bps.space Thrust Vectoring Control rocket build thread

[afadeev]

I haven't seen anyone document their TVC build yet, so I figured I will share how mine goes.

I had ordered my bps.space TVC kit last summer, right around the time I had scored one of the last remaining #2157 Saturn V kits, and decided that it would be really cool to fly it slow-mo on a TVC motor.

It took a while for the motor be shipped (Joe B was waiting on a new batch of parts to arrive). I finally got the box in the mail by early fall, by which point the work, family, other hobbies and activities got in the way of building rockets.

Next thing I know it was Xmas, then vaca, then January, when I finally found the time to get going on Saturn V (by that point I had #2157 and the new #1696 kit) and bps.space TVC kits.

For starters, here is the pic of what you get once you receive the kit:


More later,
a

 

[neil_w]

Hey, cool. Subscribed.

 

[0011001100]

Oh this is gonna be good. I've been waiting for someone to do this.

 

[afadeev]

I believe there was one option when ordering the TVC kit: having the mounts printed for 74mm (~3.0") or some larger airframes, but I ordered mine sized for 29mm motor tube and 74mm airframe.

To be clear - if you are building a TVC rocket, it will be a scratch build, as everything else other than the TVC hardware and computer are on you to supply and put together.

Thus you will need:
0. A very creative approach to OpenRocket simulation - OR will hate your TVC model, and proclaim that your rocket will leave the launch rod unstable, and tumbling. Actually, you don't even need a launch rod for TVC rockets (beyond having some way to keep them upright before lighting the motor). So I've been adding massive phantom fins to my TVC OR model to get useful speed and altitude data out of it (7 foot long 0.01" thick fins out the back ;-). Basically, aerodynamics do not matter, and I'm shooting for sub 2:1 weight:thrust ratio on the finished rocket.
1. An airframe (figure at least 3x17" body tube). You need ~8" for TVC motor & electronics, + space for bulkhead & ejection charge canister, + some room to accommodate nose cone shoulder.
2. A nose cone (you don't really need any fins, but you can certainly get creative here!). I had a nose cone laying around, from somewhere.
3. Large capacity LiPo that can maintain 7+V for long periods of time.
4. Small capacity SD card (card reader was not recognizing my 64 & 128 Gig cards, so I had to order an 8 Gig micro SD card to make it work)
5. 12" long 29mm motor mount tube - this will act as a liner inside the TVC 3D printed MMT. I had some lying around from the last supply order from www.balsamachining.com
6. Some 29mm motors.

TVC only works when there is thrust from the motor, so you want to longest burning motors you can find to maximize the show.
For that purpose, there are really just 2 good options on the market today:

• F15 (Estes). Burns for 3.5 seconds, priced at $26.99 for a 2-pack, but can be had at ~40% discount.
• F10 (Apogee is the exclusive distributor of this AT motor). Burns for 7.0 seconds, priced at $28.08.
• G8 (AT's new long-burning motor). With some luck, it will be ready to be shipped in March. Burns for 16.6 seconds, priced at $29.99.
• G11 - AT may have another long burner coming down the pike, but less clear when. Burn for 13.6 seconds with higher initial and average thrust than G8.

Hazmat shipping is required for all of the above, except Estes F15.
You could technically fly with any other 29mm motor.
However, TVC mount's pivots on 3.5mm metal screws self-threaded into 3D printed ABS plastic, so I would not put excessive g-loads on it. I don't know the limit, but I am self-constraining myself to < 10G's.
TVC mount also works only when the motor generates thrust, so if you are flying on a sub-1 second burning T/W/R motor, it's a bit of a waste.


Since my TVC rocket will go inside a 4.0" Estes Saturn V airframe, cosmetics don't really matter. Thus, I re-purposed some ~3.0" tubes left over from the last Halloween's kids shopping spree, courtesy of Nerds candy that is packaged into 3" tubes!
The tube above is a mock up of a trial rocket, with a 75mm nose cone that will hose HED.
The tube in the middle is the finished but not completely painted Estes Saturn V main airframe.
The tube on the bottom is the 16.25" long section of another Nerds candy container, that is about to be cut up to house TVC, and will go inside the SatV (see the centering rings).

