1/24 Liberty Bell 7 Mercury Redstone MR8 - NARAM 40 (1998)
The model which was eventually flown and won the Team Division Sport Scale event at NARAM 40 at the AMA headquarters site in Muncie, Indiana was pretty much an "accident" in that I had intended to return to NARAM 40 after the crash of the 1/72 Saturn V at NARAM 39 the year before with an all new Saturn V in 1/72 scale.
The Saturn had crashed due to severe weathercocking and an overly long ejection delay. My intention was to develop radio-controlled method of deploying the recovery system so that I could have control of when to deply the recovery system in a sort of "abort" control to quickly deploy the parachute if needed. Upon returning from NARAM 40 I began researching various methods of "aborting" a scale competition flight in order to save the model. In the process, I stumbled across the Futaba Pilot Assist Link (PA-2) which utilizes optical sensors to "see" the horizon in for directions. It is intended for model airplanes with the goal of keeping the wings level and the plane neither climbing or diving when the unit is engaged. I saw the potential use for this in model rockets in keeping them flying straight up and set about quickly building a gimballed-enging test model utilizing reloadable compisite engines. Ultimately, I wanted to use low-thrust long-burn motors for more realistic flight.
The resulting model was built around Plastruct 3" o.d. ABS tubing in order to be durable. The engine gimbal used micro servos and the engine gimbaled at the nozzle end. Basically, the front end of the reloadable motor did all the moving while the nozzle essentially remained on the model centerline during gimbaling instead of swingling back and forth. The model was about 30 inches long with a servo-release for the recovery system. The model was equipped with very small "bolt on" ply fins just large enough to make the model neutrally stable. The model was so complex, I frankly had not real expectations for a successful first flight.
Click on images below to enlarge.
The Mercury capsule was a thin resin casting, done flat and then rolled to a finished cone.
The escape tower received a lot of attention in order to make it as accurate as possible. Having a flight ready version at the Houston Museum of Natural Science and History (no longer there) was invaluable.
The LES motor and its nozzles are resin castings. The tower is Plastruct rod and tubing.
The master mold was done entirely by hand. Each "corrugation" was a small plastic rod, shaved to half-round, and glued to the mold master.
The Instrument Section included detailing, all hand done as a negative in a mold, and then a very thin glass/resin casting made and wrapped around the Plastruct body. Doesn't look very good in this closeup, does it?
Detailing on the tail section and fins was done exactly like the detailing on the instrument section.
The moment of truth nears and Terry White (right) and I place the model on the pad.
Liftoff! Moments later, the model was in dire trouble (see detailed description in text above)
Flight day arrived at a nearby field and conditions were less than ideal. The wind was blowing and there was a smoky haze all around from forest fires in Mexico over 500 miles away. Terry White (my competition team mate) and I decided to go for it. The model went absolutely straight up with no weathercocking under thrust (I believe we were using a 32mm F13 motor with about a 4 second burn). The approx. 1.5 lb model never built up much speed and coast was short. A flick of a switch on the transmitter popped the recovery system at which point the parachute deployed and promptly proceded to zero in on some power lines several hundred yards away. The high winds rapidly suspended the model over a hundred feet in the air. As we walked toward the power lines, the parachute miraculously disentangled and the model floated to the ground.
Over the next few months a couple of more test flights occurred including one which broke the engine gimbal when using a high thrust motor (still safely recovered due to ability to deploy recovery system quickly). My confidence was sky-high in the system but NARAM 40 was rapidly approaching and there was certainly no time to build a Saturn V model to utilize the system. I had been working on a 1/24 scale Mercury capsule for a couple of years and the 3" tube of the test model was only very slightly " an "overscale" match to the capsule. Within a few weeks, the test model was converted to a Redstone booster and Terry and I were off to NARAM 40.
The model was in first place after static judging. I had intended to "jettison" the launch tower in flight using an A3-2t motor at the base of the tower and using RC to ignite it. However, I decided the "risk" of this "flight points" effect just wasn't worth it since just getting a safe flight would net a contest-winning flight. So, I removed all the electronics and motor required for this "effect" from the capsule.
At that time, it was sort of a "tradition" that the last flight of a NARAM was reserved for the highest statically scored scale model and the Mercury Redstone was it. It had a lot of attention and drew a fairly large crowd. After a long and tedious prep, the model was loaded onto the launch pad. The countdown commenced and at zero the F20 motor came to life and the model proceded to pitch over as it left the launch rod. Within a couple of seconds the model had traced a big "S" in the sky and was traveling near horzontal when the motor shut off. I immediately deployed the recovery system...which worked perfectly...and the Redstone booster descended onto a gravel parking lot and was briefly dragged across it while the capsule drifed down onto a grassy area. I don't think I got any flight points for that near-disasterous flight but it did give us a qualified flight which was all that was needed to win. The RC recovery had proven itself one year after the disasterous Saturn V flight in Arizona at NARAM 39 the year before but the fancy horizon-sensing engine-gimballing seemed to be a failure...or was it?
It didn't take long to figure out why the model behaved in flight as it did. By removing the "flight effects" gear from the capsule I had taken about two ounces of weight from the nose of the model resulting in a CG that was slightly aft of the calculated CP...not a good thing for anything that flies. What I have concluded is that horizon sensing "autopilot" struggled to keep the unstable model flying vertically with little success. Luckily, it DID keep the model going "up" just enough to keep it in the air and at a sufficient altitude for a safe recovery. These conclusions enboldened me to try an even more ambitious model for the following year...the 1/10 scale Vanguard that was intended to be flown at NARAM 41.
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Scale Projects-1/24 Mercury Redstone