Earth Departure Stage
| Country of origin | United States |
|---|---|
| Used on |
Ares V SLS Block II |
| Associated stages | |
| Comparable | S-IVB |
| Launch history | |
| Status | Cancelled (Ares V) Cancelled (SLS) |
| Ares V EDS | |
| Engines | 1 J-2X |
| Thrust | 1,310 kilonewtons (290,000 lbf) |
| Specific impulse | 448 seconds (vacuum) |
| Fuel | LH2/LOX |
| SLS Block II EDS | |
| Length | 24 metres (79 ft) |
| Engines | 3 J-2X |
| Thrust | 3,930 kilonewtons (880,000 lbf) |
| Specific impulse | 448 seconds (vacuum) |
| Fuel | LH2/LOX |
The Earth Departure Stage (EDS) is the name given to the second stages of two Shuttle-Derived Launch Vehicles, the Ares V and the Block II Space Launch System. The EDS is intended to boost the rocket's payload into a parking orbit around the Earth and from there send the payload out of low Earth orbit to its destination in a manner similar to that of the S-IVB rocket stage used on the Saturn V rockets that propelled the Apollo spacecraft to the Moon between 1968 and 1972.
The EDS used on the Ares V would have been propelled by a single J-2X main engine fuelled with liquid oxygen (LOX) and liquid hydrogen (LH2), and was to have been designed at NASA's Marshall Space Flight Center in Huntsville, Alabama as part of Project Constellation. Originally, the stage would have been based on the Space Shuttle's External Tank, and would have used two J-2X engines, while the Ares V core booster would have used five Space Shuttle Main Engines and two 5-segment Solid Rocket Boosters during the first eight minutes of flight. When the Ares V was then redesigned around the use of five (later six) RS-68B rocket engines currently used on the Delta IV EELV family, the EDS was then redesigned using only a single J-2X engine and a common bulkhead, thus in its final design, the EDS resembled an oversized S-IVB, but with the capability of on-site storage (using new propellant storage techniques along with a "loiter skirt" containing solar panels for electricity) for up to 4 days, something impossible with the old S-IVB.
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