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The Delta II Rocket has been flying since 1989 and is operated by United Launch Alliance. Delta II was originally built by McDonell Douglas. The workhorse of the expandable launch vehicle fleet has flown nearly 150 times (149 as of August 2011) and has proven its reliability. In total, the program has logged only one failure and one partial failure. This record makes the launcher the most reliable active launch vehicle. Delta II rockets can be launched from Space Launch Complex 17 at the Cape Canaveral Air Force Station, Florida and from SLC-2 at Vandenberg Air Force Base, California. Delta II uses a Delta XLT-C core stage that is being powered by a flight proven RS-27 engine that is built by Rocketdyne. Rocket Propellant 1 (ultra ourified Kerosine) and liquid Oxygen are used as propellants. Strapped onto the core stage are a number of Solid Rocket Boosters. For the 7920 variant, GEM-46 Motors that are 45 inches in diameter are being used. 6 are ignited at liftoff. When those have burned out, the remaining three SRBs are being fired. The second stage is using Nitrogen Tetroxide and Aerozine as propellants. A restartable Aerojet AJ-10-118K engine places the stack in the desired orbit. The fuels that are used in the second stage require a launch within 37 days following tanking because those propellants are highly corrosive and can cause damage to the rocket that leads to major malfunctions. Also part of stage 2 are all important flight control systems like on-board computers and guidance&navigation control. Those intruments control the flight from the moment of blastoff until spacecraft separation. Delta II can support a third stage. This is optional and not included in a 7920 stack. UlA provides three different payload fairing designs. GRAIL uses the standard 10 feet enclosure. The fairing perotects the payloads from thermal loads during atmospheric flight and separates as soon as the vehicle has left the atmosphere to increase capabilities of the rocket. GRAIL is the final planned launch of the Delta II rocket before the system is retired. However, there is talk about continuing to fly the launcher for chosen missions. Delta II Naming System: First Digit: Delta Series (6 – 6000 Series or 7 – 7000 Series) Second Digit: Number of SRBs (3,4 or 9) Third Digit: Second Stage Engine (2 – Aerojet AJ-10 Engine) Fourth Digit: Third Stage (0 – No third Stage, 5 – Payload assisst module, 6 – Star 37FM H: Heavy Configuration -XX: Indicates type of Payload Fairing Delta II 7920H-10 Specifications
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| Type | Delta XLT-C |
| Inert Mass | 224,200lb |
| Diameter | 8ft |
| Length | 85.6ft |
| Propellant | Rocket Propellant-1 (Kerosene) |
| Oxidizer | Liquid Oxygen |
| Fuel&Oxidizer Mass | 211,220lb |
| Guidance | From 2nd stage |
| Propulsion | 1 RS-27A |
| Thrust at Sea Level | 890kN (200,102lbf) |
| Thrust (Vacuum) | 1,054kN (237,000lbf) |
| Egnine Length | 3.78m |
| Engine Diameter | 1.07m |
| Engine Dry Weight | 2,405lbs |
| Burn Time | 265 sec |
| Chamber Pressure | 700psia |
Solid Rocket Boosters
| # Boosters | 9 |
| 6 Ground lit | |
| 3 Air lit | |
| Type | GEM-46 (Graphite Epoxy Motor) |
| Manufacturer | Aerojet |
| Length | 48.1ft |
| Diameter | 3.8ft |
| Mass | 19140kg (42,200lbs) |
| Fuel | Solid |
| Thrust | 885.2kn (199,000lbf) |
| Burn Time | 76 sec |
Second Stage
| Type | Delta K |
| Diameter | 2.40m |
| Length | 2.40m |
| Inert Mass | 6,953kg (15,331 lbs) |
| Propellant | Aerozine |
| Oxidizer | Dinitrogen Tetroxide |
| Fuel&Oxidizer Mass | 6,004kg (13,236lbs) |
| Guidance | Inertial |
| Propulsion | 1 AJ-10-118K |
| Thrust | 43.4kN (9,753lbf) |
| Engine Length | 2.68m |
| Engine Diameter | 1.53m |
| Engine Dry Weight | 275lbs |
| Burn Time | Variable |
| Engine Start | Restartable |
| Attitude control | Redundant Attitude Control System |
| Roll, Pitch, Yaw Control | |
| Propellant | Hydrazine |
Payload Fairing
| Diameter | 3.0m |
| Length | 8.9m |
| Mass | 3,524kg (7,769lbs) |
| Separation | Pyrotechnic Activation (Actuators) |
| Construction | Sandwich Construction |
| Graphite Epoxy Face Sheets | |
| Aluminum Core |
Photo: NASA Kennedy
Photo: NASA Kennedy
GRAIL Launch Configuration
Source: NASA
