Delta IV is an expandable rocket, which executes launch services for the United States government, for the most part – chiefly for satellites flown by the National Reconnaissance Office or the Department of Defense. 

A distinguished exception was the 2014 test of the Orion Spacecraft aboard a Delta IV Heavy; the flight was made to test a spacecraft anticipated to bring astronauts beyond the orbit of the planet to deep-space destinations. A Delta IV Heavy will also take off the Parker Solar Probe in 2018, to gather data from close the sun. 

McDonnell-Douglas that later become part of the Boeing, constructed and designed the Delta IV, and now it’s manufactured by the United Launch Alliance. It takes off from two locations: Vandenberg Air Force Base in California and Cape Canaveral Air Force Station location in Florida. 

The Delta IV comes in 3 different configurations: The Delta IV Heavy, the three variants of the Delta IV Medium-Plus and the Delta IV Medium. The rocket types can have variations in their propellant types and payload fairings depending on the configuration.

The Delta IV medium has a massive core booster first state and the Delta II second stage, which is thirteen feet in diameter. The last takeoff of the Delta IV Medium occurred last November 2006. The first launch of Delta IV Heavy took place on December 21, 2004, and lead to a fractional failure. The main demonstration payload didn’t reach its intended orbit, as the core booster stage cut off ahead of time. 

In 2015, the United Launch Alliance declared plans to retire the Delta IV Medium configurations this 2018 or 2019 because of its enhanced cost compared to the competition. At the time, the firm said it intended to change the Delta IV with another takeoff vehicle, known as Vulcan. The Delta IV heavy will keep in service for the time being. 

The last takeoff of the Delta IV M- variant happened on January 12, 2018, through a remarkable launch, which stares a reconnaissance satellite placed into the low orbit of the Earth. The Parker Solar Probe will take off no earlier than 31st of July 2018, aboard a Delta IV Heavy. The probe will conduct seven flybys of Venus to make its orbit closer to the sun until it’s inside the orbit of Mercury and at an estimated closest approach of four million times. Its objective is to offer an improved forecast of the activity of the sun.