The final version would have required two Proton launches to assemble the spacecraft's booster stages in low earth orbit. They would then boost the 5M spacecraft to Mars, where it would land, scoop up some Martian soil, and boost an 8.7 kg return capsule on a return journey to earth. It was cancelled when political forces shifted and the project was seen as too complex to succeed.
The 4M was a version of the 5M that would be flown to Mars on the launch window before the soil retrieval attempt. Instead of the return craft, it would land a modified version of the Lunokhod rover on the Martian surface. This would allow systems to be checked and achieve a scientific and propaganda first without taking the risk of the complex all-up spacecraft succeeding.
In 1974 the N1 booster program was cancelled and Mishin's failed TsKBM design bureau was reorganized into Glushko's new NPO Energia. Unlike the Mishin group, the Lavochkin team had a string of successful lunar and interplanetary probe missions. Afanasyev directed that they continue work on a Mars soil return mission to leapfrog the Americans.
In the absence of the N1, the spacecraft would have to be put into low earth orbit using two launches of Chelomei's Proton booster. One launch would put a 22 metric ton fully-fuelled Block D upper stage equipped with the necessary rendezvous and docking system into low earth orbit. The second launch would place the combination of a partially-fuelled 13.5 metric ton Block D stage and the 8500 kg 5M spacecraft. The first Block D would rendezvous and dock with the second Block D. The stages would then fire, one after the other, to put the 5M on a trans-Mars trajectory.
After the coast to Mars, the orbiter would separate and brake itself into Mars orbit, while the lander would re-enter the atmosphere at 5.6 km/s. Entry would begin at 100 km altitude at a 13 degree angle of entry. The aeroshell, shaped like the American Apollo capsule, would use lift during re-entry to reduce G forces and adjust the landing point. At 5.5 km above the surface, with the speed reduced to 1.0 km/s, the capsule would fly a pop-up maneuver, gliding to an altitude of 9.4 km and velocity of 700 m/s. At this point the landing radar would be activated and the terminal landing phase would begin. Low-thrust engines would begin operation at 3.03 km altitude and 355 m/s, followed by the high-thrust engines at 2.13 km and 338 m/s. The high-thrust engine package would be dropped when the lander reached 1.85 km/s altitude and 51 m/s. A constant-speed descent would then be made using the low-thrust system. Just 10 to 30 m above the surface the aeroshell would be jettisoned, the undercarriage lowered, and the lander would settle onto the surface.
The landing site would be surveyed using panoramic cameras. The lander's robot arm would be commanded to scoop up some soil from a desirable location and insert it in a return capsule. The 2000 kg two-stage booster would then depart with the capsule, putting it in Mars orbit.
Meanwhile a third Proton rocket would have launched a separate Mars return craft toward Mars. This would brake into Martian orbit, then rendezvous and dock with the upper stage of the lander with the capsule of Martian soil. The capsule would be transferred to the return craft, which would then boost itself out of Mars orbit and head back to earth. It would maneuver yet again to place itself in a low earth orbit. A Soyuz manned spacecraft would rendezvous with the return craft, and retrieve the capsule with the Martian soil. This was considered necessary to allow study of the soil in space and ensure it was biologically safe before returning it to earth. Again the Soviet scientists showed a great concern to prevent contamination of the earth by suspected Mars micro-organisms.
This elaborate scheme, calling for three automated rendezvous and docking maneuvers, was necessitated by the lack of a heavy lift booster in the Soviet Union. But it was considered by its chief designer, Perminov, too complicated to have much likelihood of success. Therefore another designer at Lavochkin, V P Panteleyev, was ordered by Afanasyev to pursue its further development.
Panteleyev proposed modifying the Block D trans-Mars injection stages to allow cross-pumping of propellant from the first stage Block D to the second stage. This made for a more efficient burn sequence and allowed the spacecraft mass to be increased from 8,500 to 9,135 kilograms. The heavier Apollo-like re-entry vehicle was replaced by a low-drag pure ballistic aeroshell. This consisted of a 3 m diameter metallic base, and an umbrella-like construction of beryllium spokes with fiberglass cloth. This would deploy out to an 11 m diameter. These measures allowed for the mass of the two-stage Mars-orbit stage to be increased from 2,000 to 3,190 kg, allowing the soil to be returned directly to earth, and eliminating the need for a separate Mars return craft to be boosted by a third Proton launch. The final breakdown was: 1680 kg for the orbiter, and 7455 kg for the lander, including the 3,190 kg ascent stage.
The revised design was approved by Lavochkin Chief Designer Kryukov in January 1976. However weight was still marginal, and a number of innovative solutions were found to further simplify the design. The sterilization of the soil samples would be conducted in Mars orbit using passive means, eliminating the contamination problem. The re-entry capsule was reduced to a mass of only 7.8 kg by eliminating all of the recovery aids - the parachute, altimeters, battery, homing beacon, and computer. The capsule would enter the earth's atmosphere at 12 km/s as a completely passive artificial meteorite. It was tough enough to sustain the impact with the earth without a parachute. Its landing position was expected to be known within 40 km, and a radioactive source would be included in the capsule. This would allow the recovery forces to locate it using radiation detectors.
By 1978 the spacecraft was in fabrication. But suddenly political forces shifted. A government institute issued a report denouncing the whole enterprise as a high-risk, high-cost, low-chance-of-success venture. Afanasyev did an about-face and not only cancelled the project, but fired Kryukov as head of the bureau.
Gross mass: 9,135 kg (20,139 lb).
Height: 3.80 m (12.40 ft).
Diameter: 4.00 m (13.10 ft).
Span: 11.00 m (36.00 ft).