X-Git-Url: https://git.gag.com/?p=web%2Fgag.com;a=blobdiff_plain;f=rockets%2Fairframes%2Fyikstik%2Findex.html;fp=rockets%2Fairframes%2Fyikstik%2Findex.html;h=0000000000000000000000000000000000000000;hp=f1ffbaca21ca15aa8d16ef145cb05d36f29b1ef9;hb=4ae3b26a6ac33df700f9cd2fcc59abf85ce156a1;hpb=905f479e4bb64bf3252e288bd5eff6d0325c1261 diff --git a/rockets/airframes/yikstik/index.html b/rockets/airframes/yikstik/index.html deleted file mode 100644 index f1ffbac..0000000 --- a/rockets/airframes/yikstik/index.html +++ /dev/null @@ -1,835 +0,0 @@ -
Copyright © 2008 Bdale Garbee
- This document is released under the terms of the - - Creative Commons ShareAlike 3.0 - - license. -
Revision History | |
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Revision 1.2 | 12 January 2009 |
- Document firmware bug in miniRRC2 and possible impact on flight. - | |
Revision 1.1 | 5 December 2008 |
- Remove embedded images in favor of references to gallery.gag.com - | |
Revision 1.0 | 28 October 2008 |
- Recording results of first, and only, flight attempt. - | |
Revision 0.5 | 27 September 2008 |
- Building checklists - | |
Revision 0.4 | 17 September 2008 |
- Documenting the build process as it happens - | |
Revision 0.3 | 29 March 2008 |
- Incorporate ideas from James Russell during initial L3CC review - | |
Revision 0.2 | 27 March 2008 |
Cleaned up for initial review | |
Revision 0.1 | 16 March 2008 |
Initial content |
Table of Contents
- 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! -
Table of Contents
- 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. -
- 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. -
- 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. -
- 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. -
- 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. -
- 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. -
Table of Contents
- 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. -
- 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. -
- 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. -
- 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. -
- 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. -
- 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. -
- 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. -
- 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. -
- 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. -
- I hope to fly - - my own altimeter design - - 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. -
- This design has been thoroughly analyzed using - - RockSim - - 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. -
- These simulations will be refined as the build proceeds and as-built - stability verified before flight. -
- 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. -
- 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". -
- 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. -
- I intend to sew the parachutes from scratch using a design documented by - - Team Vatsaas - - 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). -
- The deployment bag will probably be purchased from Giant Leap. The - recovery harness will probably use tubular kevlar, also from Giant Leap. -
- 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. -
Table of Contents
- I have collected all of my - - build photos - - in one place, they may show better than I can explain how various - aspects of YikStik went together. -
- 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. -
- 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 - - John Coker. - -
- 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! -
- 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. -
- 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. -
- 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. -
- 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. -
- 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. -
- 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. -
- 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. -
- 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. -
- 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. -
- 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. -
- 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! -
- 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. -
- 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. -
- 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. -
- 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. -
- 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. -
- 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. -
- 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. -
- 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. -
- 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. -
- 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. -
- 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! -
- 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. -
- 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. -
- 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. -
- The main parachute will be sewn from 1.9 oz rip-stop nylon purchased - from the - - Mill Outlet Fabric Shop - - in Colorado Springs. Using the spreadsheet from - - Team Vatsaas - - 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. -
- 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. -
- 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. -
Table of Contents
- This rocket uses dual deployment. -
- 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. -
- 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. -
- The 8 foot main chute is home-made from 1.9 oz rip-stop nylon using - the design documented by - - Team Vatsaas. - - It is attached to the remainder of the rocket using another Giant Leap - pre-sewn 1/4 inch tubular kevlar assembly. -
- 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. -
- 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. -
- 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. -
- The - - Info Central Black Powder Sizing - - 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. -
- 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. -
- 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. -
- 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. -
- 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. -
- 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. -
- 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. -
- 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. -
- 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. -
- add description of anticipated flight profile here, including launch - weight, estimated drag coefficient, velocity leaving the rail, max - expected velocity, altitude, and acceleration -
- 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. -
- 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. -
- Reward if returned posters were placed in the area during the week - following the launch but have elicited no useful reponses yet. -
- 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. -
- 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. -
- 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. -
- 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. -
- 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! -
- [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! -