Almost half a century later: what will Luna-25 do?
Russia is returning to the Moon after almost half a century: on August 11, for the first time since 1976, a Russian-made spacecraft went to the Earth's natural satellite. We are talking about the automatic interplanetary station (AMS) "Luna-25", which will have to solve two difficult tasks at once - to work out the technology of soft landing and explore the soil in the region of the South Pole of the Moon, as well as its exosphere.
The last time a Russian spacecraft made a soft landing on the Moon was 47 years ago. It was the Luna-24 station , which launched on August 9, 1976 from the Baikonur Cosmodrome using the Proton-K / D launch vehicle, successfully landed on the surface of the satellite and sent home 170 grams of lunar soil . Thanks to this mission, scientists first obtained evidence of the presence of water on the Moon, which was independently confirmed in the 1990s by specialists from two American projects, Clementine and Lunar Prospector.
Following Luna-24, an automatic station from the same series was supposed to go to the celestial body, but starting from 2015, the launch of the mission was constantly postponed. It was possible to get things off the ground only on April 12, 2021 , when President Vladimir Putin, during a visit to the Vostochny cosmodrome, made it clear that Russia intends to resume its lunar program, including continuing to explore the satellite with space probes.
And the first in line in this list is Luna-25 . What tasks she has to solve, what is the complexity of a soft landing and why the South Pole of the Earth's natural satellite continues to attract the attention of leading space powers, Pro Cosmos was helped to understand by Nathan Eismont, candidate of technical sciences, leading researcher at the Space Research Institute (IKI) of the Russian Academy of Sciences .
From Vostochny to Boguslavsky
The successful completion of ground tests of the Luna-25 spacecraft, which in August of this year was entrusted with implementing the first mission in the history of modern Russia to the satellite of the same name, became known on July 13 . Then the press service of the NPO named after S. A. Lavochkin, where the probe was manufactured, reported that the ground control complex was already ready to start flight testing.
Since that moment, the lunar station has passed all the necessary electrical and pneumovacuum tests, demonstrating positive results . The last preparations before the actual launch fell on the first week of August : first, Luna-25 was docked to the Fregat upper stage , and after that, the general assembly of the Soyuz-2.1b launch vehicle was completed .
The matter remained small: on August 8, the entire structure, consisting of a launch vehicle, an upper stage and an automatic interplanetary station, was taken out of the assembly and test complex and installed on the launch pad of site 1C of the Vostochny cosmodrome. Three days later, a long-awaited event occurred: on August 11 at 02:10:57 Moscow time, Soyuz-2.1b launched the first Russian lunar AMS into space.
But this is only a small part of the path that Luna-25 has to overcome in order to find itself on the Earth's satellite of the same name. According to experts, the total flight time from our planet to the Moon will be 10-12 days : during this time, the device will have to go through several stages , and the first of them began already nine minutes after the launch of the launch vehicle, when Soyuz-2.1b delivered the upper stage with the station to the suborbital trajectory .
The first inclusion of the marching propulsion system "Fregat" was transferred to an orbit with a height of about 200 kilometers , the second inclusion of the engine sent "Luna-25" on a flight trajectory to the Earth's satellite. After the separation of the automatic station, the upper stage went into a reference orbit, while the spacecraft itself continued to move towards its destination.
During the flight, Luna-25 will perform two orbital corrections: the first was performed approximately 36 hours after launch, while the second is expected to occur the day before reaching the lunar orbit. On Wednesday, August 16 , the station will approach the Earth's satellite, after which it will be braked by the engine and transferred to a circular circumlunar orbit with a height of 100 kilometers - this will begin the third stage of its flight, which will last three days.
After that, Luna-25 will start landing: with the help of the main braking engine, the device will be transferred to a lower orbit with a height of 18 kilometers , and then the distance between the station and the Moon will be reduced to about two kilometers . The next step of the AMS will take a vertical position relative to the surface of the Earth's satellite and, finally, on August 21 , it will make a soft landing north of the Boguslavsky crater.
"A soft landing is not an easy task"
Experts note that the landing is a critical stage of the lunar mission. After all, for the first time in the history of astronautics, an automatic station will have to land on the moon in the near-polar region of the Moon with a complex terrain : in this area, the top layer of soil (polar regolith) contains a high content of volatile compounds , primarily water.
Therefore, when choosing a suitable location, Russian scientists took into account several aspects at once, taking into account the highest concentration of water, potential technical limitations, the possibility of obtaining information from the device and the presence of a relatively flat area. In total, they analyzed 12 points , but in the end, the plain north of the Boguslavsky crater was chosen as the main landing area, and the places south of the Pentland A crater and southwest of the Manzini crater were chosen as backup areas .
To make a soft landing, Luna 25 must descend at a constant low speed , and this process will be monitored by a Doppler meter specially designed for the mission. In addition, at the moment of landing on the moon, four video cameras will turn on - with their help on Earth they will be able to determine where and under what conditions the spacecraft lands.
