I want the landing to be nice and stable.

So crazy idea and need everyone’s input. I have a massive amount of Estes Alpha 3 single stage rockets left over and need to build multi (2) stage rockets next. What I thought of is finding a way to just construct 2 of these rocket kit parts together and make 1 big rocket that’ll save me from buying multi stage rockets.

Has anyone ever done this before or even better with this exact rocket? Any tips or reasoning on if this will even work and if it’s safe to do or asking for a major safety incident. Thanks!

Hai i am really interested in physics and recently i have joined a startup as a semi intern and they are going to do a model rocket launching project within this year and i want to be the guy who helps them with most of of the flight simulation , i am not enrolled in any university or any such just finished high school so matlab is not accessible for me at this point, i am quiet well versed in python , i am not able to find any books or data which is valid and which will teach me all about rocket flight simulation ( not the structural analysis part) and please suggest some books or guides for the physics behind this too , currently i am self learning ways to solve ODE's in python hope you guys will help me out note: matlab/simulink is not accessible to me , and is python enough for this purpose

Does anyone know of any turbopump cad models that exist in file formats such that they can be 3d printed?

I had an easy mini but it broke recently and when I went to replace it they were out of stock. These are the computers that look most similar in price and capabilities. They both seem good to me however the Blue jay looks slightly better because it can also be a two stage computer. From yalls experience what should I buy?

I have an Idea making a model rocket agency it won't be big I have a logo,mission patches and rocket families.

The problem is I don't have a motor or anything at all I just started I have a tube a pretty aerodynamic nose cone and a parachute I'm hoping I will make a launch pad if I find where to launch it.

If you have any tips tell me BC I don't know ANYTHING about model rocket idk how 2nd stages work how parachutes deploy and if you have any ideas tell me pls✌️

I'm stuck trying to decide what to do this fall and want some opinions. I'm between 2 projects to work on while I'm at school with workspace and tools, alongside also helping my collegiate team.

1. Start my L3 cert process by finishing my last L2 qualification flight, finding a second TAP, getting approval for my design plan, and beginning construction. I plan on doing a scratch 98mm body with a 75mm mmt, full composite, fin layups, dual separation dual deploy, redundant avionics and tracking, etc.

2. Minimum diameter 54mm build to get some supersonic, high TWR experience and build my record before an L3 attempt.

I got my L2 in the spring on a 5.5in LOC Magnum 3E adapted to a 54mm mmt, but I've only flown it once since then due to issues with my cert paperwork and getting motors. I've helped friends with multiple L1/L2 builds and launch day support, but I don't want to get overconfident by saying that can "replace" experience building and flying myself.

The reasons I'm considering an L3 are the unlocking of "bigger and meaner" rockets, the clear defined goals and "rewards" for success, and the gain for my college team of someone with more experience and a student flier of record.

My motivations for option 2 are fear of rushing before I am ready, it would be cheaper, and in all honesty it would let me fly a cool fast rocket sooner than an L3 build. It would also fill out my qualification flights, and potentially help if a TAP is worried about experience.

Let me know y'all's thoughts and opinions, I want to make sure I'm not being dumb before I spend time and money on a build

Hi everyone. At IMF.Rockets, we are currently designing the payload repositioning system for Hermes, our 100km suborbital vehicle. We need an RCS to reposition our vehicle for reentry.

We are doing a trade study on a cold gas thruster system. I really want to use CO2 because it stores as a liquid at room temperature under pressure, which gives us a massive density advantage and saves a lot of tank volume compared to compressed Nitrogen (N2).

I am worried about the phase change. Rapid blowdown of CO2 through a solenoid valve into a near-vacuum environment is notorious for adiabatic cooling, resulting in dry ice formation that clogs the valve seats and nozzles.

Has anyone here successfully built a CO2 cold gas system for high-altitude/vacuum use? Were you able to mitigate the freezing with specific high-flow solenoid valves and nozzle geometries, or did you add a heating element, or just switch entirely to N2 to guarantee reliability?

Would love to hear some empirical data or see any plumbing architectures if anyone has tackled this.

I need some help! I just finished my LOC Micro Magg. This is my first super short and stubby rocket I'm going to add nose weight, but I don't know what the stability should be I want it to be stable but not too heavy.

Not looking to be able to eject charges or anything. Literally all I want to do is just have it tell me the height the rocket went.

I'm working on the design of a small pressure-fed GOX/ethanol rocket engine (around 200 N thrust with a 5-second static burn) and I'm looking for some advice on injector sizing, specifically the GOX orifice calculations.

The oxidizer is supplied from a high-pressure welding oxygen cylinder through a regulator to the injector, and the ethanol side will also be pressure-fed.

So far I've been using CoolProp to model the oxygen tank blowdown and the cooling that occurs across the regulator, which has been really helpful. The part I'm struggling with is modeling what happens after the regulator. As the oxygen flows through the piping, injector plate, and hardware, it warms back up from the initial temperature drop, and that changes the density at the injector. Predicting that temperature rise accurately has turned out to be much more difficult than I expected.

I'm trying to avoid introducing a large error into my injector orifice sizing because of incorrect assumptions about the GOX properties at the injector inlet.

Has anyone here dealt with a similar problem? If so I have a couple questions.

