Another silly multistage project

[LithosphereRocketry]

So with my Black Brant waiting for a field, what better time to start another project?

One of my longtime ambitions has been to get on the Tripoli records leaderboard, and with single-stage being very optimized these days, I figured multistage would be a better place to set my sights. I'm not necessarily expecting to set any records with this particular project, but I might as well see how close I can get. The plan is to go for the Complex J category, with a full I booster and baby J sustainer; Loki's 38/740 and 38/480 cases line up nicely for this, and no HAZMAT is a big plus.


RASAero is very optimistic about my altitude, consistently predicting a few hundred feet above OpenRocket even with OR's most generous presets:



Besides the record-chasing, this build will also be a testbed for Mach lockout methods on my homebrew flight computers since right now I don't have a rocket that can maintain that kind of speed for more than a second or two.

More to come!

Edit: forgot to attach OR/RAS files

 

[LithosphereRocketry]

Starting work on a CAD model of the rocket. Next is the first scary step: trying to fit everything in the avbay.

 

[LitmusAero]

So with my Black Brant waiting for a field, what better time to start another project?

One of my longtime ambitions has been to get on the Tripoli records leaderboard, and with single-stage being very optimized these days, I figured multistage would be a better place to set my sights. I'm not necessarily expecting to set any records with this particular project, but I might as well see how close I can get. The plan is to go for the Complex J category, with a full I booster and baby J sustainer; Loki's 38/740 and 38/480 cases line up nicely for this, and no HAZMAT is a big plus.
View attachment 527080

RASAero is very optimistic about my altitude, consistently predicting a few hundred feet above OpenRocket even with OR's most generous presets:
View attachment 527081
View attachment 527082

Besides the record-chasing, this build will also be a testbed for Mach lockout methods on my homebrew flight computers since right now I don't have a rocket that can maintain that kind of speed for more than a second or two.

More to come!

Edit: forgot to attach OR/RAS files

Cool! I didn't know you could change altitude units in openrocket, how do you do that?

 

[waltr]

Cool! I didn't know you could change altitude units in openrocket, how do you do that?

Edit/Preferences/Units to change globally.

 

[LithosphereRocketry]

Minor updates going on- since my current shop is a college facility, I haven't had easy access to it over the summer.

I ordered some flush-mount speaker wire to play around with. I saw this recommended somewhere on the forum -- I want to say from Jim Jarvis but I could be totally wrong.

I was hoping (a little optimistically) that the backing adhesive would be conductive so I can just wrap it around the igniter. Alas, it is not. The tape is actually made of a stack of smooth plastic->double sided tape->copper->double sided tape, which makes it a bit of a pain to get at the underlying copper layer. My best solution was to cut away the top layer, clean up the adhesive with a liberal helping of isopropanol, and then sand away the tape to get a nice solderable copper surface. This worked fine but is quite labor intensive: I estimated 5-10 mins of work per connection. My next step is probably going to be trying out a stronger solvent like acetone; however, I don't have that on hand to try. The official way to use this tape is with an insulation-displacement connector that stabs pins through all four layers, but they're bulky and expensive so I'd like to avoid that.

 

[JimJarvis50]

The stuff I use is called Taperwire. I remove the thicker top wear layer and replace it with celophane tape that is thinner. It is possible to peel away the adhesive layer if you are very carefull. It does take a bit of alcohol or acetone as a final cleanup. It's a bit of a learning process to get a procedure that works, but it can be done. The wire I use is 424-WT/CL/BLK

Jim

 

[LithosphereRocketry]

The stuff I use is called Taperwire. I remove the thicker top wear layer and replace it with celophane tape that is thinner. It is possible to peel away the adhesive layer if you are very carefull. It does take a bit of alcohol or acetone as a final cleanup. It's a bit of a learning process to get a procedure that works, but it can be done. The wire I use is 424-WT/CL/BLK

Jim

Thank you for the advice!

How reasonable do you think it would be to make something like the original insulation-cutting connectors? I'm now thinking about doing something like a couple screws on conductive inserts through the top of the tape.

In other news, I'm now thinking this is probably going to become a single-deploy build, as it's much easier to deal with stage wiring if I don't have to worry about breaking the connection between the avbay and the lower airframe. New design to come soon- hopefully it stays in waiver with the lost weight.

 

[Charles_McG]

I've also used the ghost wire in a sustainer with limited space . I also cleaned it up and soldered to it. I had originally left a small amount extending beyond the end of the body tube, but it broke with repeated flexing, and I had to re-solder further up. Luckily I've only got one more flight for that Recruit planned, and I'm not quite ready for the Talos Terrier Recruit.

