Speed, precision and a ‘Yes, we can’ attitude evolves into a sound barrier-busting project.
By Greg Snapper
In the New Mexico desert 100 miles north of El Paso, Texas, wedged between the San Andreas and Sacramento mountains, a high-speed military test track grows longer and time trials get faster with every precast concrete section that’s installed.
So far, 120 precast sections have been transported to Holloman Air Force Base in New Mexico to provide guideway beams for a magnetically levitated test track. The project is commonly known as the MagLev Upgrade, and the U.S. Air Force’s 46th Test Group is building this military track for weapons systems testing that uses a rocket-mounted sled designed to reach Mach 10. The Air Force foresees the project as a five-mile test track running alongside its existing 10-mile test track, which currently holds the world record as the longest (almost 10 miles) and fastest (6,453 mph) test track. Both tracks run parallel and serve the same basic purpose, but the MagLev’s track will provide a more realistic, low-vibration environment.
David Minto, technical director for the Holloman High Speed Test Track, said the track is bound to raise some eyebrows. “I’m sure for Precast Solutions, this is going to be unusual.” Minto is right. What’s more impressive is that it’s a first for the precast concrete industry.
A need for Mach speed
In early 2004, San Diego-based high-technology systems developer, General Atomics, approached precast manufacturer San Diego Precast Concrete Inc. to cast 150 specialized precast rail units for the Air Force. But before the project mix designs were conceptualized, before specialized stainless steel fiber reinforcement was thrown in the mix, and even before the project was dubbed MagLev, the bottom line had to be drawn.
“The track has been here since 1950, and it’s about a 10-mile-long, dual-rail, rocket sled test track,” Minto said. Forty-two years after the first high speed weapons systems testing began on this Holloman track, Minto and a team of military personnel and civilians working in the Test Group determined that testing could be done with a magnetically levitated rocket sled – and could accomplish more. Minto just happened to mention the idea to a visiting congressman, and the next thing his team knew, they had funding for what is now called the MagLev Upgrade.
“Suddenly we had $5 million to start developing the MagLev track and sled system,” Minto said. “We hadn’t even finished the feasibility study yet.”
‘Yes, we can.’
The faith of a congressman and a military/civilian engineering team fueled the first leg of MagLev’s journey, but more than a decade after its birth, the track is still in its infancy.
“We’re here 13 years later and we’re still working on it,” Minto said. To date, only 5 percent of the track is complete, but with project leaders such as San Diego Precast and General Atomics on the job, confidence in finishing the project has grown.
Gordon Pettis, project manager for San Diego Precast, said teamwork was key to MagLev’s success. “I think you need to have a specific team set up for this type of customer. Your quality control team has to maintain and test on a daily basis,” Pettis said. To ensure the quality control of the precast concrete rail beams, San Diego Precast followed a detailed production/curing process and voluntarily created fail-safe procedures. “You can’t afford to lose one piece,” Pettis said.
Extruded copper plates, encased in stainless steel, line the inner channel of the precast units. Due to the electromagnetic requirements, General Atomics replaced conventional steel reinforcing bars with steel fibers in the mix design. This creates a three-dimensional load resistance system throughout the units, allowing the MagLev sled, which rests atop the units, to eventually operate at supersonic speeds close to Mach 10. Standard steel reinforcement would otherwise interfere with the electromagnetics, which is the driving force of MagLev.
Manufacturing these particular units, which measure 13 feet 4 inches long with a 5-foot-wide base and stand 37 inches tall, involves a lengthy process from start to finish. The units are set up and poured in one day. Non-magnetic stainless steel fibers are used as reinforcement in the top portion of the unit (near the sled’s superconducting magnets), and carbon steel fibers are used in the bottom portion. Following the pour, the units rest in the mold for two days followed by a five-day water cure.
The units are moved to a preshipment staging area where they are cleaned and stenciled, and protective dunnage is attached. Finally, the units are shipped to New Mexico for installation at Holloman.
This process may seem routine, but the details involved show that it is anything but routine. For example, quality control is vital and highly prescriptive. A seven-day compressive strength test is required along with a seven-day flexural strength test. Both compressive and flexural tests are repeated at 28 days. Compressive strengths average 12,500 psi and flexural strength average is between 2,800 and 3,000 psi, satisfying General Atomics’ strict requirements. Both are highly ambitious requirements, but the mix and manufactured units have held up.
“ said it wasn’t possible,” project manager Pettis said. “But fortunately for us, our company motto is ‘Yes, we can.’”
Testing weapons systems components
The Air Force uses MagLev to test vital weapons systems components in a high-speed environment. Everything from heat-seeking devices to sensors and warheads will be mounted atop the MagLev sled and sent speeding down the test track. A failed heat-seeking sensor on the nose of a ballistic missile won’t get the weapon to its target – and for that reason, among many other scenarios just like it, the MagLev project is crucial for weapons systems testing. Minto said a ground-based test facility is ideal for the type of weapons testing they conduct.
“The United States has fielded missile defense system sites in Alaska and California to intercept ICBMs entering the country,” Minto said. “The best way to test U.S. warhead components is on the ground. We’re trying to simulate the dynamics of these missile engagements.”
The quarter-mile MagLev track being completed this spring has some limited test capability, but hypersonic weapons systems testing cannot be accomplished until the track reaches its desired length of five miles. That completion date is still unknown as it is based on incremental, government funding. It is not certain that San Diego Precast and General Atomics will even complete the USAF’s project as both of their Air Force contracts end after the first phase is complete, but both parties expressed a desire to extend their business agreements. San Diego Precast and General Atomics may not have a stake in the project’s future, but talks between the two have revealed future projects between the two are a sure bet.
Project Name: MagLev (Holloman MagLev Upgrade)
Owner: U.S. Air Force, Holloman Air Force Base, N.M.
Contractor/Engineer: General Atomics Co., San Diego
Precast Manufacturer: San Diego Precast Concrete Inc., San Diego*
* San Diego Precast Concrete Inc. is a certified plant under the NPCA plant certification program.