Some decisions to alleviate weight
Happy new year y'all. I've been thinking a lot about this project and have decided on two major things: weight of the External Tank (ET) and the weight of the orbiter.
On the ET front, I've decided to move to a LOC/Precision Phenolic tube that is 11.41" - this is still roughly scale when compared to the 12" Sonotube I was going to use. The SRBs are exactly half of the diameter of the ET, so the LOC tube is actually more scale and will not be as thirsty for Epoxy as Sonotube reportedly is.
To state the obvious: this project is part rocket, part RC glider. And you have to deal with each with the technologies that assist them. The SRBs and ET are very straightforward to me and familiar. Yes, there will be challenges there, like the separation mechanisms and getting the CG just right. The orbiter, on the other hand, is an airplane - specifically a glider. It cannot be built with normal high powered rocketry techniques. I've gotten used to building things heavy duty (like the Nike and the ALCM), but in this case, the glider needs to be as light and strong as possible.
Therefore, I've decided to use 3D printed molds to build a carbon fiber/fiberglass shell. By using
Aramid Honeycomb, I can avoid bulkheads and tubes (typical HPR building techniques). In this world, the entire orbiter model is built in Fusion 360 and "subtracted" from mold blocks. The printing of these blocks takes a long time - in my first test of printing a fuselage core that was 8.5 x 8.5 inches, it took 3 days to print. The full fuselage is around 53" long and the cabin is 13" long. All told, just printing the molds will take nearly two months. Then the prep of the molds (filling and sanding) and the final casting. The good news is that when the molds are done, if I don't destroy them getting the form out, can be reused again and again. I'm not deceived about this project; I know I will destroy some orbiters figuring this whole thing out.
I've been doing research about this technique online and the best and closest practitioner I can find on the subject is Ramy RC - a brilliant RC builder in Germany. Here are some links - and don't be surprised when after you've viewed a few of these that you are inspired in new ways to build rockets.
Let me know your thoughts...