Steven F. Udvar-Hazy Center Planning

A Good Place For Our Air and Space Treasures

The National Air and Space Museum staff works hard to provide the best possible conditions for our irreplaceable and priceless national treasures. At the new Steven F. Udvar-Hazy Center, aviation and space artifacts will be displayed in a manner that preserves them for many future generations of visitors.

The preservation, or conservation, of any valuable object requires the careful control of its environment. This is a real challenge when the Aviation Hangar alone contains over 19 million cubic feet of space. To get technical:

Table 1 lists some of the factors that must be controlled along with the limits set by the Museum.

Table 1 – Environmental Parameters for Conservation

Lighting

The control of light intensity and wave length is particularly important. Ed McManus notes that too much light will fade artifacts or cause chemical changes. Too little light would make it difficult for visitors, and colors would not be truly reflected. Different limits have been established for different materials. For example, 20 footcandles is the maximum light level allowed for cotton, whereas 50 footcandles is the limit for glass and metal [Light Level Guidelines, National Air and Space Museum, Exhibits Division, Design Unit, October 1991]. If the ambient light levels are brighter than allowed, the artifacts must be given their own environments in display cases.

Frank Florentine, Exhibits Designer, National Air and Space Museum, tells us that lighting presents special problems. In the Aviation Hangar, very little daylight will be allowed to reach the artifacts. Daylight that does reach artifacts will be filtered to reduce ultraviolet energy, and it will be diffused by baffles. Therefore, the majority of lighting is electrical; the light levels are high enough to allow for comfortable viewing by visitors while low enough to provide a measure of protection to the artifacts.

The Aviation Hangar is huge, and light fixtures will be placed at various distances from the artifacts. Fixtures that might normally be used to light such a big commercial space would be so hot that they would interfere with the temperature control of the hangar. Therefore, ceramic metal-halide lights will be used. A 39-watt halide unit emits 2100 lumens, whereas a 50-watt halogen unit emits only 610 lumens, less than one third the light for a fourth more heat energy. ("Watts” indicates the amount of electricity used, which is turned into light and heat.)

The 20 footcandles of light will allow visitors to see artifacts very well. Also, the color spectrum of the lights is close to daylight (about 3000°K) – not red or yellow as with incandescent (2500-2000°K) (°K means degrees Kelvin, a measure of light color). Thus, artifacts appear in their true “outdoor” colors. Fisher, Marantz, and Stone of New York designed the lighting for the Center’s architect, Hellmuth, Obata + Kassabaum. The fixtures are being installed by MC Dean, the electrical subcontractor.

Frank explains that the placement of the light fixtures is very important, too. Hanging aircraft will be up-lighted so that they stand out against the high ceiling (the ceiling is designed with 90% reflectance to conserve light). Lights will be directed upward from waist-high barriers around artifacts as well as from the walls on both sides of the Aviation and Space Hangars. Downward lights will also be used.

Temperature, humidity, and pollution

Once the Museum and curators established the limits for temperature, humidity, and pollution as listed in Table 1, it was up to the building architects to design the air handling and conditioning systems to provide the correct atmosphere. Richard Powers, Vice President, Hellmuth, Obata + Kassabaum architects, gives us an engineer’s look at how this is being done.

After all the good research, planning, and design, hardware needs to be purchased and installed to give artifacts and visitors a controlled environment. In fact, 15.32% of the construction costs are for the mechanical system and 13.49% for the electrical system. The building contractor for the Udvar-Hazy Center, Hensel Phelps Construction Co, awarded the contract for heating, ventilating, and air conditioning systems (HVAC) to John J. Kirlin, Inc., the mechanical subcontractor. Linda Arseneault, a Steamfitter Foreman, was given the job of supervising the huge job. The systems installed by Kirlin workers must cool or heat, and humidify or dehumidify the air for the Center. The following describes the key parts of the system. Refer to the diagram below.



