I could use just a little guidance

[CoyoteNumber2]

The program for this flight was to launch vertical, turn immediately to a 15° tilt (at a bearing of 0°), change to a bearing of 20° at 6.2 seconds (still at 15°), and then go back to vertical at 12.2 seconds.

Is 0° relative to the rocket's heading at launch? Or relative to 0° due north?

Badass stuff, by the way.

 

[JimJarvis50]

Is 0° relative to the rocket's heading at launch? Or relative to 0° due north?

Badass stuff, by the way.

It's 0° relative to the initial position of the rocket on the pad. The control system doesn't have a compass. I just say north/south so that the flight is easier to visualize.

Jim

 

[JimJarvis50]

Well, Crap! I flew my stabilized rocket over the weekend at the TNT Texas Shootout. This flight was in the two-stage configuration. It was a K2050 in the booster to get things moving followed by an L395 long-burn motor in the sustainer. The sustainer didn't light (it spit the igniter due to mostly operator error). It was going to be a fun flight, too. Here's a video clip of the flight, such as it was. Also, here's a video clip of the flight program. I'll leave it as an exercise for the reader to figure out what we were up to. The good news is that everything recovered just fine - just have to glue various fins back on the rocket - so I'll try it again before too long.

Jim

 

[Arpak]

I'll leave it as an exercise for the reader to figure out what we were up to.

I'll keep your secret if you promise to try it again sometime

-Patrick

 

[Finicky]

Awesome attempt Jim. When in doubt, add more pyrogen

Sorry if you've been asked this before, but what camera are you using ?? I love the torpedo shape.

 

[JimJarvis50]

I'll keep your secret if you promise to try it again sometime

-Patrick

You might get to see it ....

Jim

 

[JimJarvis50]

Awesome attempt Jim. When in doubt, add more pyrogen

Sorry if you've been asked this before, but what camera are you using ?? I love the torpedo shape.

View attachment 467035

It's called a Replay XD 1080 mini. The torpedo shape is something I added (a nose cone basically).

Jim

 

[WoShuGui]

Is the sustainer fin can rotating Independent of the airframe?

 

[JimJarvis50]

Is the sustainer fin can rotating Independent of the airframe?

Yes, it's one of my two spin cans. The purpose of them is to avoid "control reversal". The canards on the top of the rocket can cause voticies that hit the lower fins and turn the rocket in the wrong direction. The spin can prevents that. This video shows the design.

Jim

 

[jmwoody]

Howdy Jim

Thank you for joining us and flying your great rockets at the TNT Texas Shootout this past weekend. I had the pleasure and honor to RSO your rocket Saturday ... very cool sir .... well done! I'm looking forward to visiting with you again at our next launch

John

 

[JimJarvis50]

Howdy Jim

Thank you for joining us and flying your great rockets at the TNT Texas Shootout this past weekend. I had the pleasure and honor to RSO your rocket Saturday ... very cool sir .... well done! I'm looking forward to visiting with you again at our next launch

John

Thanks John. I think the Shootout is only going to grow over time. It's great that TNT has two good fields now.

So, the stabilized flight didn't go quite as planned, but the two-stager that you laid hands on did a bit better.

Jim

 

[Arpak]

Thanks John. I think the Shootout is only going to grow over time. It's great that TNT has two good fields now.

So, the stabilized flight didn't go quite as planned, but the two-stager that you laid hands on did a bit better.

Jim

Details! What motors?

 

[JimJarvis50]

Details! What motors?

This was just my well-worn purple two-stager. Has probably a couple dozen flights on it - built maybe 15 years ago - but it just keeps coming back. It can fly up to 25K with maximum motors, but this flight was just a J-760 to I-120 to around 6K. Very pretty flight though.

The last time I flew the rocket was back in June 2020, also at Seymour. The sustainer motor cato'd, so that part of the rocket was rebuilt prior to this flight. I"ve had it prepped for months, but we haven't had a suitable day to fly it, so I took it to the Shootout.

Jim

 

[JimJarvis50]

So, last month, I tried my "Infinity Squared" flight at the Tripoli North Texas Seymour launch. The sustainer didn't light (my fault). This weekend, I got to try the flight again at the Tripoli Houston South Texas site. The flight went quite well. The booster motor was a K2050 (to get the rocket moving) and then an L395 long burn (12.5 seconds) in the sustainer for some aerobatics. The flight program was to fly vertical until 4 seconds, turn to a 7.5° tilt between 4-6 seconds, fly two "infinity signs" while at the 7.5° tilt, and then return to vertical at about 22 seconds. Pretty much all of that happened. I'm still looking over the data and cleaning up all of the rocket parts, but I'll post some data when available. In the meantime, enjoy the flight of Infinity Squared!

Jim

 

[Finicky]

Outstanding !!!

 

[Finicky]

Just curious if the 2nd stage velocity flatlined because of the long, slow burn ?

 

[JimJarvis50]

Just curious if the 2nd stage velocity flatlined because of the long, slow burn ?

Well, it didn't exactly flatline. The booster gets the speed to about 150 ft/s and then it rises to about 700 ft/s approaching apogee. Counting the descent, the motor provides over 25 seconds of useful time for moving the rocket around (except that the smoke grain burns out before that). But the booster has to be used to get the rocket off the pad because the long burn motor doesn't provide enough thrust to do that. The flight program considered the velocity of the rocket versus time and the turning rate as a function of velocity (from prior flight data).

