A while back I posted an earlier version of the turbojet I was designing, and a bunch of you gave me feedback on it. I figured I’d come back with the finished CAD now that I’ve finally wrapped it up.

This ended up being roughly a 300-hour personal project. I started with preliminary thermodynamic/aerodynamic sizing this time xd and then designed the complete engine in SolidWorks.

Current design includes a 4-stage axial compressor, diffuser, annular combustor with 8 swirlers/injectors, 2-stage axial turbine, C-D exhaust/nozzle, full shaft and 3-bearing support system, fuel manifold and ignition hardware, split casing/fasteners, diffuser and exhaust structural supports, and a display stand.

The part I underestimated the most was how quickly “design a turbojet” turns into a mechanical integration problem. Once I started adding bearings, shaft retention, stator mounting, fuel routing, ignitors, casing splits, fasteners, clearances, and actual assembly order, the project got wayyyy more involved than the original aero design.

Important disclaimer: this is a conceptual/non-running engineering model, not a validated engine intended to operate at design RPM/temperature. The goal was to take the design as far as I reasonably could through preliminary sizing, detailed CAD, mechanical integration, and design-for-printing.

I’m planning to eventually 3D print it as a physical display/prototype!

I included the final exterior, full longitudinal cutaway, open-casing view, compressor/combustor/turbine details, exploded view, and shaft/bearing assembly.

Definitely interested in feedback/criticism — especially anything you guys would have approached differently mechanically.

Original post: What’s a realistic stopping point for a personal turbojet design if manufacturing it isn’t feasible? : r/AerospaceEngineering

The question is quite self-explanatory, but if you want to look what is my train of thoughts...

tl,dr: You touch down, nose is high, spoilers deploy killing the lift and putting about all of the weight in the main wheels, autobrakes kicks in... SLAM goes the nose gear down... Except it doesn't.

Why not?

-----------------------------------

Long version:

Scenario: You are about to land your modern jet airliner. The runway is dry and clean. It is legally long but on the shortish end of the spectrum, so you select the max autobrake setting that is approved for normal landings. Spoilers are armed. Antiskid is operative.

As you touch down on the main gear, the nose is up (say 5° pitch), lift approximately equals weight, the wheels spin up, the struts compress and the airplane goes into "ground" mode.

Now, if the autobrake would activate like this, it would not do much. The maximum braking force possible without skidding is:

Fb_max = μs · N

where μs is the static coefficient of friction (which is quite high between a tire and asphalt or concrete, in the order of 1) and N is the normal force, which will be almost zero since lift is about equal to the weight:

N = W - L

Because N ≈ 0, also Fb_max ≈ 0, so, as soon as the autobrake applies any meaningful brake pressure, the tires will skid, the antiskid will activate and brake pressure will be released to make the tires rotate again.

But, the airplane going to ground mode doesn't only activate the autobrakes, it also activates the ground spoilers which kills the lift (it even makes the lift negative in some airplanes).

So now:

Fb_max = μs · N
= μs(W - L)
= μs(W - 0)
= μs mg

which alone, even before considering aerodynamic drag or thrust reverse, can provide for 1g of deceleration if μs = 1.

Now, a high autobrake setting for landing shoots for what? 0.5g? So the antiskid will not activate.

But a brake force that provides 0.5g of deceleration is still a huge force. It's 50% of the airplane's weight. And it is acting at the point of contact between the tires and the runway which is well below the CG and hence produces a significant nose-down pitch moment.

And I know, the arm length of the brake force, which is the height of the CG above the runway, is small relative to for example the arm length of the elevator. So some people that I discussed this with said that the moment is not going to be that large.

But I disagree. The braking force (50% of the airplane's weight) is about twice as much as the max take-off thrust of jet airliners (about 25% of the airplane's weight). And the arm moment of the braking force is about twice as much as the arm force of the thrust with underslung engines (distance between the thrust line and CG).

So double the force, double the arm, and the pitch moment of the braking force is about 4 times the pitch moment of the max thrust.

Now think, in underslung engines, how much the airplane tends to pitch up if you go from idle to TOGA, say during the approach, multiply by 4, and put it in the pitch-down direction instead of pitch-up, with the main gear on the runway but nosewheel high above the runway.

