Ad Astra per Tartarus

[8BitCosmonaut]

By the way, 8bitCosmonaut, I'm guessing this is something you'll enjoy making fun of.
This Engine is Ethane/N2O Pressure fed.
Also, for everyone else, practically all of the hardware here is simply there to prevent explosions in the event of a failure.

Here's its state after today's work. We finally actually got the main pieces of the test assembly together. A couple pipes need to be fitted now, and then it will be ready to start having fluids flowing through it.
View attachment 33086 View attachment 33087 View attachment 33088

I have SO MANY questions about this. This is by far the most exciting post I've seen in ages. I have my own engine designs and my own college doesn't even allow me to build anything that uses combustible fuels, they have SLS printers, lathes, CNC machines and all the necessities to fabricate a proper one.

-How are the parts for the testbed obtained? Did you get a local manufacturer to bend and machine those parts for you?
-How long did it take for yall to get the math right and design the parts needed?
- Can I get a closer look at the rocket engine itself?
- Is the rocket engine nozzle and chamber lathe turned or printed?

 

[Lt. Snakestrike]

I have SO MANY questions about this. This is by far the most exciting post I've seen in ages. I have my own engine designs and my own college doesn't even allow me to build anything that uses combustible fuels, they have SLS printers, lathes, CNC machines and all the necessities to fabricate a proper one.

-How are the parts for the testbed obtained? Did you get a local manufacturer to bend and machine those parts for you?
-How long did it take for yall to get the math right and design the parts needed?
- Can I get a closer look at the rocket engine itself?
- Is the rocket engine nozzle and chamber lathe turned or printed?

One note is that I'm still mostly new to this project, so a lot of this work is from before I was even involved.

Most of the stuff is machined in-house. There are some things that we couldn't do ourselves, namely the welding for the pressure tanks.
In terms of the maths and such, I know they spent a long time (at least year) just trying to figure out what made sense. The engine is pressure-fed, so the tanks you see run directly into the main valves, which runs directly to the injector (which is machined in-house, and was designed as simple as possible as a result). Also, regarding the fuel choice: Nitrous and Ethane is a god-awful fuel choice in the grand scheme. However, for us it makes perfect sense, mainly because they're non-cryogenic, non-hypergolic/non-toxic liquids that are self-pressurizing (simplifies the pressure-fed system). This is all because we are a student team, so it's about the simplest we can make it all logistically. The worst thing we have to deal with propellant-wise is making sure the Nitrous Decomp doesn't blow something up.

The Combustion Chamber / Nozzle are lathe turned btw. It's a bulky development one though, so it's literally just a cylinder of metal on the outside. Makes it more durable. Frankly, it's probably one of the least worked-on things in the entire project (Right now anyway). We've had to machine 4 different injectors so far this semester, but the combustion chamber was machined at least a year ago (before my time), and has just been sitting around since then.

 

[8BitCosmonaut]

The Combustion Chamber / Nozzle are lathe turned btw. It's a bulky development one though, so it's literally just a cylinder of metal on the outside. Makes it more durable. Frankly, it's probably one of the least worked-on things in the entire project (Right now anyway). We've had to machine 4 different injectors so far this semester, but the combustion chamber was machined at least a year ago (before my time), and has just been sitting around since then.

Nice. Its better to lathe turn the chamber, because SLS printing vaporizes the dust to liquid by a laser before solidifying, essentially making it a die-casted product. That's what I'm most worried about.

Since you've said that they have lathe turned it (which are usually cold worked), I'm assuming that the finished product needs to be heat treated to relief internal stresses? I'm guessing the injector is a kind of face plate to be bolted down to the chamber?

 

[8BitCosmonaut]

Nitrous and Ethane is a god-awful fuel choice in the grand scheme. However, for us it makes perfect sense, mainly because they're non-cryogenic, non-hypergolic/non-toxic liquids that are self-pressurizing (simplifies the pressure-fed system).

If this test is successful, do you guys plan to move on to using liquid fuel? For the oxidizer, you can still stick to using gaseous types no problem. Many hobby rocket engine builders go with alcohol/gasoline with gaseous oxygen configurations and the setup works well.

 

[8BitCosmonaut]

Since you've said that they have lathe turned it (which are usually cold worked), I'm assuming that the finished product needs to be heat treated to relief internal stresses? I'm guessing the injector is a kind of face plate to be bolted down to the chamber?

Ah sorry, my mistake, heat treatment if only for metal spinning like the one shown below, I misidentified it as lathe turning. But you confirmed it as being made by turning, isn't it expensive? The size of that chamber would require a rather large amount of stock material.

Wouldn't metal spinning be superior? It would require far less stock material and is theoretically cold worked so it is stronger on the molecular level.

 

[Lt. Snakestrike]

If this test is successful, do you guys plan to move on to using liquid fuel? For the oxidizer, you can still stick to using gaseous types no problem. Many hobby rocket engine builders go with alcohol/gasoline with gaseous oxygen configurations and the setup works well.

