For the tenth time in its history, United Launch Alliance (ULA) will fly the most powerful member of its Atlas V fleet at 5:44 a.m. EDT Thursday, 8 August, when a 551 booster—boasting a 17.7-foot-diameter (5-meter) payload fairing, five strap-on solid-fueled rockets and a single-engine Centaur upper stage—rises from Space Launch Complex (SLC)-41 at Cape Canaveral Air Force Station, Fla.
Previously labeled “the bruiser” by ULA CEO Tory Bruno, the 551 will carry the fifth Advanced Extremely High Frequency (AEHF-5) military communications satellite. Built by Lockheed Martin, this satellite will join its four cousins, launched between August 2010 and last October, in providing fast and secure communications to link civilian leaders with military assets, anywhere in the world. Thursday’s mission also marks the 80th launch by an Atlas V, tracing an ancestry (and an impressive success rate) back to its maiden flight in August 2002.
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In terms of actual launches, the first half of 2019 has proved relatively quiet for ULA, with only two flights conducted to date—the Delta IV Heavy lofted the NROL-71 reconnaissance satellite for the National Reconnaissance Office, back in January, and the final Delta IV Medium+ (5,4) carried the latest Wideband Global Satcom (WGS-10) in March—and the Atlas V fleet itself has seen no action since October 2018, when another 551 deployed the AEHF-4 satellite to orbit. However, despite this only being ULA’s third mission of the year, preparations have been ongoing for some months. On 13 April, less than a month after the WGS-10 launch, ULA’s Mariner cargo ship departed the firm’s Decatur, Ala., facility, laden with the giant Common Core Booster (CCB), which forms the central element of the Atlas V first stage, and the Centaur upper stage.
Eight days later, on Easter Sunday, the Mariner arrived at Port Canaveral and the two stages were offloaded, bound initially for different destinations. The CCB headed for the Atlas Spaceflight Operations Center (ASOC) for receiving steps and preparation ahead of vertical stacking, whilst the Centaur was integrated with the Atlas V inter-stage adapter and the lower portion of the bulbous Payload Fairing (PLF). In mid-May, the CBC was hoisted atop the Mobile Launch Platform (MLP) at the Vertical Integration Facility (VIF), which sits about a quarter-mile (400 meters) from the SLC-41 pad surface. It was tight fit as the giant core stage was rotated and gingerly moved through the VIF doorway and onto the MLP. ULA noted that this marked the 65th occasion in the Atlas V program that the so-called “Launch Vehicle On-Stand” (LVOS) had taken place at the Cape. The other 15 Atlas Vs—most recently the booster for NASA’s InSight mission to Mars—have all been flown out of Vandenberg Air Force Base, Calif.
Also in May, the Centaur upper stage was mated to its inter-stage adapter, in a “efficiency process” known as Offsite Vertical Integration (OVI). “The OVI eliminates multiple lifting operations at the VIF and saves several days in the pre-launch schedule,” ULA noted. On the AEHF-5 mission, the Centaur will conduct three “burns” over a 5.5-hour period to deliver its payload to orbit. Early in June, inside the VIF, the five solid-fueled motors were attached to the Atlas V CCB. Meanwhile, in Astrotech Space Operations’ payload processing facility, AEHF-5 was encapsulated in its bulbous payload fairing on 5 June, ready for transfer to the VIF for integration aboard the Atlas V.
Originally targeted for launch in late June, the mission was postponed until no earlier than 17 July, due to a vehicle battery failure during final processing. “Additional time is needed for the technical team to complete the evaluation of the issue and replace the battery, noted ULA.” Then, last month, it slipped again until no sooner than 8 August, due to an anomaly experienced during component testing at a supplier, which created “a cross-over concern.” At length, on 25 July, ULA confirmed the revised launch attempt would occur during a two-hour “window”, from 5:44 a.m. EDT through 6:44 a.m. EDT 8 August.
When operational, the 13,600-pound (6,170 kg) AEHF-5 will take its place as the fifth member of a “constellation” of high-powered satellites, providing fast and secure communications to connect civilian leadership with military assets, anywhere in the world. Built by Lockheed Martin in Sunnyvale, Calif., and with a “protected communications payload” developed by Northrop Grumman Corp., headquartered in Bethpage, N.Y., the AEHF system replaces the outdated Milstar network and—as its name implies—operates at extremely high frequencies (44 GHz uplink) and super-high frequencies (20 GHz) downlink and can relay communications directly, without the need to pass through ground stations. Their phased-array antennas help to eliminate potential sources of radio jamming and each AEHF can support data rates as high as 8.192 Mbits/sec.
