Trans Lunar Injection

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Trans Lunar Injection (TLI) is a term describing the propulsion maneuver used to set a spacecraft on a trajectory which will intersect the Moon.

The spacecraft is usually in a parking orbit around Earth at the time of TLI.

The maneuver is usually performed by a rather large rocket engine. On the Apollo missions it was performed by the restartable third (S-IVB) stage of the Saturn V rocket. This particular TLI burn lasted approximately 346 seconds, providing 10,000 to 10,600 ft/s (3.05 to 3.25 km/s) of delta-v, at which point the spacecraft was travelling at approximately 10.95 km/s (24,500 mph or 39,420 km/h).

The burn is timed so that the mid-point of the TLI is opposite the moon (or more precisely, the moon's location upon arrival).