Axiom Mission 4: Why space docking is crucial for this mission as it nears the ISS?

The Axiom-4 mission with Indian astronaut Shubhanshu Shukla onboard is scheduled to dock with the International Space Station (ISS) at around 4.30pm IST (7.00am EDT) on Thursday, June 26, after more than 28 hours in space.

The International Space Station (ISS) is one of humanity’s most remarkable achievements in space exploration. Orbiting about 400 kilometres above Earth, it serves as both a home and a science laboratory for astronauts and cosmonauts from around the world. Built through the combined efforts of NASA, Roscosmos, ESA, JAXA, and CSA, the ISS has supported continuous human presence since November 2000.

One of the most technically demanding operations in any space mission is docking—where a spacecraft must precisely connect to the ISS while both are moving at orbital speeds. The Ax-4 mission has to dock with the ISS on June 26, 2025, using the spacecraft’s automated system.

The ISS travels at a speed of 28,000 kilometres per hour and completes an orbit around the Earth every 90 minutes. Despite advancements in autonomous docking, astronauts like Shukla are thoroughly trained to perform manual docking if needed. “The docking process requires extremely precise alignment, slowing the spacecraft’s relative speed to near zero, and connecting within millimetre accuracy. Even minor errors can cause failed dockings or damage to the spacecraft,” explained Srimathy Kesan, founder and CEO of Space Kidz India.

Interestingly, there have been notable examples where astronauts had to take manual control during docking. In 2015, Soyuz TMA-19 M’s autopilot failed just 17 meters from the ISS, forcing commander Yuri Malenchenko to manually complete the docking. In 2008, Yuri Lonchakov performed a manual docking of Progress M-01M after an automated system issue. During the 2023 Boeing Starliner mission, NASA astronaut Butch Wilmore also manually docked the spacecraft when thruster issues disrupted the automatic system. Even earlier, in 2000, cosmonaut Yuri Gidzenko had to manually dock the Progress M1-4 due to sun glare and visual interference that disabled the video feed.

In Ax-4, mission Shukla’s role as the mission pilot includes close monitoring of the system and readiness to intervene manually if problems occur. “The ability to switch from automated systems to skilled human control ensures mission safety and highlights the irreplaceable value of astronaut training and experience,” remarked Kesan.

Spacecraft Docking requires precision; imagine trying to park your car in a garage—except both the car and the garage are moving around Earth at 28,000 kilometres per hour. “Docking is the incredibly precise process of linking a visiting spacecraft with the space station to form a safe, airtight bridge that astronauts can use to move between them. The ISS has multiple docking ports and standardised connection points designed to accommodate different spacecraft from around the world, much like a universal charging port,” explained space analyst Girish Linganna.

Using radar systems, cameras, and antennas, the spacecraft locates the ISS and begins its approach. Every move must be carefully calculated; this is like playing a complex game of 3D chess in space. A single misstep could risk collision and endanger the mission. Different missions use different methods, depending on the type of spacecraft involved. “Uncrewed cargo ships use a method called berthing. These ships hover close to the ISS, where astronauts use a robotic arm to gently capture and guide them to a port. This method reduces the risk to fragile equipment onboard. Spacecraft carrying astronauts use automated docking systems to connect directly with the station. This approach is faster and safer in emergencies, allowing quick access to the ISS without external help,” added Linganna.

Axiom-4 mission uses SpaceX’s Crew Dragon, a cutting-edge spacecraft that showcases the next generation of docking technology. Equipped with cameras, sensors, and onboard computers, Dragon performs docking autonomously, constantly adjusting its course in real time. While astronauts can take manual control, the system is built to complete the task on its own. This Dragon capsule—the fifth and final one in SpaceX’s current active rotation—will be officially named by the crew once in orbit. It docks with the International Docking Adapter, a modern standard built for international cooperation in space.

There are different docking systems around the world. The Russian Probe-and-Drogue System is one of the oldest and the most reliable docking systems in space history. It’s used by Russia’s Soyuz spacecraft (which carries astronauts) and Progress spacecraft (which brings cargo). The system works like a long probe from the spacecraft slides into a cone-shaped opening called a drogue on the ISS. It then locks in place securely. This docking is usually automatic and has been working well since the early days of human spaceflight.

Then there is the American Docking Systems, which is also known as the International Docking System (IDS). It is a universal docking system like a common charger that lets modern spacecraft from different countries connect to the ISS safely. It’s used by SpaceX’s Crew Dragon and Boeing’s Starliner, both of which carry astronauts. The spacecraft automatically lines itself up with the ISS using cameras and sensors, then gently docks without needing manual help. IDS was made so that any future spacecraft from around the world can also use it, making space travel more connected and cooperative. It’s fast, safe, and allows for quick departure in emergencies.

There is also the Common Berthing Mechanism (CBM), and this system is mainly used for uncrewed cargo missions, like Northrop Grumman’s Cygnus spacecraft. Instead of docking by itself, the cargo ship floats close to the ISS, and a robotic arm operated by astronauts grabs it and attaches it firmly to the station. This is called “berthing” instead of docking. It’s a slower but very precise process, and it helps bring large cargo loads to the station. Experts point out that together, these systems make sure that all kinds of spacecraft, whether old or new, Russian or American, crewed or cargo, can safely reach the ISS and support life and research in space.

Space docking is evolving, and missions to the Moon, Mars, and beyond will demand more sophisticated and flexible systems. The knowledge gained from ISS missions like Axiom-4 is already shaping the next era of space infrastructure.

Sci/Tech