February 26, 1972 (2PM CST)
Earlier this morning, we conducted the first flight of A-Rocket, my very first amateur rocket. A simple ballistic design, A-rocket consisted of a metal tube, metal fins, wooden nosecone, and powered by one of my first successful all-metal rocket motors. We conservatively used a half load of propellant, as we were unsure of just how high this rocket would fly with a full load of propellant. Powered by my A-Engine, with 60/40 potassium nitrate/sucrose propellant, static testing demonstrated this motor delivered a pretty good punch, in comparison to the model rocket "engines" that boosted my model rockets into the air. As it turned out, we were indeed pretty conservative, as Flight A-1 went no higher than an estimated 50 feet above the launch pad. It was nevertheless a satisfying flight, as both the rocket and motor worked...!
Now it was time to conduct launch number two of the A-rocket. This time with a full load of 50 grams of propellant. Double the height wouldn't be a bad achievement. Maybe it'll go a bit higher.
We installed the rocket into the modified wooden launcher we'd used for the first flight. The launcher consisted of three parallel pairs of 2x4's, to serve as guides for the three fins. The spacing between each pair was just enough for the fins to neatly slide along. Unfortunately, for that first flight, the spacing must have been just a bit too tight, or perhaps it was the extreme morning cold that shrunk the wooden parts just enough to be troublesome, as we were only able to slide the rocket about a third way down into the launcher assembly before it became an overly snug fit. For flight number two, we were able to rectify the problem, and the slightly less frigid cold weather this afternoon probably helped, as well.
The igniter was the same as used for our static tests. A small stick of cast sugar propellant with a length of nichrome wire embedded at one end. This was inserted into the nozzle a short distance. Using a motorcycle wet-cell battery, I'd approached the rocket and made contact with the battery leads to the nichrome wire. The propellant stick began to burn, giving us a delay of about 5 seconds before the flame reached the propellant grain in the motor. This gave me just enough time to dash away, grab my Imperial Mark XII camera, and snap a photo as soon as the rocket commenced its skyward journey.
Liftoff...! Our A-rocket was full of vigour this time, rapidly soaring skyward, climbing higher and higher, well beyond the 100 foot mark doubling the altitude of the first flight, and still climbing... 200... 400, peaking at perhaps 500 feet, an estimate based on our experience with launching plenty of model rockets the previous summer. The bright winter sun glinted off the shiny metal rocket as it arced over at apogee. Slowly picking up speed, the rocket began its ballistic descent, picking up ever-greater speed as it arced toward the ground several hundred feet downrange. With a loud clang, our A-rocket ended its amazing flight as it struck branches of a distant poplar tree.
It took us well over an hour of searching, but eventually, we found the rocket, buried into the snow cover, its entry marked by a distinctive hole in the snow accentuated by three radial gouges courtesy of the fins.
LEFT: Author with A-rocket prior to 1st flight; MIDDLE: Liftoff of 2nd flight; RIGHT: Landing site
A-rocket is largely in its original form. Some restoration was in order. The nosecone, which was badly cracked after its fourth and last flight, was replaced with a near-replica, identical with the exception of the material. The original nosecone was birch, the replacement is oak hardwood. Other than the nosecone, the only new part of the rocket is the thrust bolt, against which the A-engine delivers its propulsive force. The three fins had been carefully removed from the rocket, taking care not to fracture the rusted screws holding the fins to the rocket body. It was necessary to straighten the fins, slightly bent as they were.
The original A-engine that powered A-rocket on its four flights was misplaced at some point in time and, as such, it was necessary to make a replica. Using the original drawing as a guide, a casing was cut from a length of 1/2 inch metal conduit (EMT). A new nozzle and bulkhead were fabricated from cold-rolled steel, using the same method as was employed in making the original. We did not have a metal lathe back then, so we improvised, using a drill press to full advantage.
Propellant for A-engine was the early formula straight out of Brinley's Rocket Handbook for Amateurs, a melted mixture of 60% potassium nitrate and 40% powdered sugar. I'd fabricated a contemporary set of four casting moulds for the propellant to reproduce four hollow-cylindrical grain segments with a 1/4 inch core, as per the original. It took a couple of attempts to cast four satisfactory grain segments using the old oil-bath method of melting the propellant. I'd forgotten how challenging it is to successfully cast sucrose-based propellant, with its high melting point, tendency to caramelize, and rapid cooling and hardening as the slurry is scooped into its mould. The modern, easy-to-cast versions of sugar propellant, such as KNSB and KNDX, are a real godsend...!
Of course, it was necessary to static-fire the replica motor before being bestowed the honour of lofting our precious A-rocket on its fifth-ever flight. We'd conducted the static firing in April of 2021, nearly a year in advance of the planned 50th anniversary flight. We chose to connect the motor to our present-day instrumentation for measuring chamber pressure. When we static fired the original A-engine, we did not have this capability. We were certainly curious to find out what chamber pressure this jaunty little motor developed. The answer... a peak pressure of 928 psi (6.4 MPa). Nice.
I faintly recall it was a frigid winter day when we flew A-rocket on its maiden and follow-up 2nd flight. Today, the thermometer is likewise well below zero, with a brutal wind. Fortunately, the sun is shining brightly, offering just a little warmth. I'd kept my videocamera warm inside my coat pocket. Now it was time to begin recording, and to announce the countdown. My brother manned the launch button, and had the additional duty of setting the landing locator to record the landing site location.
I gave the countdown. Five...four...three...two...one..ignition! A puff of smoke appeared at the base of the launcher, followed immediately by A-rocket leaping skyward, it's smoke trail clearly accentuated by the bright sun and blue sky. Launched at an 80 degree angle, A-rocket gracefully arced toward apogee climbing higher and higher just like it did on its flight exactly 50 years ago. I noticed one thing about the contemporary flight that I don't recall on its prior flight. The rocket was spinning, made apparent by the sun reflecting off its oversized fins. Come to think of it, on A-rocket's prior flight, it was a cloudy day, that may be the reason why I had not noticed this. Either that, or the exhilaration of witnessing its remarkable flight took precedent in my mind and memory. The rocket arced over at apogee, which we once again estimated to be approximately 500 feet...this altitude coincides with the simulation we'd run in preparation for the flight. Picking up speed on its ballistic descent, A-rocket soon ended its fifth (and final?) flight silently, burying itself in the deep snow cover several hundred feet downrange.
We briefly searched for A-rocket, although we knew it would be challenging to find the "witness mark" of its entry into the metre deep snow. At this point in time, we'd been out in the elements for over an hour, having conducted some unrelated rocket motor static firings prior to the flight of A-rocket. We were starting to feel the onset of frostbite, so we abandoned the search, marked the GPS location of the launch site, and recorded the orientation of the landing locator on film. Once the snow melts, in a few months from now, we'll return and recover our much-valued A-rocket.
LEFT: Author with A-rocket prior to 2022 flight; RIGHT: Liftoff!
2022 LaunchA-rocket exiting the launcher
Climbing toward apogee...
Arcing over at apogee, estimated at 500 feet (150m.)
Launch video (19 Mbyte) MP4 format
Restored A-rocketA-rocket with its brand-new nosecone
A-rocket with straightened fins and replica A-engine
A-rocket and author , February, 2022
A-enginePotassium nitrate/sucrose being weighed
Heating using an oil-bath
Cast into moulds
Four grain segments with motor casing
Ready for its static test firing
Static test chamber pressure graph
Static firing video (9.6 Mb) MP4 format