Brian H.
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Unfortunately not any more after some property was developed just east of our site.
StratoSpear: 38mm 3-stage for complex L record attempt
- Thread starter Adrian A
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GrouchoDuke
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Wait, what?? Hartsel is now limited to 8k AGL? The last email from John said there were still call-ins to 14.2.
Adrian if so, the Alamosa NAR folks are awesome to fly with too.
Adrian if so, the Alamosa NAR folks are awesome to fly with too.
Brian H.
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I am so sorry. I was talking Tripoli Southern Colorado in Pueblo
GrouchoDuke
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Cool, thanks. Whew.
I drilled out two motors to use their casings to make pistons, a 24mm SU motor for the chute cannon, and an 18mm motor (shown with the nozzle sanded off) for the nosecone ejection piston. The little disks are FG pieces I'm gluing on the end with JB weld.
I did a test-fit of harness wrapped around the chute cannon and revived a simple kevlar-wrapping jig I made years ago. After I installed all the harness I could, I did a fit check with a test nosecone (above) and was happy to see that the test nosecone is longer than it needs to be by at least 1/2". Also, that amount of Kevlar turned out to be 18 feet, which seemed excessive, so I cut it down to 12. The harness from chute to rocket to nosecone is all 1 piece, and I'm planning to allocate it with about 9' for the nosecone deployment and about 3' for the chute deployment.
My new Cotronics 4461 epoxy arrived today, and once my new Silicone mold release arrives, I'll be laying up the flight nosecone, just in time to test it on Sunday.
I did a test-fit of harness wrapped around the chute cannon and revived a simple kevlar-wrapping jig I made years ago. After I installed all the harness I could, I did a fit check with a test nosecone (above) and was happy to see that the test nosecone is longer than it needs to be by at least 1/2". Also, that amount of Kevlar turned out to be 18 feet, which seemed excessive, so I cut it down to 12. The harness from chute to rocket to nosecone is all 1 piece, and I'm planning to allocate it with about 9' for the nosecone deployment and about 3' for the chute deployment.
My new Cotronics 4461 epoxy arrived today, and once my new Silicone mold release arrives, I'll be laying up the flight nosecone, just in time to test it on Sunday.
Layup prep done, except for putting mold release on the mold. Last week I did a test run on a 29mm silicone mold with a different mold release. That was a dismal failure, and now that mold is pretty much destroyed. So I have some new mold release to try that's out for delivery now.
From left, and in order of use:
From left, and in order of use:
- 18mm and 24mm cardboard tube tools to help insert the wet composite sleeves and push/expand them into place
- 0.75" light carbon sleeve (this and all other sleeves from Soller composites). I'll install this against the mold. This time I'm going to try adding some silica-thickened epoxy to the outside before I put it into the mold, in hopes of reducing/eliminating print-through.
- 1.5" light carbon sleeve, will go against the mold with some overlap with the 0.75" sleeve. The portion not covered by the two 1.5" sleeves will have cast tungsten/epoxy, so the 0.75" sleeve is mostly to help provide a smooth sandable surface
- 1.5" light fiberglass sleeve, installed against the mold. This is FG for radio transparency since this is where the av-bay will be.
- Pre-cured FG tube. This is the tube I made a few posts ago, with the smaller inside diameter I want for a solid overlap with the sustainer coupler. I tapered the forward end down to a knife-edge, and sanded off all the high spots (I do love my bench-mounted belt sander)
- 1.5" heavy carbon fiber sleeve. This is intended to go from the cast noseweight area all the way back to overlap with the FG tube. It will be installed against the other layers and overlapping a bit with both FG parts. This reminds me, I should trim back the masking a little on the pre-cured FG tube
- Polyester peel ply. I hope to use the cardboard tube tools to get these approximately into the right places. This peel ply is to give the vacuum bag a bit of a path to suck the air out, and to give the inner vacuum bag something to slide against as it gets inserted.
- Inner vacuum bag, made by brushing silicone onto the male plug. It is intended to push the layup against the silicone mold surface with atmospheric pressure. It's a larger diameter than it should be (I would have had to make an entire other plug to get it the right size) so I will live with a pleat/wrinkle somewhere on the inside.
- Silicone mold, cast inside a 54mm FG tube. I have release tape on the outside because the goal is to get excess resin sucked out through the mold opening between the inner bag and the mold, and it will wind up there.
- The original mold plug, just for reference. Its job is done, but I had it out to help visualize where the cylindrical part of the nosecone starts, and to measure the biaxial sleeves.
Wow, that was hard. The 4461IP resin was a lot more viscous and sticky than I'm used to for laminating resin, so adding the thickener probably wasn't necessary. I think I'm going to wind up with a rather resin-rich nosecone.
The smallest forward CF piece was the only one that went in pretty easily. The FG sleeve took 3 tries, both 1.5" sleeves took about 4 tries, and the peel ply took about 10, where each try I had to start over and pull the piece completely out In the middle I made a new tool, a narrow metal rod that I covered with flash breaking tape and mold release to try to get some kind of tool I could put into the mold to push without pulling out whatever it was touching. I think I went through 8 pairs of gloves. I really hope this cures well because I really don't want to redo it. If I have to, may use the 4461 resin for the outermost layer and then do a secondary layup with the 820 laminating resin that's not nearly so sticky.
