ABOUT TRANS-LUNAR INJECTION (TLI)
Trans-Lunar Injection is the propulsive maneuver that places a spacecraft on a trajectory toward the Moon. It is performed from a parking orbit around Earth, typically LEO, and increases the spacecraft’s velocity to approximately 10.8 km/s. TLI was famously executed by the Saturn V’s S-IVB third stage during the Apollo program.
ORBITAL PARAMETERS
| Altitude (Min) | 185 km |
| Altitude (Max) | 384,400 km |
| Inclination | 28-51° |
| Orbital Period | N/A minutes |
| Orbital Velocity | 10.8 km/s |
| Delta-V Required | 3.1 km/s |
| Eccentricity | 0.97 |
| Category | Maneuver |
EQUATION / FORMULA
Δv_TLI ≈ 3.13 km/s from 185 km LEO
ADVANTAGES & DISADVANTAGES
ADVANTAGES
Direct and time-efficient path to Moon, well-characterized trajectory, proven technique
DISADVANTAGES
Requires precise timing, high propulsive energy, narrow launch windows
HISTORY
| Discoverer / Pioneer | NASA Apollo Program (1960s) |
| First Use | December 21, 1968 |
ALTITUDE CONVERSIONS (MIN)
| Kilometers | 185 km |
| Miles | 115 mi |
| Nautical Miles | 100 nmi |
TYPICAL PAYLOADS (3)
