I Figured Out How To Throttle a Solid Rocket Motor

[@integza]

Your being a little harsh on the hybrids Joe, they do the best they can

[@oldUmanUshea]

I think the best deflector would have been a tomato, but this solution was nice too. Love your vids!

[@foamfpsguy6316]

Oh hi Integza, I love your channel!

[@myszot6804]

Hallo comrad! good luck

[@subwasd123]

So are tomatoes

[@justspace103]

The metal depositing happened to us on MIT Rocket team this past month when developing our new propellant. It’s called slag, and it’s pretty common in smaller motors like this.

[@jwtfpv8957]

Like when welding.

[@ReneSchickbauer]

@@jwtfpv8957 Just theorizing here, but if you have a small channel in the middle of the tongs along the path of the rocket exhaust, closing the tongs would speed up the exhaust and could potentially rip those stalagmites off. This could make the design somewhat self cleaning, especially if you introduce tiny fast movements that vary the pressure/speed in the channel very fast.

[@jkcable10]

I work with large scale solid rocket motors (SRB's) and slag is common on these as well. During horizontal static tests there will be thousands or pounds of slag at the end of burn. Keep up the good work!

[@RTFMundHDf]

@@ReneSchickbauer no, in supersonic flows a konvergent (narrowing) crosssection decreases flow velocity. Thats why a rocket nozzle is divergent (opening), which increases the speed. (for subsonic flows, our intuition, it's the opposite. which makes sense: if you could increase speed (which equals thrust) with such a measure, every rocket would look like that.

[@jorgeverdugosoto]

@@RTFMundHDf maybe can be clean up by the proppelent if you design the the cap in a specific shape?

[@simplerobotics6960]

This is awesome! Thanks for the shout out! I'm excited to support the tiny first step towards having hobby level hoppers. Lets launch and LAND these rockets propulsively!

[@silmarian]

I was literally looking at the channel earlier today to see if there was a new video. Perfect timing!

[@MadScientist267]

OMG! LITERALLY?! LIKE... Wow! This means you were... Like actually... You actually did this?! Holy shit! What will the rest of these clowns do if they can't achieve your literally epic greatness?!!? 🙄

[@lukasdimmler2622]

You can actually increase the thrust with air (air augmented rocket). If you suck in air with the bernoulli effect of the exhaust stream and then mix it with the exhaust gases in a tube the momentum can be increased. You might also want to try graphite for the deflector panels. It's very easy to machine, extremely heat resitant and probably not as expensive as the machineable ceramic.

[@ericlotze7724]

I second the graphite. My only concern would be it oxidizing/burning with atmospheric oxygen in the air when heated by the rocket, but it *should* be minimal? Also that may act in favor of preventing the slag buildup in APCP motors due to the graphite "flacking off" (similar to some anti-biofouling hull paints) Either way it is pretty cheap, damn easy to machine. The only concern i heard is it is essentially a black lung generator, BUT i think you can machine it "wet" under water and/or a good dust collection system always helps!

[@SeanBZA]

@@ericlotze7724 Yes hard graphite will work much better than the ceramic. After all it has been used in rocket motors since the V2, to guide the rocket, and while it will erode away with time, being cheap does have advantages. Yes will need to either have a HEPA filter and shroud to machine dry, or a nice pond and shield to contain the splashing if doing it wet, plus use solid carbide sharp tools. Use the CNC to drill the holes as well, just put in a pecking drilling motion, or use a smaller tool and spiral it to machine a hole bigger than the tool diameter, so the tool path creates the chip removal volume, and slow feed rate. Plus cut some of the side away where the control rods run, so they act more to the centre of the part, better control and no assymetry on the bearing surfaces it pivots on. As a bonus pivot points will also self lubricate, and have low friction. You can even use clay filled graphite that has been fired, cube resistance is not a worry here, all you need is it to be machinable and able to withstand the forces involved, plus temperature resistance. If each one lasts 5 firings before you replace it consider it a consumable like the rocket motor.

