Why does the Axiom-4 mission need 28 hours to reach the ISS?
On June 25 at 12.01 at 12.01, India’s first space flight, including four astronauts, including Group Captain Shubhanshu Shukla, a crew capsule rose to NASA’s Falcon 9 rocket from Florida.
The departure pointed to the beginning of the long-awaited Aksiyom-4 mission.
The launch was smooth. When the two stages of the rocket completed his work, the crew capsule, called Dragon, traveled on a thousand kilometers per hour.
The arrival point of the capsule was the International Space Station (ISS), which is located in orbit at a height of 400 km above sea level. During the removal, Dragon, who organized this task, said that Dragon would approach Iss in 28 hours.
Why does a spacecraft that travels so fast to reach a little more than the distance between Chennai and Bengaluru need 28 hours?
The capsule and the ISS are not a car trying to drive up to a point in front of 400 km, but help to depict the same part as two racing cars in separate strips.
Everything takes place on the earth and the choreography is determined by the orbit mechanics and solid safety rules.
In order to share the strip of ISS, the capsule must comply with both the altitude and the speed vector. This is obtained using the timing as well as raw speed.
Instead of giving the crew capsule radially outward energy, mostly side -by -side. Direct 400 km rising would leave Dragon at almost zero side speed and would almost fall back like a thrown ball.
The Falcon 9 rocket will be vaulted in a light elliptical park orbit of a low elliptical park. The speed there is about 27,000 km/h, which protects the capsule to prevent it from turning to the ground.
ISS is higher than this park orbit at approximately 400 km, and therefore surround the world a little slower to prevent hug. Once, ISS takes about 92 minutes to walk around the Earth, while Dragon starts with about 88 minutes. Thus, lower than ISS, Dragon is slowly behind in its orbit until it is caught with ISS.
After the system controls, the dragon capsule will first perform a series of small repulsive burns to raise the entire orbit (the point in the elliptical orbit of the dragon is the farthest from the earth).
Each of these burns is timely time after completing a few orbits, Dragon is exactly where ISS will be. This looks like merging on a highway at the right exit instead of directing directly to another car.
For the Axiom-4 mission, task planners designed a front-wing profile or about 18 orbits that lasts about 28 hours. At the end of this profile, the Dragon Crew capsule will be on the right side of ISS at a time when a free placement port is available and the ISS team is awake.
When Dragon arrives within 30 km of ISS, it will carry itself to a ‘corridor’ aligned with ISS. From here, the rules require the capsule to move more than a few meters per second. When Iss is in 20 m, Dragon will have to slow down up to a few centimeters per second.
There are 400 m, 220 m, 20 m and 1 m away from ISS, where the dragon crew will have to perform Go/GO surveys and LIDAR controls, including the designated task pilot, Captain Shukla. Even if there is a wrong sensor reading in this process, the dragon will have to withdraw from ISS along a pre -programmed path.
This deliberate pacing alone adds a few hours to the ISS approach of the crew capsule alone.
It is important for Axiom Space and NASA to use the Dragon Crew capsule for this task. The task operators allowed the crew to choose a more conservative profile in terms of fuel, allowing the crew to finish the check-out before the intensive placement exercise.
Published – 26 June 2025 03:30 IST
