r/AerospaceEngineering

Suppose we have 2 molecules and one moves on the other with 10m/s. The pressure wave travelled from one molecule to other with a speed of 10m/s so this should be the speed of sound. Same principle applies when there's billions of them no? Why? Does my example hold but in reality since there's billions of them the system gets more chaotic and so the speeds are not the same due to energy losses, not perfectly elastic collisions, different speeds​ of each individual molecule etc?

Most mechanical catapults suffer from severe initial jerk followed by exponential force decay, requiring massive structure to survive peak loads while underutilizing the rest of the stroke.

I recently published an open-source passive transmission called RopeComb that addresses this by dynamically altering mechanical advantage throughout the stroke using a counter-folding pulley array.

The paper preprint is on engrXiv (https://doi.org/10.31224/7913), and the interactive kinematic solver + open CAD files are available at ropecomb.com.

https://i.redd.it/pgtu01mt3akh1.gif

https://preview.redd.it/m9avca7v3akh1.png?width=1250&format=png&auto=webp&s=fc0696cdbe77d2cdcdfeabea0717c29ec559468b

https://preview.redd.it/lthhnb7v3akh1.png?width=1278&format=png&auto=webp&s=8e2b28b109ce30535053304466c48a0fcb2db13a

Key takeaways from the kinematic model:

• Near-constant acceleration profile: Flattens the peak-to-average force ratio, maximizing velocity gain over shorter rail lengths.
• High energy transfer efficiency ($>70\%$): Converts heavy carriage momentum directly into projectile exit velocity without onboard motors or high-pressure gas.
• High-modulus line utilization: Leverages modern UHMWPE (Dyneema) lines to scale exit speeds past standard mechanical limits purely passively.

Can this be the new king of mechanical launchers ? ... I'd love to get feedback from anyone working on high-speed mechanical linkages or dynamic line systems regarding real-world friction and line-dynamics bottlenecks.
[Patent pending — US provisional application 64/124,997]

So from what I've understood choked flow occurs if a fluid flows in a pipe with a velocity of mach 1 and no matter how much more we decrease the cross-sectional area of the pipe it won't go past mach 1. Why is that? I've heard explanations saying that mach 1 is the speed that information travels from the right to the left (assuming that the fluid flows from left to right) and so if we decrease the area from the right part of the pipe the information will not be able to travel back to say​ ​"​hey the pressure dropped here, I want​ you to push more". But I don't want that kind of explanations, I want to really understand what happens there. Even if we have to look at the macroscopic level. I want to understand the mechanism. Also I am asking this because I'm trying to understand how the De Laval Nozzle works so if anyone can help me there feel free to drop an answer to this post:​

https://www.reddit.com/r/AerospaceEngineering/comments/1vq87hu/how_does_a_de_lavar_nozzle_workand_what_is/

​

Hi! Hope this post is allowed. I'll try to avoid any secret information, sorry.

In 2024, I've had to do calculations for the new Russian orbital station and iss. No-one knew how. It was similar to my first job, I thought I'll somehow manage with literature. I collected some books, started learning. Couldn't figure it out for a week or so. My chief, who started working in 2000, started thinking about it as well, couldn't figure it out as well. 2 weeks passed.

Later, we came to an old engineer from other office who worked from the 80s and in roscosmos since 90s-2000s. Silently completed everything in 10 minutes without any help, just my questions "how". Real story btw.

He was such a nice guy. And he wasn't a chief or something, just a regular engineer.

Btw should I do ama someday?

Not necessarily the biggest breakthrough.Somthing underrated?

It could be a relatively small development that has made a huge difference to performance, manufacturing, sustainability or cost.

What's something you've come across recently that made you think:

"That's actually pretty clever."

Would be great to hear some examples from people working across different parts of the materials industry.

Hey guys, I've got about a year of experience with OpenFOAM. I've run different types of simulations — SIMPLE, PIMPLE, incompressible, compressible, laminar, turbulent — on 2D airfoils and 3D aircraft, like the NASA N2A HWB model, with decent mesh quality and case setup. The post-processed results matched the reference data pretty well. Just sharing this to give some context on where I'm at with OpenFOAM, but I'm still learning and exploring more of it.

