4 ms·

I'm confused; wouldn't the oxidizer-rich half run hotter? Isn't that challenge the Russians overcame but the US punted on back in the days of the space shuttle

I'm confused; wouldn't the oxidizer-rich half run hotter? Isn't that challenge the Russians overcame but the US punted on back in the days of the space shuttle? Your post and the referenced wikipedia article claims the turbines run cooler. Wouldn't that only be true for the fuel-rich side?

avmich 8y ago
> wouldn't the oxidizer-rich half run hotter? You try running it as hot as possible, but without burning metal. You have about twice as much liquid oxygen by volume than kerosene in a typical engine, but you can heat kerosene to higher temperatures without burning. So... I don't think you'll get higher temperatures with oxygen gas generator?
- newnewpdro 8y ago
  The hackaday article explicitly states the oxygen-rich preburner exhaust was extremely hot and required metallurgical advances before turbines could survive it. How is the Raptor's oxygen-rich side any different from what the Russian's were dealing with? The article left me with the impression that the Raptor is using similarly resilient materials for the oxygen-rich side, with its language describing the US and Russian designs solving the two critical halves of the problem. There just seems to be a contradiction in the statements surrounding the turbines running cooler.
  - avmich 8y ago
    > The hackaday article explicitly states the oxygen-rich preburner exhaust was extremely hot I didn't find this exact quote, but the idea is the following: oxygen-rich flow can get hot enough to ignite metal. What Russians did was to find the materials withstanding ignition best and find temperatures which are still safely avoiding ignition. This combination turned out good enough to use oxygen-rich gas generators. Raptor may be using similar approach. "Two sides of the problem" language is, in my opinion, about the tradition to have fuel-rich turbines in America and oxygen-rich in Russia, and for full flow engine you need both. The turbine can run cooler, because you don't need to have gases from gas generator that hot in order to get enough power to the pumps. You're getting that power from the fact that you use full flow of both fuel and oxidizer, and since you have that additional source of power, you can relax requirement of the gas generator exhaust temperature.
    - gpm 8y ago
      > but the idea is the following: oxygen-rich flow can get hot enough to ignite metal. A relevant example of igniting metal being the first Raptor test firing, which was slightly "engine rich". Which we could see by the green given off by burning copper (and later confirmed by Elon, also somehow fixed). Video: https://twitter.com/elonmusk/status/1092270756715737088 https://twitter.com/elonmusk/status/1092270756715737088

avmich 8y ago

> wouldn't the oxidizer-rich half run hotter? You try running it as hot as possible, but without burning metal. You have about twice as much liquid oxygen by volume than kerosene in a typical engine, but you can heat kerosene to higher temperatures without burning. So... I don't think you'll get higher temperatures with oxygen gas generator?

newnewpdro 8y ago
The hackaday article explicitly states the oxygen-rich preburner exhaust was extremely hot and required metallurgical advances before turbines could survive it. How is the Raptor's oxygen-rich side any different from what the Russian's were dealing with? The article left me with the impression that the Raptor is using similarly resilient materials for the oxygen-rich side, with its language describing the US and Russian designs solving the two critical halves of the problem. There just seems to be a contradiction in the statements surrounding the turbines running cooler.
- avmich 8y ago
  > The hackaday article explicitly states the oxygen-rich preburner exhaust was extremely hot I didn't find this exact quote, but the idea is the following: oxygen-rich flow can get hot enough to ignite metal. What Russians did was to find the materials withstanding ignition best and find temperatures which are still safely avoiding ignition. This combination turned out good enough to use oxygen-rich gas generators. Raptor may be using similar approach. "Two sides of the problem" language is, in my opinion, about the tradition to have fuel-rich turbines in America and oxygen-rich in Russia, and for full flow engine you need both. The turbine can run cooler, because you don't need to have gases from gas generator that hot in order to get enough power to the pumps. You're getting that power from the fact that you use full flow of both fuel and oxidizer, and since you have that additional source of power, you can relax requirement of the gas generator exhaust temperature.
  - gpm 8y ago
    > but the idea is the following: oxygen-rich flow can get hot enough to ignite metal. A relevant example of igniting metal being the first Raptor test firing, which was slightly "engine rich". Which we could see by the green given off by burning copper (and later confirmed by Elon, also somehow fixed). Video: https://twitter.com/elonmusk/status/1092270756715737088 https://twitter.com/elonmusk/status/1092270756715737088