[@jimwong8056]

Graphite has high thermal conductivity. Once you ignite graphite, it will keep burning.

[@maxk4324]

@@ericlotze7724 Yes it's minimal usually

[@Blox117]

so i just have to thrust harder while she sucks in more air?

[@jamiekawabata7101]

If you had 3 flaps, perhaps you could do a combination of throttle and thrust vectoring.

[@YourArmsGone]

I like that Idea.

[@HuskyMachining]

this is a cool idea

[@ansleylobo8917]

Not worth the complexity

[@__-fm5qv]

@@ansleylobo8917 might be less complex though than sticking the rocket on a gimble

[@CruzMonrreal]

Several things : 1. Good on you with the respirator. 2. You might consider machining the ceramic underwater, kinda like how you can do so worth carbon fiber. 3. DRILL BIT MATERIAL. If you ever try to use a wood drill bit on metal, you know. But if not, drill bit material (and geometry) massively have an effect on its longevity and performance.

[@mikegofton1]

Great to see you back and making progress. As others have pointed out, graphite blocks may be a lower cost and more readily available material for your throttle mechanism. I’d also suggest using V shaped thrust deflectors to provide proportional control, i.e. vary the area impinging on the exhaust flow. Good work !

[@YourArmsGone]

You could probably control the ceramic blockers with a single servo, that might reduce side forces even more by forcing both blockers to move at the same rate. plus it's one less point of failure.

[@Unmannedair]

Having two motors though gives you de facto thrust victory.

[@Rmaia3d]

You know the video is good when it starts straight to the point and answers your question right on the first sentence! 😁

[@haydendorockets]

"Hybrids are trash" -Joey B 2022 In all seriousness, great video Joe! Super excited to see how you use this in the future. And yeah, you're probably observing "slag" (molten aluminum) buildup on the paddles when throttling the APCP motors.

[@blaircox1589]

With the making dust part, I always do my best to capture or remove whatever dust I'm making. In your case, it looks like you need a fume hood of sorts. I typically create one from plastic sheeting depending on my needs. But the basics is to control the airflow around the workspace and move the unhealthy components into a safe area. Whether that is external exhaust and/or filtering. You do this easily by means of negative or positive pressure using fans. I use contractor level fans that move a lot of air.

[@gonun69]

I guess you could just put a vacuum cleaner right next to the drill, should suck up any particles that are light enough to fly up into the air. There are also lots of models for 3D printed dust collector nozzles on Thingiverse or similar sites. Still wear a respirator though.

[@sabership]

I'm sure you already have a gimbal for your motors, but could you potentially replace the two sided blocker with a 3 or 4 sided blocker and independently control each blocker leaf to allow for a crude thrust vectoring that doesn't involve gimbaling the entire motor?

[@TDOBrandano]

It doesn't have to be crude either, deflector baffles worked for vector thrust in the X31 and NASA's F18 HARV. I think the ideal setup would use 3 or 4 "scoops" reaching into the exhaust and deflecting part of it sideways, so that by balancing the amount of side thrust you can get vectoring control at the same time as throttling of the main exhaust jet. Moving in the deflector sideways like in thrust reverser baffles would also reduce the loads on the servos.

[@nic.h]

3 baffles should be adequate, although with 4 I think you might also be able to control roll

[@dbillionaer]

Came to say this need 3 fingers

[@ericcmcgraw]

If you gimbal 2 parallel motors where the lateral range of motion approaches 90 degrees such that they're splayed out and oppose each other's thrust, you can achieve throttling without using blocking baffles. These 4 degrees of freedom will also give you 4 degrees of control. Splaying the motors in sync will control downward thrust magnitude, splaying them differentially will control lateral thrust (and be able to correct for differing amounts of thrust from each engine), rotating them along the rocket's axis together will control roll, and differentially will control the other dimension of lateral thrust. The only challenge would be after landing, if one motor burns out before the other, in which case you'll get a burst of unbalanced thrust. Perhaps the range of rotation can be extended to closer to 180 degrees, so that after landing you can direct the remaining thrust upwards. This way you could use the last amount of thrust to actually assist in stabilizing the rocket on its landing legs. It wouldn't need to be 180 degrees, just enough to vector the thrust direction to point between the landing legs.

