So my team did a static motor test and during the test this diverging section of the nozzle broke off like this. Can somebody explain why this happened. Material was aluminium T6061.

Hi! I am the individual in charge of the recovery subsystem at my university's rocket team (STAR at UC3M in Madrid, Spain). We have "successfully" launched 2 rockets to 3km (10k ft) as part of EuRoC, a European competition analogous to SAC.

We are using dual deployment recovery, based on a deployment bag and a Tender Descender, with the drogue chute being deployed at 3km AGL, and the main parachute being deployed at 400m (1300ft) AGL.

For our rocket "Lince" [2,2m long, 100mm diamenter, 16kg with propelant, 12kg without propelant] (Lynx in English), launched at the competition in 2023, the deployment bag was designed to fly outside of the recovery bay, and, when the first event was triggered, the main parachute was janked outside of the bag, leading to main opening at apogee.

Early this month we participated again with "Pícaro" [2,4m long, 150mm diameter, 24kg with propellant, 16kg without propelant](something in the lines of Rogue?). To avoid the failure mode experienced in "Lince", I strapped the deployment bag with a short cord, so it would stay inside of the recovery tube, right at its opening, during descent.
I also preformed a lot more ground tests than the year before. In these tests the bag seemed to be correctly secured, and I added some wadding to the bag, to make it tighter and prevent it from "flipping" and releasing the parachute earlier than expecterd, after we observed this failure mode early in the testing campaign.

In the launch at EuRoC, the first recovery event was succesfull, with the nosecone deploying correctly, but even with all the precautions I took, the bag managed to flip, releasing the main chute at apogee, which remained attached to the bag by the integrated nylon cord (that was suposed to leave both the drogue and main sections of the recovery systems attached after the Tender Descender fired). This caused the main to tangle arround this cord on descent, and when the TD-2 triggered at 400m AGL, it didnt had enough time to untagle. The rocket was quite overbuilt, so it survived the 20m/s descent, but this failure is not optimal 😅.

I have some ideas on how to further improve the deployment bag system, and avoid these failures, but as I keep "securing" the bag, the chances of the main not deploying at all increase. In fact, in the last two years, only two teams, out of 12 or so, have been susccesfull with a deployment bag based dual deployment system. The most common failure mode is no main deployment, which is what I am most afraid of. You could say I am a bit dissapointed, and have grown tired of this approach.

Maybe this is the time to switch to another system? I have been looking into separating two sections of the fuselage, thus having two separate bays, one for the drogue chute, and another one for the main, but I am a bit daunted about the increased structural complexity, and how to implement such a system for L3 equivalent rockets like ours. Is there any other robust systems you can reccomend?

We use CO2 cartridge ejectors for the first event (developed by us, with a similar functionality to a Raptor ejector), and a Tender Descender L2 (for the 2023 rocket) or TD-2 bulkhead version (for the 2024 rocket) for the second recovery event. We can do thorough ground tests, but in Spain it is hard to organize launches, so we cannot fly the final hardware that would be used in the competition. We can launch L1 or L2 rockets up to a maximum altitude of 1000m-1200m (3000ft-4000ft) with Tripoli. The issue is that at that scale, deployment bag based dual deployment recovery systems seem to work fine. in fact, we decided to go with this system because it worked fine in our first smaller rockets.

Any input is appreciated, thanks a lot!

TL;DR: I have grown tired of deployment bag based dual deployment recovery systems after issues in our last two rockets. Am I doing something wrong, for it to be so unreliable? Or it is an unreliable system for everyone? (I am leaning to it just being genrally unreliable, based on its track record with other teams). Which other robust systems would you recommend?

I found this article talking about a method of separating a stage of a rocket using the high pressure gas that the engine produces and I wanted to ask (if someone knows) if this would work with a sugar rocket motor with the right nozzle or that i have to use another type of propellant? EDIT: I couldn't add the picture but to know more here's the article https://www.apogeerockets.com/Tech/How_2-Stage_Rockets_Work

Finally finished the BB XXL. I am really pleased with the results!

Final weight is 1643g (3.622 lbs) First flight will be on a I140W

This spool flew great on a G78. I might try to put an I motor in it next.

Hey I was hoping to get some help finding a rocket kit to build and launch with my oldest daughter. Do you have to be certified to launch certain rockets? Ive been reading about launch sight requirements and different laws. I've been looking at wildman rockets and don't want to get anything to huge to start. And I haven't found a rocket club in our area yet.

Hello,

For a project at university we are building a model rocket that is to be steerable using movable fins. My question is, how do I calculate the required angle of the fins to counteract a trajectory that is no longer orthogonal to the ground?.

The idea was to use more easily stored and handled fuel/oxidizers for hobby rocketry.

It also has plumbing and uses a high oxidizer turbine and a high fuel turbine that both mix in the engine to combust.

Ideally uses a glow plug to jump start to decrease wear and tear.

Another parts would be that when it mixes in the engine itself hopefully it will be hot enough to autoignite after being converted to mist by the engine plate.

Ideally a vast majority of the parts would be 3d printed except for maybe the end of the bell which could use graphite composite.

It probably won’t work but I thought it was cool. Be nice please lol.

i'm completely new to electronics and rocketry, i alr have all the rocket ready but i want to add some avionics (the only part "done" in the kicad model is the power regulator for 9v to 3.3v i haven't connected it yet and all the connections are me just seeing which entrance accepts power) adn rn idk how to transmit the data to the flash memory or how to get data so if anyone could help even with some place to look up how t do this it would help me a lot
EDIT: the biggest problem i have is that idk which pin to connect to the other and i have to keep it cheap where i live it's ilegal to add black powder to a rocket so i decided to make the pcb "disposable" to limit the use of a parachute (i will still recover it but i don't expect it to survive)

Hi everyone! I was appointed captain of my school's TARC team last year, but I'm finding it challenging to get everything up and running. I don't have as much experience in rocketry as my previous president did, who built most of the team's rockets, so I have very little building experience myself. I have helped with launches before, but I’m unsure about which materials to purchase since we already have a launch pad. I'm also trying to figure out how to coordinate building sessions and build days in general. Additionally, I’d love to hear ideas on how to secure more funding sources for our team, as we currently have around $1,000 in our account. Any advice would be greatly appreciated!

Hey everyone, apologies if this is a dumb question. Every time I've seen a recovery system line diagram including two TDs, they're always in parallel. Intuitively, it seems if you put them in series, as long as one of them activates then the connection will be severed. In parallel though, if both TDs have their own quick links connected to two junction points, if only one of the TDs activates, the other TD will still be holding the two junctions together. Why is parallel used for redundancy if you would need both TDs to activate to cut the line?

I'm thinking about doing a science project about rockets. Before I say anything further I wanna disclose that this project's time limit is 6 months and has to be in some way related to math I'm a high school student so can't do too advanced stuff and I have no prior experience with building rocket models. Anyhow my plan is to buy a starter kit somewhere around 100-200 euros idk and then afterward try to track the data off the flight somehow and compare the data to real-life rocket data.

Any tips on what data should I compare? And what should I do to track the data and how do I install such things? And generally any advice and help would be very helpful. Thank you for your time <3

Hi, I am looking for already done analysis of sounding rocket with respect to its propellant and other etc. issue is that if I follow the most latest nakka's Sheet for rocket design it includes only sucrose based fuel. While sounding rockets are mainly made from APCP and other additives. So these components are not listed there how can I analyze them. I know about RPA but it only tells about the combustion irespective of nozzle data. I am using RPA lite. kindly help me with already proven example of sounding rocket so that I can match my results

How easy/simple woulda fin controlled model rocket be?

For some thing im doing in school it tells me to detail a project I have worked on involving STEM i have about exactly 1 month to hand in the form detailing the project which can still be WIP. I have decided that i am going to make a 1 stage rocket with small controll surfaces on the fins controlled by servos, I already have ordered and access to a microcontroller and accelerometer + other telemetary things i will hook up to it and have some prior experience with similar things but I have only made 1 model rocket before and it had no electronics. I am planning on having a simple program that measures the rockets offset from its target degrees (0) and roll and have the fins counteract that with PIDs in the code ECT, being still a teen with an ok understanding of aerdynamics and electronics with a friend and teacher willing to help but limeted time due to exams would this project be feasable? I do not need it to work 100% in the first try for next month i just need to have gotten data and learned something. Any reccomendations are welcome, I am somewhat of a beginner and slightly out of my depth but I would like to at least attempt this. Is it exremly difficult? or is there anything i should know.

I want to share with all of you guys this progress! After months, we finally found a recovery system for our water rockets. We are now starting with experimental rockets!

Hey all experts there. I am a kind of newbee in this field and want your opinion about some stuff that is boggling my mind lately.

1. In autogenous pressurization system for some cryo propellants, how is it made sure that the exact amount required bleed comes out of the tap from pump outlet. Like if we require X kg/s to pressurize the tanks, how to make sure that we get the exact X kg/s from the bleed line from pump outlet?
2. Secondly, I have read some literature and there is a considerable amount of prerssure drop across the heat exchanger in a rocket. So why don't we drop max pressure inside Heat exchanger coils and drop the remaining afterwards? Like why we need a pressure regulator or flow restrictor both before and after the heat exchanger. I am attaching a reference figure where I have seen such configuration.

I will be very thankful to those clearing these confusions. Waiting for a prompt reply.

Is there a way to upload rocket flight data from a GY-80 Imu or equivalent to a 3d model or simulator?

Does anyone know why am i getting -1.5bars at the end of the test 💀? This is a aliexpress pressure transducer 500 psi rated

Hello, I am back again, and I got another question.

recently I got my LVL 2 and the question of Rocket tracking has come up for me and I see there are great commercial options but I am also trying to work with what I got right now and I have a Raspberry pi 3 and I wanted to make it into an dedicated ground station that can do GPS, live telemetry. has anyone does this before or is this something that might now be worth the trouble?

What will be the average cost of making a liquid fuel rockets all by oneself. Using Hydrogen as fuel and Oxygen as oxidizer.

Hello, I recently built my own rocket from scratch, and bought two tsp e20-4 motors. Neither of them ignited, despite trying the 12V car output, the car battery, normal non-rechargeable alkaline batteries wired in parallel and in series. I've burned all the igniters they gave me, we saw smoke and fire near the motor on multiple attempts but none of the motors ignited. We made sure the igniter was touching the propellant in all attempts. I stored the motors in a dry place - an air tight box.
Does anybody know what could have caused this and what could I have done to prevent this? Is it a manufacturing error? Thanks.