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## Travel on Airless Worlds Part II

25 Jun 2014, 18:11 UTC
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This is a continuation of Travel on Airless Worlds where I looked at suborbital hops.The surface of airless worlds will be exposed to radiation so it's likely the inhabitants would live underground.Moreover, it is not as hard to burrow. The deepest gold mine on earth goes down about 4 kilometers. The heat and immense pressure make it hard to dig deeper. In contrast, the entire volume of a small body can be reached.Courtney Seligman shows how to compute the pressure of a body with uniform density. The bodies we look at don't have uniform density but we'll use her method as a first order approximation.Central pressure of a spherical body with uniform density is (3/(8 π G) * g * R2Where G is universal gravitation constant, g is body's surface gravity and R is body's radius.At distance r from center, pressure is (1 - (r/R)^2) * central pressure.What is the pressure 4 kilometers below earth's surface?Earths's radius R is 6378000 meters. r is that number minus 4000 meters. g is about 9.8 meters/sec^2.Plugging those numbers into(1 - (r/R)^2) * (3/(8 π G) * g * R2gives 2120 atmospheres.Besides pressure, heat also discourages us from burrowing deeper. So it might be ...