progress iss-4p launch

Progress M1-4 on the pad. Image courtesy Spaceflight Now/NASA TV.

View of Alpha from Progress M1-4. Image courtesy Spaceflight Now/NASA TV.

Progress M15 in orbit. Image courtesy RKK Energia.

Editor's Note: After the time of this writing, the launch of ISS-4P was delayed to 21 May 2001; the International Space Station did not yet need the resupply craft. The Progress module docked to Zvezda's aft port one day later and remained at the station until 22 August 2001.

On the evening of 12 April 2001, a Progress automated resupply ship will be launched from the Baikonur Cosmodrome in Kazakhstan toward the International Space Station Alpha.

The 7500 kg Progress vehicle was originally developed by the Soviet Union to ferry food, rocket propellant, and other supplies to their Salyut space stations. After the launch of the Space Station Mir in February 1986, Progress spacecraft were used to service that space station. An improved version of the Progress will be used to service Alpha during its on-orbit assembly and operations.

The Progress does not carry people, but its development and flight profile are closely related to the former Soviet Union's human spaceflight vehicles. The Progress launches on the same type of rocket as the Soyuz (the vessel which has carried cosmonauts into space since 1967). The rocket consists of four strap-on boosters surrounding a two-stage core rocket; it burns kerosene and liquid oxygen and has a mass of 300000 kg at launch. After firing for 500 seconds to accelerate to a speed of 7600 meters per second, the rocket falls silent and separates from the Progress.

Once in orbit and separated from the booster, the Progress deploys its antennas and solar arrays and begins a series of on-orbit maneuvers to bring it to a rendezvous with the space station (Salyut 6, Salyut 7, Mir, or ISS/Alpha). Normally, the Progress automatically docks to the space station; however, it can be switched to manual mode, in which the crew of the space station directs the module toward the station docking port by watching video transmitted from a camera on the Progress.

After the Progress docks to the station, the radar antenna for the automated docking system is retracted. The crew of the station then opens up the Progress's pressurized compartment and unloads the supplies. Meanwhile, propellants from the Progress's pressurized tanks are fed into the station's tanks to refuel the station. After the Progress has completed its mission at the station, its pressurized compartment is filled with waste and sealed. The Progress then separates from the station and fires its engines to send it falling back into Earth's atmosphere, where it burns up.