[@Validole]

@@ericcmcgraw I think the main issue (besides the engines' thrust over time not being very repeatable, which he'll have to account for anyway) is that having such a huge gimbal range gets very heavy very quickly.

[@roboman2444]

Now you can also use the paddles to thrust-vector, and avoid the complicated gimble.

[@rocket_nerd]

That AVA in the background looks like it doesn't wanna be there. Great Vid :)

[@ELAI_aerospace]

Amazing job, amazing research, amazing vid, you are a huge inspiration joe, tbh I’ve started with the hobby thanks to you, but now it has become more than that, thank you joe, greetings from Argentina 🇦🇷 ! ♥️

[@cweagans]

Instead of milling pre-cast ceramic, have you considered using something like Porcelite? It's a 3d printer resin. After printing, you bake it in a kiln to drive out the binder and you're left with a heat tolerant ceramic part. There's some shrinkage you'd have to figure out, but I think it's pretty doable and would let you experiment with pretty elaborate geometries that might let you get multiple uses out of your thrust (for instance, can your throttling mechanism also help you with precise lateral positioning? Maybe there's some configuration of parts that would let you have this kind of control).

[@WellingtonIronman]

Integza should be able to give some advice on Porcelite

[@MrJoegotbored]

Wellington beat me to it. Integza has some experience with 3D printed ceramics and his results are wildly inconsistent across prints. It'll take several tries to get the intended geometry, and then there's still a lot of cleaning required that would likely affect the end result. Not sure I'd go this route for a launch vehicle part unless you had access to a commercial-quality printer.

[@Myname-il9vd]

6:11 words cannot describe how much I love this little dude, one of my favorite things out there idk why it’s just so fun to watch it go

[@reubenjones9567]

Seeing this gives me a ton of hope for a successful controlled landing in 2022 for you, been watching your channel for a while now and seeing your constant excitement through this video was fantastic

[@RocketVlogs]

Aluminum slag for sure! Perhaps a bit late, but a solid alternative material for your blockers is graphite! Most research APCP motors use graphite nozzles and I've done plenty of scraping slag off of them.

[@Larock-wu1uu]

Yes! I was waiting so long for this to happen! Super glad that you finally found the time to do it. Keep up the good work. You gonna land this beast!

[@PlasmaChannel]

This was really a novel idea. Have you considered running a current through the exhaust, and using electromagnetic confinement to restrict or assist the plasma flow?

[@maxk4324]

Wouldn't the power requirement on that be through the roof?

[@acorgiwithacrown467]

@@maxk4324 Not really, it only fires for a few seconds so it wouldn't be too difficult to power the electromagnets with a few LI-ion packs.

[@varunkoganti9067]

@@acorgiwithacrown467 that will abuse the li-ion packs. Not the way you use them. Short time high current means you use caps

[@acorgiwithacrown467]

@@varunkoganti9067 Ok, then use caps, my point still stands.

[@varunkoganti9067]

@@acorgiwithacrown467 that's why I suggested.

[@StatisticalError82]

Awesome concept! Have you considered angling the inner surfaces of the deflectors outward? It'd probably help a bunch if the exhaust was more cleanly deflected. As long as it was evenly deflected on both sides, net side force would be virtually non-existent It would also probably prolong the useful duration of the deflectors, maybe reduce slag buildup, and might stop hot exhaust gas from accidentally being ducted into something that could melt, like a plastic servo horn It might be tricky to machine it, but you could maybe cast it with a 3D printed mold, and there are also resin printers that can print ceramic parts, Integza uses one occasionally on his channel

[@m5w5]

Seeing real thrust control was awesome! For awhile, I thought you were going to say you could angle the engine or the whole rocket off-axis, like you've talked about in the past. also I love the return of the "he's designing the board" song

[@phoenixrising4073]

I'm seriously so happy for you; this is aside from the fact of how cool and innovative this is. The word awesome seems to be inadequate for this level of awesomeness. Keep going man!!!

