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TimestampNameComment
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5/14/2015 23:01:15ThomasLeave a comment! Let me know what you think!
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5/16/2015 9:31:23DVery nice! Cool idea! The air brake is a great method of controlling the rocket's apogee.
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5/16/2015 9:32:17ThomasThanks!
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9/28/2015 10:38:23Diego OspinaHi, i am curious if you could teach me how you were able to program the micro controller to know, when it needed to deploy the air break system
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10/1/2015 14:16:20ThomasHi Diego! A good start to learning how to program the micro controller is reading my ABDS Paper posted above. There is an entire section dedicated to the programming of the micro controller. If you have any questions after reading the paper, I can help you out from there. Thanks for asking, and good luck!
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11/12/2015 10:56:41tomThat Air Brake is ingenious, were there many other entries at TARC that tried autonomous controls?
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11/16/2015 11:34:59ThomasHi Tom,

Thank you! Last year at Nationals I am aware of only two other teams that used autonomous controls. There may have been more, but I only saw two.
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12/9/2015 8:28:42tomcould you have used a 5V arduino pro mini, so more voltage could be applied to the servo? or would that have fried the BMP180?
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12/12/2015 22:49:34ThomasHi Tom,

Yes, I could have used a 5 volt Arduino Pro Mini with both the BMP180 and the Micro SD card reader without frying either one. This would in turn provide the servo with more power. One thing to note is that most BMP180 sensors on the market are only 3.3v compatible; however, I bought mine through Adafruit. Adafruit makes their own BMP180 with an internal voltage regulator, so either 5 or 3.3 input voltage can be used.

The reason I did no use a 5 volt Arduino Pro Mini was my battery. The battery I used (3.7volts) did not provide enough volts to run the 5 volt Arduino. So, I instead used the 3.3 volt Arduino.
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12/21/2015 15:34:06tomdid you download the software to run the BMP180 so it would tell the arduino the correct altitude, or did you write it from scratch?
I'm relatively new at coding.....
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12/30/2015 9:29:29ThomasHi Tom,
Yes, I did download the software to run the BMP180. I used the tutorials and Libraries available on Adafruit to create my base program.
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2/4/2016 10:27:46tomdid the arduino internal clock start the timing by first sensing an altitude change?, or did you use a mechanical device, like a wire, to start the clock?
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2/5/2016 11:17:51FrankI really like your design and can you share your 3D design file of parts with me.
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2/7/2016 13:40:33
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2/7/2016 15:28:12ThomasHi Tom, the Arduino's clock started after sensing an initial altitude change. Other altimeters, like the TARC PNUT do the same, they begin after some initial altitude change.
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2/7/2016 15:33:05ThomasHi Frank,
Thank you, I am glad you like the design. At the current time, I am not releasing the CAD files for the ABDS. You are more than welcome to design your own though. Thanks!
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3/3/2016 21:02:37Diego OspinaThank you for the replay, I did read through the paper and I have design an airbrake of my own, I am using the same equation you are using to project the altitude, one question I have is the A. vehicle is that just the piR.quare so If my rocket has a 5.5 inch diameter would that just be pi(r/2)^2.
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3/19/2016 5:36:37Megan SunHi Thomas,
Though this type of science is not my cup of tea and I did not necessarily understand everything that was on this site, I was extremely fascinated by the air brakes and how they worked.
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3/20/2016 22:10:03ThomasHi Diego,
That is fantastic to hear that you have an air brake design! Would you be willing to email me pictures?

