CEV Service Module, Boosters and CLV

The CEV service module will also be cylindrical. It will
cover and protect the heat shield of the CEV capsule while in
flight and provide power, propulsion, and attitude control.
The service module will be jettisoned prior to re-entry.

Some features of the service module include:

* A single engine propulsion, which will use slightly
more efficient methane/oxygen fuel rather than the hypergolic
mixture of Apollo SM (hydrazine/nitrogen tetroxide).
Methane/oxygen fuel has a greater specific impulse than
hydrazine/nitrogen tetroxide, which means a longer burn time
for the same mass of propellant and greater velocities. In
the future, it may be possible to make methane fuel from
components on the moon and Mars to fuel this type of vehicle.

* A larger fuel capacity to make different lunar orbits
and landing sites possible.

* Solar panels to generate electricity to supplement the
energy from the fuel cells.

* Conduits containing liquid ammonia or water/glycol
mixtures to transfer heat to radiators so it can escape into
space. In outer space, the difference in temperature between
sunlight and shade is about 400 degrees Fahrenheit. This
uneven heating causes thermal stress on the metals in the
spacecraft's structure. To counter this effect, the Apollo
spacecraft rotated on its axis when going to the moon to
allow solar radiation to heat the spacecraft evenly (the
"barbecue roll maneuver"). The CEV will probably do the same.

* Attitude control with thrusters similar to the Apollo.

The Apollo required a massive launch vehicle (Saturn V) to
lift both crew and payload. The shuttle's main engines needed
to supply large amounts of thrust to the vehicle for the same
reasons. The CEV launch booster, will only lift the crew, not
heavy payloads. Because of this, the CEV booster can be
smaller than the Apollo and space shuttle boosters.

The first stage of the CEV booster will be a solid rocket
booster (SRB) named Ares I, which will be similar to the one
on the space shuttle. The second stage will consist of
a single space shuttle engine fueled by liquid hydrogen and
oxygen tanks. Neither stage will be recovered or re-used (the
shuttle SRBs were both recovered and re-used).

Manned space exploration requires placing both astronauts and
payloads into orbit. Past vehicles have combined humans and
payloads on the same rocket, but the CEV concept has
separated these functions. The CLV will lift heavy payloads,
like lunar landers, moon transfer stages and space station
components. If necessary, the CLV can also be configured to
launch humans.

The CLV will consist of two stages:

* The firs t stage will have five main engines fueled by
liquid hydrogen and liquid oxygen (named Ares V)
* The second will have either a shuttle main engine or
an Apollo J-2 engine, also fueled by liquid hydrogen and
liquid oxygen.