After wrapping up one of its quietest years on record in 2017, with only eight launches across its Delta IV, Atlas V and Delta II fleet, United Launch Alliance (ULA) has begun 2018 with a bang, by flying two missions from the West and East Coasts, just one week apart. The company launched its final Delta IV Medium+ (5,2) from Vandenberg, last Friday, 12 January, and at 7:48 p.m. EST Friday, 19 January sent the fourth member of the geosynchronous-orbiting Space-Based Infrared System (SBIRS GEO-4) aloft from Space Launch Complex (SLC)-41 at Cape Canaveral Air Force Station, Fla. Launch was originally scheduled for Thursday night, but was scrubbed, due to a ground-based issue associated with the liquid oxygen system. It marks an impressive start to 2018, in which ULA plans to fly out the last of its “single-stick” Delta boosters, including the final Medium and the swansong of the Delta II.
Rocket launches out of the Cape, whilst not necessarily an everyday sight, do tend to have a measure of regularity. However, the departure of SBIRS GEO-4 looked peculiar to many observers, launching atop the rarely-used “411” configuration of the venerable Atlas V. Flown only five times since April 2006—firstly transporting the Astra 1KR communications satellite to orbit, followed by the classified NROL-28 payload in March 2008, a pair of Naval Ocean Surveillance Satellites (NOSS) in April 2011 and NASA’s Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-REx) in September 2016—the 411 boasts a 13-foot-diameter (4-meter) payload fairing, a single-engine Centaur upper stage and a single strap-on rocket booster. All told, the combo carries the potential to deliver up to 26,786 pounds (12,150 kg) to low-Earth orbit and 13,120 pounds (5,950 kg) to geosynchronous orbit, some 22,236 miles (35,786 km) high.
With only a single strap-on booster to one side of the Atlas V, tonight’s launch created a peculiarly asymmetric perspective for the gathered spectators along the Space Coast. Although the RD-180 engine of the Common Core Booster (CCB) has a steering gimbal to compensate for the offset thrust, the first-stage plume appeared to flare noticeably to one side. And for the SBIRS GEO constellation, it was another first, for the three previous satellites—launched in May 2011, March 2013 and January 2017, respectively—had all ridden the “barebones” Atlas V 401, without a strap-on booster. “For prior missions, this customer preferred to place the expended Centaur in the designated disposal orbit (junkyard, from which stages slowly decay into re-entry),” ULA CEO Tory Bruno noted in a Tuesday, 17 January tweet. “On this flight, the [booster] provides enough energy to allow Centaur to be immediately deorbited.”
Built by Lockheed Martin, SBIRS GEO-4 provides an additional set of powerful infrared eyes, part of a multi-billion-dollar Pentagon effort to replace the outdated Defense Support Program (DSP) network of missile early-warning satellites, whose ancestry extends back to the early 1970s. SBIRS is expected to enable the United States’ space surveillance needs for at least the next two decades, with focuses including advanced early warning, missile defense and battlespace characterization. In its final form, it will comprise six GEO satellites in geostationary orbit, together with associated sensors aboard the high-elliptical-orbiting HEO-1 and HEO-2 satellites, launched in June 2006 and March 2008, as well as an expansive ground-based command, control and data-processing system.
The successful launch of SBIRS GEO-1 in May 2011 marked the culmination of a long and tortured development process, which saw the program costs literally balloon by over 400 percent from an estimated $4 billion to over $17 billion. According to General Accounting Office auditors, and reported by Defense Industry Daily in February 2013, it suffered from “immature technologies, unclear requirements, unstable funding, underestimated software complexity, poor oversight and other problems”. The Air Force’s apparent lack of alternatives for an urgent national requirement to have an advanced surveillance system in orbit to monitor ballistic missile launches and nuclear events seems to have prevented SBIRS’ cancelation. Its capabilities include highly sophisticated scanning and staring sensors, with improved infrared sensitivity and the scope to provide a wide-area (“scanning”) surveillance of missile launches and natural phenomena across the Home Planet, as well as observing small-area regions (“staring”) with superior sensitivity and reliability. The GEO-2 satellite followed into orbit in early 2013, followed by GEO-3 last January.
