Sometimes the wiggle just means it’s happy to finally be flying

"I did a bad job" is a shocking statement for the incredible job done so far. That rocket is 90% complete, no doubt. Very impressive work!

You see the problem here is when it stopped moving it was on its side, you want it to stop with the pointy bit facing up.

Old engineer here (66 years old and a metallurgical engineer for 45+ years). One thing I noticed in the video, was that the gimbal tended to increase oscillation - it did not look damped at all. You have 2 problems - one is getting the rocket to go straight up using the gimbal, and the second is getting the motor curve right to land and actuate the gear. Simplify the problem and break it into the two parts. For instance, to reduce the oscillation of the gimbal during ascent (and to get the proper height), add some small fins to the body of the rocket. This is only a temporary thing, to allow focus on the landing portion (hardest problem). This minimizes gimbal oscillation during ascent and helps overcome the wind loading on the airframe (and allow the rocket to get to the desired height). Once you have the issues with landing resolved, you can take off the fins, and concentrate back on reducing the gimbal oscillation during ascent. You are so close. I have been following your work for quite a while and am very impressed. The interdisciplinary approach needed (mechanical engineering, electrical engineering and material science), gives me hope. Good job.

So, I had a think... You don't need to work with one landing curve, you can work with many! If AVA has enough memory, try a set of landing curves, say one per meter of altitude between 15 and 30 is those extremes are within the range the throttle can vary thrust for, and have the computer calculate expected apogee at burnout, then go into a lookup table and pull the correct curve. Depending on memory, you can vary the apogee resolution to just fit. 7 meters is obviously way out of line (as demonstrated), but depending on various factors a meter might be plenty. Alternatively, are there any weird discontinuities between the landing profiles needed for various apogees? If not, a scaling factor or two derived from that particular flight's predicted apogee might be enough, and that's both smaller and faster to execute.

I dug out the code from a mars landing simulation I worked on a while ago and here's how I handled powered descent. Is your thrust at minimum throttle below your dry weight? If so, you could use a similar approach: If above 5 metres, the target velocity 'v' is set assuming constant deceleration: v = sqrt(u^2 + 2as), where 'u' is our desired end velocity (zero), 's' is our altitude plus 5 metres, and 'a' is our maximum theoretical deceleration rate at this exact moment in time including gravity. This makes optimum use of delta v. If below 5 metres, the target velocity is set linearly based on altitude, decreasing to 0.5 m/s at zero altitude to ensure a firm touchdown at which point the engine is cut. By trying to get to zero velocity by 5 metres, we build in a safety net in case we under perform. A PID controller uses the throttle to achieve target velocity. I found this worked reliably under all sorts of descent conditions. The code is in vector form. double target_velocity = sqrt(2 * ((MAX_THRUST - Fg.abs()) / lander_mass) * (position.abs() - MARS_RADIUS - 5)); if (position.abs() - MARS_RADIUS < 5) target_velocity = 0.5 + Kh * (position.abs() - MARS_RADIUS); velocity_error = -(target_velocity + velocity * position.norm());

Reasons why I love this channel: Awesome projects Never gives up Great techincal information *Puts what everyone wants to see at the start of the video*

The “We’ll be right back” right as it turned sideways was hilarious!

First of all: MAD respect for what you have done so far!!! Regarding your invitation for feedback: I am studying aerospace and rocket science in Germany and in one interesting lab on the calibration of sensors we learned about one possible source of the problem with the "wiggling". Broadly speaking if you want to measure something correctly you need to measure at least 10 times more often than the expected change rate of what you are measuring. For example if you are measuring something that would plot a sinus wave and you start at 0 and measure it only every "pi" interval the results will be a constant 0. If you measure it every "pi/2" the result will be a weird "wiggle" of 0, 1, 0, -1, 0,.... if you measure it in smaller increments of "pi/10" you actually start getting a kinda smooth sinus wave. What I am hinting at is that one possible problem is that the interval in which your sensors measure (or your servos react) are to slow compared to the change rate of what you are measuring / trying to correct. Secondly, someone else has encountered your problem and has solved it. It is a guy trying to build a solar tracker, but it kept over correcting and started to "wiggle". The video is short and about half way through he talks about this initial problem and how he solved it. kzfaq.info/get/bejne/hdBheJqgnLCXoZc.html "World's simplest sun tracker." by "3D Printer Academy". Hope that helps. Would love to see you succeed!!!

