eJar0k
Member
Been lurking for a while, so here's my first build thread.
I want to get into staged flights and recently signed on to beta test the Blue Raven, so I thought it'd be fun to make a staged scale scratch build. After some researching, I settled on a late-model Terrier, since the US Navy missiles with strakes just look cool and the missile/booster shape is actually pretty simple. The plan is to make a fairly small build that can fly from most fields on cheaper motors, be durable for lots of flights, and be used to test some new techniques.
Here's a rough OR model with some eyeballed dimensions. I originally wanted to do a 3"/54mm MMT booster and 54mm/38mm MMT sustainer, but I took it down to 38/29 and 54/38. Airframes and motor mounts will use glassed PML phenolic, a first time for me, while the interstage's "fairing" and nose will be 3D printed. The booster will take an Eggtimer Quantum for single deploy or cable cutter DD, and the sustainer will take the Raven and an Eggfinder Mini for drogueless DD. 1/8" Kevlar will connect everything to some Top Flight chutes. Fins will be 1/8" birch plywood on the sustainer and 1/4" on the booster, and might get glassed as well. Centering rings are also birch ply, but I might print the inner few rings on the sustainer with notches for fin alignment. Avbay sleds will be printed and use threaded rods+eye nuts, nothing special there; I have another 38mm MD build that I can copy from.
The staging plan is why I'm posting here in the first place, since I have a few problems to tackle and need advice.
First, wiring. The Raven will both fire a separation charge and light the sustainer motor, but I am not sure how to run connections down. The gap between the ISC's coupler and sustainer's MMT is about .065" nominal, which can slip an e-match wire and not much else. Currently, I want to run a pair of 3D-printed channels or some tubes down the motor mount for direct wiring, then connect those wires to some JST-RCY's on the avbay to break off at drogue deployment. The other ends will be bare and taped to the MMT (more on that later). There's basically zero space for connectors or terminals at the bottom, so the actual e-match leads will probably be loosely spliced and taped to these bare leads to hopefully fall off at sep/ignition. Any better ideas for a build this tight? I don't want to upsize, since this size is pretty cheap to fly and easy to transport. Plus, it's just darn cute.
Second, the ISC. I'll have a coupler stick about half a caliber into the sustainer and then get shear pinned in. From there, a bulkhead will sit just below the nozzle, and the booster's electronics will live below that. No hot staging, so no need to reinforce the interior. Centering rings will take the 38mm coupler to a 54mm coupler, and a 54mm bulkhead will cap off the bottom. A totally non-structural 3D-printed fairing will then join the gap and try to replicate the shape of the Terrier's actual interstage. I don't see any major issues here, except that the male coupler design makes wiring and sustainer motor retention difficult. Suggestions?
Third, motor retention. Again, there is almost room at the bottom of the sustainer for retention; not even a Slimline will fit. I thought a Slimline could be used as a coupler to a female interstage, but it doesn't really fit any standard tubing and makes sustainer ignition hard. I think I can just friction fit and use aluminum tape at the bottom, and that will allow me to tape down my avbay leads and then splice them. I'd love to hear a better method, though, since I'd rather use solid positive retention (and not buy hardware for an MD retainer).
Fourth, motor ignition. I don't want to solely fly blue motors and CTI has... issues... so I think I need to augment my igniters. I can also pop pyrodex pellets into my reloads, but obviously not in DMS. Any recommendations?
I think I can totally pull off the build as-is, but I'm always open to better ideas. If anyone has good sources for dimensions of the Terrier (even just the booster), please send them as well! I can document the build and dimensions for anyone that wants to replicate it.
I want to get into staged flights and recently signed on to beta test the Blue Raven, so I thought it'd be fun to make a staged scale scratch build. After some researching, I settled on a late-model Terrier, since the US Navy missiles with strakes just look cool and the missile/booster shape is actually pretty simple. The plan is to make a fairly small build that can fly from most fields on cheaper motors, be durable for lots of flights, and be used to test some new techniques.
Here's a rough OR model with some eyeballed dimensions. I originally wanted to do a 3"/54mm MMT booster and 54mm/38mm MMT sustainer, but I took it down to 38/29 and 54/38. Airframes and motor mounts will use glassed PML phenolic, a first time for me, while the interstage's "fairing" and nose will be 3D printed. The booster will take an Eggtimer Quantum for single deploy or cable cutter DD, and the sustainer will take the Raven and an Eggfinder Mini for drogueless DD. 1/8" Kevlar will connect everything to some Top Flight chutes. Fins will be 1/8" birch plywood on the sustainer and 1/4" on the booster, and might get glassed as well. Centering rings are also birch ply, but I might print the inner few rings on the sustainer with notches for fin alignment. Avbay sleds will be printed and use threaded rods+eye nuts, nothing special there; I have another 38mm MD build that I can copy from.
The staging plan is why I'm posting here in the first place, since I have a few problems to tackle and need advice.
First, wiring. The Raven will both fire a separation charge and light the sustainer motor, but I am not sure how to run connections down. The gap between the ISC's coupler and sustainer's MMT is about .065" nominal, which can slip an e-match wire and not much else. Currently, I want to run a pair of 3D-printed channels or some tubes down the motor mount for direct wiring, then connect those wires to some JST-RCY's on the avbay to break off at drogue deployment. The other ends will be bare and taped to the MMT (more on that later). There's basically zero space for connectors or terminals at the bottom, so the actual e-match leads will probably be loosely spliced and taped to these bare leads to hopefully fall off at sep/ignition. Any better ideas for a build this tight? I don't want to upsize, since this size is pretty cheap to fly and easy to transport. Plus, it's just darn cute.
Second, the ISC. I'll have a coupler stick about half a caliber into the sustainer and then get shear pinned in. From there, a bulkhead will sit just below the nozzle, and the booster's electronics will live below that. No hot staging, so no need to reinforce the interior. Centering rings will take the 38mm coupler to a 54mm coupler, and a 54mm bulkhead will cap off the bottom. A totally non-structural 3D-printed fairing will then join the gap and try to replicate the shape of the Terrier's actual interstage. I don't see any major issues here, except that the male coupler design makes wiring and sustainer motor retention difficult. Suggestions?
Third, motor retention. Again, there is almost room at the bottom of the sustainer for retention; not even a Slimline will fit. I thought a Slimline could be used as a coupler to a female interstage, but it doesn't really fit any standard tubing and makes sustainer ignition hard. I think I can just friction fit and use aluminum tape at the bottom, and that will allow me to tape down my avbay leads and then splice them. I'd love to hear a better method, though, since I'd rather use solid positive retention (and not buy hardware for an MD retainer).
Fourth, motor ignition. I don't want to solely fly blue motors and CTI has... issues... so I think I need to augment my igniters. I can also pop pyrodex pellets into my reloads, but obviously not in DMS. Any recommendations?
I think I can totally pull off the build as-is, but I'm always open to better ideas. If anyone has good sources for dimensions of the Terrier (even just the booster), please send them as well! I can document the build and dimensions for anyone that wants to replicate it.