Here's the current status:
My vacuum bag is just a garbage bag twisted and clamped closed. Then I put a little hole at the open end and pulled the inner vacuum bag flange through the hole. Nothing really sticks to that silicone, so I put a ring of vacuum sealing putty around the flange of it and set the whole thing on top, which seemed to do the trick. I was going to do a heated cure, but I'm now inclined to just let it go at least overnight at room temperature to allow more of the resin to flow around and hopefully out. There were a few times when I added extra resin to the tools just to use as a lube.
The smallest forward CF piece was the only one that went in pretty easily. The FG sleeve took 3 tries, both 1.5" sleeves took about 4 tries, and the peel ply took about 10, where each try I had to start over and pull the piece completely out In the middle I made a new tool, a narrow metal rod that I covered with flash breaking tape and mold release to try to get some kind of tool I could put into the mold to push without pulling out whatever it was touching. I think I went through 8 pairs of gloves. I really hope this cures well because I really don't want to redo it. If I have to, may use the 4461 resin for the outermost layer and then do a secondary layup with the 820 laminating resin that's not nearly so sticky.
Here's the current status:
My vacuum bag is just a garbage bag twisted and clamped closed. Then I put a little hole at the open end and pulled the inner vacuum bag flange through the hole. Nothing really sticks to that silicone, so I put a ring of vacuum sealing putty around the flange of it and set the whole thing on top, which seemed to do the trick. I was going to do a heated cure, but I'm now inclined to just let it go at least overnight at room temperature to allow more of the resin to flow around and hopefully out. There were a few times when I added extra resin to the tools just to use as a lube.
Here's how it came out of the mold, and after I peeled enough masking back so I could install it on the end of the sustainer:
It turns out that the smallest sleeve that I thought went down easily didn't go in all the way, so it didn't make much contact with the mold. There were some other significant moldless parts like that. The part that took the longest to deal with is slightly visible in the blue-ish part of the fiberglass above; the heavy 1.5" sleeve didn't go down far enough, and it had about 1.25" overlap with the blue masking tape on the ID. Getting rid of that was possible using a small, sharp chisel:
followed by 120 grid sandpaper on a stick. This thread isn't about just showing off the pretty stuff.
After using the belt sander to sand everything down to expose the low spots, it looks like this:
and my finger looks like this after it got snagged by the disc sander of my otherwise-beloved benchtop belt sander and was caught against the piece holder:
(just kidding, nobody wants to see that) Just a flesh wound, fortunately.
I slathered up the nosecone with more epoxy and put it back into the mold to fill in more of the low spots. I suspect I'll still have a few bubbles so I'll probably have to do it again, but one re-mold should be good enough for tomorrow's launch. I have it curing now at about 100 F and when that sets up I'll either de-mold it or just leave it in place to cast the tip of the nosecone with tungsten powder and install the shock cord holder.
I updated the simulation model with new measurements and weights to figure out how much tip weight I need. I'm going to add 170 grams to the tip of the nosecone to put the sustainer minimum stability margin right at 2.0. I think RASAero has the right rule of thumb for that. Speaking of which, Chuck Rogers kindly contacted me and pointed out that with the expected max speed over Mach 3, that thermal surface damage is to be expected, which I should simulate using all turbulent flow and camouflage paint. With those assumptions, the expected altitude is around 90,000 feet. I would be happy with that, to say the least. I'm expecting this flight to bring out all of the considerable flaws in the nosecone and fin layups in terms of poor resin control, bubbles, etc. I think the nosecone is thick and strong enough to withstand some weakening and scouring of the outer surface. But I have had a nosecone I made implode on me at Mach 2.8 before, so I might not be the best one to judge. This one I could definitely stand on without damage, and I don't think that was true from what I can recollect from way back when.
It turns out that the smallest sleeve that I thought went down easily didn't go in all the way, so it didn't make much contact with the mold. There were some other significant moldless parts like that. The part that took the longest to deal with is slightly visible in the blue-ish part of the fiberglass above; the heavy 1.5" sleeve didn't go down far enough, and it had about 1.25" overlap with the blue masking tape on the ID. Getting rid of that was possible using a small, sharp chisel:
followed by 120 grid sandpaper on a stick. This thread isn't about just showing off the pretty stuff.
After using the belt sander to sand everything down to expose the low spots, it looks like this:
and my finger looks like this after it got snagged by the disc sander of my otherwise-beloved benchtop belt sander and was caught against the piece holder:
(just kidding, nobody wants to see that) Just a flesh wound, fortunately.
I slathered up the nosecone with more epoxy and put it back into the mold to fill in more of the low spots. I suspect I'll still have a few bubbles so I'll probably have to do it again, but one re-mold should be good enough for tomorrow's launch. I have it curing now at about 100 F and when that sets up I'll either de-mold it or just leave it in place to cast the tip of the nosecone with tungsten powder and install the shock cord holder.
