Tuesday, December 16, 2008

Prochron Heads Up

I am currently doing a huge batch of much modernized AFAL (http://www.dunnspace.com/isp2001.zip - under 300k...don't bother unless you are, or want to become, a rocket scientist runs in DOS...even in XP's prompt window...is two colors...black and white...or black and green if you find an old enough system.) The "modernization" of AFAL data involves putting it into an OpenDocuments spreadsheet and adding conversion formulas for specific impulses (to m/s), pressures (to kPa), and for ambient pressures and total thrust pressures (this latter needed to size motors for vehicle concepts).

There is some bad news for Prochron...the Isp's used in the spreadsheet and previous posts are too high for the first stage. I saw this when I dug up my April 2007 notes for Symtex. The new Isps are about 2100m/s at sea level, 2700m/s in vacuum, but it should still be possible to achieve 3000m/s in the upper stages and on the OpenLuna lander versions.

AFAL batch work is still needed for above Prochron/Symtex oxykerosene work, increased exit pressures for Prochron/Symtex, oxy/LNG and possibly oxyhydrogen for Freezerburn. I'll only do the oxyhydrogen if I get writer's block, or once I've worked through to Lilmax. The "flip point" for oxyhydrogen starting to benefit the Ascent Roadmap is probably in the 100-500 tonne LEO payload range...and my personal "point" guess is 250 tonnes before I start using it prior to achieving low energy orbit. A lot of more worthwhile work remains before I start looking for that point with calculators and spreadsheets.

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