Showing the CAD timelapse was much appreciated. Don't be afraid to lightly edit the raw timelapse. I'd recommend experimenting with slowing or pausing the timelapse at times, just to make sure what you're talking about is still in the background and the video hasn't moved on. Perhaps also you could occasionally annotate the raw video with arrows or some such for a little bit of added clarity. Hopefully that sounds possible as a way to improve production without causing undue editing burden. Cheers! What great content!
I really love your videos. It's not just that you explain the stuff it's that you give refrences for designing with things like o-rings. Often researching where to find that stuff is more effort and time than actually doing it.
Building rocket engines sure is expensive, especially if you don’t have access to a machine shop (as was the case when I tried building my own liquid-fueled rocket engines). Have you considered putting up a Patreon or something similar where people like me can help fund your engine development? I’d certainly like to do my part to live vicariously through you!
I'm interested in the fact that engines are usually started oxidizer rich. My basic knowledge would suggest me to stay always away from ox rich flames. Why is it done?
@@theophrastusbombastus8019 Engines are usually run oxygen rich when they are running Kerosene in a staged/closed cycle, they cannot be run fuel rich to spin the pumps, as the Kerosene will polymerize under incomplete combustion, coking up the plumbing and injectors.
@@seanbaskett5506 as Mr Garcia said you need to avoid coking only in the preburner, in the combustion chamber oxygen is an heavy molecule and very aggressive so a ox rich flame would reduce your efficiency and make it difficult to protect the walls from oxidation
You might want to consider researching internal combustion engine valves, their required shapes and operating forces and pressures and the methods for mating valve and seat by grinding both in situ. Good luck!
Beat me to it with the grinding. The idea is that you make a decent fit, and then spin the sleeve against the seals with some fine grinding compound and the faces grind each other perfect matching faces.
Hey Charlie, looks fascinating 😉 do you consider the thermal effect on the spring stiffness k when cooling the injector with the oxidicer? Looks like a very delicate game of load balance!
everything is sooo much clearer when you show some sort of animation, like when you talk about the gas path and seals at 7:08. you should do that much more.
For those who do not know. You don't need to buy solid works for CAD. As he mentions Fusion 360 is also a very good CAD design software. I have used Fusion 360 and it is really good. Besides the program is free for all hobbyists, although the free version does not have all of the features.
Great video! Can’t wait for the next one! I actually understood what you were taking about this time and I think that has to do with your speech pacing a little which is good
Hard starts more specifically happen due to excess of fuel vapors at ignition, best way to mitigate is to start with an oxidizer rich lead in. The throttling co-axial pintle is probably a massive over-kill for this type of project, the main reason its used is to negate combustion instabilities that occur in larger motors due to poor atomisation/vapourization & mixing. You don't really have that issue in this sized motor.. Could probably have saved a great deal of complexity & machining cost by having a simple static pintle element & two throttling control valves. BTW, have you considered perhaps getting this into a kit form for those without engineering degrees? Maybe can get it up on kickstarter and those who want to reserve kits can fund the kickstarter?
If I have difficulty with the pintle sleeve, I'll definitely drop the dynamic pintle. For the meantime, it's an interesting thing to work on. The engine won't be throttling, even with the dynamic pintle, at least at first. I'll be machining everything, so luckily there isn't too much money to waste on job-shops. There is almost no chance of a kit. Something like this could be dangerous to people who don't know what they're doing and the market is small, especially since it would probably cost well above $5,000. I'm always happy to help other hobbyists though!
Keep going Charlie ! Nice info! looking foward for the machinning videos. If you have a place were we can rotate image from the parts designed that help hobbysts with no engineering background
Question: depending on the TWR will high G loads at max thrust effect the function of moving components inside the engine? Do you need to account for G forces or are they negligible compared mechanical advantage given by the engines pneumatics and pumps?
"But that's just a machining problem" this guy is an engineer. Machinist side "why the heck does this guy want to hold 1 hundred thousandth on these edges and call out fractional tolerances everywhere else" btw, if you happen to read this, I would love to pitch a new design at you to discuss feasibility.
There will indeed be a seal there, however I'm starting with a flow test rig, so designing chamber seals is premature. The reason I did the face seal on the hat now is because I know that will be a flat plate on both the engine and flow test rig.
