The Mock Terrier Sustainer is my scratch-built L1 project which has been a mental exercise for over two years and was physically assembled over the course of about 6 weeks of construction and materials acquisition. It employs 2-stage recovery, tumble from apogee and then main deployment at 250 feet, a measurement that is an irrevocable characteristic of the Apogee ALTS-2 altimeter.

Mark Willett & Mock Terrier Sustainer.

The project weighs 1.4kg with an Aerotech H97J motor. The fin can will accommodate electronics for (future) air starts, and is pre-wired with binding posts aft at the motor retention location on the rear centering ring for motor igniter wiring. Motor retention is a 3/8" strap of 22 gauge stainless steel which hooks over the aft motor closure and is secured to a post screw on the aft centering ring.

The airframe is fiberglass-reinforced 2.6" diameter cardboard tube with a Dupli-Color paint job and clear coat, built with three 3/16" plywood fiberglass-reinforced fins, using through-the-wall construction to a 29mm motor tube. Just looking at those fins you can tell the bird is so stable, it's stupid!

Mock Sustainer's fin can.

The electronics bay is fitted with binding posts fore and aft for the recovery charge circuits, and an external rotary switch for arming. I am really pleased with my arrangement of the apparatus. Pre-launch assembly and prep is fumble-free and smooth-flowing as related to the electronic recovery system. The fore and aft payload bay airframe tubes are secured to the electronics bay with four epoxied-in-place blind nuts and flat head Allen-drive screws (which are a cool anodized metallic blue - RC car parts).

I learned a lot during the construction, and particularly the testing of the recovery system. Not only was this my first high power motor, but it was my first use of electronics for recovery. Some things that I thankfully learned before flying the bird. For instance, that black powder residue is electrically conductive.

Some other interesting subjects of study were along the line of black powder charges and airframe pressurization requirements and calculations. I had purchased a low current electric match kit from a fireworks supply company and "hand-dipped" my own e-matches, which function flawlessly with an impressive amount of combusting material to assure deployment.

Inside the Mock Terrier's electronics bay.

I showed up to the launch with my project in hand. It was my understanding that two NAR members of certain qualifications were required to sign off on the paperwork. I was assured that Jim Jarvis was available and willing so I hit on Alex Mericas as a second, who upon the request indicated that he is L3, so he'd handle it all. Mr. Jarvis indicated that if that was the case, he was going to RSO my launch. Now I knew that I was really going to be scrutinized and receive the greatest possible amount of grief that this situation could possibly generate by my friends in the Austin Area Rocketry Group!

Alex commenced to scrutinize my knowledge of the project, the processes of construction employed, the anticipated flight characteristics, and a liturgy of investigation and questioning that was three times the written checklist provided with the certification form (which was administered also, by the way). In response to who it was I consulted relating to the project; Stu Barrett and Rick Van Voorhis had physically inspected my project during different phases of construction, and the entire club, including Alex himself, had participated in review of my questions and observations during construction on the Yahoo AARG email list. I had acknowledged everyone's advice that was offered. After final assembly, I was allowed to proceed to check-in.

The Terrier Sustainer's business end.

Now Jim is inspecting my rocket as RSO and inquiring as to my ejection charges and pondering whether it is adequate relative to my airframe dimensions. Rick attacks my giant fin construction, at which point Stu chimes in (he hates fins, too). When I respond to questioning relating to recovery, no one is impressed with the 250 foot altitude setting for deployment of the main (combined with tumble recovery and no drogue chute), and Jim cites the likely rate of descent and the time frame thereof for the full inflation of the main parachute. I state that it will not (can not) be changed and that's the way it is, over a din of laughter in apparent anticipation of this event, which seemed to result in amusement among the bystanders and those antagonizing me.

At the rail, I cut a slit into the red plastic cap that slips over the nozzle of the motor assembly (as supplied by the manufacturer) in order to secure my igniter in the motor, but my modification to the plastic cap would not secure the igniter. Since I had retained the motor with my stainless steel retention strap, the holes in the aft closure were vacant, so I ran my igniter leads through one of the holes. This was satisfactory and so now I was ready for launch.

Mark had great success with this e-match kit.

I really enjoyed the dark smoke of the Blackjack propellant as the rocket left the rail at a somewhat leisurely pace (calculated airspeed at 6' elevation is 34mph). As the rocket accelerated the fins seemed to shrink relative to the scale speed of the project (estimated 235 mph maximum velocity). I was pleased with the visual effect. She cocked slightly into the Westerly wind and flew over our heads to an arcing apogee (predicted to be 1,500').

It seemed like a couple of seconds after apogee when I became concerned, as it seemed that descent was well underway and no separation had yet occurred, but then it happened and a nice tumble ensued.... and it tumbled to the East, back over our heads in the direction from which it traveled... and it tumbled. "Heads up" is called but everyone was aware of the 250 foot altitude for deployment of the main parachute so anticipation was high. Perhaps it was 150 yards to our East, at about the required moment, when the main deployed and the 36" Giant Leap Rocketry TAC-2 parachute fully inflated in purple and red colors in an impressive close-up observation of the recovery event, and quite frankly a bit of a nail-biter.

Success! All is well but for a tiny 3/16" zipper of the forward payload body tube. Recorded altitude was 1,471'. It is difficult for me to imagine that anyone that has ever qualified L1 could have had as much fun and satisfaction in doing it, than I did on this day.

Congratulations, Mark. Welcome to high power. Now get out your wallet!

02-13-2007 08:50 PM  #1
crontab Certified Level Three   Joined: Aug 2006 Posts: 204	Congratulations, Mark! That initial rush after agonizing over the event is well worth the wait. Hope you enjoy the hobby for many more years.

04-06-2007 09:38 AM  #2
agrippo Certified Level Three   Joined: Aug 2006 Posts: 75	Congratulations Mark, Nice rocket and a great article, thanks for sharing. There's no wonder as to why you were able to cert. You had a great ground crew helping you. I don't believe you can do any better then Jim, Rick, Stu and Alex. Ya Done Good!!! Welcome to High Power. Now get out the checkbook... Andrew Grippo