With a little help from my friends: 2-stage 54mm min diameter

[rocketace]

Time to get high with a little help from my friends!

I have had a lot of fun with extreme flights with 38mm motors and now I am ready for a new challenge. I am in beginning design stage of a 54mm to 54mm 2 stage rocket that will be all minimum diameter. I have been doing a lot of research on current and past extreme projects from all you fine/crazy people. I am working on this project with a buddy of mine, but I want to document as much as I can here so yall can pick apart everything to find potential areas we over looked.

Goal:
First and foremost…safety.
After that…To get as high as possible with a 54mm motors in a 2 stage. But no Loki, sadly just not in the budget for this build.

Design-Overall:
The design is far from finalized, but after bouncing around dozens of configurations. The below is my current top ideas.

Airframe:
Current plan is 4-5layers (trying to match the tail cone diameter) of CF 3k Twill with 820 epoxy from sollercomposites.com. Mandrel will be a Blue Tube full length coupler. Since we will be using tape wire for sustainer ignition and possibly booster separation, some test layups will be done to figure out what ID we will need.

Nose cone:
Keeping it simple here by just using a Wildman FG nosecone. I will be adding a sled at the top for a GPS tracker.

Fins:
1/8” FG attached with RocketPoxy. Tip to tip is still TBD. I don’t think it will be needed for the flight profile, but it would be nice to have so I don’t have to worry if it has a hard landing. However, the current design has the sustainer OD airframe as the coupler which complicates things for tip-2-tip. A partial tip-2-tip is possible as well.

Recovery set up:
This is the main focus at the moment. So many design choices! I am highly leaning towards single recovery bay for each stage with the main held closed by a cable cutter. The ISC would be the nose cone of the booster. However, a 2 bay design isn’t ruled out yet nor is a chute cannon….

Recovery gear:
Most parts from Top Flight. Harness will be 1/8” TK, Main chutes planned to be 40” but not sure if I want to do 1.7oz or 1.1oz yet. Drogue or drogue-less has not been decided but I am leaning towards using a drogue. Booster drogue would be a standard 12” X-type and sustainer I am thinking a 12” Ultra-X-Type. Sizes are not finalized and any recommendations would be appreciated, especially if you have any data on decent rates for a rocket around 5lbs after burnout.

Electronics:
This is the second focus as the moment. There is no easy place to put the electronics, especially in the sustainer. If I put the altimeters just above the motor we will have to figure out if we can still arm wirelessly (like a slot antenna in one of Jims posts). If it is not right above the motor then we have to figure out how to incorporate quick disconnects for the sustainer ignition wires. Anyway, below is the current planned electronics to be used. Information in the parenthesis will be the arming method.

Sustainer:
Featherweight GPS - Ttracker (Magnetic switch)
Split 4K – Camera (TBD )
Raven V4 – Airstart – Backup Apogee/Main – (Wifi for power and 2 Screw switch for shunt and short)
PerfectFlight SLCF –Primary Apogee/Main (Screw switch)…Now I just need to time it right to get one

Booster:
EggFinder GPS – Tacker (Magnetic switch)
Eggtimer Quantum – Separation – Backup Apogee/Main – (Wifi switch)
PerfectFlight MAWD – Primary Apogee/Main (Screw switch)

A few notes: I might switch out the PF MAWD to something else that is a smaller package. Also, LabRat Pull switches might replace some screw switches.

Interstage coupler:
The current design has a coupler that will be external to the airframes. This will add a bit of drag, but as long as the booster separates after it burns the drag penalty shouldn’t be too bad. The coupler will be FG so the tracker and wifi switch can operate. The sustainer fins will be ~2.5 from the bottom to leave room to slide it in the coupler.

Motors:
I currently have 2 AT-K250 and a CTI K300. I will be using those for the sustainer motors. I am crossing my fingers on the K300 casing holds together… For the booster I am thinking of using the AT 54-2800 motors. If I want to keep it in the L range I can use the L1090 with the K250 and the K1050 with the K300. After we fly it as high as possible, we might want to go as fast as possible! That motor combo is TBD.

