ESA SME Initiative Course Materials and Processes Human Spaceflight

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					                                     The ESA SME Initiative Training Courses


      Human Spaceflight




      ESA SME Initiative
Course Materials and Processes



                 Dr. Thomas Rohr
      Materials Physics and Chemistry Section
         Materials and Processes Division
     Product Assurance and Safety Department




               Materials and Processes Division                   Sheet: 1
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                                                  The ESA SME Initiative Training Courses


                         Introduction



!   1st Human spaceflight on April 12, 1961 (Yuri Gararin in Vostok I)
!   Soviet/Russian programs
    Sputnik, Vostok, Voskhod, Soyuz, Lunar, Salyut, Mir
!   US programs
    Mercury, Gemini, Apollo, Skylab, Space Shuttle
!   International programs/missions
    Apollo-Soyuz
    Shuttle-Mir (ISS phase I)
    ISS
!   Future programs
    Moon, Mars

                            Materials and Processes Division                   Sheet: 2
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          ISS




                               Artist's impression
                               showing the current
                               configuration of ISS
                               as it passes over the
                               Dutch coast
                               ESA-D.Ducros 2004

Materials and Processes Division                       Sheet: 3
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      Space Inhabited Environment I


!   Impact of space environment on humans
    Microgravity: Blood volume redistribution, muscular atrophy, vestibular
    problems (motion sickness), bone decalcification
    Radiation, debris: Shielding required
    Vacuum: Life support system (atmosphere control and revitalisation,
    temperature control, water recovery, waste management, etc.)
!   Space inhabited environment ↔ materials
    Pressurised volume, humid atmosphere, living organisms
    Flammability
    Toxicity
    Corrosion, biocorrosion
    Fungus growth

                             Materials and Processes Division                   Sheet: 4
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Space Inhabited Environment II



                                              Loss of material            Catastrophic
                    Combustion
                                                 function                    failure



                    Off-gassing,
                                          Toxic gases               Aggressions to life
                  ageing, corrosion
Life supporting
  atmosphere
                                          Numerous problems,
                   Degradation of
                                         particularly insulation,
                  material function
                                               gasketing



                     Biological
                                                   Toxicity                 Diseases
                      growth



                       Smell            Discomfort




                          Materials and Processes Division                                Sheet: 5
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         Off-Gassing (ECSS-Q-70-29)


The determination of off-gassing products from materials and assembled articles
to be used in a manned space vehicle crew compartment

Purpose: Determine the identity and quantity of volatile off-gassed products
from materials and assembled articles.

   Material screening test
   - Quantity of total organics (pentane equivalent) off-gassed in µg/g
   - Quantity of carbon monoxide off-gassed in µg/g
   - Identification of contaminants in excess of 10 µg/g of material

   Acceptance limits
   - Total Organics: < 100 µg/g material
   - Carbon monoxide: < 25 µg/g material

                                Materials and Processes Division                   Sheet: 6
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   General Off-Gassing Procedure I


General test for materials/assembled articles
! Identification and quantification of all contaminants present
! Use of T-values for acceptance

Test chambers
Different facilities are available, e.g.
Heraeus ovens 128 L and 718 L
Glass bottles 1, 2.5 and 5 L

Test conditions
! Mass (material) ~ 5 g/L test volume
! Atmosphere: synthetic air or clean/dry air
! Temperature 50°C
! Pressure: 1 bar
! Duration: 72 h

                                   Materials and Processes Division                   Sheet: 7
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      General Off-Gassing Procedure II

Analysis and quantification
! Sampling: ~ 250 mL (flow rate 25 mL/min) gas on adsorption trap after max. 12 hrs
  recovery to reach RT → pre-concentration of gaseous components
! Desorption and injection into gas chromatograph, separation of components
! Identification via mass spectrometer
! Quantification via TCD (thermal conductivity detector), MS

→   Each component that was off-gassed is identified and quantified

Acceptance limits
! The quantity of each individual off-gassed product shall result in a predicted spacecraft
  concentration below the SMAC value (Spacecraft Maximum Allowable Concentration).
! Toxic Hazard Index (T) shall not exceed 0.5. T is determined by
                                                                                  n
                                                                                       ci
  calculating the ratio of the projected concentration of each off-gassed T =
  product to its SMAC value and summing up these ratios for all
                                                                                  ∑
                                                                                i =1 SMACi
  off-gassed products.
                                   Materials and Processes Division                   Sheet: 8
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Off-Gassing - GC/MS




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                                Odour Test


NASA-STD-6001: Determination if the odour is objectionable or revolting

!   The odour of a material or assembled article is objectionable or revolting if an
    average of 2.5 or higher on an odour characteristic scale is obtained:
    0 - Undetectable
    1 - Barely detectable
    2 - Easily detectable
    3 - Objectionable
    4 - Revolting

!   Sample preparation is the same as for Off-gassing test

!   Test panel shall consist of 5 qualified persons


                                 Materials and Processes Division                  Sheet: 10
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                          Flammability I


Identification of flammable materials used, their amounts, thickness, exposed
surface, exposure environment.

Identify propagation paths for exposed materials (including housing)
If configuration is container, evaluate its capability to contain an internal fire
If unacceptable configuration through the configuration assessment, there are two options:

! Use fire break concepts to reduce flammability hazard by isolating the
  flammable materials
! Conduct a test to show acceptability of configuration


Screening of space materials
Wire test

                               Materials and Processes Division                  Sheet: 11
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                                             Flammability II



            Are there any flammable materials or multiple
            applications of flammable materials in amounts    no
                                                                    Acceptable
            > 45 g or 65 cm² in manned compartments or
            > 450 g or 30 cm in other compartments?                                               yes
                                                                                                                         yes
                                       yes                               Will the container contain any internal fire?         Acceptable

                 Are exterior surfaces and any externally     no
                                                                                           no
                     attached materials flammable?
                                                                                                                         no
                                                                                 Does the container contain air?               Acceptable
                                       yes
                                                                                                  yes
      yes       Could a fire propagate on the surface more
                than 15 cm in manned compartments or 30                 Are internal ignition sources precluded while    yes
                       cm in other compartments?                                                                               Acceptable
                                                                           the container is located in the orbiter?
                                no
                                                                                           no
Unacceptable,                                                no
 modification               Is it a container?                     Acceptable
                                                                                       Unacceptable,
  required
                                       yes                                           modification required


                                                                                          Source: Adapted from NSTS 22648
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           Reduction of Flammability
                   Hazards


!   Limitation of flammable materials by replacement with a non flammable one

!   Restriction of propagation paths through

    Covering of flammable materials with a non
    flammable one

    Separation of flammable materials
    (avoid propagation)




                              Materials and Processes Division                  Sheet: 13
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           Upwards Propagation Test
               (ECSS-Q-70-21)

                                                                  64 mm
Determine if a material, when exposed to a
standard ignition source, will self-
extinguish and not transfer burning debris,
which can ignite adjacent materials

Test criteria




                                                   300 mm
! Self extinguishing within 15 cm
! No transfer of burning debris                                                    Test
                                                                                 Specimen
! Burn Propagation time < 10 min


Sample: 300 x 64 mm², worst case thickness
                                                                              Ignitor
Test atmosphere: Depends on application
(24% O2 or more…)
                                                                               NiCr



                              Materials and Processes Division                        Sheet: 14
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Upwards Propagation Test




       Materials and Processes Division                  Sheet: 15
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               Wire Flammability Test
                  (ECSS-Q-70-21)


Determine if a wire insulation system, when exposed to an external ignition
source, will self-extinguish and not transfer burning debris, which can ignite
adjacent materials

Acceptance criteria: Prior to flame application, while heating wire to maximal operation
T, no spontaneous combustion, splitting insulation nor baring conductor During ignition
and combustion no flaming droplets/particles After burner is extinguished, cease
flaming within 10 s and within a total burn length of 150 mm.

Sample: 5 times 1 m
Test atmosphere: Depends on application (20% O2 or more…)




                                Materials and Processes Division                  Sheet: 16
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Wire Flammability Test I




       Materials and Processes Division                  Sheet: 17
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Wire Flammability Test II




       Materials and Processes Division                  Sheet: 18
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            Microbial contamination I


Closed system, need to monitor air, water (recycled) and surfaces.
Several studies claim that microgravity is accelerating microbial growth.

Study on Mir between 1987 – 1999
! 234 species of microorganisms (108 bacteria and 126 fungi) were identified
! The largest diversity (64 species) was related to the group of technophylic fungi,
   destroying polymers and corroding metals!

Sources
! Initial contamination of materials during manufacturing and assembly
! Supplies and delivery of supplies to Mir
! Secondary contamination during the lifetime of Mir
! The crew and any other biological material on board e.g. animals, plants, microbes
  used in scientific experiments.

                                Materials and Processes Division                  Sheet: 19
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            Microbial contamination II



Effects of microbial contamination on materials

!   Mechanical damage of polymeric material by penetration of fungal mycelium into the
    bulk material

!   Colonies of microorganisms can deposit on surfaces to create biofilms. Degradation
    of polymeric material (components can act as nutrients), development of (pitting)
    corrosion underneath due to local potential differences
    - Dissolved oxygen is available at the metal/solution interface
    - Production of acidic metabolites
    - Production of sulfide metabolites by anaerobic bacteria

No general approach for evaluation of the bio-corrosion potential

                                Materials and Processes Division                  Sheet: 20
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                       Fungus Growth I


According to ISS requirements (SSP 30233) materials which are non-nutrient to fungi
shall be used as defined by MIL-STD-810F (method 508) or as identified in MIL-HDBK-
454 (guideline 4, fungus inert materials).

Exceptions are:
! Materials in crew areas where fungus would be visible and easily removed
! Materials inside environmentally sealed containers with RH < 60%
! Materials inside electrical boxes where the temperature is always ≥ to ambient cabin
   temperature
! Materials with edge exposure only
! Materials stowed with no risk of condensation in stowage locations
! Crew clothing items
! …


                               Materials and Processes Division                  Sheet: 21
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                       Fungus Growth II


Fungus inert materials according to MIL-HDBK-454 (guideline 4)

Group 1 (fungus inert)
Examples are acrylics, ceramics, FEP, glass, metals, PAN, PA, PC, PET, PI, PP, PS,
PTFE, silicones

Group 2 (fungus nutrient)
Examples are ABS, cellulose acetate, epoxy resins, MF, PF, LDPE, PMMA, PUR,
synthetic rubbers, UF

When fungus-nutrient materials must be used, they shall be treated to prevent fungus
growth. Materials not meeting this requirement shall be identified including any action
required such as inspection, maintenance, or replacement periods.


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