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6:52 pm
February 6, 2010
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Rocket-To-The-Moon
| | Altus, Oklahoma, USA | |
| Member | posts 685 | |
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Post edited 6:53 pm – February 6, 2010 by Rocket-To-The-Moon
I've recently been thinking about nozzle cooling and how to best approach this problem. This solution might be a bit unorthodox, but I think that it is simple and functional.
The idea is to have the entire expansion bell and throat submerged in water (water jacket). The water jacket would be pressurized and protected by a relief valve. During the burn the water would absorb heat from the motor causing the water to boil off. The steam would then be used for actuation of the flight controls (paddles in the exhaust stream as on the X-31). The water jacket would need to be pre-pressurized before flight so that there is pressure until steam can build up.
The nozzle bell would need to be made of a material that has a high heat conductivity and high melting temperature. A nickel alloy may be able to fit this bill.
Thoughts?
 
Keep in mind that this applies more if the motor burns for a fairly lenghty time (1+ mintue).
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Main Workgroups: Propulsion & Spacecraft Engineering
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8:01 pm
February 6, 2010
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brmj
| | Rochester, New York, United States | |
| Member | posts 402 | |
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One thought is that as the water level lowered, areas of the engine an nozel assembly would cease to be cooled. Another thought is that something like this could perhaps be done using excess cryogenic fuel, oxidizer or, if we used it, pressurent. That might be mre exxicient, since those are less massive and initially colder. I'm not sure if the temperature differences would cause problems, though.
Over all, I think this is an interesting idea.
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Main work groups: Propulsion (booster), Spacecraft Engineering, Computer Systems, Navigation and Guidance (software)
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8:03 pm
February 6, 2010
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Rocket-To-The-Moon
| | Altus, Oklahoma, USA | |
| Member | posts 685 | |
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For OHKLA we won't have any cryogenic fuels to help cool the nozzle. The lowering of the water level is a concern, but the system could be designed so that the water level never goes below a certain critical position.
Probably a silly idea. Posted here for documentation.
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Main Workgroups: Propulsion & Spacecraft Engineering
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8:17 pm
February 6, 2010
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brmj
| | Rochester, New York, United States | |
| Member | posts 402 | |
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I was still thinking in terms of CLLARE. Sorry.
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Main work groups: Propulsion (booster), Spacecraft Engineering, Computer Systems, Navigation and Guidance (software)
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11:50 pm
February 6, 2010
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Luke Maurits
| | Adelaide, Australia | |
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Maybe I've missed something, but I'm a little confused about this idea. It seems like a fine idea in its overall operating principles, I'm just not seeing why we need something like it for OHKLA. Why do we need vector paddles if the idea is to go straight up? I can see why they would be handy for an orbital insertion project, but for suborbital I didn't think we would have any need for this kind of control. Also, we seem to have fairly well established that the best approach for a suborbital flight is to have a burn that is very high thrust and very short duration – CSXT used only 15 seconds, if I recall. Perhaps I'm being naive about nozzle endurance, but for a burn that short couldn't we largely get away with just ablative and radiative cooling? I can see how this sort of approach would work well for rocket burns that were several minutes long (like we might see on CLLARE), but for a burn that will probably be between 10 and 20 seconds I feel like it may be overkill.
I get the feeling I may have completely missed something here so please feel free to point out anything stupid I've overlooked.
I want to make it clear that I don't think this idea is stupid at all, just that I'm not sure it's applicable to OHKLA. To CLLARE, however, or other projects where we are doing orbital insertion, they seem like perfectly good ideas that we should definitely consider.
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Main CLLARE workgroups: Mission Planning, Navigation and Guidance. I do maths, physics, C, Python and Java.
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1:07 am
February 7, 2010
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brmj
| | Rochester, New York, United States | |
| Member | posts 402 | |
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Actually, I think Rocket and I have completely missed something. Your analysis of this looks fundimentally sound. I suspect Rocket and I were still in a CLLARE mindset and my previous blunder was just one example of this. Rocket, is this correct or is there something that is being missed here?
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Main work groups: Propulsion (booster), Spacecraft Engineering, Computer Systems, Navigation and Guidance (software)
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8:31 am
February 7, 2010
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Rocket-To-The-Moon
| | Altus, Oklahoma, USA | |
| Member | posts 685 | |
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The thrust vectoring might not be necessary for anything other than gaining experience with guidance and control. If that is the case then the steam could just be aimed directly downward for a few Newtons of extra thrust.
My thoughts on the long duration burn also stem from gaining experience. However, going to the OHKLA wiki page reminds me that I am a little bit off base since we are aiming for the absolute minimum.
Maybe we can shelve this and wait for OHKLA Advanced.
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Main Workgroups: Propulsion & Spacecraft Engineering
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