Tag Archives: two-day rendezvous

For the second time, a Progress freighter has launched and, after only four orbits, docked with ISS.

For the second time, a Progress freighter has launched and, after only four orbits, docked with ISS.

This was the fourth Progress launched this year, the second to follow an abbreviated four-orbit rendezvous with the space station. Russian flight controllers normally implement two-day rendezvous profiles, but they are perfecting procedures for single-day flights for possible use with manned Soyuz missions to shorten the time crews are forced to spend in the cramped ferry craft.

The Russians have used the leisurely two-day rendezvous path now for almost a half century. So, why are they suddenly trying to shorten the travel time to ISS to six hours? Though there are many good engineering reasons, I also suspect it is because they are now feeling the pressure of competition. The shorter travel time probably lowers their costs at mission control. It also makes using the Soyuz for manned flights more appealing. Dragon for example is presently using the two-day rendezvous path. And Dragon will soon become a direct competitor to Soyuz, when it begins flying humans in the next three to five years.