What to watch out for? (Rocket Flight Computer)

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Hello, thank you for your time. We are building a rocket for an upcoming rocketry contest. We want to prepare for every possible problem in the avionics department. If you could list some of the problems you can think of down below that would be much appreciated.

If possible please leave links to sources we can research this.

We are using:
Arduino x2
BMP
GPS module
MPU x2
2 channel 5V relay module
9V duracell alkaline batteries
Communication module
sd card module
 
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FredA

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I see a problem - you are not using an off the shelf, proven system.
Why are you designing your own?
Unless it's a requirement of the contest, it's a mistake.

So - please explain what you are trying to accomplish that can't be done today, off the shelf.
What problem are you trying to solve?
What are the unmet requirements?
 

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The contest gives us extra points if we design our own flight computer. Also the off the shelf flight computers are expensive here. (They have to be imported.)
We don't exactly have problems yet. The point of our research is finding potential issues that may occur during the flight. If you can think of any problems that would occur in a flight computer please let us know.

By the way we have our avionics department made of 6 members in the rocket team.
 

FredA

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So - please explain what you are trying to accomplish that can't be done today, off the shelf.
What problem are you trying to solve?
What are the unmet requirements?
You still haven't said what all this HW is doing for you.....I'll assume nothing more than deployment.

First -- rockets are not cheap - I can't imagine importing a $50 stratologger or equivalent is out of your budget -- how much are you paying for all the parts? What is the at-risk value when your [first] design fails and you crash the rocket? I read the "more points" bit, but is this the place to get those points - nearly every team leaves "points on the table" by wisely choosing which parts of the competition to tackle.

Second - what are your goals for the above long list of HW? What are you trying to do?

Third -- ditch the relays -- few, if any are flight worthy. They have no place in a high-G, high-vibration environment.

Fourth - if you really intend on rolling your own, why not start with cloning an open-sourced product? Google is your friend.
 

heada

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Have you looked at the Teensy 4? Much smaller, much faster, bigger memory area (for both programming and data storage) compared to the Arduino Mega or the Nano. Also, have you looked at the BNO055? It combines accelerometer, magnetometer and gyroscope into a single package that also outputs quaternions, Euler angles or vectors. And has been said, rather than use a relay, there are MOSFETs capable of switching high power that would be better options.
 

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You still haven't said what all this HW is doing for you.....I'll assume nothing more than deployment.

First -- rockets are not cheap - I can't imagine importing a $50 stratologger or equivalent is out of your budget -- how much are you paying for all the parts? What is the at-risk value when your [first] design fails and you crash the rocket? I read the "more points" bit, but is this the place to get those points - nearly every team leaves "points on the table" by wisely choosing which parts of the competition to tackle.

Second - what are your goals for the above long list of HW? What are you trying to do?

Third -- ditch the relays -- few, if any are flight worthy. They have no place in a high-G, high-vibration environment.

Fourth - if you really intend on rolling your own, why not start with cloning an open-sourced product? Google is your friend.
First:
(I had to change some names for privacy reasons.)
Excuse me for explaining the budget in my local currency. 1 USD before the recent events was sub 6 Turkish Liras (Now its reaching 7). So a 50 dollar stratologger would be 300 liras. The communication module is given to us by a sponsor so that's free and hopefully we might get some of other for free as well. Compact Arduino is sub 70 Liras, small Arduino is around 20 Liras (we need 2 of it 1 for the nosecone computer and 1 for the backup computer), pressure sensor is around 25 Liras, IMU is around 9 Liras, GPS module is around 50 Liras (we need 2 of it 1 for the nosecone computer and 1 for the main computer) and at last Relay module is around 10 Liras, and i forgot to mention SD Card module it is around 5 liras. So that costs around 43 dollars but with bits and bobs the cost might get to 50 dollars. We are building 2 rockets so that's 100 dollars.

Second: The flight computer will deploy the drag and main parachute at the right times via relays (Relays are used to control the 9V supply for the igniter.). The pressure, altitude, location etc. data will be written to an SD Card (Black Box of the rocket). The computer will also send these to a ground computer that also we will set up so that we can find the rockets location after it safely lands or god forbid crashes.

Third: We can not ditch them unfortunately because Arduino can't give an output voltage higher than 5 Volts. But thank you for this specific information this really might save us from a crash.