Lately I've been seeing AI/ML being used in CFD, and since I come from a non-coding background (I'm a Mechanical Engineer), AI/ML and neural networks still feel like a black box to me. I don't really know how they work under the hood.

So I wanted to ask — how can I actually use AI/ML and neural networks in aviation-related CFD work?

For context, my future work will mostly revolve around optimization studies, detailed aircraft analysis, and static/dynamic stability analysis of aircraft. So I'm hoping to understand how AI/ML can help speed things up, and ideally how to align with whatever the industry is currently doing in this space.

Many explanations from my perspective seem incomplete because they do never actually explain the why but only the what happens. Why does adding a diverging section on a throat which gases reach velocities of magnitude Mach 1, accelerate them even more reaching supersonic speeds instead of slowing them down? From what I've read this phenomenon occurs due to the gases being compressible instead of incompressible but still that does not explain the why. Why a compressible's fluid speed increases when the cross-sectional area gets bigger? Is it the opposite of what would happen with an incompressible fluid? It seems to. Also what if we keep just the converging and throat sections only and keep making the throat smaller and smaller? I've watched a video saying that Mach1 is the max speed the gases can have at the throat and if we keep making it smaller it doesn't make them faster. How is that? Can someone give me an in-depth analytical explanation?

Hi everyone !

This has been on my mind since the end of my third year. For context, I’m about to enter my fourth year of Aerospace Engineering degree in France. As part of our curriculum, we need to complete a 16 week internship abroad to validate the year. My profile is quite good I think, with notably an internship in a big firm in France, on top of internships in smaller firms, volunteering, and involvements in projects and clubs sanctioned by some other big firms. On top of that, I’ve lived most of my life abroad, and am fluent in three languages. My main issue now is finding contacts and internships in English speaking countries. Obviously, aerospace engineering is quite a closed sector, and especially due to defense matters, most companies don’t allow foreigners, which also limit my options. Apart from contacting alumni in hopes of getting an answer, how can I find suitable openings, especially ones that could help me find a job right after graduation ?

Thank you in advance !

Hello all, I want a goal of mine for the next year to be making my first aeronautical engineering project. I am pretty late to the scene because I enlisted in the marines for 4 years, but I am about to start my second year of college and I really need to get my feet wet before I start taking upper division courses at uni.

I am super inexperienced, to start. I would just like to know what kind of engineering project I should start with. I am very interested in electric propulsion systems for aeronautical engineering. Obviously I am nowhere near that level, but what’s a good few hobby projects I can do that would help me start build up to that level? Also what’s a good resource I could use to understand how the basics work? I have dabbled a very tiny bit with Arduino and C++. I took like 3 CAD classes in high school (Intro to CAD, Auto CAD, and 3D CAD), but I literally don’t remember anything or how I even passed those classes with As and Bs to be completely honest as that was like 10 years ago… Dang.

With that being said, if anyone could also give a new guy some suggestions or resources that helped you, I would genuinely appreciate it.

I need wiring and connection details.
dimensions.
How much time i use once connected to Flight controler board
and how i choose for defence application

Especially for those of you working in defense.

For example, Shanghai has the world’s largest planetarium. Would I be allowed to visit?

Hello. So AE is a thing i really love but for Versatility does doing BSc in ME changes a thing? As being a non citizen doing Bsc in AE is not the best option due to Itar laws. so whats yalls opinion on this?

Hey guys
I’m taking aerospace engineering as my major (and I know the first year or two is just regular engineering basics) but I have some free time and wanted to get ready for it as much as I can. I have never touched coding and heard it’s very important here for making stuff work on arduinos and analyzing data so I wanted to learn it.
I just wanted to know any good resources anyone has to learn future skills needed for this type of major for coding or for any other thing to make my time useful instead of just scrolling. I’d want free resources preferably (of course) but I’m fine spending a little bit on things that might be worth it.
Basically what skills should I learn and from where to get ready for college to the best of my abilities so I can use my free time well.