When it comes to calculating the Area of the rocket, it is going to be based of the the rocket's diameter. So, if you have a 5.5 inch diameter, the area would be: pi*(5.5/2)^2. The general area formula is: pi*(Diameter/2)^2 or pi*(Radius)^2.
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3/20/2016 22:25:34ThomasHi Megan,
Thank you! I am glad you liked the air brakes.
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5/26/2016 13:39:44KevinReally cool project. What kind of 3D printer did you use so that you could print threads?
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5/27/2016 1:54:31ThomasHi Kevin,
Thank you - I am glad you liked the project! The 3D printer I use is a Maker Gear M2. To ensure the threads have a nice fine resolution, I print them with .1mm layer height.
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10/24/2016 21:10:53SpencerDid you have any issues with the air brake system interfering with the stability of your rocket?
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10/25/2016 13:07:59ThomasHi Spencer,
That is a great question. In fact the affect the ABDS would have on the rocket's stability was a major design concern when we first tested it.
From my experience and testing of the ABDS, the ABDS does not have any (noticeable) negative affects on the rocket's stability. Theoretically, the ABDS could cause stability issues, since when the flaps open, the Center of Pressure (CP) would move toward the nose of the rocket. This would decrease the distance between the CP and Center of Gravity and therefore would decrease the rocket's stability. However, I have never observed any physical signs of this actually occurring.
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4/15/2017 1:10:35RickyHi Thomas,
I am looking into doing something similar for a larger rocket but I am relatively new at Arduino and am having trouble programming the flaps. I read your ABDS paper and I was wondering if you had a sample of the code to see how you plugged in the formula.
Thanks!
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4/15/2017 9:55:00ThomasHi Ricky,
I am excited to here that you are working on something similar - best of luck! At the current time, I have not released the entirety of my code, however here is what the formula looks like in arduino:

altitude_Projected = altitude + ((velocity_Current * velocity_Current)) / (2*((GRAVITY)+((.44*((1.2*(velocity_Current*velocity_Current))/2)*.003))/rocket_Mass));

In the above equation, the ".44" is my rocket's experimentally found Drag coefficient and the ".003" my rockets area (when looking down on the nose) in meters squared. So these will need to be adjusted to fit your rocket.
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9/28/2017 23:37:43SamirHello Tom,
I wanted to ask, when you mention the cross sectional area of the rocket in your formula, do you only include the pi*r^2 of the rocket or do you also include the rectangular area of the flaps when fully deployed.
Regards,
Samir
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9/30/2017 22:51:00ThomasHi Samir,
In my formula, I only use the pi*r^2 of my rocket's frontal area. I did not try to include the rectangular area of the flaps as they extended. It was not necessary for my application to include the rectangular area of the flaps; however, adding the area of the flaps (as a function of distance extended) may actually improve the accuracy of the algorithm.
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1/10/2018 15:29:36KaiHello Tom,

Have you changed your status on releasing the 3D design files? I'm very interested in your design. It will be used mostly for testing purposes.

Thanks!
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1/16/2018 16:12:07ThomasHi Kai,
Thank you for the interest in my design! At the current time, unfortunately, I am not planning to release the CAD files for my design. However, my paper details the design, via pictures, of the entire ABDS. Feel free to take as much inspiration from my design as you would like. If you have any further questions, don't hesitate to ask!
Best of luck,
_Thomas
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6/2/2018 21:56:04MyBlueMarsGreat design and superb documentation. My son and I are gearing up for level 1 certification and we are inspired by your presentation here!

Regards,

Matt & Dan
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6/15/2018 18:31:08ThomasHi Matt & Dan,
Thanks! Good luck with your level 1 certification!
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9/26/2018 10:53:06SkyHi Thomas,
First, I would like to know how much the complete system weighed? Second, do you recall how many feet above target altitude the rocket needed to fly to be able to reach altitude with brakes in various conditions?
Thanks,
Skyler
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7/17/2019 17:07:17Larry J.Hi Thomas,
I am a TARC participant looking into use of an airbrake. Good work on your project! I was wondering about the compatibility of such a system with TARC rules: the handbook says "Rockets must contain one and only one electronic altimeter of the specific commercial types approved for use in the
Team America event. These types are the Perfectflite APRA, or Pnut. ", yet you used a barometric pressure sensor to detect altitude. I am looking into creating my own system, possibly TVC, but I am struggling to find a way to measure altitude without a pressure sensor.
Did you have any trouble with your sensor? Did anyone at TARC say anything about it?

