Archive for the ‘Microgravity Research’ Category

by: Jason A. Sutula

The (cliché?) saying, “It’s not what you know, it’s who you know,” comes to mind as I write this short blog post. Mostly because I have the good fortune to know Samarra Khaja. Besides being family and a friend of mine, she is a highly talented and creative individual. While having her husband and family over for a visit recently, she spent some time working with me on a new branding image for the blog. The final result is below. If anyone who reads this blog has a need for logo & branding work, illustration, or photography (and several other creative services), I hope you will consider contacting SK. You can check out her work at smarrakhaja.com.

And now, the reveal:

Logo low res

Feel free to chime in on the design in the comment section. If there is enough interest, maybe I will make up some t-shirts and give them away in a contest!

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by: Jason A. Sutula

In a previous post on the topic of fire in space, I discussed the 1997 fire incident aboard the Mir Space Station. The case study still resonates today and provides valuable lessons for both NASA and the private commercial space companies on what fire hazards can be expected and need to be defended against in both manned and unmanned spacecraft missions. The single most important lesson that the Mir incident taught us is that the process of a fire burning in space is not intuitive.

Gravity, the driving force for natural fluid flow on the earth, cannot exert its influence on people, objects, and even fire when they are in a spacecraft circling the globe. In free fall around the plant earth, hot gases do not rise, and cold gases do not fall. The effects of buoyancy as seen in earth-bound fires are removed, which results in drastic differences in the appearance and structure of flames.

Fortunately, research in these areas has continued over the past few decades. Several on-going research studies are currently being conducted independently as well as in conjunction with NASA and the International Space Station in efforts to more fundamentally understand the fire hazards in microgravity environments.

One study by McGrattan, Kashiwagi, Baum, and Olson (McGrattan et al., 1996) demonstrated some strange fire behavior in microgravity conditions. For the study, a thin cellulosic fuel was suspended in a combustion test rig designed for a 2.2 second drop tower. The 2.2 second drop tower provided of a short amount of simulated microgravity conditions while the fire was burning. Ignition occurred in the middle of the sample and the flame was allowed to spread both vertically “upward” and “downward” at the same time. As a further variable, the researchers forced an air flow across the fuel sample at various speeds. The results were very surprising. The researchers initially expected the flame to propagate more rapidly in the downstream direction of the flow of air (think of how a camp fire will flare up when you blow on the coals). Instead, the fire burned more readily in the upstream or “opposed” direction of the flow, and the downstream flame died out quickly.

McGrattan et al. formulated a two-dimensional, time-dependent combustion model using computational fluid dynamics to better understand the phenomenon. Their computational study demonstrated that the flame moving in the opposite direction to the flow created an “oxygen shadow” in relation to the flame moving in the same direction as the air flow. This resulted in the downstream flame extinguishing since the flame moving toward the flow had already consumed all of the available oxygen!

In the embedded YouTube video above, Dr. Sandra Olson of the NASA Glenn Research Center, presents actual footage of the flame front burning as it is dropped in the 2.2 second drop tower. The full video is geared toward a younger, more kid friendly audience, so if you want to skip ahead, the microgravity combustion video and discussion begins at 0:51.

More research and computational studies will need to be conducted by NASA and commercial space ventures to better understand all of the fire hazard risks associated with microgravity environments. Fortunately, there are pioneers in this field laying the groundwork for fire safety in the final frontier.

McGrattan, K.B., Kashiwagi, T., Baum. H.R., and Olson, S.L., “Effects of Ignition and Wind on the Transition to Flame Spread in a Microgravity Environment,” Combustion and Flame, 106: pp 377-391, 1996.

by: Jason A. Sutula

microg flame

I have been extremely fortunate to have had the opportunity to research the physics of fire over widely ranging projects throughout my career. When I get the chance to discuss some of these projects with friends, colleagues, and future engineers, scientists, and investigators, the ones that tend to stand out the most involve my research in the realm of microgravity combustion. Microgravity combustion can be more simply described as how a fire will burn when it is in “Space”. There have been many motivations for this type of research over the years, and many government agencies have provided funding to study combustion in this fashion.