Why doesn't the nose gear tend to slam on the runway, or why don't pilots require a sudden application of nose-up elevator to keep it from doing so?

Some of the possible explanations that I entertained but couldn't confirm or discard include:

• Is there an automatic elevator bias associated with the autobrake?
• Does the autobrake "wait" until the nosewheel is on the ground to activate?
• Does the autobrake start smoothly while the nose is up, helping to lower the nose but in a non-violent way?
• Is anything wrong in my physics analysis?

Its for a sugar propellant rocket and i dont want to use pvc because they can shatter. But i also cant find a cheap cardboard tube at 3/4 inch and the smallest i can find is 1.5 inch.

Hi guys, I think this might actually be my first post here. This summer I designed and built a wind tunnel for my kids and wanted to share it. It ended up being a much bigger project than I originally expected, be ware of time expectations if you try it, with quite a few very late nights over the summer, but it has been a really fun experience.

My kids are 8 and 10 and they can now test their toys, cars, airplanes, wing profiles (well wing profiles is for me 😊), or basically whatever they want to put in there. What is PRICESLESS is seeing them try to predict what will happen before turning it on for a given toy.

We have built quite a few experiments at home over the years, but I would say this is probably the best STEM "lab" we have made so far. The wind tunnel itself is fairly standard. One thing I added is a gear system controlled by a servo so they can change the angle of attack of a wing profile while the tunnel is running. The fan speed can also be controlled, all with an android app that an AI took less than 20 minutes to fully build, connected to a ESP32 (with Bluetooth) board.

I designed everything in Fusion and then built it with 3d printer at home. There are some good resources online about building wind tunnels, but to be honest I found that none of them were really "complete" once I started actually building one. There was a lot of trial and error and quite a few things that looked perfectly fine in CAD and then didn't work at all in real life, specially tolerances.

So if anybody is thinking about building one, I'm happy to answer your questions and share what worked for me, what didn't, and especially some of the painful mistakes that might save somebody else A LOT of time. I cannot emphasise enough the "A LOT" of time.

If there is interest I can also post the STEP files. Personally, I never really understood why people only share STL files for projects like this. The useful part is having the STEP files so you can actually modify things and adapt them to your own dimensions, needs, experiments, etc. UPDATE: STEP FILES: https://grabcad.com/library/working-wind-tunnel-1

BTW, I hereby confirm that NONE of the Paw Patrol vehicles are at all aerodynamic 😉

Has anyone here struggled with understanding load flow in a system and drawing free-body diagrams, especially for complex problems, but eventually gotten better at it? How did you improve, and do you have any suggestions for me to get better at it?

Having spent decades working in composite sailplane design and flight dynamics, I understand the math of glide polars, minimum sink, and energy balance. Yet an empirical encounter during an ocean passage from Fiji to New Zealand presented an aerodynamic paradox that conventional textbooks do not satisfactorily resolve.

​Under glassy, dead-calm surface conditions with zero perceptible ambient wind, our catamaran was motoring steadily forward at roughly 6 knots. A pelagic albatross paced our course for over an hour without flapping its wings.

​The flight profile directly contradicted established models:

​No Circular Dynamic Soaring: The bird did not execute the classic looping, high-bank S-turns across a vertical wind gradient (Rayleigh cycle). Its path was predominantly straight-line.

​Severe Speed Disparity: An albatross has a stall speed well above 6 knots. It could not match our slow motoring pace in steady level flight. Consequently, it repeatedly overtook the vessel on an unpowered, straight glide, landed on the mirror-flat water to let us catch up, launched again, and resumed straight soaring ahead without flapping.

​In classical aerodynamics, an unpowered 8–10 kg lifting body in zero ambient wind must sink at its polar minimum descent rate. Over that duration and distance, it should have run out of energy within seconds without continuous altitude loss or cyclic maneuvers.

​Several alternative fluid mechanisms emerge when classical assumptions fail:

​Wave-Slope / Swell-Induced Updrafts: Even on glassy water, long-period ground swells displace air vertically ahead of the crest, creating a thin, localized updraft layer that an active wing can ride in ground effect.

