Fifty years ago, on July 20, 1969, Neil Armstrong and Buzz Aldrin landed on the Moon. It took more than eight years between the announcement and implementation of a manned moon landing, so it is not that easy to get from Earth to the Moon. But don’t you just need a powerful rocket to get to the moon? If not, How did the Apollo mission fly to the moon? Let’s find out.
“I believe that the United States should aim to land a man on the moon before the end of this decade and bring him back safely to Earth.” These were the words of US President John F. Kennedy on May 25, 1961. More than eight years passed before NASA implemented this bold plan.
During this time, the space agency not only developed the necessary technology for a flight to the moon, but it also had to find the best route to the Earth’s satellite. Because unlike on Earth, the start and endpoint in space change their position relative to each other during the journey. It is because everything is in constant motion. The earth revolves around itself and circles around the sun. And also the destination, in this case, the moon, revolves around the earth.
Couldn’t a rocket just fly straight from the earth to the moon? There is nothing physically against it. But for such a flight you would need an extremely strong rocket and a lot of fuel. So, the space scientists try to make optimal use of the gravitational pull of the celestial bodies and thus save energy.
Rockets are preferably launched near the equator and in the direction of Earth’s rotation. This alone makes the rocket travel at a speed of 1674 kilometers per hour. However, for a typical orbit around the earth at a height of 300 kilometers, a spacecraft must reach a speed of 28,000 kilometers per hour.
There are now different ways of getting from an earth orbit to a more distant place such as the moon, as energy-efficiently as possible. The one used during the trip to the moon was called the Hohmann orbit. It is based on minimum energy transfer but it takes more time.
To reach such an elliptical orbit leading to the moon, the spacecraft must be accelerated to a speed of around 40,000 kilometers per hour. The engines have to ignite at exactly the right moment so that the spacecraft aimed for the moon actually reaches the moving moon at the most distant point.
In the 1950s and 1960s, this flight maneuver was a technical and numerical challenge. Every smartphone today is millions of times superior to the NASA computers used for the Apollo missions. And to get into orbit around the Earth’s satellite or land softly on the moon, an even more complicated trajectory is required.
On September 12th, 1959, Lunik 2 was the first spacecraft to hit the moon. The first soft landing on the moon was achieved on February 3rd, 1966, by the Soviet Luna 9 probe, and on April 3rd of the same year, Luna 10 swung into orbit around the Earth’s satellite for the first time. On December 24th, 1968, Apollo 8 was the first manned spacecraft to reach the moon and orbit a total of ten times within twenty hours. And just seven months later, NASA’s Apollo 11 was the first manned moon landing.
Apollo 11 launched on July 16th, 1969, and reached orbit as planned twelve minutes later. The rocket orbited our planet one and a half times before heading for the moon. After 76 hours, Neil Armstrong, Edwin Aldrin, and Michael Collins reached the Earth satellite about 380,000 kilometers away. On July 19th, the astronauts swung into a lunar orbit. A day later, the lander disconnected, with Armstrong and Aldrin on board, and touched down on the surface of the moon a little later. On July 21st at 3:56 am Central European Time, Armstrong was the first person to walk on the moon, and twenty minutes later Aldrin followed. The first excursion to the lunar surface lasted two and a half hours. After about 21 hours on the moon, they went back, first to the Apollo spacecraft and then to Earth.
The Apollo astronauts’ journey to the moon took three days and four hours. Short flight time is a crucial criterion for manned missions because it means less radiation exposure for space travelers. In contrast, the flight time plays a minor role in unmanned probes. Flight routes that last for months but cost little energy are also conceivable. Such orbits usually lead far out of the earth-moon system and use the attraction of the sun to finally return to the moon. Instead of the powerful chemical based engines, electric drives can also be used. Another great advantage is that the spacecraft approaches the moon at a low relative speed, which means that only minor corrections are necessary to swivel into orbit around the earth’s satellite.
In total there have been 121 officially known attempts to fly to the moon. Of these, 55 failed in different ways, from explosions at launch to unplanned crashes on the moon. India has also sent chandrayaan II however the lander ‘Vikram’ crashed and one of the important missions could not be completed. However, 98% of the Indian lunar mission was considered complete as the study was to be conducted from the spacecraft in orbit.
As part of NASA’s Apollo program, there were nine flights to the moon and six successful moon landings from 1968 to 1972. A total of twelve people have so far entered the surface of the moon. In the coming decade, people could fly to the moon again. NASA is planning an orbit around the moon in 2022 with the new Orion spacecraft. And entrepreneur Elon Musk wants to fly his Starship spacecraft to the moon for the first time in 2023. Japanese billionaire Yusaku Maezawa has already booked tickets for himself and a group of six to eight invited artists for this trip.