Concurrent Flame Spread Over Two-Sided Thick PMMA Slabs in Microgravity


Spacecraft fire safety is an important consideration when designing future exploration missions. Concurrent flow flame spread experiments were carried out aboard the Cygnus spacecraft while in orbit to address current knowledge gaps related to solid fuel combustion in microgravity. The experiments used PMMA (polymethylmethacrylate) samples that were 50 mm wide and 290 mm long with two variations—one sample was a 10 mm thick flat slab, while the other was a 10 mm thick flat sample that had a 4 mm thick grooved center section. The thickness variation had a major impact on the flame shape, and the grooved sample developed a deep inverted-V shaped notch as the thin center section burned through. This notch enhanced heat transfer from the flame to the solid through an effectively wider flame base, which is the part of the flame with the highest temperature. Unlike in normal gravity (and also likely in partial gravity), where buoyant flow promotes acceleratory upward flame growth, the microgravity flames reached a steady size (limiting length) for a fixed forced convective flow in agreement with theory (i.e. there is a zero net heat flux at the flame tip). The limiting length implies that the spread rate of the flame will be controlled by the regression rate (burnout rate) of the material because the flames remains anchored to the upstream end of the fuel samples. This is a significant finding for spacecraft fire safety, and makes the probability of flashover in a spacecraft unlikely as the flame size will be small for low convective ventilation flow environments typical in spacecraft. On the other hand, long-burning flames in small vehicles will generate significant quantities of fuel vapor that may reach the lean flammability limit and cause a backdraft. The rapid extinction of the flame when the flow was turned off also supports the existing fire mitigation strategy on the ISS to deactivate the ventilation system in the event of fire alarm. These findings can be applied to improve the safety of future space exploration missions.

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  1. 1.

    Pedley MD (2014) JSC 29353B, Flammability configuration analysis for spacecraft applications

  2. 2.

    ECSS 5 (2010) ECSS-Q-ST-70-21-C, ESA requirements and standards division.

  3. 3.

    ISO (2008) ISO 14624-1A Space systems—safety and compatibility of materials—part 1: determination of upward flammability of materials

  4. 4.

    NASA-STD-6001B (2016) Flammability, offgassing and compatibility requirements and test procedures, NASA

  5. 5.

    Jomaas G, Torero JL, Eigenbrod C, Niehaus J, Olson SL, Ferkul PV, Legros G, Fernandez-Pello AC, Cowlard AJ, Rouvreau S, Smirnov N (2015) Fire safety in space–beyond flammability testing of small samples. Acta Astronautica 109: 208–216

  6. 6.

    Altenkirch RA, Tang L, Sacksteder K, Bhattacharjee S, Delichatsios MA (1998) Inherently unsteady flame spread to extinction over thick fuels in microgravity. Proc Combust Inst 27(2): 2515–2524

  7. 7.

    Ferkul P, Sacksteder K, Greenberg P, Dietrich D, Ross H, Tien J, Altenkirch R, Tang L, Bundy M, Delichatsios M (1999) Combustion experiments on the Mir space station. In: 37th aerospace sciences meeting and exhibit, p 439. AIAA-99-0439.

  8. 8.

    Sanchez-Tarifa C, Lazaro B (2001) Experiments conducted on combustion of a solid at microgravity in the Texus-38 sounding rocket. Results and conclusions. Microgravity Res Appl Phys Sci Biotechnol 454: 267.

  9. 9.

    Olson SL, Hegde U, Bhattacharjee S, Deering JL, Tang L, Altenkirch RA (2004) Sounding rocket microgravity experiments elucidating diffusive and radiative transport effects on flame spread over thermally thick solids. Combust Sci Technol 176(4): 557–584

  10. 10.

    Ivanov AV, Balashov YV, Andreeva TV, Melikhov AS (1999) Experimental verification of material flammability in space. NASA/CR—1999-209405

  11. 11.

    Olson SL, Ferkul PV (2017) Microgravity flammability boundary for PMMA rods in axial stagnation flow: experimental results and energy balance analyses. Combust Flame 180: 217–229

  12. 12.

    Meyer F, Schwenteck T, Ruhe M, Bihn P, Freier A, Eigenbrod C (2017a) Experimental findings on flame propagation along PMMA samples in reduced gravity on REXUS 20 (UB-FIRE). In: 23rd ESA PAC symposium. ESA. Visby, ESA, p 8

  13. 13.

    Meyer F, Schwenteck T, Ruhe M, Bihn P, Freier A, Eigenbrod C (2017b) UB-FIRE experiment results on upward flame propagation along cylindrical PMMA samples in reduced gravity. In: 47th ICES. Charleston, SC, p 11

  14. 14.

