Space Collection Part 3: Everyday Astronaut figures out the RL-10 Rocket EngineJan 02, 2022
Greetings earthlings. If you follow the channel, you'll know that we recently visited Steve Jurvetson's amazing
collection. We got our heads spinning with so many amazing gadgets, Apollo main sofas, MOCR console, fuel cells, Soyuz panel etc. which we covered in the previous episode. But the
collectionalso has a good number of
engines. From the really small to the really big. Unfortunately, I know relatively little about
engines, which is probably a good thing, or I'd be tempted to get them going again. But while we were there, this guy came through the door. The
spaceenthusiasts among you will have recognized Tim Dodd from the popular and oh-so-amazing Everyday Astronaut channel.
Tim explains everything about space with clarity and depth. He had hardly walked through the door that he was drawn to this giant thing. A complete RL-10 engine. This incredible engine, first flown in 1963 on the Atlas rocket, is still in use today and will fly on the SLS in the near future. To my uneducated eye, when I see a rocket engine, I see a large bell nozzle and lots of randomly interconnected tubes. Actually, I see a goat. Because, you see, the piping for a rocket engine was clearly inspired by the interconnections of the digestive system of herbivores.
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space collection part 3 everyday astronaut figures out the rl 10 rocket engine...
Look, it's obviously similar. Engine. Goat. Engine. Goat. Same concept, one powered by weed and the other by oxygen and hydrogen, which produces much bigger farts. And of course Tim wanted to discover the digestive system of this engine. So both are hydrogen. And these are the gimbal mounts? Yes, definitely. So say again, how does this flow? Oh yeah, so what have we discovered? Okay, since, and I'm not by any means, I'm just... You're now the resident expert now, take up the mantle! No, no, all we have to do is get Scott Manley here, he'll get us in shape.
And as Tim rightly points out, Scott Manley has a whole episode on expansion cycle engines including the famous RL10, which we should have seen beforehand. But we didn't. However, you probably should. So let's say you haven't seen Scott Manley's video. How much can you find out just by looking at a rocket engine? Until now, you'd obviously figured out the hood cooling tubes and the visible injector plate in the combustion chamber, right in the middle here. So we know that hydrogen goes through these pipes. We know that hydrogen is, yes, definitely, because this is the hydrogen bomb here.
So we go here. So yeah, at some point. First of all, I have to find out how he got here in the first place. This is what you confuse with it being an expander. So is the hydrogen cooling the hood? Ah yes, key point. Liquid hydrogen: get all this: when this is at full power, it's hotter than the sun right here, and simultaneously icicles are forming on the edge, at the same time. So the hydrogen goes through the bell first? Yes, where? I think this is the hydrogen inlet tube, this is an oxygen inlet tube. Okay.
And then it's led through there, through... Well, because either it goes - oh god... Yeah, it goes, it goes here. Yes of course. Yes, so it goes here, it goes there... Oh, that's why there are two! Why? One is an outlet, the other is an inlet, because after it flows through the chamber, it has to go through the pump back to the pump. So wait, maybe I was wrong about this. Is this a separate circuit that generates additional lines? Is not the same. So it will only drive these tubes. Half, you know, split two to one.
So the hydrogen set goes in here and the other set goes in here? No. So this goes into the hood, comes out and goes to the second turbo pump and then combusts again. So, I don't know if he has to come back. He never goes back... He goes back to the camera. It combusts. At the end of his journey, he is burned. Yes. We know where it ends! Yeah, so what I'm trying to figure out is... where's the oxygen? iOxygen is here. Simple: in and up. Okay. And that is? So just one pass through the pump?
Yes, little man. So is there much more to hydrogen because of the circuitous route? Mainly because it's so thin, it's so sparse that it requires a lot more, multiple stages, and a much bigger pump. Lesser in the gas phase? Yes, both. Ok, liquid too? Yes. So, they burn at a ratio of six to one, liquid hydrogen to liquid oxygen. One is hydrogen and six is oxygen, which is the opposite for most fuels and such as metalox and RP1. But then, I'm still trying, I'm still trying to figure out, however, one of these is what you have to drive.
And normally, it should work out fine. You think it gets hot, the biggest tube would be the one coming out of the hood, it got hot and now it's more gas. And the thinnest perhaps food? That very well could be the answer. This one goes here, one goes in the hood, goes up, picks up here, makes some gasoline. It is also bigger, it is enlarged. I wonder if the side that is larger is closer to the gas phase? And then this is the end where it comes in. And look at the thickness of the pipe, rather the diameter. repeat it?
