Solid Rocket Motors 1.5: OpenMotor Tips

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.

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.

Charlie it’s been 3 months where are you

could this software be modded into KSP? would be a nice addition to procedural SRBs

I love your videos mate, keep it up

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..

please upload more videos in these series !!!

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?

Hey, are there any plans to add KNSU to open motor?

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.

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

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!

Hi Charlie what is the software you're using for your testing & simulation?

I'm here. Sub'd. I blame Tim :-) -Jake

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!

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.

is there a way to change units into metric system?