[@bkdooz]

Appreciate that you talk to the safety aspect of working with ceramic dust. It's easy to ignore but pretty much any dust is not something you want to breathe in.

[@nathannation]

Is it bad I couldn't help but say "Now he's routing the traces" at 11:05 lol. Cool work Joe.

[@ash1219]

First ever non clickbait video in the history of youtube!

[@EricBu12]

Man I have been following your rocket landing attempts and the thrust to timing from your drone drops, and Coming very close to landing.. Now you have thrust blockers.. Wow!.. As a 56 yr old who did some rockets in the 80's and 90's, all this and the computer data and everything just blows me away as well as space X landing it's boosters does.. Can't wait to see you actually land a rocket on a hard surface and on a dime like SpaceX. Best of luck to you.. Keep evolving!

[@EuroGarageOfficial]

I have been working on the same project and immediately went for a hybrid set up. Building my test stand now actually.

[@MattSimmonsSysAdmin]

Great idea with the ceramic throttle body! Very cool results. Nice job!

[@C4reful]

Have you thought about modeling it after the trust-reversers on jet-engines? Many different designs out there to inspire yourself, military, comercial, private and hobby sectors all have their own solutions... And its not just a shutoff valve, but trust redirect, so might be even more efficient

[@RoseHayes-321]

Really like how you break down the thought process (and trial & error) behind the engineering.

[@idristhebean5199]

I love this newer more chaotic style of video so much please keep doing it, it is so much fun :D

[@dannyallyn223]

I feel like a little kid watching this channel. Plz post more You’re so inspiring

[@bensonboys6609]

I would have assumed that you would have varied the thrust by taking two rocket motors that you can actively control where they’re pointing and point them incrementally away from each other. Full thrust they’re pointing in the same direction, zero thrust they’re pointing in opposing directions. The thrust blocking is a great idea! I would have never thought of it! Keep up the good work!

[@AsymmetricThrust]

I LOVE this design! Can't wait to see where it goes!

[@andymuzzo8568]

This is absolutely ridiculously awesome. Well done.

[@John-uq1ye]

I sent this idea to you via your website a good while ago comparing it to how reverse thrusters work on older jets. It’s so cool to see you giving it a try!

[@DKTek07]

@10:31, a shop VAC with a HEPA filter...maybe $150. 👍Still use a respirator though. Great video!

[@NapoleonBonaparte3]

Its youtubers like you who make me a little more knowing of my dream job thanks

[@DoRC]

I mentioned this idea several times over the last few years in comments. Good to see it in action :-)

[@jonbeno9926]

Incredible work! First, the deposit is aluminum oxide, which is the result of aluminum burning in the combustion chamber. There are molten aluminum oxide droplets in the exhaust stream of aluminized solid propellent, which is still going to be over 2000 C upon impingement with your ceramic jet tabs. Second, look up jet tabs because you've made a version of these, which are commonly used for thrust vector control of some munitions. Thrust loss is effectively directly proportional to the blockage fraction, the area you cover divided by the area of the exit plane. Your design will be somewhat nonlinear as TVC, especially over time with the deposits, but as a thrust reducer I think you've nailed it. While the slag is a bit annoying and a risk that you won't be able to close down fully late in the burn, I suspect you may be able to live with that with the composite propellant motors. Good luck, I want to see you land one of these!!!