Which one goes in, which one goes out? Both pipes are approximately the same size. It could be, actually, this could be
partof the accelerator, believe it or not. Like a fixed throttle bore so you know it will never exceed a certain pressure. Or it could be a deeper bell mouthpiece actually. Now that I think about it, it's more likely... Wait, this could be, this could be the actual
partof the expander! Where it's taking the hot gas from here, accelerating to supersonic, going high pressure through a de Laval nozzle, turning this bomb. That pump drives both liquid oxygen and - this makes sense! - and the input goes in here.
Okay, so that's all your beauty right there! Yes, here is your first stage. Is that tagged somewhere? I have to know now, I have to know! Okay, so what is this? Say once more, what is the effect of this? So this is basically, it's a mini rocket nozzle. This is going to be the same as the throat of the engine, where there is going to be high pressure here, they choke the flow, which will take it to supersonic speeds. And then they expand the flow again, just like any thruster you see around here. So it's a de Laval mouthpiece.
So what you're doing here is trading high pressure for more speed. So they do this to increase speed, so they can spin the bombs, right before the bombs spin. I think, now again, I'm really an amateur, but that seems plausible. Here's a diagram of the RL-10 engine that I looked up the last time I was here. Hopefully that will help. Okay. so it comes from the hood, it gets hot, it gets hot. It's collected up to here. So all these little tubes go all the way up. In fact, you can see it almost here, this is a version.
Right here, you know, you can see how this manifold interacts with these individual tubes. This is feeding. Yes. And then they go up. Yes. Oh, therefore the two to one. So you're coming in here. So the hydrogen comes to the middle of the bell, through the middle of these little tubes, and goes down. At the end of the hood, the tubes make a U-turn and back up, to the top of the hood, then further up to the top of the firebox to keep the outside of the chamber cool. , as can be seen here. Yeah, we're definitely right that the lower tube is...
The ring that this fat tube is attached to collects the hydrogen from the tubes. Now it is heated and transformed into a gas at very high pressure. This is what will drive the turbo pump. ...is the - after it's run through everything. So this is what rotates. We are now looking at the inlet (to the right) and the outlet (down and to the left) of the turbine that is at the bottom of the turbopump and that spins everything. The absolute final journey goes this way. Yeah. The very bottom of this big fat guy is what's going to go: there's going to be a vent at the end of this and that's going to...
Is there a vent somewhere? Yes, this guy. Adjustment of the mixing ratio. So it goes into combustion - the top ring is in the combustion chamber, right? Yeah. So the top of the combustion chamber is right here and that will be your injector. Which makes sense, just physically, with these tubes: the inside would be... Hmm, okay, so we're definitely right, this is the bottom line here. So all the hydrogen goes through the bell? Um, that's a good question. Because it seems like maybe it's just a part. This is still very dense compared to... But does it split into one that goes through the bell and one that goes straight through?
No. All of the hydrogen passes through the pump, enters the bell, expands to drive the pump's turbine, and then enters the combustion chamber. Oh, so this is stage one, stage two. Yes, and exactly, then you will start organizing from there. But then the exit would be here? It is also driving oxygen. Oh sorry, so the exit is down there. It's mechanical. Are there like gears between these? Which makes a lot of sense. And your oxidizer and fuel just follow those lines. So this is a right hand gearbox. You are driving the oxidizer. The oxidizer is hilariously simple.
The oxidizer goes in and then the tube goes to the purge check valve, which we should see. Purge check valve, it doesn't say purge check valve, it says mixture ratio adjustment. This is a discharge, cooling and pressure relief valve. That's on the hydrogen line. The mixture adjustment is a throttle valve, so you can adjust the oxygen. Yes, that would make a lot of sense. So one thing about the gearbox is you have to make sure that the seal, because you have the same gearbox for both oxygen and hydrogen, you have to make sure that your seals are really good, or the mixture of oxygen and hydrogen.
Oh yes, that would be bad. So sometimes they will have like two separate turbo pumps so you don't have to worry about seals. And voila, with the help of the Everyday Astronaut, a group of retroelectronics can crack the plumbing for an RL-10 rocket engine. A little sorta. We might as well have watched the old Pratt and Whitney video from the 1960s and gotten the explanation, which will now easily follow. The engine itself is as simple as the diagram. To demonstrate, hydrogen enters at this point, flows through the first stage pump, into the second stage pump, passes through the cooling jacket manifold, down through the middle of the tubes, to the turn collector, it goes up the long tubes and is collected in the exit collector. , through the venturi in the turbine.
There it provides the energy to drive the hydrogen and oxygen bombs. Then around the large line through the main fuel shutoff valve to the injector and then into the combustion chamber. On the oxygen side, oxygen flows through the inlet valve via a single stage pump, directly through the ratio control valve, to the injector. Now for real, go watch the Scott Manley video. See you in the next episode! Arriving at one of the vertical test stands, the RL-10 is set up and prepared for the fire test. Three, two, one, zero... At the end of this firing test, the engine will be returned to the manufacturing area for complete disassembly, inspection, and assembly.
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