Show HN: Cygnus-X1 – A Thrust Vectoring Model Rocket Flight Computer | Hacker News Reader

Show HN: Cygnus-X1 – A Thrust Vectoring Model Rocket Flight Computer

github.com

124 pointspolishdude2054 comments

The first time I witnessed a vectored model rocket, was in 1996.

It was launched at the 5th Annual Scottish International Rocket Weekend, in Kelburn Country Park, Largs, Scotland. [0]

I was 17 years old and a member of the Paisley Rocketeer's Society [1] - one of the oldest model rocket clubs in the world, led by the late John Stewart.

Gyroc 1's vectoring was accomplished by controlling a model rocket engine by way of 2 axes controlled by a gyroscope. Subsequent Gyrocs have been made and flown. [2] (Note: the article states 1995 but the 5th IRW was in 1996 ;) )

The model rocket launched to a height of about 1-2 metres, and only managed to hover for a couple of seconds before the model rocket engine was spent, but at the time it was a glorious flight.

[0] https://www.gbnet.net/orgs/staar/report.html

[1] https://www.paisley.org.uk/paisley-history/paisley-rocketeer...

[2] http://www.ukrocketman.com/rocketry/gimbal.shtml

I wonder how many people involved in that as kids had gone on to work at NASA and other organizations.

That's a really clever name. It's a reference to the black hole Cyg X1 [1], which was among the first astronomical X-ray sources discovered. X-rays are (fortunately) blocked by our atmosphere, so X-ray astronomy began using sounding rockets and observations of just a few minutes.

[1] https://en.wikipedia.org/wiki/Cygnus_X-1

I really hope somebody that utilizes this names their rocket ‘Rocinate’ as well.

That's my hope as well :)

The Expanse did this.

Haha that and other connections as well! It's also a song by Rush of an explorer who rides his spaceship into the heart of the black hole to become the god of balance. Balance -> keeping the rocket pointed up :)

That's awesome! As soon as I saw the name I was totally hoping for that :)

Welp this made me realize what kind of filthy Rush casual I am. Started listening on my phone to see if I recognized it. Nope. Grab headphones and renew my sympathy for Alex Lifeson, in just about any other band he would be a beast lol.

Check out La Villa Strangiato next...it contains, in my quite humble opinion, the best solo Alex ever composed and performed.

Make sure to listen to Hemispheres (from the album of the same name) afterward. It continues the plot of the song and extends it with the 'god of balance' stuff the parent mentioned.

That's... even more clever! :) Obviously this astronomer is deficient in musical taste.

I immediately jumped to the Rush Hemispheres [ my favorite album by the boys, btw ] Cygnus-X1 reference, and I feel my instincts were correct when I noticed the guitar amps in the background of the thrust-vectoring video.

https://photos.google.com/share/AF1QipOiNJAihxhEA67VCx54dzVX...

I looked into building a vectored guided rocket several years back and remember discovering that it would land me in hot water with the ATF or some similar TLA. At what point does rocket guidance step into legally questionable territory?

“Stability, not guidance” — its sort of like “tax avoidance, not tax evasion”.

I’m not sure what the defined red lines are in the US, but most people building rockets big enough for the feds to worry about are following the model rocketry code and associated with NAR/Tripoli, so at least have access to more expertise to help follow the rules.

Getting the big motors requires multiple certs from those orgs, so the system tends to be self regulating to some extent, since you can’t test your code without the hardware.

I know Joe Barnard of BPS has mentioned a few times that he doesn’t release his code because the laws are unclear, and lawyers familiar with them are expensive.

Stability and guidance are both covered, specifically "gyrostabilizers or automatic pilots and integration software therefor" per ITAR. The MCTR has similar language bit I'm too lazy to find it. This is why most rocketry hobbyists won't release airfoil designs, propellant formulas, or advanced flight control systems.

The issue isn't you building a rocket big enough for the feds to care about, but the people who can build (and use) big rockets using your designs. Iran for example relies heavily on open source for its drone program.

It seems that sharing plans would be fine after verifying citizenship of the recipient.

I'm sure there are plenty of citizens of $YourCountry who are either (a) loyal to $CountryYouThinkIsBad or (b) not discerning about passing on some designs they got from an internet stranger.

Sure, but the legal problems go to them.

Only if you got them to sign an ITAR End User Certificate and you have a reasonable belief that it was completed truthfully.

HP for example is still heavily involved in the investigation of Huawei's export of HP hardware to Iran. They didn't get to just point and say "go talk to them."

I don't think that's how legal problems work.

Careful, citizenship can still hide double allegiances [0]

[0] https://www.justice.gov/usao-az/pr/former-raytheon-engineer-...

My desire to do same has barely gotten its shoes laced, but it’s attractive to me because it combines so many interesting technologies and concepts.

I think I’ve made the emotional pivot to UAVs instead because swarming and autonomous guidance & control is one of the more interesting parts to me and even if it weren’t likely to draw ’attention’, the development process for rocket is stymied by the characteristics of rocket propulsion.

Yeah and UAV's last longer and it doesn't cost $15 a pop for a 3 second burn time.

Are there any promising hybrid engines or are we stuck with solid fuel for the time being?

For model rocket stuff of this size, yeah all we got is solid motors. I've seen some larger amateur rockets that use liquid fuel though but at that point, that leaves "amateur single person" territory and it's more for larger institutions or clubs.

I flew high-power rockets under a Tripoli certification back in the late 90s. The Aerotech hybrid system looked really attractive to me at the time. I wasn't in a financial position to take the plunge, though.

