[News Terms] 'Jungnyeok Pokchwap' (Gravity Capture), Without This You Become a Space Orphan

KARI: "Danuri Captured by Lunar Gravity... A True 'Lunar Orbiter' Orbiting the Moon"
Final Target Orbit 100km Above the Moon... Four More Maneuvers Planned

Photos of Earth (left) and the Moon sent by Danuri. Photo by Korea Aerospace Research Institute

[Asia Economy Reporter Han Seung-gon] South Korea's first lunar orbiter, 'Danuri,' has successfully completed the first gateway of its mission orbit insertion. With this, South Korea has taken a significant step toward joining the ranks of the world's seven major lunar exploration countries. The Korea Aerospace Research Institute (KARI) announced on the 19th that Danuri successfully performed the first mission orbit insertion maneuver around 2:45 a.m. on the 17th.

The first insertion maneuver was the most critical operation to ensure that Danuri was stably captured by the Moon's gravity and did not pass by the Moon. 'Gravity capture' means that Danuri was stably captured by the Moon's gravity. For example, if it were not captured by the Moon's gravity, it could drift away from the Moon's vicinity into other outer space. In other words, it could become a 'space orphan.'

There was actually an incident where a spacecraft nearly became a space orphan. In April 1970, Apollo 13, launched for a lunar landing, suffered an oxygen tank explosion due to abnormal vibrations in the command module while in the Moon's gravitational sphere 320,000 km from Earth, severely damaging the command module. The astronauts on the mission hurriedly abandoned the command module and moved to the lunar module.

At that time, NASA Flight Director Gene Kranz believed the only way to bring the astronauts home was to use the Moon's gravity to put the lunar module on a return trajectory. However, if the orbit was missed, the astronauts would inevitably become eternal space orphans?a kind of gamble.

As expected, being captured by the Moon's gravity was by no means an easy task. By using the lunar module's engine to go around the far side of the Moon and then setting an accurate course, it was possible to enter a return trajectory to Earth, but if an error occurred, orbit correction was impossible, and the spacecraft would disappear into other parts of space. The astronauts, with sweaty palms, managed to enter the return trajectory with the help of the Moon's gravity. The Apollo 13 incident was made into a movie titled 'Apollo 13' in 1995.

Conceptual diagram of Danuri's lunar mission orbit insertion maneuvers, a total of 5 times (December 17-28). Photo by Korea Aerospace Research Institute

According to KARI, Danuri's process of being captured by the Moon's gravity was also not easy. Since its launch on August 5, Danuri has traveled a total of 5.94 million km. During this journey, its speed reached up to 8,000 km/h. Given this situation, the first insertion maneuver aimed to reduce Danuri's speed from 8,000 km/h to 7,500 km/h by operating thrusters for about 13 minutes, then enter the lunar orbit moving at 3,600 km/h.

After the first insertion maneuver, KARI analyzed orbital data for about two days and confirmed that the target speed reduction (8,000 km/h → 7,500 km/h) and elliptical orbit insertion were achieved, finally verifying that Danuri was stably captured by the Moon's gravity. Having safely completed the insertion maneuver, Danuri is currently orbiting the Moon with a perilune of 109 km, an apolune of 8,920 km, and an orbital period of 12.3 hours relative to the lunar surface. KARI explained the significance of this first maneuver success by stating, "Danuri has become a true 'lunar orbiter' orbiting the Moon after being captured by the Moon's gravity."

Danuri plans to perform four additional maneuvers to approach its final target orbit at 100 km above the lunar surface. The second, third, and fourth insertion maneuvers will be conducted sequentially on the 21st, 24th, and 26th, respectively. The final success will be determined after data analysis on the 29th. Since Danuri has passed the most difficult first insertion maneuver, there is a strong analysis that its challenge is likely to succeed.

This content was produced with the assistance of AI translation services.