I was also concerned about the heat resistant of the wire backing in the region where ejection charges would be going off, so I covered it with a strip of aluminum tape.

 

[JimJarvis50]

Thank you for the advice!

How reasonable do you think it would be to make something like the original insulation-cutting connectors? I'm now thinking about doing something like a couple screws on conductive inserts through the top of the tape.

In other news, I'm now thinking this is probably going to become a single-deploy build, as it's much easier to deal with stage wiring if I don't have to worry about breaking the connection between the avbay and the lower airframe. New design to come soon- hopefully it stays in waiver with the lost weight.

I"m not sure what you're asking (i.e., conductive inserts). I think I would need some pictures, perhaps. I can say that the wires above and below the motor are relatively fragile. I try to protect them.

Regarding the staging wiring, I just run wires from the avbay through the drogue section to the top of a zipperless coupler. At the zipperless coupler, I use a couple of Dean's Plugs as a reakwire. It's easy to connect them when putting the sections of the air frame together, and then they come apart eaily when the sections separate. I tpically file the little prongs just a touch so that I get the separation force that I want. It's quite easy to do. A pic or two showing the above are attached.

Jim

 

[cerving]

For the igniter breakwire, I've simply ran the wires through the bulkhead with tinned ends, and wrapped the end of the igniter wire (or an extension if the wire isn't long enough) around the tinned ends... twice works well. I use a piece of 1/8" launch lug to insulate the connection, and tape them to the bulkhead-side wire.

 

[LithosphereRocketry]

Encountered a slight potential issue: turns out 38mm fiberglass couplers are almost comically thick. I was hoping to mount my 1.4" wide custom altimeter in the coupler... turns out the inner diameter is 1.37". Whoops...

I can use something like an EasyMini for this build, but I'd really like to have tilt lockout if possible. Guess I just have to get working on a more compact altimeter

 

[cerving]

You can put a Proton in a 38mm coupler... I've done it. Yes, they ARE thick...

 

[LithosphereRocketry]

You can put a Proton in a 38mm coupler... I've done it. Yes, they ARE thick...

That's definitely an option - if possible I'd like to have true tilt sensing for peace of mind, but accel/baro lockout would probably be just as good.

 

[G_T]

For that thickness difference, perhaps take a dowel and wrap sandpaper... Do it outside. Or a small flap or drum sander or hone and a hand drill.

Gerald

 

[LithosphereRocketry]

You can put a Proton in a 38mm coupler... I've done it. Yes, they ARE thick...

Do you have any pictures of your setup for this?

 

[LithosphereRocketry]

For that thickness difference, perhaps take a dowel and wrap sandpaper... Do it outside. Or a small flap or drum sander or hone and a hand drill.

Gerald

Unfortunately the circuits skirt pretty close to the edge of the board, so I don't think I could do that without damaging something.

 

[Charles_McG]

Here’s a Proton inside the coupler of a WildChild I modified into a Recruit sounding rocket. And an Eggfinder Mini in the nosecone.

 

[cerving]

That's pretty similar to mine. The Proton sits on a little basswood sled, the 300 mAH Lipo tucks into the other side of the sled. The two #10 allthreads lay against the bottom of the sled with the battery between them.

 

[Charles_McG]

I printed the endcaps and ran a kevlar line through the coupler next to the battery to take the force.

 

[cerving]

I printed the endcaps and ran a kevlar line through the coupler next to the battery to take the force.

Good idea!

 

[rocketgeek101]

Here’s a Proton inside the coupler of a WildChild I modified into a Recruit sounding rocket. And an Eggfinder Mini in the nosecone.
View attachment 538503View attachment 538504View attachment 538505View attachment 538506View attachment 538507View attachment 538508View attachment 538509View attachment 538510View attachment 538511

How is the nosecone attached to the Eggfinder mount? Is the green ring glued into the NC shoulder?

 

[Charles_McG]

How is the nosecone attached to the Eggfinder mount? Is the green ring glued into the NC shoulder?

Yes, the green adapter is epoxied into the shoulder of the nosecone. It has inside threads. I printed a version of the white holder - which matches the dimensions of the Estes 18-24mm motor adapter, and holds a Quark or a Mini quite nicely - with tabs that match the threads. I added a pair of holes that I can put the tips of needlenose pliers in and twist the mount into the threads. The power and battery leads poke out the end.