Nitrous and Ethane are gaseous at standard pressure. You need to remember that it's not at standard pressure though in the tanks, so both are actually in liquid state for us. And no, we don't plan on changing to anything else. The benefit of Nitrous for a pressure-fed system is that its slow decomposition into Nitrogen and Oxygen keeps the pressure of the Ox tank while the engine is running. Ethane does something similar, although I'm not entirely sure what the mechanic is behind it. That's what I meant by self-pressurizing.

 

[Lt. Snakestrike]

For the machining, I don't really know as much.

The injector is bolt connected, yes.
Also, we don't have printing as an option anyway.

There's one of the injectors. The outside ring is the bolt holes to go into the combustion chamber. The innermost hole is the Ox inlet, and everything else is fuel (no, it's not designed to be efficient, we know that, it's designed to keep any ox from getting to the engine walls).

Also, regarding the nozzle/chamber. It's not uniformly thick. Right now it's a cylinder of material (aluminium) with just the inside carved out. At the moment it's designed to be durable just by sheer bulk, and once we start transitioning to the vehicle setup (after we hopefully get it firing in the first place) we will figure out how what material we can take off based on heating.

 

[8BitCosmonaut]

Nitrous and Ethane are gaseous at standard pressure. You need to remember that it's not at standard pressure though in the tanks, so both are actually in liquid state for us. And no, we don't plan on changing to anything else. The benefit of Nitrous for a pressure-fed system is that its slow decomposition into Nitrogen and Oxygen keeps the pressure of the Ox tank while the engine is running. Ethane does something similar, although I'm not entirely sure what the mechanic is behind it. That's what I meant by self-pressurizing.

I understand the operations of a gaseous propellant rocket engine, I was just curious if your team would plan to move on to more potent propellant configurations if this test is successful.

But I didn't know that nitrous oxide can decompose, so that is interesting.

 

[8BitCosmonaut]

I understand the operations of a gaseous propellant rocket engine

You need to remember that it's not at standard pressure though in the tanks, so both are actually in liquid state for us.

Sorry, I misread your comment again. So it's theoretically a liquid fueled rocket engine, nice. Now this is a cycle new to me, keeping gaseous propellant under pressure throughout the system so they inject into the chamber at liquid state? Very interesting.

 

[8BitCosmonaut]

For the machining, I don't really know as much.

The injector is bolt connected, yes.
Also, we don't have printing as an option anyway.

View attachment 33401
There's one of the injectors. The outside ring is the bolt holes to go into the combustion chamber. The innermost hole is the Ox inlet, and everything else is fuel (no, it's not designed to be efficient, we know that, it's designed to keep any ox from getting to the engine walls).

Also, regarding the nozzle/chamber. It's not uniformly thick. Right now it's a cylinder of material (aluminium) with just the inside carved out. At the moment it's designed to be durable just by sheer bulk, and once we start transitioning to the vehicle setup (after we hopefully get it firing in the first place) we will figure out how what material we can take off based on heating.

Ooo, I wish I was in your team right now. I have so many ideas.

Looking at the chamber above the injector, those inner circle of holes I presume are coolant holes?

 

[Lt. Snakestrike]

Ooo, I wish I was in your team right now. I have so many ideas.

Looking at the chamber above the injector, those inner circle of holes I presume are coolant holes?

I have no Idea honestly.

 

[Lt. Snakestrike]

Just blurred out some names.

 

[Lt. Snakestrike]

Also, this poster is several years old, so a lot of things may be inaccurate.

 

[Roger Jolly]

View attachment 34215
Just blurred out some names.

“blurred” lol

 

[Lt. Snakestrike]

Oh whatever

 

[Lt. Snakestrike]

Soo... What's the policy on necroposting on my own thread???

 

[Lt. Snakestrike]

An update: We still haven't Hot-fired the Rocket. Our main hold-ups are ignition and finding a suitable test location, but also it's a student project, so things take time. I'm the Vehicle Lead now, and most of my work is redesigning the P&ID so it can be used with a rocket that can actually detach from its support systems. Anyways, we're high pressure testing this weekend, and I'm excited, to say the least. Will share pictures soon.

 

[Lt. Snakestrike]

8bitCosmonaut If you're still around, I know and can answer a lot more now if you're interested.

 

[Pink]

The high pressure test sounds like it will be good progress!
Will it use the actual propellant or inert substitutes?

8bitCosmonaut If you're still around, I know and can answer a lot more now if you're interested.

He sometimes comes on, but you can reach him faster on a discord server I'm in, if you're interested.

 

[Lt. Snakestrike]

The high pressure test sounds like it will be good progress!
Will it use the actual propellant or inert substitutes?

We're using Nitrogen as a Simulated Prop until the actual test where we'll fire.