What do you MPR and HPR people think of Thrust vector control

[AndrewB]

My project is still in development and you are correct im reconsidering it and I may change a LOT about that, I am starting a new TVC project on 76mm tubes btw they are on sale you can get two for 6$ at office depot!
Link: https://www.officedepot.com/a/products/578184/Office-Depot-Brand-Tuff-Tube-Mailing/
(Buy them before they run out if ya need em)

Back to what I was saying George My new rocket called Verizon is in development and Im currently working on my own tvc design along with learning how to code, and also learning how to design on a pcb board. George This rocket is going to look a lot like the one Joe Barnard is making, that other rocket im not sure if I want to do anymore and im like seriously reconsidering the thought. thanks for including and talking about that it makes more sense to me now. With my Verizon rocket its going to have the same goal as what the sprint rocket had sorta.

The rocket is going to look like this:
Length: 4 feet
Dia: 76mm
material for tube used: Cardboard (Mailing tubes are cheapest)
Motor: F10
desired altitude (I always start low and work my way up so for now its low altitude): 100Meters

I am probably going to be working on this project this year and the rest of the year so I am not sure how it will go but if you wanna be updated on it I might post on my personal channel for fun: https://www.youtube.com/
when I get my 3d printer and stuff thats when I really start getting to design and I get to testing and stuff.

 

[georgegassaway]

I think for our flight profiles, it is pointless.

Do you mean the same thing the way it's been done since the late 1950's?

Before before "C" motors, before cameras, before electronic payloads, before trackers, before boost gliders, before "F" motors, before helicopter recovery, before "flying saucer" models, before composite motors, before R/C rocket gliders, before altimeters, before HPR?

Were all of those "pointless"?

Vertical guided flight using gimbaling/TVC is not pointless. It's a dream come true. Lots of rocketeers have wanted to be able to launch models that had slow liftoffs, and fly vertically without pitching over badly due to weathercocking or gravity turn. Now with current technology, it is possible to do that, with gimbaled engines with very long burn motors like the F10 or G12 or G8. And without having to invent it all from scratch, either.
The Eagle Tree Guardian is still available: https://www.eagletreesystems.com/index.php?route=product/product&product_id=50

Such as convert the new Estes 1/100 Saturn-V kit to fly using a gimbaled engine, on F10 or G12 power.

I'm not saying everybody ought to be doing guided models. Indeed I can think of a few fliers that thank goodness they haven't tried (not exactly highly successful).

But don't sit on the sidelines and put down what others want to do to enjoy the hobby, advancing the state of the art, or exploring new tech for themselves. It's saying stuff like THAT, that is worse than pointless.

Perhaps you meant "your" profiles, not "our" profiles? Well, there's all sorts fo variety possible in this hobby. You fly what you want. Don't knock what other people want to fly , as long as they try to do it safely.

 

[AndrewB]

Do you mean the same thing the way it's been done since the late 1950's?

Before before "C" motors, before cameras, before electronic payloads, before trackers, before boost gliders, before "F" motors, before helicopter recovery, before "flying saucer" models, before composite motors, before R/C rocket gliders, before altimeters, before HPR?

Were all of those "pointless"?

Vertical guided flight using gimbaling/TVC is not pointless. It's a dream come true. Lots of rocketeers have wanted to be able to launch models that had slow liftoffs, and fly vertically without pitching over badly due to weathercocking or gravity turn. Now with current technology, it is possible to do that, with gimbaled engines with very long burn motors like the F10 or G12 or G8. And without having to invent it all from scratch, either.
The Eagle Tree Guardian is still available: https://www.eagletreesystems.com/index.php?route=product/product&product_id=50

Such as convert the new Estes 1/100 Saturn-V kit to fly using a gimbaled engine, on F10 or G12 power.

I'm not saying everybody ought to be doing guided models. Indeed I can think of a few fliers that thank goodness they haven't tried (not exactly highly successful).

But don't sit on the sidelines and put down what others want to do to enjoy the hobby, advancing the state of the art, or exploring new tech for themselves. It's saying stuff like THAT, that is worse than pointless.

Perhaps you meant "your" profiles, not "our" profiles? Well, there's all sorts fo variety possible in this hobby. You fly what you want. Don't knock what other people want to fly , as long as they try to do it safely.

I agree with everything said here, also I do think he means "your" instead of "Our" It is such a dream come true to see tvc on model rockets!

 

[Flyfalcons]

Do you mean the same thing the way it's been done since the late 1950's?