[@NonEuclideanTacoCannon]

There's a Chinese dude who's been working on a "throttleable" solid motor. His, the motor case has four nozzles that can vector outwards. To limit thrust, the four nozzles are vectored such that they no longer point down, and basically cancel each other out. It is a more analog option. Really fascinating project. His name on here is L Shang, here's his most recent update: kzbin.info/www/bejne/oGixgWZtgqqInZo

[@Blox117]

but thats wasteful

[@amperzand9162]

@@Blox117 If anything, it's less wasteful than blocking the thrust outright, as done in this video. Performance doesn't seem to be super important for this application anyway, waste is very tolerable.

[@cambridgemart2075]

It already exists in missiles, look for turnover motors.

[@rocketcello5354]

IIRC, that's pretty similar to the 1st stage of the Minuteman missile. 4 nozzles on one solid for roll control. But not throttleable

[@ETC_Rohaly_USCG]

Loved your colab with Jeff and O.G.

[@sebi-t6i]

i think you want to intentionally divert the thrust to both sides instead of blocking it with the shape of the blockers. It could -reduce stress on blockers -reduce heat -reduce metal deposition -give better control of side forces -if you manage to control their left/right motion you could even control side forces, which would be awesome

[@Pystro]

I was thinking the same. Have the first flap intercept the front half of the exhaust gases and deflect them to the right, and the second flap intercept the rear half deflecting them left. The only problem with that would be that you're trading the sideways forces for a rotational moment. It should also help with the metal deposition. Having different parts of the flaps intercept the highest concentration of metal allows you to avoid creating something that sticks out as much as that fang. And not relying on the two surfaces to touch means the metal deposition can't get in the way of it. You just need to include a sufficient gap in between the flaps so that they don't get welded together.

[@sebi-t6i]

@@Pystro i was thinking more of a wedge shape on both

[@Pystro]

@@sebi-t6i Yeah, that would probably work better than my idea, even if it's harder to manufacture. Unless you just tilt the whole flap block 45° to the side and let the exhaust hit the edge of the face that it hit in this test.

[@4729Punisher]

I'm trying to build a 4 stage solid rocket, I have been machining parts since December, when finished it will have 4 separate chambers, I'm using a paper case with an ejection charge, delay holder and delay charge with clay end cap and nozzle on all 4. This might be completely wrong for your beautiful rocket but I was having trouble keeping it stable so I built a rail gun, very simple, it's 10m long and I can angle it as far as I need. I set the charge to ignite around 1/30 of a second after the rail is charged and released. I'm just a fan of rockets and wanted to build my own, everything I done was something I taught myself through trial and error. For me I find this is the best way for my design, its just an idea to keep in the back of your mind. The rail gun helps keep on course and gives it an extra boost, it adds between 12k ft and 28k ft, getting it to about 35 miles. Good luck

[@oninoni]

You might even be able to kind of "reverse thrust" with a proper geometry for the deflectors.

[@YourMJK]

Why would you want reverse thrust in a rocket?!

[@nic.h]

@@YourMJK if you want to slow down faster than gravity allows by itself.

[@YourMJK]

@@nic.h Okay, but in which scenario would you want that?

[@amogusenjoyer]

@@YourMJK to land?

[@nic.h]

@@YourMJK rapidly accelerating in the reverse direction can be useful at avoiding obstacles. There is a whole class of quad rotors that use it to fly upside down, similarly helis use it for acrobatic maneuvers. So on a standard rocket that just likes to go straight up, not a lot probably. But you want to increase what you can do with that rocket there could definitely be uses for this.

[@gabefredrich309]

I get so excited whenever I see you post a new video. They are the highlight of my day. Thanks for another great one!

[@JerryPrado]

So if you could build a photo lens aperture like mechanism from ceramic wafers you could affect total thrust. You could move that mechanism off-center as well for thrust vectoring. Perhaps moving the center of the mechanism towards fixed paddles as needed. Great work guys, thanks!

[@ErikBongers]

I wonder if both jaws should be driven by the same servo. Because with 2 separate servos, when the opening between the jaws is really small, the slightest asymmetry will cause the exhaust to dramatically point off-center, thus messing up your TVC. In any case, a mechanical link between the two jaws would 'synchronize' them mechanically. But I'm glad you finally tackled the throttle problem!

