Mission Atlas
← Mission directory

Mission record

Cosmos 300

Also known as Cosmos300, Kosmos 300

U.S.S.R · Launched

Explore trajectory

Failed · Failure

A Soviet lunar mission that reached Earth orbit but failed to leave it, and so received a Cosmos designation.

Destinations
Launch vehicle
Proton
Launch site
Tyuratam (Baikonur Cosmodrome), U.S.S.R
Countries
Soviet Union
Mission types
Sample return

Chronology

Mission timeline

  1. Launch

    Cosmos 300 launched from Baikonur Cosmodrome

  2. Milestone

    The Block D stage failed, leaving the spacecraft in Earth orbit

    The cited page records the failure and the resulting Cosmos designation without giving a date for it.

    Earth

Mission architecture

Vehicles

  • Cosmos 300 · Spacecraft

    Destinations: Moon

    • Cosmos 300 ascent stage · Spacecraft

      Destinations: Moon

      • Cosmos 300 sample return capsule · Return capsule

        Destinations: Earth

Trajectory record

Trajectory dataset not yet available

Known dates and encounters do not uniquely determine a flight path. This mission’s sourced timeline is available above; no verified trajectory is currently published here.

What is needed to reconstruct this path?
  • A frame-qualified position and vector velocity at an epoch, or equivalent complete orbital elements.
  • Separate state histories and release epochs for the listed vehicles; a parent mission trajectory cannot be assigned to every component.
  • Finer event-time constraints where required by an orbital reconstruction; the stored day/month/year precision is retained.
  • The actual failed-flight state history. Intended destinations are not evidence that the spacecraft reached them.

Provenance

Sources

Each source is listed once and labeled with the mission, event, trajectory, or destination/body context it supports.

Data verified through October 12, 2026