Liquid Bipropellant Rocket Engine Project

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saustin

saustin

L2, NAR #86266
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Hi TRF,

I'm a university student studying aerospace engineering. While we deal mostly with solids on this forum, I thought I'd share a project from the world of liquids.

Over the past year, I designed, built, and successfully hot-fired a liquid propellant rocket engine. The engine burns kerosene/liquid oxygen and was designed to produce 500 pounds of thrust at a chamber pressure of 600 psi.

I fired the engine at the Friends of Amateur Rocketry (FAR) site out in California in August. Ignition was achieved on the first attempt, and the engine burned successfully for 2.55 seconds. Among the many people who made this project possible are Rick Mascheck of FAR and Dave Crisalli of the Reaction Research Society.

Video of the test is here:

Best,
Sam

Te4mTku.jpg


ZPxNBEM.jpg


tW6PycH.jpg
 
Thanks!

CoyoteNumber2 said:
Super cool. Do you have plans for a flight vehicle?
Click to expand...

Not at the moment. Over the course of this project I got feedback and identified several ways I could improve the design, mainly regarding material choices in the chamber and nozzle to survive a longer burn. I'm redesigning the engine now for a little more thrust and, pending a static fire, will then look at building a rocket around it.
 
How much does it weigh, with a full load of propellant?
What's the average thrust?
 
The engine itself weighs 15 pounds, and the rest of the test stand (steel mounting plate plus tanks and plumbing) weighs about 100 pounds by my approximation. LOX and kerosene load was about 15 pounds each (30 total).

I unfortunately didn't get any data from the test because the SD card wasn't inserted in the DAQ, but the design thrust was 500 lbf. I'm starting on a new 1500 lbf design that weighs the same as the last engine.
 
saustin said:
Hi TRF,
I'm a university student studying aerospace engineering. While we deal mostly with solids on this forum, I thought I'd share a project from the world of liquids.
Over the past year, I designed, built, and successfully hot-fired a liquid propellant rocket engine. The engine burns kerosene/liquid oxygen and was designed to produce 500 pounds of thrust at a chamber pressure of 600 psi.
I fired the engine at the Friends of Amateur Rocketry (FAR) site out in California in August. Ignition was achieved on the first attempt, and the engine burned successfully for 2.55 seconds. Among the many people who made this project possible are Rick Mascheck of FAR and Dave Crisalli of the Reaction Research Society.
Video of the test is here:

Best,
Sam
Click to expand...


Very impressive. Much success with your future work!

Bob Clark
 
saustin said:
The engine itself weighs 15 pounds, and the rest of the test stand (steel mounting plate plus tanks and plumbing) weighs about 100 pounds by my approximation. LOX and kerosene load was about 15 pounds each (30 total).

I unfortunately didn't get any data from the test because the SD card wasn't inserted in the DAQ, but the design thrust was 500 lbf. I'm starting on a new 1500 lbf design that weighs the same as the last engine.
Click to expand...

I would recommend rerunning the test, this time with the SD card (I would also make sure to have a checklist that includes inserting the SD card), before doing any redesign. You already have everything so it should just be a matter of fuel, oxidizer, and time. What you learn from the data collection might be helpful for the redesign.
 
Hi all, just wanted to provide an update with my progress on the liquid engine project. Following the static test of the first engine back in August (posted above), I decided to design another engine with an increased thrust level of 1500 lbf. I increased the amount of phenolic ablative material used in the chamber and nozzle in order to increase the engine life after observing visible thermal failure in the nozzle and injector during the last test. I also switched to aluminum for the chamber casing, injector, and nozzle carrier. In light of those design changes, the new engine tripled the thrust to weight ratio of the old engine as it was approximately the same weight as the original design.

I tested this engine at the Friends of Amateur Rocketry site in California on January 19. The engine started on the first attempt and burned for 3.1 seconds before depleting the oxidizer tank. Thrust and pressure data was recorded and compiled after the test. All the engine hardware is in good condition and ready for a second test after some refurbishment.

Hercules 2 Hot-Fire 1.19.19 Summary:
Propellants: Kerosene/LOX
Max Pc: 614 psi
Max thrust: 1276 lbf
Avg thrust: 1137 lbf
Burn time: 3.1 s
Total impulse: 3,570 lbf-s
Designation: N-5100

Original vs new engine: https://imgur.com/a/Fw7f4ux
Cold flow calibration and visual impingement inspection: https://imgur.com/a/DWWuzxs
Hot fire: https://imgur.com/a/LuzaSlY
Data: https://imgur.com/a/QyFuQcqhttps://imgur.com/a/QyFuQcq
Video here:

I'm thankful for the many people who made this project possible by offering advice and assistance along the way.
 
saustin said:
Hi all, just wanted to provide an update with my progress on the liquid engine project. Following the static test of the first engine back in August (posted above), I decided to design another engine with an increased thrust level of 1500 lbf. I increased the amount of phenolic ablative material used in the chamber and nozzle in order to increase the engine life after observing visible thermal failure in the nozzle and injector during the last test. I also switched to aluminum for the chamber casing, injector, and nozzle carrier. In light of those design changes, the new engine tripled the thrust to weight ratio of the old engine as it was approximately the same weight as the original design.

