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I've been working on the design of my first two-stage project over the past couple of months and am about to start fabrication. It's only fitting that I take the opportunity to post my first build-thread on TRF despite having more than a few scratch-builds in my fleet. I am absolutely welcoming input from those with far more experience than me - especially the staging gurus who have supplied ample late-night reading for me over the years. That said, I've already purchased most of the material and am beginning fabrication. This first post is somewhat posthumous with regard to the design process.
The name of this project is a not-so-subtle riff on one of my all-time favorite rockets: the Aerobee High. I actually purchased and built a Cosmodrome Aerobee kit years ago that promptly found its way into a soy-bean field where it resided over the winter and spring; returning to me somewhat worse for wear. Hopefully, this build will not share the same fate.
The entire vehicle has been modeled both in Fusion 360 (for fabrication as well as exports for 3D printed parts) and RockSim for flight simulations. The images below are taken from the Fusion 360 model.
Project Goals:
1. Design and build to fly on a wide range of motor combinations (including sustainer only) that stay under local field waiver (East Coast field).
2. Utilize construction methods developed on non-staged projects that combine fiberglass and 3D printed components.
3. Minimum diameter on the booster so 54mm booster motors can be flown (this is driven more by the Aerobee High configuration that had a smaller diameter booster than sustainer).
View attachment ARO-B - ARO-B.jpg
View attachment ARO-B - DIMENSIONS.jpg
BOOSTER
The booster airframe is 54mm fiberglass minimum diameter with 3 swept trapezoidal fins. I like this plan form due to its long root cord that provides longitudinal strength. It also pushes the bulk of the surface area aft benefitting CP, but not so far as to risk breaking in rough landings (such as a swept delta). Booster motors will be retained via a minimum diameter retainer and 5/16" threaded rod to a threaded/plugged closure. An adapter can be used for 38mm motors. Following is a cut-away view of the booster with the motor retainage (the airframe has been hidden in this view).
View attachment ARO-B - MOTOR RETAINER.jpg
INTERSTAGE COUPLER
The interstage coupler is constructed from a 54mm coupler that houses the booster avionics and GPS tracker. The booster nose cone is 3d printed PETG with 50% infill. The nose cone will be epoxied into the 54mm avionics coupler. The interstage base of the sustainer coupling is also 3d printed PETG with 50% infill and will be epoxied into a 65mm fiberglass coupler. These two pieces are then tied together with 3 high strength, thick-walled aluminum struts. An Eggtimer quantum will control the booster deployment event. For higher altitude flights, the booster parachute (24" semi-circumference ultralight hemispherical) will be deployed via Jolly Logic Chute Release. The ISC avionics bay also includes an Eggfinder Mini GPS transmitter. Both the Quantum and the Eggfinder mini are mounted to 3d printed PETG trays. In order to mitigate potential impacts on the radio and GPS antennae, the aft bulkhead of the booster avionics bay will be held in place with knurled nuts and nylon threaded rods. Given the relatively low mass of the booster, I’m comfortable that the nylon rods (and threads) have sufficient tensile strength to hold everything together. The ISC sustainer coupling extends into the aft end of the sustainer 1.3 calipers. The 3d printed sustainer base is printed with a well for the separation charge.
E-matches for the separation charge and air start will run down internal conduits made from 3/16" diameter Garolite.
Following are views of the ISC.
View attachment ARO-B - INTERSTAGE COUPLER.jpg
View attachment ARO-B - INTERSTAGE COUPLER SECTION.jpg
SUSTAINER
The sustainer has a 65mm airframe. It incorporates 3 swept trapezoidal fins similar to the booster, though with a longer root cord and shorter semi-span. These fins will be through-wall and epoxied to the 38mm motor mount and centering rings.
In the avionics bay, an Eggtimer proton will control the primary sustainer deployment events as well as the separation charge and air start. The proton has a barometric sensor and a 200g accelerometer. For air-starts, the proton incorporates a barometric/acceleration deviation qualification for lock-out. The barometric readings are used to compute the vertical distance from the ground while the accelerometer data is integrated to arrive at the total distance traveled. If the difference between these values deviates beyond a preset threshold, the air-start is locked out. The proton will be connected to a telemetry module that will send real time flight data to a ground station. While the proton's arming features are Wi-Fi enabled, a pull-pin switch will be used for additional safety at the pad and to satisfy any RSO's that insist on a mechanical switch or shunt on the air-start e-match. An Eggtimer quantum will control redundant recovery deployments.
The drogue will be a 6.5" parabolic. The main will be a 42" (semi-circumference) hemispherical. All tethers will be 3/16" tubular Kevlar.
The nose cone is a 5:1 Von Karmen with aluminum tip. The sustainer GPS transmitter is housed in a bay in the nose cone and mounted to a 3d printed PETG sled.
