Overview
Progress is an uncrewed cargo spacecraft developed by RKK Energia and operated by Roscosmos. Derived from the Soyuz design, it has been resupplying space stations since 1978 — first Salyut, then Mir, and now the International Space Station. With over 180 flights, it is the most-flown cargo spacecraft in history.
Beyond cargo delivery, Progress provides a critical function: orbital reboost. Its engines periodically fire to raise the ISS orbit, counteracting atmospheric drag that slowly pulls the station downward. Progress is expendable — each capsule burns up on re-entry loaded with station waste.
Key Specifications
| Parameter | Progress MS (current) |
|---|---|
| Manufacturer | RKK Energia |
| Type | Uncrewed cargo + ISS reboost |
| Total Cargo | 2,400 kg (pressurised + propellant + water) |
| Length | 7.23 m |
| Mass | 7,150 kg (loaded) |
| Launch Vehicle | Soyuz 2.1a |
| Launch Site | Baikonur Cosmodrome |
| Docking | Automated (Kurs system) |
| Return Cargo | None — destructive re-entry |
| Reusability | No — burns up with station waste |
ISS Reboost Function
The ISS orbits at ~400–420 km, where residual atmospheric drag causes it to lose 2–4 km of altitude per month. Progress uses its propulsion system to periodically reboost the station, firing its engines while docked. This is a critical function — without regular reboost, the ISS would re-enter within 1–2 years. Cargo Dragon and Cygnus do not provide reboost capability, making Progress (and occasionally Cygnus with its own extended missions) essential for station maintenance.
Frequently Asked Questions
Over 180 flights since 1978, supplying Salyut, Mir and the ISS.
No. Progress is expendable — it burns up on re-entry loaded with station waste. Only Cargo Dragon can return significant payloads.
The ISS loses altitude due to atmospheric drag. Progress uses its engines to periodically push the station higher, a critical function for station survival.