The largest aircraft ever built will be based at a 103,256-square-foot hangar completed earlier this year at the Mojave Air & Space Port in Mojave, Calif. Burt Rutan, a legend in the aviation field, designed the twin-fuselage behemoth that will serve as the air-launch carrier for multi-stage rockets on commercial aerospace missions. Paul Allen, the co-founder of Microsoft and an aerospace enthusiast, has financed Stratolaunch Systems as a startup venture with headquarters in Huntsville, Ala. The company could someday dominate the commercial aerospace industry, just as Allen and Bill Gates achieved during the meteoric growth of Microsoft.
Wallace & Smith General Contractors, based in Bakersfield, Calif., completed the hangar earlier in 2013, and a neighboring 88,000-square-foot manufacturing and assembly facility in 2012, where the unique aircraft is being built from hybrid composites combined with major sections from two retired Boeing 747-400s that will be stripped of their engines, landing gear and electronics for use in the unique plane.
The assembly building and the following larger hangar were awarded as separate design-build contracts. CBC Steel Buildings, a division of Nucor, based in Lathrop, Calif., supplied the custom-engineered and fabricated structural framing, standing seam metal roof and metal wall panel systems.
CBC builder earns project referral
“We had built several projects at the Mojave airport where we earned a solid reputation for quality and performance,” says Paul Cooper, a vice president with Wallace & Smith General Contractors, Bakersfield, Calif. “In 2006, [Mojave-based] Scaled Composites, now part of Northrop Grumman [Corp., Falls Church, Va.], was referred to us as a reliable contractor to build two facilities that included the earlier building to manufacture this aircraft.”
“Conceptual discussions began in 2006, but were shelved in 2009 just prior to obtaining permits,” Cooper reflects. “The owner came back to us in June 2011 and had us bring everything back on line in a fast-track schedule that enabled us to start construction on December 15 of that year. We had an excellent design-build team and CBC really supported us in refining the engineering and meeting delivery schedules. This enabled us to complete the hangar $500,000 under budget and two months ahead of an already challenging schedule without lost-time injuries.”
“The savings stayed with Stratolaunch Systems,” Cooper notes.
The two contracts were awarded separately and involved the same California-based project team led by Wallace
& Smith. On the design side, the team included Engle & Co. Engineers, Bakersfield, which served as engineer of record. Teter Architects & Engineers, Fresno, Calif., were the project architects. B.D. Compton, Santa Rosa, Calif., provided the steel erection for the 88 truckloads of heavy-steel trusses, roof and wall cladding systems that were hauled 300 miles at night under police escorts to the project site from the CBC plant in Lathrop.
The metal building manufacturer’s building information modeling
(BIM) system was a valuable tool for interacting throughout the coordinated design development, fabrication, delivery and erection sequence for the 1,500 tons of fabricated steel components.
Large parts of the story
The building is configured as an inverted-T footprint with the 148- by 462-foot dimension on the larger entry side established by the aircraft’s 385-foot wingspan. A contiguous 135- by 212-foot extension at one side accommodates the tail of the twin-bodied aircraft when parked inside the cavernous hangar.
The CBC MS-24 standing seam metal roof system extends from the 57-foot eave height in a double-slope condition of 2 1/4 inches on 12 inches that steps to a 1/2-inch on 12 inches double slope 30 feet below the 100-foot-high ridge. The space that receives the twin tails of the aircraft has a uniform 1-inch in 12 inches slope from the 66-foot eave to the 72-foot-high ridgeline.
Baymarr Constructors, Bakersfield, served as the concrete subcontractor for the foundations and flatwork. The foundations are 20 feet wide, 7 feet deep and 56 feet long, with 300 cubic yard of concrete poured for each of the main footings. The floor construction has varied depth sections from 15 inches at center to 9 inches at each side to 6 inches at the outer wall lines. The floor’s varied plane-and different section thicknesses-are necessary to carry the loads from the 1.3-millionpound aircraft. Each section slopes slightly toward cast-in-place trench drains to capture any release from the dual fire protection systems.
