Delta IV thunders off the pad with AFSPC-6 payload

Photo Credit: United Launch Alliance

CAPE CANAVERAL, Fla. — Lighting up the early-morning sky over central Florida, the United Launch Alliance (ULA) Delta IV Medium+ (4,2) rocket thundered off the pad on the sixth U.S. Air Force Space Command (AFSPC-6) mission. As part of the Geosynchronous Space Situational Awareness Program (GSSAP), two Orbital ATK-built satellites were sent to a near-geostationary orbit (GEO).

Liftoff from Space Launch Complex 37 took place at 12:52 a.m. EDT (04:52 GMT) Aug. 19, about five minutes into the 65-minute launch window. The two GSSAP satellites will allow for more accurate tracking and characterizing of human-made objects in orbit. While the spacecraft will be sent to near-GEO, due to the military nature of the mission, the exact parameters of the orbit were not revealed.

According to Wayne Monteith, 45th Space Wing commander and mission Launch Decision Authority, the Delta IV launch was the culmination of many long hours of work by the entire mission team.

“Congratulations to the AFSPC-6 integrated team and all our mission partners on a successful launch that will enhance our capabilities in space situational awareness and our space-based space situational awareness architecture,” Monteith said in a press release. “Today’s mission is just another example of our unwavering focus on mission success and guaranteeing assured access to space for our nation while showcasing why the 45th Space Wing is the ‘World’s Premiere Gateway to Space.’”

This rocket, the Delta IV Medium+ (4,2), is a two-stage, 207-foot (63-meter) tall rocket. This particular version sports a 4-meter fairing and two strap-on solid rocket motors.

The rocket’s common booster core (CBC), the first stage, is 133.9 feet (40.8 meters) tall and 16.7 feet (5.1 meters) in diameter. The CBC has a single Aerojet Rocketdyne RS-68A engine on the bottom that consumes liquid hydrogen and oxygen to produce 702,000 pounds (3,123 kilonewtons) of thrust at sea level.

Each of the Orbital ATK-built strap-on GEM 60 solid rocket motors are 60 inches (152 centimeters) in diameter and 53 feet (12.2 meters) tall. They burn for about 90 seconds and are detached from the stack some 100 seconds into the flight. They will each produce 280,000 pounds (925 kilonewtons) of thrust.

The second stage of the vehicle is the Delta Cryogenic Second Stage (DCSS). It utilizes a single RL10B-2 engine. According to ULA’s product sheet, the engine is the world’s largest carbon-carbon extendable nozzle.

The DCSS produces 24,750 pounds (110 kilonewtons) of thrust. It burns liquid hydrogen and oxygen for up to 465 seconds. The second stage is 13.1 feet (4 meters) wide and 39.5 feet (12 meters) long.

A Delta IV Medium+ (4,2) is capable of sending 28,440 pounds (12,900 kilograms) into low-Earth orbit and 13,580 pounds (6,160 kilograms) into geostationary orbit.

Weather for tonight’s launch was predicted by the 45th Space Wing to have an 80 percent chance of acceptable conditions at the scheduled time of liftoff with cumulus clouds being the primary worry. However those never materialized. At the launch viewing site, skies were clear and the weather remained in the green throughout the countdown.

Fueling of the vehicle began about 3.5 hours prior to liftoff when about 100,000 gallons of liquid hydrogen started filling into the rockets CBC. Liquid oxygen started not long after. Altogether, the four cryogenic fuel tanks (a set for both stages) took about two hours to fill.

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