Space Shuttles destined for equatorial orbits are launched from
the KSC, and those requiring polar orbital planes will be launched
Orbital mechanics and the complexities of mission requirements,
plus safety and the possibility of infringement on foreign air and
land space, prohibit polar orbit launches from the KSC.
Kennedy Space Center launches have an allowable path no less than
35 degrees northeast and no greater than 120 degrees southeast.
These are azimuth degree readings based on due east from KSC as
A 35-degree azimuth launch places the spacecraft in an orbital
inclination of 57 degrees. This means the spacecraft in its orbital
trajectories around the Earth will never exceed an Earth latitude
higher or lower than 57 degrees north or south of the equator.
A launch path from KSC at an azimuth of 120 degrees will place
the spacecraft in an orbital inclination of 39 degrees (it will
be above or below 39 degrees north or south of the equator).
These two azimuths - 35 and 120 degrees - represent the launch
limits from the KSC. Any azimuth angles further north or south would
launch a spacecraft over a habitable land mass, adversely affect
safety provisions for abort or vehicle separation conditions, or
present the undesirable possibility that the SRB or external tank
could land on foreign land or sea space.
Launches from Vandenberg have an allowable launch path suitable
for polar insertions south, southwest and southeast. The launch
limits at Vandenberg are 201 and 158 degrees. At a 201-degree launch
azimuth, the spacecraft would be orbiting at a 104-degree inclination.
Zero degrees would be due north of the launch site, and the orbital
trajectory would be within 14 degrees east or west of the north-south
pole meridian. At a launch azimuth of 158 degrees, the spacecraft
would be orbiting at a 70-degree inclination, and the trajectory
would be within 20 degrees east or west of the polar meridian. Like
KSC, Vandenberg has allowable launch azimuths that do not pass over
habitable areas or involve safety, abort, separation and political
Mission requirements and payload weight penalties also are major
factors in selecting a launch site.
The Earth rotates from west to east at a speed of approximately
900 nautical miles per hour (1,035 mph). A launch to the east uses
the Earth's rotation somewhat as a springboard. The Earth's rotational
rate also is the reason the orbiter has a cross-range capability
of 1,100 nautical miles (1,265 statute miles) to provide the abort-once-around
capability in polar orbit launches.
Attempting to launch and place a spacecraft in polar orbit from
KSC to avoid habitable land mass would be uneconomical because the
Shuttle's payload would be reduced severely-down to approximately
17,000 pounds. A northerly launch into polar orbit of 8 to 20 degrees
azimuth would necessitate a path over a land mass; and most safety,
abort, and political constraints would have to be waived. This prohibits
polar orbit launches from the KSC.
NASA's latest assessment of orbiter ascent and landing weights
incorporates currently approved modifications to all vehicle elements,
including crew escape provisions, and assumes a maximum Space Shuttle
main engine throttle setting of 104 percent. It is noted that the
resumption of Space Shuttle flights initially requires more conservative
flight design criteria and additional instrumentation, which reduces
the following basic capabilities by approximately 1,600 pounds:
Kennedy Space Center Eastern Space and Missile Center (ESMC)
satellite deploy missions
The basic cargo-lift capability for a due east (28.5 degrees) launch
is 55,000 pounds to a 110-nautical-mile (126-statute-mile) orbit
using OV-103 (Discovery) or OV-104 (Atlantis) to support a 4-day
satellite deploy mission. This capability will be reduced approximately
100 pounds for each additional nautical mile of altitude desired
by the customer.
The payload capability for the same satellite deploy mission with
a 57-degree inclination is 41,000 pounds.
The performance for intermediate inclinations can be estimated
by allowing 500 pounds per degree of plane change between 28.5 and
If OV-102 (Columbia) is used, the cargo-lift weight capability
must be decreased by approximately 8,400 pounds. This weight difference
is attributed to an approximately 7,150-pound difference in inert
weight, 850 pounds of orbiter experiments, 300 pounds of additional
thermal protection system and 100 pounds to accommodate a fifth
cryogenic liquid oxygen and liquid hydrogen tank set for the power
reactant storage and distribution system.
Vandenberg Air Force Base Western Space and Missile Center
(WSMC) satellite deploy missions
Using OV-103 (Discovery) or OV-104 (Atlantis), the cargo-lift
weight capability is 29,600 pounds for a 98-degree launch inclination
and 110-nautical-mile (126-statute-mile) polar orbit. Again, an
increase in altitude costs approximately 100 pounds per nautical
mile. NASA assumes also that the advanced solid rocket motor will
replace the filament-wound solid rocket motor case previously
used for western test range assessments.
The same mission at 68 degrees inclination (minimum western
test range inclination based on range safety limitations) is 49,600
Performance for intermediate inclinations can be estimated by
allowing 660 pounds for each degree of plane change between inclinations
of 68 and 98 degrees.
Landing weight limits
All the Space Shuttle orbiters are currently limited to a total
vehicle landing weight of 240,000 pounds for abort landings and
230,000 pounds for nominal end-of-mission landings.
It is noted that each additional crew person beyond the five-person
standard is chargeable to the cargo weight allocation and reduces
the payload capability by approximately 500 pounds. (This is an
increase of 450 pounds to account for the crew escape equipment.)