The hangar’s wall system consists of 12 18-foot-wide truss columns with I-beam diagonal bracing that create six frame lines. The rafter trusses were fabricated as 40- to 50-foot-long by 14- to 17-foot-wide bolted sections to create the roof support assembly. This fully rigid structural skeleton was engineered for a 100-mph wind load.
The overhead door ranks as the largest supplied by Megadoor, Peachtree City, Ga., on a civilian hangar in North America. It is skinned with a translucent PVC-coated polyester fabric with UV inhibitors and fire retardants that admit 10 percent of the ambient daylight into the interior. An unusual feature are the four 6-foot diameter exhaust ventilation fans integrated into the solid bottom section of two of the individually operator door sections. The tight seals of the Megadoor units can resist the notorious windblown desert dust known for infiltrating conventional bottom-rolling doors and had been proven to minimize the infiltration on two previous installations at the airport.
The wall and roof trusses, versus the customary welded three-plate columns and beams in the metal building systems industry, are more akin to a conventional steel structure and underscore the custom fabrication capabilities of CBC Steel Buildings, notes Brian Compton, the head of the erection company that operates in five states.
“This was certainly not the typical steel supplied by a metal building manufacturer that I’ve seen so many times in my 50 years in the erection business,” Compton emphasizes. “This also was our first experience involving BIM, and it proved invaluable during live discussions about details with everyone involved with the job. BIM really improved communications and made it easy to reference details and resolve questions and procedures. With our first experience with BIM, I’d say it is clearly the way to go on large or structurally complex projects.”
The adequately sized site eliminated the need for hot picks from the trailer loads of steel deliveries that were staged and erected from the ground using three mobile cranes. The wall truss columns were set and two opposing sections of roof trusses then lifted and joined into place to create one frame line per day, Compton says. His crew of 16 erectors finished cladding the building with the standing seam metal roof and metal wall panel systems in three months. At peak activity, the project had 145 workers in various trades and activities on the jobsite.
Evaporative coolers were specified to control the hangar environment at 80 F. The Elaminator insulation system by Owens Corning, Toledo, Ohio, achieved the R-19 thermal barrier in the roof, while R-13 was specified for the single-skin metal wall system assemblies. The lighting is primarily high-bay metal halide in the hangar space and a T-5 fluorescent system in the office area.
A record aircraft in the making
The wingspan for the Stratolaunch Systems aircraft is 385 feet, which is greater than the infamous H-4 Hercules aircraft produced in the late 1940s that became referred to as ‘The Spruce Goose.’
The air-launch concept for multi-stage rockets is envisioned as more efficient than static pads for vertical launches of multi-stage booster rockets that were the mainstay of the original Space Race. The Mojave Air & Space Port presents a big presence in what is steadily evolving into the epicenter for the Commercial Space Race. The facility was originally a U.S. Marine Corps fighter base during World War II and is undergoing aggressive redevelopment with an emphasis on marketing sites to aerospace companies and for open-air storage of retired commercial aircraft.
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Jim Ladesich has more than 30 years experience writing about the construction industry as a free lance writer and marketing communications consultant. He earned a BS in Journalism at the University of Kansas, where he also pursued graduate studies. He resides in a suburb of Kansas City.
Vital Stats
Systems Hangar at the Mojave Air & Space Port, Mojave, Calif.
General contractor: Wallace & Smith General Contractors, Bakersfield, Calif.
Project architect: Teter Architects & Engineers, Fresno, Calif.
Building erector: B.D. Compton, Santa Rosa, Calif.
Concrete contractor: Baymarr Constructors, Bakersfield
Engineer of record: Engle & Co. Engineers, Bakersfield
Hangar door: Megadoor, Peachtree City, Ga., www.megadoor.com Insulation: Owens Corning, Toledo, Ohio, www.owenscorning.com
Metal building system: CBC Steel Buildings, Lathrop, Calif., www.cbcsteelbuildings.com
