Ask an Explainer

People and supplies can be transported to orbiting spacecraft in a few ways. NASA currently has two companies, SpaceX and Orbital ATK, sending unmanned supply ships to the International Space Station (ISS). Russia uses the unmanned, disposable Progress cargo ships to get supplies to space and Soyuz space crafts to transport people and supplies back and forth. No matter which is used, mission planners have to calculate precise flight paths to ensure the supply vehicle and the space craft meet in space at the same speed.