Lunar Exploration: What’s the Travel Time to Our Celestial Neighbor?

Since the first moon landing with Apollo 11, the question of the time needed to reach the Moon has intrigued and fascinated. If the distance between the Earth and the Moon is constant, approximately 384,000 kilometers, the time to travel it is far from fixed. Space missions vary depending on their primary objective, their technology and the strategic choices made by engineers. These durations reveal both the constraints of space physics and the technological advances that mark lunar exploration.

However, not all missions to the Moon follow this model as Livescience points out. The New Horizons probe, designed to explore Pluto, holds the record for the fastest trip to the Moon, with a journey time of just 8 hours and 35 minutes according to Ca M'Intereste. This was possible thanks to its extremely powerful propulsion and a direct trajectory. Unlike the Apollo missions, New Horizons did not attempt to stop on the Moon, which simplified its route.

In contrast, some modern missions favor longer journeys to save fuel or test new techniques. In 2019, the Israeli Beresheet probe took 48 days to reach the Moon. After orbiting the Earth several times to build up enough speed, it headed toward the satellite. Although the mission ended in a crash, it demonstrated that it is possible to use alternative, less fuel-intensive trajectories.

CAPSTONE, an experimental NASA mission launching in 2022, holds a unique lunar record. This small probe made the longest journey ever to the Moon. It took her 4.5 months to reach her goal, an unprecedented feat. Intended to test a new orbit, CAPSTONE is preparing the future Gateway station. To save fuel, the probe increased its orbits around the Earth. This method, although strategic, lengthened the trip. Through this approach, it demonstrated optimized use of resources.

The essential stages of a lunar journey

A journey to the Moon begins with a powerful launch, necessary to overcome Earth's gravity. About 60% to 90% of a rocket's weight is spent on fuel, which is essential for this first stage. Once the rocket is in Earth orbit, the spacecraft adjusts its trajectory to head towards the Moon. These adjustments, often made while conserving fuel, sometimes use gravitational forces to guide the ship.

The crossing to the Moon then depends on the mission objective. A habitable mission, like Apollo 11, requires a precise trajectory to reach lunar orbit in a controlled manner. On the other hand, missions like New Horizons, with no intention of stopping, favor speed and take direct trajectories.

During final approach, the ship must slow down to be captured by lunar gravity. This step is crucial for missions requiring a moon landing. In the case of the Apollo missions, a specific module separated from the main craft to descend to the lunar surface, while the main module remained in orbit to allow return.

Strategic choices dictated by objectives

Each space mission reflects the priorities of its time. The Apollo missions, in the 1960s and 1970s, aimed to demonstrate Man's ability to reach the Moon and survive there. The trade-off between speed and safety was essential, and expensive technologies like the Saturn V rocket helped ensure this performance.

On the other hand, recent missions, often unmanned, have placed emphasis on economic efficiency. Approaches like those of Beresheet or CAPSTONE show that it is possible to use extended trajectories to reduce costs. This is particularly relevant for experimental projects or small probes, where weight and fuel availability are major constraints.

Technological advances also make it possible to reduce durations for specific missions. Some modern rockets could reach the Moon in less than 14 hours if priority was given to speed, as New Horizons demonstrated. However, in scientific research, speed is rarely the sole determining factor.