Massive Delta IV Heavy set to launch Thursday
CAPE CANAVERAL, Fla. — A United Launch Alliance (ULA) Delta IV Heavy is scheduled to roar skyward at 1:59 p.m. EDT (17:59 GMT) on June 9 from Cape Canaveral Air Force Station’s Space Launch Complex 37 in Florida. The payload is a classified satellite for the National Reconnaissance Office (NRO).
The window for Thursday’s launch opportunity is unspecified but is expected to open at 1:30 p.m. EDT and extend to no later than 6:30 p.m. EDT (22:30 GMT).
The NROL-37 mission will launch one of the largest satellites in the world atop the United State’s biggest rocket. The payload, although classified, is likely a spy satellite heading for geostationary Earth orbit (GEO) some 22,000 miles (35,000 kilometers) in altitude, according to Spaceflight Now.
The weather for Thursday’s launch is not predicted to be particularly good. The 45th Space Wing has predicted a 60 percent chance of weather violating launch rules. The primary concerns for flight are anvil clouds, cumulus clouds, and lighting.
In the event of a scrub, ULA will try to launch the Delta IV Heavy again on Saturday when weather conditions significantly improve—to a 20 percent chance of weather interfering with launch operations. The primary concern on that day is thick clouds.
Delta IV Heavy rockets are used primarily to send large payloads to GEO. Smaller rockets usually send spacecraft bound for GEO to a geostationary transfer orbit (GTO), which is a highly elliptical trajectory with a high point at approximately the altitude of the final orbit.
A satellite’s onboard thrusters would then circularize the vehicles orbit and fine tune the altitude and position over Earth.
For this mission, the rocket’s upper stage will ignite for a third time to circularize the orbit of the satellite instead of having the spacecraft’s onboard propellant do the job.
The three-core Delta IV Heavy is the world’s highest capacity rocket currently in operation. It can send upwards of 63,470 pounds (28,790 kilograms) to low-Earth orbit, 31,350 pounds (14,220 kilograms) to GTO, or 14,880 pounds (6,750 kilograms) to GEO.
The first of these rockets to be launched took place in 2004. Since then, the Delta IV Heavy has launched a total of eight times—Thursday’s flight should be the ninth. NROL-37 will be the 32nd Delta IV mission (including both the medium and heavy classes) since the vehicle’s inaugural launch in 2002, and the 10th NRO mission to launch on any Delta IV.
The heavy version has three Common Booster Cores (CBC) strapped together, each with a liquid hydrogen (LH2) and liquid oxygen (LOX) consuming RS-68A engine. Each CBC is 134 feet (40.8 meters) tall and 17 feet (5.1 meters) in diameter.
Together, the three RS-68A engines operate at full power during liftoff for a total liftoff thrust of 1.4 million pounds (6,280 kilonewtons). About 44 seconds into flight, the center CBC throttles down to 55 percent to conserve fuel before booster separation.
CBC separation occurs around 242 seconds after launch. The center core then throttles back up to full thrust and is exhausted about 86 seconds later. The central core and upper stage then separate.
The upper stage is powered by a single RL10-B-2—also consuming LH2 and LOX. The stage is 45 feet (13.7 meters) long and 17 feet (5.1 meters) in diameter. The thrust of the single engine is 25,000 pounds (110 kilonewtons). It has a total burn time of 1,125 seconds available to use.
The last time a Delta IV Heavy lifted skyward was during the December 2014 Exploration Flight Test-1 (EFT-1) mission carrying the first uncrewed Orion spacecraft to a high-Earth orbit. That was the first time, outside of the demo mission in December 2004, that a non-military payload flew atop the massive booster.
After this booster roars skyward, the Florida skies won’t hear another Delta IV Heavy for over two years when, on July 31, 2018, NASA’s Solar Probe Plus is slated to launch from Cape Canaveral.
That could also be the first year that two of the massive booster fly. The next NRO mission to use the Delta IV Heavy is tentatively planned to launch from California’s Vandenberg Air Force Base in 2018 to carry the NROL-71 mission.
Derek Richardson has a degree in mass media, with an emphasis in contemporary journalism, from Washburn University in Topeka, Kansas. While at Washburn, he was the managing editor of the student run newspaper, the Washburn Review. He also has a website about human spaceflight called Orbital Velocity.