63rd International Astronautical Congress 2012, Naples, Italy

LARGE SCALE EXPERIMENTS ON SPACECRAFT

FIRE SAFETY IAC-12. A2.2.2

DAVID L. URBAN & GARY A. RUFF: NASA GLENN RESEARCH CENTER, USA

OLIVIER MINSTER & BALAZS TOTH: ESA ESTEC, NOORDWIJK, NETHERLANDS

A. CARLOS FERNANDEZ-PELLO: UC BERKELEY, BERKELEY, CALIFORNIA, USA

JAMES S. T'IEN: CASE WESTERN RESERVE UNIVERSITY, CLEVELAND, OHIO, USA

JOSE L. TORERO & ADAM J. COWLARD: UNIVERSITY OF EDINBURGH, EDINBURGH, UK

GUILLAUME LEGROS: UNIVERSITE PIERRE ET MARIE CURIE, PARIS, FRANCE

CHRISTIAN EIGENBROD: UNIVERSITY OF BREMEN (ZARM), BREMEN, GERMANY

NICKOLAY SMIRNOV: MOSCOW LOMONOSOV STATE UNIVERSITY, MOSCOW, RUSSIA

OSAMU FUJITA: HOKKAIDO UNIVERSITY, SAPPORO, JAPAN

SEBASTIEN ROUVREAU: BELISAMA R&D, TOULOUSE, FRANCE

GRUNDE JOMAAS: TECHNICAL UNIVERSITY OF DENMARK, KGS. L YNGBY, DENMARK

https://ntrs.nasa.gov/search.jsp?R=20130000677 2020-06-15T10:00:49+00:00Z

Spacecraft Fire Safety Demonstration

Project Objective:

• Advance spacecraft fire safety technologies identified as gaps by the Constellation Program and in the Exploration Technology Roadmaps

• Demonstrate performance of these technologies in a large-scale, low-gravity spacecraft fire safety test aboard an unmanned re-entry vehicle

- Demonstration of this operational concept could allow future experiments to investigate additional fire safety technologies and protocols

Experiment Objective:

Determine the fate of a large-scale microgravity fire 1. Spread rate, mass consumption, and heat

release

• Is there a limiting size in microgravity? 2. Confirm that low- and partial-g flammability

limits are less than those in normal gravity

• Are drop tower results correct?

Most U. S. agencies responsible for large transportation systems conduct full-scale fire tests to address gaps in fire safety knowledge and prove equipment and protocols.

FAA full scale aircraft test

Naval Research Laboratory Ex-USS Shadwell

Controlled burns of structures

Orbital Science's Cygnus ESA's ATV approaching ISS approaching the ISS

2

Implications of Fire Growth Rate

• Almost no information exists on large-scale fire growth in microgravity

• CO2 concentration approximately scales with mass of material consumed

• Safety-critical parameters such as temperature and pressure scale with mass consumed and rate of mass consumption

• Growth rate information is needed to make informed decisions on safety equipment and crew response

Pressure relief valve sizing Extinguisher size Consumables for cabin cleanup Crew response times (fight-or-flee decisions)

• Data will validate modeling of spacecraft fire response scenarios

500

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Non-survivable Fire

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Survivable Fire

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3

Experiment Justification

• NASA-STD-6001 describes the test methods used to qualify materials for use in space vehicles.

• The tests cover flammability, odor, off-gassing, and compatibility.

• The primary test to assess material flammability is Test 1: Upward Flame Propagation

Subs~ral& 'or tes1ing ot cO<aJtin QS ,

Typir;all spccimen -

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Test 1 Apparatus

• Materials "pass" this test if the flame self-extinguishes before it propagates 15 cm

• Maximum oxygen concentration (MOC) is defined as the highest O2 at which material passes Test 1

• Flammability limits determined by this test are strongly influenced by natural convection

• Drop tower data shows that flammability limits are lower in low- and partial­gravity!

• Do NASA's flammability standards result in higher flammability limits than actually found in low-gravity?

4

Low- and Partial-g Flammability Limits

• Tests were conducted at WSTF (normal-g) and GRC (Iow- and partial-g) to quantify changes in the flammability limit for Nomex, Mylar, and Ultem at low (with convective flow), Martian, and Lunar gravity levels.

• Data on right shows Oxygen Margin of Safety (negative means material burns at lower 02 compared to normal gravity!)

(OMOS = MOC)o_g - MOC)1_g)

Centrifuge drop rig being prepared for a drop in the Zero Gravity Facility

Dome

Experiment support plate

Control hardware and electronics

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o Zero Gravity Forccd Convect ion

Ultem Nomex

~ Flammability limit samples in the Spacecraft Fire Safety Demonstration Experiment will evaluate NASA-STD-6001 Test 1 in low-g and validate drop tower results.

5

Flow

Flow

Mission Concept

Load experiment into Cygnus PCM

Cygnus mounted in the shroud of the Antares vehicle Antares (Tau res 2) V launch

7

Mission Concept

Cygnus approaching ISS Unpack cargo, reload with trash

Proposed location of the SFS Demo experiment (back of vehicle)

Check-out SFS Demo experiment

8

SFS Demo Experiment Configuration

• Experiment remains on AFT wall but rotated to lie between the rails • Sample spacing requirements met • Length of flow chamber reduced from 48" to 44" • Camera enclosures facing M-01/M-02 bags on AFT wall

SFSD Expermenwith 44" Flow Chamber Displaces One M-01 CTe and One M-02 CTe

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Safety Considerations - Overpressure testing

Vacuum Faculty (VF)-13) 149.9 cm 10 360 cm high 6.35 m3 volume

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time, s from ignition start

Pressure trace for Single 12.5- by 100-cm sample ignited at the top. The fuel is 90 grade cotton cheese-cloth with a 4.92 mg/cm2 density.

12

Calculation initialization

• Calculations are initialized with a steady state flow generated by the fans at constant temperature following a classic strategy:

• Flow initialization

• Full multigrid initialization

• Few thousands iterations with first order solver

• Few thousands iterations with second order solver

• Flow modelling main parameters: • Energy equation turned on

• Turbulence model: Ke-RNG

• Air as ideal gas for density calculation

• sutherland model for viscosity

• Initial temperature: 300k

• Initial pressure: 1013 hPa

• All walls are adiabatic

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Calculation with heat release ATV configuration

• 1- ATV configuration after 1 minute of heat release • Pathlines • Velocity field • Temperature field

6.73e-01

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5389-01

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4.37e-01

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Pathlines Colored by Velocity Magnitude (m/s) (Time=6.0000e+01) Sep 06, 2012 ANSYS FLUENT 14.0 (3d, dp, pbns, rngke , transient)

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Sep 06 , 20 12 ANSYS FLUENT 1 • . 0 (3d. dp . pbns, rngke. transient)

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Sap 06 , 20 12 ANSYS FLUENT 1 • . 0 (3d. dp . pbns , rngke. transient)

Conclusions

• Microgravity fire behaviour remains poorly understood and a significant risk for spaceflight

• An experiment is underdevelopment that will provide the first real opportunity to examine this issue focussing on two objectives

• Flame Spread

• Material Flammability

• This experiment has been shown to be feasible on both ESA's ATV and Orbital Science's Cygnus vehicles with the Cygnus as the current base-line carrier.

• An international topical team has been formed to develop concepts for that experiment and work towards its implementation.

• Pressure Rise prediction

• Sample Material Selection

• This experiment would be a landmark for spacecraft fire safety with the data and subsequent analysis providing much needed verifications of spacecraft fire safety protocol for the crews of future exploration vehicles and habitats.

15