U.S. rocket makers are refining a concept to dual-launch the next generation of Global Positioning System satellites, a move that could save $50 million per satellite compared to the traditional practice of dedicating a single booster to loft each spacecraft separately.
In the military space world, where some satellites can exceed $1 billion in cost, $50 million is not a lot of money. But the immense fiscal pressure being put on the Pentagon is compelling managers to consider pinching pennies wherever possible. This, combined with a solid record of performance from the United Launch Alliance's Atlas V and Delta IV vehicles, is driving officials at the Pentagon to consider taking the risk of stacking twosatellites atop a single booster. Satellite manufacturers note that the cost avoidance can add up—a notional constellation of 30 could save $1.5 billion, they say.
GPS III, being developed by, is the ideal platform on which to try the dual-launch concept. Unlike other Pentagon satellite programs, the U.S. Air Force is buying GPS IIIs in large enough numbers to justify the non-recurring engineering for the new hardware and software for a dual launch. Air Force officials are considering this approach with satellites 9 and 10, though developers at ULA and Lockheed Martin suggest they could be ready to start with satellites 5 and 6.
The team is studying how to safely encapsulate and eject two spacecraft from atop a single booster. Options include relying on the satellites' onboard propulsion or developing a secondary vehicle for the orbital transfer, says Tony Taliancich, a ULA official.
The least risky and most affordable solution to maneuver the satellites into operational orbits will ultimately be using onboard propulsion, rather than relying on a secondary vehicle, says Keoki Jackson, vice president of navigation systems for Lockheed Martin. “This approach would also help mitigate ongoing space debris concerns, as no secondary vehicle would need to be jettisoned in high-traffic orbital areas.”
Unlike earlier GPS satellites, GPS III will not be directly injected into its operational orbit. The inherent propulsion capabilities of the A2100 platform on which GPS III is being built will allow for it to self-maneuver into orbit. “No modification would be needed for the satellite's onboard propulsion,” Jackson says. “To enable dual launch and successfully propel two satellites into separate orbital slots, we will just need to develop dual-channel communications units for each satellite, which will allow the ground system to distinguish between the two satellites during launch and orbit insertion.”
Jackson characterizes this communication system work as “low-risk,” and preliminary estimates suggest the cost of this work can be recovered in the first dual-launch mission.
The team has begun design work on an Atlas V Dual Satellite System 5, which will feature a canister structure surrounding the bottom satellite. This will provide separate load paths for two spacecraft on a single booster. The dual-launch concept points to an Atlas V with a 5-meter (16-ft.) fairing and five strap-on solid rocket motors.
Though industry says the system can be ready in three years, the Air Force is taking a more conservative approach. One industry official suggests this is so ULA does not have an advantage over(SpaceX), which is still developing its Falcon family to compete with the Atlas V and Delta IV.
GPS is the most the most likely entry point for SpaceX into the Air Force market because of the satellite's size and projected launch frequency.
Though the dual-launch work being done today is focused on GPS III, Lockheed Martin officials say some lessons could be applied to other programs and “pay dividends not only on GPS, but for the entire Air Force for years to come.”
The A2100 bus also hosts the costly and sophisticated Advanced Extremely High Frequency protected, nuclear-hardened communications system, as well as the Space-Based Infrared System early missile-warning satellites. These two systems, however, are being built in far smaller quantities—four or five of them comprise a constellation versus 28-32 for GPS—and at greater cost. Lockheed Martin, eager to keep those programs alive after a decade of developmental problems and cost overruns, is sure to crunch the numbers and propose dual-launch options for them, though.
The savings achieved with this strategy is likely an interim step for the Air Force. Far greater efficiencies could be possible if industry can either mature reusable launch systems or shrink the size of satellites enough to reduce the need for large boosters.
Meanwhile, Lockheed is continuing development work on GPS III since winning the contract in 2008, a potentially long-term win that could put rivalout of the GPS business once its IIF satellite program wraps up. Lockheed shipped the propulsion core for the first operational spacecraft late last month to its Denver facility for integration with other satellite components. The first power-on event for GPS III satellite 1 is slated for next month, Jackson says.
In April, the pathfinder will be shipped to Cape Canaveral AFS, where operators will run it through the pre-launch process for practice. It is slated for launch availability in May 2014, with the second satellite expected about nine months later. Actual launch dates could vary if the life of in-orbit spacecraft surpasses expectations.
GPS III is being designed to a 15-year in-orbit life.