An idiot swinging around a 100 AMP plasma arc!

Building the Thrust Stand

It took about a week from concept to build to get my thrust stand built. I had a hard time deciding between a horizontal and vertical thrust stand configuration. After weighing the pros and cons along with my experience using a horizontal test stand, I chose to go with a vertical setup because the ultimate aim will be to design a flyable motor. I also made sure to allow the test stand extensibility so that I could mount a rail in the future and test the entire rocket in a flight ready configuration. Another driving consideration was the testing of several experimental motor designs. My horizontal stand was troublesome anytime my rockets would not start because the chamber would fill with fuel that I would have to manually clean out between tests. The vertical position of the motor will help prevent a hard start from accumulated fuel.

The design is centered around a 1.5" x 1.5" x 1/8" thick walled square tubing backbone welded to 2" x 2" x 1/4" walled square tubing. The reasoning for such a strong base is that if I am testing a motor generating 1000 lbf then I will have to hold it down with at least that. Having the thick legs will allow me to weld on brackets that I can bury underground or mount to a concrete base.

There is a 24" x 20" shelf that will hold tanks and electronics. The verticals supporting the shelves were specifically one piece welded straight to the base so that they can act as a structural element should I need further reinforcement in the future. On the 1 ft over hang and 3 foot face there will be blast shielding to protect all of the electronics and isolate the pressure tanks in an explosion. I also plan on putting blast shielding around the pressurant tanks because they are simply 3 inch OD with 1/2" walled 6061 pipes that have caps welded on the ends. They aren't exactly hydro-testable.

I built a CAD model using FreeCad then using the FEM workbench I ran an analysis with 5000 lbs of force on the overhang. The upper surfaces of the legs are fixed and the trailing edge was fixed to act as a fulcrum. 5000 lbf was empirically determined to be the maximum amount of force before the stand started approaching plastic deformation. I only intend to test up to 500 lbf currently so there is plenty of a FoS to account for my shoddy welds (I've never stick welded before) with my homemade stick welder.

You can see my welder here

This was a great chance for me to learn how to stick welding because of the thickness of the
metal. Not having to worry about burning through allowed me to focus on the molten puddle. I first tried with 1/8" 6013 welding rods but it turns out my welder didn't have the amperage to maintain an arc so I went to 1/16" 6013 and it struck great but not much penetration so I settled on 3/32" and this seems to work just fine. What I lacked in quality of welds I made up in quantity!

A shameless presentation of unarguably my best weld on the stand

FreeCad CAD Modeling & FEM Software

This was my first time  using FreeCAD .I don't really know much software but I do have a lot of CAD modeling experience so that I at least knew how things should work. If this is your first time CAD modeling, I would recommend using a free trial of SolidWorks or ProE first because there are a lot of step-by-step tutorials at YouTube University. Once you get a feel for the flow of these softwares then you could move onto FreeCAD because there is not a lot of feed back and the tutorials online are fairly lackluster. At first I was having a really difficult time trying to understand the stress distribution in the model because of a hot spot that was created right next to a non-critical member. It was blowing my scale out of proportion.

FreeCad Default

I knew that this was useless to me unless I could figure out a way to adjust the color limits. So I poked around the source code for a few hours, I've never seriously coded in python, and came up with a macro that can probably be done more elegantly and in one line but it got the job done:

values = App.ActiveDocument.Results.StressValues
filtered_vals = []
Ulimit = 250
for v in values:
if v > Ulimit:
filtered_vals.append(Ulimit)
else:
filtered_vals.append(v)
App.ActiveDocument.Results.Mesh.ViewObject.setNodeColorByScalars(App.ActiveDocument.Results.NodeNumbers,filtered_vals)

I chose the Upper limit of 250 MPa because that is roughly where you are going to start running into plastic deformation and this is the result:

Much better

It improved my visibility into the stress distributions greatly!







I actually learned the most about the software after poking around under the hood. Overall, it is not a bad software if you already know how the software is supposed to perform and you can't beat the price. Free always fits in my budget!

V2 up and running

After a few days of runs, we finally got the engine to run correctly.  Some of our tests burn over 10 seconds which is about as much as I can squeeze into the tank. There is a YouTube play list with all of the test runs including some good mach diamond shots during day 3. HolliStar Liquid Rocket Engine: HolliStar Liquid Rocket Engine: http://www.youtube.com/playlist?list=PLPs8paqlFtFy6ad9Riu9larwPlQGtC6eC

Rocket Test Aftermath and Analysis

Surprisingly the coolant line burst and the brass fitting exploded.

