I'm surfing the web, looking for Scavenger's old AirWarrior posts. Wow! Cool tales about the Atlas/Mercury programs... I'm having rocket synchronicity. Rest in peace Scav, Salute!
One problem becomes apparent... RATS does not encourage spectators. The options are basically Fire or Forget it. We decide to each buy a rocket, become Tripoli members, and watch the fun. Darren surfs the net a bit more, and figures that the optimal rocket to get is the Sudden Rush from Public Missiles Limited. This rocket is nifty: five and a half feet long, 3 inches diameter, altimeter based ejection of drogue chute at apogee and main chute at low altitude. It can fly on anything from a small H motor to a big J-800. It has an interchangable motor system (29mm through 54mm motors.)
I call up PML and order the rocket. The altimeter is on back-order, so I tell them to ship the whole package when the altimeter arrives. Darren, far wiser in the ways of the world, orders his, and tells PML to ship what they have and to send the altimeter later.
Only a week to launch, and still no rocket. I call PML and tell them to ship whatever they have. Darren is now calling them daily, asking for the status on his altimeter (the new P5 model.)
Ok, I have Tripoli Level 1 certification now (I can buy and fly H and I class motors.) I start preparing for the RATS spring 1999 launch. My goals for this launch are:
Darren and I start thinking about the electronics.
First order of business is get a BATF Low Explosives User Permit (LEUP). This seems to be required for large rocket engines (54mm diameter and above.) I download the form, and mail it in with my $100.
Altitude measurement is proving to be more of a problem than I expected. There are a number of ways to go: barometeric (unreliable at high-alitude,) integrated acceleration (hard to verify,) ground-based telemetry (more equipment, may need a radio license,) or GPS-based. DMR says the GPS is the obvious way to go.
A web search turns up the G-12 by Ashtech. This looks good: small form-factor, rated for 20Gs, 10 readings/second, RS-232, and ready for differential. A call reveals the price (ugly, but not a show-stopper,) and the bad news: GPS receivers don't work at over Mach 2 or above 60,000 feet (regulatory, not technical.) I make a few calls to the Department of State, Commerce, etc, but no one seems to know to whom I need to talk. A post to sci.geo.satellite.nav suggests The NAVSTAR GPS Joint Program Office. The website has more acronyms than you can shake a stick at. Ashtech (these guys have a clue) suggest I send them my "project details," saying they have some experience in this area. I start writing my project details (i.e. this web page.)
If I have a LEUP, I'll be able to fly big Ks, otherwise it will have to be 38mm small J motors. I surf the web for possible rocket kits: Public Missiles still seem to have the best designs in this power range. I plan on the following rockets:
This should be a good mix. The Quantum Leap and Nimbus can both achieve 10K or so. The Nimbus should be able to break Mach 1. The Eclipse is big enough to take our custom electronics as a payload for initial tests. Another hi-alt option is the PML Cirrus - 1.5" diameter, max motor is a small J. While this will fly on a 38mm motor, it seems too much work: the quality of the body finish will have a big effect on the Cd. Quality requires time, and I'm always short of time. The Thunder N Lightning is another possibility for the two-stage rocket. I'll call PML and ask for details.
It looks like Black Sky Research ALTACC accelerometer/barometric pressure sensor is the best bet for controlling the rockets while we test our own electronics. Hmmm, I can only find an an email address for these guys. Scott Bartel of BSR replies to my mail within a day. Looks good, price is about $180. I'll need two of these.
There are a several options for radio beacons/locators. A number of firms make lightweight transmitters for falconry. Rescue equipment is slightly heavier, but provides better range. I send mail off to the companies asking for more information.
The BATF return my appication for a LEUP: I didn't fill in one box (marked "voluntary".) I call the BATF and the nice lady tells me that they will be running a background check... it's voluntary to fill in my social security number, but if I actually want a LEUP, I should fill it in.
I download VCP, a shareware program for computing the CP/CG of rockets. I test it on my Sudden Rush, and its estimate of the CP agrees with the PML's published number.
I'm now a member (#6820) of Tripoli. I assure Darren (#6822,) that although I am the senior rocketeer, I will still listen to his ideas with interest. Darren looks annoyed.
Level 3 certification seems a little tricky: specifications, analysis of failure modes, checklists, design to be approved by multiple experts, etc. I reckon it makes sense to start work on the preliminary design now, and be ready to submit it immediately after my level 2 ceritfication flight. I expect the Spring 99 flights to reveal a number of failure modes I have not fully considered.
My company sends me off to London for two weeks. I work on plans for my level 3 rocket while there.
