Solid Rocket Motors 1.5: OpenMotor Tips
ฝัง
- เผยแพร่เมื่อ 10 ก.ย. 2019
- Hi Rocketeers!
One of my Patreons requested a video that went more in depth on failures that can occur in simulating solid rocket motors. This video shows some of the ways a motor design can be found deficient in simulation before you build one.
Links:
github.com/reilleya/openMotor...
/ charliegarcia - วิทยาศาสตร์และเทคโนโลยี
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Hi Charlie, nice video. The reason our motor CATOed at 0:55 was due to overpressurization. The cause of the overpressurization was the dual pulse design of the motor...like a 2-stage rocket with a single nozzle. The concept used a pyrotechnic mid-bulkhead between the two motors. When the aft motor was ignited at launch, it would also ignite the mid-bulkhead that in theory, would take 15 seconds to burn through. The aft motor would boost the rocket and coast through dense atmosphere for ten seconds, then the forward motor would fire sending combustion gases through the burned out aft section and out the nozzle. We had two problems making this design work: 1) heat soak into the motor case from the aft motor weakening the case and 2) failure of the mid-bulkhead that would suddenly increase the Kn drastically, as seen in your video clip of that motor test. All of our singlepulse motor tests were successful that did not include this dual burn design. We have since moved on to conventional 2-stage rocket design (two nozzles)
"Always assume that it is going to explode," is damned GOOD advice.
Astronautics, issue 38, October 1937
Dear Charlie: I hope all is going well. I know how hard it is to maintain school and these long term projects. Just wanted to remind you that you inspire us and that that we wish you luck in whatever it is that is ahead of you that needs overcoming. Godspeed.
I love your videos mate, keep it up
Charlie it’s been 3 months where are you
could this software be modded into KSP?
would be a nice addition to procedural SRBs
please upload more videos in these series !!!
I was thinking the other day that many of the fuels used in solid propellants are actually injected as a softer putty then dried. You can create 3d printers that use injectors for liquid materials like resins, clay or gels that are then hardened using various means. If you could find a clay or polymer/clay mix that was heat resistant and could be used in such a printer, then also had another injector nozzle for whatever material you were using in the solid propellant, you could make some really fancy designs for entirely enclosed solid rocket engines with all different types of engineered-shape venturis and different channels in the fuel to accelerate the burn.
Hey, are there any plans to add KNSU to open motor?
hi, thanks for the toutorial, can you make a video were you add a new propellant? thanks in advice
Charlie, first of all thanks for the videos and all the info you shear. I know it takes a lot of time and effort.
I am a beginner and I am building/designing my first motor (not made of sugar) and I have so many questions I would like to ask. But number one is how do you test the pressure inside of the 30mm motor? what soft do you use and what hardware? can i buy one on the bet or I should make one for myself???
Thanks
I'm here. Sub'd. I blame Tim :-)
-Jake
Again, nicely done video series. Comment: at 7:30 in the video you suggest not having all the grains burn out at the same time to avoid a pressure drop. If all the grains burn out at the same time you have little to no unburned propellant...I do all my BATES grain motors to burn out at the same time and never have unburned propellant left. Also, at 7:45 you say finocyl grains burn out over a longer period of time yet your graphic shows burning out at the same time as the BATES if you design it with deep 'fins'. Deep fins are to increase startup burn surface for high initial thrust/acceleration. Shallow 'fins' offer a monolithic grain a neutral burn profile with most of the propellant burning out at the same time.
Hi Charlie, I am not able to find an option to change the port design, is there any add-on or something? Please help. Btw the whole solid/ liquid rocket series is really nice. Please continue and complete the solid rocket series. Thanks!
Will you be adding other propellants to the program?
Hey Charlie.
I am using open Motor because I want to calculate the performance for my self built Rocket Candy Motor. As Propellant data I entered the Properties I could find on Richard Nakkas site. My Problem is, that the Chamber pressures seem way too high. Whenever I simulate I get two warnings:
"Max pressure exceeded" and
"Propellant pressure deviated from propellants entered ranges. Results might not be accurate."
Even when I make the nozzle as wide as the grain I get these warnings and a peak pressure of 3831psi. Do you have any Idea how I could fix this?
