Liquid Rocket Engines 8: Aerospikes

[@CanineDefenseTechnologies]

0:12 over budget and under schedule. Sounds like any rocket project to me 😂

[@doco6186]

Hey Charlie, Very informative and interesting video. Boy how much rocket engine designs have changed since I was at MIT. I really videos that go have this much depth.

[@almuhanadahmedsaidalhashmi4696]

thank you very much mister for this design lectures

[@quaternarytetrad4039]

With this power I have learned I shall rule the WORLD......as soon as I actually understand the math! XD

[@concon3055]

Did I watch it? Yes. Did I even start to understand it? Not even sorta. Did I enjoy it? Also yes.

[@jeromec7367]

Very interesting video! Respect for making such a technical desing process understandible. Eventhough I didn't understand the meaning of the equations, I got a view of what the maths behind an aerospike are. Thanks!

[@michaelmoore1403]

Very interesting I am totally nerding out on this. I think the shape you were referring to is "flustrum" rather than "frustum".

[@AstroCharlie]

Pretty sure it's a 'frustum' as google tells me that is defined as the portion of a cone or pyramid which remains after slicing it with two parallel planes. I'm unable to find a definition for a 'flustrum' Glad you enjoyed it!

[@michaelmoore1403]

@@AstroCharlie fair enough

[@vedantmomayascience]

Hey awesome content and love the way that u cut right to the useful parts of the video. Can u plssssss make a video about how a high school student can learn about rocketry without any prior knowledge and with the use of only the internet because honestly for some parts of the video I'm lost and I need a formal education on rockets and online is the only way for me .A detailed video from how to go from beginer to expert would be awsome

[@MichaelFairhurst]

It's hard not to love aerospikes, even though they aren't necessarily practical in the real world. Even as a hobbyist, where the efficiency over a wide range of pressures is irrelevant, haha. Thanks for sharing, really cool to see how it's done!

[@theelectricwalrus]

Boy am I glad I took compressible fluids

[@Ameliaross106]

Ahh to much from Tim’s rocket pollution video to this ahh.

[@praveenstark5777]

Can you please tell me what book you referred for aerospike nozzle

[@davidmcintosh5441]

Fantastic video man! Just a quick question: Did you by any chance use Angelinos 1967 paper? The maths looks very similar but if not could I ask what resource you based this on? Ive been looking for a definitive paper on the MOC for aerospikes for a while and have only found papers by the likes of Rao but nothing actually explaining the methodology. We also aren't taught MOC in my degree so its been rather challenging!! On a slight tangent I cant wait to see your final rocket design, keep up the great work!

[@AstroCharlie]

Hi David, I did not use Angelinos' paper. I used my reference notes from my propulsion class (MIT's 16.512, Paulo Lozano) on method of characteristics and worked from there.

[@davidmcintosh5441]

@@AstroCharlie Thanks so much for replying man! I found the notes, they'll definitely help in developing my understanding!! Kinda really wish we had this class at our uni! 😂

[@davegriffith6786]

​@@AstroCharlie Hello Charlie Just found your Liquid Rocket channel. I've been building amateur rockets since 1973 I hold a California class 1 rocket pyrotechnic operator. This is for Liquid propellant rockets which I qualified for back in 1993. The reason I'm writing you, you remind me of my old rocket buddy Dan Ruttle he was an engineer for the Apollo program. I haven't seen since 1995. He built in my machine shop one of the first liquid propellant amateur rockets in the world that was launched in 1987 the propellants were Nitric Acid and Furferal alcohol which are hypergolic. Here's a video kzbin.info/www/bejne/qZuWk3xjZbOqqcU Hope to hear from you. Dave Griffith

[@davegriffith6786]

​@Charlie Garcia Hello Charlie My email is [e-mail]

[@FlorianGronau]

Thanks for this nice in-depth video! How would you adapt your calculations, if your shroud would not have a sharp corner forming the throat, instead forming a divergent section after the throat? So you have Mach=1 at the throat no matter what. Now let´s say, a divergent section formed by the spike and the schroud accelerate the flow to M=1.2 before the shroud has then a sharp corner. The contour of the shroud interacts with the supersonic flow in that case and actually forms a bell-nozzle in 2D-perspective. In 3D-perspective it is rather a toroidal convergent-divergent nozzle followed by an aerospike. => Would that affect the contour of the spike itself? I assume it does, because of the higher Mach number at which the P-M-Expansion fan arrises. => How would you calculate the contour of the shroud? => Would you expect an increase in efficiency with that setup?