Before before "C" motors, before cameras, before electronic payloads, before trackers, before boost gliders, before "F" motors, before helicopter recovery, before "flying saucer" models, before composite motors, before R/C rocket gliders, before altimeters, before HPR?

Were all of those "pointless"?

Vertical guided flight using gimbaling/TVC is not pointless. It's a dream come true. Lots of rocketeers have wanted to be able to launch models that had slow liftoffs, and fly vertically without pitching over badly due to weathercocking or gravity turn. Now with current technology, it is possible to do that, with gimbaled engines with very long burn motors like the F10 or G12 or G8. And without having to invent it all from scratch, either.
The Eagle Tree Guardian is still available: https://www.eagletreesystems.com/index.php?route=product/product&product_id=50

Such as convert the new Estes 1/100 Saturn-V kit to fly using a gimbaled engine, on F10 or G12 power.

I'm not saying everybody ought to be doing guided models. Indeed I can think of a few fliers that thank goodness they haven't tried (not exactly highly successful).

But don't sit on the sidelines and put down what others want to do to enjoy the hobby, advancing the state of the art, or exploring new tech for themselves. It's saying stuff like THAT, that is worse than pointless.

Perhaps you meant "your" profiles, not "our" profiles? Well, there's all sorts fo variety possible in this hobby. You fly what you want. Don't knock what other people want to fly , as long as they try to do it safely.

Without aerodynamic stabilization, things get ugly once the motor stops burning. That's all.

 

[AndrewB]

Without aerodynamic stabilization, things get ugly once the motor stops burning. That's all.

Not really, their is science behind that. And thats why tvc is for only some things

 

[georgegassaway]

Without aerodynamic stabilization, things get ugly once the motor stops burning. That's all.

No, you said it was "pointless". Which certainly came across to me as "no point in flying these", as opposed to "doesn't coast straight at burnout".

Heh, as opposed to so many flights of non-guided models that weathercock badly, they ain't pointing straight up at burnout, often 45 degrees, even horizontal at times,

And I addressed the issues of losing stabilization at burnout. There's not much coast anyway, unless it's got more thrust to weight ratio than it should have (faster it goes, the more problems with trying to fight aerodynamic instability. Or loss of TVC control effectiveness if it is too stable flying too fast).

Ideally a gimbaled model should have a little bit of positive stability. But, also, if it is designed to maximize the coolness of a long slow vertical boost (as with endburning F10, G12, or G8), it's not going to have much velocity left to need to be stable once the motor burns out (again, see the videos I posted for Joe Barnard's Sprint 5, and Alyssa Stenberg's Gimbaled flights). Too bad there's no long duration endburning I's, or J motors. Imagine an I35 to I40 with a long sustainer burn time of 10-12 seconds. That's what makes gimbaled/TVC control for HPR problematic, poor options for ideal thrust curves (Ideal being more like the good G12 curve that is shown below the I65 regressive curve which is very bad for vectored thrust control).

 

[AndrewB]

I gatherd a bunch of parts and started doing stuff, its not assembled at all I just gathering parts on the board but here is how it looks so far (again it is not done at all yet).

 

[Flyfalcons]

Not really, their is science behind that. And thats why tvc is for only some things

Can you give us the science? All this time I figured for something to fly stable in our atmosphere, it needs to be aerodynamically stable. Or can I forget that pesky cg/cp thing?

 

[Flyfalcons]

No, you said it was "pointless". Which certainly came across to me as "no point in flying these", as opposed to "doesn't coast straight at burnout".

Heh, as opposed to so many flights of non-guided models that weathercock badly, they ain't pointing straight up at burnout, often 45 degrees, even horizontal at times,

And I addressed the issues of losing stabilization at burnout. There's not much coast anyway, unless it's got more thrust to weight ratio than it should have (faster it goes, the more problems with trying to fight aerodynamic instability. Or loss of TVC control effectiveness if it is too stable flying too fast).

Ideally a gimbaled model should have a little bit of positive stability. But, also, if it is designed to maximize the coolness of a long slow vertical boost (as with endburning F10, G12, or G8), it's not going to have much velocity left to need to be stable once the motor burns out (again, see the videos I posted for Joe Barnard's Sprint 5, and Alyssa Stenberg's Gimbaled flights). Too bad there's no long duration endburning I's, or J motors. Imagine an I35 to I40 with a long sustainer burn time of 10-12 seconds. That's what makes gimbaled/TVC control for HPR problematic, poor options for ideal thrust curves (Ideal being more like the good G12 curve that is shown below the I65 regressive curve which is very bad for vectored thrust control).

