# Seeing input on a Stabilization system

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#### AmysModelRockets

##### Member
I had an idea to keep a rocket flying perfectly straight. I had an idea of having two counter rotating weights (the weights of electric motors themselves should be enough) in the nose, that would keep the rocket flying straight. They would have to be counter rotating as one would just induce a spin in the rocket itself. and if it is going to spin, it would be easier just to let the fins do the job. I know there would be a weight penalty for this but for rockets meant to fly high I think the loss of altitude due to flight angle would be more than the loss of altitude due to weight. Any Ideas?

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#### Ravenex

Gyroscopic stabilization and guidance is a proven technique in professional rocketry but I would like to warn you not to call it a guidance system. Guidance systems, those that guide a rocket on a specific trajectory, are illegal in hobby rocketry. Stabilization systems, that only keep a rocket going straight and cannot be used to guide a rocket to a specific position are legal but make a lot of people in the hobby community squeamish. Be careful to stress that your system is a only a stabilizing system. As one of the few people working to bring a commercial stabilization system to the rocketry hobby I have had that conversation with this community a number of times.

#### Ravenex

I have seen a video of this applied to a rocket model, but I am unable to find it. This is the closest I can find:

Edit: I found it:

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#### AmysModelRockets

##### Member
Cool videos. Actually I though of how to test it on the ground. That's a good reference.

#### rstaff3

##### Oddroc-eteer
I have seen a video of this applied to a rocket model, but I am unable to find it. This is the closest I can find:

Edit: I found it:

That's pretty cool, thanks for the links.

##### Well-Known Member
Guidance systems, those that guide a rocket on a specific trajectory, are illegal in hobby rocketry.
Which law, exactly, is it the makes active guidance illegal? Honestly curious and I'd like to read the law to see exactly what is allowed and what isn't.

#### OverTheTop

##### Well-Known Member
TRF Supporter
Here is a little something I have had cooking for a while. Hopefully I will get some time over the Summer to complete.

Vertical Trajectory System (with some 3D printed parts)
https://www.ausrocketry.com/forum/viewtopic.php?f=56&t=5324

If you want any details, click the link. BTW, that is 4" airframe.

#### Ravenex

I think brushing these laws off as non-existent or inapplicable is careless. In some cases even discussing certain topics and details over the internet can be a violation of US law. Here is a post I made on the subject a while back:

I am involved in the DIYdrones community and the drone developer groups, my work will be derived from their open source projects, and we are having a very similar discussion in the developers group right now.

The problem we have here is that rockets are classified differently than navigation systems for planes and ground vehicles. In the case of planes and copters the regulations apply to technologies specific to military uses with qualifications like range, speed, or targeting capabilities (the exception is regulation of drone swarming tech). The separate section for rocketry has similar verbage, certain things only apply to rockets with capabilities for over 500kg of payload or 300km of range, however there is also a category for "Rockets, SLVs, and missiles not meeting the criteria of paragraphs (a)(1) through (a)(4) of this category;" with a note "Note 3 to paragraph (a): This paragraph does not control model and high power rockets (as defined in National Fire Protection Association Code 1122) and kits thereof made of paper, wood, fiberglass, or plastic containing no substantial metal parts and designed to be flown with hobby rocket motors that are certified for consumer use. Such rockets must not contain active controls (e.g., RF, GPS)." Also "(h) Systems, subsystems, parts, components, accessories, attachments, or associated equipment, as follows: (1) Flight control and guidance systems (including guidance sets) specially designed for articles enumerated in paragraph (a) of this category (MT for those articles enumerated in paragraphs (a)(1) and (a)(2) of this category); Note to paragraph (h)(1): A guidance set integrates the process of measuring and computing a vehicle's position and velocity (i.e., navigation) with that of computing and sending commands to the vehicle's flight control systems to correct the trajectory. .... (4) Missile or rocket thrust vector control systems (MT for those thrust vector control systems usable in articles enumerated in paragraph (a)(1) of this category);" There is also a separate "Missile Technology Control Regime Annex." Section with more clarification I am still reading through but has lots of things relevant to us.

