On Thu, 2004-06-10 at 19:47, John Carmack wrote:
> Doing it with cooling passeges sounds pretty challenging to me, but we are
> planning on fabricating a palte with 16 x 1" nozzles, which should be a
> direct performance comparison with our current 1 x 4" nozzles, if I keep
> the same expansion ratios. I don't expect it to have a significant
> performance loss, and we might even get some aeruospike expansion effect at
> high altitudes if we arrange the nozzles correctly.
You just cool the two plates -- making a flat-plate heat exchanger
isn't terribly challenging, and use a material with a nice high heat
conductivity to conduct heat away from the throats. If that's not good
enough, just bore straight holes through from one side to the other and
arrange the flow paths appropriately.
On the performance side, I will be very curious to see your results.
There are four types of losses that I see affecting an array of square
nozzles much more than a single nozzle. One, the square nozzles aren't
as efficient as round ones, due to different flow behavior in the
corners. Two, since each nozzle is smaller, the boundary layers take a
relatively bigger bite than they do in a larger single nozzle. Three,
the oddly shaped combustion chamber probably will not be as efficient.
Four, since each flow passage is smaller, manufacturing defects of the
same absolute size have a larger effect.
-p
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