I tested this engine at the Friends of Amateur Rocketry site in California on January 19. The engine started on the first attempt and burned for 3.1 seconds before depleting the oxidizer tank. Thrust and pressure data was recorded and compiled after the test. All the engine hardware is in good condition and ready for a second test after some refurbishment.

Hercules 2 Hot-Fire 1.19.19 Summary:
Propellants: Kerosene/LOX
Max Pc: 614 psi
Max thrust: 1276 lbf
Avg thrust: 1137 lbf
Burn time: 3.1 s
Total impulse: 3,570 lbf-s
Designation: N-5100

Original vs new engine: https://imgur.com/a/Fw7f4ux
Cold flow calibration and visual impingement inspection: https://imgur.com/a/DWWuzxs
Hot fire: https://imgur.com/a/LuzaSlY
Data: https://imgur.com/a/QyFuQcqhttps://imgur.com/a/QyFuQcq
Video here:

I'm thankful for the many people who made this project possible by offering advice and assistance along the way.
Click to expand...

Omg so many questions... Do you have a project website with more details? Did you machine the injector yourself? Are there more pics of the injector showing how fuel and oxydizer are mixed and routed? When does it fly?
 
What is your expected nozzle life given as it seems to be one of the limiting factors?

Awesome project by the way. Great job!
 
Chad, I'm working on compiling media from the build and test and will post it when it's finished. The injector has 30 pairs of unlike impinging doublet elements with LOX injected in the center and kerosene on the outside.

The graphite nozzle insert actually survived and showed no signs of visible damage. I think the limiting factor for engine life is heat transfer into the injector, which is made of aluminum with a phenolic insulation disk epoxied to the face.
 
Very impressive and reliability looks good! A very nice accomplishment. It would be interesting to know your specific impulse. The propellants must be pressure-fed. How is that done?
 
saustin said:
Hi all, just wanted to provide an update with my progress on the liquid engine project. Following the static test of the first engine back in August (posted above), I decided to design another engine with an increased thrust level of 1500 lbf. I increased the amount of phenolic ablative material used in the chamber and nozzle in order to increase the engine life after observing visible thermal failure in the nozzle and injector during the last test. I also switched to aluminum for the chamber casing, injector, and nozzle carrier. In light of those design changes, the new engine tripled the thrust to weight ratio of the old engine as it was approximately the same weight as the original design.

I tested this engine at the Friends of Amateur Rocketry site in California on January 19. The engine started on the first attempt and burned for 3.1 seconds before depleting the oxidizer tank. Thrust and pressure data was recorded and compiled after the test. All the engine hardware is in good condition and ready for a second test after some refurbishment.

Hercules 2 Hot-Fire 1.19.19 Summary:
Propellants: Kerosene/LOX
Max Pc: 614 psi
Max thrust: 1276 lbf
Avg thrust: 1137 lbf
Burn time: 3.1 s
Total impulse: 3,570 lbf-s
Designation: N-5100

Original vs new engine: https://imgur.com/a/Fw7f4ux
Cold flow calibration and visual impingement inspection: https://imgur.com/a/DWWuzxs
Hot fire: https://imgur.com/a/LuzaSlY
Data: https://imgur.com/a/QyFuQcqhttps://imgur.com/a/QyFuQcq
Video here:

I'm thankful for the many people who made this project possible by offering advice and assistance along the way.
Click to expand...


Have you read the book,

HOW to DESIGN, BUILD and TEST SMALL LIQUID-FUEL ROCKET ENGINES
ROCKETLAB / CHINA LAKE, CALIF
https://risacher.org/rocket/

It suggests using a liquid-cooling jacket to get longer burns and longer engine engine life.

Bob Clark
 
saustin said:
Chad, I'm working on compiling media from the build and test and will post it when it's finished. The injector has 30 pairs of unlike impinging doublet elements with LOX injected in the center and kerosene on the outside.

The graphite nozzle insert actually survived and showed no signs of visible damage. I think the limiting factor for engine life is heat transfer into the injector, which is made of aluminum with a phenolic insulation disk epoxied to the face.
Click to expand...
any updates?
 
aerostadt said:
Very impressive and reliability looks good! A very nice accomplishment. It would be interesting to know your specific impulse. The propellants must be pressure-fed. How is that done?
Click to expand...

Looking at his test stand, He has a bottle of (most likely helium, but nitrogen can be done as well) strapped to the I-Beam. This goes through a regulator to step down the pressure, and then it pressurizes both his propellant tanks through check valves on the top. The pressure drives the propellant through the engine.

He has a second regulator on there to drive his actuator for his main propellant valves, which are actuated by a common actuator.

There is a lot of consideration put into selecting parts, and the configuration but that is the basics.


Great work on the engine saustin! It looks like a fantastic burn!
 