Fourth: I did not understand what you meant here. Are you saying that i should do research outside here? If yes, we already are doing that. We just wanted to benefit from your experience.
 
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Have you looked at the Teensy 4? Much smaller, much faster, bigger memory area (for both programming and data storage) compared to the Arduino Mega or the Nano. Also, have you looked at the BNO055? It combines accelerometer, magnetometer and gyroscope into a single package that also outputs quaternions, Euler angles or vectors. And has been said, rather than use a relay, there are MOSFETs capable of switching high power that would be better options.
We are working on ARM development boards but probably wont be ready for this year. Thank you ever so much for the suggestion about the MOSFET.
 

heada

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We are working on ARM development boards but probably wont be ready for this year. Thank you ever so much for the suggestion about the MOSFET.
The Teensy4 can be programmed in the Arduino IDE with standard sketches. No need to do anything special because it is ARM based.

https://www.pjrc.com/store/teensy40.html
https://www.pjrc.com/teensy/teensyduino.html

Example of a MOSFET that can switch higher power is the RFP30N06LE. It can switch up to 60V and 30A (assuming proper wiring and heat sinking) and since it is a logic level MOSFET, microcontrollers like Arduino can switch it directly.
 
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It would help if we knew what motor you plan on using, the estimated weight of the rocket, the diameter of the rocket and your target altitude. That would give us an idea of the forces involved.

The Stratologgers have a capacitor on them which helps maintain power to the altimeter in case there is a brief disruption of power during the flight. I believe the capacitor can provide 1.5 seconds of power to the altimeter. Your rocket will likely experience a high G liftoff and other stresses during your flight. You should consider adding a capacitor to your design to be safe.

Commercially made altimeters also filter out bad data to prevent ejection charges firing at the wrong time.

For safety reasons you also need a way to turn on your altimeter/recovery system AFTER the rocket is on the launch pad and ready to go. Here in the US the standard practice is to put the rocket on the pad pointing up. Activate the electronics and verify that everything is working properly. The last thing we do is insert the motor igniter. Also, minimize the number of people preparing the rocket on the pad. You also want a way to turn off your altimeter/recovery system after the flight in case some of your ejection charges did not fire.
 
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FredA

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So - to save $50ish, you're going to do a ton of development and take on added risk....is this smart. Rockets are not for the poor.

E-matches (for deployment) are current mode devices - you don't need any voltage to push the 1A all-fire current though their approximate 1-ohm resistance.

There are "published" open-source designs that do what you want to do. Why re-invent the wheel? Why take the risk? The questions you are asking are evidence you've not found these.
 

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It would help if we knew what motor you plan on using, the estimated weight of the rocket, the diameter of the rocket and your target altitude. That would give us an idea of the forces involved.

The Stratologgers have a capacitor on them which helps maintain power to the altimeter in case there is a brief disruption of power during the flight. I believe the capacitor can provide 1.5 seconds of power to the altimeter. Your rocket will likely experience a high G liftoff and other stresses during your flight. You should consider adding a capacitor to your design to be safe.

Commercially made altimeters also filter out bad data to prevent ejection charges firing at the wrong time.

For safety reasons you also need a way to turn on your altimeter/recovery system AFTER the rocket is on the launch pad and ready to go. Here in the US the standard practice is to put the rocket on the pad pointing up. Activate the electronics and verify that everything is working properly. The last thing we do is insert the motor igniter. Also, minimize the number of people preparing the rocket on the pad. You also want a way to turn off your altimeter/recovery system after the flight in case some of your ejection charges did not fire.
It's a contest and we can't give any other information we shouldn't have given information about the names of the sensors anyway (i might delete the post). All we are trying to find out is what to watch out about in the avionics subject.
 

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So - to save $50ish, you're going to do a ton of development and take on added risk....is this smart. Rockets are not for the poor.

E-matches (for deployment) are current mode devices - you don't need any voltage to push the 1A all-fire current though their approximate 1-ohm resistance.

There are "published" open-source designs that do what you want to do. Why re-invent the wheel? Why take the risk? The questions you are asking are evidence you've not found these.
Yes sure rockets are not for the poor but we can not spend a fortune on a 1500m sounding rocket. The contest gives us extra points for our own design and we just wanted to learn development of these kinds of tech.
 

cerving

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I work with several colleges on a recurring basis, a good strategy is to use an off-the-shelf altimeter for parachute deployments, an off-the-shelf tracking system to get your rocket back, and roll your own for the extended real-time telemetry. If you have a problem with your hardware/software, it's not going to result in your rocket coming down ballistic, or getting lost because you don't know where it is. Trust me, it's not as easy to get those parachutes out as you might think... I tested the original Eggtimer for over a year before it was released, logging over 100 dual-deployment flights.