 

[georgegassaway]

Look forward to this!

 

[JJSR]

I had to look this up,, WAY COOL!!!!
subscribed for sure.
Can't wait to see it in action at the farm.

 

[SpaceManMat]

Nice kit, keen to see how this works out.

Looks like TVC flight simulations during development were done using Matlab/Simulink.

OR should be able to simulations for TVC but it would require a plugin to be developed that modified the simulation behaviour accordingly. You would of course need to know details about the characteristic behaviour of the unit. I’m wondering if someone has already developed a stabilisation plungin already for OR for another stabilisation system, would be handy to have.

 

[Wallace]

Do you by chance have actual weights from the TV system alone? Just trying to get a feel for how to even begin building something that'd work with it since it's so far off the norm...

 

[BDB]

I am literally doing the same thing right now. My Saturn V just arrived last week.

I’m hoping for a slow and smoky liftofff on July 20.

 

[afadeev]

Next up - TVC assembly and testing.
The parts come in 3D-pre-printed ABS plastic segments.
Instructions are clear, detailed, and well illustrated. I will not be documenting the assembly because it was really quick and easy, and because I've already completed it without taking any mid-step pictures.
Basically, everything went exactly as per the instructions below:
https://static1.squarespace.com/sta...1546285548065/Signal+R2+-+User+Manual+1.8.pdf

If you are building yours, and you are stumped, PM me, and I will do my best to help.

After some cutting and sanding, the assembled end product looks as in pictures below.
The bit on the left is the Signal R2 circuit board in 75mm mount brackets. The bit on the right is the TVC mount:


Here is the close-up of the TVC mount itself.


Here is the assembly fully powered up, in action:

Do you by chance have actual weights from the TV system alone? Just trying to get a feel for how to even begin building something that'd work with it since it's so far off the norm...

The weights:
TVC mount, fully assembled, with wiring harnesses plugged in: 96.3g
Signal R2 computer mounted on brackets: 106.9g with 850 mAh battery, 56.0g without.

OR should be able to simulations for TVC but it would require a plugin to be developed that modified the simulation behaviour accordingly. You would of course need to know details about the characteristic behaviour of the unit. I’m wondering if someone has already developed a stabilisation plungin already for OR for another stabilisation system, would be handy to have.

I'm not sure about the need for any plugins.
The only difference between TVC and "classic" flight profile is that TVC rocket will stay stable at near-zero, and even negative acceleration levels (back sliding, or descending). So all you really need to do is to trick OR into not panicking about aero-unstable flight. I did that by adding 4 8" tall and 4" long fins of 0-weight to the back of my Saturn V rocket.

Why 4? Well, OR complained of "too many parallel fins" if I went with 5+ (I don't really know if that warning matters).

Now OR sims the flight profiles from build-in weights and motor thrust vectors without any complaints. Results appear to be reasonable, and cross-reference nicely with SatV model w/o TVC or phantom fins.

I suspect that OR height estimates are a bit exaggerated, since some of the thrust will be angled, but I can live with the presumed error (likely on the high side) of 10-20%.

I am literally doing the same thing right now. My Saturn V just arrived last week.
I’m hoping for a slow and smoky liftofff on July 20.

Can't fault you for having great taste!


I wont wait that long - will probably test fly the "mid tube Nerds" rocket on Estes F15 as soon as the weather clears (might be a week or two, the way things are trending right now).
Then "Nerds" rocket will get bolted inside Saturn V, and the full stack will fly on Apogee/AT F10. Those motors should arrive some time the next week.

