I could use just a little guidance

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Those are "tufts" that I put on to try and spot vortices from the canards. I thought I might see something that correlated with the spin can movement.

Jim

Ah gotcha, it almost looks like there's some correlation in where it's pointing but it's subtle so who knows.
 
I built a stabilized design over 50 years ago that was made up of three hobby motors mounted to use speed up down accelleration to move the rocket around the CG.

A friend of my dad's with the batf told me it was too close to being a guidance system, with only simple controls.
An arduino with a gps and 3 axis control would make it a weapon to the wrong people.
 
I built a stabilized design over 50 years ago that was made up of three hobby motors mounted to use speed up down accelleration to move the rocket around the CG.

A friend of my dad's with the batf told me it was too close to being a guidance system, with only simple controls.
An arduino with a gps and 3 axis control would make it a weapon to the wrong people.

This issue has been discussed ad nauseum here (I think) and in other threads. Making a system that points the rocket up and/or at angles to stay within the waiver is all OK. IIRC, NAR and TRA said that controlling a parachute (or a rocket-boosted RC glider) to land in a spot is also fine as long as that spot is in a safe location. Making a guidance system that aims at a target is Not OK. Doing anything intentionally destructive is Not OK. There is a big gray area in the middle that we prefer not to test.
 
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An arduino with a gps and 3 axis control would make it a weapon to the wrong people.

I worked on a counter-UAS development program, and I can promise you that turning a model rocket into a target-seeking missile is not as easy as everyone seems to think. The "wrong people" would better spend their time finding some Stingers on the black market.
 
My senior capstone project was sponsored by the University's rocketry club. While my work was not directly tied to the navigation system, I can tell you with certainty that all the CS, EE, and CompE students, faculty, and industry volunteers involved saw no possibility of making a 6-DoF guidance algorithm run on an Atmel 328 MCU. If anyone wants to go down that rabbit hole, find an University team to partner with. The complexity, cost, access to appropriate GPS hardware is next to impossible for a hobbyist to do on their own--not to mention compliance with applicable regulations.

Stabilization, roll control, etc... Sure. Guidance under thrust... Not a chance.
 
My system attempts to control the orientation of the rocket, i.e., a specified tilt and bearing. It generally follows those instructions, but is affected by the ability of the rocket aerodynamically to hold the desired orientation, errors in the cumulative tilt and bearing calculations over time, and wind. The powers-that-be are OK with this. But, add gps or targeting and all bets are off.

Jim
 
All of that can be done with an IMU based system. No need for GPS at all in the compensation loop. If you're using active control though, simulation of your loop parameters is key. Error on the low side of each parameter for the first flight. It's much safer to have an over damped system.
 
All of that can be done with an IMU based system. No need for GPS at all in the compensation loop. If you're using active control though, simulation of your loop parameters is key. Error on the low side of each parameter for the first flight. It's much safer to have an over damped system.
I'm about 25 flights into the operation of my system. Check out videos earlier in this thread (the "Infinity" flight was pretty good).

Jim
 
So, at last report, I crashed the test rocket at AirFest. The only significant damage was to knock two fins off the spin can. It has been repaired. It's a pita to take off the residual tip-to-tip carbon and redo it, but it's now completed (except that I need to add the fin tips like those used in the last flight). I'm hoping to conduct another flight with a slightly different profile perhaps early next year.

Jim
 

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So, I added the new fin tips and everything from the AirFest flight has been repaired. A replacement L-395 is on order as well, so I'll try the "Python" flight as soon as I get a chance. The new flight profile will use a K1200 for the booster rather than the K-2050. That will result in some additional velocity on the booster, allowing more time for the sustainer motor to come up to pressure (hopefully, it will not take 5 seconds to do that the next time around).

Jim
 

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So, I added the new fin tips and everything from the AirFest flight has been repaired. A replacement L-395 is on order as well, so I'll try the "Python" flight as soon as I get a chance. The new flight profile will use a K1200 for the booster rather than the K-2050. That will result in some additional velocity on the booster, allowing more time for the sustainer motor to come up to pressure (hopefully, it will not take 5 seconds to do that the next time around).

Jim
I'm always surprised the flutter doesn't mangle your fin extensions. I guess the CF is just that stiff?
 
I'm always surprised the flutter doesn't mangle your fin extensions. I guess the CF is just that stiff?
The fin extensions are just basswood. Plenty strong out at the end of the fin. I had some previous fin tips that had a smaller span (half an inch) that were balsa. They didn't last very long. The first set of 1.5" basswood tips lasted for 4 flights as I recall.

Jim
 
So, I added the new fin tips and everything from the AirFest flight has been repaired. A replacement L-395 is on order as well, so I'll try the "Python" flight as soon as I get a chance. The new flight profile will use a K1200 for the booster rather than the K-2050. That will result in some additional velocity on the booster, allowing more time for the sustainer motor to come up to pressure (hopefully, it will not take 5 seconds to do that the next time around).
Glad to hear the Test Rocket is back together again!

That K2050 dumping so many Newtons at low altitude was a spectacular sight, but the change seems an elegant counter to a whole class of slow-ignition problems. Ignition speed and reliability have been on my mind as I contemplate staged composite flights of my own (still a long way off yet).

