Earlier this week, the Direct Team released its latest update to their Jupiter rocket, an architecture designed to fulfill the 2005 ESAS (Exploration Systems Architecture Study) and the goals of the existing Project Constellation program. The architecture was presented to the Augustine Commission on 17 June 2009 at their first public session.
One key element in the Direct architecture is the Jupiter, a true Shuttle Derived Launch Vehicle (SDLV). The design work is being done on an off-hours volunteer basis by some of the same NASA and aerospace industry engineers that are part of the Ares team. This group of around 70 engineers has worked on the Direct architecture for the past four years due to their concern with the performance, cost and safety aspects of the Ares I and Ares V rockets as championed by former NASA administrator, Michael Griffin.
The image at the right shows four configurations of the core Jupiter system. Whereas Ares I and Ares V are different rockets, each with many brand new elements, the core of the Jupiter system uses the Space Shuttle Main Engine (SSME), the External Tank (ET) and the Space Shuttle Solid Rocket Booster (SSSRB).
As shown, the engines go on the bottom and the payload goes on top. The payload can be anything from the Orion Crew Excursion Vehicle (CEV) going to the International Space Station (ISS), The Orion plus 30 mT (metric tons) of cargo and supplies to ISS, the Altair lunar lander sending supplies to the Moon, the Orion plus Altair on the the way to the Moon.
The new details involve the configuration with the four SSMEs beneath the ET. Engineering has determined that a change from four engines mounted in a straight line between the two SSSRBs to the four engines mounted in a diamond pattern has certain advantages. First, the thrust structure weighs less. The thrust structure transfers the engine thrust to the external tank. The weight savings could add as much as one ton to the payload capability. Second, the plumbing carrying liquid oxygen and liquid hydrogen to the engines is simpler than in the straight line version. All this adds up to less the cost.
Looking from lower right to upper left, the four configurations are: