Concerning the redundancy of all mission equipment, we have adhered to NASA policy requiring double redundancy for all mission critical factors and triple redundancy for all life critical factors. The redundancies are most clearly explained by breaking down the entire mission into two different phases, transport and surface. We define a transport phase to be any period of time spent traveling to or from mars, for example the T.M.I. journey. The surface phase is simply the period of time spent inhabiting the mars surface.
Redundancy aspects of the transport phase
During the trip to and from mars food will be kept in a triple redundant quantity. We saw no other alternative since food can not be produced at any time during the mission. Shelter is defined as in the conventional notion, an area sheltered from the elements of space. Under normal conditions shelter will be provided by the habitat. Oxygen is redundant in both the amount produced and by the CO2 to Oxygen converters. Double redundant power for all systems is provided by with a third redundancy for minimum backup power.
Redundancy aspects of the surface phase
Power will be generated on the surface from batteries, 6 solar panels and 2 nuclear generators. This power availability provides more than triple redundancy for life critical needs and double redundancy for mission critical needs on the surface. Double redundant mission critical power is a result of having two nuclear generators. In case of a failure regarding both generators, solar panels will produce enough power to maintain life critical systems.
The three alternatives for making the oxygen supply available during the mission are the use of oxygen converters from scrubbing CO2 after combusting chemical fuel and conventional oxygen tanks.
The Communication Systems
The Mars mission will contain three communication relay satellites. This will enhance the standard communications unit so there would be no blackout period. Two communication relay satellites will orbit Mars, this will allow the crew to communicate with earth 24-hours a day. The third satellite will essentially follow the earth around the sun which will enable the crew to communicate during the short black out period which would have occurs in January of every odd-numbered year.
The Space Shuttle
"The two solid rocket boosters are each 149.1 feet (45.4 meters) high and 12.2 feet (3.7 meters) in diameter. Each weighs 1,300,000 pounds (589,670 kilograms) when on the launch pad. Their solid propellant consists of a mixture of Aluminum powder, Ammonium Perchlorate powder, and a dash of Iron Oxide catalyst, held together with a polymer binder. They produce about 3.1 million pounds (13.8 million newtons) thrust each for the first few seconds after ignition, before gradually declining for the remainder of a two-minute burn. Together with the three main engines on the orbiter, this provides a total thrust of over 7.3 million pounds (32.5 million newtons) at liftoff.
The external tank is actually three components in one: a liquid oxygen tank located in the forward position; a liquid hydrogen tank located aft; and an intertank assembly that connects the two propellant tanks and houses the forward solid rocket booster attachment points. The external tank weighs approximately 1,655,600 pounds (751,000 kilograms) when filled with propellants and 66,000 pounds (29,900 kilograms) when empty.