I am pretty interested in rocketry and when I grow up I want to go to MIT.. I am 12 years old and live in India..Sadly there are no facilities to launch rockets here so all I can do is wait and get to MIT..
In a similar situation. I recommend sims
Hi Charlie what is the software you're using for your testing & simulation?
is there a way to change units into metric system?
Hey, Charlie. I'm looking to use OR in my classroom with my middle and high school students. Do you have a Windows installer? I am looking for a simple way to install this app, for classroom use...where we have nothing but Windows 10 PCs. Thanks!
YES!!!!!!!
Have any interest in doing some jet experiment videos in the future? I have some prototypes you might like to try out. It's a mini so it won't be dangerous, expensive or hard to build. I have EDF afterburner designs I'd love to see made and tested. I don't have my own channel I actively run but I do use my tube account to archive informative videos of use or research.
I am aiming for a long burn time, medium thrust motor. I ended up with a 38mm G50 with a burn time of 3.12 seconds and an average thrust of about ~50 newtons. To keep it G impulse (I do not have L1 Certification yet) I had to over expand the nozzle a little. Are there any signs that I should be aware of that might indicate flow separation? The best way I could test it was to increase the exit diameter further and see how the thrust changes, but I am not too sure what I am looking for.
openMotor will not advise you about flow separation. Why did you overexpand the nozzle instead of using less propellant?
@@AstroCharlie Because then the total impulse became too high. Though I can reduce the propellant further and get slightly longer burn times, however that means sacrificing a bit of thrust. I am trying to find a good balance between something that will look cool, and something that can preform well.
You mentioned a concerning KN value of around 2.0 lb/ft^2*s but your units show are shown in lb/in^2*s. Is this concerning mass flux in units of inches or feet?
Also you said that to decrease the Kn, we should increase the size of the port, but wouldn't we want to decrease the port size to decrease the surface area? Thanks
Hi @bnl1852
2 lbs/in^2 is the correct 'concern' threshold for core mass flux, although I'm aware of motors that have operated at as high of a value as 9.0 lbs/in^2 with appropriate design on both the internal ballistics and propellant. Appropriate KN values (which is a separate design concern) are usually in the 150-300 range, depending on propellant.
Increasing the size of the port raises the KN but improves the core mass flux as there is more area for the gas to flow.
@@AstroCharlie Ah this makes more sense now, thank you for the clarification.
I have my first job interview tomorrow and wanted to brush up on SRM design, you're videos have been extremely helpful so thank you!
Hello Charlie, great info. I downloaded OpenMotor to my mac and I have the icon but it refuses to open. Not sure why or what to do about it. Any suggestions? Thanks
I could probably come up with a few ideas - but that isn't much information. Can you make a bug report on the repo?
@@AstroCharlie I also downloaded version 4.0 on my Mac but it says downloaded from an unknown developer is that normal
How do you download and install the software?
For a solid rocket motor, if the effects are very transitory at the start of the burn (i.e. an extremely hard start), how much of an issue is a significant rise above operational pressure?
I mean, it sounds like it shouldn't be catastrophic because of any of the things you mention here, which is nice, but it sounds like the kind of thing which should cause issues that would either need dealing with or would be a ruler-outer. Would structural failure of the propellant ever be much of a concern when it hasn't had the time to burn away yet to any real degree?
Extremely hard starts are probably the second most common cause of failure, after heat related failures. A significant rise above average pressure is fine, as long as it isn't a rise above design pressure.
Structural failure of the propellant can happen any time.
Thanks, that's very helpful to know. I'll just start testing it softly and carefully work it up then.
Does anyone know how to add new propellants? I added a density but do not know how to add a characteristic velocity. It also says "Tab #1 has the same minimum and maximum pressures."
The characteristic velocity is calculated via thermodynamics or test data. Software like Propep can help you calculate this. 'Tabular' propellants are set up in the software to have more complex behaviors, but they require those ranges to be defined. A simpler propellant just has a single behavior from some minimum to some maximum pressure.
Sweet
CHARLIE GARCIA/BPS SPACE CROSSOVER CONFIRMED!
