Soviet and Russian Lunar Exploration

was difficult to escape in the ocean and could take some time to find. They also argued
against the expense involved in having a big recovery fleet at sea.
The timing for Russian around-the-moon missions around the sun-Earth-moon
symmetries was therefore quite complex [14]. To meet all these requirements, there are
only about six launching windows, each about three days long and a month apart,
each year. There can be long periods when there are no optimum conditions. There
were no optimum launch windows for Zond to the moon between January and July
1969, the climax of the moon race. The scarcity of these opportunities explains why
several L-1s (e.g., Zond 4) were fired away from the moon. Although these missions
caused mystery in the West, the primary Russian interest was in testing navigation,
tracking and the reentry corridor. Having the moon in the sky was not absolutely
necessary for these things and since it was not available anyway, they flew these
missions without going around the moon.
L-l/Zond
Length
Diameter
Span
Weight
Habitable volume
Engine
Fuel
Thrust
Specific impulse
5m
2.7 m (base)
9m
5,680 kg
3.5m 3
One KDU-35
AK27 and hydrazine
425 kg
276 sec
Block D
Weight 13,360 kg
Fuel Oxygen and kerosene
Thrust 8,500 kg
Specific impulse 346
Length 5.5 m
Diameter 3.7 m
Source: Portree (1995); RKK Energiya (2001)
When the L-1 Zond was wheeled out for its first test - Cosmos 146, set for 10th March
1967 - the three-stage UR-500K Proton stood over 44 m tall and must have been a
striking sight. The first two tests were called the L-1P, P for 'preliminary' indicating
that a full version of Zond would not be used and that a recovery would not be
attempted. The first stage would burn for 2 min with 894 tonnes of thrust. The second
stage would burn for 215 sec. The third stage would place Zond or the L-1 in low-
Earth orbit in a 250 sec burn. Finally, the Korolev block D fourth stage would fire
100 sec to achieve full orbit. One day after liftoff, the fourth stage, block D, would
relight on the first northbound pass over the equator to send Zond out to a simulated
moon [15].