how docking to iss works at high speed

The International Space Station (ISS) travels at an average speed of approximately 28,000 kilometers per hour (about 17,500 miles per hour) in its orbit around the Earth. This high orbital velocity allows the ISS to complete one orbit around the Earth roughly every 90 minutes. This incredible speed is necessary to counteract the gravitational pull of the Earth, allowing the station to remain in a stable, low Earth orbit.

Docking with the International Space Station (ISS) at high speed requires a carefully coordinated and precise approach to ensure the safety of both the spacecraft and the station. Here's an overview of how the process works:

1. Rendezvous and Approach:

   • Before reaching the ISS, the approaching spacecraft must perform a series of maneuvers to align its trajectory with the station's orbit. These maneuvers may include adjusting the spacecraft's speed, altitude, and inclination. Spacex's Dragon is also being used to send cargo and crews to ISS.

2. Relative Velocity Adjustment:

   • As the spacecraft gets closer to the ISS, it needs to match its relative velocity with the station. High-speed approaches are typically avoided, and the spacecraft is slowed down to ensure a safe and controlled approach.

3. Initial Contact:

   • The spacecraft approaches the ISS from below or behind and aligns itself with the station's docking port. The spacecraft's guidance and navigation systems play a crucial role in ensuring precise alignment.

4. Capture Phase:

   • To make initial contact, the spacecraft uses a docking mechanism equipped with capture latches or docking probes. These mechanisms are designed to physically link the spacecraft to the ISS.

5. Soft Capture:

   • Once the initial contact is made, the capture latches or docking probe is used to gently bring the spacecraft and the ISS closer together. This phase is referred to as "soft capture." The spacecraft's docking system may include sensors and mechanisms to dampen any relative motion between the two vehicles.

6. Hard Capture:

   • After soft capture, the spacecraft undergoes a series of checks to ensure that it is securely attached to the ISS. Once these checks are complete, the docking system performs a "hard capture." This involves firmly locking the spacecraft into place, creating a secure connection between the spacecraft and the station.

7. Leak Checks and Pressurization:

   • Following hard capture, astronauts on both the spacecraft and the ISS conduct leak checks to ensure the seal between the two vehicles is airtight. Once confirmed, the area between the spacecraft and ISS can be pressurized, allowing astronauts to transfer between the two.

8. Hatch Opening:

   • Once the pressure is equalized, the hatches between the spacecraft and the ISS are opened, allowing astronauts to move freely between the two vehicles.