Cross posted from the drone developers group:
In the US there are several separate sets of laws regarding these technologies. In the case of the legality of developing, using, or selling them within the US most specifically exclude non-weaponized uses and are based on intent of use. However when it comes to transferring items, technologies and information of US-origin to outside the US the world of US export laws comes into play and this is where the problem lies. There are two levels of export controls, the state department oversees the United States Munitions List (USML) which defines items that are considered military use and are restricted via the International Trade in Arms Regulations. Exporting anything on this list, including swarming technologies, requires registration and licensing as an arms exporter. If an item isn't on the USML it can still be on the extensive Commerce Control List (CCL) which applies to the Export Administration Regulation overseen by the US Department of Commerce&#8217;s Bureau of Industry and Security. This is for items that are dual use (military and civilian) or can be used in the production of weapons or infrastructure the US doesn't approve of. Many items are being moved from the USML to the CCL to account for the changing state of technology. The CCL applies mostly to export to hostile countries but not exclusive and includes items from laptop computers & software, to sensors and materials, to equipment. These items also require licensing or approval to export.

ITAR & USML:
https://www.ecfr.gov/cgi-bin/text-idx?SID=5a7e69ded9e360bfd53d0c779d434446&mc=true&tpl=/ecfrbrowse/Title22/22CIsubchapM.tpl

EAR & CCL:

##### Well-Known Member
I think brushing these laws off as non-existent or inapplicable is careless. In some cases even discussing certain topics and details over the internet can be a violation of US law. Here is a post I made on the subject a while back:
So exporting(physically or logically) such systems may be regulated by ITAR but the development and use within the US is not illegal, correct? As long as you're not exporting it and have no intent on harm, then it is legal within the US, correct?

#### georgegassaway

There needs to be a FAQ, this keeps coming up so often, and so many "assume" that any type of guidance is not legal.

Guidance that can hit a TARGET is not allowed. As in, homing towards an aircraft, or steering towards a ground target

Guidance to make the rocket go mostly "UP", without the capability of tracking or hitting a target, IS ALLOWED.

There have been "guided" hobby rockets since around 1968, better known as the first R/C Boost Gliders. Of course, those were like flying an R/C airplane that used a rocket motor to climb up rather than a propeller or whatever. I've been flying those kind of "guided rockets" (gliders) since 1980

First successful known Self-guided rocket was what I developed in 1988 for "Sunguidance", flying towards the sun on a sunny day. flying mostly vertically on an overcast day. Unable to track anything. (I do want to note that Forrest Mims III could have done it around 1970 if that was his only objective. But when the unique ram-air guidance steering method he was testing proved unworkable he didn't care to use more conventional servos. His project was about the steering method which was a very small and compact method that fit into in an 18mm rocket, it was not to develop a generalized overall guidance system which would have needed a big rocket with heavy servos and heavier batteries. But I am sure he could have done it if he'd wanted to make a conventionally steered onboard guidance for a model rocket. It surprised me in 1988 when I realized it was possible with relatively simple electronics that had existed for many years..... that nobody had done it years before).

Early 1990's, David Gianokos' team developed a "True Gyro" system, a spinning Piezo disc (horizontally spun), that stayed horizontal, with optical sensors to detect any angular tilt and cause pitch or yaw corrections to keep the rocket pointed vertical.

By the late 1990's, John Pursley worked up guidance systems using a mix of R/C airplane horizon-sensing autopilot and R/C "gyros" (the old R/C gyros had a lot of drift, so he used the horizon-sensing system to give the gyros a non-drift reference, and IIRC later deleted the gyros)

Some others worked with microcontrollers, like Arduinos, and the "Wii" and smart phone type sensors to program and work up their own electronic guidance systems.