Thank you,
Larry
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7/21/2019 20:14:59ThomasHi Larry,
Thank you - it was a fun project! That is a great question. I used a barometric pressure (BMP180 breakout board) sensor in my design and TARC did not have any issues with it. My team and I used the ABDS at TARC nationals and the officials never said anything about it. I did contact TARC to confirm that the ABDS was legal to use in the TARC challenge and, at the time, was given approval. I would suggest contacting TARC and verifying that your project would be legal (as it has been a few years since I did mine). Good luck with your airbrake!
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10/29/2019 15:16:02Logan EvansI was review the equation that you were using to project the apogee of the rocket. How did you determine the current velocity? I am guessing that you are assuming a vertical launch and didn't take any angles into account.
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11/3/2020 16:04:11WellingtonHi Thomas, great project! I was wondering if you could point me in the direction of the derivations for the equations you used on the Arduino? Any literature or sources would be appreciated?
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11/11/2020 20:13:19ThomasHi Wellignton, thank you! Great question - I actually had been wanting to post a better explanation of the equation, so shared above on this webpage is a new document which contains the derivation of the equation used in this project. I hope that helps.
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11/30/2020 20:12:55Andrew How did you know the position of the continuous servo, so that it can stop at some limit? Encoder?
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11/30/2020 21:32:24Andrewhmmm did you use a timed limit by any chance? Like if it was rotating at some constant speed it would add time until it hit a limit in this case 9000, then if it reverses it would subtract the time until it hit 0 again then stop. If so how accurate was this? -Thanks in advanced
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12/1/2020 22:21:18ThomasHi Andrew,
Great question. When I did it, I just used time in the exact method you mentioned. I never had trouble using time; however, I did have to make sure to manually setup/reset the ABDS manually before each test or flight. Using an encoder would be a nice improvement to the design.
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1/23/2023 14:59:33SergeiHey, I really liked your airbrake design and I'm wondering if you could share the 3d model with me. I am an amateur looking into model rockets and I find the concept of airbrakes fascinating. Any help would be greatly appreciated.
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1/24/2023 21:49:41ThomasHi Sergei,
It's great to hear about your interest in air brakes and model rocketry!
As for the 3D models, at this time they are not available. However, feel free to use the information in my paper (posted on this page) to make and design your own!
For designing rockets, there are tons of great online resources and free simulation tools (such as OpenRocket) to help you design your own model rocket. Happy flying!
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3/13/2023 15:48:04AbdulFor the air brake system, how did you know when to deploy the brakes to reach the target altitude for TARC? Did you use the projected altitude formula and adjusted the flap angle to ensure that the calculated altitude is the target altitude?

Also, how did you measure the drag coefficient for the rocket?
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3/14/2023 23:13:55ThomasHi Abdul,
Yes - I used the projected altitude formula to adjust the flap angle. Example: if the projected altitude formula calculated that the projected apogee was greater than the target altitude, the flaps would start opening. If the projected altitude was lower than the target altitude, the flaps would close.

To determine the drag coefficient of the rocket, I used the simulation software Open Rocket.
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6/4/2023 12:36:12Drew StephensWhat type of filament did you use to print the mechanisms? I'd think something like ABS or PETG would be needed.
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6/5/2023 21:22:37ThomasHi Drew,
At the time, I used mostly ABS - since it tends to be stronger than PLA. However, PETG would likely be fine as well.
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8/15/2023 12:58:06Drew StephensHi. I have two questions for you. One, does cross-sectional area vary with the position of the airbrake fins? Two, if a rocket had an upper section that housed the airbrake of a thinner diameter than the bottom section, an engine section, do you think it would have a major effect on the equation's efficacy, or do you think it would still provide a reasonable estimate? Thank you for your time and wonderful documentation.
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8/26/2023 21:27:04ThomasHi Drew,
1) When I originally used the equation (in the above posted Addendum) I did not account for the variation in cross-sectional area of the rocket due to the change in air brake position. However, it would likely improve the accuracy of the apogee estimation if it was.
2) I believe that using the larger of the two diameters as the representative rocket cross-section would still provide a reasonable estimation.
I am glad to hear the documentation is helpful - happy flying!
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