The system features advanced encryption, low probability of intercept and detection and the ability to penetrate the electromagnetic interferences caused by nuclear weapons to route communications, real-time video, maps and targeting data to users on land, at sea or in the air. By 2020, when AEHF-5 and the final member of the fleet, AEHF-6—which boasts the first 3D-printed part ever flown on a Lockheed Martin-built military satellite—are fully operational, the six-strong fleet will provide full surface coverage between 65 degrees North and 65 degrees South latitude.
Northrop Grumman reportedly completed AEHF-5’s protected communications payload in March 2017 and delivered it to Lockheed Martin for integration and testing. By May of the following year, the fully integrated satellite was put through 39 days of extensive Thermal Vacuum Chamber (TVAC) and acoustic testing, ahead of systems-level inspections. “TVAC and acoustic tests are critical milestones in the production cycle of a satellite, where we have one shot to get it right,” said Michael Cacheiro, vice president for protected communications gharsh space environment.”
Early in May 2019, AEHF-5 was delivered from Sunnyvale to Cape Canaveral Air Force Station aboard a C-5 Galaxy aircraft for final pre-launch testing and integration with the mighty Atlas V. With launch targeted to occur only eight months after AEHF-4, this is the shortest interval between two AEHF flights. The network’s first element launched in August 2010, followed by others in May 2012, September 2013 and last October. “We are thrilled to return to the Cape to launch AEHF-5 less than a year after launching AEHF-4,” noted Mr. Cacheiro. “AEHF-4 arrived to its on-orbit operational position a month early, where it demonstrated Extended Data Rate (XDR) connectivity. This is an exciting time where we are witnessing the deployment of critical capabilities of the current four AEHF satellites in geosynchronous orbit, which provide ten times greater capacity than the original Milstar constellation. The AEHF system is essentially a high-capacity data network in the sky and this is a complete paradigm shift for the future of protected communications.”
Thursday’s launch marks the tenth flight of the Atlas V 551, whose Russian-built RD-180 engine at the base of the CCB and five solid-fueled motors produce a liftoff thrust of 2.6 million pounds (1.1 million kg). The 206-foot-tall (62.8-meter) rocket can haul up to 19,620 pounds (8,900 kg) of payload to geostationary altitude, some 22,300 miles (35,900 km) above the planet. First utilized in January 2006 to launch NASA’s New Horizons probe to Pluto, it has since seen service to boost the Juno mission to Jupiter in August 2011, five heavyweight Mobile User Objective System (MUOS) military communications satellites between February 2012 and June 2016, a dedicated payload for the Air Force Space Command (AFSPC-11) in April 2018 and most recently AEHF-4 last October.
The rocket was rolled out from the 30-story VIF to its launch pad on the morning of August 6, while SpaceX was preparing to launch their next Falcon 9 mission at neighboring SLC-40. The U.S. Air Force 45th Space Wing is forecasting 80% favorable odds of acceptable conditions for launch during the 120-minute ‘window’ opening at 5:44am EDT, calling for chance of anvil clouds from distant thunderstorms.
Sunrise is scheduled for 6:49am EDT, so if the launch delays it will turn into a visually spectacular sight, even moreso than usual, as the light of twilight and sunrise illuminate the rocket’s plume, ascent, stage separations and other events. Such was seen across Florida on Sep 2, 2015 with launch of MUOS-4 for the U.S. Navy atop the same rocket variant (see video above). Californians freak out around LA for the same reason when rockets launch from Vandenberg Air Force Base at dawn and dusk too, seeing the same phenomenon.
The 551 is expected to fly again in December 2019 to launch the Air Force’s Space Test Program (STP-3), on a mission which will see it trial the new Graphite Epoxy Motor (GEM)-63, which boast higher performance and lower operational cost than the currently in-service GEM-60.
With two Delta IV launches conducted thus far, and in addition to the forthcoming AEHF-5 and STP-3 missions, ULA also expects to stage the long-awaited uncrewed and piloted test-flights of Boeing’s CST-100 Starliner to the International Space Station (ISS) before year’s end, currently tracking dates in September and November. Notably, in late August the much-delayed final flight of the “single-stick” Delta IV will transport the second Block III Global Positioning System (GPS) satellite to orbit.
And if astronauts ride a Starliner before the end of the year, it will close with the first Atlas booster to carry humans since May 1963.
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