• How did you estimate or model the oxygen warming between the regulator and injector?
• Did you use a simple engineering approximation, a thermal model, CFD, or just rely on test data?
• For injector sizing, I've been using a mass-weighted average temperature over the burn to estimate the GOX properties at the injector. Is that a reasonable approach, or is there a better method? At this point ive accepted across the whole run It won't be 100% accurate but I'm trying to get as close a possible.

I'd really appreciate hearing how others approached this problem or if there are any references or papers you'd recommend.

Thanks, any help is appreciated!

Hello,
I want to build a little altimeter and a speedmeter
For a homemade rocket. It hase to be 6cm longue and 2/3cm wide.

How can i build one for a cheap price (10-20€)?

Hi! I've been doing some deep dives into bipropellent rocket engines but found something that just doesn't seem right.

When expressing Chamber pressure inside of the combustion chamber our 2 main variables are Characteristic Velocity and Mass Flow Rate, but wouldn't inlet pressure not being included mean that with a propellent, supplied at a sufficient mass flow rate, allow you to achieve a higher chamber pressure than the pressure at which said propellent was injected?

From what I've seen the injector is always the highest pressure point in an engine, from where subsequently the pressure falls by some percentage and that constitutes the chamber pressure.

Sorry if the question seems weirdly worded, English is not only hard, it's also frustrating.

Edit: Thanks for the quick answers! The misconception has been eviscerated and I think I see where I went wrong!

Are there any good known locations to fly model Rockets in Lake County?

While pouring some KNSB motors for stand testing an idea occurred to me, if a home made E match uses a carbon powder slurry across two wires to generate heat, and that resistance was aiming for approximately 2 ohms, then could I just use a standard 2 ohm resistor? So I scraped together a few small beads of propellant and wrapped it around a few different values of 1/2W resistors I had on the bench and started testing. I grabbed a 12v 8Ah battery as a power source and put together three different igniters using a 5 ohm, 3.3 ohm and 1 ohm resistors with a small bead of propellant wrapped around each. The 5 ohm lit in about 2 seconds, the 3.3 lit almost immediately and the 1 ohm completely failed to ignite. I believe a 3.3 ohm with a small amount of propellant around it makes a completely serviceable igniter for only about $0.03 each.

Hi everyone! I’m still pretty new to flight dynamics and stability analysis, so I was hoping to get some guidance.
From what I’ve read, a static stability margin of around 1.5–2.0 calibers at the launch pad is generally considered a good target. My rocket is currently 1.52 cal at liftoff, so that seems fine. However, when I ran the simulation, I noticed that the stability margin keeps increasing during flight as the motor burns out. Near burnout it reaches about 3.44 cal, and after burnout it actually exceeds 3 cal. We’re using a plugged solid motor, so there’s no ejection charge or significant hardware change after burnout.

Most of the discussions I’ve found mention that you generally don’t want a rocket to exceed 3 calibers because it can become more susceptible to weathercocking, but I’m not sure whether that’s meant as a strict limit or just a rule of thumb.

So I have a few questions:
1. Is it normal for the stability margin to exceed 3 cal after motor burnout?
2. Should I only be concerned with the stability margin at liftoff, or should I also be trying to keep it below 3 cal throughout the entire flight?
3. If having more than 3 cal after burnout is actually a problem, what are the usual ways to address it? Is moving mass aft the only practical solution, or is this generally considered acceptable as long as the liftoff stability is within a good range?

I’d really appreciate any explanations. I’m trying to understand the reasoning behind the guidelines rather than just follow a number. Thanks!

Need some help with solid rocket motor. Like extracting the propellant grain data, cuz when I put up the geometry data into my solver, the results are not matching with the experimental data. The pressure profiles (chamber pressure vs time) are close but not entirely matching. Plz someone help🙏🏽🙏🏽

i recently made a rocketry team in my university with a bunch of mechanical engineering students.we will be basically the first rocketry team in our country. We have no access to prebuilt motors and will have to make all the parts of the rocket from scratch. We are actively working on getting flight permissions. I wanted to know where should we start the development of our rocket so we can make a minimum viable product

Hi everyone. I’m a founder and propulsion engineer of IMF Rockets in Italy (building the HERMES suborbital vehicle for microgravity payloads), and I need some advice on our solid motor nozzle retention.

We are designing our first-stage solid rocket motor casing using Aluminum 7075-T6. Based on our internal ballistics, our Maximum Expected Operating Pressure (MEOP) is 69 bar (~1000 psi).

To retain the nozzle carrier, the current CAD architecture uses 12 radial retaining pins. I've been running the structural mechanics equations to calculate the exact failure points for the pins under pure shear stress versus the bearing stress (hole elongation) on the 7075 aluminum casing itself.

Here is my question: When dealing with radial pins at this pressure, what fastener material (ex, 18-8 Stainless, 4140 Alloy Steel, or custom brass shear pins) do you recommend? My goal is to ensure that if we suffer an over-pressurization anomaly on the static test stand, the pins cleanly shear before the 7075 casing catastrophically yields and fragments.

I've attached a cross-section of the CAD. Any flight-proven advice on fastener selection or safety margins for the bearing surfaces would be massively appreciated.

My friends are censored