r/rocketry

Hi everyone, I was just curious as to how people in this community test that their flight computer firmware is working correctly before launching?

Hello everyone,

I'm designing a gas-generator rocket engine feed system from scratch (including regenerative cooling) in EcosimPro as part of a university project.

I was looking for a detailed P&ID to better understand the typical plumbing architecture of a liquid rocket engine, including the valves, piping, and instrumentation required from the propellant tank outlet to the injector interface.

I've searched extensively online, but I haven't been able to find the level of detail I'm looking for. I'm particularly interested in references such as technical papers, books, reports, or publicly available engine documentation that explain the design philosophy behind the fluid system.

For example, I'd like to understand questions such as:

• Why is the Main Fuel Valve (MFV) often located upstream of the regenerative cooling circuit?
• Under what circumstances are check valves preferred over actively controlled valves?
• What drives the placement and selection of components such as filters, purge lines, pressure transducers, relief valves, and flow control devices?

I'm not looking to copy an existing design; rather, I'd like to understand the engineering rationale behind the layout and component selection so I can develop my own system from first principles.

If anyone can recommend good references or share useful resources, I'd really appreciate it.

Thanks in advance!

A podcast episode with mechanical engineer Emma McCarthy at LSU on making materials for extreme conditions!

Our team is making an hybrid rocket, and we wanted to try and use dry ice to cool down the N2O tank. Anyone have some tips or designs to do it? Im having a little trouble finding stuff

I am on a student team and would like to design a good media setup - for photographing the rockets and making videos of launch, as well as producing high-quality on-board live videos.

The setup I want:
- A high-quality video camera to record video of liftoff from the ground
- A high-quality photo camera to capture high-quality stills of liftoff
- A go-pro or something go-pro-like to put on the launch rail with remote power-on and remote recording trigger capabilities
- A good camera for live streaming the launch to our social media
- A good system for creating the highest quality on-board video that would be live-streamed

To this day, my main issues have been:
- Remotely powering on the cameras. The time between leaving the pad and liftoff can be up to 2-3 hours, so we can’t just turn them on and leave them
- Cameras overheating. I have attempted to solve this with a fan that attaches to the camera and a small umbrella, but still better to turn it on about 5 min before launch
- Remote recording trigger. How do I start recording remotely?

Can you guys recommend cameras and solutions for this?
The brand of the camera DOES NOT MATTER, neither does the price NOR the way in which it would be remotely triggered

like genuinely how do you all come up with names for your rockets😭

I've made a couple of model rockets, and I think I'm confident enough to build a rocket with multiple first stage engines. However, I'm deathly terrified of only one engine igniting or having a significant delay between the two, leading to the rocket shooting sideways. Do you guys have any tips for ensuring a good ignition or making the rocket safer if it doesn't occur?

I've been looking at highly-metallised fuel grain concepts for hybrids and I think I've come up with something unexpected. I call it "Hypermag", short for "hybrid peroxide magnesium".

The oxidiser is 85% HTP, and the fuel is Elektron magnesium-aluminium alloy (I've assumed 90% Mg 10% Al w/w), mixed in various ratios with a hydrocarbon binder (for calculations I've used paraffin, as that's what CEA supports). At high metal loadings, it may be preferable to introduce molten hydrocarbon into a metal matrix rather than trying to slurry metal powder into the hydrocarbon. Isp peaks at 70% metal in the fuel and density impulse peaks at 80%. Even a pure-Elektron fuel grain (assuming you can get bulk metal, rather than powder, to burn smoothly) has an Isd about 10% higher than neat paraffin. There are some potential operational advantages to these highly metallised fuel grains, such as the mechanical strength of Elektron, and its thermal conductivity (which should improve regression rates and may also make chamber heat available for regenerative cooling, driving thermal decomposition of peroxide to power pumps if that's your jam), but the main benefit is in some interesting properties of the propellant chemistry.

When run rich, the Mg strips the oxygen out of water (the magnesium-steam reaction), producing a significant amount of H₂ in the exhaust (about 70% of all the hydrogen in the propellants ends up in this form). It's also reducing enough that the carbon in the paraffin goes to CO, rather than CO₂ (the reverse water-gas shift reaction). These light diatomic molecules make for a γ that's surprisingly good for something that's half ceramic smoke by mass. When run lean, these equilibria shift to favour H₂O and CO₂, and the increase in energy release is almost exactly balanced by the decrease in nozzle efficiency. This is especially noticeable with the 70% metal fuel, whose Isp peaks at 1.2 O/F but is less than a percent lower at 3.0. (Tc is 3100K in both cases.) This almost complete insensitivity to mixture ratio is handy for a hybrid (where O/F is often poorly controlled), and may even improve stability (e.g. by eliminating mixture-mediated Pogo).

