On the 10th of this month, a spacecraft entered Earth's atmosphere at an altitude of approximately 122 kilometers. Its reentry speed reached 33 to 35 times the speed of sound. The surrounding air layer, crushed by the shockwave, was compressed to its extreme limit and heated to ultra-high temperatures. This is the phenomenon known as aerodynamic heating. The spacecraft's surface temperature soared to 3,000 degrees Celsius in an instant. The crew had to endure gravitational acceleration pressing down on them with four times their normal body weight. This hellish scene—seemingly capable of melting flesh and breaking bones—was in fact a monumental moment in the history of space exploration. Artemis II successfully completed a crewed lunar orbit mission for the first time in about half a century and returned safely to Earth. This was the moment of "Welcome! Artemis II"—the return of America's multipurpose crewed spacecraft to Earth.
Spacecraft are said to be far more dangerous when returning to Earth and reentering the atmosphere than when departing. If the reentry angle is too shallow, the craft skips off like a stone across water. If the angle is too steep, the collision pressure and heat from the air layer surge, disintegrating the vessel mid-air. Even with the correct trajectory, mechanical failures can occur. The Soviet Union's Soyuz 1, the world's first crewed spacecraft, crashed in 1967 after atmospheric reentry due to a parachute malfunction. In 1977, the crew of Soyuz 11 died from a depressurization accident caused by a pressure valve defect during atmospheric reentry. In 2003, the U.S. Space Shuttle Columbia exploded in the atmosphere, unable to withstand the extreme heat after damage to its wing's thermal tiles.
To date, only six nations have successfully overcome these formidable hurdles to achieve atmospheric reentry: the United States, Russia, China, the European Union, Japan, and India. North Korea has made several reentry attempts, but these were illegal intercontinental ballistic missile (ICBM) tests, not spacecraft. South Korea successfully launched its domestically developed space rocket Nuri for low-orbit satellite deployment, but has yet to demonstrate atmospheric reentry technology. To complete our unmanned lunar exploration plans targeted for the 2030s, we must quickly catch up with the technology of these six advanced nations. However, there is concern that the government and both ruling and opposition parties may push space exploration budgets to the back burner while securing funds for local election pledges.