Flight Tests:
Flight test 1 - Sustainer only) One of the K250s I will use as a sustainer only flight test. This will be to test the stability of the rocket, recovery sequence, as well as testing how long the K250 takes to pressurize with whatever igniter we decide to fly with. I am also contemplating doing a smaller initial shake down flight an a small J first.

Flight test 2 – Full stack wo/sustainer motor) Motor is TBD, but probably will be a big J or small K, but I want to mimic launch rail exit velocity as close as I can. This will test the full stack stability, separation, and recovery sequence. Also, this will demonstrate a safe recovery if sustainer doesn’t light.

Safety:
Using a shunt and a short for sustainer ignitor separate from other switches
Having an altitude and velocity check for sustainer ignition
Utilizing a wifi switch for arming Raven that will control sustainer ignition (aiming for no ladder)
Will be following a checklist and arming sequence to reduce hazards as much as possible
Test flights to prove stability, stage separation, recovery, and to check the checklists.

Of course at this point actual values, checklists, shunts, ect are all TBD. Much testing will be needed during this project.

Test rocket:
On top of all this I should mention I have yet to do any HPR two stage rockets. I have kept up with and looked at many 2+ stage flights on here over the past 10+ years and I believe I am ready for the challenge! Once the design (and before the construction) for the above rocket is complete I am planning on building a less extreme 2 stage that will use the same electronics, recovery, and staging configuration. I will use this rocket as my test bed to gain experience in the world of HPR 2 stage. Due to current on hand materials, I am planning for this rocket to be made out of thick walled 2.5” OD cardboard, 0.125-0.25” plywood fins, 3D printed nosecone, 38mm MMT in booster, 29mm MMT in the sustainer. This rocket will also have a few test flights before its first full 2 stage flight. This test rocket will be a big step and serve as a proof of concept and to validate that we are on the right track.



Initial Rocksim design:


Possible Sustainer configurations:

Possible Booster configurations:

Rejected ideas:

So...Feel free to follow along and please provide any input you may have!

 

[JimJarvis50]

Jason,

Looks like a very fun project. Come find me at the shootout and we can discuss. We'll need to talk about how Ravens are used for staging.

Jim

 

[rocketace]

Thanks Jim, sounds like a plan. I will see you at the shootout!

 

[jmuck78]

I'm considering my own 2 stage project, and I'm unclear on the separation scheme. Are you planning to use a separate black powder charge between the booster and sustainer to separate the two stages before you ignite the motor in the sustainer, or does the motor in the sustainer serve to separate the two stages?

 

[rocketace]

I'm considering my own 2 stage project, and I'm unclear on the separation scheme.

Hey Jason, I am planning on having a small separation charge that will fire when burnout is detected. This way the sustainer can coast for a bit without the drag form the booster.

 

[jmuck78]

Hey Jason, I am planning on having a small separation charge that will fire when burnout is detected. This way the sustainer can coast for a bit without the drag form the booster.

Great, thanks - good luck.

 

[RAHagen]

Hey Jason, this looks like an awesome build! Looking forward to watching the process!

Some first thoughts I thought were worth mentioning:

I wonder if you could integrate the tape wire into your composite layup? If you did that you would protect and secure the wire without having to worry about ID/Motor clearance issues.

On the avionics side, I know that Altus Metrum Products (specifically the telemega since it can do staging) can be wirelessly turned on after full integration and the rocket is on the pad. I didn't think I'd need it, but it's a dream to work with. The system stays in a standby mode until the command is given so you can connect all your pyros at your car and do continuity checks all before heading to the pad.

Stoked to see this thing!

 

[rocketace]

Hey Robert,

Thanks for the thoughts! Interesting Idea about laying up the tape wire in the CF. Ill look into this a bit more, but my initial thought is that would reduce the life of the airframe. As soon as the tape wire is damage then the airframe would have to be remade.