I've thought about getting back into the hobby and it looks like all the hybrid systems have disappeared. The ATF permitting for solid fuel motors seemed pretty onerous back in the late 90s (I always flew at launches where I could purchase reloads for my Aerotech RMS on-site so I didn't have to deal with transporting motors) and I assume it got worse after 9/11.

Anybody know what ever happened to the hybrid systems? Aerotech's website looks like it stopped being updated about the time I left the hobby. Same goes w/ their competitor Hypertek (which I thought had a ridiculous ground-support system).

I've noticed the same. Maybe all of this YouTube tinkering will help revitalize the hobby.

Many many orders of magnitude longer and thousands of km further on hydrocarbon fuels ;)

https://en.m.wikipedia.org/wiki/The_Spirit_of_Butts%27_Farm

> My desire to [...] has barely gotten its shoes laced

This is such a hilarious phrasing but it nicely captures the feeling!

At the point where you start telling the rocket to go anywhere but upwards I'd assume. As long as it's active stabilization and not active guidance I'm assuming.

If you think this is cool, check out BPS Space on youtube

Looks like a clone of Joe’s work. Sensors, capability, and even board layout are quite similar.

Surprised there’s no mention of Joe and his “AVA” on the git.

Definitely reminiscent at first glance. I don’t know if/how Joe licenses any of his work or if any of this is infringing in any way so I’ll avoid that topic.

I will say that I am seriously impressed with folks that are able to combine so many disciplines, especially when each domain seems to have its own set of unique hard challenges.

Yeah sorry, Joe's AVA was definitely an inspiration. I'm actually part of his discord channel and a lot of people there have helped me with this design.

Yep, that's what inspired me to make this. A lot of this stuff was directly learned about from the members of his Patreon discord channel.

I really want to get into thrust vectoring model rocketry (after some experiments with solid fuel "gunpowder" based rockets).

The first major challenge is procurement! I was able to get gunpowder from a friend who has contacts in a fireworks shop. Constructing it required minimal machining and was a lot of fun. Finding parts and machining timing for liquid fueled rockets is harder!

Demonstrates thrust vectoring with a propellor. One of those "obvious when you think about it" smart ideas I didn't think of.

Yeah although the thrust given by that propellor is so much less than what the motor would give that the PID gains I've got on there won't work. I'm thinking I'll try and simulate this exact propellor setup in software with some PID gains and see if the real system works like the sim, then I'll know if that's true, I can then modify the sim and find PID values for when I attach a motor.

What would you use for such a simulation? Awesome project by the way!

The propeller test rig looks fun.

I spent a long time in Kerbal Space Program trying to increase delta-V by using oxygen breathing jet engine boosters.

Do petrol propellers work for model rockets, to at least get a boost to a thinner atmosphere?

Your thrust vectoring video has about 30 seconds where nothing happens. It would be great if that interval was shortened.

I know nothing about thrust or vectoring, so that's my only feedback.

Under GPL-3.0 - I don't object at all but out of curiosity can you actually comply with it on a microcontroller?

Why not? As long as you distribute the software in source form and the means to compile and flash it?

The anti-tivoization clauses

It's not a problem. Many microcontrollers with GPLv3 licensed firmware has been shipped with perfect GPL-compliance.

Tivoization is only defined as "They can modify or execute arbitrary code, you cannot." If neither they or you can modify the end product due to technical reasons, it's not Tivoization. FSF said:

> Tivoization: Some companies have created various different kinds of devices that run GPLed software, and then rigged the hardware so that they can change the software that’s running, but you cannot. If a device can run arbitrary software, it’s a general-purpose computer, and its owner should control what it does. When a device thwarts you from doing that, we call that tivoization.

The anti-tivoization clause basically says "the necessary technical information and data (Installation Information) must be provided to the user, so that the user can run whatever software they want, just like the developer can", for example, if firmware update is supported, the protocol must be documented and provided to the users. If signature check is used, there must be a way to get a key or bypass it. However, if nobody can modify the system in its final form (e.g. if the firmware is in OTP ROM, if the JTAG interface has been permanently disabled), it's not Tivoization, no action is needed. Arguably, when you disable EEPROM write via an one-time fuse, it ceases to be a general-purpose computer at that moment.

Thus, you can still create a product that has been completely locked down, if it has been really locked down with no backdoor to ever be unlocked again.

GPL says,

> Corresponding Source conveyed, and Installation Information provided, in accord with this section must be in a format that is publicly documented (and with an implementation available to the public in source code form), and must require no special password or key for unpacking, reading or copying.

> If you convey an object code work under this section in, or with, or specifically for use in, a User Product, and the conveying occurs as part of a transaction in which the right of possession and use of the User Product is transferred to the recipient in perpetuity or for a fixed term (regardless of how the transaction is characterized), the Corresponding Source conveyed under this section must be accompanied by the Installation Information. But this requirement does not apply if neither you nor any third party retains the ability to install modified object code on the User Product (for example, the work has been installed in ROM).

Whoa this is awesome, what kind of engine size do you use?

Haven't put an engine into it yet but it's planned for an F15 engine

I wonder if one of those hobby jets would work. Seems like there's a lot of activity in the small jet engine segment in recent years from the likes of Kratos.

He's planning for an F15 engine, which is another class entirely. If new, it's either the F100-PW-220/220E or the F100-PW-229. It has has a thrust of 17,800 lbf (79 kN) dry, or 29,160 lbf (129.7 kN) with afterburner. If he got the old F100-PW-100 it would be 23,930 lbf (106.4 kN).

I suspect he's referring to this: https://estesrockets.com/product/001650-f15-0-engines-29-mm/

correct!

Name reminds me of the black hole film.

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