Central Utility Plant: The Central Utility Plant holds the key equipment to provide the correct environmental atmosphere for the artifacts and people. In the Plant are heaters, chillers, control equipment, electrical distribution equipment, and the like.

The Central Utility Plant was the first building completed because it must serve the rest of the Center. Photo by Mark Avino, NASM

Air handling: Outside the Aviation Hangar are box-car sized air handlers 60 ft X 25 ft X 20 ft. Air flowing through these air handlers is mixed with outside air, warmed or cooled, humidified or dehumidified, and filtered.

Sensors in the return ducts tell the units what adjustments are needed. The handlers also take in some outside air to keep the pressure in the hangar positive (air flows out through cracks, not in), and the percentage of carbon dioxide (CO2) does not rise due to the presence of visitors, thus reducing any “stuffy” feeling.

	Air handlers are located at the corners of the Aviation Hangar. The large supply and return ducts connect them to the Aviation Hangar's inside ducts. Photo courtesy of Dick Powers, HOK
	Each of the Aviation Hangar air handlers was shipped from the factory in six sections and assembled on site. Shown here is one of the largest sections. Photo courtesy of Dick Powers, HOK
	Not all air handlers are huge. Linda Arseneault, Steamfitter Foreman for John J. Kirlin, Inc., is shown with one of the 13 indoor air handlers (9 are in the public amenities area). More will be added for the restoration and artifact preparation areas when they are built. Photo by Bill Doole

Cooling. Chillers are the machines that condense and evaporate the refrigerant. Two 500-ton (a measure of capacity) centrifugal chillers are used to cool the refrigerant going to the heat exchangers in the air handlers. The Trane company chillers are specially built for the Smithsonian, according to the brass plate on each machine. Trane is also responsible for start-up of the system.

Photo by Smithsonian staff	Four chillers generate chilled water to cool the air flowing through the air handlers. One of the larger chillers, with a 760-ton cooling capacity, is shown being moved into the Central Utility Plant.
Photo courtesy of Dick Powers, HOK

The water cooled by the chillers is 30% propylene glycol and 70% water, a food-quality mixture that will not create an environmental hazard if it leaks. 30,000 gallons of this chemical mixture are transported from the Ashland Corp in Texas in 7 tanker trucks to fill the system. When in operation, a 55-gallon tank will automatically replenish the system.

Ice reduces energy use. Twenty-seven ice storage tanks are used to control energy costs. When air conditioning is needed, ice is made inside these tanks at night when electric power demand is less (and cheaper). As the ice melts during the day, the cold water is passed to the chillers. Of the 3000 tons of cooling capacity in the chillers, 600 tons can be provided by the melting ice, approximately 20% of a day’s cooling load.

Two screw chillers (compressors using large screws rather than centrifugal blowers) produce 27 deg F chilled water to make the ice.

Ice storage also uses the existing electrical generators when they would otherwise be underutilized, reducing the need for additional generating capacity.

In the winter, ice remains frozen in these tanks to avoid the stress of freeze-thaw cycles. Photo by Linda Arseneault, John J. Kirlin, Inc.

Heating. Two 400-hp and one 200-hp gas-fired steam boilers produce steam at a pressure of 50 pounds per square inch (psi). They have a combined heating capacity of 33 million BTU per hour. However, only one 400-hp boiler will be on line at a time, and the 200-hp boiler is a back-up.

	It was a tight fit, but the John J. Kirlin crew got this 400-hp boiler through the door of the Central Utility Plant. Photo by Linda Arseneault, John J. Kirlin, Inc.
	The boilers seen here have been set in place and the piping is being installed by the Kirlin staff. Photo courtesy of Dick Powers, HOK

Humidifying. The boilers also provide heat for the humidification system. The 50 psi steam is piped to a “clean steam” generator where soft water is turned into 20 psi of steam. In the air handler, this steam is sprayed into the air as needed to increase the humidity. Throughout the Center, humidity is kept the same so that humid air does not migrate from one area to another.