OR sims the F10 flight of 550g / 19.4 oz Saturn V to 566 feet, with gentle 3.5G of acceleration. Rod clearing speed of 33 f/s.
That looks a bit too fast to be a good show, so I might add more ballast to the Saturn V rocket (around the CG, not the nose!) to slow down.
+200 g of ballast around CG slows ascent rate down to ~23 f/s, with apogee at 201 ft and acceleration of 2.3G. Hmmmm.

I am thinking 3 or 4 nut-serts epoxied to the mid-body centering rings will be sufficient to secure the Saturn V airframe to the "Nerds" TVC rocket core. Top and bottom centering rings will just friction fit to keep the inner core centered inside Saturn V airframe.

The main Saturn V airframe will gain 3-4 extra holes (below/above or on top of mid-section wraps - TBD), but those will only add character! I might cover the holes with white vinyl flaps to hide them alltogether.

Thoughts?
Questions?


Next steps - "Nerds" rocket assembly, and TVC PID calibration.
What's PID, you ask? Stay tuned.

a

 

[Wallace]

Next up - TVC assembly and testing.
The parts come in 3D-pre-printed ABS plastic segments.
Instructions are clear, detailed, and well illustrated. I will not be documenting the assembly because it was really quick and easy, and because I've already completed it without taking any mid-step pictures.
Basically, everything went exactly as per the instructions below:
https://static1.squarespace.com/sta...1546285548065/Signal+R2+-+User+Manual+1.8.pdf

If you are building yours, and you are stumped, PM me, and I will do my best to help.

After some cutting and sanding, the assembled end product looks as in pictures below.
The bit on the left is the Signal R2 circuit board in 75mm mount brackets. The bit on the right is the TVC mount:
View attachment 375968 View attachment 375969

Here is the close-up of the TVC mount itself.
View attachment 375989 View attachment 375990

Here is the assembly fully powered up, in action:





The weights:
TVC mount, fully assembled, with wiring harnesses plugged in: 96.3g
Signal R2 computer mounted on brackets: 106.9g with 850 mAh battery, 56.0g without.




I'm not sure about the need for any plugins.
The only difference between TVC and "classic" flight profile is that TVC rocket will stay stable at near-zero, and even negative acceleration levels (back sliding, or descending). So all you really need to do is to trick OR into not panicking about aero-unstable flight. I did that by adding 4 8" tall and 4" long fins of 0-weight to the back of my Saturn V rocket.

Why 4? Well, OR complained of "too many parallel fins" if I went with 5+ (I don't really know if that warning matters).

Now OR sims the flight profiles from build-in weights and motor thrust vectors without any complaints. Results appear to be reasonable, and cross-reference nicely with SatV model w/o TVC or phantom fins.

I suspect that OR height estimates are a bit exaggerated, since some of the thrust will be angled, but I can live with the presumed error (likely on the high side) of 10-20%.




Can't fault you for having great taste!


I wont wait that long - will probably test fly the "mid tube Nerds" rocket on Estes F15 as soon as the weather clears (might be a week or two, the way things are trending right now).
Then "Nerds" rocket will get bolted inside Saturn V, and the full stack will fly on Apogee/AT F10. Those motors should arrive some time the next week.

OR sims the F10 flight of 550g / 19.4 oz Saturn V to 566 feet, with gentle 3.5G of acceleration. Rod clearing speed of 33 f/s.
That looks a bit too fast to be a good show, so I might add more ballast to the Saturn V rocket (around the CG, not the nose!) to slow down.
+200 g of ballast around CG slows ascent rate down to ~23 f/s, with apogee at 201 ft and acceleration of 2.3G. Hmmmm.

I am thinking 3 or 4 nut-serts epoxied to the mid-body centering rings will be sufficient to secure the Saturn V airframe to the "Nerds" TVC rocket core. Top and bottom centering rings will just friction fit to keep the inner core centered inside Saturn V airframe.

The main Saturn V airframe will gain 3-4 extra holes (below/above or on top of mid-section wraps - TBD), but those will only add character! I might cover the holes with white vinyl flaps to hide them alltogether.

Thoughts?
Questions?