Following are views of the avionics bay and the nose cone GPS bay.
View attachment ARO-B - SUSTAINER AVIONICS.jpg
View attachment ARO-B - GPS BAY.jpg
Next post will include static and dynamic analysis of the design.
The name of this project is a not-so-subtle riff on one of my all-time favorite rockets: the Aerobee High. I actually purchased and built a Cosmodrome Aerobee kit years ago that promptly found its way into a soy-bean field where it resided over the winter and spring; returning to me somewhat worse for wear. Hopefully, this build will not share the same fate.
The entire vehicle has been modeled both in Fusion 360 (for fabrication as well as exports for 3D printed parts) and RockSim for flight simulations. The images below are taken from the Fusion 360 model.
Project Goals:
1. Design and build to fly on a wide range of motor combinations (including sustainer only) that stay under local field waiver (East Coast field).
2. Utilize construction methods developed on non-staged projects that combine fiberglass and 3D printed components.
3. Minimum diameter on the booster so 54mm booster motors can be flown (this is driven more by the Aerobee High configuration that had a smaller diameter booster than sustainer).
View attachment ARO-B - ARO-B.jpg
View attachment ARO-B - DIMENSIONS.jpg
BOOSTER
The booster airframe is 54mm fiberglass minimum diameter with 3 swept trapezoidal fins. I like this plan form due to its long root cord that provides longitudinal strength. It also pushes the bulk of the surface area aft benefitting CP, but not so far as to risk breaking in rough landings (such as a swept delta). Booster motors will be retained via a minimum diameter retainer and 5/16" threaded rod to a threaded/plugged closure. An adapter can be used for 38mm motors. Following is a cut-away view of the booster with the motor retainage (the airframe has been hidden in this view).
View attachment ARO-B - MOTOR RETAINER.jpg
INTERSTAGE COUPLER
The interstage coupler is constructed from a 54mm coupler that houses the booster avionics and GPS tracker. The booster nose cone is 3d printed PETG with 50% infill. The nose cone will be epoxied into the 54mm avionics coupler. The interstage base of the sustainer coupling is also 3d printed PETG with 50% infill and will be epoxied into a 65mm fiberglass coupler. These two pieces are then tied together with 3 high strength, thick-walled aluminum struts. An Eggtimer quantum will control the booster deployment event. For higher altitude flights, the booster parachute (24" semi-circumference ultralight hemispherical) will be deployed via Jolly Logic Chute Release. The ISC avionics bay also includes an Eggfinder Mini GPS transmitter. Both the Quantum and the Eggfinder mini are mounted to 3d printed PETG trays. In order to mitigate potential impacts on the radio and GPS antennae, the aft bulkhead of the booster avionics bay will be held in place with knurled nuts and nylon threaded rods. Given the relatively low mass of the booster, I’m comfortable that the nylon rods (and threads) have sufficient tensile strength to hold everything together. The ISC sustainer coupling extends into the aft end of the sustainer 1.3 calipers. The 3d printed sustainer base is printed with a well for the separation charge.
E-matches for the separation charge and air start will run down internal conduits made from 3/16" diameter Garolite.
Following are views of the ISC.
View attachment ARO-B - INTERSTAGE COUPLER.jpg
View attachment ARO-B - INTERSTAGE COUPLER SECTION.jpg
SUSTAINER
The sustainer has a 65mm airframe. It incorporates 3 swept trapezoidal fins similar to the booster, though with a longer root cord and shorter semi-span. These fins will be through-wall and epoxied to the 38mm motor mount and centering rings.
In the avionics bay, an Eggtimer proton will control the primary sustainer deployment events as well as the separation charge and air start. The proton has a barometric sensor and a 200g accelerometer. For air-starts, the proton incorporates a barometric/acceleration deviation qualification for lock-out. The barometric readings are used to compute the vertical distance from the ground while the accelerometer data is integrated to arrive at the total distance traveled. If the difference between these values deviates beyond a preset threshold, the air-start is locked out. The proton will be connected to a telemetry module that will send real time flight data to a ground station. While the proton's arming features are Wi-Fi enabled, a pull-pin switch will be used for additional safety at the pad and to satisfy any RSO's that insist on a mechanical switch or shunt on the air-start e-match. An Eggtimer quantum will control redundant recovery deployments.
The drogue will be a 6.5" parabolic. The main will be a 42" (semi-circumference) hemispherical. All tethers will be 3/16" tubular Kevlar.
The nose cone is a 5:1 Von Karmen with aluminum tip. The sustainer GPS transmitter is housed in a bay in the nose cone and mounted to a 3d printed PETG sled.
Following are views of the avionics bay and the nose cone GPS bay.
View attachment ARO-B - SUSTAINER AVIONICS.jpg
View attachment ARO-B - GPS BAY.jpg
Next post will include static and dynamic analysis of the design.
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