INTO THE SEA OF RAINS

Luna 17’s mission was, at least for its first six days, apparently identical to that of Luna 16 and 15. A four-day coast out to the moon was followed by lunar orbit insertion circular at 85 km, 1 hr 56 min, 141°. On the 16th, the onboard motor lowered the orbit to an altitude of 19 km. Luna 17’s target was nearly a hemisphere away from that of Luna 16. The entire western face of the moon is dominated by a huge, dark ‘sea’ which is called the Ocean of Storms. In its northwest corner is a semi-circular basin, the Sea of Rains.

After only two days in orbit, reflecting the bright sunlight of the setting sun, Luna 17 skimmed in low over the Jura Mountains. The retrorocket fired. Luna 17 came down as the radar checked the landing site. At 600 m, coming down at 255 m/sec, the final main engine burn was made. Down it came, as softly as a parachutist on a wind – free day. By the time it landed, Luna 17 weighed 1,836 kg. The long shadows of the structure stood out starkly toward the darkening east. For two hours, Luna 17 reported back its position. Russia coolly announced its fourth soft-landing on the moon. A return capsule would be fired back to Earth the next day – or so everyone

Lunokhod descending to the moon

Not so. On the upper stage rested the first vehicle designed to explore another world. It had eight wheels, looking like pram wheels, which supported a shiny metallic car, covered by a kettle-style lid. Out of the front peered two goggle-like television eyes. Above them peeped the laser reflector and two aerials. It was an unlikely-looking contraption – on first impression more the outcome of a Jules Verne or H. G. Wells type of sketch rather than a tool of modern moon exploration. But the wheels were ideal for gripping the lunar surface and less prone to failure than caterpillars. The lid could be raised backward to the vertical and then flat behind, exposing solar cells to recharge the batteries in the Sun’s rays. The exposed top of the car was a radiator, discharging its electronic and solar-baked heat. There was genius in its simplicity.

The most dangerous part of the vehicle’s journey was probably getting off the platform and onto the lunar surface. Two ramps unfolded at each end, so it could travel down either way if one exit were blocked. Still sitting on the landing platform, ground control commanded the dust hoods to fall off the television eyes. A picture came back at once, showing the wheel rims, the ramp down to the flat bright surface and the silhouette of the landing ramps. There was nothing for it but to signal to Lunokhod to go into first gear and roll down the ramp and hope for the best.

So it was that at 6:47 a. m. on the morning of 17th November 1970, carrying the hammer and sickle, a red flag and a portrait of Lenin, the moon vehicle edged its way down the ramp and rumbled 20 m across the lunar surface. Its tracks were the first wheel marks made on another world. Its television cameras showed its every move and at one stage Lunokhod slewed around to film the descent stage which had brought it there. On day 2 it parked itself, not moving at all, lying there so that its lid could soak

Lunokhod tracks across the moon

in solar energy for its batteries. On day 3 it travelled 90 m, 100 m the following day, overcoming a 10° hill. On the fifth day, with lunar night not long off, it closed its lid, settled down 197 m from Luna 17 and shut down its systems for the 14-day lunar night. At this stage, it had travelled a modest 200 m. A nuclear power source would supply enough heat to keep it going till lunar daybreak.

The Soviet – and Western – press took to Lunokhod with an affection normally reserved only for friendly robot television personalities. There was unrestrained ad­miration for the technical achievement involved, for it was a sophisticated automated exploring machine. The Times of London called it ‘a remarkable achievement’. ‘A major triumph,’ said The Scotsman. The Daily Mail, in a front-page editorial entitled ‘Progress on wheels’ gave Lunokhod’s designers an effusive message of congratulations. It was the main news story for several days.

The control centre for Lunokhod was, like much else in the venture, a scene straight from science fiction. It was located in Simferopol, Crimea, near the big receiving dishes. Five controllers sat in front of television consoles where lunar landscapes were projected on screens. The crew of five worked together like a crew operating a military tank. Signals were relayed to the drivers by the high-gain antenna which had to be locked on Earth continuously. The drivers operated Lunokhod with a control stick with four positions (forward, backward, stop, rotate), and they could make the rover go either of two speeds forward: 800m/hr or 2km/hr, or reverse. If the Lunokhod looked like crashing, either drivers or commanders could press a panic button to turn the electric engine off. Any one wheel could be disconnected individ­ually if it got stuck or there were a problem. Lunokhod was designed to cope with obstacles up to 40 cm high or 60 cm wide, but an automatic system would cut the engine out if it began to tilt. Average speed started at 2.3 m/hr but later increased to 4.8 m/hr. All the wheels ran at the same speed and they turned the rover like a tank by running the wheels faster on one side than the other, until the change of direction was achieved – skid-steering [5]. In reality, driving the Lunokhod proved to be quite a lot more difficult than the drivers expected. The drivers realized at once that the cameras were too low down – it was like being a human on all fours rather than upright. The television cameras were able to provide little contrast: the images were too white, and rocks and craters looked deceptively alike [6]. Driving the moonrover was strenuous and during the lunar days the teams alternated 9 hr shifts, catching up on sleep during the lunar nights.