Finally. I just watched and hoped to release a new video and it came true. well thank you

I’ve been following you since you had 5k subs. You are so close to sticking a landing and I’m going to be super proud when you do. It’s been years in the making and you’re super close!

9:39 perhaps the solution is to not calculate it at peak thrust, but rather at peak apogee, therefore you have a consistent way to slow the rocket down to touchdown? Another possible solution is to have multiple plot points set for different altitudes, for example one at 25m, 20m, and 15m, and switch to them based on reached height of the rocket.

For the higher level control of when to light motors you are already getting dangerously close to model predictive control that you might as well make an MPC.

Can’t wait to see the future of Scout F! Good luck with the attempts!!!

It's so cool to watch you do what you do, thanks Joe!

Only just recently found your channel and 1) I’m not an engineer 2) yesterday I tourney 70, 3) launched my first model Rocket a simple old Centauri Model that I launched and it just flew out of sight and the parachute drifted my first rocket out of sight never to be seen again. 😂 that was in 1965 😳😂 watching your channel is just amazing entertainment for one who remembers vividly the early space race days. I stayed home from school to watch Alan Sheppard’s first suborbital flight and I still can’t believe Mom allowed me to do that! Undaunted I built more rockets and flew them until I discovered the opposite sex 🤦🏻‍♂️😉. Then when I had kids, I reentered the model rocketry hobby and got my son and daughter involved and it was great family fun.

I’ve been SOO hyped for your uploads I’m so excited

The fact that youre doing things this advanced this young is astonishing. You seem like you will be successful

So close!! I am incredibly impressed by how much work you've put into this and how good of results you're getting.

Nicely done as always Joe

Onshape is awesome, cool to see you getting more sponsers

You always impress me with you persistence! Keep it up!

Awesome dude! Every iteration brings new improvements and new learning. Great work Joe.

Nice one Joe - great development so far

You are so close! This is super impressive. Love your videos. Keep it up!

Good to see your still at it excellent work really liking your stuff things

i have been following u now for couple of years ...the kind of dedication u have...that gives me motivation

Excellent video. Great to see you back in good form 🙂

Have used Onshape for years at work and it's great. 👍👍

I've followed you for years now, you are amazing and so inspiring. keep the awesome work and education coming !

I always love seeing one of your videos show up on my subscribtions feed. You WILL nail this, of that, I''m confident. Cheers!

Good work man. You have come a long way.

i love your channel. i've been following it for quite a while. i'm so glad you're not giving up. Greetings from Germany

This is absolutely epic. You’ve come a long way

Your Passion for this Project is inspiring!

Congrats on an awesome sponsor like onshape 👌

You are inspiring. Thank you for the way you engineer and think through these issues. I really appreciate this.

I enjoy the project and videos. Please keep progressing and good luck!

The work you do, really impresses me and for me you are doing what i can only dream of.

Just found this video, stick with it your onto great things. All the best for a great future.

Always look forward to these videos.

MY DUDE! Excellent execution here! The setup is looking so mature at this point. Scout will 100% nail this, I'm convinced! Next flight will be!