Contracts for GEO-4’s construction had been awarded in early 2011 and the core structure was delivered to Lockheed Martin’s Mississippi Space & Technology Center in May 2012, for the installation of its propulsion subsystem. By May 2014, the propulsion module had been completed and SBIRS GEO-4 progressed into final assembly, integration and testing. Later that year, Northrop Grumman delivered the imaging payload for the satellite for installation at Lockheed Martin’s facility in Sunnyvale, Calif. In the meantime, long-lead-time items for the follow-on GEO-5 and GEO-6 satellites were contracted in March 2013 and a $1.86 billion contract was signed between the Air Force and Lockheed Martin in June 2014 to fabricate the fifth and sixth members of the SBIRS GEO fleet.
Processing smoothly along its own flow to launch, the 4,500-pound (2,000 kg) GEO-4 bird was flown from Moffett Federal Airfield in Sunnyvale, Calif., to Cape Canaveral Air Force Station, Fla., last 31 October, aboard a C-5 Galaxy aircraft. The design of the satellite is based upon Lockheed Martin’s tried-and-true AM2100 “bus”, equipped with twin solar arrays and a powerful communications payload. “SBIRS provides our military with timely, reliable and accurate missile warning and infrared surveillance information,” said Tom McCormick, vice president of Lockheed Martin’s Overhead Persistent Infrared Systems mission area. “We look forward to adding GEO Flight 4’s capabilities to the first line of defense in our nation’s missile defense strategy.” Last month, teams at the Cape began loading 430 pounds (195 kg) of fuel aboard the SBIRS GEO-4 propulsion system to enable its lengthy climb to geosynchronous orbit and maintain operations for a 12-year lifespan.
On 9 January, the satellite was encapsulated into its 13-foot-wide (4-meter) Large Payload Fairing (LPF) and integrated atop the Atlas V 411 at SLC-41 two days later. The Launch Readiness Review (LRR) was completed on Tuesday, 16 January, ahead of Wednesday’s rollout of the 194-foot-tall (59-meter) stack from the Vertical Integration Facility (VIF) to the SLC-41 pad surface. In keeping with longstanding tradition, the booster and mission was dedicated to former ULA employee Erik Madison, who passed away in November 2016. Emblazoned on the side of the rocket, ULA honored “our colleague and friend”.
The weather outlook for Thursday’s opening launch attempt was favorable, with a 90-percent chance of acceptable conditions, tempered only by a risk of violating the Cumulus Cloud Rule. “On launch day, high pressure with favorable weather persists with cold morning temperatures,” noted the 45th Space Wing at Patrick Air Force Base in its L-1 briefing on Wednesday morning. “Through the afternoon, winds become from the north and continue to trend down with peaks in the mid-to-upper teens during the window. There is a slight threat of an isolated shower. The primary concern for launch is cumulus clouds coming in off the Atlantic.” A similarly 90-percent-favorable forecast was provided for Friday’s backup launch attempt.
As darkness fell over the Cape on Thursday evening, ULA prepared for its 125th mission, as well as the 75th flight by a member of the Atlas V family. Since August 2002, the fleet has delivered ten commercial communications satellites, 16 National Reconnaissance Office (NRO) payloads and a host of other military cargoes, including four flights of the X-37B Orbital Test Vehicle (OTV). Scientific customers have included three missions to Mars, the New Horizons voyage to Pluto and the Kuiper Belt, the Juno orbiter to Jupiter and exploratory ventures to the Moon and to the carbonaceous asteroid Bennu. With a 100-percent mission success rate, the Atlas V remains one of the world’s most reliable launch vehicles. And that reliability was not to be disappointed.