 

[LithosphereRocketry]

Forgot to post this, but update on the wire tape: it looks like the stuff I have will fit:

This is with Wildman tube instead of the Composite Warehouse stuff I'll be using for this project, but I'm assuming the mandrel size is similar.

In other news, I've once again waffled on my electronics choice. I was pretty unhappy with not having tilt lockout, and testing electronics is a major goal of this project, so I sat down for a couple hours and redesigned my altimeter board to fit:

It's the exact same schematic plus a spare output channel, just using more SMD parts to shrink it down- the whole board is about 1" by 3". Still to be determined if I end up flying it, as it might be better to have a commercial backup for deployment at least- maybe I'll try to jam an EasyMini into the nose somehow. We'll see how it goes. I'm still waiting on the airframe parts, so I've got some time to test things and decide.

 

[LithosphereRocketry]

Forgot to post this somehow: I also redesigned the rocket slightly for single-break deployment with JLCR so that I could avoid breakwires:


I'll likely replace the massive eyebolt in the nose with a tie-down U-bolt similar to the Additive Aerospace ones.

In other news, I need to figure out whether it's realistic to use the Crossfire24 parachute I originally planned for the sustainer or whether I'll have to downgrade to a traditional MPR-style chute- I was really hoping for the extra durability but it's quite bulky compared to what I'm used to in this size.

 

[waltr]

What Baro and Accel modules are you using? PCB footprints look like the Adafruit ones but a bit smaller.

 

[LithosphereRocketry]

What Baro and Accel modules are you using? PCB footprints look like the Adafruit ones but a bit smaller.

I'm using the generic no-name MPU6050 and BMP280 modules from your choice of large online retailer- the MPU6050 isn't ideal for this as it's limited to 16G but it works well enough.

 

[waltr]

Ok, thanks.
I use both sensors on Adafruit breakouts for a data logger. Just doing post analysis to learn the math.

 

[LithosphereRocketry]

Some updates-

Since this project needs to be done by this winter, I was getting sick of waiting for Composite Warehouse, so I cancelled my order and ordered replacements from Wildman. For some reason I had thought that Wildman's 38mm tube was sized to 1.63" meaning that this would be a pretty major weight penalty, but apparently I never actually checked- I went to measure a piece and it turns out they are indeed the smaller 1.60" size. Perfect!

I got my fly-away rail guides and found them to be a bit loose. I was originally planning on shimming with rubber bands, but I found some foam tape lying around the shop that worked perfectly:


Test fits on a piece of LOC tubing felt pretty snug with the foam compressing nicely - that's 1.63" OD so I'll probably need to add another layer for the slimmer Wildman tube. Unfortunately, the piece of Wildman tube I have right now is a motor mount and not quite long enough to fit comfortably in the guide.

I was hoping that I'd be able to get away with a Crossfire 24" chute in the sustainer for a bit of extra ruggedness, but upon receiving the parachute it was clear that wasn't going to happen:


A regular TopFlight 24" chute fits fine, although I did have to stretch the sustainer ever-so-slightly based on my tested packing volume.

Flight computer boards arrived:

To be continued...

 

[Joekeyo]

Some updates-

Since this project needs to be done by this winter, I was getting sick of waiting for Composite Warehouse, so I cancelled my order and ordered replacements from Wildman. For some reason I had thought that Wildman's 38mm tube was sized to 1.63" meaning that this would be a pretty major weight penalty, but apparently I never actually checked- I went to measure a piece and it turns out they are indeed the smaller 1.60" size. Perfect!

I got my fly-away rail guides and found them to be a bit loose. I was originally planning on shimming with rubber bands, but I found some foam tape lying around the shop that worked perfectly:
View attachment 543655

Test fits on a piece of LOC tubing felt pretty snug with the foam compressing nicely - that's 1.63" OD so I'll probably need to add another layer for the slimmer Wildman tube. Unfortunately, the piece of Wildman tube I have right now is a motor mount and not quite long enough to fit comfortably in the guide.

I was hoping that I'd be able to get away with a Crossfire 24" chute in the sustainer for a bit of extra ruggedness, but upon receiving the parachute it was clear that wasn't going to happen:
View attachment 543658

A regular TopFlight 24" chute fits fine, although I did have to stretch the sustainer ever-so-slightly based on my tested packing volume.

Flight computer boards arrived:
View attachment 543660
To be continued...

Even one of those looks like a big pile of work to me. I call it "ship in the bottle" craftsmanship. Good luck bro.