Re: [Starlink] some post Starship launch thoughts

["Mark Handley" <mark@handley.org.uk>]

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My understanding was that a pad water deluge system isn't primarily to remove energy from the exhaust plume itself, but rather to reduce the extreme sound level all the pad equipment and the booster are exposed to outside of the exhaust plume.  At really high sound levels you're achieving a near vacuum in the rarefactions of the sound waveform, and this low pressure will cause water to boil, removing energy from the sound waves.  Or at least that's how I assumed it works :-)

Mark

On Wed, 26 Apr 2023, at 10:05 PM, Eugene Y Chang via Starlink wrote:
> Rodney, 
> I agree with your point of view.
> 
> To neutralize the exhaust of the rocket engine, it is all about taking the energy out of the exhaust. Taking out the energy will slow the speed of the exhaust gas and take down the temperature. 
> 
> To get into more nitty gritty, the amount of heat absorbed by H2O or LN2, depends on the dT (the temperature change) and also any heat of phase transition (e.g. liquid to gas).
> Gene
> ----------------------------------------------
> Eugene Chang
> eugene.chang@ieee.org
> o 781-799-0233
> 
> 
> 
>> On Apr 26, 2023, at 10:41 AM, Rodney W. Grimes via Starlink <starlink@lists.bufferbloat.net> wrote:
>> 
>>> As always I enjoy the flood of information we get on this list!
>>> 
>>> still, so far, my research on a nitrogen deluge system (instead of
>>> water) has come up empty for me, except as a fire suppressant. So it?s
>>> either crazy or brilliant. Or both! I really liked the idea of
>>> something cooler that was a natural byproduct of the LOX process...
>> 
>> I dont think cooler does much, isnt it the "energy of vaporization"
>> that is actually doing all the "work" in this type of system?
>> 
>> H2O is 40.7 kJ/mol and LN2 is 5.6 kJ/mol so you would
>> need ~7 times as much LN2 to do the same work.
>> 
>> And the reason N2 is used as a fire suppressant is again not
>> because of temperature, but because it displaces the O2 and
>> suffocates the fire.  N2 is also easier on our ozone layer
>> than the prior used Halon.  Finally, this is usually
>> compressed N2 gas, not LN2.
>> 
>> --
>> Rod Grimes                                                 rgrimes@freebsd.org
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