Aboard the Common Core Booster (CCB), storable rocket-grade kerosene (known as “RP-1”) had previously been loaded, with liquid oxygen tanking getting underway late in the countdown, to allow boiled-off cryogens to be replenished until close to T-0. In readiness for fueling, the propellant storage area was chilled down, in order to prevent thermal shocking and damage to critical vehicle components. Fuel lines were purged and SLC-41 was cleared of all personnel and roadblocks established. By 6:50 p.m. EST, about an hour before the opening of Thursday’s launch window, liquid oxygen tanking aboard the Centaur upper stage had reached Flight Level and entered Replenishment Mode. At the same time, loading of liquid hydrogen aboard the Centaur began. However, despite the good weather, it was not ULA’s day. “Scrub,” tweeted Mr. Bruno at 7:20 pm. “LOX fill-and-drain valve acting up. Need to go out to the pad to check it out.”
Friday’s backup attempt proceeded with greater smoothness, tracking a revised T-0 at 7:48 p.m. EST. A final “Go/No-Go” poll of all stations was met with a string of “Go” calls across the board, with the Launch Director coming on the net to officially issue authorization to the Launch Conductor to launch. The clock was released from its final pre-planned hold point at T-4 minutes, entering the terminal count. During this period, the Atlas V’s propellant tanks were pressurized and the Flight Termination System (FTS) was placed onto internal power and armed. “Range Green” came the call from the Range Operations Co-ordinator (ROC) at T-1 minute.
A little under three seconds before zero, the Russian-built RD-180 main engine at the base of the CCB roared to life, pumping out 860,000 pounds (390,000 kg) of thrust from its twin nozzles. The Atlas V 411 departed SLC-41 at T+1.1 seconds, its side-mounted booster producing a characteristic “sideways” plume as the vehicle commenced its climb. Passing Mach 1 and maximum aerodynamic pressure about a minute into the flight, the rocket shed its side booster at the 140-second point. The RD-180 continued the push towards orbit, finally shutting down at 7:52 p.m. EST, some four minutes after leaving the Cape. Shortly afterwards, the Centaur upper stage and SBIRS GEO-4 separated from the stack, preparatory to the first of three “burns” to position the satellite into orbit.
The first burn of the Centaur’s RL-10C-1 engine ran for over nine minutes, generating 22,900 pounds (10,387 kg) of thrust. Shutting down at 8:02 p.m. EST, the stack coasted for ten minutes, before the second burn got underway. This was a shorter firing, lasting around five minutes, which positioned the $1.2 billion SBIRS GEO-4 for separation.
The satellite departed the upper stage at 42.5 minutes into tonight’s flight, whereupon the Centaur fired its engine for one final burn, lasting just a couple of seconds, to position itself for a safe deorbit and disposal. At the time of writing, the Centaur was due to impact the ocean early Friday morning, some 9.5 hours after liftoff.
At the moment of separation, SBIRS GEO-4 was in an initial orbit with an apogee of 22,276 miles (35,851 km) and a perigee of 115 miles (185.2 km), inclined 16.88 degrees to the equator. It marks ULA’s second successful mission of 2018, with a full plate manifested for the rest of the year. Current plans call for up to 13 more flights, including eight by the Atlas V, four Delta IVs—including two Heavy launches, one from the Cape and the other from Vandenberg—and the final swansong of the long-serving Delta II, which will deliver NASA’s Ice, Cloud and Land Elevation Satellite (ICESat-2) into orbit. Additionally, 2018 is expected to see a pair of classified missions for the National Reconnaissance Office, several military communications satellites, the Parker Solar Probe and Mars-bound InSight lander, the first uncrewed and piloted test-flights of Boeing’s CST-100 Starliner for Commercial Crew operations and, coming up in March, the next Geostationary Orbiting Environmental Satellite (GOES)-S.