Launch from the Baikonur Cosmodrome; landing
48 km southwest of Tselinograd.
Soyuz 15 was to conduct the second phase
of manned operations aboard the Salyut 3 military space
The spacecraft arrived at the Salyut 3 space station
successfully, but the cosmonauts were unable to dock, because of a fault
in the automated docking-system (Igla). The Soyuz spacecraft had no reserves or
backup systems for repeated manual docking attempts, so the mission had to be
abandoned. Later on the state commission discovered that the Igla docking
system of the Soyuz needed serious modification. This could not be completed
before Salyut 3 decayed.
The Soyuz spacecraft is composed of three
elements attached end-to-end - the Orbital Module, the Descent Module and the
Instrumentation/Propulsion Module. The crew occupied the central element, the
Descent Module. The other two modules are jettisoned prior to re-entry. They
burn up in the atmosphere, so only the Descent Module returned to
Having shed two-thirds of its mass, the Soyuz reached Entry Interface
- a point 400,000 feet above the Earth, where friction due to the thickening
atmosphere began to heat its outer surfaces. With only 23 minutes left before
it lands on the grassy plains of central Asia, attention in the module turned
to slowing its rate of descent.
Eight minutes later, the spacecraft was
streaking through the sky at a rate of 755 feet per second. Before it touched
down, its speed slowed to only 5 feet per second, and it lands at an even lower
speed than that. Several onboard features ensure that the vehicle and crew land
safely and in relative comfort.
Four parachutes, deployed 15 minutes before
landing, dramatically slowed the vehicle's rate of descent. Two pilot
parachutes were the first to be released, and a drogue chute attached to the
second one followed immediately after. The drogue, measuring 24 square meters
(258 square feet) in area, slowed the rate of descent from 755 feet per second
to 262 feet per second.
The main parachute was the last to emerge. It is the
largest chute, with a surface area of 10,764 square feet. Its harnesses shifted
the vehicle's attitude to a 30-degree angle relative to the ground, dissipating
heat, and then shifted it again to a straight vertical descent prior to
The main chute slowed the Soyuz to a descent rate of only 24 feet
per second, which is still too fast for a comfortable landing. One second
before touchdown, two sets of three small engines on the bottom of the vehicle
fired, slowing the vehicle to soften the landing.