I updated the simulation model with new measurements and weights to figure out how much tip weight I need. I'm going to add 170 grams to the tip of the nosecone to put the sustainer minimum stability margin right at 2.0. I think RASAero has the right rule of thumb for that. Speaking of which, Chuck Rogers kindly contacted me and pointed out that with the expected max speed over Mach 3, that thermal surface damage is to be expected, which I should simulate using all turbulent flow and camouflage paint. With those assumptions, the expected altitude is around 90,000 feet. I would be happy with that, to say the least. I'm expecting this flight to bring out all of the considerable flaws in the nosecone and fin layups in terms of poor resin control, bubbles, etc. I think the nosecone is thick and strong enough to withstand some weakening and scouring of the outer surface. But I have had a nosecone I made implode on me at Mach 2.8 before, so I might not be the best one to judge. This one I could definitely stand on without damage, and I don't think that was true from what I can recollect from way back when.
The nosecone came out of the mold with about 70% of the low spots filled in, and with the cast tungsten nose tip and shock cord holder installed. Good enough for today for tomorrow's test flights. With so much of the weight concentrated at the nose tip (you can get some idea from where the balance point is in the photo), and with the nosecone so slender and sharp, the rocket feels... dangerous. Like it's trying to live up to its new name.
I had a nervous time pulling the kevlar thread through the eye of the hanger bolt in the nosecone, and then pulling through an intermediate size cord. I wanted to use a bigger cord but I couldn't get it to go through, so I decided to double up on the smaller cord. If I had lost the thread during the process, I'm not sure the nosecone would have been recoverable.
Getting deployment charges prepped for tomorrow:
I had a nervous time pulling the kevlar thread through the eye of the hanger bolt in the nosecone, and then pulling through an intermediate size cord. I wanted to use a bigger cord but I couldn't get it to go through, so I decided to double up on the smaller cord. If I had lost the thread during the process, I'm not sure the nosecone would have been recoverable.
Getting deployment charges prepped for tomorrow:
GrouchoDuke
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Fly well tomorrow! (...and get good data!)
Due to some last minute debugging of Blue Raven software I ran out of prep time and didn't fly StratoSpear yesterday. A good lesson on getting ready early. I did pick up the K motors, though. This week I'll test the new nosecone ejector piston and the chute cannon, and finish the nosecone. I think I'll vacuum bag it this time to get the rest of the bubbles out.
I just did a test-fit of my new Loki case in the second stage, and it doesn't really fit, diameter-wise. I can only squeeze it in about 1/2". Anyone have suggestions for increasing the inside diameter a few thousandsths? Flap-wheel sander or something?
Edit:
I have a borrowed case and one that I bought. I checked the borrowed one, and it does fit into the second stage. And the new one fits into the carbon tube I have for the booster. So I guess I won't need to do any mods.
The new case is about 1.504, and the borrowed case is about 1.495. I made the second stage around a 1.500 mandrel with 1 wrap of mylar that makes it about 1.504
Edit:
I have a borrowed case and one that I bought. I checked the borrowed one, and it does fit into the second stage. And the new one fits into the carbon tube I have for the booster. So I guess I won't need to do any mods.
The new case is about 1.504, and the borrowed case is about 1.495. I made the second stage around a 1.500 mandrel with 1 wrap of mylar that makes it about 1.504
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StratoSpear is going to be a crazy long 38mm rocket. The silver tube on the left is one of my 6' tower poles for reference. The sustainer will start out almost entirely out of the tower.
The blue Loki case exposed in the photo is about how much overlap I'll have with the first stage booster. That tube is a relatively loose fit, so I'm considering just doing drag separation and motor ejection for the first stage chute deployment to save some complexity, cost, time, and rocket length. If I do that I would want to put some vent holes near the base of the 2nd stage motor so the booster doesn't take too long to come off.
The blue Loki case exposed in the photo is about how much overlap I'll have with the first stage booster. That tube is a relatively loose fit, so I'm considering just doing drag separation and motor ejection for the first stage chute deployment to save some complexity, cost, time, and rocket length. If I do that I would want to put some vent holes near the base of the 2nd stage motor so the booster doesn't take too long to come off.
Sustainer deployment testing yesterday.
What it looks like under the chute cannon during wiring:
Just before loading black powder into the nosecone ejection piston at the top:
I put in 0.5 grams of loose powder into it. The chute cannon got a premade charge that is like what I have used before for previous iterations of the chute cannon: A 1/4" launch lug cardboard tube cut 5/8" long, one of the charges in post 69.
The results was dramatic (sorry for the poor camera work, needed 3 hands):
View attachment IMG_9656 (2).MOV
Both charges fired simultaneously, and they weren't supposed to. The video doesn't capture the sharp crack sound of a shock wave, but it does capture the echo as the report bounced off of the neighbor's houses.
The base of the nosecone piston was blown off, and I believe that was what allowed the main chute to get burned.
At first I guessed I had accidentally hooked up the two test leads to Apo and Main rather than Apo and +Arm, which would have fired both charges in series, but with the crappy video work I accidentally recorded the connections in the end of the video above, and after looking at some screen captures I'm pretty sure the test leads were connected to the right wires. This morning I checked continuity through the test leads to see if I had a wire crossed inside the test connection. No such luck. So I'm left scratching my head. I don't think it was a sympathetic firing, because the chute was in between the two charges. I had some oversized rings on the test wiring, which could have shorted to the body tube, but I would be surprised if it is conductive enough on the inside of the tube, despite being made of carbon. Maybe the Apo and main wires were touching in the grass?
Most of the joint was JB weld that failed, which is the lighter gray compared to the carbon.
What it looks like under the chute cannon during wiring:
Just before loading black powder into the nosecone ejection piston at the top:
I put in 0.5 grams of loose powder into it. The chute cannon got a premade charge that is like what I have used before for previous iterations of the chute cannon: A 1/4" launch lug cardboard tube cut 5/8" long, one of the charges in post 69.
The results was dramatic (sorry for the poor camera work, needed 3 hands):
View attachment IMG_9656 (2).MOV
Both charges fired simultaneously, and they weren't supposed to. The video doesn't capture the sharp crack sound of a shock wave, but it does capture the echo as the report bounced off of the neighbor's houses.
The base of the nosecone piston was blown off, and I believe that was what allowed the main chute to get burned.At first I guessed I had accidentally hooked up the two test leads to Apo and Main rather than Apo and +Arm, which would have fired both charges in series, but with the crappy video work I accidentally recorded the connections in the end of the video above, and after looking at some screen captures I'm pretty sure the test leads were connected to the right wires. This morning I checked continuity through the test leads to see if I had a wire crossed inside the test connection. No such luck. So I'm left scratching my head. I don't think it was a sympathetic firing, because the chute was in between the two charges. I had some oversized rings on the test wiring, which could have shorted to the body tube, but I would be surprised if it is conductive enough on the inside of the tube, despite being made of carbon. Maybe the Apo and main wires were touching in the grass?
Most of the joint was JB weld that failed, which is the lighter gray compared to the carbon.
Yesterday I rebuilt the nosecone ejection piston, and did a secondary layup with a short section of biaxial CF sleeve that was supposed to wrap around the bottom. But the Soller epoxy I used was really slick and I couldn't manage to get the fibers to wrap around properly. If it doesn't stay on with today's testing I'll start with some CF on the base, clamp it down, and then wrap it up the sides of the tube so that I get fibers wrapping around the joint.
The corrections for today's testing will be to more thoroughly check the continuity as I go along, and start with 0.3 grams of BP in the nosecone ejection piston.
The corrections for today's testing will be to more thoroughly check the continuity as I go along, and start with 0.3 grams of BP in the nosecone ejection piston.
Well, 0.3 grams of BP may still be a bit much, but this was more successful than the last one, for sure. I remembered to use slo-mo and point the camera correctly this time:
View attachment IMG_9665.mov
Unfortunately, it wasn't perfect; the nosecone ejection piston got a little jammed into the top of the chute cannon:
View attachment IMG_9665.mov
Unfortunately, it wasn't perfect; the nosecone ejection piston got a little jammed into the top of the chute cannon:
Attachments
I reset the nosecone ejection piston and test-fired the main chute:
View attachment IMG_9669.mov
If you're wondering, "how is the nosecone piston attached", this is what I was wondering myself about 10 seconds after firing the main chute.
You can see it getting fired off into the tree. It's a really big blue spruce, and the rocket was lined up with the trunk, so I don't think it went across the street, but... I haven't found it yet.
At least the main chute didn't get any more damage than it had from yesterday, so the chute cannon is working correctly. It wouldn't hurt to cut back a little on the size of that charge, also. These small pistons are really effective.
Update: I found the nosecone ejector piston under one of the blue spruce branches, good as new. I just need to attach a leash to it.
I think I should make some improvements to the end of the chute cannon and the nosecone ejector to keep it from getting wedged into the end of the chute cannon. Mostly I think I just need to glue on a larger, thicker disc at the bottom of the nosecone ejector piston.
View attachment IMG_9669.mov
If you're wondering, "how is the nosecone piston attached", this is what I was wondering myself about 10 seconds after firing the main chute.
You can see it getting fired off into the tree. It's a really big blue spruce, and the rocket was lined up with the trunk, so I don't think it went across the street, but... I haven't found it yet.
At least the main chute didn't get any more damage than it had from yesterday, so the chute cannon is working correctly. It wouldn't hurt to cut back a little on the size of that charge, also. These small pistons are really effective.
Update: I found the nosecone ejector piston under one of the blue spruce branches, good as new. I just need to attach a leash to it.
I think I should make some improvements to the end of the chute cannon and the nosecone ejector to keep it from getting wedged into the end of the chute cannon. Mostly I think I just need to glue on a larger, thicker disc at the bottom of the nosecone ejector piston.
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Yesterday I worked on fixing up the outer surface of the nosecone. I sanded off all the high spots,
coated it with epoxy, put it into the mold, and then vacuum bagged the mold, with the idea that the vacuum would push the nosecone into the mold and pull out bubbles. What happened instead was the low pressure caused all of the trapped air in the epoxy to expand and make a sort of foam:
Oof. That's ugly.
This morning I sanded all that back off:
I was tempted to just start manually coating it with epoxy from here, but I wanted to give one last chance for the mold to give it the mathematically correct VK shape. This time I mixed up 46 grams of epoxy and then dug out a vacuum bell jar, and used it to de-gas the epoxy. The epoxy foamed right up inside the bell jar, and some of the bubbles popped, but sadly there was still quite a bit of foam on top when I decided I didn't want to lose any more of my pot life and I let air back in. The bubbles promptly went back down to near-invisibility. The high viscosity of this Cotronics 4461 epoxy (500 F) is definitely a downside. In contrast, the Cotronics 4460 (600 F) epoxy runs almost like water when you heat it up, which causes its own issues, besides the issue that you have to get it up to about 200F before it starts curing.