Next steps - "Nerds" rocket assembly, and TVC PID calibration.
What's PID, you ask? Stay tuned.

a

Well....According to Google PID is pelvic inflammatory disease. Hope it's not too terribly painful...

 

[Wallace]

Or did you mean process ID?

 

[gwh]

https://en.wikipedia.org/wiki/PID_controller

"A proportional–integral–derivative controller (PID controller or three-term controller) is a control loop feedback mechanism widely used in industrial control systems and a variety of other applications requiring continuously modulated control. A PID controller continuously calculates an error value as the difference between a desired setpoint (SP) and a measured process variable (PV) and applies a correction based on proportional, integral, and derivative terms (denoted P, I, and D respectively), hence the name.

In practical terms it automatically applies accurate and responsive correction to a control function. An everyday example is the cruise control on a car, where external influences such as hills (gradients) would decrease speed. The PID algorithm restores from current speed to the desired speed, with small delay and overshoot, by controlling the power output of the vehicle's engine."

 

[Wallace]

Well that makes a whole lot more sense...

 

[JJSR]

Alex will you be ready for next weekend to fly this?

 

[afadeev]

Alex will you be ready for next weekend to fly this?

"Nerds" rocket - probably.
Still waiting for the bulkhead and a coupling to be delivered to complete the electronic ejection bits.

The weather forecast, however, looks ugly every time a weekend rolls around.
We are getting another 5-8 inches of snow tonight, then some more the next weekend, then more precipitation the weekend after next. I might just go ahead and test-fly at a local baseball field one of the afternoons when we get a rare warm and sunny day.

a

P.S.: Do you know any shop around these parts (within ~90 minute driving radius of The Farm), that stocks rocketry building supplies ?

 

[JJSR]

F&M hobby on 206 in Flanders, not sure what they have on hand,, closes at 3pm 973 361 0042 give em a call

 

[afadeev]

Well, FedEx shipping adventures are delaying further progress.

For reasons unknown, Apogee/TVM shipped by FedEx with "signature required" selection. F10's are made by AT, but only sold by TVM.
The package was due to arrive on Saturday, but we had a snow storm, and FedEx did not show up. Incidentally, USPS mail-woman did a 180 as well, when she saw neighborhood kids engaged in a snow ball fight in front of our hose, looked at them, got back into the truck and did not deliver mail to the entire street. I was expecting a package for another hobby, and USPS status read: "Held at Post Office, At Customer Request". Cute.

Back to FedEx.
FedEx updated its status over the weekend to Monday delivery, "signature required". So I arranged a work-at-home for Monday, and they did not show up again.
No further updates to the status.
So I re-finagled WAH for today, and ... saw a FedEx truck drive up and down the street, then got an SMS notification that delivery will be re-attempted on Wednesday, because no-one is at home. Which is a total lie. As was the insistence by FedEx that they left delivery attempt sticker at the door (not the case). Signature is still required for re-delivery on Wednesday, and can't be waived, per sender instructions.

I forgot that TVM marks his shipments "signature required". For no good reason.
I got nailed with that once or twice before. It is a PITA.

Yet another reason I don't like ordering from Apogee, and hadn't done so for at least a year.
Alas, I had no choice this time (F10 distribution monopoly).
I have to be in the office tomorrow, so with some luck, FedEx will no-show tomorrow, again. Not sure how many times FedEx re-tries before sending package back to shipper. I guess I will find out.


arrghhh....

a

 

[Wallace]

Not sure about Fed Ex but with UPS they'll hold it at their distribution center for pick up?

 

[cerving]

How much will it all weigh with the Saturn V "skin"? A G8 would be super cool, but it may not get off the ground... anything over about 400 grams is going to be dicey. On the other hand, it would be a REALLY good test of the BPS...

 

[Tobor]

Question: Are you allowed to receive packages at work? If so, use work as your delivery address for Apogee orders?