Air ducts. There can be no layering of air inside the hangars (hot air near the ceiling and cooler air near the floor), nor can there be drafts that would be uncomfortable to visitors and could make the suspended aircraft move. Hanging aircraft must have the same conditions as those on the floor. Dick Powers tells us that architects and engineers used a fluid dynamics simulator (“Computational Fluid Dynamics”) to try different configurations of air ducts and to confirm the final design. The result is a system of very large ducts (the largest return duct has a diameter of 3 meters (9.8 feet) with an area of 7 square meters (76 square feet)).

From the main supply ducts, vertical vents are mounted in each truss. Air stratification is also controlled by using a low temperature differential – air coming out of the vents is at nearly the same temperature as the surrounding air. The air flowing from the handlers to the building goes through ducting fabricated by United Sheet Metal.

	Large air ducts go to and from the air handlers. Photo courtesy of Dick Powers, HOK
	Return duct "T" fittings were fabricated in the sheet metal contractor's shop. The 110-inch (2.8 meter) diameter duct is shown next to a 6-foot ladder for size comparison. Photo courtesy of Dick Powers, HOK
	A Kirlin crew prepares an air duct for installation by joining the sections. Photo by Linda Arseneault, John J. Kirlin, Inc.
	Ducts (risers) for the Aviation Hangar are designed to evenly distribute heated and cooled air with a constant temperature. The ducts are curved to blend with the truss structures. Photo courtesy of Dick Powers, HOK
	The supply ducts do not look so huge on the walls of a hangar that is 103 feet high. SI#: 2002-17807 Photo by Carolyn Russo, NASM

Piping. All of these systems need a lot of pipe. There will be 12,200 feet of underground pipe and 50,000 feet of above ground pipe.

	Forty-foot pieces of pipe are welded into 120-foot sections before being lowered into the ground. Note that the pipe is on rollers to ease the work of the Kirlin welder. Photo by Linda Arseneault, John J. Kirlin, Inc.
	The 120-foot sections are gently lowered into trenches that go under the floor of the Aviation Hangar. Photo by Linda Arseneault, John J. Kirlin, Inc.
	The pipe utility trenches hold a variety of pipe: steam, electrical, communications, water, etc. Photo by Linda Arseneault, John J. Kirlin, Inc.
	Pipes must eventually come above ground. Shown here are pre-insulated Thermacore steam pipes. Above ground, the TBN company is responsible for pipe and ducting insulation. Photo by Linda Arseneault, John J. Kirlin, Inc.
	The steam or water flowing through the pipes must be controlled by valves and regulators. When all systems are installed the Seneca Balance company will use controls such as these to test and balance the system. Photo by Bill Doole

Pollution removal. Particulate filters in the air handlers remove about 85% of the non-gaseous material (e.g., dust and pollen) that is 0.3 microns in size or larger, and charcoal filters remove hydrocarbons such as the jet exhaust from airplanes operating at Dulles International Airport.

When the Restoration Hangar is built, many additional specialty air handlers will be needed to process the air to remove paint spray fumes, welding gases, cleaning fluid fumes, sanding dust, and other by-products of the restoration process.

Vibration

Any area with aircraft operations, such as at Dulles Airport, will have noise, which causes vibrations. In time, these vibrations could possibly weaken aircraft and spacecraft structures, particularly those that are somewhat delicate. The exhibit designers and conservators consider each artifact and provide mounting devices that minimize the effects from any vibration.

Insects and Pests

Most insects and pests are kept out by the air handling system, which controls and filters the air in the Center. If insects or pests are detected inside the hangars, integrated pest management actions will be taken.

A Good Place

The National Air and Space Museum’s conservators, exhibit designers, architects, and construction teams are taking extraordinary steps to insure that both our national air and space treasures and the visitors who are inspired by them will have the best possible environment.

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