Being that I intend to be use this thrust stand to completely profile my rocket motors, I have been spending a lot of effort building the microcontrollers, software and data acquisition modules. In a sense, I feel like I am playing catch up for all of the work I didn't do on my first motor.
Since there are no moving parts in a pressure-fed liquid rocket motor, there are only a few places you can collect valuable data and even then you must interpolate it into something meaningful. One module in particular affords a lot of insight into the performance characteristics of the motors and that is the mass flow rates for the fuel and oxidizer.
Mounting rail for the load cell
I fashioned a bracket out of a 1 ft length of 2 inch wide 1/8 steel flat bar. I welded it to a 1.5" c-channel that is welded to the top of the frame.
Back of the mounting bracket
I wanted the load cell hanging from the mounting bracket and bolted to the top of the skate so I welded a pad onto the top of the bracket.
Next the skate is made of a 1ft piece of 4 inch 1/8" steel flatbar with 2 1/2" square tubes holding a piece of 1/4" steel flat bar that is threaded for the m4 bolts that fit my v-groove bearings.
Skate the the tank is mounted to
Once assembled the grooves in the skate bearings slide over the 2" flat bar mount to provide a sturdy linear bearing.
Linear bearing
Load cell mounts
The load cell is mounted between the two tabs seen in the picture above.
Load cell mounted
Closer picture of the load cell
I zip tied the tank on until I figure out a better way to hold the 2ft long tank against the skate.
Holding the tank that I made back in Ohio.
Now that I see the concept works, I am making another taller one that will have a universal mount to allow me to hold a variety including CO2, N2O and flight ready tanks.
Been building one day and one dollar at a time. Infrastructure is my new game. Couple grand in but still much to be done. Lathe and mill bought. Cylinders for brazing aluminum acquired. Materials ate in. Designs have been designed. My new rocket is going to be a 250lbf flyable model. It's a bit of a living mess for the time being but more to come.
It has been a while since I have been able to get back into building rockets. After my career move down here to Cape Cavaneral, I have been rebuilding my infrastructure. Currently, my spare bed room in my apartment is has been converted to a rocket research lab and I have been aggregating all the tools that I need to continue development.
To date I have been able to equip myself with:
Grizzly 7x14 Lathe that I am upgrading with an arduino based power feed that will read the RPMs and move the tool at prescribed rates to give the best finishes and certain threads per inch.
90A flux core MIG Welder that I converted to DCEN with a 100 amp bridge recitifier, 94,000mF capacitor bank (40 individual capacitors), and a 40 turn torodial core inductor. The stock AC welder would barely even weld 1/8 in steel and even then it was very sporadic and popped slag//bb's all over the place. Since the conversion, the welder just sounds mean! A constant sizzling bacon sound with up to 1/4 in 4 thousands gap penetration with the settings only turned up ~3/4 of the maximum. I got the welder on sale for $80 then put $30 worth of electronic into the upgrade and its performance now is EASILY comparable to some of the $500-600 machines I have welded with in the past.
2 x 1000 psi regulators. One of which is oxidizer hardened.
I have also designed and started to build my thrust stand that will be able to host a variety of sensors, high speed loggers, and data acquisition instruments. I have been learning machine code and the fundamentals of optimization to develop my data loggers. So far I can get a sample rates nearing 5-7 microseconds which should be plenty of resolution for future testing.
My latests efforts have been focused solely on the building of my 3 axis CNC router. It will serve as the backbone for roughing out blanks and cutting out my injector plate stacks. Eventually I will upgrade it to a 4th dimension on the router head and install a 4th axis spindle.
It will be primarily steel construction. Bed size is 32 x 21 inches made of 2in square tubing with 1/8 thick walls and the red gussets are 1/4 in steel plate. Currently, I have the base frame and gussets made. I also have all of the linear rails, bearings, 1-1/2 hp router, stepper motors, stepper motor drivers, all 1/2"-10 acme lead screws. Its just a matter of time before I can finally get this put together.
Welding Machine and welding table
Lathe Lab Setup
Thrust Stand Front Frame (19x19 inches)
CNC base frame and completed parts
Assorted Rocket Stuffs
Sorry for the explosion of pictures but I should be able to keep a more regular update schedule now that I am getting into the swing of things.
The month of June has been a very eventful one. Most significant is my career shift. I got a new job in Cape Canaveral working on rockets...imagine that! I packed up and moved down so now I am located in the rocket capital of the world! Sadly, this takes me away from the machine shop where I spent the past few months slaving over the tools building rockets. For the time being I will have to put my rocket engine building on hold until I can find a new home to get back to work. It does give me time to start developing a flight ready design with the knowledge I have gained.
The
final tests before I had to see my baby go. These were the best/loudest
tests yet so at least I left off with a wooooooosssshhhhhh and not a
bang!
Fortunately, my rocket has a good home where it will serve as a demo model for Advanced Engine Technologies back in Dayton. I did manage to get a regenerative chamber designed and hastily machined so the next big step in that build will be to get an injector plate drilled up. So if there is anyone in the state of Florida that has access to machine tools please let me know and we can make
some sparks fly! I have a youtube playlist with all of my engine tests that can hopefully help inspire other to keep up the good fight! Please continue to share and offer me some feedback so that the next one will be even better!
This is the 100 lbf regeneratively cooled chamber! Coming eventually! I'll have more pictures as soon as I get unpacked.
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
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!
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!
