Autonomously landing TVC rocket

Created wiring diagram and PCB schematic in KiCad. I stuck with the protoboard design though because it works well I didn’t see any real nor distinct advantage of getting a PCB over just using what I already have

I finished building the new TVC mount. A piece of the 3D print snapped off but I just hot glued and then epoxied it back on

I made another version of the parachute bulkhead and ejection piston. The new version uses a rack and pinion system with a steel bar, so the actual component with stress of it is not the servo horn itself. Additionally, I can simulations with claude code that simulated 2,000 flights with an Apogee F10 for the ascent motor instead of the Estes F15 (there is still an F15 for the descent motor). The reason for the switch is that the F15 descent motor was too strong for the velocity that the rocket was landing at. Either the descent motor set off too early and the landing velocity was too much or the motor set off too late and the rocket sprung back up when it hit the ground. With the new stronger F10 motor, the rocket achieves a greater apogee so the velocity that the rocket comes down at is greater, allowing the F15 to actually use its thrust slowing the rocket down sufficiently instead of being too strong for the rocket. Below is a photo of the outcomes for the 2,000 simulated flights.

I performed a static test with a rocket motor. Everything went well, except that the thrust vector motor tube melted due to the heat of the motor. Looks like I need to print a new motor tube.

I created version 4 of the parachute bulkhead piston. This version had a longer hook and the sides were also shaved down so that the piston fit easier into the tube. I also added more walls and used a gyroid infill in the slicer this time to increase the structural integrity of the part before I sent it to the 3D printer.

I replaced the lower leg ring with the improved design and I also added funtak to the bottom where the legs and ring contact. In theory, the funtak should slow down and absorb the impact/velocity of the legs before they hit the bottom. I added the funtak because in the last lower leg ring design, the velocity that the legs were coming down at snapped the platform below it.

I installed the new avionics holder today. However, when I was testing the lower leg ring, I found a weakness in the design. The ring has snapped where the legs came into contact with it. I failed to see the issue with my previous design where the 90 degree angle that the leg platform and the ring made was a point where the 3D print was fragile and could snap easily. So, I redesigned the lower leg ring so that the is a 0.25in fillet that tapers toward 0.125in at the edge along the edge where the 3D print had previously snapped. Below is a picture of the snapped leg ring.

I added the avionics and avionics holder into the lower body tube of the rocket. After that I attached the top tube to the bottom. I then performed multiple drop tests testing a straight down vertical drop, lateral and vertical drop, and spinning drop. I found that the rocket performed really well on the lateral and vertical lateral drops which I’m really proud of because the landing pads were doing their jobs of absorbing the shock. However, I found that on spinning drops, the rocket had a tendency to tip over, but not enough to fall. I think reducing the angular velocity about the body tube is something that I should look out for when performing my test flights.

I installed the new servo arm into the spring system and tested it, but in one of the trials, the crook where the servo arm is placed into the bulkhead broke off, so I had to redesign the bulkhead so that the fillet value on the corner where the bulkhead crook broke off to a greater value. The increased value on the fillet will hopefully increase the crook’s resistance to snapping. Also I had to solder together a female XT-30 connector port to another wire that plugged into the Li-ion charger because I didn’t have the adapter. The old wire was a female XT-60 connector which didn’t work with my male XT-30 connector. I also epoxied the bungee cord connected to the nose cone to the upper body tube.

I finished drilling out the holes in the body and I installed the spring mechanism into the tube. The arm of the servo was starting to become detached due to the stress that it experienced when holding back the spring’s force when locked, so I wrapped wire around it and epoxied the arm again to make the arm strong again. Next step is to find a place to attach the nose cone and confirm the spring mechanism actually works with a static test with a loaded parachute.

Today I got the spring mechanism for ejecting the parachute to work reliably. I made a few improvements. Specifically, I made a new top bulkhead for the ejection system that featured a latch/crook for the servo arm to swing into when the spring is compressed and ready to be locked into. In contrast, the previous version had the servo arm swing directly in between the spring coils, which led to inconsistency and jammed ejections. Overall, today was a pretty productive day and I’m happy I got the mechanism finished since I thought I would’ve taken a lot longer on it.

I tested the spring mechanism that launches the parachute out of the top rocket tube. I cut open an old tube so that I could see the length that the spring compresses. Still need to verify the system works and touch up on the actual mechanism.

Took apart old version of the spring mechanism on the parachute bulkhead to use the spring on my next iteration of parachute bulkhead. Below is a picture of the parachute bulkhead before I took it apart.

I worked on the parachute spring and more importantly, the e-matches that ignite the descent motor and cut the rubber band holding the legs together, to then release the legs to landing. Today was most likely the biggest leap in the project because I finally got the e-matches to not only ignite, but also ignite of command with little to no delay. I still need to work a little more on the parachute spring ejection system, but that’s as expected because I only started that component a few days ago. (Also peep the white monster in the corner).

I glued the landing pads onto the legs of the rocket. After expoxying them, I tested the landing leg deployment and how it would land and they legs worked!

I wired the two positive wires from the second 7.4V LiPo and negative wires to the LiPo negative and Teensy 4.1 ground for each of the two MOSFET gates.

Today I attached the legs on the rocket and confirmed the leg deployment system worked with one of the four leg structures. Next step is to epoxy the landing pads onto the ends of the legs.

Added servo that controls the parachute ejection system. The servo will release a spring that will then eject the parachute out. Also I needed to cut and add additional wire and then shrink tube it bc the wires were too short.

Soldered the wires connecting to MOSFET to ignite the descent motor. Tried to wire the additionally connected wires to create the spark, but could not complete today.

Build the bulkhead that will be used to platform the black powder charge or mechanical spring parachute ejection system.

Today, I mounted the thrust vector control mount onto the lower body frame of the rocket. Still need to confirm it works tho, for next work session…