I have seen people use the Telemega, it is definitely a great product, but its a bit large. And considering I already have trackers and altimeters I didn't want to purchase new ones. Now having said that, when the Tiltometer 3 was released last week I bought one... I couldn't resist. I wasn't even considering a tilt meter due to the small size of my 54mm airframe, but with how small the form factor is for the new one, I am almost positive I can incorporate it to increase the safety margin a bit.

Project update:
Not much, progress has been slow. House hunting has been the main source of the delay. But closing and moving in to my first house next month. Finally having a garage will help this and my other projects a lot!

Altimeter change:
I did end up getting a Mini Alti Duo V2 altimeter which I will be trying out and probably using in this project. It doesn't record, but its so small that it will make the perfect back up altimeter. This will replace my old trusty MAWD for this project to save weight and size.

Parts:
I have the parts for the test rocket. Just need to decide on the interstage coupler then put everything together.
I have the 54mm blue tube mandrel and the tape wire. Test layups are next to figure out which mylar thickness will work best. But that will probably be after I move.

 

[OzHybrid]

How did this go? Any video/pics?
Norm

 

[rocketace]

Life has got in the way (first house, job promotion, ~60hr/week, ect..) The project is still in the design phase. I have all the electronics and even the final flight motors now. But still need to build and fly the "test rocket" and start testing layups to find the exact ID that I need.

 

[OzHybrid]

Promoted to a 60 hr week. I'll add that to my oxymoron list. Right up there with military intelligence.
Time to clean the dust off........
Now get going before anyone else notices...

 

[rocketace]

Time for a small update, but progress is being made!

For the 3" test rocket here is the simulation. 1st flight will be sustainer only on a H128W. Second flight will be a Boosted dart configuration with the booster motor being a I180W. If all goes well, flight number 3 will be my first high power 2 stage flight with a I180W in the booster and a G79W in the sustainer. Motors might change based on availability. Most parts are LOC from Wildman and they arrived today! The body tube will be glassed, just trying to decide 1 vs 2 layers of FG.






For the main rocket I now have most of the parts including motors and electronics. Last few items will be the recovery gear and composite fabric. Currently going with the bellow configuration.


I even got to do a test layup to fit check clearances when the flat wire is installed.




We Still have lots of hurtles to get over. The biggest two is finding the best way to cram all the electronics in a small space, and how to get the external interstage coupler to fit good.

 

[rocketace]

Another little update, mainly progress on the test rocket.

Peeled and glassed airframes. I was being cheap and quick, So I did not use any long cure layup epoxy, therefore I had to do it inside so it would not set up as quick.


Marking and cutting fins the "Old Fashion" way. Measured out my fin on graph paper, cut out templets on cardstock, cut out the rough pattern with a jigsaw, trimmed up with my Dremel, clamped and sanded each set.


And cutting out some fin slots. More pictures coming soon.

 

[rocketace]

More incremental updates on the test rocket and homemade cord cutter that will be used with the test rocket and the minimum diameter flights.

All the structural components ready for mounting.


Fins clamped to some 90 degree aluminum to keep them straight.


Finally starting to look like a rocket!


Interstage coupler electronics bay:
Eggtimer GPS
Eggtimer Quantum (Stage separation and secondary apogee)
Mini Alti Duo V (Primary apogee and main)
RatLab dual pull switch (for the altimeters)
Featherweight magnetic switch for GPS (not mounted yet)


Not much vertical room since it the sustainer motor takes up almost half of the coupler so take full advantage of all the volume. Probably would have helped if I used something smaller than 1/4" wood and all thread, but they were scrap from other projects.


Looks a lot better all closed up!

 

[rocketace]

Now for the cord cutter.

Homemade cord cutters are finally ready for testing. Seams like 0.1 grams is a good spot where it has plenty of umph yet not too violent.


