Orion struggles to lose excess weight

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Ares 1 crew launch vehicle performance problems blamed for design changes

The initial version of NASA's Orion crew exploration vehicle, designed for International Space Station transport missions, is still more than 700kg (1,560lb) too heavy, months after its system requirements review.

The Block 1 Orion review in January evaluated a design identified as 604, and the vehicle was still 2,034kg above its weight target when the revised 605 version was reviewed weeks later.

Since February NASA's Project Orion office has been working on the 606 design with prime contractor Lockheed Martin. The goal is for this version to be 1,730kg lighter than the 605 to achieve the gross lift-off weight (GLOW) target of 28,934kg.

Weight reduction efforts saw the design team reduce the 605's propellant load by 1,525kg, which is 16% of its original mass.

"Based on current allocations there is still a mass challenge on the crew module, service module and spacecraft adaptor," says a Project Orion source.

Lockheed Martin was not available for comment. NASA denies any weight problems with Orion and says it expects to finalise the design and meet its GLOW target.

The actual 605 design masses are 6,579kg for the launch abort system 10,202kg for the crew module 4,045kg for a dry service module 9,186kg of propellant and 650kg for the spacecraft adaptor. The 605 Orion's GLOW is 30,664kg.

Mass reduction efforts have seen changes to the thermal protection system, back shell, air bag system, flight crew equipment, and a parachute resizing. Sources blame ongoing Ares I crew launch vehicle problems for forcing weight-related Orion design changes.