HolliStar V2 Rocket Engine Tests Updated

Working at Cape Canaveral is interesting to say the least. SpaceX and Delta launches fly directly over my building a few times a month. I am about 3 miles from the launch pads. Talk about loud....



Finally, got all of the test runs together in one place. After the rapid disassembly of V1, I had over 25+ full 10 second burns using the HolliStar V2 without any major malfunctions other than a melting o-ring. I can't wait until I can get back to building rockets! I am building a website and should have it up soon. I will keep you updated!

The Pause of an Era

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.

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 30: Custom Tanks

We got sick of refillling the tiny tank every two runs so I designed these 1/2 gallons tanks. A little bit of an upgrade from the 1/3 of a liter one we were using! Of course, Geoff laid down a perfect triple weld on the end caps. I only needed 0.083 inch thick walls for 1500 psi so the 0.250 inch thick walls will be more than enough.

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 27: Things are coming together!

After three injector blanks and $30 of micro drill bits, I was finally able to get a plate drilled! The design called for 6 x 0.017" inch impinging fuel jets to be drilled and that was simply not going to happen. I wound up breaking the bit on the second to last hole. Being that I was so close, I drilled it out with a 0.023" bit with the intent of reducing the injector pressure drop.

I ran about 20 flow tests at varying pressures to verify the design...but before that I had to get my daily dose of adrenaline. It turns out that 300 psi max in the lines was no joke. At about 400 this finally gave out on me right into my chest. Like a bomb went off and punched me in the chest, I found myself stumbling around my rocket lab concussed from the BANG!

My ears were ringing for at least an hour. Luckily I had a back up hose and went right back to it getting the tests done... with ear protection on this time.

The stoichiometric flow rate is ~0.02 kg/s for a 5.7:1 O/F ratio. There is no surprise about the increased diameter increasing the flow rate to about double what I designed. Further investigation shows that at an injection pressure drop of 60 psi will give me a 2.5:1 O/F ratio which offers a fuel rich combustion that can reduce combustion temperatures by nearly 1000 K while producing an ISP just over 200 seconds. I'll take it! If worse comes to worst, I can drop to ~30 psi (10% chamber pressure and still push 4:1 O/F ratio.

I got a couple good pictures of the injection pattern. It stays nice and centered. I chose an injection normal for the central oxidizer and 45 degree impingment angle for the fuel.

You can see the diamond shape in the middle of the injector stream. That is from the middle stream getting impacted by the fuel stream from the outside.

Behind the scenes

And of course when I am finally done monkeying around, tragedy strikes when I am trying to be careful. My tank fell off the top of the rocket assembly. This should be an interesting set back.

Did both ends have to break off!? Should be interesting getting that out.

Sneak peek of all the systems! It's starting to look like rocket!

Day 26: 1 extra hour in each day is what I'm asking Santa for this year!

The 80/20 law is in full swing! 20% of the work got me 80% of the way there. Its getting down to the last couple pieces and now comes the hard part.

Drilling the injectors has proven to be more difficult than I anticipated. The oxidizer holes (inner ring) are 0.033 inches where as the fuel holes (outer ring) are 0.015 inches which is the smallest drill bit in the world. It is a #80 drill bit. I broke 2 of them before ordering one made of carbide. That broke too. I am convinced that it is simply not possible for me to drill these holes with the tools I have so I will be changing to a 6 hole pattern which will allow me to use 0.038 and 0.017 inch bits for the oxidizer and fuel, respectively. I am also going to start by drilling one small hole to start that way if I can't get the 17 thousandths bit to work I can go to a 4 injector set up.

The bottom left hole on the outer ring contains the offender!

This is the new injector plate.

Since I couldn't work on my injectors until I got a new plate finished, I started to test my electronic systems. I learned that not all nitrous solenoids are created equal. My fuel solenoid is not powerful enough to open against the 400 psi charge pressure. Should have figured that since car fuel pressure is only ~20-50 psi. So ordered a new one that is on the way now.

I  took the time to just sit down and learn everything there is to know about DC circuits and capacitor banks. Turns out that even though the steady-state requirements of my coolant pump is only 110 watts at 5 amps, the start-up surge can top 50 amps. Even if it is only for a split second, it still shuts my set-up-down. Geoff comes to save the day yet again with lawn mower battery that I can use to run the pump separate from the rest of the system until I can get a capacitor bank put together.

 Testing of the cooling system with the battery. Everything checks out.

 This is the man himself! This is Geoff helping me get my solenoid to seat properly.

 For some reason, our horizontal band saw has been taking FOREVER to cut so while I got the stock for the injector plate cut, I started to shape my next next rocket! This one will be 100 lbf and regeneratively cooled. More on that later!


Quick design notes for my capacitor bank (Warning: Hand-wavy math incoming):

The governing equation is Charge (Coulombs) = Capacitance (Farads) x's Voltage (Volts)

Capacitors in series have additive voltages. A common voltage is a 2.7 volts so I will need 5 of them to get higher than my 12 volt power supply. 2.7 x 5=13.5 volts maximum.

They need to all be able to store the same amount of total charge.

So the equations break down to:

Vt=V1+V2+V3+V4+V5
1/Ct=1/C1+1/C2+1/C3+1/C4+1/C5
Qt=Q1=Q2=Q3=Q4=Q5

It (amperage)=Ct*dV/dt
Stored work potential in the capacitor (joules) is W=1/2*Ct*V^2

So my pump needs 50 amps at 12 volts minimum. My PSU supplies 12.3 volts. Ebay has cheap capacitors that are 80 farads at 2.7 volts. Combining them in series gives me a maximum of 16 farads at 13.5 volts.

dV/dt is going to be limited by the rate at which my power supply can recharge the capacitor.

300 watt power supply can supply 300 joules/second.
If the total joules of energy in my full charged capacitor is W=1/2*~16*12.3^2=1152 Joules
If the total energy in the capactiors can be kept above W=800 Joules (~300 joules less than the full charged one), solving for V=sqrt(2*W/Ct)=sqrt(2*800/16)=~10 volts shows that my psu can supply about 2 volts/second to the capacitor. So my dV/dt is 2 v/s.

The amperage that my ebay capacitor can supply amounts to
It (amperage)=Ct*dV/dt=16*2=32 amps psuedo-continously but it is ok if the voltage drops for a little while until the motor gets spooled up so I think it will work.... "in theory"