1 MAVEN Breakup & Burnup Analysis for Planetary Protection M. Johnson LMSSC

2 MAVEN B&B Background The MAVEN project intends to utilize breakup and burnup analyses to aid in meeting planetary protection bioburden requirements –Aeroheating due to entry will meet sterility requirements as specified by NASA Policy Guideline (NPG) C for a portion of the spacecraft components –These components will be excluded from contributing to the spore count at launch The B&B approach will be similar to that performed by the Mars Reconnaissance Orbiter program

3 Breakup & Burnup: General Approach Spacecraft trajectory is modeled for atmospheric entry –Aerodynamics are either tumbling or stable –Points are identified where components would separate from main spacecraft Separate trajectories are initiated for each new object, all the way down to box-level Aerothermal heating is tracked for each object Thermal analysis determines temperature profile and whether item burns-up or not –If it doesn’t vaporize, as long as the temperature reaches 500 C or higher for at least 0.5 sec, the surface is considered sterilized This is sufficient for externally contaminated items Items with embedded organics may fail this criteria and carry their spore count forward to the final assessment –Items that do not burn-up or reach sterilization conditions are considered non-exempt and are tracked for their spore burden Structural analysis will determine points in the entry where structural failure of components will occur and spawn separate parts for analysis –Generate new trajectory and heating data for the new object from this point forward Total spore burden is based on items that do not vaporize or reach sterilization temperature –Total allowable spore burden of non-exempted items is 5 x 10 5 at launch –These items may be subject to cleaning if needed in order to reduce their bioburden

4 24 February 2016 MAVEN Breakup & Burn-up Analysis Model FINISH Orbiter Decomposition Phase Module Decomposition PhaseComponent Heating Phase Track trajectory of each module Calculate altitude modules break away Determine critical breakpoints: Load capability Dynamic forces Thermal effects Orbiter enters flow Altitude estimate Stable or unstable START Module enters flow Altitude/Vel calculated Component geom (sph/cyl shape) Mat’l properties/Therm effects Calculate altitude module breaks up Track trajectory of each component Assess heat load on each component Compare heat of ablation for mat’l Determine component burnup altitude or survival survived Burned up Higher fidelity thermal model for component’s true geometry. Assess if burned-up Calculate temperature profiles for surviving components Bio-contamination assessment phase Assess bioburden of compnent Sterile Burned up (no bioload) Burned up (no bioload) Not Sterile

5 24 February 2016 MRO Breakup and Burn-up Approach LMA’s standard set of orbital, entry and CFD software codes were used to define entry environments Structural, thermal and chemical properties of the orbiter were modeled to simulate mechanical response to entry environment Stable and tumbling entry scenarios were investigated B&B analysis identified those orbiter elements that fail to burn-up or reach 500 deg. C for 0.5 sec or longer Non-exempt: Classification of Components that fail to burn-up or reach 500 deg. C for 0.5 sec or longer A maximum value of 5.0 x 10 5 spore allocated at launch Target bio-reduction for hardware with highest bio-burden values until the aggregate threshold value of <5.0 x 10 5 spores is met

6 24 February 2016 Table 1 of Non-Exempt Hardware (MRO)

7 MRO Conclusions Generalizations –A lot of things don’t completely burn up! –Metal items (boxes, brackets, bolts, tubing, etc) exposed to heating flow will sterilize –Interior of prop components exposed to hydrazine are sterile –Composites contain a lot of spores, but also ablate easily –Cards internal to electronics boxes are shielded by their boxes and often survive PWBs are actually very low burden, but populated cards have a lot of surface area –Lightweight items will burn up if attached to s/c and exposed but may survive if they can break off early Thin wires, mesh likely ok, but blanketing probably not –Internal lubricants likely to carry forward spores The value of looking at MRO is not to reduce B&B work (it all needs to be done in order to prove the final spore count), it is in focusing assaying and cleaning efforts on the things that are likely to survive

8 Implications for MAVEN Payloads Standard contamination control process should be sufficient in most areas Intra-instrument harness and payload-provided MLI should be baked out –Probably already being baked out for outgassing; time just needs to be extended Assays of work areas before assembly will help lower spore burden –Actuals are usually less than standard numbers Assay electronics box interiors and card surfaces throughout manufacturing –Before/after PWB cleaning, after conformal coating Assay after assembly Inputs to B&B analysis –Material list –External dimensions –Electronics card dimensions and part population density (rough) –Component masses (enclosure, cards, baffles, etc)

9 Accepted Bio-Burden Reduction Options Dry Heat Microbial Reduction for Targeted Hardware –Any of three time - temperature combinations may be used for a 90% reduction in bio-burden (one order of magnitude): 110C for 62.5 hours 125C for 6.25 hours (or 120 C for 54 hours a concession from JPL PP office) 146C for hours –Note 1: NASA Policy Guideline NPG B require Four Orders of Magnitude reduction –Note 2: 120 & 125 C yield minimal impact to hardware and chamber time The absolute humidity must be controlled for the entire period by either of two methods: –The chamber may be purged with dry nitrogen gas with the water vapor content in the purged volume less than 0.1% relative humidity at the process temperature. Or –The chamber may be evacuated to a pressure of less than 1 Torr. Proxy Assays –Provides better (lower) spore numbers than the assumed values for a particular environment IPA Wipe and Assay