But I'm giving it a shot. I poured about 3/4 of the epoxy into the silicone mold, wiped on the rest on the outside of the NC, doing my best to work it into all the pockets, and then shoved it in. Because of the cylindrical section of my nosecone, there's no avoiding trapping a bunch of air in there at first. But I pushed the part in hard enough to get a lot of epoxy to run out, and squeezed the outside of the silicone mold up from the bottom. I put the mold back into its FG liner (which keeps it straight), again squeezing up from the tip as it went in, so there's some chance I'll get the result I'm looking for. I seem to recall having success when I used the mold like this about 10 years ago, but I don't remember the details. It's currently sitting tip side up with weight of the mold pushing the nosecone in farther. I'm going to let it cure at room temperature all day today and cross my fingers when it comes out. Worst case, I'll just have to do some more sanding and manual finishing. I'm hoping that there are only a few bubbles and I can trust that most of the cone has the mold's shape.
coated it with epoxy, put it into the mold, and then vacuum bagged the mold, with the idea that the vacuum would push the nosecone into the mold and pull out bubbles. What happened instead was the low pressure caused all of the trapped air in the epoxy to expand and make a sort of foam:
Oof. That's ugly.
This morning I sanded all that back off:
I was tempted to just start manually coating it with epoxy from here, but I wanted to give one last chance for the mold to give it the mathematically correct VK shape. This time I mixed up 46 grams of epoxy and then dug out a vacuum bell jar, and used it to de-gas the epoxy. The epoxy foamed right up inside the bell jar, and some of the bubbles popped, but sadly there was still quite a bit of foam on top when I decided I didn't want to lose any more of my pot life and I let air back in. The bubbles promptly went back down to near-invisibility. The high viscosity of this Cotronics 4461 epoxy (500 F) is definitely a downside. In contrast, the Cotronics 4460 (600 F) epoxy runs almost like water when you heat it up, which causes its own issues, besides the issue that you have to get it up to about 200F before it starts curing.
But I'm giving it a shot. I poured about 3/4 of the epoxy into the silicone mold, wiped on the rest on the outside of the NC, doing my best to work it into all the pockets, and then shoved it in. Because of the cylindrical section of my nosecone, there's no avoiding trapping a bunch of air in there at first. But I pushed the part in hard enough to get a lot of epoxy to run out, and squeezed the outside of the silicone mold up from the bottom. I put the mold back into its FG liner (which keeps it straight), again squeezing up from the tip as it went in, so there's some chance I'll get the result I'm looking for. I seem to recall having success when I used the mold like this about 10 years ago, but I don't remember the details. It's currently sitting tip side up with weight of the mold pushing the nosecone in farther. I'm going to let it cure at room temperature all day today and cross my fingers when it comes out. Worst case, I'll just have to do some more sanding and manual finishing. I'm hoping that there are only a few bubbles and I can trust that most of the cone has the mold's shape.
I pulled out the nosecone last night and it was satisfyingly shiny, with full contact with the mold and almost no bubbles. I think degassing the epoxy really helped.
Just one bubble visible in this one:
The tip is cast epoxy/tungsten. The lighter gray areas behind that are where the carbon fiber didn't have contact with the mold in the initial layup and I filled it with colloidal-thickened epoxy. The fiberglass section looks ugly but it's smooth and solid.
It feels good to have the sustainer basically done for the test flight next weekend. I think I'll do the post-cure heat treatment today or tomorrow. Between the test flight and Balls, I'm going to sand and paint the whole sustainer with the Cotronics 1200F stainless steel paint.
Just one bubble visible in this one:
The tip is cast epoxy/tungsten. The lighter gray areas behind that are where the carbon fiber didn't have contact with the mold in the initial layup and I filled it with colloidal-thickened epoxy. The fiberglass section looks ugly but it's smooth and solid.
It feels good to have the sustainer basically done for the test flight next weekend. I think I'll do the post-cure heat treatment today or tomorrow. Between the test flight and Balls, I'm going to sand and paint the whole sustainer with the Cotronics 1200F stainless steel paint.
GrouchoDuke
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That's pretty. Looks fast!
Today I worked on the second stage. I drilled the Loki forward closure sideways to install a 1.5” long female threaded spacer that will anchor the front of the motor to the airframe and also to the second stage deployment spacer in the photos below.
This deployment spacer has the airstart arm screw switch and a connector to the av-bay, and holds the deployment charge and deployment harness. The 2nd stage av-bay is trapped between this fixed deployment spacer and the sustainer motor, and gets deployed with the parachute at apogee. It has a Blue Raven and a Featherweight GPS tracker in a 2” long section just like in the sustainer. I’ll make another av-bay/chute holder/motor spacer for the booster starting tomorrow and it will be more clear from those photos how it will work.
Below is a better look at the bulkhead that will stay attached to the 2nd stage av-bay, which uses a stock Featherweight 38mm active bulkhead.
I’m using a simple 2-pin header connector for the connection to the fixed spacer that is attached to the motor.
