A LOT of this project was engineered on the fly and by no means reflects the best way to approach the tasks described. It's just how I did it and you're welcome to make changes any way that suit your engineering skills.
I offer this in hope that this 'instructable' will inspire others to build and fly similar projects.
Step 1: Preamble
This ISN'T a scale project; the "Mercury Booster" is a little thicker than the real thing. The "Mercury" capsule is built from the GI Joe unit, is under scale as well.
The big challenge of this project is to perfect a system that allows the capsule to free-fall to a safe altitude before deploying its parachutes. Technically this is no more than a dual deployment flight, but the added complication of extracting the tower so the capsule can free-fall is anything but simple.
At apogee the capsule (with tower) will decouple from the booster.
The capsule has a deployment bag attached to the heat shield which will pull out the pilot chute for the booster.
The decoupling activates an ejection charge timer inside the tower, allowing for the capsule and tower to drift away from the booster which will be unfurling its main chute.
Once the tower charge has fired and its chute has inflated, the weight of the capsule causes it to fall free off the tower base.
The capsule free-falls to about 1500' before deploying a pilot and main chute combination.
With all going to plan, video of the flight is captured from the booster, looking up and down, the Tower, looking down and the capsule, both interior and an additional view down.
Step 2: Basic Design Concepts
Each section has its own avionics, video capture and recovery system.
The booster section is divided into two parts to make it easier to transport and store in the off season. It is held together by turnbuckles on nylon straps hat clip onto large eye bolts.
The capsule is fitted with a PVC end cap that couples to a 1/2" PVC pipe that extends down the center of the main recovery chamber. This reduces the need for a large ejection charge to blow the capsule off and push out the booster's parachute.
Four centering blocks keep the capsule aligned with the body tube.
The capsule and booster have flight computers that are setup to trigger the primary decoupling at apogee. The capsule's flight computer then waits for a designated period of time (or altitude drop) before it deploys the capsule's recovery system.
Step 3: The Upper Airframe
This lathe is made of mounted 2x4s with 1 1/8" holes and a 6 foot length of 1" gas pipe with 9.25" plywood disks. To keep the disks in place I'll often just add tape to give them a nice friction fit.
I use a BBQ rotisserie motor slowly rotate the tube while I apply an even coat of the resin.. Later to aid in the sanding, I switch the rotisserie motor out with the upper head of a drill press, this gives me nice speed and torque.
Note: When sanding, I use furniture clamps to hold the lathe posts in place on the table.
Step 4: The Fin Can
You can put any motor configuration into your fin can, I decided to go with a central 75mm with 4 38mm in case I want to do a cluster launch.
The fin can air frame is 26" long with a 6" coupling shoulder.
Step 5: Tower
The important aspect about the tower is it needs to sit firmly on top of the capsule but separate once the weight of the capsule is applied.
Step 6: Capsule (continued)
After as many flights the capsule has endured many a harsh landing but as a testimony to the original, it help up.
The one change I made that isn't show (well) here was that I built a fiberglass extension to the capsule nose. I used a 3.5" phenolic tube and built an end cap out of model aircraft plywood.
The Annual GI Joe convention requested Mercury Joe to make an appearance, so I shipped him off and included this little demonstration video to help them better understand some of the technical aspects of the modified capsule.
Step 7: Paint and Decals
The first time I build this project I painted the checker pattern at the top of the Redstone, the second time I built the pattern in Adobe Illustrator then sent it to a decal manufacturer to make. I'm not convinced that made the job easier as putting on such a large decal has its challenges as well. It did help to put the tube on the tube lathe but even with that the alignment wasn't perfect.
BUT no one really notices that sort of thing when the bird is on the pad or in the air.
I chose to paint the capsule blue instead of black, mostly because it made it more "Navy" like and Alan Shepard was an Annapolis Grad (and I'm from Annapolis) Plus the capsule isn't scale so I felt I could take the liberty.
All the lettering and flag decal came from a local arts and craft store and the black striping is automotive pin stripe.
Because this is such a popular rocket to model, it's very easy to find visual references via Google.
Step 8: Flying and Recovery
It can take a couple hours to build the ejection charges, test the avionics batteries, make sure all the chutes are packed correctly, the cameras charged and have plenty of memory available, the motor built and secured and of course the Astronaut well rested and ready to fly.
I highly recommend a check list, it can reduce the risk of failure considerably (but not entirely).
This rocket has flown up to 1 mile high on an M, but my preferred altitude is 2500' using an L. This allows the spectators a good clear view of all the processes working.
Note this video is playing at 1/2 normal speed.
Flying to 2500' also makes it extremely difficult to lose sight of the three sections and because we fly with AeroPAC out at the Black Rock desert, it's REALLY hard to lose anything, even when the smallest component manages to break free (like the cap to the capsule).
That said, when it works, all that effort is it is worth the celebration and the accolades people often shower upon you! :)
Step 9: Part Sources, Pages and Suggestions
The Body Tube and bulkeads: was harder to find, and is key to making this particular rocket. Rocket Dynamic Systems (RDS) sells a 9.25" body tube that is the diameter of the base of the capsule.
Now if you wanted a more scale Redstone booster, you could use a 9" body tube as with the real Mercury Redstone the capsule extended out slightly beyond the booster's diameter. (see picture below)
The Fin Material: The fins are made of Aerospace Composite material from Giant Leap Rocketry.
Avionics : You will no doubt want to use a flight computer you're familiar with. In this project I use gear from;
Adept - Altimeter in the capsule
PerfectFlite - Timer in the tower
GWiz - Altimeter in the booster
Cameras : Over the course of this project I've used SO many different cameras, but right now the combination I like is
Tower Camera - BoosterVision Gearcam
Cockpit Camera - Grayson Hobby's Aerial Cam Note: you can also find similar ones on eBay called 'Gum Stick cameras"
Booster Camera - Aiptek 60 fps HD camera
I also use a couple Keychain cameras for additional views, like looking up the booster.
JOIN A CLUB
If you're going to build and fly one of these (and live in the USA) I highly recommend you join either TRA or NAR then find a local club. This sort of project greatly benefits from the experience you can get flying with a high power rocketry club and I attribute the successes I've had because of my involvement with AeroPAC .
Mercury Joe website
Mercury Joe Youtube channel
Mercury Joe on Facebook