The question was fielded to MPR and HPR fliers. My answer comes more from the HPR side than the MPR side. It is a simple statement - that for the flight profiles of HPR flights, TVC is pointless. The reason for that is in the absence of aerodynamic stability, a rocket will lose its stability after motor burnout. Most of an HPR rocket's flight profile involves coasting with no power.

Can it be done as a novelty, sure. But it doesn't necessarily accomplish anything that can be accomplished better through static or active aerodynamic stability. It's your hobby and you get to enjoy it however you want.

 

[Ez2cDave]

I think that any technology, applied to Rocketry, is fine, UNLESS it subjects Rocketry to too much "scrutiny" by the "Powers That Be" . . .

If "Thrust Vector Control" were to advance to the point where "Hobby Rockets" could be considered to be "Guided Missiles", that would be detrimental to Rocketry.

Case in point, look at all the "official attention" that Drones are attracting, thanks to the actions of a few irresponsible people, recently. That is going to have a negative effect on the RC hobby.

Dave F.

 

[AndrewB]

I think that any technology, applied to Rocketry, is fine, UNLESS it subjects Rocketry to too much "scrutiny" by the "Powers That Be" . . .

If "Thrust Vector Control" were to advance to the point where "Hobby Rockets" could be considered to be "Guided Missiles", that would be detrimental to Rocketry.

Case in point, look at all the "official attention" that Drones are attracting, thanks to the actions of a few irresponsible people, recently. That is going to have a negative effect on the RC hobby.

Dave F.

ehhh, Dave I dont think TVC is heading that way and they are NOT guided missiles, I see what you mean by the comparison of the drons and understand because I took a drone class and am looking to get certified in 3 years. But they are not guided missiles and are only to be guided up for stability.

 

[AndrewB]

Can you give us the science? All this time I figured for something to fly stable in our atmosphere, it needs to be aerodynamically stable. Or can I forget that pesky cg/cp thing?

mmm I see, so basically tvc is not meant to be designed around coasting after burnout without adaptations, usually the rocket is supposed to lift off slowly with tvc and the motor has a long burn time on it. That is for a reason like you said it can not coast but their is science behind that using long burning motors you can easily go up and after motor burnout you can do 1 of 2 things (this is the short answer). One you can have fins pop out or something to control it after motor burnout for the rocket to coast or two the rocket (usually this is the case) doesn't want to coast after motor burnout so whenever the motor burns out that is apogee and it comes back down you can make that happen by adding all sorts of stuff or doing certain things I can teach you that stuff if you would like? I also am in discord servers if you want to know more about this stuff you can ask them and stuff or just ask me anything on the forum.

 

[AndrewB]

I left out a lot of info in my last reply, I would encourage you to DM me on discord or on the forum if you would like to know more its easier for me and you may get to know a little more about tvc if you would like!

 

[Flyfalcons]

Not really, thanks. You just agreed with me that aerodynamic stability is required for a rocket to coast, which was my point. So I don't see the discord you are referring to.

 

[Retrospace101]

I so badly want to try out Thrust Vectoring, yet I cannot find a solid guide to get started.

 

[afadeev]

ehhh, Dave I dont think TVC is heading that way and they are NOT guided missiles, I see what you mean by the comparison of the drons and understand because I took a drone class and am looking to get certified in 3 years. But they are not guided missiles and are only to be guided up for stability.

TVC has nothing to do with any kind of missiles guidance.
That was a clueless and trolling comment by the poster who is no stranger to many "ignore" lists, including mine.

I so badly want to try out Thrust Vectoring, yet I cannot find a solid guide to get started.

Consider the following link as a starting point:
https://bps.space/

My answer comes more from the HPR side than the MPR side. It is a simple statement - that for the flight profiles of HPR flights, TVC is pointless. The reason for that is in the absence of aerodynamic stability, a rocket will lose its stability after motor burnout. Most of an HPR rocket's flight profile involves coasting with no power.

Completely agree.

TVC is great for slow-mo starts that would not have otherwise been possible due to lack of aerodynamic off the rod stability. Very few motors are on the market to support that use-case today. That number is not zero, but it's still disappointingly small.

For post-motor burnout stabilization, or for proper HPR high-G flights, one needs aerodynamic surface controls. There have been a few one-off solutions implemented for that use-case, but I am not aware of any commercial products on the market that address that need today.