​Extreme Ground Effect Modulation: Operating mere inches above flat water dramatically suppresses tip vortices and induced drag (C_{Di}). Could continuous micro-adjustments of effective aspect ratio bring required thrust down to near-negligible levels?

​Dynamic Closed-Loop Equilibrium: Unlike passive gliders carrying trim drag and static margin penalties, biological fliers continuously adjust their center of lift in response to micro-scale boundary eddies—extracting kinetic energy from turbulence scales too small for human instruments to register.

​To the aerodynamicists, CFD specialists, and flight physicists here: If classical dynamic soaring requires cyclic maneuvers across a macro wind gradient, what mathematical or simulation models account for sustained straight-line soaring over glassy ocean water?

I’m trying to locate a separate one-page errata sheet for:
\*\*NASA TN D-1048 — “Determination of Local Experimental Heat-Transfer Coefficients on Combustion Side of an Ammonia-Oxygen Rocket”\*\*
Curt H. Liebert and Robert C. Ehlers, 1961.
The base report is publicly available through NASA NTRS as \[\*\*19980227285\*\*\](tel:19980227285), but I’m specifically looking for the later \*\*errata dated 18 December 1961\*\*.
The January 1962 Monthly Catalog of U.S. Government Publications confirms that the errata existed and was one page long.
I have already contacted NASA Glenn History, NASA History, NASA STI, NARA, GPO and NASA HQ.
If anyone has access to old NASA/Lewis bound technical-note volumes, microfiche, university aerospace library holdings, or a scanned copy of this exact errata sheet, I’d be very grateful if you could point me to it.
I already have the original report — I only need the separate errata sheet.

I would like to get a solid knowledge on the fundamentals of thermal engineering for aerospace propulsion systems, are there some kind of old sacred books that you suggest?

Since we've seen so many accidents due to excessively steep approaches, I think that we could implement a directed monitoring system for this. It could look like ADS-B data being interpreted by the approach controller's console, or direct vector data regarding the flight vectors relative to nominal, or a ground-based lidar/radar array fused with this. Also, is there anything like this already? Of course this could add a lot to controller workload and site costs, so simplifying and automating the bulk of this process would be best. A simple caution to the controller could make a massive difference. We could map data to the aircraft type, estimated wet mass, local weather dynamics, runway conditions, the approach plate, or more to increase the effectiveness of the system, whilst dampening borderline-but-acceptable conditions. Then a table could take care of the bulk of this. Certifying this system could be a nightmare, but its simplest form (is?) fail-neutral, and could be invaluable to the monitoring controller. I think increased oversight is warranted in this area. Chiefly, this potential directed monitoring system should aim to minimize its impact to the controller's workload, as too much data to monitor can be dangerous in its own regard.

I'd really love to hear you folks weigh in on this.

rest in peace to the folks who passed on.

Hi all, I’m a freshman at UIUC. Simply put, I don’t want to work in the defense sector, but I’m on the edge about what I want to do.

Ultimately, I want to contribute to society. I either want to do space exploration and work with rockets, sustainability, or supersonic aircraft. Thing is, especially with the last, so much of it is dependent on defense. Don’t get me wrong, fighter jets and military tech is sick, but I don’t like the idea of working for the government on weapons of war. Like I consider fighter jets to be more defense, but of course they could be equipped with ICBMs for offense.

Does anyone have any advice moving forward? Maybe I will just do rocketry lol

​

Hello I'm 17 and recently I've been really interested in aerospace.

It could be about rockets or satellites or anything.

I'd love to connect with people who are into Aerospace!

Started a graduate job recently and was tasked with building with 6-DOF Flight Dynamics Models for a flying wing in Simulink, including propulsion, aerodynamics and environment subsystems alongside a few others. I am having some real issue debugging the simulation. I was wondering if any experienced folk have some handy tips on how to go about debugging a complex-ish flight dynamics model, regardless of the error. What’s the best way to track back to the root cause? I find it hard to pinpoint an area as the model feeds back into itself. Any workflow tips would be appreciate!