[@CookingWithCows]

You can also use multiple engines and TVC them in opposite directions so the upward effective thrust is reduced and the sideways force is equalled out by the other engine's opposing thrust vectored thrust.

[@internalerror00]

Amazing progress. Looking forward to see it in action.

[@kynanledee5089]

Very cool! Was concerned about the side force initially but good to see it’s a non issue

[@astrofox2409]

That's amazing! I was under the impression for a while that you can sorta throttle SRMs by using different grain geometries, but that also involves somehow making very particular core/grain shapes at a very small scale, which is a very difficult task, and on top of that just making them consistent enough across all firings is another task to add onto the already difficult production of a motor like that. Seeing stuff like those ceramic blockers and hearing about the Krushnic effect really broadened my scope on this topic. Seeing the slag on the ceramic blockers genuinely made my mouth drop because of the distribution of the slag (and of course because it's glowing possibly due to blackbody radiation).

[@greenaum]

Wouldn't different grain geometries need to be done in manufacturing? Here, he needs his thrust control to be interactive, real-time, rather than planned in advance, since he's trying to land a rocket standing up. Interesting though, wonder if real rockets use it?

[@astrofox2409]

@@greenaum Yes, the grains would have to be shaped during manufacturing. The idea I had was calibrating a motor to have a very particular thrust curve that could get the rocket to land without too much trouble. In retrospect, this is a lot more complicated as you have to make the grains, make sure the motors you produce are consistent across batches, make sure to fire it off at the right time during descent, and figure out to prevent the grass underneath the rocket from getting too burned. Using only a solid rocket motor, I am not sure it is practical to go down the route I've described given its complexity. It is possible to have it work correctly at least once, but probably as a result of the infinite monkeys theorem. That isn't to say that it is impossible to combine both Joe's new method and this one - it's just that buying a motor from a highly experienced vendor takes * a lot * of the complexity away from an already complex project. Real rockets do use different grain geometries to produce different thrust curves depending on the application of the motor. However, they obviously don't land using only solids. That would be a nightmare to do on an orbital class launch vehicle.

[@harshitverma4543]

~~bit down rn so ig I'll vent here~~ its always great to see you upload, i was wandering here and there...and then started to wonder if there are any youtubers that i used to follow who haven't become shit ..and ofcourse here you are ... doing even more amazing stuff. Back when I first started watching you, i was soo much into this stuff...over past 4-5 years my interests changed... I tried to start working on them ..but I failed...and now I'm here ..with so many things right above my head...and yet unable to do anything. Your videos make feel better...they remind me of the careless kid i was... engulfed in dreams and plans...in stuff I loved. I hope I'll be able to do all that stuff someday

[@heftycat]

immediate thumbs up for the intro, thx!

[@natosaichek]

If the ceramic gives you problems, consider Molybdenum. It's got almost the same temperature handling characteristics as tungsten (melts about 2500C) , and it's almost as easy to machine as Aluminum. I guess you've gotten the ceramic working, so I guess you don't need it - but keep molybdenum in mind for future projects!

[@michaelharris679]

Love the video, my first instinct would have been to cast a propellant that was oxidizer-deficient and make a hybrid-hybrid-motor that you could throttle by starving it of it's additional flow of oxidizer, but there are a lot of good reasons not to take that approach.

[@grahams5871]

Love the lighting in the intro.

[@owenkegg5608]

I love that multiple kill vehicle. Coolest thing ever. Glad you showed it.

[@ericromano3964]

Wow!! This looks super promising. So cool to see you persist through this extremely difficult, never before done engineering challenge. Really looking forward to your future videos with this new design.

[@funkyflashfive]

To clear the dust from the air more quickly, a furnace filter in front of a box fan works super well.

