Work on the TMK project continued, including trajectory trade-off studies and refinement of the design. In its final iteration, in May 1966, before Korolev�s OKB was overwhelmed by N1-L3 development work, the design was known as the KK - Space Complex for Delivering a Piloted Expedition to Mars. Nuclear-electric propulsion was retained, but various mission designs were studied in an attempt to reduce the overall vehicle mass.

The spacecraft itself now consisted of six (less ambitious) modules:

• EK - Expeditionary spacecraft, the command centre for piloting of the complex on the interplanetary portions of the mission
• OK - Orbital Complex, which contained the living and work compartments and the life support systems
• SA - The Landing Module, to be used by the crews for landing on the surface of the planet either from Martian orbit or directly from the interplanetary trajectory
• AV - The Ascent Module, in which the crew would return to the EK from the Martian surface;
• RV - The Ascent Rocket stage, which would take the AV from the Martian surface to either Mars orbit or directly on an interplanetary trajectory
• PS - The Planetary Station, which would be used by the expedition on the Martian surface for life support and scientific research

The following mission profiles were considered for the mission:

• Descent Scheme - direct aerodynamic braking from the interplanetary trajectory with landing of the complete expedition on the surface of the planet. Direct ascent from the Martian surface to an interplanetary trajectory, with no intermediate Martian orbit. This was the least favoured scheme. It required the most total energy and the choice of landing regions on Mars was very limited. Nuclear electric propulsion could not be rationally used in this alternative, since it would only be used for the departure from Earth (braking at Mars would be aerodynamic and ascent from the surface would require high-thrust chemical stages).
• Orbital-Descent Scheme - Insertion of the entire expedition into Mars orbit, followed by descent of only those portions required to the surface. Return of the crew to Mars orbit and docking with the waiting EK. Boost of the remaining required modules from Mars orbit to the interplanetary trajectory. This was the favoured scheme and had many advantages. The only drawbacks were the requirement for successfully completing rendezvous and docking in Mars orbit and the long time spent by the crew in the departure and braking spiral orbits of the low-thrust ion engines.
• Orbital Scheme - Insertion of the EK into Martian orbit but without landing on the surface. This was considered as an alternate or preliminary mission.
• Flyby-Descent Scheme: Undocking of those modules required on the surface from the main complex on the interplanetary trajectory. Direct aerodynamic braking from the interplanetary trajectory and landing on the surface of the planet of those modules. Ascent of the crew directly into an interplanetary trajectory, followed by docking with the main complex in interplanetary space. This scheme had the lowest energy requirements but not a few disadvantages. It had the same landing site limitations as the descent scheme and survival of the crew depended on successfully accomplishing the difficult rendezvous and docking on the interplanetary trajectory.

By the time the KK design was completed, the Soviet lunar landing goal had been set and all OKB-1 staff concentrated on design and development of the N1-L3 lunar spacecraft. Work on Mars projects was deferred for the duration of the moon race.

Craft.Crew Size: 3. Total Mass: 150,000 kg. Primary Engine Thrust: 6 kgf. Main Engine Propellants: Xenon. Main Engine Isp: 8,000 sec. Electric system: 15,000.00 total average kW. Electrical System: Nuclear reactor.

Work on the TMK project continued, including trajectory trade-off studies and refinement of the design. In its final iteration, before Korolev�s OKB was overwhelmed by N1-L3 development work, the design was known as the KK - Space Complex for Delivering a Piloted Expedition to Mars.

• 283 - Vetrov, G S, S. P. Korolev i evo delo, Nauka, Moscow, 1998.