A switch to two independent nuclear reactors to increase flight reliability 640У292 (67 970 bytes)

A change in the shape of the lander (a lifting body instead of a "headlight" with a heat shield) 640У436 (53 219 bytes)

The next Martian mission project proposed in 1987, after a successful launch of super heavy-lift launch vehicle Energia, to a large extent drew upon engineering solutions of 1969 project.
The distinctive feature of this project was the use of Energia launch vehicle as the means of putting elements of the spacecraft into orbit. Besides, the interplanetary transit was to use two independent propulsion power plants 7.5 MW each with its own nuclear reactor, radiator, and a cluster of electric rocket engines. This allowed to drastically increase reliability and safety of the interplanetary transit without any increase in the initial mass and cost.