I've been waiting for this upload for ages

I had a couple of dangerous ideas of how you could control of the throttle on a solid rocket motor. Activity control the amount of exposed surface area of the fuel grain. One way was to push a carbon rod into the top center of the rocket motor. Then during flight, have a linear servo push or pull the rod. Another idea would be to split the rocket motor vertically into 3 or more shafts. Then rotate them together like an iris

Beautiful job Joe! Cannot wait to see the bigger motors:)

What an epic project. Incredible challenge. I can't imagine anyone else doing something similar. Great film. Mahalo for sharing! 🙂🐒👍

Dude this is really awesome!!! Bears close resemblance to the Grasshopper tests and the Falcon 1....and yeah knowing how that lil program turned out....you'll get there too!!! Awesome work..!!!

Wow, very cool. Looking forward to see the progression of this.

As a new aerospace engineering graduate, your videos are AMAZING and help me to get excited again for the work I do and the projects I want to work on!

Am I the only one who sees a notification for a new BPS video and waits until they have spare time in the day to enjoy every second of the video to gobble it all up! Love it Joe! Great work!!

Stellar work miboi, love seeing some good engineering

bro you're so cool no matter all the accidents you have you can easily just brush it off and I hope your dreams come true one day

Came to have a look after Marcus House gave you a shout out on his channel. So glad he did. Really looking forward to seeing up coming videos!

Incredible work. Just awesome

wow, that link is so cool, it’s like magic!

Awesome start !!!

just before I watch, the celebration and excitement I had when I saw you released a video is just "extreme"

I have loved watching this develope over the years. I can't to see your next flight

Really awesome project, thanks for the content

I just wana say I really dig what ya got going on with this rocket.

love your work

Im not a rocket scientists, mostly an idiot really, but I was working on a really difficult project for my channel with similar problems, still haven't finished. I built a few prototypes for a self landing bottle flip bottle (you throw it, and it lands every time after a full "flip"). I faced a similar issue where I had to draw a curve that would time the landing with the initial unknown throw of the bottle. Because of mechanical design issues, I was only able to fully test it on one axis, but what ended up working almost perfectly was continuously recalculating a rotation curve on the fly. This permitted me to throw the bottle with almost any angular speed and, if it could exert enough force over time to correct, would land perfectly straight. My on board system knew it had a set time to achieve full rotation and stabilize, it also knew its maximums forces it could apply to correct the rotation speed. With those, I was able to dynamically calculate new curves that smoothly transitioned from the current position and speed to the target landing angle/time. Of course, a PID controller continuously tried to match this varying curve. Hard to explain but the math behind it kind of sucks, I had to make some computer sciency shortcuts to estimate the curves and get them smooth. There are some websites that will guide you on curve fitting with the data, I introduced myself to those principles with mycurvefit.com (not the best website domain name choice but it is about math, you can also google it haha) That being said I could be completely wrong with my approach, so this could be completely useless information, but it worked in my case. Anyway love the video, super excited to see the next launch!

SCOUT! .. I am so happy you have returned to the task that first brought me to your channel ... Dont worry too much, you've got this 🙂

Joe, I just hit subscribe and like. You have got a great idea for a learning video about space. Lovely how you modulate engine thrust by diverting the plume. Just wow. DIRECTIONAL control by gimbal. Fabulous.

Running a simulation that attempts to characterize the rocket in real time could be an option. Might need something with a bit more processing power to make that work though.

I'm always amazed whenever I look at your rockets,

Joe's enthusiasm for his failures (that still return useful data) reminds me of the running joke from Milk: "We lost, but with more votes than ever!" That, and the fact that he doesn't make you wait for the money shot are two of the biggest reasons I love his work.

Bro that's a huge effort👍

I'm 1:10 in, but holy crap! I'm so glad to have seen the progress for as long as i have! What a brilliant flight! oscillation was definitely it saying it's happy as Nicholas has!!

this is so cool! Appreciate the detailed explanation

I'm just glad it's you figuring this out and not me! Good luck on the next shot. Gunch speed.

That gimble was working some major OT!! Very awesome

Super cool, always love these video's!!!!

wow its awesome as usual

Never thought i would understand the physics of rocket dynamics but you did an excellent job explaining everything

Many people may not see it to my extent but even tho scout failed its mission i find it a masterpiece like the way it stabelized itself using a not so diy but still diy system then cut its thruster and reactivate it along with the landing legs. Masterpiece.

