ProgressThe first Soviet-made unmanned Progress resupply vehicle lifts off en route to the manned Salyut 6 space station. Looking more or less like a Soyuz vehicle, Progress is an automated freighter whose systems lock onto Salyut’s docking transponder, guiding the unmanned craft toward a smooth and completely automated docking (though ground controllers stand by to take manual control by remote). Since Progress is not required to return a crew to Earth, its engines and their fuel can help to boost Salyut 6 into a higher orbit when necessary. It carries over 5,000 pounds of food, clothes and other supplies, and can automatically refill the station’s air and fuel supplies. Progress vehicles become an integral part of the space program, remaining in service long enough to resupply the International Space Station in the 21st century.