The Cape, Chapter 3, Section 3

Medium and Light Military Space Operations

DELTA II Processing and Flight Features

Before we look at the remaining NAVSTAR II GPS missions, a short review of DELTA II processing and flight highlights is in order. Like the TITAN and ATLAS lines of vehicles, the DELTA line was built on major components supplied by several different contractors. McDonnell Douglas built the basic core vehicle and supplied fairing materials at its plant in Huntington Beach, California, but it shipped them to another plant in Pueblo, Colorado for further assembly and/or match ups with other contractors' components. Rocketdyne provided the DELTA's main engine, and Aerojet supplied the vehicle's second stage engine. DELCO supplied the inertial guidance system, and Morton Thiokol built the strap-on solid rocket motors used for the basic Model 6925 DELTA II vehicle. (Hercules built the Graphite Epoxy Motors [GEMs] used on the more powerful Model 7925.) Once the core vehicle stages and fairing were assembled, they were transported by truck to the Cape and received at Hangar M. After their initial inspection at Hangar M, the first and second stages were taken to the DELTA Mission Checkout Operations Area, where they received telemetry and controls checks, flight simulations and dual composite testing. The first and second stages were transported to the Horizontal Processing Facility (HPF) in Area 55 for destruct system installation. Following processing at the HPF, both stages were moved to Complex 17 and erected.²⁵

	Figure 107: First DELTA II erection (left) and SRM mate (right) at Pad 17A November 1988
	Figure 108: Solid Rocket Motor Operations in Area 57

The strap-on solids and the new DELTA-configured PAM-D followed different processing flows. The DELTA II's Morton Thiokol or Hercules solid rocket motors were trucked to the Cape's Area 57 initially. Once there, the solids were: 1) inspected, 2) checked for leaks and flaws in the solid propellant and 3) built up with the required destruct harnesses and nose cones. Finally, the assembled solid rocket motors were placed on transporters and moved out to Complex 17. The DELTA II's PAM-D motor was received at an ordnance storage area where it was inspected, placed in a cold chamber and cold-soaked. Later, the motor was transferred to the Non-Destructive Test Laboratory (NDTL) where it was x-rayed and placed in a shipping container for transport to the NAVSTAR Processing Facility. At the NPF, the motor was assembled into a complete PAM-D by adding a payload attachment fitting equipped with a fueled nutation control system and a spin table. Following assembly, the PAM-D was spin-balanced at NASA's Explosive Safe Area 60 (on the Cape). The PAM-D was returned to the NAVSTAR Processing Facility and mated to the spacecraft. The payload was installed in a McDonnell-Douglas payload container, loaded on a transporter, and driven out to the launch pad.²⁶

At Complex 17, the entire process came together to create a complete DELTA II launch vehicle. The interstage and payload fairing were brought out to the launch pad from Hangar M. The first stage, solid rocket motors, interstage and second stage were erected and mated at the pad, and the payload fairing was secured in the Mobile Service Tower. The solid rocket motors were aligned, and umbilicals were installed. Electrical and mechanical qualification checks were accomplished about a month before the launch, and subsystem checks continued as the contractor prepared to mate the vehicle with its payload about nine days before lift-off. Ordnance connections and safety checks continued during the last week on the pad, and the vehicle was prepared for launch.²⁷

	Figure 109: PAM-D Motor
	Figure 110: Spacecraft/PAM-D Premate Closeout

The first DELTA IIs were Model 6925 vehicles equipped with nine Morton Thiokol Castor IVA solid rocket motors, but a more powerful version-the Model 7925-made its debut in November 1990. The Model 7925 was equipped with nine Hercules Graphite Epoxy Motors (GEMs) and a more powerful Rocketdyne main engine to boost heavier Block IIA NAVSTAR satellites into orbit. Despite the differences in payload and power, all DELTA II/NAVSTAR II missions had several flight sequences in common. Following lift-off, the DELTA II rolled over into a flight azimuth of 112 degrees for the Model 6925 flights and 110 degrees for the Model 7925 missions. Only six of the DELTA II's strap-on solid rocket motors or GEMs fired at lift-off, but the last three motors fired about one minute after launch (e.g., 59 seconds after launch for the Castor IVAs and 65 seconds after launch for the GEMs). The first six solids separated from the vehicle two seconds later, and the last three motors continued to burn for about one minute before they were jettisoned. The first stage cutoff occurred between 4 minutes and 20 seconds and 4 minutes and 24 seconds after launch (i.e., the Model 6925 burned four seconds longer), and the first and second stages separated eight seconds later. The second stage's Aerojet ITIP engine ignited six seconds after that, and the payload fairing was jettisoned between 11 and 14 seconds later. Following the vehicle's entry into a low-Earth parking orbit, the second stage's engine ceased firing, and the vehicle and its payload went through a "slow roll" to distribute temperature caused by solar radiation. After the vehicle reoriented itself, it coasted until either: 1) the second stage's engine fired once again to assist the PAM-D (third stage) in placing the payload into the prescribed transfer orbit, or 2) the PAM-D ignited to place the payload in the prescribed transfer orbit. In either case, the spacecraft separated from the vehicle about 25 minutes into the flight, and the Apogee Kick Motor was used along with the satellite's Reaction Control System (RCS) to circularize the NAVSTAR's orbit in one of at least six orbital planes approximately 10,900 nautical miles above Earth.²⁸