Its still my favorite project of yours!

awesome! you did great

Add a Prox(imeter) Center to the bottom of your rocket. When the prox hits, the 4 axis (0-90-180-270) thrust cancelling defectors activate, (with the possibility of thrust vectoring for the last 1-5 secs). So if the initial burn w/weight did/didn't achieve the proper height with the payload; it then would then wouldn't matter (On Target, No. Landed, Yes.).

great vid. Just had a thought (i'm sure easier theorized than executed) - can you redesign the throttle arms, such that when they are close, they redirect the thrust sideways in 4 (or at least 2) axis, or reversing the thrust, aiding with keeping the rocket in place. example of this can be seen in the Boeing 737 Thrust reversers.

Great progress, word to the wise softmounting your imu/gyro board will change your life! look for rubber gummies or anti vibration standoffs used for flight controllers! Another material is alpha gel! Adding these will allow you to tun your PID loop - good luck x

As a computer scientist, since you have access to real-time flight metrics and know you're landing burn constraint I would develop an algorithm or deterministic computation that would be able to handle landing at any given real-time descent. That way you aren't "hard-coding" for 25m +/- 3m. This is an incredible project, nice work!

wow! just wow! that was so dang close!

Crazy video mate!

Hi, I was made aware of your channel from watching Marcus House. Really enjoying you content!🖖

My god that's a beautiful bit of engineering from beginning to end, even if there it's not a perfectly outcome. This is the scientific method in practice and how to find solutions to problems via rigorous data collection and honest analysis of the system and decisions made to get it there. Our governments could learn from this (in no small way!). Brilliant stuff, Joe.

Moving the accelerometers up to the CM should help reduce the impact of the wiggle, and if you leave the battery back at the motor mount the CM shouldn't shift too much.

Perhaps your ceramic thrust reduction pincers should be cup shaped to redirect exhaust gasses slightly upward which would not only reduce upward force via downward thrust reduction, but could also reduce it further via the gasses redirected upward providing a downward force. This would increase the range of upward force control and also allow landing lock by fully closing to direct thrust upward once landing leg contact is detected.

Came from Marcus House, and am very impressed with your approach

Your rockets does not look like plastic anymore! Awesome!

Damn. Well done.

Just by looking at this video I know this will be epic

In my ignorance I think that one of the problems of the rocket falling on landing is the landing charge lasts for a long time there would have to be the possibility of ejecting or turning off the charge as soon as it touches the ground. the second visible problem is the landing support that perhaps should be more supported above the middle of the rocket. I really admire your project.

This is probably my favorite project going on on YT by far. Scammer Paybacks or Mark Robers big videos are cool and all, but this is something different. Don't lose hope, I think the hardware is pretty much done. With a very good worked out brain this thing will go places, high places! Take your time to give the problems the care they need and we'll see a beautiful touchdown with the rocket standing straight up! Cheers!

GOOD effort, very close!

To tame that shimmy, simply counterbalance it. When the actuator pulls the motor one way, have it move something else the other way. That way this unwanted behavior is counteracted in its own section, instead of leaking its effect to the rest of the structure. An example of a machine that uses this every day is a piston engine crankshaft, with the counterweights built into it. Where possible, they try to get the pistons to counterbalance eachother, but some cylinder counts and arrangements require more brute force. You may see some benefit in response time and weight if you design a motor pivot gimbal frame that tilts the motor from its middle, and counter tilts part of the mechanism that performs this movement.

It is getting close!

Next level!

1) the wiggle cost you apogee, but it looks so cool! 2) There’s plenty brainy folks about, but your you are real good at presenting the engineering design thinking - I hope you make it to space, but I think you may have a reasonable chance for the next prize to be a position as a professor somewhere! 3) looking forward to the next one!!

This is great progress, soon you will be like spacex