As far as what to "watch out for" with your own system, there have been several threads on that subject... search for "arduino" or "kalman" in this forum, you'll turn up a lot of good material.
 

Rob702Martinez

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It's a contest and we can't give any other information we shouldn't have given information about the names of the sensors anyway (i might delete the post). All we are trying to find out is what to watch out about in the avionics subject.
First:
(I had to change some names for privacy reasons.)
For a school related project this sure sounds fishy. What is there to hide? Where is the information of said competition posted?
 

rharshberger

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I work with several colleges on a recurring basis, a good strategy is to use an off-the-shelf altimeter for parachute deployments, an off-the-shelf tracking system to get your rocket back, and roll your own for the extended real-time telemetry. If you have a problem with your hardware/software, it's not going to result in your rocket coming down ballistic, or getting lost because you don't know where it is. Trust me, it's not as easy to get those parachutes out as you might think... I tested the original Eggtimer for over a year before it was released, logging over 100 dual-deployment flights.

As far as what to "watch out for" with your own system, there have been several threads on that subject... search for "arduino" or "kalman" in this forum, you'll turn up a lot of good material.
And one of your Quark kits would give them a cheap and reliable altitude and deployment only altimeter so that they could safely recover their home-built Telemetry and deployment system, they could even use the Quark as a back up to their DIY system that way they get everything back if the DIY fails to do its job.
 

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For a school related project this sure sounds fishy. What is there to hide? Where is the information of said competition posted?
Team leader told us to keep it a secret. It might not be much but we don't want to give other teams our information.
 

K'Tesh

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One thing I can think of is to make sure that your batteries are fresh, and that they don't move during flight. One problem I have with some products (bike lights/flashlights)(not rocketry related) is that even "off" the batteries drain suspiciously fast and I occasionally will find them on even though I haven't touched them for some time.

The movement issue is to make sure that they don't come loose and bang around inside the AV bay and damage something, or somehow get disconnected from power.
 

David Schwantz

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You also have to build all of the Eggtimer stuff. That should give you the extra points you are looking for.. I have lots of eggs. They all work great!!!
 

FredA

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Somehow we [the hobby] should get a handle on [eliminate] these competitions that incite inexperienced people to make and fly their own deployment computers without proper validation.

They almost never work.
They are dangerous to people, property and reputation.

I've mentored a bunch of college teams.
Many make their own and I've seen few, if any work.
Most just cause scrubbed launches and waste a ton of time and goodwill.
Some go poorly.

I'll never forget one instance.
I was helping a team launch their rocket.
It was a home-built full up tracking/telemetry/deployment system - built by a big team of EE students (about a dozen) and LOOKED pretty spiffy.
They had the usual stumbles getting it on the pad and reporting readiness that wasted most of the day.
Finally, late in the day, they pushed the button.
They had maybe 30 students on site to "watch" - they launched and ALL were under their EZ-UP staring at their laptop's calling out telemetry.
I was watching the rocket.
Shortly after they called out apogee deployment, I blew the heads up horn.
The rocket was coming in HOT despite what their telemetry told them.
None of the team saw the rocket in the air.

All contests should require deployment be controlled by a proven flight computer.
IMHO.
 

Nytrunner

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Somehow we [the hobby] should get a handle on [eliminate] these competitions that incite inexperienced people to make and fly their own deployment computers without proper validation.
Not sure how much influence we as the hobby have on Turkish university competitions
 

Maxwelljets

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I'm about 95% certain that the OP is talking about the turkish rocket competition. Details can be found here.

If you're upset about teams being asked to make their own deployment avionics, rather than berating this team, your time would be better spent contacting the people who organized the competition.
 

curtisheisey

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First of all, you should use a proven commercial flight computer as a back up.

Second, don't underestimate the difficulty in building and debugging both the hardware and software, as well as the time and number of test flights involved. There are lots of corner cases that you will have to consider and account for. You will need to do lots of test flights and will likely have a number of lawn darts in the process. Don't expect to build a flight computer, throw it in the rocket, and have it work as expected the first try.

