Japan's complex landing on the Moon yesterday, which the Japanese space agency took almost two hours to explain, is the latest example of the complexity of returning to the satellite after the ship has landed. Moon 9 in 1966. The Moon lacks air, so parachutes cannot be used. Only rocket engines, the thrust of which must be adjusted to reach the ground exactly with zero speed or almost. It is not easy to land on it. Radar or laser variants must be used to measure the altitude second by second and ration the scarce fuel (every kilo counts) so that it does not run out prematurely. And land without horizontal displacement to avoid risking a rollover. All that and trust that the impact will not damage the delicate instruments on board.
Such are the problems that NASA has decided to postpone the Artemis program plans for a year, postponing the return of humans to the lunar surface until 2026, at the earliest. But it is the uncrewed devices, landers of all kinds, that have failed again and again until today: in the last decade, no private attempt has been successful and only two nations, China and India, have achieved their goal without accidents. .
What happened to the last failed probes?
The Chandrayaan 2 crashed due to a bug in the descent control software. He Moon 25 Russian was the victim of a failure in its braking system, which remained in motion for more than twice as long as expected. He Beresheet Israeli, due to an inopportune reset of its central computer at such a low altitude that it did not give it the opportunity to recover and restart the engine. The Japanese Hakuto-R It suffered confusion when its radar detected the sudden rise of a crater wall. She was still 5 kilometers above the ground, but interpreted the sudden change as an imminent landing and shut down the engine. In it Pilgrim, A simple valve stuck “open” injected so much pressure into the fuel tank that it caused a crack and a corresponding loss of propellant and mission failure.
Only the third Chandrayaan It accomplished its objective, landing in the southern polar zone of the Moon. The Indian engineers, chastened by their previous bad experience, had rewritten many of the landing routines, trying to overcome Murphy's curse. His motto: “Anything that can go wrong, will go wrong.” And under that premise they succeeded in becoming the fourth country to reach the Moon.
Didn't they crash 50 years ago?
Not quite. It took the Soviet Union a dozen attempts to land the first capsule on the Moon. And it was a very simple vehicle that also landed somewhat abruptly, protected by airbags.
The first American operations were also a string of failures. The series of Ranger He did not achieve results until the seventh attempt (and they were ships destined to be destroyed on impact with the ground). On the contrary, NASA succeeded first time in achieving a soft landing with the probe Surveyor 1. But two of the six devices that followed failed.
The exception is the Chinese lunar program, which has achieved an impressive record of successes, always on the first try. They have landed on the Moon and Mars, have deposited rovers there and have managed to bring samples of regolith to Earth in a very complex maneuver reminiscent of the Apollo operations, except that it has been carried out by autonomous robots.
Can't the moon landing be directed from Earth?
The moon landing is an operation that cannot be controlled from Earth. Radio signals take a little more than a second to reach us from the Moon, and the same goes for the orders that can be sent to the ship. Those three seconds of delay represent too long a reaction time in operations whose success is a matter of tenths of a second. In that sense, the lunar ships must be autonomous and make their own decisions based on how the descent progresses.
Why did it take days before and now months?
The Apollo missions arrived there in three days. But now rockets of lower power than the colossal ones are used saturn 5. And to squeeze maximum performance from them, low-energy trajectories are used that require less fuel. The price to pay is longer flight time.
The Apollos followed a direct route to the Moon; Current probes describe very elongated ellipses, whose apogee increases little by little based on short ignitions of their propellant, which is usually low power. Sometimes, the trajectory exceeds the orbit of the Moon, extending up to more than a million kilometers and playing with the gravitational interactions of the Earth, Moon and Sun. If the calculations have been correct, when it passes through the vicinity of the Moon again, It will capture it without spending much fuel on braking.
What happened to the 'SLIM' ship?
The ship SLIM that reached the Moon yesterday is an engineering test. I was trying to achieve a precision descent, that is, with an error of less than one hundred meters, which we still do not know if it has worked. Its navigation system had to locate the exact location by comparing the craters seen by its camera with those on a map stored in the computer's memory. Algorithms based on artificial intelligence had to allow both area identification and lateral movements to avoid obstacles.
The chosen terrain was complicated: a 15-degree slope, which would make even a traditional probe overturn. SLIM It had a kind of five-legged landing gear attached to its side. This meant vertical descent, but it would drop to its side as soon as it made contact with the ground to deploy its instruments and, in particular, the pair of rovers which he transported as passengers.
What robots were on board the SLIM?
Two different models are on board the ship. One of two kilos, with movement in jumps and capable of communicating directly with the Earth. The second is the size and weight of a tennis ball. Once on the ground, it opens into two halves that act as wheels and at the same time deploys a pair of mini-cameras. So small in size that it does not even have a communications antenna, so the images of its movement would be sent through the other robot, with which it is connected by Bluetooth.
If that robot looks like a transformer It is because it inherits that Japanese tradition. He designed it and built it in a Japanese toy factory commissioned by the space agency. An identical one was on board the unsuccessful Hakuto-R. If this time the moon landing had gone well, the little gadget had many numbers to become the fashionable toy.
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