Upon my return, I find I have a phone message from my local BATF agent. I call back and am subjected to an hour long phone "interview." First he laughs at me saying LEUP (I pronounce it like LRRP, as in long range recon patrol.) He tells me that the cool crowd says "Low Ex." Then we talk about the inapplicable answers that I have given in response to the inapplicable questions on the LEUP form. A debate into the exact meaning of "perjury" follows. Next we chat about the New York State Labor Department rules, the National Fire Prevention Association code, and the Department of Transportation rules: most of this revolves around whether I have so far only violated state or federal laws. A discussion of the interpretation of laws concerning maximum hobbyist propellant weights ensues, touching on explosive shipping containers, the "location" of interstate motor purchases, and other topics I know little about. He asks me about my "day box." Huh? He explains that it is a metal box with a non-sparking interior for holding my motors (aka a portable magazine.) Official day boxes are class 3 magazines, but he mentions the possibility of a BATF waiver for a portable class 4 magazine. Things are looking up! He asks me about my plan for disposal of unused motors... Hmm, I hadn't considered this. Finally, he tells me to get a magazine (even suggesting I could build one from an Army ammo container,) write up a disposal plan, and show compliance with state laws, and make an appointment for a face-to-face interview. I pick Jan 4. In spite of the grief, I got the impression that the agent was a good guy, actually trying to help me comply with the BATF requirements. One of his concerns was that, while I only what to fly big rockets, the licence lets me buy all kinds of cool toys.
I surf the web for information on explosives magazines. Some of requirements seem Kafkaesque: it should be painted bright red with clearly visible sign "Warning: Explosives" nearby (so that firefighters, etc, are aware of the hazard.) The sign should also be invisible, so that the criminal element is not attracted to it. The states, of course, all have different requirements for magazines: I guess you do a dog-and-pony show at each state border. Except that some states have rules about when you can open magazines... and transfer to a non-compliant (i.e. the other state's requirement) magazine ain't one of them. I'm glad I only want a little red box for use at a launch range.
Monday, Dec 28, I call PML and order an Eclipse, a Quantum Leap, a Nimbus, and an Ultimate Endeavour. The Ultimate Endeavour is a 6" body rocket... I rationalize that it'll help me figure out heavy rocket construction techniques.
Tuesday, Dec 29. I finish up my BATF letter: it includes a plan for disposal of unused motors and a detail of the Orbital Dynamic's day-box. I hope the inspector will approve the box design... a type 3 magazine is nearly twice the price of the OD box. Note to self: hide all credit card receipts from wife.
I discuss day-boxes with my BATF agent. He isn't too keen on the OD box: the metal lock hasps on the box inside make him nervous. I think I'll just get the Armag box and be done with it.
I order a custom box from Armag (18x12x12 internal dimensions, 80 pounds.) It's overkill, but I really don't have time to waste on this. PML still hasn't shipped my order: apologies about tubes not in stock, etc. I order some toys from Zeppelin: two quarts epoxy, some two-inch tube, an Acme fin can and conformal lugs, Stine's Rocketry Handbook, some nomex pads, etc. I also order two 54mm motor retainers from Countdown Hobbies. Most of these things are for evaluation purposes.
My BATF agent calls back: he has just seen a day-box that he thinks might suit my needs. He gives me the company name and url. Can he really be from the government... and here to help me?
UPS manages to totally screw up delivery of my rocket parts: I get the motor retainers (after a great deal of hassle,) but the shipment from Zeppelin is somewhere in Illinois.
I post a plea on rec.models.rockets for Barrowman's paper on rocket stability. Gary Crowell (the author of VCP) answers, and offers to send me a copy of the original thesis, plus a bunch of other notes.
Building the rockets seems more like industrial assembly than hand-crafting. Each evening, I prep a few parts from each rocket, apply epoxy, and go to sleep. The Ultimate Endeavour starts taking shape first, followed by the Quantum Leap. The Nimbus is getting stretched with the 36" booster tube, and I replace its fins with the Acme fin can. The Eclipse brings up the rear (it was shipped without a bulkhead ring, so it's last in line on the epoxy runs.)
The nice man from the BATF keeps calling to ask about my day-box. I call Armag, my box should ship by the 22nd or so. I'd like to just cancel and get the light, cheap box, but I did custom order this one (and Armag seems like a good company,) so I wait for shipment.
I break down and buy a Dremel. This tool is just too cool! I only really need two attachments: the cutting disk and the sanding cylinder. It strips unwanted epoxy beads in seconds, cuts fiberglass flashing trivially, and makes fin edge sharpening easy. Even Maya thinks this is a good thing to own!
