# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

**Re: Lunars barometric pressure correction**

**From:**Bill B

**Date:**2005 Apr 22, 16:42 -0500

> Bill wrote: > "Big difference between the two formulas when the elevation > gets into miles." Frank replied: > Yes, and given today's cheap computing, might as well use the exponential > formula. By the way, you can also use it to answer the question "where does > space begin?" Just set the equation for density of the air: > density = exp(-altitude/34,000feet) > equal to 0 and solve for the altitude. :-) Having little success with modifying the formula with my math skills. Trying to manipulate the exponent and or find the nth root of zero has me off in deep space. Did try the plug and chug method with the TI-30, and ran out of computing power approx. 1277 nm. Looks like with enough computing power it could go on like pi. Interesting as I would have thought the value would have been in the 60-120 nm range. It did lead me to check out the Federation Aeronautique Internationale's definitions for outer space, which are located at: http://encyclopedia.laborlawtalk.com/Outer_space Two values that interested me: Reentry from orbit begins at 122 km 100 km - Aerodynamic surfaces no longer function As to the bigger question, "where does space begin?" (Or end?) After reviewing the works of philosophers, mathematicians, and physicists--and using two TI-30Xa calculators simultaneously-- I arrived at the value "42." Back to Schaum's Theory and Problems of Basic Mathematics, Bill