I have been making some pretty light 38mm rockets, but this post:
https://www.rocketryforum.com/threa...omposite-case-38mm-rocket.183709/post-2523215
showed me that I could be a lot more radical in my weight savings. In particular, this rocket got to Mach 5 by replacing the commercial Al motor case with an integrated motor case/body tube. Which got me to thinking.
The Loki 38-1200 motors are awesome, the highest impulse 38mm motors available. The build quality is great, and they have survived a lot of my abuse. But the Al case is not particularly light; it seems to have been designed with quite a bit of margin. Dropping an empty CTI Pro38 case from a table onto concrete can render it unusable. Not so with the 38-1200. What if I took the awesome K627 reload, which already requires bonding the grains into the nice Loki phenolic liner, and laid up a carbon fiber motor case around the liner, that also becomes a body tube? Could that help enough to get a space shot on a 2-stage 54-38mm rocket?
With a sustainer build the way I have been doing for record attempts, including a J1026 flight to over 24 kft, and with similar build style on the booster, I get about 280k for a simulation of a Loki M1378 to K627. This is with smooth paint and biconic fin profile options. But if I can take 1/2 lb off of the rocket (the 38-1200 motor case is 14 oz) by replacing the body tube and the Aluminum motor case with a single composite layup, which also reduces the rocket OD down to about 1.50", the sim goes up to 388k. This is with a sustainer all-up mass of 3 lbs. For comparison, the K627 with the aluminum case, by itself, is 2.75 lbs.
This was a quick and dirty set of modeling to satisfy my curiosity, and I'm sure there are at least minor errors.
But this is pretty encouraging. For years I have had a very long-term goal to do a space shot. This strategy has the potential to save years off of my timeline, and thousands of dollars. I mean, these are motors I have in my garage already, right now.
An M1378-K627-K627 3-stage sims to ridiculous altitudes, by the way.
I'm not planning to mix motors, ever (I'm a messy builder and don't trust myself with AP and fuel in my garage), but laying up an adequate composite case around the K627 reload with its liner is something I can do, or at least I'm pretty sure I can figure it out and verify it with some test burns on the ground. I know I can use using Cotronics 4461 epoxy to make some nice thin, light, carbon fins that stand up to Mach ~3 at low altitude, without a blemish. Whether they can stay smooth after Mach 5.5 at 48 kft is unknown, but I'll hopefully get a lot closer to testing that out with my planned 38mm 3-stage attempt at Balls this fall.
So now my plan is to continue my 38mm multi-stage plans for this season, and then get ready to do some ground test burns after that to validate how much lighter I can make a K627 sustainer, with an eye toward making a space shot attempt at Balls 2025. Oh, and I need to get my L3 certification in there somewhere. Maybe this year at Balls after I send a 3-stage 38mm rocket over 100 kft. .... I kid. Maybe. Tis the season for running sims and dreaming.
https://www.rocketryforum.com/threa...omposite-case-38mm-rocket.183709/post-2523215
showed me that I could be a lot more radical in my weight savings. In particular, this rocket got to Mach 5 by replacing the commercial Al motor case with an integrated motor case/body tube. Which got me to thinking.
The Loki 38-1200 motors are awesome, the highest impulse 38mm motors available. The build quality is great, and they have survived a lot of my abuse. But the Al case is not particularly light; it seems to have been designed with quite a bit of margin. Dropping an empty CTI Pro38 case from a table onto concrete can render it unusable. Not so with the 38-1200. What if I took the awesome K627 reload, which already requires bonding the grains into the nice Loki phenolic liner, and laid up a carbon fiber motor case around the liner, that also becomes a body tube? Could that help enough to get a space shot on a 2-stage 54-38mm rocket?
With a sustainer build the way I have been doing for record attempts, including a J1026 flight to over 24 kft, and with similar build style on the booster, I get about 280k for a simulation of a Loki M1378 to K627. This is with smooth paint and biconic fin profile options. But if I can take 1/2 lb off of the rocket (the 38-1200 motor case is 14 oz) by replacing the body tube and the Aluminum motor case with a single composite layup, which also reduces the rocket OD down to about 1.50", the sim goes up to 388k. This is with a sustainer all-up mass of 3 lbs. For comparison, the K627 with the aluminum case, by itself, is 2.75 lbs.
This was a quick and dirty set of modeling to satisfy my curiosity, and I'm sure there are at least minor errors.
But this is pretty encouraging. For years I have had a very long-term goal to do a space shot. This strategy has the potential to save years off of my timeline, and thousands of dollars. I mean, these are motors I have in my garage already, right now.
An M1378-K627-K627 3-stage sims to ridiculous altitudes, by the way.
I'm not planning to mix motors, ever (I'm a messy builder and don't trust myself with AP and fuel in my garage), but laying up an adequate composite case around the K627 reload with its liner is something I can do, or at least I'm pretty sure I can figure it out and verify it with some test burns on the ground. I know I can use using Cotronics 4461 epoxy to make some nice thin, light, carbon fins that stand up to Mach ~3 at low altitude, without a blemish. Whether they can stay smooth after Mach 5.5 at 48 kft is unknown, but I'll hopefully get a lot closer to testing that out with my planned 38mm 3-stage attempt at Balls this fall.
So now my plan is to continue my 38mm multi-stage plans for this season, and then get ready to do some ground test burns after that to validate how much lighter I can make a K627 sustainer, with an eye toward making a space shot attempt at Balls 2025. Oh, and I need to get my L3 certification in there somewhere. Maybe this year at Balls after I send a 3-stage 38mm rocket over 100 kft. .... I kid. Maybe. Tis the season for running sims and dreaming.