Today I drilled the airframe for the fixed deployment spacer and figured out how much of the 2nd stage motor (k627) will stick out the back end. A lot, 9.2”. That makes the booster longer, now 42”. The total rocket length went up to 104”. I think the entire sustainer will now stick out of the top of the 6’ tower.
I’m shooting for flying the whole 3-stage stack with a dummy motor in the 2nd stage this weekend. The booster will be an H999 or I299 to get 50-60 Gs out of the tower, just like the Bslls flight. I don’t think there will be a problem with the tower or the initial stability, but if there is I want to know sooner rather than later.
This deployment spacer has the airstart arm screw switch and a connector to the av-bay, and holds the deployment charge and deployment harness. The 2nd stage av-bay is trapped between this fixed deployment spacer and the sustainer motor, and gets deployed with the parachute at apogee. It has a Blue Raven and a Featherweight GPS tracker in a 2” long section just like in the sustainer. I’ll make another av-bay/chute holder/motor spacer for the booster starting tomorrow and it will be more clear from those photos how it will work.
Below is a better look at the bulkhead that will stay attached to the 2nd stage av-bay, which uses a stock Featherweight 38mm active bulkhead.
I’m using a simple 2-pin header connector for the connection to the fixed spacer that is attached to the motor.
Today I drilled the airframe for the fixed deployment spacer and figured out how much of the 2nd stage motor (k627) will stick out the back end. A lot, 9.2”. That makes the booster longer, now 42”. The total rocket length went up to 104”. I think the entire sustainer will now stick out of the top of the 6’ tower.
I’m shooting for flying the whole 3-stage stack with a dummy motor in the 2nd stage this weekend. The booster will be an H999 or I299 to get 50-60 Gs out of the tower, just like the Bslls flight. I don’t think there will be a problem with the tower or the initial stability, but if there is I want to know sooner rather than later.
The booster build was uneventful. I have some mostly-unidirectional carbon fiber plate for the fin stock. On Monday I cut out the fins on my tile saw, clamped them together, sanded the perimeter identical for the 3 fins, rounded the edges on the belt sander, and then used a foam core jig to glue them on. Tuesday I used the 810 epoxy from Soller, mixed with West colloidal silica for the fillets. The didn't come out very smooth, but I'm o.k. with that. The booster will be part of the flight for less than 1 second.
Yesterday I completed the av-bay wiring and final mods for the av-bays in the booster and the second stage, and then cut and tied Kevlar harness everywhere.
This morning after measuring 3 times, I cut the booster tube to the final length, and put the whole thing together. This is a crazy long rocket!
Today I'm going to figure out exactly what I want to do for motors, spacers and filler weight so I can fly it on Monday in Alamosa within the 15,000 foot waiver. All 3 stages will fly, separate, and hopefully be recovered in 1 piece (well, 3 pieces). One goal is to boost it with flight-like acceleration so I can confirm it will start out straight coming out of the 6' tower. For that, I'm going to boost it with either an I-1299 or H-999. The second stage will have a Loki case for structure. Another goal is to get the stability margins similar to the big flight. I'd also like to get the sustainer supersonic, and test out the ignition logic and a head-end ignitor (without motor) in the second stage.
I haven't post-cured the nosecone yet, so I think I'll get that going while I spend some quality time with Open Rocket and RasAero to finish the plan for this test flight.
Yesterday I completed the av-bay wiring and final mods for the av-bays in the booster and the second stage, and then cut and tied Kevlar harness everywhere.
This morning after measuring 3 times, I cut the booster tube to the final length, and put the whole thing together. This is a crazy long rocket!
Today I'm going to figure out exactly what I want to do for motors, spacers and filler weight so I can fly it on Monday in Alamosa within the 15,000 foot waiver. All 3 stages will fly, separate, and hopefully be recovered in 1 piece (well, 3 pieces). One goal is to boost it with flight-like acceleration so I can confirm it will start out straight coming out of the 6' tower. For that, I'm going to boost it with either an I-1299 or H-999. The second stage will have a Loki case for structure. Another goal is to get the stability margins similar to the big flight. I'd also like to get the sustainer supersonic, and test out the ignition logic and a head-end ignitor (without motor) in the second stage.
I haven't post-cured the nosecone yet, so I think I'll get that going while I spend some quality time with Open Rocket and RasAero to finish the plan for this test flight.
Bad news on the post-curing of the nosecone. The data sheet for the epoxy calls for 1 hour at 250F and 1 hour at 350F.
I increased the temperature gradually, but when I got somewhere above 250F on the way to 350F, the sleeve over the cast tungsten/epoxy portion split. I think it was just a matter of the coefficient of thermal expansion (CTE) of the tungsten/epoxy being higher than that of the carbon sleeve composite, and it just burst. Unfortunately, it looks like the damage is more than cosmetic and the tip is now a little off-center. I think I'm going to have to start over on this for at least the Balls shot.
For the next version I should reduce the overlap between the carbon sleeve and cast section and/or do the post-curing before casting the tip.
I increased the temperature gradually, but when I got somewhere above 250F on the way to 350F, the sleeve over the cast tungsten/epoxy portion split. I think it was just a matter of the coefficient of thermal expansion (CTE) of the tungsten/epoxy being higher than that of the carbon sleeve composite, and it just burst. Unfortunately, it looks like the damage is more than cosmetic and the tip is now a little off-center. I think I'm going to have to start over on this for at least the Balls shot.
