Retroactive post about this build and design since I finally got to launch this today. This is a semi-scale build designed after the rocket that is at the Udvar-Hazy Center in DC/VA. The F-23 has some nice size vertical fins and provided a good balance of size vs print time while providing some details I could do better with 3D printing. I measured scale from pictures and decided to do a BT-55 version with BT-50 ramjets -- comes in at a bit over 32" long (BT-60 + BT-55 also works for sport-scale proportions but was quite a bit bigger). The plan is to channel ejection gasses through the thick ramjet support members into the main tube. I was not sure this would work but it worked great -- better than I ever would have guessed. You could also build it with smaller chutes or streamers in the side engine pods if you taped off the connecting channels into the main body.
Here is my completed built version.
This model / design is in a good space for me since there are some nice details I can incorporate into the model to take it beyond something generic. It was a bit of a challenge to get the main connecting piece to print as a single part without tons of supports but I got the design to work well and minimized cleanup.
I had to do some gymnastics to get it to simulate in OR -- OR ignores the side ramjet tubes, unless they are tube fins, in stability calculations. I decided to put mock fins the same area as the tubes since these provide the majority of horizontal fin surface area. Surprised I still needed so much nose weight but it flew great. Should be nice launches on a pair of C5-3 or a D12-5 (assuming both engines ignite - rocket should get hung up on launch rail if only one lights up).
Finally had a chance to test launch this today and it flew great and ejected the nosecone with no issues. Sadly, my 8yo videographer is still in summer mode and so is out of practice making videos... Rocket flew nice and straight although it did rotate some (I think one engine might have ignited a little faster than the other which put it to spin around the launch rod a little on take off). To let him off a little easy, this did take off really fast due to the two engines. I decided to launch with smaller engines this time and it flew really nicely on a pair of B6-4 engines.
Here is my completed built version.
This model / design is in a good space for me since there are some nice details I can incorporate into the model to take it beyond something generic. It was a bit of a challenge to get the main connecting piece to print as a single part without tons of supports but I got the design to work well and minimized cleanup.
I had to do some gymnastics to get it to simulate in OR -- OR ignores the side ramjet tubes, unless they are tube fins, in stability calculations. I decided to put mock fins the same area as the tubes since these provide the majority of horizontal fin surface area. Surprised I still needed so much nose weight but it flew great. Should be nice launches on a pair of C5-3 or a D12-5 (assuming both engines ignite - rocket should get hung up on launch rail if only one lights up).
Finally had a chance to test launch this today and it flew great and ejected the nosecone with no issues. Sadly, my 8yo videographer is still in summer mode and so is out of practice making videos... Rocket flew nice and straight although it did rotate some (I think one engine might have ignited a little faster than the other which put it to spin around the launch rod a little on take off). To let him off a little easy, this did take off really fast due to the two engines. I decided to launch with smaller engines this time and it flew really nicely on a pair of B6-4 engines.
