+ My calculations show that if we assume a chute size of 8.5 feet and
+ a Cd closer to 1, we can get to a descent rate of 32 feet per second.
+ </p><p>
+ So, overall, this was a successful flight, but with three things to
+ change before we fly the airframe again...
+ </p><div class="orderedlist"><ol type="1"><li>
+ the main chute may be too small
+ </li><li>
+ switch to a piston to cap the main chute bay
+ </li><li>
+ beef up the battery retention on the avionics sled
+ </li></ol></div><p>
+ </p></div></div></body></html>
projects / web / gag.com / blobdiff