The United Launch Alliance Delta IV Heavy that will lift Orion to an orbit has been loaded with liquid hydrogen fuel and liquid oxygen to power its engines. The Delta IV Heavy uses three core stages bolted together for the first stage. Each core holds about 110,000 gallons of the liquid hydrogen and 40,000 gallons of liquid oxygen for a total load of 330,000 gallons of hydrogen and 120,000 gallons of oxygen. The rocket will turn those super-cold propellants into about 2 million pounds of thrust at liftoff, enough to push the 1.63 million pounds of rocket, spacecraft and fuel straight up into the sky. The second stage uses the same kind of propellants but in much less quantity – 4,500 gallons of liquid oxygen and about 10,000 gallons of liquid hydrogen.
The second stage will make two critical burns during Orion’s mission, the first to get it into an initial orbit of 115 miles by 552 miles, then to push Orion into its high orbit reaching 3,609 miles above Earth. The second stage will separate to leave Orion on its own for re-entry at the end of the mission.
We are moving through this morning’s countdown and everything remains on track for a liftoff at 7:05 a.m. EST, including the weather. We’ll have the final launch forecast shortly, followed by a 15-minute built-in hold at T-4 minutes that will set the stage for the terminal countdown phase.
Launch polls will be conducted during this hold to clear the way for liftoff. Orion will switch over to its own battery power then the final “go/no-go” call will be made. After that, the Delta IV’s three core stage engines will ignite and rev up to 2 million pounds of thrust.
The Delta IV Heavy and Orion will clear the tower in just a few seconds to begin a carefully choreographed climb skyward. The core stages on either side of the rocket will burn their propellants and fall away at T+3minutes, 56 seconds. The central core stage will continue for another 94 seconds as the rocket and spacecraft climb higher and pick up more speed. The first stage will fall away and the second stage will take over to put Orion into an initial orbit of 115 miles by 552 miles.
“We haven’t had this feeling in a long time, this feeling of beginning something new – in this case deep space exploration. It’s a new mission and there are some things that we’re going to learn tomorrow from this flight test that we will apply.”
United Launch Alliance operates the Delta IV Heavy, the largest rocket in the American launch inventory. The first stage of the Delta IV Heavy includes three core stages, each one 134-feet-tall and 16.7 feet in diameter. An RS-68 engine is at the base of each core stage to give the rocket a combined thrust of about 2 million pounds. The stage holds super-cold liquid oxygen and liquid hydrogen propellants. The second stage of the Delta IV Heavy is powered by a single RL10B-2 engine that also uses a combination of liquid hydrogen and liquid oxygen. The Orion spacecraft is bolted to the top of the second stage.
The Spaceflight Meteorology Group at Johnson says the weather looks good off the coast of Baja California where Orion will descend and splashdown later this morning to end the flight test. Navy ships are waiting in the area to recover the Orion spacecraft.
The three core stages of the Delta IV Heavy are venting oxygen as the propellant boils off from its cryogenic liquid state at minus-297 degrees F. The gaseous oxygen is dumped to prevent a pressure buildup inside the tank. The liquid hydrogen also vents as its temperature increases above minus-423 degrees F, but the gaseous fuel is carried away from the rocket before being cast aside. Once the tanks are filled, pumps continue to trickle the propellants into the stages to replace the small amount that boils off.
Today’s launch blog comes to you from Hangar AE at Cape Canaveral Air Force Station in Florida. We are about four miles south of Space Launch Complex 37.
AE is a NASA facility that is probably best known as the communications hub for the agency’s uncrewed missions by the Launch Services Program including the MAVEN and Curiosity missions to Mars among dozens of others. Kennedy Space Center began maintaining the facility in 1960. NASA TV broadcasts launch commentary from here for the LSP missions and today’s on-air coverage also is originating from here.
The teams of engineers and flight controllers that will conduct Orion’s flight test took their places about an hour ago at consoles here at Cape Canaveral and at Houston’s Mission Control Center at Johnson Space Center. Everything from system checkouts and confirmations to the fueling process is done remotely by the controllers since no one is allowed at the launch pad during this final phase of the countdown. Once Orion leaves the launch pad, Mission Control takes over as it did during Space Shuttle missions.