The last few years, some R/C model plane autopilot systems, using the same kind of sensors and programming, have become amazingly possible to use off-the-shelf to make a rocket fly vertically, the same way those can keep a plane flying horizontally wings-level, with NO DRIFT. The Eagle Tree Guardian, for example.

And some of the R/C Multicopter controllers, in the $20-30 price range, can also be adapted for vertical guidance. But do require a bit of tinkering and some set-up/calibration using a software application like "Cleanflight". Jim Jarvis flew a very high altitude staged HPR rocket using a modified type of multicopter controller, after having first tested a bit with an Eagle Tree Guardian and wanting more programming options than the Guardian could provide for a rocket as complex as that one. Here is an early thread he started about the project. https://www.rocketryforum.com/showthread.php?122042 - George Gassaway [video=youtube;I6ZFSSBQNT0]https://www.youtube.com/watch?v=I6ZFSSBQNT0[/video] Last edited: #### Ravenex ##### Sponsor TRF Sponsor George, I think you and I are in agreement except in a semantic way. It has to do with the word guidance, which I believe is technically accurate but give people the heebees. I prefer to call it stabilization. All of the rockets you discussed were stabilized to point in one direction, in most cases up. In fact using the sensors you described, gyros, accelerometers or even light sensors are legal because they don't give you a position or heading only an orientation (the light sensor could be an exception). As you pointed out the line into illegal guidance is an ability to target something which requires position and heading. Once you add sensors such as GPS and magnetometers and the programming becomes aware of deviations in trajectory, such as with drone control boards, you cross into sketchy territory. The US Munitions List suggests this definition: A guidance set integrates the process of measuring and computing a vehicle's position and velocity (i.e., navigation) with that of computing and sending commands to the vehicle's flight control systems to correct the trajectory. Since the munitions list and other laws prohibit "Guidance Sets" I prefer to avoid the term guidance. I have also found that this semantic difference matters to the average rocket builder. Last edited: #### jadebox ##### Roger Smith TRF Sponsor As you pointed out the line into illegal guidance is an ability to target something which requires position and heading. Once you add sensors such as GPS and magnetometers and the programming becomes aware of deviations in trajectory, such as with drone control boards, you cross into sketchy territory. Nope. Please see the other discussions. There's no reason to keep harping on something that has already been settled. -- Roger #### cerving ##### Owner, Eggtimer Rocketry TRF Sponsor TRF Supporter There was also a presentation at a recent NARCON about an electronic stabilization system. Obviously, if the NAR blesses it then it's not out of the realm of hobby rocketry. #### georgegassaway ##### Lifetime Supporter TRF Lifetime Supporter If you want "sketchey territory", well, I was tempted to describe how a bunch of dumb ballistic rockets could be used for a terrorist event, but for the sake of sanity I am NOT going to describe it. I will say that if I were a terrorist who wanted to use a flying model to do something bad, to get the most effective platform, it would not use a rocket. The Super Bowl nearly 2 years ago, first one in an open stadium in a long time.... I would not have been surprised if a multicopter had flown in with some sort of "bad payload" (Of course had a multicopter flown in, set down on the 50 yard line, and DONE NOTHING, the stadium still would have been evacuated, hopefully without panic and stampede). Some news reports long after mentioned there were a few countermeasures in place for such a thing, at that Super Bowl (not the kind of stuff that is practical to do day-to-day in general, but for very special high-security events). In any case, yes, the same kind of tech and controllers used for multicopters, are being used for hobby rockets. The NAR and TRA allow them. There are no legal issues with doing so, as long the rocket guidance system is NOT one that is set up to track and hit a target. This is effectively no different from say having a manually flown R/C model airplane........ it's not a weapon until or unless the pilot purposely steers it at a target (or designs/programs it to hit a target by itself). Or a car or truck or bus if the driver wants to do something bad. Last edited: #### UhClem ##### Well-Known Member I had an idea to keep a rocket flying perfectly straight. I had an idea of having two counter rotating weights (the weights of electric motors themselves should be enough) in the nose, that would keep the rocket flying straight. How is that supposed to work? If you have identical contra-rotating gyros on the same axis they will produce forces in exact opposition to each other. #### OverTheTop ##### Well-Known Member TRF Supporter Since the munitions list and other laws prohibit "Guidance Sets" I prefer to avoid the term guidance. I have also found that this semantic difference matters to the average rocket builder. That is why I call my system a "Vertical Trajectory System" I am not the first to use this term though. #### georgegassaway ##### Lifetime Supporter TRF Lifetime Supporter FWIW - various guidance projects. In my listing of past guidance projects, one I left out was David Hein &#8217;s Quad Pod II in 2008. A micro controller, MEMS-type gyro I think, custom programming, and gimbaled engine. An F10 powered model which was intended to use the thrust spike to get it off the ground and go up, then with the rocket weighing a BIT more than the sustainer thrust, to make a powered descent down sort of like a Lunar Module. If the flight below had been in calmer weather, it probably would have &#8220;stuck the landing&#8221;. Go to 2:00 in the video: It's a very short "hop", apparently over-ballasted, too heavy. But the next scene, IT WORKS! [video=youtube;wUJx7LbRZn0?t]https://youtu.be/wUJx7LbRZn0?t=158[/video] One of the most advanced guided rocket project&#8217;s was Jim Jarvis&#8217; 2015 three-stage rocket designed to fly well above 100,000 feet. He used a very unique arrangement by putting the finned guidance system between the 1st and 2nd stages, so that the guidance system would only be used to assure the rocket was vertical or near vertical shortly before the 2nd stage ignited. It was custom programmed in several ways, using a modified Multicopter type controller. [video=youtube;i7OqOj7GHuc]https://www.youtube.com/watch?v=i7OqOj7GHuc[/video] He first began with a Guardian (at the time of the above video), then changed to the custom programmed flight controller programmed by the controller maker himself (!). A long and VERY impressive thread, here, probably the top TRF technical thread of 2015: https://www.rocketryforum.com/showthread.php?122042 One of the unique customizations was for the unit not to provide any corrections early in the boost, to do the steering corrections mainly between first stage burnout (and first stage separation), as it coasted for several seconds, then the guidance module was dropped and the second stage ignited. Below is an earlier test flight. The actual all-out flight that he did, for some reason the first stage did not separate from the guidance module, so the guidance module was unable to help guide it towards vertical, but even so the rocket flew straight enough to fly over 130,000 feet. [video=youtube;umoduWiQb-o]https://www.youtube.com/watch?v=umoduWiQb-o[/video] This project below, from this year uses a gimbaled engine and is trying to do a SpaceX Falcon type landing under thrust (same kind of flight profile as Dave Hein's Quad Pod). Still having trouble with that part. But the guidance sometimes works well enough to steer it vertical, till it starts falling downwards. Using an Arduino and gyro/accelerometer type sensors, I think. More info here: https://twitter.com/joebarnard [video=youtube;XDJpuwW1-4k]https://www.youtube.com/watch?v=XDJpuwW1-4k[/video] Here is a project using a very interesting tether method to test out the gimbaled engine and guidance programming without risking it flying off to the side if it did not work. It REALLY works well in the 2nd test at about 1:28. Using a MPU6050 with DMP gyro chip, didn&#8217;t state the micro controller. [video=youtube;xO0D0KEGc2E]https://www.youtube.com/watch?v=xO0D0KEGc2E[/video] Here&#8217;s an Arduino guidance system on a rocket using steerable nose fins. [video=youtube;pTDpV6fkEA8]https://www.youtube.com/watch?v=pTDpV6fkEA8[/video] Here is a link to another Arduino guidance