PPT for my first seminar on "polymers in space"

1. PE1509
Geevarghese George
Semester 6
PSE

2. Embrittlement of MISSE 5 Polymers
After 13 Months of Space Exposure

3. NASA STI Program
http://www.sti.nasa.gov/

4. Objective
To measure the embrittlement of 37
thin film polymers after LEO space
exposure

5. Why?
To design durable and stable
spacecraft components

6. Materials International Space
Station Experiment (MISSE)

7. MISSE 5
• Polymer samples were taken from PEACE
and were flown in a nadir-facing position
for 13 months
• Samples were exposed to omni-directional
charged particle radiation, thermal cycling,
& low doses of atomic oxygen and direct
solar radiation

8. Pre Flight photograph of the MISSE 5

9. Experiment Trays mounted on the ISS

10. Test for Space Induced
Embrittlement
Bend Test
Strain necessary to induce surface cracking

11. Causes of Degradation
• Space Debris
• Space Radiation
• Atomic Oxygen Interaction
• Thermal Cycling

12. Space Debris
Size <1 to 30 cm

13. Haystack Radar

14. Surface of the HST before the HST Servicing mission

15. Space Radiation
Ionizing radiation is known to
embrittle polymers

16. Photograph of embrittled and cracked Teflon FEP retrieved from the HST

17. Picture of HST
The Hubble Space Telescope

18. Atomic Oxygen Interaction

19. Thermal Cycling

20. MISSE 5 Experiments
Contained two active (FTSCE & PCSat-2)
and one passive (TBME) experiments

21. Passive Experiment
MISSE 5 Thermal Blanket Materials
Experiment
• Consisted of several Individual
experiments to measure the
degradation of more than 200
materials in the space environments
• 49 PEACE samples were flown as a
part of the Experiment

22. • MISSE 5 was placed in the zenith/nadir
position the P6 Trunion Pin Handrail of
the International Space Station
• And was exposed to LEO for 13 months
and retrieved on September 15 2006
during the STS115 mission

23. Ionizing Radiation
~2.75 Krads through 127 micrometer
Kapton

24. Sun Hours
165±25

25. Atomic Oxygen Influence
~1.8X0.10^20 atoms/cm2

26. Thermal Cycles
6400

27. MISSE 5 PEACE Polymers Experiment
=
Thermal Blanket Materials Experiment
•MISSE 5 PEACE polymers experiment
consisted of 49, 0.5X1.5in rectangular
polymer samples
•Majority of the samples were thin and
flexible

28. Primary objective was to determine the
Atomic Oxygen Erosion Yield (Ey) of
polymers after exposure to space in
nadir position

29. • Thin samples were taped on to a Kapton
blanket substrate therefore making
determination of Ey based on mass loss
difficult
• So samples were dusted with fine salt
spray particles to provide isolated locations of
protectionfrom AOE so that recession depth
measurements could be made post flight for
Ey determination

30. Experiment Procedures

31. Sectioning Bend-Test Samples
• A piece measuring 0.5 X 0.2in of each sampled
was sectioned for bend testing
• Small salt particles were removed from the
samples prior to bend testing by:
Brushing with a small horse hair water color
brush
Rinsing with water and then gently drying the
sample with pressurized Nitrogen

32. Bend Test Procedure
Strain necessary to induce surface cracking was
determined by bending the samples over
mandrels

34. 23 nos
1.253 to 0.052 cm

35. • Sample was placed with the space exposed
face down onto the semi guided apparatus
• Mandrel was pushed down onto the sample
forcing the material against the pliable surface
• Sample was bent in a U shape where the
space exposed surface was in tension and the
backside was under compression
• As the diameter of the mandrel decreases, the
tension on the space exposed surface
increases because the sample was forced to
bend more tightly around the material

36. The samples where examined before and after
bend testing at magnifications of
10x to 13.8x
Using an Olympus SMZ stereo zoom optical
microscope outfitted with a Canon digital
camera

37. Depending on the size of the samples
9 to 15
Optical microscopy pictures were taken and
observed for cracks during the bend test
process and were recorded

38. Strain Calculations
Allows the percent strain E to be calculated
based on the thickness of the sample t and
the diameter of the mandrel d
E = {t/(d+t)} * 100

39. Results and Discussion

40. TWO
samples cracked in half while on-orbit
• Sample T-1 : PMMA, 50.8 µm
• Sample X-2 : PMP, 50.8 µm

45. 17

48. These results indicate that many thin
film polymers are susceptible to
embrittlement in the LEO space
atmosphere, even after low solar and
particle radiation

49. Therefore even minimal amounts
of radiation exposure must not
be overlooked when designing
spacecraft components based on
expected mechanical properties.