I know altitude isn't your priority for these tests, but does the change of booster motor look to cost much altitude?
 
Glad to hear the Test Rocket is back together again!

That K2050 dumping so many Newtons at low altitude was a spectacular sight, but the change seems an elegant counter to a whole class of slow-ignition problems. Ignition speed and reliability have been on my mind as I contemplate staged composite flights of my own (still a long way off yet).

I know altitude isn't your priority for these tests, but does the change of booster motor look to cost much altitude?
Actually, the K1200 results in a higher altitude and more velocity at burnout. I'm trying to avoid both of those things, actually. I don't want the top speed on the L395 to increase very much.

Jim
 
The fin extensions are just basswood. Plenty strong out at the end of the fin. I had some previous fin tips that had a smaller span (half an inch) that were balsa. They didn't last very long. The first set of 1.5" basswood tips lasted for 4 flights as I recall.

Jim
I think u covered this in your NAR preso, but how do attach the extensions? Just epoxy along the extension's "root" edge? Any additives to the epoxy, or none and let it seep into the extensions? What type of surface are the extensions bonding too? I realize the fins are CF, but I don't remember what the fins' cores are made from.
 
I think u covered this in your NAR preso, but how do attach the extensions? Just epoxy along the extension's "root" edge? Any additives to the epoxy, or none and let it seep into the extensions? What type of surface are the extensions bonding too? I realize the fins are CF, but I don't remember what the fins' cores are made from.
I've used CA, but these were with epoxy. The fin cores are G10. Nothing fancy.

Jim
 
So the last time I posted here, it was after the Airfest flight where the sustainer motor took 6 seconds to light and ended up coming up to pressure just after recovery system deployed. Not so good! I plan to repeat the flight later this spring when I get replacement motors from Wildman. The booster motor will be a bit larger, which should also help. The flight will be like the "Infinity Squared" flight, except that the "Serpent" flight focuses more on tilt changes than bearing changes (tilt changes are more difficult). It'll be fun.

Since I've been without a project, I have decided to try another attempt at something I did a few years back. Nearly 7 years ago (wow), I tried a beta group test of the vertical orientation system discussed in this thread. There were at least 6 experienced fliers that got a control board with the objective of building a system. There were a few systems built, and some limited success, but for the most part, the results were not as good as I would have hoped for. It's just not an easy thing to do. However, those of us working on this system have a desire to make the technology more broadly available, so we want to try another beta group. I don't exactly know how this is going to play out, but this is the starting point.

There are a couple of lessons from the previous beta group that I hope will result in more success this time around. It was clear to me from the first attempt that building an orientation system that is mechanically sufficient is not easy. Several of the systems built were simply inadequate and could never have worked. I think this factor also discouraged others from trying to construct a system. So, the lesson for me was that for this effort to be successful, a system needs to be provided that is proven and much closer to ready-to-fly. A second lesson, maybe learned after the original beta testing, is that a system probably won't work all that well unless combined with a spin can. This is another impediment to more wide-spread use of the technology since spin cans are also not that easy to construct.

I envision the following initial steps:

- Build a prototype of a design that is relatively easy to construct
- Adapt the design for 3D printing
- Develop a flight program that rocketeers can use that does useful things
- Develop a spin can that can be easily incorporated into existing or new rockets

The price of admission in the original beta testing effort was about $60 (the price of a control board). This won't be possible for the current effort due to the cost of development and the components used. But, it will still be a lot of fun - and hopefully worth the cost - for anyone that participates. I look forward to input and advice from the TRF community.

Jim
 
Hi Jim!

I think your idea for the second beta is spot on. I am prepared to commit to participate in the development work and would welcome the opportunity to help you and the rest of the team with this effort.

Please let me know what I can do to help when you are ready to get going.

Brett
 
Hi Jim!

I think your idea for the second beta is spot on. I am prepared to commit to participate in the development work and would welcome the opportunity to help you and the rest of the team with this effort.

Please let me know what I can do to help when you are ready to get going.

Brett
Brett,

You would be a great choice for this! I will definately keep you in mind when the time comes. Probably this summer. There is a lot in the que before then.

Jim
 
If you've been following this thread for a while, you may recall that I had a breakthrough with the system when I installed a bearing to support the servo spline. Prior to that, things happened that didn't seem right. After that, the system started working and became much more reliable. If you recall, though, the bearing was located in the air frame itself. It was very difficult to install the bearings, and this approach made the system essentially none-portable. So, a key design consideration is to get that essential bearing located inside of the air frame. Will it fit? We'll see.

Back in December 2019, I started working in Fusion 360 with plans to 3D print a bunch of stuff including the orientation system. Then comes the pandemic and lots of work-related stuff, and 3D printing got put on hold. Some day, I will learn it and I'm looking forward to it, but for now, my design capabilities are a little primative. But I have processes that work for me, and so I started in on a prototype for a revised design. The prototype, out of wood, will never fly, but I can play with how things are arranged and configured with something that I can actually handle. So, here's the part of the design related to the bearings. The answer to the question "will they fit" is yes, barely for a 4" air frame. So far, so good.

