Things are coming together for a flight on my new sustainer rocket tomorrow, using a Loki J1026 motor.
This stage is designed as a new sustainer for my StratoSpear 3-stage rocket, and most of the build thread is over in the multi-stage sub-forum.
For electronics, I'm using 2 new 29mm diameter Blue Raven altimeters and a Featherweight GPS Tracker, which fit together with 2 batteries into an av-bay with 3" long threaded rods that are also the deployment terminals.
The 2 altimeters, 2 batteries, GPS tracker, 2 magnetic power switches (built into the 29mm Blue Ravens), top and bottom bulkheads, and attachment hardware to the motor and the chute cannon altogether weigh 69 grams. The chute cannon, chute, nosecone ejection piston, and harness combine for 76 grams.
The aft body with the fins is 120 grams, and the scratch-built nosecone is 82 grams, for a grand total of 347 grams empty weight. The motor weighs 1171 grams. The airframe, recovery and electronics come in at 23% of the launch weight.
Below is the full configuration with the av-bay, chute cannon, and the top of the nosecone ejector piston peeking out. You can see the antenna taped to the side of the carbon fiber chute cannon. Not ideal for RF range, but fortunately the Featherweight GPS tracker system has a lot of range margin.
The rocket is 39" long. 24.5" is motor, 11.2 is the curved part of the Von Karman nose cone, so the rocket is 3.3" longer than it could be if the recovery gear were smaller.
The rocket is expected to have about 100 Gs for 1.0 seconds, accelerating to Mach 2.8 in that time, if everything holds together. That's a pretty significant if, because this scratch rocket is all brand new. The fin stock is 0.060 mostly-unidirectional that I haven't used before, though the manufacturer claimed it used high-Tg resin. The carbon tubing is also supposed to use a high-Tg epoxy. The fins are a little delicate-looking to my eye, but at least I have some nice big fillets on them. They feel pretty stiff considering their shape and size. I installed them with a new fin jig I made from aluminum angles, and I think they're quite straight. The reason for the big sweep is that according to RASAero, the limiting case for the sustainer for stability is during the 3-stage configuration when the sustainer is going Mach 4 at 30,000 feet, and at those speeds, the sweep apparently really helps.
The nosecone and the fin fillets used Cotronics 4461 epoxy. Today I post-cured the airframe at 250F for a couple of hours and it came out just as smooth as it went in. This rocket has about 6.3" of stability margin, since it's designed for a sustainer application where after this flight I'll cut off about 3" of the aft body to expose that much motor as a coupler, moving the fins forward by about 3."
The deployments use a chute cannon that is new for this rocket but the same concept I have used before. The nosecone ejection uses a new small-diameter aluminum piston that's designed for reliability at very high altitudes. The ground testing went fine, with no surprises. The av-bay with 2 Blue Raven 29mm altimeters sharing 3 threaded rod/deployment terminals is similar to the setup I used last week in a 29mm rocket. The harness is fresh. The chute is scratch-built but well-tested on 29mm and 38mm rockets.
The rocket sims to a little over the current J record of 23,725 ft, held by Curt von Delius.
This stage is designed as a new sustainer for my StratoSpear 3-stage rocket, and most of the build thread is over in the multi-stage sub-forum.
For electronics, I'm using 2 new 29mm diameter Blue Raven altimeters and a Featherweight GPS Tracker, which fit together with 2 batteries into an av-bay with 3" long threaded rods that are also the deployment terminals.
The 2 altimeters, 2 batteries, GPS tracker, 2 magnetic power switches (built into the 29mm Blue Ravens), top and bottom bulkheads, and attachment hardware to the motor and the chute cannon altogether weigh 69 grams. The chute cannon, chute, nosecone ejection piston, and harness combine for 76 grams.
The aft body with the fins is 120 grams, and the scratch-built nosecone is 82 grams, for a grand total of 347 grams empty weight. The motor weighs 1171 grams. The airframe, recovery and electronics come in at 23% of the launch weight.
Below is the full configuration with the av-bay, chute cannon, and the top of the nosecone ejector piston peeking out. You can see the antenna taped to the side of the carbon fiber chute cannon. Not ideal for RF range, but fortunately the Featherweight GPS tracker system has a lot of range margin.
The rocket is 39" long. 24.5" is motor, 11.2 is the curved part of the Von Karman nose cone, so the rocket is 3.3" longer than it could be if the recovery gear were smaller.
The rocket is expected to have about 100 Gs for 1.0 seconds, accelerating to Mach 2.8 in that time, if everything holds together. That's a pretty significant if, because this scratch rocket is all brand new. The fin stock is 0.060 mostly-unidirectional that I haven't used before, though the manufacturer claimed it used high-Tg resin. The carbon tubing is also supposed to use a high-Tg epoxy. The fins are a little delicate-looking to my eye, but at least I have some nice big fillets on them. They feel pretty stiff considering their shape and size. I installed them with a new fin jig I made from aluminum angles, and I think they're quite straight. The reason for the big sweep is that according to RASAero, the limiting case for the sustainer for stability is during the 3-stage configuration when the sustainer is going Mach 4 at 30,000 feet, and at those speeds, the sweep apparently really helps.
The nosecone and the fin fillets used Cotronics 4461 epoxy. Today I post-cured the airframe at 250F for a couple of hours and it came out just as smooth as it went in. This rocket has about 6.3" of stability margin, since it's designed for a sustainer application where after this flight I'll cut off about 3" of the aft body to expose that much motor as a coupler, moving the fins forward by about 3."
The deployments use a chute cannon that is new for this rocket but the same concept I have used before. The nosecone ejection uses a new small-diameter aluminum piston that's designed for reliability at very high altitudes. The ground testing went fine, with no surprises. The av-bay with 2 Blue Raven 29mm altimeters sharing 3 threaded rod/deployment terminals is similar to the setup I used last week in a 29mm rocket. The harness is fresh. The chute is scratch-built but well-tested on 29mm and 38mm rockets.
The rocket sims to a little over the current J record of 23,725 ft, held by Curt von Delius.