Homes Protected from Raging Forest Fires
Every year we hear about countless homes being destroyed by forest fires. Unfortunately, the public isn’t aware that our current level of technology can readily address this problem. I have been examining a concept that has intrigued me over the past decade and which I call a “fire shield”. This shield functions by completely enveloping a private home and protecting it against encroaching forest fires. We’re talking about protection against a blazing fire storm generating high speed winds and flames in excess of 100 MPH. The shield would be a flexible structure that easily inflates like a balloon (needing perhaps three people for a day to erect) and forms a protective hemispherical, shell-like dome over the home (Fig-1). The structure would be impervious to penetration by high speed flames and their intense radiant heat, thereby keeping the enveloped home safe, cooled and protected.
Each home would require a pre-fitted, customized buildup of a number of pre-built modular, balloon-like segments. They are manufactured and then assembled over the house only once, to get a customized tailored fit, then taken down and stored, and thereafter are ready to be deployed within a day’s advance notice of an encroaching forest fire.
The Fire-Shield would be a modular, portable, inflated dome like those used for indoor tennis, which is prepared and custom-fitted to be later erected within a day. While typical inflated domes have their entire inner volume pressurized, our Fire-Shield will only require pressurizing a small volume contained between its double-walled structure that forms the dome as shown in Fig-1. The surface of its outer material uses NASA's radiatively reflective, aluminized Mylar to ward off the intense radiant heat of a fire storm. In addition this surface gets protected against the 100 – 150 MPH fire-winds, which are ready to impinge upon it, by injecting a high speed film of air (just like gas-turbine blades) produced by portable blowers. The actual heat-shield contains multiple, redundant pockets of cells directing the flow of air to both film-cool its surface and protect the shield against direct flame contact. Each major modular segment would contain its own portable, gasoline powered wind generator to supply the airflow. Depending upon home-size, several of these modules would be easily connected using Velcro plus redundant snaps and safety-stays. The shield gets attached over chimney tops and to pre-installed, grounded cement-posts, plus strategic hooks about the outside of the house. Special, inflated pillows are also strategically placed (between the shield and the house exterior) to facilitate the formation of a hemispherical shield that envelopes and protects our home against a high speed fire-storm.
The Fire-Shield Design Concept
The concept for a fire shield went through a gestation period of several decades as my career in thermo/fluids evolved. It started with the design of jet engine turbine cooling to thermal control of satellites, and finally to designing radiant heat barriers for cryogenics. These activities enabled receiving a score of patents as well.
These activities inspired the concept for a rapidly deployable Fire-Shield to protect homes against a raging forest fire. The idea requires integrating several technologies ranging from inflatable commercial air domes to jet engine cooling to radiatively cooled spacecraft. Also included are flexible material coatings developed by NASA that radiatively reflects high temperature heat, making the deployable Fire-Shield a viable concept.
Two key design principles are employed to protect both the heat shield and the home it envelopes. The first is shown in Fig-2 and uses a high speed film of air (faster than the anticipated fire-storm flame speeds of 100 – 150 MPH) that is locally directed to blow over the shield’s surface, cooling it and protecting it just like the metal turbine blades of jet-engines. The temperature of speeding flames impinging upon a jet engine’s metallic turbine blades is hot enough to easily melt them, yet the blades are protected by using this film cooling technology. The same technology will protect the heat-shield from meltdown when high speed flames of 100+ MPH attempt to impinge upon its surface.
The second principle protects the shield against the intense radiant heat coming from a blazing forest fire where temperatures can exceed 2000 F. While this radiant heat does not physically touch the shield, as would a fire-storm’s flames, its presence is “felt” and is as deadly as the hot flames that would normally scrub over the shield without our film-cooling. We use a radiatively reflective, thermal coating barrier that repels this radiant heatload and protects the shield from melting. Such coatings were originally developed by NASA to protect satellites and spacecraft. The coating gets applied to the shield’s outer domed surface and will reflect better than 97% of all intensive radiant heatloads that are incident upon the dome’s surface. (Patent Pending; Original Concept Documented in 2006)