The saying “Space is hard” applies here.
This maxim has been proved time and again as humans and their machines have tried to launch beyond Earth. Recent attempts to touch down on the moon — a feat first accomplished nearly 60 years ago by the former Soviet Union’s robotic Luna-9 probe — have been particularly fraught with failure.
For the first time ever, an Indian spacecraft successfully landed the moon’s surface on August 23.
Chandrayaan-3, launched on 14 July, delivered the Vikram lander and Pragyan robot to the south pole region of the moon. Thought to contain water ice (SN: 5/24/22).
These reservoirs would be a vital source of drinking water and hydrogen fuel for future inhabitants of the moon. This was the country’s second attempt at a lunar landing, following the crash of Chandrayaan-2’s lander in 2019 (SN: 9/20/19).
Vikram’s landing catapults India into a rarefied group of nations that have successfully made a “soft landing” — as opposed to an uncontrolled “hard landing” — on the moon: the United States, the former Soviet Union and China (SN: 12/16/19). The recent failures are followed closely by the success of this mission.
On August 19, Russia’s Luna-25 lander crashed into the moon. The car-sized spacecraft had been orbiting the moon for several days when, according to Russia’s space agency, communications were lost after the craft fired its engines during prelanding maneuvers. Luna-25 was bound for the vicinity of Boguslavsky crater near the moon’s south pole, where it would have studied the moon’s surface and tenuous atmosphere.
Earlier this year, on April 25, Japan’s Hakuto-R Mission 1 lander also crashed on the moon’s surface. According to ispace, the private company that developed the mission, the crash occurred because onboard software miscalculated the lander’s altitude above the lunar surface. The lander’s mission was to land in Atlas crater, on the nearside moon, and collect lunar dust.
The moon is a relatively distant object at just over 400,000 km. A challenging target for spacecraft that are trying to land (SN: 4/11/19). That’s in large part because our nearest celestial neighbor lacks an atmosphere.
The go-to mechanism for slowing down a descending object on Earth — a parachute — is therefore useless, says Dave Williams, a lunar and planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md. “The only way to slow yourself down is with rockets.” That’s where things get tricky, he says, since firing a rocket means controlling its orientation and thrust, among other things.
The moon’s gravity, while only roughly one-sixth that of Earth’s, is strong enough to have a deleterious effect on a crippled spacecraft in free fall, Williams says. (Spacecraft landing on a comet or asteroid have it easier because those bodies’ gravitational fields are generally so weak there’s little danger of a crash.)
There’s also the challenge of determining a safe landing site. Williams says that an area which appears flat from orbit may be littered by boulders and other obstacles. A spacecraft’s software must be capable of evaluating the terrain on its own.
Relying on human operators back on Earth isn’t feasible, Williams says, because there’s too long a lag in communications due to the finite speed of light. “You’re always 2.5 seconds behind.”
Japan will again try to reach the moon on August 26. The country’s space agency is slated to launch its Smart Lander for Investigating Moon, or SLIM, mission from the Tanegashima Space Center. No landing date has been announced, but if all goes well, the probe — designed as a technology demonstration — will eventually touch down near Shioli crater on the nearside of the moon.