[@thom7440]

Joe, you should look into how to make "Starlite" over on NightHawkInLight's channel. It would work similarly to the ceramic, but cost you $1 for a set of thrust deflectors instead $100 for the ceramic. Check out "Part 2" in his series to see how adding Borax to his recipe made it quite durable. You could also use it as a coating, along with phenolic resin and graphite, to protect a metal "skeleton" for the deflectors. Just a thought, but might be worth looking into.

[@HowToSpacic]

8:28, 9:36Joe really rocks the mustache look

[@butterpupper]

You made clamshell thrust reversers for solid rockets. Cool!

[@gutluckbro9802]

This man needs a million subsicribers, I have been hooked for weeks

[@marshallpennington2960]

Hey Joe great video and I think that you could use the ceramic thrust control for thrust vectoring if you added a additional 2 ceramic knob things and then individually controlled the servo to then block the thrust in certain directions and move the rocket in the opposite direction

[@kenreynolds1000]

You should heat the slagtites (my word) with a torch and see if they melt. I think they are mostly aluminum oxide which won't melt. I recall a prof talking about his research into abrasion of the 2 phase flow of sapphire crystals in the rocket nozzle paying for most of his house.

[@benanddadmechanical6573]

Maybe I’m just strange but I have a hunch that three paddles impinging on the exhaust jet might be better and potentially give you a modicum of thrust vectoring.

[@Craftlngo]

you'll get probably a sharp edges in the middle of the thrust that have to withstand the heat. In his solution it's two rather large flanks that have to dissipate the heat. But on the other hand I could be totally wrong and it could be a proper solution for a thrust vector steering, when you close the three paddles asymmetrically

[@420dax420]

We're stoked too. Epic work man.

[@Cole_Bailey]

This is incredible! You never fail to amaze me

[@cooperthomson9359]

Have you looked into using ESP propellants? I'm not sure how well they would work on the model scale, but they have been using in microthrusters and allow for "throttling" via an electric charge.

[@oldfridayboy5597]

What an amazing video! You are absolutely right to be stoked about the Throttle control.

[@deltametaYT]

Happy to see you back at it man!

[@johnpurvis4016]

I just wanted to say that this Vito’s not only entertaining but something about it looks visually updated…

[@alphaindustries5775]

This is genius! I cant wait to see you land a rocket using this design!

[@bragegranslaen-fjeldstad9579]

Hi Joe! Cant wait for the next Scout landing! Youre killing it! So insporational!

[@carsondobbs6824]

Awesome design and testing! Also, as someone who has seen a LOT of this aluminum fueled APCP, that's definitely slag. It's an aluminum oxide ceramic and deposits onto pretty much anything that is cooler than the exhaust flow. This includes even the nozzle throat, and you'll probably see that if you cut open that used motor. Also, I've seen this happen on any size motor, from low power up to a P class 6".

[@CharlesReiche]

I do not doubt that you will continue to make progress. I never have. Keep gettin' after it!

[@micultimy91]

Try using a 3 paddle system mounted at 120 degrees, with features that can let the gases escape much faster. Imagine an "orange peel grab" with reversed shapes of each paddle in order to let gases flow easily. Use the CNC to make the shape of each paddle from ceramic and try mounting the ceramic part to the aluminum mounts. Also, I would suggest using some sort of high speed continous rotary actuator connected to a DC motor with encoder. That way you'll have a faster response of the controls. Also, you should think about using a pneumatic control system for the paddles with a rotary control valve. If you still want to use NC/NO pneumatic valves, use an array of valves connected to a single output to have a faster response.

[@BasedBidoof]

Love the way you presented this

[@ArsenioDev]

Can you throttle a solid? No... Wii sports theme end card

[@gabrielhacecosas]

If you put two motors and if they both point down you have 100% thrust and if they point in opposite directions you have 0% thrust, and in all positions in between you have thrust range. I guess the problem will be that they both turn on at the same time and have the same thrust, but you could still try. If both have the same 2-axis gimbal, these problems might be are solved by software.

[@primate_0]

I’m so stoked! Can’t wait to see the next flight!!