Besides attempting to gain fundamental understanding of the combustion phenomenon, the main motivation to study fire in space is safety. One particular space-related fire safety story that captured my imagination (and was the main motivation for both my Master’s Thesis and Ph.D. Dissertation) is the story of the 1997 fire aboard the Mir space station.

In February of that year, three replacement crew members arrived at the Mir via Soyuz spacecraft to continue joint Russian-American experiments that covered a broad range of scientific inquiry. On arrival, one crew member activated an oxygen generating device designed to boost the concentration of oxygen aboard the station to account for the increased number of people. Immediately after the activation of the device, the holding canister ruptured and began to burn uncontrollably. The fire was described as a “blowtorch-like, white conical flame” that was roughly two feet in length. The crew feared that the fire would impinge on the opposite wall of the Kvant module and threaten a breach and subsequent depressurization of the capsule. Additionally, the fire was situated in a location that cut off the escape route for three of the crew to the Soyuz escape vehicle. In under a minute, the visibility in the space station was reduced to less than a few feet due to the smoke given off by the fire. Some of the crew reported that they could not see their hands in front of their faces. The atmospheric temperature within the space station also began to rise to upward of 100 °F. With breathing becoming difficult, the crew donned compressed air gas masks shortly after the fire began, and attempted to fight the fire and limit its spread. Several foam/water extinguishers were discharged by the crew, but were observed to be ineffective against the flames. Eventually, the fire subsided on its own, most likely from exhausting its fuel supply.

After extinguishment of the fire, the air scrubbing capability of the Mir was put to the test. The crew was able to remove the life saving compressed air gas masks in a few hours, but then had to wear particulate filter masks for several days after the fire incident until the remaining combustion particulates were filtered down to a reasonable exposure level.

This particular fire incident was extremely valuable for pointing out several fire safety concerns with space vehicles, space structures, and manned space exploration. First, in space-based vehicles and structures, there is no easy way to “evacuate” from the vehicle or structure. On earth, if an individual is involved in a structure fire, the easiest method of preserving life and preventing injury is designing the structure with fire notification (a fire alarm system) and an adequate means of escape (such as: an appropriate number of exits from the building, lighted exit signs, posted escape pathways to the nearest exit in hotel rooms, etc.). In the vacuum of space, evacuation to the exterior of the vehicle or structure will be a much more problematic means of fire safety.

Second, extinguishers and extinguishing methods that are used on earth are not as effective in space vehicles and space structures with microgravity conditions. Buoyancy, which drives heat “upward” due to density differences, and the presence of a gravitation field on the surface of the earth are both non-existent when a fire occurs in space. Fire does not burn “up” in these environments. Instead, a fire will follow any local ventilation currents and exist where sufficient oxygen and fuel are available. When extinguishing attempts are made in a microgravity environment, the momentum from the jet of an extinguishing agent (imagine using a kitchen fire extinguisher that is sprayed at a fire) can “push” the flame out of the way. The result may be that the extinguishing agent has completely missed the fire and the fire was able to spread to other mission critical systems.

Third, the inherent flammability of a particular material should be addressed before it is used in a space vehicle or space structure. If the flammability of a material is deemed to be too great, then limiting or not allowing that material on board should decrease the overall risk for a particular space vehicle or space structure. NASA, along with other researchers and groups, has performed work on this very topic to lay the fire safety groundwork for future extraterrestrial missions.

While these three concerns for fire safety in microgravity are a good start, they are certainly not comprehensive for all of the issues surrounding the management of fire in these challenging environments. With amazing and exciting progress being made almost every day by companies such as Scaled Composites, Virgin Galactic, and SpaceX in the fields of commercial space exploration, tourism, and payload delivery, it is only a matter of time before more and more people gain access to and utilize space vehicles and space structures for work and pleasure. Safety and, in particular, fire safety for these individuals must be a top priority.