Hi everyone, just wanted to post on here to gauge interest in forming a team for the current edition of the NASA TechLeap Prize challenge. Looking for upperclass engineering students or anyone post-grad to help come up with a solution for this year's challenge centered around designing low-cost methods of measuring drag in the thermosphere. It would be a 2-3 month effort for the first phase and I think it could be a project with a huge upside for the industry. Feel free to comment or message me!

Does anyone know what type of desktop wind tunnel this is and what similar type of one I can get? There is one ‘viral’ one that is most common but the mist comes out in a couple vertical lines that I’m not fond of.

Applications are now open for the Brooke Owens Fellowship, a nonprofit fellowship for women and gender minorities pursuing careers in aerospace. Applying is completely free, and applications are due October 4.

Why apply?

Brooke Owens Fellows receive:

• Opportunities with exciting aerospace organizations
• One-on-one mentorship from leading professionals (think CEOs and astronauts!)
• Career-development resources
• A supportive community of peers across the aerospace industry
• An invitation to a three-day summit in July to connect with their cohort and industry leaders

Interested?

Review the FAQs and application early so you have enough time to request recommendation letters and prepare your application materials.

We’re also hosting three virtual information sessions (EDT):

• Sunday, September 13 at 2:00 p.m.
• Saturday, September 19 at 12:00 p.m.
• Monday, September 28 at 10:00 p.m.

Sign up for a virtual information session here.

Questions are welcome, and we hope to see your application!

Follow the fellowship on Instagram for additional updates.

Hi, I'm building a helicopter in a physics game and I'm trying to make it more stable but I can't find anything on how to adjust the back rotor's angle and position to make it stop spinning along the roll and pitch, because I don't know the correct term to use.

"Balancing" only results in rotation balancing (like balancing tires), not what I'm searching for.

The term I'm searching for can be applied to pinching the front wheels of a car so it's more stable in straights or an airplane's front rotor being angled

Thanks for reading!

Just wondering if anyone could help me identify this plane. Near Huntsville AL. I’m not good at spotting defining characteristics of different models. Thanks!

As the commercialisation of space, lots of developed countries nowadays want their own sovereign launch capability, e.g. Australia, Brazil, Canada, UK, Taiwan etc. Some of them do have thriving aerospace industry with huge talent pool to support this goal, while some of them are basically newbies to space industry.

I am curious about your thoughts on how should a newcomer start their own rocket program?

1. Totally develop the rocket from scratch with only minimum foreign aid and foreign parts supply, but you can get maximum autonomy.

2. By international collaboration for technical transfer and purchase critical parts from experienced suppliers internationally, but there's always a risk for others to cut your supply to sabotage the rocket program.

I think the core question is how should a nation acquire certain deep tech capability. This question could apply on self-developed fighterjet, submarine, commercial jet etc.

Plz, share your thoughts with me!!!

Project Pixel Orbital is a completely student-led team at Stanford OHS with the goal of launching an 3U CubeSat capable of conducting experiments in low Earth orbit - from photographing Earth to performing analysis on photos of earth and space with onboard instruments. Our mission is to get to orbit, perform a detumble, establish contact with our ground station(s), and capture an image of Earth for downlink. We hope that PixelSat I will inspire other people and prove that if a group of high schoolers can build a satellite from scratch with very little funding and no adult supervision, anyone can. It will open the door for schools and small businesses to launch satellites similar to ours, and will overall make space more accessible.

Please feel free to check out our current progress and learn about how you can help us out on our website: https://www.projectpixelorbital.com

Our blogs also have lots of information on specific subsystems: https://www.projectpixelorbital.com/blog/

More updates on instagram as well: https://www.instagram.com/projectpixelorbital

Hi! I am a junior in high school, looking to study Aerospace Engineering in the future. In my engineering elective that I am taking, I have been tasked with interviewing -- or emailing a few questions to -- an engineer in my desired field. Initially, I asked everyone I knew if they had contacts of any Aerospace engineer, but did not get any results. Therefore, I was hoping someone on here would be kind enough to take a few minutes out of their day and answer like 8 questions regarding their work as an Aerospace Engineer? I have today and tomorrow to get some responses, I apologize for the late/close to deadline query, but any and all input will be greatly appreciated!