Gemini Titan High-Power Rocket Model

One of the coolest and most collectable "original era" Estes Kits is the Gemini Titan. To have one in your collection is like owing the Holy Grail. However, since I favor flying rockets over collecting, I built a clone of the Estes kit to avoiding being labeled as a "nefarious spoiler of relics". The "clone" has dual 18mm motors and uses a 2.2-inch diameter capsule nosecone from Balsa Machining. It was finished in shiny Monocote trim instead of paint, and, like the Estes model had no fins. For flight stability it had a clear butyrate plastic slip-on ring that sported four clear fins. Unfortunately, it did not get flown for the next 5 years. As soon as my wife saw it, it became part of her 'Man in Space' shrine. Foiled again! "Flying is too risky for such a special rocket", she told me..

While my Titan was part of the shrine I contemplated building another to fly. Before I started I heard about a large plastic Gemini capsule. Why make a second small model when I could make a bigger and better one! I obtained an un-built mid 80s Revell 1/24 scale capsule kit. (They have been re-released again this decade, Revell Kit No.1835).

The plastic capsule was far more complex that I anticipated a nose cone should be. Its exterior came as an agglomeration of many parts that required me to simultaneously hold together when gluing. As a display model it was intended to disassemble by snapping open in sections to reveal the details of its interior, aft end and skirt sections. Even the doors were supposed to hinge open for the astronauts to ingress and egress.

But as a flying model all the internal details were wasted. I gave the astronauts and all the other detail pieces to my son to use with his GI Joes. Plenty of glue was used to convert the show model into a flying spacecraft. Plastic cements were used for gluing all the styrene parts of the capsule. All joints had heavy glue coating, full seam gluing.

Base diameter of the capsule skirt is five inches; this requires a 5-inch OD airframe tube for the rocket. Not as easy as it sounds. Most 5-inch tubes I found were 5-inch inside diameter, or 5 1/4-inch OD. While this may work it would not give the ideal appearance. I luckily found a 5-inch OD tube on ROL that was ideal for the project.

I cut a 6 inch piece of the tube and made it into a coupler by removing a lengthwise section and glassing the seam on the inside. This is a trick used by most people who make rockets out of found tubes. As follows: 1) Cut off a piece long enough to make a coupler. 2) Cut thru one side of the coupler tube, cutting end to end. Place the cut tube into the airframe section by spiraling one cut end inside the other. 3) Draw a line inside the coupler at the overlap. 4) Remove the coupler and carefully cut on the outside edge of line. 5) Put the coupler back inside the airframe with a piece of waxed paper or plastic wrap between the seam and the airframe. (dont let the coupler get glued to the airframe). 6) Seam the coupler on the inside by using a strip of fiberglass and epoxy.

The coupler was then epoxied to the capsule skirt and the seam reinforced with glass strips on the inside. A plywood bulkhead and eyebolt finished the structure of the nose. I placed the bulkhead far forward to permit a forward chute placement for better CG position without resorting to nose weight.

Designing the motor assembly and fins took me considerably longer than building the whole project. The flimsy slip on ring Estes used would not work on a High power model. Complicating matters, Titans have external bell shaped engine nozzles on the aft end to compete for space with the fins. Thru the wall fins were out of the question, they would not look right on a Titan! How to do it?

After much mulling around I decided to go with twin 38mm motors. Canting them slightly outwards will help negate the effects of asymmetric thrust or delayed pressurization. Since the airframe had no slots the fins had to be behind the rocket, in the same space as the engine bells.

I looked around for plastic Easter eggs or anything else that I could use as a form for the engine bells. I did not want to take time turning forms on the lathe if I could use a found object. My wife found Aquapod rocket shaped water bottles that won over the goose egg size Easter eggs I had collected. (The cool bottle also gave some ideas for future flying bottle projects).

The bottle bells were glued to the motor mount tubes and glassed with three layers of 6 oz glass. Centering rings inside the bell gave a place to add positive motor retention made from screen door clips. The motor was deliberately set above the bell so the bell would be protected from heat and hitting the ground during landing.

(Brad's note: "The motor mount reminds of... something! I just can't put my finger on what that might be....

Fins were decided to be flag shaped pieces of 1/8-inch Lexan. They would be keyed into a removable motor/ centering ring assembly. A bulk plate in the airframe hold two 1/4-20 lengths of threaded rod that run thru the centering rings and nuts on the aft end to secure it all.

This motor mount/ fin can arrangement offered several advantages: I could change the motor configuration latter to a pair of 29mm motors, or a single 38mm, or 54mm motor. Best of all, I could easily replace broken fins at the range by simply removing two nuts and slipping out the assembly.

To keep the parachute forward and therefore eliminate any need for adding nose weight I added a stuffer tube. It is a 24-inch long by about 2-1/4 roll core from a drafting plotter. The stuffer is mounted between two centering rings to fill the large void inside the airframe. It also gives a good place to mount the upper recovery harness eyebolt. The open chamber between the ends of motor tubes and the stuffer creates a labyrinth that will reduce any chance of ejection gasses burning the chute.

The entire bird was finished in heat applied Monocote to give it a real aluminum metallic look. Applying Monocote to a cardboard tube is no easy task. Once it is on there is no way for the air trapped under it to exit. Many pinholes are needed to vent the blisters and iron out wrinkles. It worked best by rolling the tube and ironing it on about inch at a time.

We flew it in Lilly Georgia on 2 H123s for a first flight. The motors came up to pressure unevenly but the rocket remained stable. At about 6 feet off the rail the motors hit full song and it looked great.

It landed in fairly hard on the fins without sustaining any damage!

I also brought the Estes clone to the launch. It also had a successful first flight that day on two B6-4s (see photo to right by Scott Russell.) Yeah!