YMMV,
a

 

[georgegassaway]

The question was fielded to MPR and HPR fliers. My answer comes more from the HPR side than the MPR side. It is a simple statement - that for the flight profiles of HPR flights, TVC is pointless. The reason for that is in the absence of aerodynamic stability, a rocket will lose its stability after motor burnout. Most of an HPR rocket's flight profile involves coasting with no power.

Again, you said it was pointless. You didn't address who "our" was, or stability or anything else.

No HPR rocket can be different than what you envision as normal?

You are the national spokesperson for HPR?

And regardless, you keep missing what i said. You are HUNG UP on finless unstable rockets using TVC to fly stably. What have I been saying all along? TVC is best done when the model is slightly stable.

And indeed you are so hung up on assuming all TVC rockets must be finless and unstable, that you missed what I pointed out was the actual practical issue with doing TVC for HPR rockets. I'll let you look it my previous messages, I'm not going to repeat it for the 3rd or 4th time

 

[georgegassaway]

TVC has nothing to do with any kind of missiles guidance.
That was a clueless and trolling comment by the poster who is no stranger to many "ignore" lists, including mine.

[snip....]

For post-motor burnout stabilization, or for proper HPR high-G flights, one needs aerodynamic surface controls. There have been a few one-off solutions implemented for that use-case, but I am not aware of any commercial products on the market that address that need today.

Aerodynamic control surfaces are easier and more forgiving to do than a gimbaled motor mount. Not too hard to design a means for nose fins to pivot and be moved by servos (a bit harder to do it with control surfaces at the tail). Works well once a model gets moving fast enough to be effective (the same guidance electronics can be used regardless of control method, a matter of tweaking involved). I'm surprised more haven't been doing guidance with aerodynamic control. Although of course slow boosting TVC flights are more impressive and a better technical challenge.

Of course, I half expect at this point for Flyfalcons to jump in and on behalf of all HPR claim why aerodynamic guidance is pointless too.

 

[Retrospace101]

Speaking of TVC, what happened to those lovely LONG BURN motors, I heard that Kosdon used to sell 30+ burn motors, These would come in Handy with TVC. Someone should like start a petition to bring the long burn G11 or G12 back. They had at least 10+ burn seconds.

 

[Retrospace101]

Speaking of TVC, what happened to those lovely LONG BURN motors, I heard that Kosdon used to sell 30+ burn motors, These would come in Handy with TVC. Someone should like start a petition to bring the long burn G11 or G12 back. They had at least 10+ burn seconds.

Also the H8 was ( I think) had a 15 or 15+second burn. This is also OOP

 

[Flyfalcons]

Again, you said it was pointless. You didn't address who "our" was, or stability or anything else.

No HPR rocket can be different than what you envision as normal?

You are the national spokesperson for HPR?

And regardless, you keep missing what i said. You are HUNG UP on finless unstable rockets using TVC to fly stably. What have I been saying all along? TVC is best done when the model is slightly stable.

And indeed you are so hung up on assuming all TVC rockets must be finless and unstable, that you missed what I pointed out was the actual practical issue with doing TVC for HPR rockets. I'll let you look it my previous messages, I'm not going to repeat it for the 3rd or 4th time

Go get some fresh air, George. It's okay to disagree. And do your best to not take it to a personal level when that happens.

 

[Ez2cDave]

TVC has nothing to do with any kind of missiles guidance.

Works well once a model gets moving fast enough to be effective (the same guidance electronics can be used regardless of control method, a matter of tweaking involved). I'm surprised more haven't been doing guidance with aerodynamic control.

So, TVC has "nothing to do with missile guidance" ?

Notice that the discussion has evolved into "guidance with aerodynamic control" ( i.e. - directional control, both before and after burnout ).

One thing leads to another, eventually.

Dave F.

 

[Ez2cDave]

That was a clueless and trolling comment by the poster who is no stranger to many "ignore" lists, including mine.

Personally, I never "ignore" anyone . . . I like to see what everyone is saying . . . "Keep your friends close and your enemies closer".

Dave F.

 

[Ez2cDave]

Go get some fresh air, George. It's okay to disagree. And do your best to not take it to a personal level when that happens.

Actually, I have to agree with George here . . .

 

[Flyfalcons]

Actually, I have to agree with George here . . .

Well you're certainly welcome to disagree. As long as you don't make it personal then I'm all for it.