For the next version I should reduce the overlap between the carbon sleeve and cast section and/or do the post-curing before casting the tip.
Upon further review, the tip is still centered, and there's still about 1" of overlap between the intact carbon and the cast noseweight. In other words, the nosecone is still structurally sound and safe to fly this weekend.
Once the tip cooled back down to room temperature, the split closed back up on its own:
If I make another nosecone, I think I'll post-cure the skin before casting the tip, and then cast the tip at a somewhat elevated temperature, maybe 140 F, trying to match what its bulk temperature might be in flight when the skin gets hot.
Once the tip cooled back down to room temperature, the split closed back up on its own:
If I make another nosecone, I think I'll post-cure the skin before casting the tip, and then cast the tip at a somewhat elevated temperature, maybe 140 F, trying to match what its bulk temperature might be in flight when the skin gets hot.
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As for the test flight attempt last weekend, I'm not sure why I thought this, but I thought that the 2-day launch in the 3-day weekend was Sunday and Labor Day. Not so, so I missed my last opportunity for a test flight before BALLS. I figured out my mistake before I started driving on Sunday night, at least, but it was a combination of a disappointment and relief that the test flight didn't happen. I got the rocket pretty much ready, which was most of the point of prepping for that launch. Now I'm doing the rest of the tasks. Today is prepping the motors and the head-end igniters.
One change to my plan is to swap out the CTI IMAX J530 sustainer motor for a J150 CTI Mellow Yellow longburn. This is mostly to avoid accidentally going over 100,000 feet. With high-drag assumptions consistent with aero damage, the flight sims under 100k with the J530, but under less-conservative assumptions it could have gone over 100k, and I don't want to tick off the launch organizers since I'm not flying as a class 3 flight. With the J150 in the sustainer it's almost certainly not going over 100k. It also has the advantage of reducing the peak aeroheating of the sustainer, so there's a better chance of getting it back un-damaged. When I was first considering motors, I avoided the J150 because I thought it must be an endburner since it such a long burn time, and I'm only set up for head-end ignition in the upper 2 stages. But it's a core burner, and now it seems like a great fit, with pellet ignition and a max velocity of about Mach 2.6.
One change to my plan is to swap out the CTI IMAX J530 sustainer motor for a J150 CTI Mellow Yellow longburn. This is mostly to avoid accidentally going over 100,000 feet. With high-drag assumptions consistent with aero damage, the flight sims under 100k with the J530, but under less-conservative assumptions it could have gone over 100k, and I don't want to tick off the launch organizers since I'm not flying as a class 3 flight. With the J150 in the sustainer it's almost certainly not going over 100k. It also has the advantage of reducing the peak aeroheating of the sustainer, so there's a better chance of getting it back un-damaged. When I was first considering motors, I avoided the J150 because I thought it must be an endburner since it such a long burn time, and I'm only set up for head-end ignition in the upper 2 stages. But it's a core burner, and now it seems like a great fit, with pellet ignition and a max velocity of about Mach 2.6.
Some photos from this morning:
Grains taped together:
Loki delay element scraped clean on the inside. The delay material burns away, and we don't want that.
Forward closure greased and delay sleeve inserted. Note all the o-rings. The wire is AWG 22 magnet wire. I might have preferred 26 or 28, because I'm trying to minimize the heating of the epoxy with the wire, but the next easily-available size was AWG30 and IMO that's just too fragile.
In the past I have had a problem with the superhot motor gas melting through regular wire insulation and then sneaking along where the the wire goes to get out. I fixed this in later head-end-ignition attempts by stripping the wire where it gets potted. In this attempt I'm using the higher-temperature and thinner magnet wire insulation, along with some coils, to hopefully do the same thing with hopefully a little more margin and no chance of accidental shorts.
Here's what a CTI forward closure looks like if you just pot the wires into a hole drilled into the delay grain (my first failed airstart attempt from ~2011). In that case the 2nd stage blew out the sustainer and the avionics forward of the motor not long after ignition. I think the avionics got destroyed IIRC, and the 2nd stage broke a fin. The sustainer landed on its chute with a full motor and was basically o.k. The problem was that the wires acted as an ignition source for the delay to burn through to the end almost immediately:
Here I dug out the delay material from a new CTI forward closure and it's ready for potting the feed-through wires.
Here are the two HEI bulkheads before potting the wires:
And here hare the two Loki motors with grains glued into the liner per the detailed Loki instructions, and the two HEI forward closures full of high-temp epoxy:
I'm getting some epoxy leaking through where the wires go through the touch hole, and I'm wishing I had added some colloidal silica to thicken up the epoxy, at least at the forward end.
I also used this batch of high-temperature epoxy to repair the split in the nosecone as best as I could. I let the NC soak in the oven at 175F for a couple of hours to try to get the split to gently open up, but if it did, it was very subtle. I worked more of the Cotronics epoxy into the split area and wiped off the excess.
Grains taped together:
Loki delay element scraped clean on the inside. The delay material burns away, and we don't want that.