A few months ago, I made some changes to the spin can so that it worked better under thrust. Then, I saw this motor. Hmmm.? Bill created a way to add up to 100 bearing/tilt changes to the flight program and we just thought a little about what to do with the time.

Jim

 

[bad_idea]

Jim, while we missed seeing the aerobatics at the Shootout, it was an education and a pleasure to help you haul the most interesting rocket in Texas out to the pad. Great to see that you got it back in the air and that it worked exactly as you planned.

 

[JimJarvis50]

Jim, while we missed seeing the aerobatics at the Shootout, it was an education and a pleasure to help you haul the most interesting rocket in Texas out to the pad. Great to see that you got it back in the air and that it worked exactly as you planned.

Thanks! Yep, it was nice to get it in the air and that the sustainer lit this time. You might notice that the sustainer lite INSTANTLY. It's a complex flight and at some point, it needs to work! Your help at the shootout was very much appreciated and I'm glad you get to "see" it too.

Jim

 

[Arpak]

You might notice that the sustainer lite INSTANTLY.

Sad no sustainer ignition noises

 

[JimJarvis50]

Sad no sustainer ignition noises

I feel your pain. Did you determine what happened?

Jim

 

[Arpak]

I feel your pain. Did you determine what happened?

Jim

Haven't had the time to pull the data from the altimeters yet, although it's either programming, continuity within the altimeter, or another possibility I thought of was maybe the breakaway cable disconnected after the separation charge.

 

[BABAR]

Congrats. I think you would have photodocumented your namesake if not for some wind and a pesky cloud!

 

[JimJarvis50]

So, here's some of the data from the flight. It's mostly things that are probably of interest only to me, but here goes.

This first photo shows the gps trajectory. There is a similar trace from the pad cam that confirms that the gps trace is indeed correct. The main conclusion from this is that the wind at altitude really messes with the intended ground path. Fortunately, there is a smoke column that drifts with the wind so that the flight path can be seen. Otherwise, it would be hard to figure out what happened.

Jim

 

[JimJarvis50]

This second photo shows the X and Y feedback values for the "program" shown in the video and for the actual flight. These are the values that are then converted into the actual canard movements. In the video, the "program" was run with the rocket vertical on the bench. That generates one set of feedback values. In the actual flight, however, the position of the rocket, and therefore, the "directions" to the next orientation, are completely different than the bench depiction. Generally speaking, the canard movements in the flight were less than that for the bench version.

Jim

 

[JimJarvis50]

This third photo shows the bearing rate changes in the flight. When I set up the program, I looked at prior flights and learned that at a velocity of 600 ft/s, a moderate change in the position of the canards would move the rocket at a rate of about 12.5 °/s. When the rocket is at a tilt of 7.5°, the actual change in the flight angle to change the bearing by 30° is 3.75°. Thus, the time I allowed for a change in the bearing would be 3.75 / 12.5 = 0.3 seconds. So, the timing of the bearing changes was 0.3 seconds at high velocity and up to 0.5 seconds at lower velocities before and after apogee. I actually flew the rocket with larger canards than in most of the test flights and at a slightly higher gain. It looks like from the data that the rocket often moved faster than 12.5 degrees and then got to a rate of zero prior to the next directed change in the bearing. I had expected that the bearing might lag behind the directed changes a little, but the rocket moved as would have been expected from the original analysis. The "feedback" graph in the previous photo shows that the canards never reached their maximum positions (a value of 500 on the graph). Overall, the results suggest that it would be possible to move the rocket around at about twice the rate of this flight without the system reaching limitations in it's capability.

Jim

 

[JimJarvis50]

This fourth graph shows the X and Y vert values (i.e., where the rocket thinks it is with respect to yaw and pitch). Also shows are the tilt values from the control system (the UDB5) and the EasyMega. It always surprises me how well they tend to agree.

The data show that the rocket reached it's 7.5 degree target, but towards the end of the flight, the flight angle dropped off. Not sure why that happened.

Jim

 

[JimJarvis50]

This fifth graph shows the acceleration values during the flight. The Y acceleration shows the thrust of the mightly L395 motor (about 3 G's), and that the turns were being executed at nominally 3G's. I suspect it would not be a good idea to increase those acceleration rates too much further (would need a stronger rocket than the "Test Rocket").

Jim

 

[JimJarvis50]

This sixth photo shows the gyro values. This is interesting data. The control system includes a heading hold feature that keeps the rocket facing the same general direction through the flight. You can see that in the video. When the bearing changes (in 30° increments, but at actual angle changes of 3.75°), the rocket has to roll slightly to be "looking" in the original direction. So, there is a roll rate associated with each change in the bearing. The maximum roll rate for the chip is set at 1000°/s, so the flight is withing the capability of the chip, but this might limit more aggresive flights.

Jim

 

[steveh.jae]

Yes, it's one of my two spin cans. The purpose of them is to avoid "control reversal". The canards on the top of the rocket can cause voticies that hit the lower fins and turn the rocket in the wrong direction. The spin can prevents that. This video shows the design.

Jim

Thank you Jim! That is a very informative video.