6.4 Reliability and Maintenance:

Reliability:

   The  MMVS vehicle system is to be designed with the most possible reliability and  redundancy and to very high tolerances. Redundancy of functional elements is  used to counteract the effects of failure on the mission. The majority of the  critical components contain some sort of redundancy, including power, thermal  control, life support and communications. Redundancies consist of two types,  active and stand-by. In stand-by redundancy, the redundant element is switched  into operation when a failure occurs in the main unit. A transfer mechanism that  switches to the redundant component after a failure has been detected is of  great importance.  An active  redundant element is operational for the entire mission, where the total load  and stress is shared.

Maintainability:

   All  integral systems are to be made accessible internally by the crew. Astronauts do  replacement of the functional elements that have a life span less than the  mission duration from the interior of the spacecraft. The crew will be fully  trained on all repair procedures and will have access to the necessary onboard  support equipment. If there exists a problem on the exterior, which is less  likely due to minimal component use, a robotic arm will be deployed. There is a  system operating at all times to provide amplified fault diagnosis and repair  information both to crew members in the event of a failure during the mission  and to personnel of the mission control. The computer system will analyze all of  the integral parts of the vehicle from in-cabin pressure to fuel lines and  engine temperature. This system will consist of a small portable computer with  repair information stored on CD-ROM and hard disk for any procedural updates  from mission control. If a system becomes over stressed, it will be noticed and  maintenance action can be taken with operations that are planned with minimal  disruption of the mission objectives.