Forward closure greased and delay sleeve inserted. Note all the o-rings. The wire is AWG 22 magnet wire. I might have preferred 26 or 28, because I'm trying to minimize the heating of the epoxy with the wire, but the next easily-available size was AWG30 and IMO that's just too fragile.
In the past I have had a problem with the superhot motor gas melting through regular wire insulation and then sneaking along where the the wire goes to get out. I fixed this in later head-end-ignition attempts by stripping the wire where it gets potted. In this attempt I'm using the higher-temperature and thinner magnet wire insulation, along with some coils, to hopefully do the same thing with hopefully a little more margin and no chance of accidental shorts.
Here's what a CTI forward closure looks like if you just pot the wires into a hole drilled into the delay grain (my first failed airstart attempt from ~2011). In that case the 2nd stage blew out the sustainer and the avionics forward of the motor not long after ignition. I think the avionics got destroyed IIRC, and the 2nd stage broke a fin. The sustainer landed on its chute with a full motor and was basically o.k. The problem was that the wires acted as an ignition source for the delay to burn through to the end almost immediately:
Here I dug out the delay material from a new CTI forward closure and it's ready for potting the feed-through wires.
Here are the two HEI bulkheads before potting the wires:
And here hare the two Loki motors with grains glued into the liner per the detailed Loki instructions, and the two HEI forward closures full of high-temp epoxy:
I'm getting some epoxy leaking through where the wires go through the touch hole, and I'm wishing I had added some colloidal silica to thicken up the epoxy, at least at the forward end.
I also used this batch of high-temperature epoxy to repair the split in the nosecone as best as I could. I let the NC soak in the oven at 175F for a couple of hours to try to get the split to gently open up, but if it did, it was very subtle. I worked more of the Cotronics epoxy into the split area and wiped off the excess.
LithosphereRocketry
Pining for the Fjords
- Joined
- Feb 19, 2017
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Question - is HEI allowed for record attempts? The Tripoli rules say "no modification to certified motor hardware," which seems to imply no HEI (as afaik HEI is considered experimental) but doesn't say it explicitly.
heada
Well-Known Member
Loki has instructions detailing how to do HEI on Loki reloads. That's as close as you can get for Manufacturer approval.
https://lokiresearch.com/images/Documents/Headend Instructions 2.docx
Yesterday was about finishing the sustainer.
I sanded off all the previous high-temperature finish experiments off of the fins, and sanded everything else down too, before applying an all-over coat of the Cotronics 4461 epoxy. I cured it at 175 in the kitchen oven so I could keep going. Here's how it came out, glossy but kinda gloppy:
Lots more sanding with 150 grit dry for shaping, then 360 grit wet. Back into the oven for drying and further curing. Interestingly, when it came out the surface was a little rougher. But when I re-read the directions for the paint it recommended roughing the surface, so I didn't re-sand. Here's the last look before it all got covered over:
The paint is the Cotronics stainless steel 1200F paint, which did great when I used it for a high-speed test on one of the fins 10 years ago, and which seemed good when I painted a tube for radio transmission experiment a few weeks ago. As a bonus, I think it looks sharp, too:
The paint instructions recommend doing a post-cure at 400F for 15 minutes. I'm a little hesitant in case something goes wrong, and because I don't really want to stink up the kitchen (I made a rocketry oven 10 years ago that I have been dragging across the country, but I haven't put it back together). I think 15 minutes is short enough that the cast tungsten-epoxy won't get hot enough to expand and split the surface again. Maybe I'll do 400F for 5-10 minutes just to be sure.
My other goal for today is to do a complete assembly as if I'm getting ready to launch, and take final weights and measurements. I might also do a check of the deployment charge sizing for ejecting the 1st or 2nd stage av-bays if I feel up to it (recovering from side effects of Omicron booster). Due to some personal travel this is the last real prep day I have before packing up for BALLS.
I sanded off all the previous high-temperature finish experiments off of the fins, and sanded everything else down too, before applying an all-over coat of the Cotronics 4461 epoxy. I cured it at 175 in the kitchen oven so I could keep going. Here's how it came out, glossy but kinda gloppy:
Lots more sanding with 150 grit dry for shaping, then 360 grit wet. Back into the oven for drying and further curing. Interestingly, when it came out the surface was a little rougher. But when I re-read the directions for the paint it recommended roughing the surface, so I didn't re-sand. Here's the last look before it all got covered over:
The paint is the Cotronics stainless steel 1200F paint, which did great when I used it for a high-speed test on one of the fins 10 years ago, and which seemed good when I painted a tube for radio transmission experiment a few weeks ago. As a bonus, I think it looks sharp, too:
The paint instructions recommend doing a post-cure at 400F for 15 minutes. I'm a little hesitant in case something goes wrong, and because I don't really want to stink up the kitchen (I made a rocketry oven 10 years ago that I have been dragging across the country, but I haven't put it back together). I think 15 minutes is short enough that the cast tungsten-epoxy won't get hot enough to expand and split the surface again. Maybe I'll do 400F for 5-10 minutes just to be sure.
My other goal for today is to do a complete assembly as if I'm getting ready to launch, and take final weights and measurements. I might also do a check of the deployment charge sizing for ejecting the 1st or 2nd stage av-bays if I feel up to it (recovering from side effects of Omicron booster). Due to some personal travel this is the last real prep day I have before packing up for BALLS.
