High-tech space facility benefits from low-location lighting, using passive photo luminescent paints from MSS
Protruding seat studs in full-size mockups of Space Shuttle Crew Compartment Trainers 'highlighted', to minimize personal injury risks to astronauts and others.
Photoluminescent paint from Norway's Metal Safe Sign International (MSSI) is a passive, non-electrical photoluminescent product that is widely used for location marking and wayfinding safety purposes in many different industrial, maritime, aviation and public transport environments. It is now also being used by Houston, Texas-based Johnson Engineering for a very unusual space-related 'mission'!
Johnson Engineering is a subsidiary company of Houston-headquartered SPACEHAB, Inc.. It offers and provides specialized, high-end engineering and operation support to the group's diverse space research and logistics services, including astronaut training operations and high-tech facility engineering design and production.
The company manages NASA's unique Space Vehicle Mockup Facility (SVMF) building at the Johnson Space Center. This facility houses full-size mockups of the International Space Station and the Space Shuttle, including shuttle training modules comprised of a Crew Compartment Trainer (CCT), a Full Fuselage Trainer (FFT), and the second Crew Compartment Trainer (CCTII).
Seats for the astronauts are located on the shuttle's mid deck and flight deck (FFT, CCT and CCTII). During on-orbit operations the seats are removed from their floor studs, folded and stowed out of the way. This leaves the one and three-eighths inches (1 3/8") high seat studs exposed and protruding from the floor, which is not a problem during live flights as astronauts are floating in space above!
But during ground training in the full-size CCT (Crew Compartment) mockups, these studs are 'capped' with 1¾"-high red (denoting a non-flight item) plastics covers. They represent a potential hazard and could cause a person to trip, fall, twist or break an ankle or worse. Because a large number of people use the SVMF building - including trainee astronauts, instructors, on-site employees and occasional visitors - their safety is of considerable concern to the facility owners and operators.
In a low-light situation the probability of someone tripping over the 'capped' seat studs is increased significantly. If a power blackout occurs, for example, emergency lighting in the building fails to provide adequate lighting inside the trainer modules. Main building illumination is also substantially reduced, and all external light sources are blocked from entering the facility, when night exercises are conducted.
In this situation the building is like a gigantic darkroom, to simulate the darkness of space conditions, enabling crew members to train with low light cameras and depth perception while using the space vehicle's docking lights.
Experiments with several hazard marking alternatives were conducted, including depressions in the compartment floor, directional arrows to point and illuminate the way to safety, and photoluminescent tape around the studs. The consensus of opinion from instructors, safety officers and management was that the most effective option was to focus attention on the studs by illuminating them, to help wayfinding when exiting the trainer, as well as enhancing awareness of the hazard in all low light situations.
Rather than use 'glow in the dark' tape, which technicians disliked partly because it was easily damaged/displaced by shoe and boot 'scuffing' (see photograph provided), Johnson Engineering selected photoluminescent paint from Metal Safe Sign International for this 'space age' application. The paint is a heavy-duty product using MSSI's non-radioactive Strontium Aluminate (SA) pigment MSS-SA-III GY.
"The paint will be an elegant solution to satisfy safety and the technicians while providing a means to illuminate possible tripping hazards in the trainers," states Mr Clayton Hamm, Johnson Engineering's Shuttle Lead, SVMF - Integration Engineering Team.
While it is recognized that Strontium Aluminate-based photoluminescent safety signage systems take marginally longer to 'charge' than Zinc Sulfide (ZSu) systems, SA signs and hazard warnings 'store' significantly more light, making their much longer and stronger illumination output more effective where ambient light levels are low.
When the photoluminescent paint is applied at 115 microns dry film thickness (dft), and exposed to a light source for ten (10) minutes at 1,000 Lux (DIN 67510-part 1-1992), the after-glow strength substantially exceeds the luminescent effect requirements of IMO Res. A 752/18 (a minimum of 15 micro candela (mcd) for 600 seconds/10 minutes, and not less than two (2) mcd for the next hour). The paint installed at the Shuttle trainer deliver 55.4 mcd at the 10-minute mark, progressively reducing to 8.7 mcd after one hour. Equally impressive after-glow strengths are recorded when the photoluminescent paint at 115 microns dft is exposed to light source charges of 15 and 25 Lux for one hour, with even better performance being provided when the paint is applied in a thicker coat (180 microns dft recommended by MSSI). (Please note: These measurements are from the old version of Metal Safe Sign's photoluminescent paints. The company now offers much improved and better paints).
Established in 1996, Metal Safe Sign International is a leading innovator in the design, production and application of high-performance Strontium Aluminate pigments planned to provide improved 'passive' (non-electrical) safety and emergency wayfinding systems. Its extensive range of signage products is already used in many industrial locations, offices and public authority buildings, hotels, ships, offshore installations, railway, road and metro/subway tunnels, and at many other sites.
"The Space Shuttle requirement is a new
and very interesting application for our photoluminescent paints," reports Mr Arve Heggem, MSSI's
Managing Director. "Maybe the often heard expression of 'looking good Houston' will
become 'see the studs clearly' when the CCT modules are in future use!"
Metal Safe Sign International
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Mr. Arve Heggem