    Markstein GH, De Ris J (1973) Upward fire spread over textiles. In: Symposium (International) on combustion, vol. 14, no. 1, pp 1085–1097.

  15. 15.

    Urban DL, Ferkul P, Olson S, Ruff GA, T’ien JS, Liao Y-TL, Fernandez-Pello AC, Torero JL, Legros G, Eigenbrod C, Smirnov N, Fujita O, Rouvreau S, Toth B, Jomaas G (2019) Flame spread: effects of microgravity and scale. Comb Flame 199: 168-182.

  16. 16.

    Fernandez-Pello AC, Hirano T (1983) Controlling mechanisms of flame spread. Combust Sci Technol 32(1–4): 1-31

  17. 17.

    Loh H-T, Fernandez-Pello AC (1985) A study of the controlling mechanisms of flow assisted flame spread. In: Symposium (International) on combustion, vol 20, no 1, pp 1575–1582

  18. 18.

    Chao YH, Fernandez-Pello AC (1993) Flame spread in a vitiated concurrent flow. ASME-Publications-Htd 199: 135

  19. 19.

    Delichatsios MA, Altenkirch RA, Bundy MF, Bhattacharjee S, Tang L, Sacksteder K (2000) Creeping flame spread along fuel cylinders in forced and natural flows and microgravity. Proc Combust Inst 28(2): 2835–2842

  20. 20.

    Di Blasi C, Crescitelli S, Russo G (1988) Near limit flame spread over thick fuels in a concurrent forced flow. Combust Flame 72(2): 205–215

  21. 21.

    Fernandez-Pello C, Mao C-P (1981) A unified analysis of concurrent modes of flame spread. Combust Sci Technol 26(3–4): 147–155

  22. 22.

    Tseng Y-T, T’ien JS (2010) Limiting length, steady spread, and non-growing flames in concurrent flow over solids. J Heat Transf 132(9): 0912011–9912011.

  23. 23.

    Raghavan V, Rangwala AS, Torero JL (2009) Laminar flame propagation on a horizontal fuel surface: verification of classical Emmons solution. Combust Theor Model 13(1): 121–141

  24. 24.

    Smirnov EM, Ivanov NG, Telnov DS, Son CH (2006) CFD modelling of cabin air ventilation in the international space station: a comparison of RANS and LES data with test measurements for the columbus module. Int J Vent 5(2): 219–227

  25. 25.

    Eigenbrod C, Hauschildt J, Meyer F, Urban DL, Ruff GA, Olson SL, Ferkul P, Jomaas G, Toth B (2017) Experimental results on the effect of surface structures on the flame propagation velocity of PMMA in microgravity. In: 47th international conference on environmental systems. ICES 2017-67, Charleston, SC

  26. 26.

    Würzburg N (2015) Experiments on the vertical flame propagation along surface-structured PMMA-samples; influence of sample thickness. Universität Bremen, B.Sc., Universität Bremen, pp 1–60

  27. 27.

    Thomsen M, Fernandez-Pello C, Ruff GA, Urban DL (2019) Buoyancy effects on concurrent flame spread over thick PMMA. Combust Flame 199: 279–291

  28. 28.

    Ferkul P, Olson S, Urban DL, Ruff GA, Easton J, T’ien JS, Liao Y-TT, Fernandez-Pello AC, Torero JL, Eigenbrod C, Legros G, Smirnov N, Fujita O, Rouvreau S, Toth B, Jomaas G (2017) Results of large-scale spacecraft flammability tests. In: 47th international conference on environmental systems, Charleston, SC

  29. 29.

    Kashiwagi T, McGrattan KB, Olson SL, Fujita O, Kikuchi M, Ito K (1996) Effects of slow wind on localized radiative ignition and transition to flame spread in microgravity. In: Symposium (International) on combustion, vol 26, no 1, pp 1345–1352

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The support of the NASA Advanced Exploration Systems Division provided the finances that enabled the Spacecraft Fire Safety Demonstration Project and the Saffire experiments. The authors appreciate the support of Orbital ATK for the integration and operation of the Saffire experiment in the Cygnus vehicle. The support from the topical team (ESTEC contract number 4000103397) on fire safety in space is also appreciated. In addition, the authors acknowledge the various space and research agencies that have supported the topical team, including but not limited to JAXA, ESA, RSA, CNES, DLR, the Russian Academy of Sciences and NASA.

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Correspondence to Sandra L. Olson.

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Olson, S.L., Urban, D.L., Ruff, G.A. et al. Concurrent Flame Spread Over Two-Sided Thick PMMA Slabs in Microgravity. Fire Technol 56, 49–69 (2020).

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  • Concurrent flame spread
  • Microgravity
  • PMMA
  • Thermally thick