So that makes it seem like the diagram you have, which is for the Merlin 2, is just a different control system than for the Merlin 1.
which increases the pump pressure, which increases the fuel and oxidizer flow to both the main chamber and the GG, and that increases the GG gas volume which is positive feedback.....And there is one other thing. CRS-6 came down hard because of a "stiction in the biprop throttle valve, resulting in control system phase lag" (Elon Musk). This suggests they are throttling both LOX and fuel to something, I suppose the gas generator.
Okay, so both the RP-1 and LOX are modulated by throttle valves on the way into the gas generator. That means that during the landing burn it would be possible to run the gas generator richer than during the ascent burn, so as to increase the amount of turbopump exhaust volume injected into the engine bell for a given amount of turbopump power. Well, unless something is going to break from running at lower temperature (like maybe gas generator ignition?)
Two identical turbines. Both have the same mass flow entering them. One gas stream is hotter than the other. Output ambient pressure is equal.
The hotter turbine will produce more output power on the shaft, right?
Two identical turbines. Both have the same mass flow entering them. One gas stream is hotter than the other. Output ambient pressure is equal.The hotter turbine will produce more output power on the shaft, right?
As you say, PV=nRT. Turbine A's incoming stream has larger volume. Output stream will have larger volume. Shaft output power will be larger, because the shaft will be turning faster.
Two identical turbines. Both have the same mass flow entering them. Exit pressure is the same. Let's say the torque load on the shaft is the same. Turbine A has hotter gas. That's enough to determine the rest of the conditions.As you say, PV=nRT. Turbine A's incoming stream has larger volume. Output stream will have larger volume. Shaft output power will be larger, because the shaft will be turning faster.Right?
1. And that means I could reduce the mass flow for the hotter one to make the shaft power the same. And then I'd have two turbines with the same shaft power emitting different mass flows of gas. One emits less mass at higher temperature and lower volume. 2. This demonstrates that, by actuating the turbopump's LOX and RP-1 valves separately, we can vary the GG output mass rate for a fixed turbopump shaft power. We don't have full freedom, because the GG can't get too hot, but we can go some amount in the other direction and run the GG with more mass flow and lower temperature.
The F-1 engine pictures show that it's possible to get the GG exhaust well past the exit of the bell before it mixes with the main flow. .
The GG exhaust in the bell is subsonic, so it will decelerate and increase in pressure as it expands towards the exit of the bell.
So then once I can vary the mass flow from the GG into the main engine bell, my question was around how much control I can actually get from this.
.........And, supersonic gases accelerate when the flow cross section expands. Subsonic gases decelerate. That's why rocket nozzles coverge and then diverge. Now you could tell me that the GG exhaust is injected into the bell supersonically, and I'd be surprised, but I suppose it's possible. Short of that, though... I'm starting to think we're not actually having the conversation I was hoping to have.That's too bad. Oh well.
The shear between the subsonic GG exhaust (<500 m/s) and the main flow in the F-1 (>2600 m/s)
Mixing will be greater on the side with more shear.
Uh... are you just pulling my leg?
Now you could tell me that the GG exhaust is injected into the bell supersonically,
I'm starting to think we're not actually having the conversation I was hoping to have.
i just do not want to make another topic so this seems close enough.what if reuse just most valuable part of the 2 stage - engine? it has compact size so no need to big heat shield. it has integrated heat tolerant tail stabilizer so no need to worry about center of mass problems. it is light weighted (400 kg?) so no need for big shute an the end. and even small helicopter could catch it in the air.