Ground Testing Avionics and Recovery Gear.
Ground testing mid and high-powered rockets when using new avionics or recovery gear is crucial for several reasons:
- Safety: The primary reason is safety. Rockets can reach high altitudes and velocities, and any failure in the avionics or recovery systems can lead to dangerous situations, including property damage, injury, or even fatalities. Ground testing helps identify and rectify any issues before the actual flight.
- Functionality Verification: Ground tests verify the functionality of the new equipment. It's essential to ensure that the avionics perform as expected under simulated flight conditions and that the recovery systems (like parachutes) deploy correctly.
- System Integration: Testing helps assess how the new components interact with the existing systems. Sometimes, new components might not integrate seamlessly with the existing systems, leading to unexpected behaviours during flight.
- Data Collection: Ground tests can provide valuable data to predict the rocket's performance and make necessary adjustments. This data might include deployment timing, battery life, signal strength, and sensor accuracy.
- Regulatory Compliance: In some regions, certain tests might be required by law or by the guidelines of rocketry organizations to ensure compliance with safety standards.
Methods of Ground Testing:
- Bench Testing: This involves testing individual components or systems on a workbench to ensure they function as intended. This can include testing electronics, battery life, sensor accuracy, etc.
- Static Fire Test: This test involves firing the rocket's motor while the rocket is anchored to the ground. It allows you to observe the motor's performance and the avionics' response to the motor ignition and thrust without the rocket actually taking off.
- Recovery System Test: This involves testing the deployment of parachutes or other recovery systems. This can be done using a drop test, where the rocket (or just the recovery system) is dropped from a height to ensure that the parachutes deploy correctly and at the right time.
- Integration Test: This is a full-system test with all the rocket's components integrated together but not launched. It's to check the overall system performance, including communication between different components.
- Signal and Communication Test: For rockets with telemetry or remote activation systems, it's important to test signal strength and reliability, especially if new avionics are involved.
Remember, each type of rocket and setup might require specific testing procedures. Always follow best practices as outlined by experienced rocketeers or rocketry organizations, and adhere to all safety guidelines and local regulations.
How do you go about testing your rocket’s recovery system?
Would you like to see time put aside at launches to either test or tutor in the correct configuration of your rocket’s recovery system?
Spent some time testing the Altus Metrum EasyMini v3.0 to simulate my anomalous flight and lawn dart last weekend with the 38mm “The Lawgiver”.
The flight was on a Pro24 sparky G100. Good launch but quickly vectored right to about a 45 degrees climb then flattening out at about an estimated 800 feet. Watched it come in ballistic in the distance, fully intact, so both the apogee event and the main event failed to either ignite or to shear the single 2-56 nylon shear pins for the lower airframe or the nose-cone separation. Both BP charges were 0.35gms (ground tested well with 0.25gms), both BP ignitors were MJG Technologies J-Tek 7 eMatches, the battery was a Dualsky ECO 520.1S 3.7V LiPo.
I sent some basic info to the Altus Metrum “contact us” page and got speedy replies back. Since I’ve not found the rocket to check the physical evidence, I’ve only been able to give them flight behaviour observations. After contacting the Altus Metrum guys, the conclusion regarding the altimeter functionality was that:
- The EasyMini would still have detected the launch (uses barometric sensing) despite the lower than expected apogee.
- The actual apogee should still have triggered the apogee ignition. Altus have reviewed a flight log where the apogee was only 35m above ground and it still triggered.
- The main chute (set to 700feet) should still have triggered, either at that altitude or a short duration after the apogee ignition if the actual apogee was lower than the setting for the main. They do this to ensure each igniter gets sufficient charge to work and to protect the airframe from the stresses of a simultaneous drogue and main deploy.
- They advised that my LiPo might have had a discharge protection circuit built into it which may have stopped the ignitors from getting sufficient current to fire. Their recommendation is to either use their special LiPos or a 9V battery.
So, to explore the theory that maybe the LiPo failed to fire the igniters, I’ve performed two ground tests with a spare EasyMini v3.0. I used the same type of set-up as the flight:
- One 1S Dualsky ECO 520 battery (1.92Wh, 3.7V, 25C).
- Both tests used a pair of MJG Technologies J-Tek 7 eMatches fitted to the Apogee and Main outputs. All were cut to the same lengths as was used in the Av Bay, and resistance checked to between 1.2 and 1.4 Ohms.
- One test was with the Lipo battery fully charged at 4.0V, as seen on the charger control screen and as reported by the EasyMini beeps.
- The other test was with the battery reporting 3.8V (EasyMini beeps only).
- Testing was done in my vacuum food-saving tupper-ware box, the air extracted by hand pump.
- In both tests, the apogee and main ignitors successfully fired at approximately the points they should have, so no apparent firing restriction from the LiPo.
AMRS Level 1 - PML Callisto May19 H100W 3600ft
AMRS/Tripoli Level 2 - 3" AGM33 Pike Aug20 J270W 3300ft
First Airstart - Thales Starstreak Mar22
First Cluster - Banana Republican Jun23 3xE20 1856ft
Impulse tally - 11,019NS since May 2019
Thanks for the detailed info, really like the test setup. Hopefully you'll find it next launch to triage a bit more. At the end of the day, it could be something as simple as a loose connector on the battery terminal of the altimeter....
I had something similar happen a few years ago, turned out to be a dodgy LiPo.
Did you say the rocket was called "The Lawngiver"???
Tripoli #13468 L3
Tripoli Prefect #131
QRS President
@crom With hindsight, its a really good job I didn't give it the other name I'd selected...... "Cow-piercer".
AMRS Level 1 - PML Callisto May19 H100W 3600ft
AMRS/Tripoli Level 2 - 3" AGM33 Pike Aug20 J270W 3300ft
First Airstart - Thales Starstreak Mar22
First Cluster - Banana Republican Jun23 3xE20 1856ft
Impulse tally - 11,019NS since May 2019
I'd like to chime in here Brendan to say this might not have been on you. What you may have run into is what many people in the hobby refer to as "The Altus Experience". There's a reason why I fly TeleGPS instead of TeleMetrum, much like there's a reason why I've not updated my EasyMega firmware that I use for tilt inhibit staging in quite some time.
Keith and Bdale are great, but it's a hobby business and they make hobby mistakes. When they mentioned the Lipo protection circuit issue to you, I doubt they would have copped to the fact they discovered this by shipping TeleMetrum v1.0 kits with Lipos that had voltage protection circuits. These batteries would power off the Lipo when the TeleMetrum attempted to fire an e-match. It's quite disappointing to have a Blackhawk38 reach 12.5k ft only to never send a packet or be seen ever again.
Altus "FixBattery" page
If you're going to roll the dice with firmware upgrades for Altus hardware, I'd recommend waiting for the firmware released after Balls where people's projects failed due to "The Altus Experience" and they were patched up after the event. Reading some of those bugfix release notes is quite an eye opening experience. Attached is one of the aforementioned "Balls patches".