MAE 5595: Space Environments and Spacecraft Interactions. Lesson 4: Introduction

Transcription

1 MAE 5595: Space Environments and Spacecraft Interactions Lesson 4: Introduction

2 Ambient Environment Neutral Environment Low pressure environment (150km ~ 3x10-9 atm) Ambient neutral gas (LEO atomic oxygen) Outgassed molecules from spacecraft surfaces Thruster generated molecules Plasma Environment Ambient plasma (ions/electrons) Thruster generated ions/electrons Arc generated plasmas

3 Ambient Environment Radiation Environment Solar photons (X-Rays) Electromagnetic interference (EMI) Cosmic rays Particulate Environment Micro-meteoroids Orbital debris

4 Typical Spacecraft Orbits Low-Earth Orbit (LEO) 100 to 1,000 km, i < 65 Medium-Earth Orbit (MEO) 1,000 to 36,000 km, i < 65 Polar Earth Orbit (PEO) > 100 km, i > 65 Geostationary Earth Orbit (GEO) 36,000 km, i ~ 0 Interplanetary Orbit (IO) Outside Earth s Magnetosphere

5 Ambient Atmosphere for Typical Spacecraft Orbits LEO - Dense neutral gas (AO), ionospheric plasma, solar UV, orbital debris MEO - Solar UV, trapped radiation belts, plasmasphere PEO - Solar UV, dense ionosphere, orbital debris, auroral energetic particles, solar flares, cosmic rays, radiation belts GEO - High energy plasma sheet, solar UV, solar flares, cosmic rays IO - Solar wind plasma, cosmic rays, solar flares

6 The Sun: Energy Input

7 The Vacuum Environment Low pressure environment Outgassing Arcing potential Solar UV output Lack of absorption Material degradation

8 The Neutral Environment

9 The Neutral Environment Troposphere: Adiabatic lapse rate 6.5 K/km Upper Atmosphere driven by solar conditions p = nkt (n = no. density) P(z) = P(z o ) exp ((z-z o )/H); H = kt/mg)

10 The Plasma Environment

11 The Plasma Environment Daytime/Nighttime Differences Solar Input Variations

12 The Radiation Envirnoment

13 The Radiation Environment Trapped Radiation: The Van Allen Belts

14 The MMOD Environment Cheyenne Mountain ~ 8000 objects

15 The MMOD Environment

16 A Brief Picture of Spacecraft Interactions

17 Vacuum Environment Effects UV Material Degradation Photon / Surface interactions Energetic photons can break molecular bonds Alters material properties Absorptivity, reflectivity, transmissivity Conduction Strength Outgassing Release of adsorbed molecules Material mass loss due to volatiles

18 Neutral Environment Effects Aerodynamic drag Atomic oxygen material degradation Reactive species Long term exposure Spacecraft ( Shuttle ) glow Contamination Material outgassing Thruster firings Optical surfaces and solar panels

19 Spacecraft Generated Environment Own Ambient Atmosphere Material Outgassing Thruster Firings Process Generated Species Neutral Species: P OAA > P Ambient Ambient Atmosphere

20 Plasma Environment Effects Shifting of spacecraft ground Arc damage - spacecraft charging Electrostatic/Electromagn etic attraction of contaminates High energy plasma sputtering and modification of surfaces EMI Sensor interference

21 DMSP Aurora

22 Plasma Environment Effects An object in a charge neutral plasma will charge slightly negative Wake charging issues

23 Plasma Environment Effects

24 Radiation Environment Effects Degradation of materials including solar cells High energy particle penetration into materials Single event upsets, anomalies Electronics damage Material modification Arc damage

25 Radiation Environment Effects SEU/SEE due to the South Atlantic Anomaly

26 MMOD Environment Effects Destruction Destruction Destruction Destruction Destruction Destruction Destruction

27 MMOD Environment Effects LDEF Satellite

28 Synergistic Effects Weak individual effects or interactions couple in such a way as to have a nonlinear effect on the spacecraft Example: Some materials experience accelerated degradation when exposed to the the LEO AO and UV environments simultaneously {D(AO,UV) > D(AO) + D(UV)}

29 Spacecraft Subsystems Typical Spacecraft Subsystems Propulsion Attitude Control Structure Thermal Communications Payload Each subsystem can affect the spacecraft environment and be affected by the spacecraft environment

30 Multidisciplinary Subject Disciplines Involved in Spacecraft-Environment Interactions Solar Physics (Astrophysics) Rarefied Gas Dynamics Plasma Physics Gas-Surface Interactions Quantum Mechanics Electronics Engineering Material Science Anything Else You Can Think Of...