#### Location

Cocoa Beach, FL

#### Start Date

7-3-1966 8:00 AM

#### Description

The purpose of this presentation is to define the advantages which result from the use of the cis-lunar libration point LI as place of departure for descent to the Moon, as parking place for the Command Module and as place of rendezvous after take-off of the Lunar Landing Vehicle (LLV) from the Moon in regard to simplifying operations in lunar space and increasing the chances of success of lunar missions.

The Earth-Moon System contains five points where the initial forces are in exact balance with the gravitational forces from Earth and Moon and which remain in fixed position relative to the Earth-Moon configuration. These are the so-called libration points. The uniqueness of these positions has made them the subject of a number of studies beginning with those of La Grange in the 18th century.

For the restricted 3-body model, considering only Earth and Moon rotating around their barycenter, the location of the libration points is shown in Fig. 1. The orbits of the triangular points L4 and L5 are ellipses similar to that of the Moon's orbit, whose axes are tilted 60° from that of the Moon. The orbits of the co-linear points L^, L£, and L3 are ellipses concentric with that of the Moon. It should be noted that the triangular points are basically stable, whereas the co-linear points are basically unstable positions. The term "unstable" means that any displacement of a body from the exact location of the libration point will result in an everincreasing displacement away from the point.

The Role of the Cis-Lunar Libration Point in Lunar Operations

Cocoa Beach, FL

The purpose of this presentation is to define the advantages which result from the use of the cis-lunar libration point LI as place of departure for descent to the Moon, as parking place for the Command Module and as place of rendezvous after take-off of the Lunar Landing Vehicle (LLV) from the Moon in regard to simplifying operations in lunar space and increasing the chances of success of lunar missions.

The Earth-Moon System contains five points where the initial forces are in exact balance with the gravitational forces from Earth and Moon and which remain in fixed position relative to the Earth-Moon configuration. These are the so-called libration points. The uniqueness of these positions has made them the subject of a number of studies beginning with those of La Grange in the 18th century.

For the restricted 3-body model, considering only Earth and Moon rotating around their barycenter, the location of the libration points is shown in Fig. 1. The orbits of the triangular points L4 and L5 are ellipses similar to that of the Moon's orbit, whose axes are tilted 60° from that of the Moon. The orbits of the co-linear points L^, L£, and L3 are ellipses concentric with that of the Moon. It should be noted that the triangular points are basically stable, whereas the co-linear points are basically unstable positions. The term "unstable" means that any displacement of a body from the exact location of the libration point will result in an everincreasing displacement away from the point.