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>"Regenerative cooling" is a rocket term. It came to mind because I used to be an aerospace engineer. There's no requirement in the definition of regenerative c

>"Regenerative cooling" is a rocket term. It came to mind because I used to be an aerospace engineer. There's no requirement in the definition of regenerative cooling for the coolant to be dumped. ? Regenerative cooling in rocketry uses propellant. Propellant is always dumped overboard, because it's propellant. Please show me a rocket that uses closed loop cooling of the rocket nozzle. >Filtering and then compressing atmosphere, running it through a heat exchanger, and then letting it expand through the cooling channels before dumping it doesn't seem obviously worse than having kilometers of refrigerant running around. My turn to be pedantic about definitions: this sure sounds like closed loop cooling to me! The working fluid is air, you draw it from a big reservoir, (the atmosphere) cool something with it, then return it to the reservoir. (Something you can't do with open-loop regenerative cooling of a rocket nozzle, since the coolant gets burned at the end of the cycle) However, maintaining the air dryers and replacing the filters sounds like it wouldn't be any cheaper than conventional phase-change cooling, and having to build custom vacuum/compressor pumps for the hyperloop project is going to be more expensive than buying COTS vacuum pumps.

JumpCrisscross 9y ago
> Please show me a rocket that uses closed loop cooling of the rocket nozzle The most famous one is the under-development SABRE [1], which includes a closed-loop helium cycle. For cryogenic rockets, closed-loop cooling of the nozzle has been explored [2] to avoid hydrogen embrittlement and oxidation of the nozzle channels, as well as to simplify plumbing. In any case, we've devolved into arguing semantics. > My turn to be pedantic about definitions: this sure sounds like closed loop cooling to me! I was figuring on dumping the air once done versus worrying about a reservoir. That said, I haven't done any math on the benefits of saving the return piping (and reservoir cost and maintenance) versus using something traditional. > maintaining the air dryers and replacing the filters sounds like it wouldn't be any cheaper than conventional phase-change cooling, and having to build custom vacuum/compressor pumps for the hyperloop project is going to be more expensive than buying COTS vacuum pumps Fair enough. As you observe, it's a problem I haven't seen a suitable solution to (apart from burying, which trades the thermal problem for, in my view, the better water management problem and the scarier land-use problem.) [1] https://en.wikipedia.org/wiki/SABRE_(rocket_engine) https://en.wikipedia.org/wiki/SABRE_(rocket_engine) [2] https://www.google.com/patents/US3516254?dq=closed+loop+rocket+engine&hl=en&sa=X&ved=0ahUKEwjwr4XF8uvWAhUm54MKHeXHAdUQ6AEINjAC https://www.google.com/patents/US3516254?dq=closed+loop+rock...
- sbierwagen 9y ago
  >The most famous one is the under-development SABRE [1], which includes a closed-loop helium cycle. From the linked article: >>The 'hot' helium from the air precooler is recycled by cooling it in a heat exchanger with the liquid hydrogen fuel. It's open-loop regenerative cooling, with helium as an intermediate coolant. The heat still ends up in the propellant, which gets dumped overboard. Not closed-loop. That patent also specifies a heat exchanger to the propellant tank. >I was figuring on dumping the air once done versus worrying about a reservoir. A poorly telegraphed joke. The atmosphere, here, is the reservoir. I have edited my comment.
BRAlNlAC 9y ago
>However, maintaining the air dryers and replacing the filters sounds like it wouldn't be any cheaper than conventional phase-change cooling, and having to build custom vacuum/compressor pumps for the hyperloop project is going to be more expensive than buying COTS vacuum pumps. Just want to point out a facet of such a project that you probably haven't considered. The EPA puts strict requirements on the operators of refrigerant systems, the way they categorize operator class is based on pounds of refrigerant. Thus even though a COTS phase change refrigerant system seems like the obvious choice for Hyperloop One, because of regulatory burden it would almost certainly unfeasible. A refrigeration system big enough to cool a hyperloop would have to have every inch of refrigerant line spray tested every 3 months or an insanely expensive monitoring system. https://www.arb.ca.gov/cc/rmp/rmpcomply.htm#large https://www.arb.ca.gov/cc/rmp/rmpcomply.htm#large
- hwillis 9y ago
  Heat tubes use distilled water as a refrigerant and do not use pumps

JumpCrisscross 9y ago

> Please show me a rocket that uses closed loop cooling of the rocket nozzle The most famous one is the under-development SABRE [1], which includes a closed-loop helium cycle. For cryogenic rockets, closed-loop cooling of the nozzle has been explored [2] to avoid hydrogen embrittlement and oxidation of the nozzle channels, as well as to simplify plumbing. In any case, we've devolved into arguing semantics. > My turn to be pedantic about definitions: this sure sounds like closed loop cooling to me! I was figuring on dumping the air once done versus worrying about a reservoir. That said, I haven't done any math on the benefits of saving the return piping (and reservoir cost and maintenance) versus using something traditional. > maintaining the air dryers and replacing the filters sounds like it wouldn't be any cheaper than conventional phase-change cooling, and having to build custom vacuum/compressor pumps for the hyperloop project is going to be more expensive than buying COTS vacuum pumps Fair enough. As you observe, it's a problem I haven't seen a suitable solution to (apart from burying, which trades the thermal problem for, in my view, the better water management problem and the scarier land-use problem.) [1] https://en.wikipedia.org/wiki/SABRE_(rocket_engine) https://en.wikipedia.org/wiki/SABRE_(rocket_engine) [2] https://www.google.com/patents/US3516254?dq=closed+loop+rocket+engine&hl=en&sa=X&ved=0ahUKEwjwr4XF8uvWAhUm54MKHeXHAdUQ6AEINjAC https://www.google.com/patents/US3516254?dq=closed+loop+rock...

sbierwagen 9y ago
>The most famous one is the under-development SABRE [1], which includes a closed-loop helium cycle. From the linked article: >>The 'hot' helium from the air precooler is recycled by cooling it in a heat exchanger with the liquid hydrogen fuel. It's open-loop regenerative cooling, with helium as an intermediate coolant. The heat still ends up in the propellant, which gets dumped overboard. Not closed-loop. That patent also specifies a heat exchanger to the propellant tank. >I was figuring on dumping the air once done versus worrying about a reservoir. A poorly telegraphed joke. The atmosphere, here, is the reservoir. I have edited my comment.

BRAlNlAC 9y ago

>However, maintaining the air dryers and replacing the filters sounds like it wouldn't be any cheaper than conventional phase-change cooling, and having to build custom vacuum/compressor pumps for the hyperloop project is going to be more expensive than buying COTS vacuum pumps. Just want to point out a facet of such a project that you probably haven't considered. The EPA puts strict requirements on the operators of refrigerant systems, the way they categorize operator class is based on pounds of refrigerant. Thus even though a COTS phase change refrigerant system seems like the obvious choice for Hyperloop One, because of regulatory burden it would almost certainly unfeasible. A refrigeration system big enough to cool a hyperloop would have to have every inch of refrigerant line spray tested every 3 months or an insanely expensive monitoring system. https://www.arb.ca.gov/cc/rmp/rmpcomply.htm#large https://www.arb.ca.gov/cc/rmp/rmpcomply.htm#large

hwillis 9y ago
Heat tubes use distilled water as a refrigerant and do not use pumps