My Armag box arrives... Well, it actually arrived in New York several days ago. UPS decided it was kind of heavy, so there was no point in delivering it until I started complaining.
I set up the interview with my local ATF agent. He's a pretty cool guy: in the reserves, speaks several languages, knows his World War II aviation history. He tells me that he likes to look at applicants' bookselves... they're a good personality check. He approves of my military section, Maya's language and history books. He is polite enough not to mention my copy of The Anarchist Cookbook. We go over the regulations and requirements, and then he tells me he's recommending approval. Woohoo!
I'm thinking about fiberglassing options for my rockets: I order a bunch of stuff from Fibreglast: 3cc syringes, a few yards of 3oz cloth, 1/32" milled glass fibers, a dust mask, etc.
Bad news - the RATS spring launch is cancelled! I start websearching for alternative sites for level 2 certification this summer.
Real life (i.e. my job) seems to be eating up all my time. I finally take a break and go to see October Sky with my wife. She actually likes it! The next day, she asks about attending a launch. Cool, this is much better than being subjected to Freudian theories concerning my reasons for filling the living room up with rockets!
I buy some toys from Parallax: a Basic stamp experimenter's board and a Basic Stamp II with a mounting board. The experimenter's board is very cool: sockets for Stamps, toggle and pushbutton switches, 4 LEDS, a 7-segment display, a piezo speaker, many high power outputs, a potentiometer, RS232, and leads to wire it all up. I hook it up to my PC's parallel port using 25 pin connector and a few paper clips (these make good pins in pinch.) I try to program it to flash the four LEDs in sequence... amazingly, I get it running within three hours!
I get all the stuff from Fibreglast. Maya (my wife) is going out of town for a conference so I reckon this is a good time for heavy-duty fiberglassing. My reasoning is as follows:
Litton sells a really neat gyroscope. I call them up and ask about price and availability. $25000!! I'll look for alternatives.
I order more stuff: a P5 barometric altimeter from PML (and a 3" coupler tube for my friend Scott, plus the missing 4" bulkhead,) an AltAcc altimeter from BlackSky Research, and a Futaba gyro/servo combo from Tower Hobbies. I'm learning... everything is shipped to my workplace, and our mailroom is totally clueful when it comes to dealing with UPS insects.
Now I'm buying epoxy by the gallon. Manhattan has one marine supply store... epoxy, slow hardener, measuring cups, and microballons, dual-cartridge respirators. I'm in heaven.
I decide that CAN is the ideal bus for a rocket: nice protocol, many chips talk it. I'm kicking around ideas for level 3 and above projects... some of these involve 10 or 20 devices talking to each other.
My gyro from Tower Hobbies shows up. A web search shows that R/C stuff communicates using pulse width modulation. I should be able to get the Stamp board talking to it without too much trouble.
I'm surfing the web and find an engine that looks ideal for a CATS prize booster: the Viper V from ISP. It's a 6" diameter, 7 foot long motor, with a total impuse in the Q range. They refuse to sell me one.
I start spray painting the rockets. Spray paint sucks, I should really get an airbrush.
July 4th weekend: I finish painting the rockets, start drilling vent holes, test the Altacc, and write some notes for the launch crew.
Tuesday, July 6th. The Ultimate Endeavour now has an electronics bay designed to hold the AltAcc.
Wednesday, July 6th.
Final shopping supplies: masking tape, carpenter's chalk, Spectra, rattail file, batteries, weights, 5min epoxy, rubber bands, explosives logbook, long bolts. Final tasks: chute packing, weighing, simulations, return-to-sender tags.
The rocket suddenly crystalizes in my mind: 4" diameter, 7' 5" length, glassed, upper airframe with coupler tube from booster to nose cone, generous electronics bay, a single 3/4" tubular nylon harness running from fore to aft. The booster harness will attach to the motor casing's threading fore closure, secured against twisting by lock nuts and chute swivels. Heat transfer to the lower recovery shock cord (5mm climbing rope, 25% stength reduction at 200 degrees) will be attenuated with masking tape insulation on the eyebolts, and an 8" steel trace that will be air-cooled during the decent under drogue. This is basically an upscaled level 2 rocket: friction fit nosecone and booster, zipperless design, and redundant recovery electronics. Its sweet spot is a medium L motor, but it should be flyable on a baby M and a full I. The fins are oversized and swept (PML 'D' form) to reduce the risk of fin shadowing during Mach speed transition (an L1120 should hit this.)
I order the parts I need from PML.
RATS: I redo a level 2 cert flight on the Ultimate Endeavour: really nice boost and a clean recovery. Woohoo! On a sad note, Scott lawn darts his Ariel.