In the years following the first successful operations of the Orbital Transport, a need was recognized for a general purpose spacecraft to handle various jobs within the solar system. The most successful design was the Cinderella class. Cheap, sturdy, and versatile, Cinderella's came to handle almost all 'tugboat' services in Earth orbit. Modified to one degree or another, versions could be found among the asteroids performing mineral assays, doing medium range survey duty within the system, and acting as platforms for scientific research impossible within a planetary gravity well or atmosphere. Although overshadowed by her more glamorous contemporaries, at one point almost thirty percent of all registered civilian spacecraft were some form of 'Cindi'. The model shown is a generic Cinderella, before being fitted for specialized tools, pods, and sensor arrays.
1 - BT-20, 13" (331mm)
Construction Steps (also see the hints and tips listed farther down)
1. Using a sharpened 3/4" (19mm) dowel, punch holes through the centers
of both styrofoam balls.
2. Push the rear ball onto one end of the BT-20 main tube.
3. Slip the cardboard templates over the other end of the main tube.
4. Insert the dowels into the templates to keep them lined up.
5. Carefully push the dowels slightly into the rear styrofoam ball.
6. Push the front ball onto the main tube until the dowels are inserted about an inch.
7. Adjust everything so that 1/4" (7mm) of tube is sticking out of the rear ball, and about 1/16" (2mm) is sticking out of the front ball.
8. Use hot glue to secure the balls on the main tube, and the dowels into the balls. Make sure everything is lined up.
9. You can use scissors to snip away the templates.
10. Glue a shock cord mount into the front of the main tube. I used a regular ol' Estes paper type.
11. Glue an engine block into the rear of the main tube so that an engine will stick out about 1/4" (7mm) from the rear tube.
12. Using the 3/4" (19mm) dowel from step 1, make 8 tubular indentations into the rear ball. Make them as straight and as evenly spaced as possible, parallel to the main body tube.
13. Hot glue the tube fins into the indentations.
14. Using a quick-setting glue, attach string between the dowels to simulate support cables.
15. glue a 1 1/2" (39mm) length of 1/8" (4mm) launch lug to the inside of one of the tube fins. Make sure it's straight.
16. Finish and paint as desired. Make sure you test your paint on scrap styrofoam first.
Construction Hints and Tips
Use this diagram to make a template that will help keep the dowels parallel when you insert them into the balls. Make at least two from light cardboard.
A simple jig can be made to easily line up the tube fins. Drill a scrap of wood (measure carefully) so that 3/4" (19mm) dowels are sticking up in the proper places for the fins and another, longer one in the exact center. Push the ball down into the jig, using the center hole as a guide, to indent the styrofoam for the tube fins. I didn't do this, but I might for the next one. Note that you'll have to do this before step 2 in the construction steps above, and then skip step 12.
Here's some ideas I had on how to customize the Cinderella:
- more tube fin 'pods'
- glue elastic shock cord material or more string around the fin tubes to simulate strap-on pods.
- small dowel or tube pods glued to the main tube between the balls, or attached to the dowels.
- different patterns for the strings
- BT-3 (?) tubes glued around the motor mount for small thruster rockets
- replace a tube fin or fins with 'solar panel arrays' (ie. fins)
- create a different nose cone, hang antennas all over it, or change the shape
- install a recovery setup like the sputnik, with a 90 degree bend within the front ball; no nosecone!
- glue conduits or exposed piping all over it
- make indentations in both front and rear balls (put tube fins on rear only)
- replace the tube fins with huge 'Flash Gordon' type fins (an earlier version had these)
The prototype Cinderella has flown three times, once each on an A8-3, B6-4, and a C6-3. The A8 was too small an engine, and the B6 was barely acceptable. This rocket *needs* the C, and even then it doesn't get up very high (estimated 150'). The boost on the first three test flights were less than perfect, each corkscrewing up. I'll add weight to the nose and keep testing, but it could very well be the rather sloppy job I did lining up the tube fins. Recovery was gentle using a 12" chute with a spill hole, but if the rocket gets much heavier (paint and/or customization), I'd switch to a 12" without the hole, and maybe even go to an 18" chute.
Credit for the Idea
I had bought styrofoam balls a long time ago for a Sputnik, but never got around to building it. TJ and Rachael (my kids) suggested a 'dumbell' shaped rocket, and we started playing with the idea. This is the latest version, and the first flyable one. There've been many mockups and sketches made since then, and although it'll never win an altitude contest, this rocket is simple to build and wildly customizable. Have fun with it!