Aerospike ISP curve

[steuben]

I was looking at the isp curve of the aerospike... and what do the last pair of numbers mean, bold?

   key = 0 340 -50 -73.71224
   key = 1 290 -21.23404 -21.23404
   key = 5 230 -10.54119 -10.54119
   key = 10 170 -13.59091 -13.59091
   key = 20 0.001

Edited July 15, 2016 by steuben

[OhioBob]

That's the slope-in and slope-out at each point on the curve.  The equation used is the following, as explained here:  Cubic Hermite spline.

You can also try plugging the numbers into the following spreadsheet to see what it looks like (sheet 1) or to convert it into easy to use polynomials (sheet 2)

http://www.braeunig.us/KSP/AtmoTutorial/FloatCurve.xlsx

ISP is an example of something that Squad made complicated when they didn't need to.  In real life, ISP vs. ambient pressure is a simple straight line relationship.

 

Edited July 15, 2016 by OhioBob