Space Shuttle Requirements
The Shuttle will transport cargo into near Earth orbit 100 to
217 nautical miles (115 to 250 statute miles) above the Earth. This
cargo -- or payload -- is carried in a bay 15 feet in diameter and
60 ft long.
Major system requirements are that the orbiter and the two solid
rocket boosters be reusable.
Other features of the Shuttle:
- The orbiter has carried a flight crew of up to eight persons.
A total of 10 persons could be carried under emergency conditions.
- The basic mission is 7 days in space.
- The crew compartment has a shirtsleeve environment, and the
acceleration load is never greater than 3 Gs.
- In its return to Earth, the orbiter has a cross-range maneuvering
capability of 1,100 nautical miles (1,265 statute miles).
The Space Shuttle is launched in an upright position, with thrust
provided by the three Space Shuttle engines and the two SRBs. After
about 2 minutes, the two boosters are spent and are separated from
the external tank. They fall into the ocean at predetermined points
and are recovered for reuse.
The Space Shuttle main engines continue firing for about 8 minutes.
They shut down just before the craft is inserted into orbit. The
external tank is then separated from the orbiter. It follows a ballistic
trajectory into a remote area of the ocean but is not recovered.
There are 38 primary Reaction Control System (RCS) engines and
six vernier RCS engines located on the orbiter. The first use of
selected primary reaction control system engines occurs at orbiter/external
tank separation. The selected primary reaction control system engines
are used in the separation sequence to provide an attitude hold
for separation. Then they move the orbiter away from the external
tank to ensure orbiter clearance from the arc of the rotating external
tank. Finally, they return to an attitude hold prior to the initiation
of the firing of the Orbital Maneuvering System (OMS) engines to
place the orbiter into orbit.
The primary and/or vernier RCS engines are used normally on orbit
to provide attitude pitch, roll and yaw maneuvers as well as translation
The two OMS engines are used to place the orbiter on orbit, for
major velocity maneuvers on orbit and to slow the orbiter for reentry,
called the deorbit maneuver. Normally, two OMS engine thrusting
sequences are used to place the orbiter on orbit, and only one thrusting
sequence is used for deorbit.
The orbiter's velocity on orbit is approximately 25,405 feet per
second (17,322 statute miles per hour). The deorbit maneuver decreases
this velocity approximately 300 fps (205 mph) for reentry.
In some missions, only one OMS thrusting sequence is used to place
the orbiter on orbit. This is referred to as direct insertion. Direct
insertion is a technique used in some missions where there are high-performance
requirements, such as a heavy payload or a high orbital altitude.
This technique uses the Space Shuttle main engines to achieve the
desired apogee (high point in an orbit) altitude, thus conserving
orbital maneuvering system propellants. Following jettison of the
external tank, only one OMS thrusting sequence is required to establish
the desired orbit altitude.
For deorbit, the orbiter is rotated tail first in the direction
of the velocity by the primary reaction control system engines.
Then the OMS engines are used to decrease the orbiter's velocity.
During the initial entry sequence, selected primary RCS engines
are used to control the orbiter's attitude (pitch, roll and yaw).
As aerodynamic pressure builds up, the orbiter flight control surfaces
become active and the primary reaction control system engines are
During entry, the thermal protection system covering the entire
orbiter provides the protection for the orbiter to survive the extremely
high temperatures encountered during entry. The thermal protection
system is reusable (it does not burn off or ablate during entry).
The unpowered orbiter glides to Earth and lands on a runway like
an airplane. Nominal touchdown speed varies from 184 to 196 knots
(213 to 225 miles per hour).
The main landing gear wheels have a braking system for stopping
the orbiter on the runway, and the nose wheel is steerable, again
similar to a conventional airplane.
There are two launch sites for the Space Shuttle. Kennedy Space
Center (KSC) in Florida is used for launches to place the orbiter
in equatorial orbits (around the equator), and Vandenberg Air Force
Base launch site in California will be used for launches that place
the orbiter in polar orbit missions.
Landing sites are located at the KSC and Vandenberg. Additional
landing sites are provided at Edwards Air Force Base in California
and White Sands, N.M. Contingency landing sites are also provided
in the event the orbiter must return to Earth in an emergency.