FULL NIGHT — 9999894380 Call Girls In Patel Nagar | Delhi
2
1. Space Environment
Lecture 2 – Effects on spacecraft
High vacuum & solar radiation
Professor Hugh Lewis
SESA3038 Space Environment
2. Overview of lecture 2
• In this lecture we will take a broadly high-level look at two key
characteristics of the space environment and their effects on spacecraft
– High vacuum, in particular the effects of sublimation
– Solar radiation
• These effects will feature in later lectures on space weather, when we look a
little more closely at the specific effects of space weather on spacecraft, and
particular missions sent to observe the Sun
Space Environment – Environmental effects
3. • High vacuum
• Solar radiation
• Particle radiation
• Atomic Oxygen
Environmental effects Space Environment – Environmental effects
4. Environmental effects
• Characteristics of the space environment (order of magnitude):
UV radiation Particle radiation
Space Environment – Environmental effects
Altitude
(km)
Pressure
(Pa)
Kinetic
temperature
(°C)
Composition Gaseous density
(particles/cm)
0 105 ±30 78% N2, 21% O2, 1% A 2.5×1019
30 102 - N2, O2, A 4×1017
200 10-5 ±930 N2, O, O2, O+ 1010
800 10-8 ±1030 O, He, O+, H 106
6500 10-12 - H+, H, He+ 103
22000 10-12 - 85% H+, 15% He2+ 101 to 102
5. Environmental effects of vacuum Space Environment – Environmental effects
High vacuum:
• Sea level: 105 Pa
• ISS/Space Shuttle: 10-5 to 3×10-7 Pa
• MEO: 10-12Pa
• GEO: 10-15 Pa
• Structural problems unlikely
• Deposition on other spacecraft
surfaces is hazardous
• Thin coatings sensitive
6. Environmental effects of vacuum Space Environment – Environmental effects
Materials strength:
• The surface conditions are modified
compared to the ground where:
• Surface cracks absorb gases
• Surfaces oxidise
• For example: glass is 3 times
stronger in vacuum than air because
crack propagation is hindered
• Fatigue life is generally improved
7. Environmental effects of vacuum Space Environment – Environmental effects
Sublimation of metals in high vacuum
• Temperatures (in °C) for given sublimation rates:
0.1 µm/year 10 µm/year 1 mm/year
Cadmium 40 80 120
Zinc 70 132 180
Silver 480 590 700
Aluminium 550 680 810
Gold 660 800 950
Silicon 790 920 1080
Titanium 920 1070 1250
Tungsten 1880 2150 2500
9. Gaia Space Environment – Environmental effects
Launch: December 2013
Cost: €650 M
Objective: Astrometry
The problem:
• Water vapour outgassed from the spacecraft,
landing on cold surfaces including mirrors
https://phys.org/news/2014-06-gaia-space-telescope-team-stray.html
10. Lubricants Space Environment – Environmental effects
• Conventional lubricants not suitable
• Lubricant properties can change
due to loss of volatile components
• Oxygen (and other gases)
• Water vapour
• Use either solid lubricants
(Molybdenum Disulphide: MoS2) or
low volatility oils/greases (Fomblin)
11. Effect of solar radiation Space Environment – Environmental effects
• Polymers particularly sensitive to high
energy photons
• Resistivity modifications
• Optical changes
• Solar arrays particularly sensitive to UV
• Coverglass and adhesive subject to
darkening
• May enhance erosion by atomic oxygen
12. Effect of solar radiation Space Environment – Environmental effects
• UV degradation of BETA cloth
13. Effect of solar radiation Space Environment – Environmental effects
• UV degradation of BETA cloth
14. Effect of solar radiation Space Environment – Environmental effects
• UV degradation of painted surfaces
• Inertial Upper Stage (Data from Dr Kira Abercromby, California Polytechnic State University)
15. Activities
• The “Spacecraft Environment and its effect on
design” is chapter 2 of Fortescue, Stark &
Swinerd:
• Read this chapter (pages 11-47) to support your
learning of this topic (and those to come)
• Access to the e-book is available via the Library
website:
https://onlinelibrary.wiley.com/doi/book/10.1002/9
781119971009
• You can also find two technical reports
focused on lubricants for space systems in the
“Course Content” folder on Blackboard
Space Environment – Environmental effects