Hey. Since you know a lot about rockets, could someone ease tell me why there is often a pipe going to the end of the nozzle. What is it used for? Is I necessary?
That pipe typically carries the fuel to the bottom of the nozzle to flow it between the layers of the nozzle to keep it cool. This is called 'regenerative cooling' sometimes this also carries the turbine exhaust.
Hi Charlie. I,m having trouble shooting with version 4.0. The edit propellant tab is not accessible. Have you noticed this and do you perhaps know how to get around this glitch? Support will be much appreciated.
Please submit a bug report on Github.
Tell us how to make APCP rocket propellent
Do you have AP?
@@ratneshsoni9045 Ammonium perchlorate composite propellant
@@short_with_roshannonoffici1150 I mean do you have ammonium perchlorate
@@ratneshsoni9045 nope
Can you tell me name of the software?
It's called OpenMotor and it is linked in the description.
Where are you bro
Can you use openMotor for liquid rocket engines ?
Not really, there is no way to simulate the fuel being injected into the combustion chamber, openMotor uses grains, which is a solid and hybrid only thing.
Oh alright thanks :)
6:18 Hey Charlie. Great Video! I just wanted to point out that your voice could not be heard properly during that rocket-engine test clip. Maybe lowering the video sound might have helped. Oh, and also, RIP earphone users in a same sense haha.
Can you translate measurements in your vidios to metric system pls
Feel u
just download OpenMotor and run it yourself with SI units. (or use google to convert, google will convert most SI units)
1" = 2.54 cm, you are welcome
And please make a few videos
Love from India , osum video.
#buddytech
What does KN stand for in German?
The Russian analogue of this term is the "k-phase", where k is the abbreviation of "critical" ("Критический" - Russian language). I think that in German this coefficient also comes from "critical" (kritisch- Deutsch language)
It stands for Klemmung which is German for 'clamping' or 'choking'
Fascinating, to hear about the Russian root. The German origin is from clamping or choking and the word is klemmung
@@AstroCharlie So, KlemmuNg?
Is it legal to manufacture and sell rocket engines in an online store? (buyers have to have a license and they can't have anything in their crime record) I would sell the to big entities or students
You may not sell homemade rocket motors.
@@theredstonehive you mean solid rocket motors? I know that you can't sell those becouse (at least In Germany) they are under the explosive regulations. But it's different with liquid rocket motors,becouse the fuel itself isn't an explosive. I'd just be selling a hunk of metal with pipes on it. Would it be different if I sold the commercially, with a quality checked production line?
Hey charlie
Hello
@@AstroCharlie Haha
Anyone here who can recommend some books about hobby rocket building?
Even i also don't know but know only i started reading books so i recomend to use first rocket propulsion, ignition books
I wish amonium perchlorate was cheaper and easier to get. Oh well, at least they did a great job keeping it safe away from kids
It's Ammonium Percolate. Source of small quantities, is the active ingredient in 'Cold Packs' in the Bandaid section of Pharmacies.
@@paulmoffat9306 Oh sorry I meant that. Also yes I am aware, but the very pure high quality form is optimal for a rocket propulsion system. And opening a bunch of cold packs will be a bit of work. Well that is still a option though.
@@paulmoffat9306 ammonium perchlorate is NOT found in cold packs. That would be ammonium nitrate. Even more commonly found in cold packs is ammonium chloride. You would preform a double replacement reaction with potassium perchlorate to yield ammonium perchlorate.
It is actually ammonium perchlorate, I don't believe that it is used in cold packs.
@@AstroCharlie @Paul Moffat @Magic Smoke RC yes my dad uses them at his clinic, I double checked, cold packs have ammonium nitrate, not ammonium perchlorate. Gosh I better look very carefully to make sure it's ammonium perchlorate when If I ever buy it. For sure I won't be making motors till I fully understand the chemistry (that's in a while). Thanks for telling me though 😀
Here cause of Tim..... I’m not completely mad. Will be back. Sub’d..... I’m pretty sure I’ll be back.... not sure why..... Yeah I’ll be back.
ALL U DID WAS SHOW SOME SOFTWARE
No guide on how to acquire and run the software.