Different cords that were cut.
The top left and top center are some nylon cords. The far left white is e-match wire. Red is a zip tie. Black center bottom is an elastic cord. The right top is an elastic cord for crafts. The bottom right is a semi elastic cord for crafts. The right 2 were tested with 2 wraps going though the cutter. I did not try the blue cord, its dyneema and would not cut well.


Slo-mo video of one of the tests
View attachment IMG_4438.mov

Now to start on the overly complicated sustainer e-bay. I like to use 3D printed dummy units until everything is ready just to reduce possible damage on the actual electronics.

 

[waltr]

Great progress and it is looking good.

I'd like more details on the cable cutter.
What casing is that?
Did you need to machine the internal part to fit the casing?
What does it weight?

 

[rocketace]

Thanks Waltr.

The idea for a casing come from an older post somewhere on here. It’s a .22 mag casing. It’s the only small one long enough I could find.

I got the steel rod of McMaster, since they have such a huge selection of rods, I was able to get one that fits without turning it down. I did get a friend with better equipment to drill the holes and cut them down to size.

The casing, cutter, and tether weigh 5g. Main reason for not using s commercial one is space. I plan to use two to be redundant and the commercial ones would be a tight fit with 2 in a 54mm.

 

[waltr]

Thanks for the details. I tried making a cutter for the sustainer of my 2-stage using two pieces of brass tubing but could not get it to cut a cable. It only poured flames out the holes where the cord goes though. So used elastic and this burns/melts releasing the chute. Did a test flight last weekend and it did work.
I am also looking for a cutter that is smaller, lighter and cheaper than the comerical ones.

 

[tfish]

Thanks for the details. I tried making a cutter for the sustainer of my 2-stage using two pieces of brass tubing but could not get it to cut a cable. It only poured flames out the holes where the cord goes though. So used elastic and this burns/melts releasing the chute. Did a test flight last weekend and it did work.
I am also looking for a cutter that is smaller, lighter and cheaper than the comerical ones.

I've been doing reefed chutes since about 2010 https://www.rocketryforum.com/threads/chute-reef-line-cutter.17067/

I use a 357 case with turned down 3/8 aluminum rod. The rod can be turned down with a drill press .

here's how I use and set mine up. https://www.rocketryforum.com/threads/chute-release-vs-cable-cutter.164297/#post-2096131

Tony

 

[rocketace]

here's how I use and set mine up.

I have been bouncing around the idea of reefing but concerned about the e-match wires twisting too much during decent even with strain relief. Do you have any lessons learned for keeping the wires from twisting too much?

And thanks for the links! Lots of good info there.

 

[tfish]

about reefing? or use, of a cable cutter?
when I began playing with this type of set up, I was referring it to as 'reefed'. To me each has it's own meaning.
Reefed..removing, some or lots of a parachutes "ability".
cable cutter...releasing a parachute at a desired time.
My early reefed chute test...https://www.youtube.com/watch?v=ggtsORqpFEY
Flying it this way ended up with nothing but a tangled mess.
wrapping up the chute helped some,,
I got to thinking what was actually happening "up there" during my types of flights..and what the reefed or bundled chute had to go through before it finally was 'released'
Imaging free falling at 80 mph(?) for a couple of minutes..what will your chute, nomex blanket and shock cord look like when you need them to deploy. For a really good picture of what they will look like..do test and hang it out the window of your car..not really but..you get the idea.
I came up with using a 'deployment bag'..sort of different then what we traditionally see/use. It's more of an open mouth bag and the zip tie (used with the cable cutter) keeps the bag closed. The other end of the bag is attached to the shock cord. For my bigger rockets I actually use a "leg" of a pair of pants as the the deployment bag. I'm able to get used nomex pants and have a good supply of them. I've been meaning to to to a "goodwill store" and get a couple of pair of jeans.....and see how they hold up to the ejection charges (one pair would be a pair of kids jeans...to try on my 54mm rocket)

back to question...
to avoid wire pull and tangling...put everything inside a bag....(open the bag (cut zip tie) at a practical altitude..to give things a chance to open, slow down...and maybe give your tracker Tx or GPS a few seconds to get a couple more way points.) and keep the distance (the wires need too span) short and stiffer then your shock cord.

sorry for the long rambling reply..

disregard the name of the photo!

it should be named...'not reefed'

Tony

 

[rocketace]

Yeah I have seen a few tangled messes that’s why I have shyed away from trying to reef with a cutter. I’ll probably end up with something externally similar to what you have described and pictured.