[@Glasspack66]

So Cool Joe !!!! You have contributed amazing things to the Model Rocketry world !!!

[@Dallemations]

yes you can. just redirect the flow of thrust to the side of the rocket. it will burn out but if you design a special mixture of rocket fuel that reignights after being submerged in water it should work

[@Luziferne]

Your Video just got recommended to me by YT and i find your solution to the Problem of throttling a APCP or any solid fuel rocket quite interesting, even if I'm not a Rocketeer myself. That said, what got my attention are the "stalagmites" that formed on the ceramic when you used the APCP. I had to rewind the Video to be sure, but at 10:17 i found the culprit. The Slag is, as you correctly surmised, the Aluminium burning to Al2O3, or Aluminium-oxide which is the main Ingredient for Alumina Ceramics. So your APCP is throwing molten Al2O3 onto a Al2O3 surface. That's like welding molten metal onto metal, so it will build up instead of flaking of. As other here already suggested, either make the blockers out of graphite or try to coat the blockers surface with graphite, so that the Al2O3 from the APCP doesn't has a surface that it can easily get stuck to. But that's just my Ideas as a trained Chemist, not some Rocket Scientists expertise BTW, that's so awesome, i want to see more and I just Subscribed

[@mikerhodes9198]

You are a genius. The door is now open. What if rather than digital full open and full closed you create a manual control you can gradually open or close at a completely variable width based on final needed thrust for the landing to fully compensate for solid motor thrust variability near exhaustion. If that works, redesign with automation monitoring remaining landing distance and variable thrust control.

[@my3dprintedlife]

Great video! I loved the Wii intro music too. PWM was a clever approach.

[@The.Talent]

I did see this on the day it was released but I got busy and then Australian Sportsball was on and I forgot to watch this video. Today, none of my subs released new videos and I was bored till I remembered that I’d missed this video! Thanks

[@Tamb899]

You can also 3d print ceramic parts with special ceramic filament, with pretty good results to!

[@danyoung444]

I commented this idea about 2 years ago lol, glad it's working

[@maxk4324]

Fun fact, those KKVs actually only used thrusters for 4 axis stability. Pitch and Yaw were stabilized by a large spinning mass near the middle of it's length.

[@ezrarichardson279]

I would argue that a hybrid rocket is great because their among the easiest to make at home. You use wax as propellant and push O2 going threw it. Mythbusters kinda was able to make a working rocket using civil war era (or atleast possible for them) technology. So as far as DIY goes, it’s great.

[@paradiserocketry]

Another very intersecting concept!! Love it.

[@R0BL0W]

Destin at Smarter Every Day would absolutely love this

[@lucaslac124]

So, they cannot be 'throttled,' in the traditional sense (on the fly adjustments to output intensity of combustion), but you can stick a big redirecting obstacle in the path of the fire to deflect and therefore limit their directional thrust at least. Neat! Obviously, there is a huge loss in possible velocity increase, if only there was a way to recoup at least some of that energy in some way...

[@akhilathawale725]

Hey. Is there a case where this lost energy could be useful? At a model rocket scale, I simply do not see how it's going to matter on the way down. Does this have something to do with these losses mounting up and the motor burning up faster than anticipated, leaving a small chunk of the remaining flight with no control authority at all?

[@snehanshourya3850]

You can try terracotta in 3d printed moulds for high temperature structure manufacturing. You just keep compressing the terracotta into the mould every 30mins while it dries to avoid cracks. Then cook it in a furnace if you have one. If you don't have a furnace, put it in a terracotta pottery piece (pot), fill the piece with table salt, then put the pot on LPG kitchen stove at full flame for 3-4 hours. It worked okay for me. There are many other easy ways to fire terracotta at home. Ps: you don't have to bother removing the 3d printed mould. It will just burn away during cooking process.

[@dougchar]

UNC Charlotte did a throttling Krushnic effect solid motor demonstration for the NASA University Student Launch Initiative a few years ago.