Delta II

Vehicle Configurations

Vehicle Components

Boeing's Delta II, one of the world's most most successful expendable space launch vehicles, is an updated version of the Thor-Delta series that first flew for NASA in 1960.  In the early 1980s, NASA halted procurement at Delta 183 after shifting all payloads to the Space Transportation System.

To create Delta II for the U.S. Air Force Medium Launch Vehicle (MLV) program after the 1986 Challenger accident, McDonnell Douglas had to restart Delta production.  The new rocket's first stage was stretched 3.66 meters and it's payload fairing was widened.  The ultimate Delta II version, which did not appear until 1990, was boosted by more powerful solid rocket motors and a more powerful first stage motor.  Delta 184, the first Delta II, launched GPS 14 on Valentine's Day, 1989.  

Boeing uses a four-digit numbering system to identify specific Delta models.  The first digit indicates the first stage and solid rocket motor (SRM) type.  The first Delta II models, 16 altogether, were 6000-series birds with Extra Long Extended Tank (XLET) Thor first stages, with a Rocketdyne RS-27A main engine, and with Thiokol Castor 4A SRMs.  The current 7000-series Delta II uses more powerful Alliant Graphite Epoxy SRMs (GEMs).  

The second digit tells how many SRMs are used, usually 3, 4 or 9.  When nine SRMs are used, six ignite on the pad.  The remaining three ignite in the air after the first six burn out.   

The third digit indicates the type of second stage.  Since 1982, Delta has used a Type 2 second stage, powered by an Aerojet AJ10-118K pressure-fed, restartable hypergolic engine.   

The fourth digit tells the optional third stage type.  Delta II currently can be configured with no third stage (Type 0), with a Star 48B (Type 5), or with a Star 37 (Type 6).  These solid motors are spun up on a second-stage-mounted spin table to add stability prior to release. Delta II does not use a third stage for low earth orbit missions.

In 2003, a new Delta II type, the 7XXX-H series (H for "Heavy") debuted. Delta II Heavy uses nine of the larger, more powerful GEM-46 LDXL SRMs that were originally developed for Boeing's Delta III.

Three Delta II payload fairings are available.  The standard 2.9 meter diameter aluminum hammerhead payload fairing was designed to handle GPS-class payloads.  A 3 meter tapered composite fairing is becoming a new standard, replacing the aluminum fairing. 

Versatile Delta II has flown a wide variety of missions from fixed pads at both Cape Canaveral (SLC 17A and 17B) and Vandenberg (SLC 2W).  Payload capacity to low earth orbit (LEO) from the Cape ranges from 2.8 to 6.1 metric tons.  Polar orbit LEO payload capacity from Vandenberg is 2.1 to 3.8 tons (more mass could be boosted if SLC 2W were modified to handle the GEM-46 SRMs). Delta II can launch 1.1 to 2.2 tons to a 28.5 degree inclination geosynchronous transfer orbit (GTO) from Canaveral, and can propel nearly as much mass to solar orbit, when a third stage is used.

Although its GTO mission business has dwindled in recent years, Delta II continues to launch LEO satellites, NASA deep space missions, and GPS satellites for the U.S. Air Force. The GPS launches are expected to transition to EELV after 2007, at which time Boeing is expected to mothball Pad 17A at the Cape. Pad 17B will remain in service to support a reduced launch rate to fulfill NASA requirements.

Vehicle Configurations

*GEO:  Geosynchronous Earth Orbit

Vehicle Components

Vehicle Components, Cont'd

References

Delta II Payload Planners Guide, October 2000
ATK Space Propulsion Products Catalog, 2008

 Last Update:  September 5, 2010