This was the same hose that blew up in my face a few weeks ago.... apparently it is back for round two!

Its fairly safe to let the excess methanol burn off.

First look inside the combustion chamber

The injector plate is unscathed.

One good note is that the hottest part of the rocket (throat/nozzle) are completely untouched.

Exactly what I thought would happen happened. When I mounted the rocket on the thrust stand, I noticed that water was leaking into the chamber. I spent two days running through the scenario in my head and what happened is that the coolant is ~50 psi and the chamber is 300 psi. The hot gasses pushed their way around the gap and into the coolant line which causes the water to boil. The steam doesn't cool at all so a hot spot forms which melts the aluminum. This progressed along the chamber wall until the hole was over the coolant outlet. The pressure then pushed its way into the line which cause the explosion and exploded the fitting.

Now that I know the concept works (when everything is sealed properly) onto V2!

SUCCESS!!!!!

HolliStar hot fire was a 100% success! Even the fireworks at the end were exactly as planned!

After two weeks and $187 of nitrous, an oxidizer solenoid bypass was used to get an igniter to burn in the chamber. Then comes the countdown 3...2...1...
The engine boomed into a roaring thunder that the recording does not justify.... FINALLY, its resounding bawl unshackled me from the cantena of unsuccessful attempts that had burdened me with doubt.The engine operated exactly as I spent over 400 hours designing, building, and assembling but it would never have been possible without the help that I got along the way. It was a wholly humbling experience.
Assuming that because I am an Aerospace Engineer, I am rocket scientist, was entirely false. The knowledge is potential. Conversion of potential to action is power. I can see now that all of the education that I received was simply following in the footsteps of great men. However, an Aerospace Engineer along with the help and support of:

Most importantly, thank you Lexi Soya. I don't know how you were able to tolerate my 24/7 rocket building schedule. You not only supported my investment of time and attention but encouraged me to keep pushing for my goal. There were many times where I came home simply defeated but you wouldn't allow me to give up...you and your contagious optimism. I didn't stand a chance and I thank you for it.

Thanks to Geoff Hollis, whom which the HolliStar Rocket is named after, because if he didn't teach me everything I now know about machining, it would have been impossible for me to build. He offered me his giant endmill, rotary table, indexing head, gallons of methanol from his slingshot dragster, his lawnmower battery, a military grade starter coil, welding of my custom tanks and most importantly insight for taking the ideas off the paper and realizing them.  Apart from that, he spent just as much time as I did rolling around on the floor getting it all to fit together and even lit the igniter in the video.

Brainstorming and Imagineering

Rick Pelfrey

Jim Kopasko

Suele Kabir

Electronics Consulting

Rhett Ward

Paige Harris

Dan Baumann

Unknowing Test Subjects

Branden Wright

Alex Soya

Logan Soya

The Mom Squad

Angel Brewer

Zee Soya

Encouraging Supporters

Rhett Brewer

Brandon Brewer

Jay Bracht

Emma Baumann

Jeff Gallese

Victoria McMurchy

Alex Cummins

Josh Cummins

Mama Cummins

Papa Cummins

Jon Thorton

NOW ONTO THE ROCKET!

I designed the rocket to operate for about 5 seconds and it operated perfectly through 3 seconds. I knew that there was a water leak into the chamber and that there would be a chamber burn through because of it. So even though the test ended in rapid disassembly, it went exactly as planned. I figured I may as well test how bulletproof my chamber since I was at it.

At start-up, you can see sparks from the aluminum melting where the coolant is leaking.
Next, the engine operates perfectly as the chamber heats up to half of the temperature of the surface of the sun.
Then the burn through happens.... fortunately the blast chamber held up!
Completion of a perfect first test run!

Though you can see 5 mach diamonds in the thrust, there were many more. The entire length of the flame had progressively weakening mach diamonds. I shot the video with a ND4 (Neutral density filter similar to sunglasses where I can take a 5 second picture in broad daylight) and it was still blown out by the white hot flames. I need to do more research as to how to record them.

Pictures of the aftermath and more analysis coming soon!

Day 29: WE HAVE IGNITION!

