ASEN 5158 Space Habitat Design

9/18/2008

Chapter 3   The Space Environment – Hazards and Effects

 

Learning Objectives

1.                  Identify and explain effects due to different types of space flight environmental parameters that can affect vehicle and crew

2.                  Distinguish between natural and man-made phenomena

 

Major Environmental Factors

 

Microgravity, Thermal Extremes & Vacuum

•         Lack of natural convection

•         Altered stress/strain structural loads

•         Collection and removal of heat via convective, conductive and radiative pathways

•         Pressure shell requirements and external surface degradation with vacuum exposure

 

Vacuum and Solar UV

•         0.3 ΅m wavelength radiation present

–        Normally atmosphere absorbs it

•         Severs some molecular bonds

•         Dictates thermal equilibrium

•         Surface degradation

–        Alters absorptivity / emissivity ratios

•         Sunburn

 

Vacuum - Contamination

•         Molecular contamination

–        Outgassing

–        Devices like solar arrays most susceptible

•         Particulate contamination

–        RCS thrusters

–        Water dumps

–        Gas purges

 

Non-ionized atoms

•         Gasses are present at orbital altitudes

–        O2, H2, He, Ar, N2, O

•         Atomic oxygen is chemically reactive

•         Effects

–        Atomic Oxygen chemical erosion

–        Drag

–        Sputtering physical erosion

–        Glow (optical instrument consideration)

 

Plasma

•         Arcing

–        Surface damage

–        Dielectric breakdown

–        Electromagnetic Interference (EMI)

•         Floating potential changes

–        Low Earth Orbits w/o solar arrays ~ 1 V

–        LEO w/ solar arrays ~ function of array voltage

–        Higher orbits ~ kV potential possible

 

S/C charging

•         Plasma at different altitudes (LEO-GEO)

–        Density decreases with altitude

–        Kinetic energy increases

•         LEO = 1 eV

•         GEO = 1000 eV

•         Lorenz Force created ~ f (ν x B)

–        force on a charged particle traveling in a magnetic field

 

•         Bottom line – plasma charging effects must be mitigated by design

 

 

Radiation

•         High energy particles/waves that deposit their energy in materials

–        Particulate (electrons, protons, neutrons)

•         mainly ionizing

–        Electromagnetic (gamma, x-ray, UV, etc)

•         mainly non-ionizing

•         Can’t see, touch, predict or define exactly

•         Material dependent

•         Hard to design for or protect against

 

Micrometeoroids & Orbital Debris (MMOD)

•         Micrometeoroids – natural matter

–        20,000 tons per year reach Earth

•         Orbital debris – from other spacecraft

–        8500 objects bigger than baseball tracked by the Air Force Space Command

–        Estimate 40,000 golf ball sized and millions smaller objects

 

Self-induced

•         Contamination/degradation

–        Off-gassing, gas leaks

–        Thruster firings

–        Fluid dumps

•         Noise (internal habitat)

•         Effects

–        Reduced effectiveness of sensors/ solar arrays, radiators

–        Obscured windows or instruments

–        Human performance/hearing loss

 

Summary

 

•         General space environment issues are similar to any satellite design

•         Important to be able to relate added complexity of these effects to specific human spacecraft design issues

 

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