Last edited:
Xrain said:
Looking at his test stand, He has a bottle of (most likely helium, but nitrogen can be done as well) strapped to the I-Beam. This goes through a regulator to step down the pressure, and then it pressurizes both his propellant tanks through check valves on the top. The pressure drives the propellant through the engine.

He has a second regulator on there to drive his actuator for his main propellant valves, which are actuated by a common actuator.

There is a lot of consideration put into selecting parts, and the configuration but that is the basics.


Great work on the engine saustin! It looks like a fantastic burn!
Click to expand...
The Electron rocket uses brushless motors and lipos to drive fuel pumps instead of the usual turbopumps. I wonder if any amateurs have tried this route? I use to be into racing drones and the discharge rates and voltages from competition batteries are incredible.
 
Details of design and operation probably should be limited to the research subforum, so I'll only ask a rather general question.
saustin said:
LOX and kerosene load was about 15 pounds each (30 total).
Click to expand...
15 pounds each seems really odd. The stoichiometry of kero + O2 → CO2 + H2O indicates roughly 3.5 lb of LOX per lb of kero. I know there are reasons to go not exactly stoichiometric, but this is very surprising.
 
Show me a small available fuel pump that can provide good flow rate for that application and I might be interested.
 
Pretty cool - no exactly an every rocket motor. Kids, don't try this at home!
 
They might have simply made sure to have enough kerosene so that it would not run out. If the fuel runs out on a liquid propellant engine, I'd expect the engine to destroy itself. Running rich is also a way to drop temperature and to keep the combustion environment reducing rather than oxidizing. It can also be hedging the bet on getting the flow rates balanced right.
 
Chad said:
The Electron rocket uses brushless motors and lipos to drive fuel pumps instead of the usual turbopumps. I wonder if any amateurs have tried this route? I use to be into racing drones and the discharge rates and voltages from competition batteries are incredible.
Click to expand...

I don't want to get too off topic here, but I've been working on doing electric pumps for my own liquids. I haven't fired an engine with it yet, and to my knowledge no other amateurs have fired an electropump. But there are a lot of nice advantages to it, the brushless motors around these days are definitely fantastic.

jqavins said:
Details of design and operation probably should be limited to the research subforum, so I'll only ask a rather general question.
15 pounds each seems really odd. The stoichiometry of kero + O2 → CO2 + H2O indicates roughly 3.5 lb of LOX per lb of kero. I know there are reasons to go not exactly stoichiometric, but this is very surprising.
Click to expand...

G_T said:
They might have simply made sure to have enough kerosene so that it would not run out. If the fuel runs out on a liquid propellant engine, I'd expect the engine to destroy itself. Running rich is also a way to drop temperature and to keep the combustion environment reducing rather than oxidizing. It can also be hedging the bet on getting the flow rates balanced right.
Click to expand...

So I could go into more detail in a different thread in the research forum if that was desired. My feeling is, most of the reason he has the same size tanks would be that double ended pressure vessels cost a lot of money and can be a bit hard to find. So he probably just bought two of the same kind rather than trying to source two different sizes just for a test stand. Flight articles you typically would go through the trouble of getting the right sized tanks.

You also never really want run a liquid engine close to stoichiometric, with nearly always being rich on the fuel. As it has a lot more performance overall running it a bit rich, as well as substantial weight savings carrying less oxidizer. Oxidizer doesn't add nearly as much energy to your rocket (normally) compared to more fuel. Also makes your engines melt less often from the lower heat flux from the lower combustion temps.

You do also typically end a burn with the oxidizer being shut off first. Blowing raw oxidizer on a hot engine tends to cause it to enter into engine rich combustion.
 
jqavins said:
Details of design and operation probably should be limited to the research subforum, so I'll only ask a rather general question.
15 pounds each seems really odd. The stoichiometry of kero + O2 → CO2 + H2O indicates roughly 3.5 lb of LOX per lb of kero. I know there are reasons to go not exactly stoichiometric, but this is very surprising.
Click to expand...

Xrain said:
So I could go into more detail in a different thread in the research forum if that was desired...
Click to expand...
Probably not necessary. I only wanted to note something odd. If it would turn you on to expound further then I will gladly read it.
My feeling is, most of the reason he has the same size tanks would be that double ended pressure vessels cost a lot of money and can be a bit hard to find. So he probably just bought two of the same kind rather than trying to source two different sizes just for a test stand...
Click to expand...
Well, not exactly that, as LOX is about 40% denser than kero, so equal volumes would give greater LOX mass, where he said he had equal masses.
You also never really want run a liquid engine close to stoichiometric, with nearly always being rich on the fuel...
Click to expand...
As I'm aware. But 1:1 is not "a little rich"; it's a whole heck of a lot rich, if he's burning even nearly all that fuel.
You do also typically end a burn with the oxidizer being shut off first. Blowing raw oxidizer on a hot engine tends to cause it to enter into engine rich combustion.
Click to expand...
Leading to unplanned rapid disassembly.

I say again, I'm just noting something odd; I'd gladly read more about it, but don't need to.
 

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