Launch Sites

Space Shuttles destined for equatorial orbits are launched from the KSC, and those requiring polar orbital planes will be launched from Vandenberg.

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 90 degrees.

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 considerations.

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 57 degrees.

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 pounds.

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.)