Axiom-4 Mission Overview
On June 25, 2025, a significant milestone in space exploration was achieved when a crew capsule, containing four astronauts, launched from NASA’s spaceport in Florida. Among the crew was India’s Group Capt. Shubhanshu Shukla, making his first spaceflight. The mission, named Axiom-4, utilized a Falcon 9 rocket to lift the Dragon crew capsule towards the International Space Station (ISS).
Launch and Initial Trajectory
- The launch occurred at 12.01 pm IST and was smooth, with the Dragon capsule reaching speeds of several thousand kilometers per hour.
- The capsule aimed to dock with the ISS, orbiting approximately 400 km above sea level, within 28 hours.
Orbital Mechanics
Understanding the trajectory requires visualizing the capsule and the ISS as race cars on separate lanes of a track rather than a direct, vertical path.
- The capsule must match the ISS’s altitude and velocity vector using orbital mechanics and safety protocols.
- The initial orbit is lower and slightly elliptical, at about 200 km high, maintaining a speed of approximately 27,000 km/hr to prevent descent.
- Dragon's orbit starts at 88 minutes per revolution compared to the ISS's 92 minutes, allowing it to catch up gradually.
Docking Process
- Dragon performs phasing burns to adjust its orbit and synchronize with the ISS's path.
- The pre-docking phase lasts about 28 hours, aligning Dragon with a free docking port on the ISS.
- Upon nearing the ISS, Dragon moves into an alignment corridor, progressively slowing its speed for docking.
- Critical GO/NO-GO polls and LIDAR checks are conducted to ensure docking safety, with specific holding points as contingency measures.
Significance of the Dragon Crew Capsule
- SpaceX's Dragon capsule was selected for its conservative, fuel-rich approach, allowing the crew to perform essential check-outs and rest before docking.