The Delta IV Heavy is an expendable rocket, the largest type of the Delta IV family. It is similar to the Medium except that it uses two additional CBCs instead of using GEMs. These are strap-on boosters which are separated earlier in the flight than the center CBC. The Delta IV Heavy (Delis expendable rocket, the largest type of the Delta IV family. It is similar to the Medium except that it uses two additional CBCs instead of using GEMs. These are strap-on boosters which are separated earlier in the flight than the center CBC. Delta IV Heavy also features a stretched 5-meter composite payload fairing. An aluminum trisector (3 part) fairing derived from the Titan IV fairing is also available. This was first used on the DSP-23 flight.