 

[afadeev]

OK, the shipping challenges have been resolved, all parts are in, final assembly begins:



Note the two dry run motor options: Estes F15 and Apogee/AT F10.
I will need to build an OR model for "Nerds" to confirm which one is a better fit for the inaugural flight.

The nose cone and recovery gear are place-holders for the test flight only, and will not be carried over to the final Saturn V stack. They were pulled out of the spare parts bin to allow a safe test flight of the "Nerds" rocket.

Sub-assembly pics.
First, the view of the packed HED nosecone, wired deployment charge compartment, main tube with electronics and TVC mount.
Second, the aft view of the TVC motor mount.


I had decided to not fly the Saturn V centering rings with Nerds, to avoid unnecessary weight and points of failure.

Final rocket, fully assembled, electronics tested, ready to go, weights in at 681g dry (without a motor):


Observe the body cut-outs for accessing the computer to turn it on, and access/remove the SD card.
The on/off switch could have been hidden away, but ready access to SD card is highly advisable, and so is ability to view the LED light sequence as a form of debugging. I haven't decided what to do about that in the Saturn V airframe, though leaning towards adding an access door to the BT-101 airframe to preserve this.

Also, there are two cut-outs in the aft section of the airframe, to give the pivot arms extra room to pivot the TVC mount. These lower cut-outs (only one is visible in the pic above) are absolutely required for TVC to operate properly, but will be completely hidden inside the Saturn V airframe.

Lastly, the final rocket comes out at the somewhat porky 681 grams.
The nose cone and recovery gear are 250g, so the actual TVC airframe that will go into SatV is 631g.
850 mAh battery is 56g by itself, so a lighter battery could drop the TVC airframe weight down to ~600g.

Still kinda heavy, but it is what it is.

Next steps:
1). Ejection charge testing
2). Paint the nose cone some bright color so that I can see it better in the snow.
3). Test fly Nerds

We have a Club launch tomorrow, but it is in jeopardy. The shipping Gods really have it in for me this week. As soon as I resolved all the fun with FedEx box shipment (long story, happy ending), the furniture people called to inform that the stuff my wife ordered in December is finally here ... and will be delivered on Saturday, day of the Club launch.

If I don't accept delivery tomorrow, next available is on the day of my kids swim meet - no good.
Long story short, I'm not sure when and where I will fly "Nerds" rocket. But when I do, I will post the results and the video.


a

 

[JJSR]

was hoping to see this

 

[Nytrunner]

I'd pick the motor with the longer burn for the vectoring system

 

[aerostadt]

This is really a nice project. The results will indicate to us everyday users if we want to try this.

 

[JJSR]

OH, MAN,,
Did you miss the day for trying this out!
Alex, there was absolutely no wind today.
I've never seen it so calm at the farm.
One guy flew to 4000 and it landed 100 feet from the pad.
Man, I'm sorry you couldn't make it out.

 

[Thundercloud]

The BPS.Space Signal kit is very exciting! I tried to contact them through the website last week, but I didn't hear back yet. Is Joe B. normally responsive?

 

[Wallace]

Very... Must be busy?

 

[Andrew_ASC]

Keep us posted on the test flight status.

 

[afadeev]

OH, MAN,,
Did you miss the day for trying this out!
Alex, there was absolutely no wind today.
I've never seen it so calm at the farm.
One guy flew to 4000 and it landed 100 feet from the pad.
Man, I'm sorry you couldn't make it out.

Damn, me too.
There is always the next time.

For TVC, wind would be kinda fun.
I would expect the rocket to stay vertical, yet drift sideways, downwind. Could be fun to watch.

The BPS.Space Signal kit is very exciting! I tried to contact them through the website last week, but I didn't hear back yet. Is Joe B. normally responsive?

It's a roll of the dice, in my experience.

Email is the only form of communication.
Sometimes you get an email response the same day, usually in a few days days, other days a week later, occasionally never.
In the latter use-case, I just resend the email and roll the dice again.

I don't believe this is Joe B's only job (at least I hope not), so it does not hurt to be persistent.

a