So great was the excitement of the first Lunokhod that journalists, academicians and scientists flooded into mission control, apparently taking up a general invitation to do so by Mstislav Keldysh. Vistors were not supposed to crowd around the drivers, still less talk. But the situation got out of hand, especially when backseat drivers would exclaim: ‘He’s going to crash into that rock!’ or ‘Mind that crater!’ Between the natural stress, the heat coming out of the televisions and the backseat drivers, the drivers’ pulses crept up to 140 and the stress began to tell. Babakin had had enough. ‘Everyone out of here!’ he ordered and after that special passes were needed to visit the control room and then in a suitable state of humility [7].

Back on the moon, nighttime temperatures plunged to — 150°C and stayed at that level a full two weeks. Lunokhod, lid closed, glowing warmly from the heat of its own nuclear radio isotope, rested silently on the Sea of Rains. It was bathed in the ghostly blue light of Earth as the mother planet waxed and waned overhead. Even as it stood there, laser signals were flashed to Lunokhod from the French observatory in the Pic du Midi and from the Semeis Observatory in the Crimea. They struck the 14 cubes of the vehicle’s laser reflector and bounced back. As a result, scientists could measure the exact distance from the Earth to the moon to within 18 cm.

To the east of Lunokhod rose a ridge and the sharp rays of dawn crept slowly over its rugged rocks early on 9th December. Had the moonrover survived its two-week hibernation? This was an anxious moment and pulses began to race when the first command was sent to the Sea of Rains to open the lid. Nothing happened. They tried again and this time the rover responded. It raised its leaf-shaped lid and at once began to hum with life. Four panoramic cameras at once sent back striking vistas of the moonscape, full of long shadows as the Sun gradually rose in the sky. After a day recharging, Lunokhod set out once more. The Lunokhod got into big trouble straight

Lunokhod route-planning conference

away. On 10th December, Lunokhod got stuck in a crater and no matter what the drivers did – go forward, go back – it remained stuck. Eventually, after nine exhaust­ing hours, the rover suddenly came free.

The drivers on Earth soon got into their stride and they had the moon car in second gear, swivelling around, reversing and traversing craters and slopes at will. One day it travelled 300 m, more than it had achieved in its first five days in November. Lunokhod took a south-southeast path, skirting around and between craters and parked in December in a crater at the southernmost end of the route, 1,400 m from the landing stage. In January, swivelling round to head back north, the panoramic camera eyes spotted in the distance a range of mountains – the far peaks of the Heraclides Promontory, part of the vast bay encircling the Sea of Rains.

For ground control it was just like being there. From the cosy warmth of their control post they could direct at will a machine a quarter of a million miles away. This prompted romantic notions in the minds of the Earthbound. Radio Moscow promised ‘more Lunokhods, faster and with a wider range.’ Boris Petrov spoke of mooncars

Lunokhod tracks

that would collect samples and bring them to craft like Luna 16 for transporting home. Others would instal packages on the moon and carry telescopes to the farside where there was radio peace, free from Earthside interference. Other probes would reach the lunar poles.

It turned out that the drivers had been well selected for their mission. The drivers faced several challenges. First, the 20 sec frame transmissions were too slow. Although driving the lunar rover might seem simple enough to a modern generation reared on video games, in reality the crew had to memorize features some distance ahead. The 20 sec time gap between frames meant that Lunokhod could reach a feature – stone, rock, crater, obstacle – a full third of a minute before the crew saw visually that it had arrived. Second, the cameras were set in an awkward place: too low to see far ahead, yet set toward the horizon in such a way as to create a dead zone immediately in front of the rover that the drivers could not see. Third, the light contrasts of the lunar surface made driving difficult, the drivers having to cope with extremes of shadows and glare. Rather than risk driving across shadowless moonscapes, operations were normally halted for two days at lunar high noon. From time to time, Lunokhod would

Lunokhod returns to landing stage

stop to take panoramic pictures. For the drivers, these were good opportunities to orientate the rover and plan the next stage of the journey.