An illustration of the Delta 4-Heavy rocket and payload. Credit: Boeing

Common Booster Core -- First Stage
The Delta 4 CBC design is optimized for balanced performance over a wide range of payloads using the high-performance RS-68 main engine powered by liquid hydrogen (LH2) and liquid oxygen (LO2). The RS-68 is throttleable to serve various mission profiles operating at 102% and 58% thrust level. Two separate 5-m-dia. LO2 and LH2 tanks provide the majority of the first stage structure. These two tanks are integrated wih a composite cylinder, called the centerbody. At the forward end of the CBC, another composite cylinder, the interstage, provides the interface between the CBC and the cryogenic second stage. For the port and starboard strap-on CBCs of the Heavy configuration Boeing replaces the interstage structure with a composite nose cone. For the 4-m second stage configurations, the interstage is tapered to integrate the 4-m-dia. second stage.

At the aft end of the CBC, an engine section provides the thrust structure and thermal shield that integrates the RS-68 main engine to the CBC. The RS-68 requirements were balanced to enable operational thrust at lower chamber pressures. This design trade increase engine reliability, while reducing complexity. Compared with the SSME, the RS-68 has an 80% reduction in unique part count. Even with lower performance than comparable LO2/LH2 engines, the RS-68 develops a world record 2,949 kN (663,000 lb) of sea-level thrust with a specific impulse (Isp) of 407.55 seconds at maximum power level.

Cryogenic Second Stage
The spacecraft is propelled to orbit using our flight proven cryogenic second stage. This second stage comprises a 5-m-diameter fuel tank, a composite intertank structure, a liquid oxygen tank, avionics equipment shelf, avionics suite, attitude control system and is powered by a Pratt & Whitney RL10B-2 liquid rocket engine that produces 100kN (24,750 lb.) of thrust. The RL10B-2, with its high expansion, carbon-carbon nozzle provides an Isp of 460.4 sec. The 5-m second stage for the Heavy launch vehicle is similar to the 4-m Medium design and operation, however, the Heavy integrates larger tanks for added performance. The heritage redundant inertial flight control assembly (RIFCA) is included to ensure accurate insertion into the desired orbit. To enable the Heavy configuration cryogenic second stage to survive the long coast period and operate its electrical and attitude control systems, a GEO kit that is made up of added tanks and batteries is added to the second stage to increase capacity for Hydrazine, Helium and power for DemoSat's GEO mission requirement.

Payload Attach Fitting
Boeing offers a variety of payload attach fittings (PAFs) that provide the mechanical and electrical interfaces between the payload and the launch vehicle. The Heavy vehicle integrates the DemoSat using the 1194-5 PAF. The 1194 refers to the spacecraft interface diameter and 5 refers to the diameter of the PAF-second stage and PAF-payload fairing (PLF) interfaces. The 4-m-dia. version of this PAF, the 1194-4, was successfully demonstrated on the Eutelsat W5 mission in 2002. The 1194-5 PAF is an 1194-mm (47-in.) diameter clampband interface attached to our composite conical structure. The 5-m-dia. aft ring of the PAF attaches to the launch vehicle second stage and provides attach points for the PLF.

Fairing
The 5-m diameter payload fairing (PLF) encapsulates the spacecraft and provides a benign environment during flight. Design features of the 5-m PLF include composite blended cone/cylinder structure, biconic separation and separation system, access doors and an acoustic attenuation system. The 76.2-mm-thick acoustic absorption blankets are provided in the cylinder section as well as the lower section of the nose cone. The acoustic blankets are vented through a mesh filter that controls particulates to a negligible contamination level.

The separation system for all of our fairings is a non-contaminating thrusting joint separation system patented by Boeing. Fairing separation is accomplished when pyrotechnics at the aft ends of each joint are detonated. The assembly in each cylinder rail retains the detonating-fuse gases to prevent contamination of the payload during the separation event. This type of thrusting joint has been subjected to more than 300 ground tests and has flown more than 200 missions with no failures or spacecraft contamination.

A separation augmentation spring system is added to the composite fairings to reduce fairing pitch rate and increase center-of-gravity velocity to provide clearance at fairing jettison. The springs in this system are preloaded and installed on the aft frame after mating to the second stage. Boeing has proven 100% mission success in over 400 PLFs to date.