I spent the morning battling the leaky connection monster. After that war was finally won, I dragged everything out to the holding bay where we typically store the race team's tractor trailer (plenty of room) and gathered everyone who has been apart of the journey so far. The first test was with 91% IPA straight from the store. When I would run the fuel, there was a great flamethrower effect until I hit the nitrous. Then the flame went out... I tried a couple different combinations with the propane torch across the injector as my ignitor and I couldn't get the combination to burn. I then realized that my nitrous tank was almost empty and that very little liquid N2O was actually getting out of the injector. Coupled with the fact that there is only supposed to be a 100 psi drop across the injectors, the mixture was off balance. Since I can't dial back the pressure on  the N2O to anything less than about 400 psi, I let the gaseous nitrous flow and reduced the injector pressure to 45 psi to try to reduce the richness caused by the, now gaseous, nitrous flow. All this tinkering cause my crowd to dwindle.

I paired the correct flows with first fuel followed by oxidizer and IGNITION! The 10-15 foot flame roared to life with a thunder. The deep rumbling sound vibrated that whole building and then the masses poured back into the holding bay. There is no question about it. This is a real rocket.

After a couple tests of 91% IPA and 99% methanol (HEET fuel system cleaner), I had to get my nitrous tank refilled ASAP. I called around and it isn't as easy as I thought it was. All of the big companies like BOC and Praxair need either a letter from a race track or league documenting that you are using it for a racing application or they need to send a representative to your company to see that it is legitimate. Even though my company name is Advanced Engine Technologies....? I called around to a couple performance shop where I was finally able to find a company that would fill the tank today. The quote of $6 per pound was like hearing fingernails on a chalkboard. I did some research and found that price to be a little high of the average $5.50 per pound so I went to get it filled. Then the real tests began.

I tested 91% IPA, 99% IPA with some proprietary chemical that makes it turn yellow (Iso-HEET), and 99% methanol. There is no doubt that methanol burns the hottest. Methanol is on an completely different level compared to the more energy dense IPA. The biggest contrast was between the 91% and 99%. The 99% FAR surpassed the 91% in terms of intensity and burn rate. I expected a difference but not that big. The pictures help but the videos say it all.

99% IPA

99% IPA

91% IPA

91% IPA

99% Methanol

99% Methanol

99% Methanol

99% IPA

91% IPA

99% Methanol

99% Methanol Injection Pattern

Day 28: Stared work on the ignitors. Tomorrow will be injector hot tests!

Harbor Freight saved the day with the broken pipe. The EZ out extractor set took it out without an single problem!

Started work on the ignitors. They consist of a short circuit dipped in a nitro cellulose emulsifer of black powered.... which is just a fancy way of saying a ping pong ball melted in an acetone milkshake with black powder sprinkles. I tested a couple and they worked well enough. I think I will still wrap them in cotton and dip them in fuel for the tests.

I got the new solenoid installed as well and everything checked out with the control panel. As soon as I stop my leaky connections I will be able to start some testing!

Day 25: The stand is coming together (sneak peek)

I think my entire stand weighs about 15 pounds and 10 of them have to be from the bolts alone! I just have to get my injector plate drilled up and plumbed up. I got the new power supply in for $11 shipped from ebay. That is what Ill spend the weekend getting that put together. It won't be too long before I get to test out how bulletproof that housing is!

Day 24: Flipped the switch and only silence

Spent a majority of my work time today getting the control panel all put together. I double checked everything and tested the connections. Everything checked out so I threw the switch only to find a gimpy psu fan pulsing at maybe 50 rpms... I took everything that I just put together apart before pulling the psu. I am positive there is a short somewhere in that vast array of resistors and capacitors and after spending about 3 hours searching, I have gave up and moved on to the thrust stand. It reminds me of something Geoff says, "If you can't fix it with a hammer, it's an electrical problem."

Looks pretty bulletproof to me!

Day 23: Just sat around playing with my nuts and bolts

Looking at my pictures, it seems like I didn't get anything finished! Bulletproof glass has proves to be exactly what I expected. Working with it is a nightmare but I am positive that it will be as safe as I thought it would be. It may be slow work but I keep telling myself that I only have to do it once!

Milling down the glass rails for your viewing pleasure. I figure I only get about 8 inches of window so why have 4 of those inches be the aluminum?! 

3/4" of lexan is bulletproof up to a 9 mm point blank round... and I don't doubt that at all after working with this stuff.