Thanks Tony for the detailed explanation, It helps!

 

[waltr]

Thanks for added details on cable cutters. Now need to get back into the shop and build some news ones to test.

The idea of a Chute bag is good and may be the best way to keep things from getting tangled before deployment. Will be looking into also doing this.
.

 

[tfish]

@rocketace
@waltr

a couple years ago I texted a buddy through making some cutters. Here is a video of a bunch of the photos. Hopefully it is of some help.



Tony

 

[waltr]

Mod'ed the cutter I built by adding a wood dowel inside the inner tube. Did a test of a tie wrap and 0.2 gram BP. Got a pretty big bang but tie wrap cut easily and the two pieces stayed attached to the Kevlar tether.
I'm in the process to make a few more with improvements.
Thanks everyone for the ideas.

 

[rocketace]

Getting so close to being ready for a test flight. On this update is finishing the Sustainer E-Bay, sealing bulkheads, shear pins, and some CAD work on the 54mm rocket.

First up, is using some thin epoxy to coat the top of the bulkheads. This is just so they are easier to clean after flight.


Now for shear pin plates.
Drilled the holes while assembled, and reinforced with some CA. Then used the Dremel to cut out a pocket for the brass. Not shown, The brass plates were then drilled, cut to size, deburred, bent, and tacked down with CA in the pocket. Last picture here shows some epoxy to "pot" the brass into the coupler with a mylar wrap.


After a little sanding they are done.



Here is the final layout for he sustainer E-bay shown with mostly dummy electronics.
The left side has the 2 Raven (Hopefully a Blue Raven soon!), Featherweight GPS, and the GPS battery.
The right side is the ugly part over complicated part. From the top down is 3 double pull pin switches from LabRat, then RTOM3 and Eggtimer Wifi switch to help control the sustainer ignitor. At the bottom are two 7.4v-300mah batteries for the RTOM3 and Wifi switch. Below them are two 3.7v-160mah batteries for the Ravens.



Now for the fun part, how to fit all of the above in 54mm. A little CAD work makes this much more possible.
The left is the Interstage Coupler and the right is the sustainer nose cone with all the electronics.
These e-bays will 3D printed.


Also figured out the motors for the test rocket.
First flight will be just the sustainer on an H180 to test the recovery set up.
If all is good, the second flight will be a boosted dart set up with an I180 in the booster and a dummy motor in the sustainer with ignitor to test the full stack electronics.
The third flight will be an I180 to G79

That's it for now.

 

[rocketace]

Big update, with a flight!

The test rocket is now fully complete. For now, I have decided to leave out the Eggtimer Wifi Switch. Its a cool unit and in theory it should add a layer of safety, but it complicate the wiring a lot. So to simplify the wiring I have left it out. Here is the sustainer E-Bay all finished.



Did some ejection testing and 1.2g of ffff worked perfect. So primary will be 1.2g and backup will be 1.5g


Sustainer chute and cord cutters prepped for flight


Prepped for its fist its maiden flight on a H180.
Main goal is to make sure the cord cutters and the parachute packing all work nicely.


Think I am going to need a ladder for the full stack.


It was a windy day, but the flight was good! Everything ejected with no tangles and the cord cutters deployed the main as planned. The one good/bad thing was after looking at the RTOM3 data it would have prevented the ignition. For this flight the wind pushed it too much. For most of the flight it was either inhibited from the motion monitoring or excess tilt.

