mikebpd221
Active Member
- Joined
- May 9, 2019
- Messages
- 36
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- 20
I'm looking at trying my first two stage project and selected the first boosted Arcas as a model to emulate. Lots of good kit models of the HV sustainer although I found what appears to be an odd artifact in the first boosted version. I've seen photos of the first boosted version that have the extended fin profile common to all of the HV variants but it retains the boat tail rear end of the single stage version. I've added my project inspiration photo below. I'm curious as to how the interstage coupling was accomplished with the pictured arrangement and how best to incorporate it into a one half scale model. I'm using the 2.2" MAC Performance kit as a base for the HV ARCAS and I had an extra boat tail in the parts bin that fits that body tube and a 29mm motor mount. The museum displays I've seen of the single stage Arcas also have a flare at the end of the boat tail, a detail the Semroc version includes in their model. I'm at something of a loss as how that seats in the interstage on the booster. I'm thinking a flat ring at the top of the interstage of the same external diameter as the body, with a stepped inner diameter, the outer part for the boattail flare, and an inner diameter just larger than the motor retainer. I'm planning on using a slimline retainer to keep the outside of the retainer as small as possible. I figure this would allow for a seating ring that measures 1/2" thick ring with the same height divided into the two steps. Small pins set into the flare or raised notches at the fin roots would prevent rotation between the two stages prior to drag separation. I'm going to prototype the interstage before I go anywhere else on the build since that's the challenge I don't have worked out yet. This group definitely has members more experienced than me at this and I wanted to get some input to aspects I may not have considered. I've seen the NASA report on their sounding rockets that's cited in a number or ARCAS threads and that really falls short on design specifics. I'm surprised to see that no one seems to have done the build I'm contemplating, unless the early two stage design was abandoned after limited launches because it just didn't work very well. At any rate, input is appreciated.