[@AstroCharlie]

In this scenario your first characteristic line would be at whatever the mach number dictated by the exit velocity of the diverging section would be. The spike contour would depend on the contour of the diverging section. The diverging section would qualify as a complex region, and would need analyzed using an iterative analysis. The video calculating the contour of this geometry would easily be 3x longer than this video, with a few hours of math homework before that. I would not expect an increase in efficiency. In general, more 'stuff' is less efficient. The newly added diverging section would have wall losses, cooling requirements, weight, etc, and in theory would perform the same as if you had not added it.

[@FlorianGronau]

Thank you very much for your quick response, @@AstroCharlie!! Really appreciate, that you looked into my comment :-) I guess even if there was an increase in nozzle efficiency, the downsides you mentioned would most likely overcome the advantage of a few ‰ of theoretical efficiency leading to an overall decrease in efficiency (especially thinking of wall-cooling) again: thanks! and keep the good work up :-)

[@markayala7752]

nice , can i ask what simulation you use to design and calculate the math ? thanks.

[@AstroCharlie]

Just an old TI-84 calculator. A python or matlab script would have worked just as well.

[@sergejp4727]

Hi, i was wondering if you can give me some advice on how and where to start learning about rocket science and rocket engines, like where did you learn the math and all, any help would be appreciated

[@_mikolaj_]

Always delayed and overbudget... Wait, aint that standard in space industry?

[@AoriDeAof]

Watched it more than dozen of times and still cant understand this pretty nerdy stuff. Just cant assemble the picture in my head even tho instructions feel pretty straight forward most of the time. You talked alot about angles but length of mach lines just mentioned and threw away i believe. I probably can construct geometry out of points with angles i got by knowing that i want every refracted mach line vector to be pointed axially. And also i want to avoid steep turns (and collecting bunch of vectors in one point) to not put under stress the spike itself. But all of this is simple geometry and a little bit of common sense using provided information. I guess math behind designing chamber and a throat is worth it but this... P-M eq at the beginnig has nothing to do with pressure (pressure is basicly needed to know under how much loads spike is to caluclate thickness and material of the spike wall), we just put in (target) mach number to get desired angle and then somehow need to calculate how far from lip that angle point is. But how? How do i find that point easily if the only things i have is two angles of a triangle (90 and P-M) but no lengths and also i dont know how much will exhaust turn around a choke lip at given flow speed? I understand that i might be a 'little' stupid and/or there might be unmentioned specific information.

[@AstroCharlie]

P-M (prantl-meyer) is related to pressure through the isentropic flow equations for mach number from pressure ratio. I'm not sure what you mean about needing to find a point from the lip.

[@danielvazquez8966]

Hi Charlie ! Thanks for taking the time to do this video, I started following your channel after watching some videos from everyday astronaut and man yours are also really cool ! I have a question I hope you have some time free to answer, its about the epsilon parameter on the last formula for Rx/Re, could you tell us what it stands for ? Thanks again !

[@AstroCharlie]

Epsilon is the expansion ratio parameter, throat to exit area ratio.

[@Graham.556]

Hello

[@robertsteinbeiss8478]

just notice this is becomming a lecture, .... wait get my pen and paper ... like it yeah full 90 minutes

[@stekra3159]

Hey Caely I love your in deephe vidios on rocket egenig I hoop you ceap the sieres going. Your vidios are more in deep then Scott Manlys and taht says somthing.

[@noahhastings6145]

Yay!! The video that was promised!

[@yottaplex2239]

how do you know if you flow is choked in a bell nozzle, knowing chamber pressure, ambient pressure and throat area? How can you therefore design a small enough throat to choke the flow?

[@ElectricEvan]

I found this fascinating.