It is worth noting that previously automatic and manned landing vehicles, developed by both domestic and foreign scientists, landed on the moon in temperate latitudes - closer to the equator . At the same time, so far only three countries have managed to carry out a successful soft landing on the moon - the USSR, the USA and China. Recent attempts by individual states to add to this list have ended in failure.
For example, in 2019, the Israeli Bereshit probe failed to complete the first non-state expedition to the Moon: on the night of April 11-12, the apparatus crashed on the lunar surface due to the failure of the main engine.
In November of the same year, India made an attempt as part of its second lunar mission, Chandrayaan-2 , but during the lunar landing, the Vikram landing platform deviated from the optimal trajectory and stopped transmitting telemetry. As a result, not only the lander was lost, but also the Pragyan lunar rover . Only the Chandrayaan-2 orbiter remained operational.
In April 2023, the same fate befell the Japanese module Hakuto-R , which almost reached the natural satellite of the Earth, but at the time of the final approach, communication with it was lost.
“As the recent experience of our colleagues from Japan and Israel and India has shown, a soft landing is not a very simple task,” said Nathan Eismont. — We can say that we already had a successful experience of such landings. But since then there has been almost a half-century break, and during this time the whole world has moved away from the analog control principles used in those years, including spacecraft. That is, now it is impossible, simply relying on that successful experience, to create a soft landing system.
As for the South Pole of the Moon, it is really more difficult to land on the moon in this area than in the equatorial region, the interlocutor of Pro Cosmos agreed. At the same time, he believes that the landing site is not so important - in any case, the reasons for the failures of his colleagues were not in this. After all, digital technology, as you know, has its advantages and disadvantages.
Looking for water
In addition to working out the soft landing technology, the Luna-25 automatic interplanetary station is also called upon to conduct a series of scientific studies of the South Pole of the Moon. To do this, the spacecraft will deliver 30 kilograms of payload to the polar region, including eight unique instruments designed to study the composition, structure, and physical and mechanical properties of the lunar regolith, as well as the near-surface dust and plasma exosphere.
One of the tools that the AMS will "operate" with is the lunar manipulator , capable of sampling soil at a depth of 15-30 centimeters . Up to 30 samples up to two cubic centimeters each are expected to be taken. In addition, a soil analyzer is installed on Luna-25 , which makes it possible to study the composition of the regolith. Upon completion of the mission, all collected data and research results carried out by the apparatus on the surface of the Moon will be transferred to Earth.
“Compared to its predecessors, Luna-25’s technological tasks are, frankly, simpler: there is no need to return soil to Earth. True, there is a manipulator for soil analysis on site. In addition, the methods of nuclear planetology are used on Luna-25. That is, detectors of neutrons and gamma rays caused on the surface of the Moon by a stream of cosmic rays. This allows you to explore the rock of the Moon in situ. Moreover, to depths of meters, ”Nathan Eismont drew attention.
At the same time, our country is not the only player in the space industry that has set its sights on the polar region of the moon. A month before the start of the Russian mission, India also launched its automatic lunar station. We are talking about the Chandrayaan-3 spacecraft , which has already entered the lunar orbit. However, the Indian colleagues are planning to land on the moon two days after the landing of Luna-25.
If everything goes according to plan, then on August 17, the landing module of the Indian Vikram station will separate from the orbital one and on August 23 will also land in the South Pole region. After that, the Pragyan lunar rover will be launched from Vikram , which will have to collect data on the composition of the soil in one lunar day (about 14 Earth days) and conduct a series of experiments.
So why exactly the South Pole? One answer to this question is simple: water. After all, if it is discovered, then in the course of further space missions, specialists will no longer have to deliver water from Earth - it will be possible to obtain hydrogen and oxygen from it right on the spot, which is necessary both for the life of astronauts and for the creation of rocket fuel. And the greatest chance of finding water is to look for it in the region of the poles, since the Sun never looks at the bottom of their craters.
“The fact is that the axis of rotation of the Moon is almost perpendicular to the plane of the Moon's orbit. Unlike the Earth, in which the axis of rotation is inclined to the plane of the Earth's orbit by 67 degrees, instead of 90 for the Moon. This means that water, perhaps, has been preserved in these craters since ancient times by astronomical standards, and in terms of isotopic composition it may differ from terrestrial water. And since when? Since the days of the so-called heavy bombardment, when it was brought to the moon by comets, ”says Eismont.
In 2020, an article was published in the American journal Scientific American , which noted that the launch of the Luna-25 automatic station would mark the restoration of Russia's Soviet potential in the field of studying the Earth's satellite after almost 50 years. Eismont, in turn, believes that the successful implementation of the mission allows our country, as well as other participants in the lunar race, to move towards "more ambitious projects, including a manned expedition to Mars ."
“The moon is an excellent testing ground for developing the technologies necessary for this,” summed up the interlocutor of Pro Cosmos.
Along with Luna-25, Russia is developing the next two devices of this series - Luna-26 and Luna-27 . The launch of the first is scheduled for 2027 - the orbiter is designed for remote research of the Earth's satellite. Luna 28 is a more complex landing station with a drilling rig, it will be able to accommodate more scientific equipment.