I was also hoping to get some deployment video from the cameras. Luckily I was able to get a few good frames. This is the best one. The primary cable cutter has fired and the parachute is opening. The secondary cutter has not popped yet.


All in all, great flight with some good data.
And a big thanks to the group at AARG in Hutto.

Ravens are now configured as well. The below is for the backup Raven that will also control the sustainer ignition. The primary Raven is set to the same, just without the time delay and no charge will be hooked on on #4.



Past few days I have been cleaning and prepping for the next flight, hopefully this upcoming weekend. It will be in a boosted dart configuration. I180 in the booster and a plane e-match with no motor in the sustainer.

After this, the only thing really left for my first high power 2 stage flight will be playing with some MagneLight.

 

[rocketace]

Ignitor test update. Using MagneLight and comparing to an AT ignitor. These tests are for G/H motors. I plan to do more testing in the future to figure out how to light the K250

Make sure the quality is turned up and slow down the speed.

 

[Hobie1dog]

Big update, with a flight!

The test rocket is now fully complete. For now, I have decided to leave out the Eggtimer Wifi Switch. Its a cool unit and in theory it should add a layer of safety, but it complicate the wiring a lot. So to simplify the wiring I have left it out. Here is the sustainer E-B

Sustainer chute and cord cutters prepped for flight
View attachment 557311

Prepped for its fist its maiden flight on a H180.
Main goal is to make sure the cord cutters and the parachute packing all work nicely.


Think I am going to need a ladder for the full stack.


All in all, great flight with some good data.
And a big thanks to the group at AARG in Hutto.

Ravens are now configured as well. The below is for the backup Raven that will also control the sustainer ignition. The primary Raven is set to the same, just without the time delay and no charge will be hooked on on #4.



Past few days I have been cleaning and prepping for the next flight, hopefully this upcoming weekend. It will be in a boosted dart configuration. I180 in the booster and a plane e-match with no motor in the sustainer.

that Electronics bay sure looks like a rather complex affair. thanks for all the pictures and congrats on a good flight

 

[rocketace]

2 Stage test rocket flight update!
Since this way my first 2 stage attempt I purposefully set the sustainer ignition parameters to have a very short window, for a learning exercise and because its a fairly low flight profile. The day in Austin with AARG was great except a bit of wind, but nothing too bad.

Overall it was good, but had 3 issues
1) Separation charge did not fire
2) Sustainer did not light
3) Sustainer parachute did not deploy

Cause
1) I had a Quantum controlling the separation charge and the minimum altitude was not met at the time the separation should have occurred. I set it to its lowest value besides OFF and it just wasn't low enough. I will set this to off for the next flight, or use a bigger motor. Yes this does make it a bit less safe since if a false launch is detected it will fire the separation charge. However its only 0.2g and with the Quantum, I can arm it when I am walking away from the rocket.
2) It seams all the parameter for ignition were met, but for some reason the raven did not show the altitude requirement was met until later which was 0.05 seconds after the set time was exceeded. The RTOM3 shows the flight was at about 9 degrees during the ignition window, so that was good. I am waiting to hear back from Adrian to see if it was user error or some miss understanding on my part.

When I think all conditions were met.


When the altitude was met the time and velocity were already cut off.


Here is how I had it programed.

3) Simply the chute was packed a bit too tight. I was trying a slightly larger cute than when I did ejection testing. When I was pulling by hand everything felt the same, but I should have re did the ejection testing. I have a new chute in the mail that will fit better. Here is a nice picture form one of the onboard cameras right after landing "bouncing" in the dirt.


Thanks to the soft dirt and some over building, there is very little damage to the rocket. The sustainer fin are mostly though the wall except the lower part with is surface mount. The area of surface mount have cracked fillets. The tubular nylon is pretty singed from the cord cutters going off while still wrapped up, so might need a new cord.

Ill get another chance next month!

Oh and here is the video.