Scratch Building High Power Motors

[Mister Monaco]

Hi all. I'm an aerodynamicist at Lockheed, and I'd like to build my own high power rocket motor. I've been collecting artillery shell casings and military steel storage tubes for quite a while now. I was thinking about using a 81mm mortar tube or a 105mm artillery shell casing to build a high power motor. Do I need a NAR certification for HPR?

 

[Mister Monaco]

I plan on using the motor recipe Grant Thompson used for his Sugar Rockets

 

[boatgeek]

NAR won't work for research propellants. Tripoli HPR certification will, at Level 2 or higher.

Please, please, please contact your nearest Tripoli prefecture (aka club) and get some mentoring. It will save you time, money, and perhaps disability. Seriously. Talk to some people who know what they are doing. PVC is a terrible idea (doesn't show up on X-rays if the casing blows on you), as is steel (can fragment if it blows). Moving from the E motor in the video to HPR is a giant leap and not easy.

 

[Mister Monaco]

Wait so those sugar rockets can explode?

 

[Mister Monaco]

https://go-armynavy.com/military-su...us-military-40mm-mk-3-shell-casing-short.html
The plan is to fill this shell with the sugar rocket propellant

 

[Mister Monaco]

And move on to larger 81 and 105mm shells later

 

[boatgeek]

Wait so those sugar rockets can explode?

I have not seen it myself because I don't do research motors. However, when the motor is burning, the pressure inside the case is what makes it go. If the nozzle hole is too small, pressure can build up enough to where it will explode. Seriously, you are headed down the path to either disappointment, injury, or both. Please get a mentor who knows what they are doing.

[edit] Also, to fly any of those motors, you will need an FAA waiver. Unless you have a field hanging around and you want to spend a few months waiting for approval, you'll need to fly with a Tripoli club. You won't be able to fly your own research motors with a club unless you have the Tripoli high power certifications.

 

[jsdemar]

Hi all. I'm an aerodynamicist at Lockheed, and ....?

Post a link the your LinkedIn page.

 

[Maxwelljets]

The method shown in the king of random video is one that was abandoned by almost all amateur rocketeers a long time ago. The pressed powder can form cracks and voids inside it, especially as you scale up. When the burning surface reaches one of these cracks, suddenly the burning surface area is greatly increased which almost always leads to the motor blowing up.

The other responses are correct. Reach out to your nearest Tripoli prefecture and get your high power certifications. Once you're level 1 certified, you can join the research subforum here, and once you have a level 2 Tripoli will allow you to fly homemade rocket motors (as long as they follow the rules laid out in the Tripoli research safety code).

Alternatively, if you're in the SoCal area, you could join the the Friends of Amateur Rocketry.

 

[DaveW6DPS]

Making propellant an forming it into rocket motors is not a simple task, and some have had disastrous results.

Start with commercial motors, and learn how things works. And definitely find a group doing research motors to learn from.

 

[JJSR]

Wait so those sugar rockets can explode?

 

[cbrarick]

Let's see if I can spot (some) of the problems

1. tripoli doesn't allow PVC motors
2. tripoli doesn't allow micrograin (e.g. pressed motors)
3. compressing grains of any type is inherently extremely dangerous (one of the other micrograin motor packing procedures actually encouraged to do it BEHIND a bunker, with full protective gear on. the people were stationed behind the earth berms)
4. ANY motor could energetically disassemble, if the nozzle plugs. Dry, compressed fuels are especially vulnerable to this as there is little in the matrix to keep it together.
5. using a grinder, especially without a sparkproof motor. is a horrible idea with ANY oxidizer. Don't become complacent because it's not so bad on this one.
6. Spent shells probably aren't good for motors as they have been exposed to high temp & pressure, are only designed for single use, and you don't know the strength of the case
7. tripoli doesn't allow steel motor cases


However, we do make sugar based motors using a completely different technology. Not many people do because they lack specific impulse. More common are AP based motors. You need to gain access to the research part of the forum to see how.

At any rate, abandon this! if you want to make motors, join tripoli, get your L2 and find a mentor. You can avoid a lot of expensive and potentially deadly results. Making motors is not a benign act - there are dangers, but also safety procedures to mitigate them......

Good luck

 

[Ez2cDave]

Wait so those sugar rockets can explode?

Solid-Propellant hobby rocket motors do not "explode" . . . They can over-pressurize the motor casing and "CATO" ( not an explosion ). They do not "detonate", they "deflagrate".

Dave F.

 

[prfesser]

Solid-Propellant hobby rocket motors do not "explode" . . . They can over-pressurize the motor casing and "CATO" ( not an explosion ). They do not "detonate", they "deflagrate".

Dave F.

Thank you. TRA and NAR spent close to 3/4 million dollars and 10+ years for a judge to decide that APCP didn't qualify as an explosive.

I forget who told me that essentially, you can tell if a rocket motor (e.g., those double-base propellants) detonates because there is no longer a motor nor a thrust stand.

Best -- Terry