Before you incorporate firing of deployment charges, I would recommend first just flying the flight computer as a data logger a few times.

You can do a lot of development and test flights on lower powered motors.
 
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mikec

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We can not ditch [relays] unfortunately because Arduino can't give an output voltage higher than 5 Volts.
The way all commercial altimeters work is to use logic-level MOSFETs where the gates can be enabled by 5V or 3.3V to switch the higher-voltage battery voltage to the initiators. You certainly don't need mechanical relays.

Obviously you need to ground test and fire your channels with real charges to make sure that battery sag doesn't cause your electronics to brown out. All commercial altimeters have big capacitors to protect against this.

If you can't fly to test, with a proven backup, you should at least rig up a simple vacuum chamber to do end-to-end testing of your barometric sensing and deployment events.

I tend to agree that these contests could be defined better to reduce the risk of bad outcomes.

And always remember, if it's not 100% rock solid on the bench in the most realistic test you can manage, it will not work in flight, guaranteed.
 

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Yes sure rockets are not for the poor but we can not spend a fortune on a 1500m sounding rocket. The contest gives us extra points for our own design and we just wanted to learn development of these kinds of tech.
Curious, how many extra points as a percentage of the total available do you get for a scratch design electronics?

How many points do get for a successful recovery?
 

cerving

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Honestly, the total score should be ZERO if you don't get it back. That's how important a successful recovery is...

As I said before, at the very least use a commerical altimeter as a backup. It doesn't even have to be one of ours. :) There's very little in rocketry more dangerous than a rocket coming in ballistic and you don't know where it is.
 

FredA

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rather than berating this team, your time would be better spent contacting the people who organized the competition.
This is not about this team -- it's maybe a thread hyjack -- we, the hobby, need to do everything we can to discourage home-made, un-validated deployment electronics being in control. Period.

Me reaching out to an unknown contest is a fruitless notion.
Us as a hobby posturing to educate against this practice and not enable these flights are things we can do.
 

Maxwelljets

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We, the hobby, need to do everything we can to discourage home-made, un-validated deployment electronics being in control. Period.
I agree with this, mostly. If a blanket ban goes into effect, new altimeter development will grind to a halt, since most of the people who make the current altimeters are doing it as a side project.

Me reaching out to an unknown contest is a fruitless notion.
I strongly disagree here. If enough people contact them, explain why they're qualified to make this call, and explain why it's a bad idea, there's a good chance they'd change the rules.
 

jderimig

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I agree with this, mostly. If a blanket ban goes into effect, new altimeter development will grind to a halt, since most of the people who make the current altimeters are doing it as a side project.
.
I think FredA agrees with you. I think he is against things like contests with some well intentioned rules that encourages hazards.

The rule could have been written that a commercial alimeter must be used as a backup and if you can show your team designed electronics worked as designed you get the points.

Also, the above IS the SOP for any new altimeter development (or it should be).
 

FredA

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a blanket ban goes into effect
Not talking about ride-along's.....development continues, just not in control until some level of validation is complete - if you've ever mentored a college team you would know that [from what I've observed] most teams fly their full-scale ONCE before going to the competition.
ONE FLIGHT.

I strongly disagree here. If enough people contact them, explain why they're qualified to make this call, and explain why it's a bad idea, there's a good chance they'd change the rules.
OK - you first......
 

Maxwelljets

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The rule could have been written that a commercial alimeter must be used as a backup and if you can show your team designed electronics worked as designed you get the points.

Also, the above IS the SOP for any new altimeter development (or it should be).
I wholeheartedly agree, and is what I am pushing for. This strikes the best balance of safety without restricting teams too much. Get too safety conscious and you just ban everything that might have a chance of challenging the teams.

If you've ever mentored a college team you would know that [from what I've observed] most teams fly their full-scale ONCE before going to the competition.
ONE FLIGHT.
I fail to see what that has to do with altimeter development. The college teams I have worked with/spoken to/participated on have typically performed many test flights during the year on non-competition rockets, to test things like custom flight computers (logging only, no deployment) or any other experimental subsystems. Why risk the entire competition vehicle just to test out a new sensor or parachute design.

And as a side note, the vast majority of BALLS projects don't even get test flown once.

I just don't think we should be faulting teams like this one who are trying to follow the rules laid out by the competition.

OK - you first......
Why do you assume I haven't already.
 
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