Jim

DSCF1120.JPGIMG_2694.JPG
 
Jim - I did something similar with canard shaft bearings on a single servo roll-control project flown at Balls a number of years ago. The rocket is a 4" diameter carbon fiber semi-scale AMRAAM (hence the canard shape) flown on a 8 sec burn A/T L339. The roller bearings are mounted on the aluminum frame and and the axles project through the body. Not very elegant but it was a concept test. It worked but there was slow roll drift towards the end of the motor burn due to the yaw sensor electronics lack of resolution/sensitivity. Next flight it will have a R/C heli heading hold pizzo gyro for servo input and we will see how well that works.

I'd be happy to participate in your second round prototype. Sounds like a cool project. BTW, love watching your multi-stage flights at Balls.

Regards, Bill Schworer

Screen grab from presentation on the project:

1645588449722.png
 
Jim - I did something similar with canard shaft bearings on a single servo roll-control project flown at Balls a number of years ago. The rocket is a 4" diameter carbon fiber semi-scale AMRAAM (hence the canard shape) flown on a 8 sec burn A/T L339. The roller bearings are mounted on the aluminum frame and and the axles project through the body. Not very elegant but it was a concept test. It worked but there was slow roll drift towards the end of the motor burn due to the yaw sensor electronics lack of resolution/sensitivity. Next flight it will have a R/C heli heading hold pizzo gyro for servo input and we will see how well that works.

I'd be happy to participate in your second round prototype. Sounds like a cool project. BTW, love watching your multi-stage flights at Balls.

Regards, Bill Schworer
Good use of roller bearings. There has to be something like that or a system won't work.

We implemented R/C heli heading hold a while back. This is in combination with proportional roll rate control. When you do roll control in combination with yaw/pitch control (which is difficult), you still get some roll, but over the flight, the heading returns to the initial heading such that there is no net roll. In the Beta testing, I anticipate that several pre-determined flight programs will be included. One will be roll control only - with the heading hold - for those that want a steady platform for video. I haven't ever done that before. I think it will work very well (done without simultaneous yaw/pitch) and I am interested in testing that. One of the goals of the beta testing.

Jim
 
I anticipate that the revised system design will look something like the attached pic. There would be two servo levels, a level for the battery and some switches, and a top level for the control board. My current system uses a vertically-oriented control board, so going to a horizontal mount will reduce the length of the system. Having the board on the top will allow access for programming (I have to take everything apart now to do that). Overall, the system will be much easier to operate.

JimIMG_2700.JPG
 
I've been working on a few spin cans along with the development of the control module. The spin can requires tubes of three different diameters. A coupler tube is the spine of the device and runs the length of it. Then, there is a set of rings produced from "air frame" tubing. Last, there is an outer tube that the fins are mounted to. This tube has to be rolled, and since strength is important, I'm rolling these out of carbon. I'm just using my normal setup where I put a little weight on the end of the cloth while rolling the tube. These will be 7-wrap tubes, and for now, I'm making enough tubes for 4 spin cans. They turned out quite well, and they sound like fine china when you tap them together.

Jim

IMG_2741.JPGIMG_2742.JPGIMG_2743.JPGIMG_2745.JPGIMG_2746.JPG
 
I anticipate that the revised system design will look something like the attached pic. There would be two servo levels, a level for the battery and some switches, and a top level for the control board. My current system uses a vertically-oriented control board, so going to a horizontal mount will reduce the length of the system. Having the board on the top will allow access for programming (I have to take everything apart now to do that). Overall, the system will be much easier to operate.

JimView attachment 506113

Sir:

I am very interested in a "flies straight up" capability and would be happy to beta test your system.

However, I foresee two issues: my smallest rocket is 6" diameter and my previous analysis has concluded that for my particular requirements a warm gas system is preferred over canards.

If it is of interest, I'd be happy to try and use your electronics to drive a N2-based thruster system designed to fit my six inch vehicle. My next flight is targeted for mid-October and I am finalizing the payload design for that vehicle over the next few weeks.

Bill C.
 
Having the board on the top will allow access for programming (I have to take everything apart now to do that). Overall, the system will be much easier to operate.
Access for the flight computer is important. Must have been a real PITA before. For next-level access, if you can, add Bluetooth connectivity so you don't need to use a cable. That makes things so much easier on my system. It also means less chance of breaking off the fragile USB connector on my FC. Was a bit of a nuisance to set up, but well worth it IMHO.
 
Sir:

I am very interested in a "flies straight up" capability and would be happy to beta test your system.

However, I foresee two issues: my smallest rocket is 6" diameter and my previous analysis has concluded that for my particular requirements a warm gas system is preferred over canards.

If it is of interest, I'd be happy to try and use your electronics to drive a N2-based thruster system designed to fit my six inch vehicle. My next flight is targeted for mid-October and I am finalizing the payload design for that vehicle over the next few weeks.

Bill C.
It's a possibility. The current system, however, puts out PWM signals intended for four canards. I can't commit to any modifications of that at this time. A system probably could be provided that did yaw/pitch only (if excluding roll control would help).

Jim
 
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