v0.2 - 25-04-2020

Moon landings

Earth's moon is a body that has no atmosphere. Therefore a parachute landing is by definition, impossible. These landings are quite complex as one needs a high amount of control over the rocket engines to perform a safe landing. This can be seen by the motor used on the Apollo Lunar Lander which could be throttled to between 10 and 60% of full thrust. Another moon where landing attempts were to be made is Phobos, one of the Martian moons. Phobos is much smaller than the earth-moon, making landings even more difficult. One could compare a landing on the Martian moons more to an asteroid lander. Landings on these surfaces can be found on separate pages. 

Zond program was two distinct series of spacecraft with the goal of exploration of nearby planets and robotic circumlunar loop flights and recovery.

Zond 1-3

Zond 1-3 used the 3MV planetary probe. Zond 1 and 2 were sent on Venus and Mars flyby respectively. However, both missions lost communication before they reached near the planets. Zond 3 was sent on a lunar flyby mission and was the second spacecraft to click a picture of the far side of the moon. It continued to a trajectory of Mars and eventually lost communication.  

Zond 4-8

Zond 4-8 were the soviet test flights during the moon race. They used the Soyuz L1 spacecraft. These spacecraft travelled in a free-return trajectory around the moon without going into lunar orbit. They were designed to potentially carry two astronauts.

Zond 4 was a test mission launched away from the moon and was supposed to make a skip re-entry. However, the separation mechanism of the re-entry module and service module failed which resulted in the trigger of the self-destruct mechanism at an altitude of 10-15 km/s.

Zond 5 improved on its predecessor and was the first spacecraft to travel around the moon and land safely on Early. Zond 5 had a payload of few animals such as tortoises, flies, worms, etc who returned alive. Additionally, it also carried a full-sized human mannequin with radiation detectors. Due to a failure of attitude sensors, the spacecraft performed a water landing in the Indian Ocean as opposed to a planned land landing.

Zond 6-8 were uncrewed test missions aimed at improving the reliability and circled the moon and landed on earth. Zond 6 aimed at land landing but suffered from cabin depressurisation. This depressurisation led to electronics malfunction and the spacecraft prematurely jettisoned the parachutes and fired the soft-landing thrusters 5.3 kms above the surface. While the capsule crashed, it was still recovered in a one piece.  Zond 6 was a precursor to crewed missions, but a range of technical problems prevented that from happening.

Zond 7 was the first in the series to perform a successful land landing and Zond 8 performed a successful sea landing. Unfortunately, these were not followed by crewed missions. Zond missions also carried scientific payloads and gathered data on cosmic rays, solar winds, radio emissions and micrometeoroids.

The Ranger program often referred as the “Shoot and Hope” program in its early years were a series of spacecrafts launched to advance American space technology and map the surface of the moon. The program was divided into three key blocks. The spacecrafts within the three blocks were nearly identical to each other. The first 6 mission of the Ranger program failed and the missions 7,8 and 9 succeeded. The Ranger spacecrafts were launched on the Atlas rockets and used the Agena second stage to propel them towards the moon. All the missions in the Ranger program were designed to be impactors due to launcher limitations.

Ranger Block 1

Ranger 1 & 2 were meant to test the operations and reliability of the different subsystems. They both failed in low earth orbit after stabilisation issues.

Ranger Block 3

After the failure of the first two blocks, there was intense pressure to get things working. Therefore, redundancy was added in most key systems such as Power, Communications and TV Cameras. There were 6 cameras with different lenses on board block 3 spacecraft. The cameras fired one after the other to prevent excessive heat and could capture one image every 10 seconds. The communication equipment was designed to send pictures up to 0.2 second before impact.

Ranger 6 impacted the moon, but cameras failed. Ranger 7 was the first successful mission of the program and sent close-up pictures of the lunar surface in July 1, 1964. Ranger 7 had a successful impact and sent over 4000 pictures. Ranger 8 also had a successful impact and sent over 7000 pictures. Ranger 8 had a successful impact and sent over 5800 pictures

The LK lander was the Russian alternative to the Apollo LM. The Lk would have launched onboard the N1 rocket below the Soyuz module much like Apollo and LEM were launched. The LK would be extracted after launch and when the combination was around the moon a single cosmonate would space walk over to the Lk. The LK was quite a bit smaller, weiging between 5560 and 6525 kg compared to 15200 and 16400 for the LEM. The Lk only had one hypergolic engine that would be usedo n both ascent and descent flight. The landing legs would stay behind on the moon. Later LK landers would be upgraded to two crew members

The Chinese Lunar Exploration Program started with two successful orbital missions launched in 2007 and 2010. The second two missions, Chang'e 3 and 4 showed the Chinese ability to soft-land on the moon. Both landers were about 1200 including a 400 kg rover. Chang'e 3 worked for 959 days, where Chang'e 4 is active today. Before the sample return mission Chang'e 5, there was an intermediate demonstrator called Chang'e 5-T1. This mission was launched in October 2014 to test the re-entry leg of the sample return. The mission became the first successful skipping entry. Chang'e 5 was launched in November 2020, landed in December 2020 and returned to earth on the 16th of that month. The mission marked the first Lunar sample return since Luna 24. The earth entry probe resembled a scaled-down Shenzhou capsule, which in term resembles the Soyuz capsule. 

The follow-up mission, Chang'e 6, is scheduled for 2024 and will repeat the Chang'e 5 mission on the Lunar south pole.

In 2019 the Israeli company Isreal Aerospace Industries became the first commercial company to land a mission on the moon. The mission was launched onboard a Space X falcon 9 together with the PSN-6 satellite. The lander then used its own engines to fly to the moon where it entered a circular lunar orbit. Just before landing a gyroscope failed which could not be solved due to a sudden loss of communication. When communication was restored the capsule had already impacted the moon. At an altitude of 150, the 150 kg (dry mass) lander was still falling at 140 m/s. A second mission is planned for 2024 including a Moon and Mars lander. 

In 2019 India embarked on the ambitious mission to become the fourth nation to soft-land a lander on the moon. This lander was launched in July 2019 onboard a GSLV Mark-III as part of the Chandrayaan-2 mission. This mission contained an orbital module, lander and rover. After the Chandrayaan-2 mission entered lunar orbit, the lander detached and moved to a lower orbit. Unfortunately, the 1471 kg rover crash crashed due to a computer glitch. During the landing, the velocity was supposed to be changed from 1683 to 146 m/s. However, the capsule flew faster than expected, and thus the landing was hard. Even though the landing was unsuccessful, it impacted close to the predicted landing site. The lander and rover were destroyed upon impact. 

Overview of Lunar Landers

The table below shows the first moon landing attempts starting in 1958. As the moon has no atmosphere all of them used some form of propulsive deceleration if needed. From the table, it can be seen that the first landers used a much simpler impact strategy. This means the kinetic energy upon touchdown is higher, but the capsule is designed to handle this. This overview only contains missions that attempted a lunar landing and not failed missions that never started the landing operation.

v0.2 - 25-04-2020