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Post by quarkster on Sept 30, 2016 4:34:41 GMT
Throat radius seems to only affect mass, meaning there is no reason to ever increase it.
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Post by RA2lover on Sept 30, 2016 15:32:59 GMT
There's an use for it - it allows you to increase the space available for the reactor without the associated pressure increase that comes with increasing the chamber wall contraction ratio.
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Post by qswitched on Sept 30, 2016 22:12:23 GMT
This is expected behavior. If you scale up or down the throat while keeping the expansion/contraction ratio the same, there should be exactly no change to exhaust velocity, thrust, or mass flow rate. The only change it allows you is greater stress tolerances when it is larger.
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Post by quarkster on Oct 1, 2016 0:20:33 GMT
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Post by qswitched on Oct 1, 2016 0:54:02 GMT
I am using that exact equation for exhaust velocity.
In an NTR, the temperature is dependent almost entirely on neutron flux and mass flow rate. Since you are keeping both the same, you are keeping the combustion temperature nearly the same in both cases. One thing you will notice is while the combustion temperature is relatively constant while the throat radius changes, the film temperature and the chamber wall temperatures will vary heavily from these changes. These affect the stresses of the engine heavily, but the combustion temperature remains the same within your reactor, and thus the exhaust velocity as well.
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