 

[Motocrossman24]

The very nature of a slow majestic climb on a long burn motor is that there's not going to be a lot of velocity. Such that once the motor burns out, it's not going to coast up very far. Pop-out fins just not worth the hassle for such a short coast. d

Also, TVC models fly best when they are a BIT aerodynamically stable, and err on the side of more stable than not stable. Rewatch Alyssa Stenberg's video of the gimbaled engine tests. Only two were finless, and they wobbled on boost (a precession). The ones with fins, where it was positively stable, no precession and any wobbling was minor reactions to TVC control, not aerodynamic related. There were a couple of flights, at least, where the stability was too much, where as it got faster, the stability forces fought against the steering corrective forces. So this is why I say a bit stable and not fast.

Even an I-65 is going to go too fast, because it is not an endburner type thrust curve. It is a regressive burn that simply lasts a long time, and the first half of that burning is going to make it fly very fast. The last half of the burn will produce less and less TVC control forces due to less and less thrust. Here i a comparison of the I-65 and G12 thrust curves. That I-65 thrust curve shape is bad for TVC, more suited for aerodynamic control.

Take note that Joe Barnard's latest model, Sprint, does have fins. Also, note on this flight how later in the burn it begins to slow while thrusting, and there is almost no "coast" from burnout to apogee. There is a fact about resin nozzle as Aerotech uses, that the nozzle throat erodes. As it erodes, chamber pressure drops, so thrust drops (you can see that in the G12 thrust curve above. The slight thrust drop from about 2.5 seconds to 8 seconds is nozzle throat erosion). To prevent that, would require solid machined graphite nozzles, which have gone out of favor due to cost to fabricate (Machined one by one rather than injection mold mass production. Also cheaper material cost)

the reason the rocket wobbles as speed picks up is because the eagle tree guardian is a very primitive flight controller...gains are set at a single point for the entire flight, and she obviously had to find a middle ground where it would still correct at low speed, but not wiggle terribly on the top end... modern flight controllers use tpa to reduce pids as the speed picks up, so if you could codethe fc to register gps speed or airspeed you would be able to get a far more accurate tune. You could probably even code the accelerometer to use tpa based on g’s

 

[OverTheTop]

the reason the rocket wobbles as speed picks up is because the eagle tree guardian is a very primitive flight controller...gains are set at a single point for the entire flight, and she obviously had to find a middle ground where it would still correct at low speed, but not wiggle terribly on the top end... modern flight controllers use tpa to reduce pids as the speed picks up, so if you could codethe fc to register gps speed or airspeed you would be able to get a far more accurate tune. You could probably even code the accelerometer to use tpa based on g’s

Yep. Fixed gain can give you good performance at the fast speed ( when the "plant" gain is high) but is a little prosaic at lower speeds. Turn control system gains up and the lower speeds the system performs nicer, but fast speeds result in oscillatory behaviour and limit-cycling.

What you describe is called gain scheduling. I didn't implement it in my VTS system as I was using a commercial autopilot and working with its constraints. Other people have coded gain scheduling into their systems, but it is not a trivial exercise to get it right. If I continue to experiment with my VTS I will likely head in that direction (no pun intended!).

Incidentally, my thoughts on TVC for HPR are to make sure you consider the safety aspects completely. You don't want a motor at full thrust commanding the rocket to go horizontal just at takeoff. Way too dangerous. I designed my VTS to maintain a neutral control until burnout, then provide the steering. That way the rocket is at altitude if the control system decides to go belly-up. Don't design for nominal behaviour. Always design for sub-optimal outcomes to keep things as safe as practicable.

 

[Alan15578]

the reason the rocket wobbles as speed picks up is because the eagle tree guardian is a very primitive flight controller...gains are set at a single point for the entire flight, and she obviously had to find a middle ground where it would still correct at low speed, but not wiggle terribly on the top end... modern flight controllers use tpa to reduce pids as the speed picks up, so if you could codethe fc to register gps speed or airspeed you would be able to get a far more accurate tune. You could probably even code the accelerometer to use tpa based on g’s

You lost me at "tpa". FWIW, it is not hard to build an adaptive control system with aero control. You can command a dither signal in roll and measure the response to estimate q, and adjust gains accordingly.

 

[Retrospace101]

I agree with everything said here, also I do think he means "your" instead of "Our" It is such a dream come true to see tvc on model rockets!

Agreed, I hope everyone can get TVC at some point in the future, as well as "special" motors to suit them ( In case there could be a line of motors specifically made for TVC)

 

[AndrewB]

Agreed, I hope everyone can get TVC at some point in the future, as well as "special" motors to suit them ( In case there could be a line of motors specifically made for TVC)

yeah that would be cool! I cant wait for some 20 second long burning motors to come out that would be really nice for tvc and everyone can enjoy some part of tvc in the future!