Mars-69, 1969

The Mars program was the first to make use of the powerful Proton launcher. The 1969 launch opportunity was a particularly favorable one and the large increase in available spacecraft mass offered the opportunity to attempt a soft landing mission, but it was decided on this initial campaign to send a spacecraft that would release an entry probe from orbit around the planet. If successful, it would provide the first in- situ measurements of the Martian atmosphere.

The first design for the Mars-69 spacecraft took advantage of all the work that had been done for the new lunar landing vehicle, the Ye-8. This design ultimately turned out to be impractical for Mars and a complete redesign produced an in-line modular configuration similar to, but much larger and more robust, than the preceding 3MV spacecraft.

The core of the Mars-69 spacecraft was a spherical propellant tank which had the engine beneath and a cylindrical section above, and held the solar panels, antennas and thermal control system. The navigation system and orbital instrument modules were mounted on opposite sides of the tank. The entry probe was installed above the cylinder. The avionics were a significant improvement on the 3MV spacecraft. Due to insufficient time for testing and significant growth in spacecraft mass, the entry vehicle had to be deleted from the 1969 campaign. Two identical orbiter spacecraft were launched in late March and early April, 1969, and unfortunately both were lost to launch vehicle failures.