How the Orion CEV Will Work

Although the space shuttle is still a technical marvel, the
fleet is aging and has become increasingly expensive to
operate. Recent problems with foam insulation have exposed
crews to danger, rendered it unsafe to fly, and caused NASA
to ground the entire fleet. NASA needs a vehicle that is
capable of carrying crew and payloads to Earth orbit, the
moon and Mars. With future exploration in mind, NASA is
designing a new vehicle.

NASA's new spaceship, the Orion Crew Exploration Vehicle,
will actually consist of two ships:

* The Crew Exploration Vehicle (CEV) will transport four
to six astronauts.
* The Cargo Launch Vehicle (CLV) will lift heavy payloads
and astronauts when necessary.

The Orion will use proven technologies from the Apollo and
space shuttle programs. They will also be safer and more
versatile for long-term space exploration.

CEV Basics

NASA has selected Lockheed Martin to design and build the
Orion. Main systems (such as power, navigation, life support,
communications, and computers) will be more advanced versions
of those on the Apollo and the space shuttle.

The CEV will consist of three basic parts:

* A capsule to hold the crew.

* A service module to hold the main propulsion system,
power systems, and attitude controls. Attitude refers to how
the spacecraft is oriented in space (x, y, and z directions
or pitch, roll, yaw axes). Apollo used four units of four
thrusters mounted on the service module for this task, while
the shuttle uses reaction control thrusters located on the
nose and aft sections.

* A booster to lift the CEV into Earth orbit.

For lunar landing missions, there will be a special module.

The capsule will be cone-shaped like the Apollo command
module, because it is more aerodynamic than the shuttle.
Instead of re-entering the atmosphere of Earth orbit at 8
kilometers per second (like the shuttle), the CEV will
re-enter the atmosphere from the higher velocities of lunar
travel, at 11 kilometers per second.

Besides shape, the CEV crew capsule has several other things
in common with the Apollo, along with a few differences:

* The larger diameter (16.5 feet, or 5 meters, instead of
3.9 feet) will hold more crew and cargo.

* The CEV aft heat shield will be ablative, meaning that
it will boil away. Apollo used a single, multi-layered aft
heat shield made of aluminum and epoxy resin that ablated as
it absorbed the heat of re-entry. (It was designed to be used
only once, just like the rest of the command module.) The
shuttle uses ceramic thermal tiles, thermal blankets, and
reinforced carbon resins to absorb the heat. However, this
concept has proven to be more difficult to service than its
theoretical design. The CEV heat shield will be replaceable
up to 10 times and last the design life of the vehicle.

* Air bags on the CEV will enable both land recoveries
and sea recoveries. All of the Apollo's recoveries were ocean
splashdowns.

* The CEV's position atop the launch booster puts it out
of the way of falling debris like pieces of foam or ice.

* An escape tower -- a small rocket that lifts the
command module off the booster in the event of a launch
failure -- is one of the CEV's unique features. This
mechanism is safer than the shuttle's abort procedures.