system project. However the designer over-built this so heavily that then he jumped to using a much bigger rocket, which would fly much faster, and is afraid to fly the prototype guidance system as he does not think the servos or nose fins are strong enough for the higher power. Sigh, these things can be developed and tested fantastically with F!0 or G12 (even E6), not HPR unless it&#8217;s needlessly over-built like this one was. Anyway, while not flown I include it since it has a lot of documentation about the guidance. https://workshopscience.com/arduino-rocket-stabilization/ Below, Alyssa Stenberg&#8217;s 2013 R&D project using the Eagle Tree Guardian to steer vertically. The Guardian itself works off-the-shelf since it is made as an autopilot for R/C planes, does not need programming or custom wiring unless NOT done with an R/C receiver and R/C Tx. Wiring is simply: Battery->Receiver->Guardian->Servos This is with a finned rocket launched at an angle, after first being held vertical for power-up initialization (a few seconds learning where vertical/horizontal is). D12-0 to E9, took awhile to get moving fast enough for the nose fins to be effective enough, after staging. But you know what would have happened if it was ballistic from that angle: [video=youtube;kTND_wot9zI]https://www.youtube.com/watch?v=kTND_wot9zI[/video] Note the NAR flag&#8230;&#8230; that was a demo at NARAM. And here is the same project done with a gimbaled engine in a 4&#8221; rocket , its first flight with fin unit removed, using a G12 reload (it worked fine, ejection & chute deploy by R/C. Was nearly dark and the cellphone image went to black). [video=youtube;jFfp2fHkw20]https://www.youtube.com/watch?v=jFfp2fHkw20[/video] And, finally, here is Alyssa&#8217;s R&D presentation at NARAM, including several minutes of video of some of the test flights. Her project won in A Division that year. [video=youtube;A4M9Uso9EsY]https://www.youtube.com/watch?v=A4M9Uso9EsY[/video] Last edited: #### neil_w ##### Doldrum dweller TRF Supporter Fantastic rundown, thanks George. #### boatgeek ##### Well-Known Member This is a really nice thread summary. One other area that I'm interested in pursuing (but not for a little while due to other projects) is active guidance during parachute recovery. In an ideal world, I'd like to return a rocket to a set of GPS coordinates. All steering is done under chute, so it's not nearly as weaponizable as steering under power or coast. There are a couple of other TRF threads up on this where people are in the demonstrating phase rather than the thinking about how you'd do it phase. Really, if someone wanted to accomplish a terrorist attack on an open stadium, they'd never use HPR--too much of a hassle. There are plenty of other cheaper and probably more effective approaches developed by various terrorist groups around the world. Unless, of course, they simply had it in for the referee or the opposing quarterback. #### georgegassaway ##### Lifetime Supporter TRF Lifetime Supporter One other area that I'm interested in pursuing (but not for a little while due to other projects) is active guidance during parachute recovery. In an ideal world, I'd like to return a rocket to a set of GPS coordinates. All steering is done under chute, so it's not nearly as weaponizable as steering under power or coast. There are a couple of other TRF threads up on this where people are in the demonstrating phase rather than the thinking about how you'd do it phase. Ironically, the biggest problem with making a GPS guided parachute to land near the launch pad, has nothing to do with the GPS or guidance system itself. People have been trying for YEARS to do R/C steered parachutes, and nobody has come up with one where they had it work 10 times in a row. Some who have had it work more than 50% of the time, but that's not good enough when the consequences can range from crashing to flying away. Now maybe someone has worked out a way to do it that is at least 90% reliable, I'd love to find out about it and how they did it. But AFAIK nobody has (yet). But that's the main problem, getting the chute to deploy and be steered by a servo (or servos), RELIABLY flight after flight. The GPS and automation part.....that exists now for well under$100 (R/C & servos not included), just have to learn how to install it and how to use some software to set it up to do what's desired.

"Arduplane", an Airplane version of "ArduCopter" controller software, can be used to make an R/C plane steer and land itself using an onboard GPS receiver and a multicopter type of control board. I've personally seen an R/C electric sailplane actually do that, it was amazing. Of course, that is simply the airplane version of "Return To Home" (RTH), or "Return to Launch" (RTL) as used by GPS-equipped multicopters to steer, fly back, and land where they took off ("launched") from. Either commanded by the flip of a switch to go into that mode, or automatic self-activation if it loses signal from the transmitter.

FWIW - here's an onboard video of a plane doing a short flight, with an automated GPS landing using Arduplane. The thing on the nose is pitot tube sensor, which helps, but is not necessary. Imagine if the Arduplane controller with GPS was set up for a servo for a steerable parachute rather than the rudder servo on this plane.

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#### AmysModelRockets

##### Member
How is that supposed to work? If you have identical contra-rotating gyros on the same axis they will produce forces in exact opposition to each other.
It won't. I ended up going with one. However, after testing on the ground I realized that the weight that needed to spun was not practical. The motor itself, and any weight I added just was not enough.

#### bdureau

##### Well-Known Member
Ironically, the biggest problem with making a GPS guided parachute to land near the launch pad, has nothing to do with the GPS or guidance system itself. People have been trying for YEARS to do R/C steered parachutes, and nobody has come up with one where they had it work 10 times in a row. Some who have had it work more than 50% of the time, but that's not good enough when the consequences can range from crashing to flying away. Now maybe someone has worked out a way to do it that is at least 90% reliable, I'd love to find out about it and how they did it. But AFAIK nobody has (yet).

But that's the main problem, getting the chute to deploy and be steered by a servo (or servos), RELIABLY flight after flight. The GPS and automation part.....that exists now for well under $100 (R/C & servos not included), just have to learn how to install it and how to use some software to set it up to do what's desired. "Arduplane", an Airplane version of "ArduCopter" controller software, can be used to make an R/C plane steer and land itself using an onboard GPS receiver and a multicopter type of control board. I've personally seen an R/C electric sailplane actually do that, it was amazing. Of course, that is simply the airplane version of "Return To Home" (RTH), or "Return to Launch" (RTL) as used by GPS-equipped multicopters to steer, fly back, and land where they took off ("launched") from. Either commanded by the flip of a switch to go into that mode, or automatic self-activation if it loses signal from the transmitter. FWIW - here's an onboard video of a plane doing a short flight, with an automated GPS landing using Arduplane. The thing on the nose is pitot tube sensor, which helps, but is not necessary. Imagine if the Arduplane controller with GPS was set up for a servo for a steerable parachute rather than the rudder servo on this plane. [video=youtube;aDjqmHXhvJ8]https://www.youtube.com/watch?v=aDjqmHXhvJ8[/video] I guess that the APM 3.1 would be ideal for such application in a model rocket #### Handeman ##### Well-Known Member TRF Supporter Ironically, the biggest problem with making a GPS guided parachute to land near the launch pad, has nothing to do with the GPS or guidance system itself. People have been trying for YEARS to do R/C steered parachutes, and nobody has come up with one where they had it work 10 times in a row. Some who have had it work more than 50% of the time, but that's not good enough when the consequences can range from crashing to flying away. Now maybe someone has worked out a way to do it that is at least 90% reliable, I'd love to find out about it and how they did it. But AFAIK nobody has (yet). But that's the main problem, getting the chute to deploy and be steered by a servo (or servos), RELIABLY flight after flight. The GPS and automation part.....that exists now for well under$100 (R/C & servos not included), just have to learn how to install it and how to use some software to set it up to do what's desired.
I'm a perfect example of that. I built a scaled down version of a man rated parasail chute and an RC control module. The chute works great, I think. I know the RC module works great. What I have never been able to do is get a reliable deployment of the chute. It isn't like a sky diver or cargo drop where you have complete and total control of all aspects of how the chute deploys. In a rocket, there are so many variables just in what direction the nose cone is pointed when the deployment happens. Add to that other factors and getting a good and reliable deployment is very difficult.

#### dhbarr

##### Amateur Professional
You -can- control these variables by taking the nosecone out of the equation, for instance w/ a rear facing chute cannon below X m/s just before apogee.