The speed of the International Space Station (ISS)

 

The speed of the International Space Station (ISS)

    The International Space Station (ISS) orbits Earth at a speed of approximately 17,500 miles per hour (28,000 kilometers per hour)(7.66 kilometers per second). This speed is required to maintain the station's altitude and to counteract the effects of gravity, which would otherwise cause it to fall back to Earth. This speed allows the ISS to complete an orbit around Earth every 92.65 minutes and travels at an altitude of approximately 248 miles (400 kilometers) above the surface of the planet.

    Now, how the cargo missions from Earth connect with the orbiting station so fast is a whole science called Space Rendezvous and it takes a whole team of specialists in Orbital Mechanics and Station Keeping.

HOW DO SPACECRAFT CONNECT WITH IT?

Spacecraft connect with the International Space Station (ISS) through a docking process. This process involves the spacecraft slowly approaching the ISS and then aligning itself with a specific port on the station, known as a docking adapter. Once the spacecraft is properly aligned, it is then connected to the ISS through a series of latches and mechanical interfaces.

The process of connecting a spacecraft to the ISS is typically done by the spacecraft's onboard computer, which uses a combination of cameras, sensors, and navigation systems to guide the spacecraft to the correct position. Before the docking process can begin, the spacecraft must first perform a series of maneuvers to adjust its velocity and trajectory to match that of the ISS.

Once the spacecraft is connected to the ISS, it can then be used to transport cargo, supplies, and crew members to and from the station. Additionally, spacecraft can also be used to perform maintenance and repairs on the ISS, as well as to conduct scientific experiments and research.

For Crewed spacecraft, astronauts will use the spacecraft hatch to enter and exit the ISS. NASA's spacecraft that currently is used is the SpaceX Crew Dragon and the Boeing Starliner and Russia's Soyuz spacecraft.

WHAT IS RENDEZVOUS?

When two spacecraft are so close together that they are only a few meters (closer to 100 feet or less) apart in the same orbit, the difference in their velocities is negligible, less than 10m/s. Another most important thing that is required for a successful rendezvous is station keeping. Station keeping is basically maintaining this proximity state so that docking can be done when needed. Docking means bringing two spacecraft together and moving them as one ship to exchange cargo or astronauts.

WHAT IS THE RENDEZVOUS PROCEDURE?

First, the tracker craft is brought into a low orbit a few hundred meters near the space station (can also be taken into high orbit). Now, after determining its relative velocity from the space station, the speed is gradually increased (Hohmann Transfer), the orbit becomes higher as the speed increases (Kepler's third law).

Now there are two things here, either the Tracker craft is placed behind the space station in the lower orbit to accelerate it to the station in the upper orbit or it is launched from the space station to the station in the upper orbit. be placed ahead and brought down to the orbit of the lower station at the appropriate time to achieve the rendezvous.

Then when the relative velocity difference of a few meters per second is left and station keeping is also achieved, this velocity difference is gradually eliminated for docking and after docking the channel for about 2 hours. The pressure is increased, after increasing the pressure, the channel is opened to allow the astronauts to enter.

RENDEZVOUS ATTEMPTS IN SPACE HISTORY:

Attempts were made in Russia's Vostok program such as Vostok 3 & 4 and Vostok 5 & 6 launched in pairs in 1962-63 but failed to achieve rendezvous. The first attempt by the United States in June 1965 failed, in which astronaut Jim McDivitt unsuccessfully attempted to rendezvous the Gemini 4 spacecraft with the upper stage of his own rocket Titan-II. The first successful rendezvous was in December 1965 when astronaut Wally Schirra brought Gemini 6 within 1 foot of the Gemini 7 spacecraft and held it there for 20 minutes. The first successful docking was in 1966 when Neil Armstrong paired the Gemini 8 spacecraft with the Agena Target Vehicle. Agena was an unmanned spacecraft used in NASA's Gemini program specifically for rendezvous and docking practice. All of these missions were instrumental in facilitating space exploration for NASA's Apollo program.