Really enjoying watching your videos. I have always been interested in Rocket Engines and wanted to try building one some day. You no longer are working for SpaceX? Cheers Willy
I would not have the time or be able to talk to you if I was. Hopefully I'll have the opportunity to work there again though, some of the best people and most interesting problems I've ever seen.
I like your use of CAD. It does help illustrate nicely. BTW, I noticed that most of your Launch Patches have 4-digit numbers on them that I don't remember from other patches I've seen from SpaceX and I can't find reference online. What are they for?
hey so at 7:53 there is a picture of the injector but i dont understand how you shut it off bc i see you use gas to keep it opened but i dont know how you close it
Super cool you share your advencement with us! Thanks a lot for that! I just had a small question : how much injectors will your engine have? On the first video it seems to have only one but this seems not enough to me
Just the one pintle. That isn't a problem though. You can just change the size of the pintle element to get enough fuel flow for the desired thrust level.
@@AstroCharlie Ok thanks for the answer! At the beginning I still had in mind the thousands-holes injectors so when you started talking about control the flow in the pintle injector, I was just like "Well... That will make a lot of motors and wires!". But one injector makes this really more logical and it makes sense since these types of more complex injectors (compared to the classic showerheads) allow for a better mix and atomization coupled with this control opportunity
Regarding that sliding seal, I notice there aren't any wear rings in the design. Are you not worried about unforeseen side/radial loads during actuation and firing wearing away tge seel? Or possibly even under compressing the seal on one side? I'm asking cuz my team is trying to design a sluding seal (for other applications) and would value your opinion on this. Also regarding the startup, doesn't the Delta 4 start the hydrogen flow first, which causes its iconic startup fireball?
How are you planning on maintaining target lambda? As far as I can see you have orface size and pressure to work with as variables. Unless you do some sort of pwm of the injector.
@@AstroCharlie i have a long history with control system (ecm calibration) in the automotive world. If you have a way to talk via email or etc I'd be interested in a conversation and approaches you could take.
What would you do if the pintle sleeve that covers the oxidizer injectors is to thin to hold the pressure? I assume you cant make it thicker because it would block the fuel from hitting the oxidizer?
I've already accounted for the hoop pressure on the section covering the LOX ports. If I did need a thicker sleeve I could also change the size of the fuel orifice, it would be a less wide slot due to the larger diameter though.
Nice, but why go with pneumatics rather than hydraulic? I would be concerned about resonances at partial throttle settings, particularly at very low settings. The fuel 'valve' section has a feedback loop, as when it is almost closed it is a restriction, meaning fuel will accelerate through it and be at low pressure through that section, closing it further. It is basically how a woodwind instrument works. Is there any reason you couldn't just use your fuel instead? The seals would need slightly redesigned, but many of your leak paths wouldn't matter anymore anyway and leaks wouldn't drain pressure so fast. The other potential issue I see is that the pressure in the spring chamber is not actively controlled (at least in the schematic shown). It will end up at some equilibrium of the two seals leaking, and there will be some delay in reaching it. That could make understanding where the sleeve is difficult, because it will be dependent on camber conditions and seal conditions as well the pressure input.
I won't be throttling this engine unless I upgrade the sleeve to be hydraulic or electrically controlled. At full throttle the sleeve has a lot of travel before it starts to shut either orifice, so resonances will be fine. I didn't want to use pure fuel pressure so I could pressurize the fuel and start the engine separately, as well as run pneumatic tests without a full fuel plenum. The back side of the pneumatic cavity will be vented to ambient, so no pressure can build up there, and the pressurized side of the pneumatics will be maintained at pressure by a regulated supply. Your concerns are all real though, and I'm only getting away with some of the sketchy things I'm doing because of other design choices.
@@AstroCharlie Thinking further about it, do you even need the actuation integrated into the assembly? If you are going to have one side vented to ambient anyway then a mechanical linkage out doesn't affect your seals.
Way way way too fast, 0 diagrams. Disliked and unsubed! The first video was easier to understand. This video looks like a quick recap of an entire semester of a university course on 2x speed. Please slow down and add diagrams
