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CONTENTS
 

Introduction

Fermi's Piano Tuner Problem

How Old is Old?

If the Terrestrial Poles were to Melt...

Sunlight Exerts Pressure

Falling Eastward

What if an Asteroid Hit the Earth

Using a Jeep to Estimate the Energy in Gasoline

How do Police Radars really work?

How "Fast" is the Speed of Light?

How Long is a Light Year?

How Big is a Trillion?

"Seeing" the Earth, Moon, and Sun to Scale

Of Stars and Drops of Water

If I Were to Build a Model of the Cosmos...

A Number Trick

Designing a High Altitude Balloon

Pressure in the Vicinity of a Lunar Astronaut Space Suit due to Outgassing of Coolant Water

Calendar Calculations

Telling Time by the Stars - Sidereal Time

Fields, an Heuristic Approach

The Irrationality of

The Irrationality of

The Number (i)i

Estimating the Temperature of a Flat Plate in Low Earth Orbit

Proving that (p)1/n is Irrational when p is a Prime and n>1

The Transcendentality of

Ideal Gases under Constant Volume, Constant Pressure, Constant Temperature and Adiabatic Conditions

Maxwell's Equations: The Vector and Scalar Potentials

A Possible Scalar Term Describing Energy Density in the Gravitational Field

A Proposed Relativistic, Thermodynamic Four-Vector

Motivational Argument for the Expression-eix=cosx+isinx

Another Motivational Argument for the Expression-eix=cosx+isinx
Calculating the Energy from Sunlight over a 12 hour period
Calculating the Energy from Sunlight over actual full day
Perfect Numbers-A Case Study
Gravitation Inside a Uniform Hollow Sphere
Further note on Gravitation Inside a Uniform Hollow Sphere
Pythagorean Triples
Black Holes and Point Set Topology
Additional Notes on Black Holes and Point Set Topology
Field Equations and Equations of Motion (General Relativity)
The observer in modern physics
A Note on the Centrifugal and Coriolis Accelerations as Pseudo Accelerations - PDF File
On Expansion of the Universe - PDF File
 

Pressure in the Vicinity of a Lunar Astronaut Space Suit due to Outgassing of Coolant Water

Problem:
The space suits worn by Lunar astronauts are cooled by the sublimation of water through specially designed, porous surfaces on the suit. The rate of water loss is approximately one pound per hour. If

A = .06m2

is the approximate area of the porous space suit surfaces, predict the gas pressure in the immediate vicinity of the suit. Assume a temperature of 273°K.

Solution:
The rate of water loss is approximately one pound per hour. This value corresponds to a mass loss of

1.4 x 10-4 kg/sec

1.

or a particle loss of

dN/dt = 5 x 1021 /sec

2.

where N = the total number of water particles available. If we assume that the temperature T = 273°K, and set the velocity v of the sublimating water particles equal to (2kT/m)1/2 (with m = 3 x 10-26 kg for water), then v = 500 m/sec approximately.

Now if n is the number density of the water vapor at the surface where sublimation from the suit into space is occurring, then

nv = (dN/dt)/A

3.

or

nA = (dN/dt)/v

3a.

where A = the area from which sublimation is occurring. Substituting for dN/dt and v in the second expression, we find that

nA = 1019 /m

4.

Setting A = .06m2, we find

n = 2 x 1020/m3

5.

and the pressure p = (2 x 1020/m3)/(2 x 1025/m3) atm = 2 x 10-5 atm, (where n0 =2 x 1025/m3 is Loschmidt's number, ie., the number density of an ideal gas at STP).

[Nota Bene: This calculated value of pressure may be used in estimating the probability of Paschen breakdown occurring in the immediate vicinity of an astronaut who might be working near an exposed high voltage if the Paschen curve of water vapor under the specified conditions is known.]


Please send suggestions/corrections to:
Web Related: David.Mazza@grc.nasa.gov
Technology Related: Joseph.C.Kolecki@grc.nasa.gov
Responsible NASA Official: Theresa.M.Scott (Acting)