Massive caveat: this is all based on CEA simulation results. Two-phase flow losses from all the condensed MgO could be higher than predicted, and whether the metal particles actually burn to completion or just coat themselves in an oxide layer can only be settled by experiment. But it certainly feels worth investigating! Has it been looked at before?

Performance calculations (O/Fs chosen for max Isp, except the extra 70% row) with Pc=30bar, Pe=0.75bar, shifting iac:

Paraffin%	Elektron%	O/F	ρ (g/cc)	Isp (s)	Isd (s·g/cc)
100	0	8.25	1.321	270.22	356.87
50	50	4.4	1.358	278.67	378.46
40	60	3.0	1.370	280.65	384.37
30	70	1.2	1.393	283.06	394.29
30	70	3.0	1.396	280.92	392.20
20	80	1.8	1.434	278.37	399.22
10	90	2.4	1.462	270.62	395.68
0	100	2.6	1.492	262.16	391.17

Exhaust composition (70% Elektron, 1.2 O/F, by mass): 45% MgO, 26% CO, 14% H₂O, 8% MgAl₂O₄, 4% H₂, 3% CO₂. (Notice that there's no Al₂O₃ in the exhaust; it all goes to spinel.)

The other interesting thing to note is that this is very specifically a propellant for the dilute peroxide. If you sim the same thing with pure H₂O₂ oxidiser, the Isp gain over paraffin is negligible (peak is a little over 1% at 50% metal). Performance of the 100% Elektron fuel is almost identical with both oxidisers (with pure HTP: O/F=3.0, Isp=264.02, Isd=391.37). Conversely, if you use 50% strength peroxide, where hydrocarbon fuels basically give up (Isp=199, O/F=14), hypermag keeps on chugging (258s for 70% metal, 257s for 100%). And that 70% metal is running at O/F=0.9 where (to within a rounding error) all of the hydrogen in the propellants ends up as H₂ (more of it winds up as CH₄ than H₂O, and there's even a bit of C₂H₂ formed. That is one seriously reducing flame). The limiting case of this is the magnesium-water rocket, which in theory is possible, but I couldn't get CEA to converge using Elektron fuel or liquid water. With pure Mg and 375K steam it gets Isp=257.61, Isd=323.03 at 1.1 O/F.

Basically I want to build a rocket over the summer what tips can you guys give me so it can go as smoothly as possible.

I recently purchased and assembled a high power rocket kit and am eager to launch it; however I am facing difficulty with applying for certification. I sent an email to the club leader of the closest NAR club over a week ago and have not heard back. This is really disheartening for me as this I have a passion for rocketry and feel like I am being held back by the nicheness of the hobby.

https://preview.redd.it/nbclrh2dyoah1.png?width=1069&format=png&auto=webp&s=de41e1d0fa3f9487461a6c258e4d16bfbcc7494f

https://preview.redd.it/9uww50beyoah1.png?width=1411&format=png&auto=webp&s=62be9414d767e19394a9c0da8dea44b77c69da66

https://preview.redd.it/e67ac1beyoah1.png?width=1390&format=png&auto=webp&s=b7e448b1ed2615ba522e9636675ba59691ddbd1f

https://preview.redd.it/udla80beyoah1.png?width=1480&format=png&auto=webp&s=14fd8e413d5dc2cccb1aac90ba1567c92af1f465

https://preview.redd.it/w0t6b0beyoah1.png?width=1534&format=png&auto=webp&s=99ea3d0c335c4f64c8da6eb8a545fcd29ad6831f

https://preview.redd.it/40e1r0beyoah1.png?width=1389&format=png&auto=webp&s=8673ee7cc150c0f9a2d8204c25dad8867f4c793d

https://preview.redd.it/qgk841beyoah1.png?width=1246&format=png&auto=webp&s=ffce0026502b9d49743c8e9f3d028646f62d47bb

4-layer PCB, 52mm × 175mm

BNO085 — 9-DoF IMU with onboard sensor fusion

BMP388 — precision barometer for apogee detection

INA260 — 15A current monitoring with integrated shunt

RFM95W — 915MHz LoRa telemetry

Teensy 4.1 — 600MHz M7 brain

Dual redundant pyro channels — two MOSFETs, two e-match outputs

4× servo outputs with screw terminals

Main power switch + arming switch — proper safety architecture

2× RGB status LEDs

Piezo buzzer

Ferrite bead noise filtering on sensitive sensor rail

Bulk capacitors on both battery and BEC output rails