Re-entry option if spacecraft hits problems

PUBLISHED : Sunday, 28 September, 2008, 12:00am
UPDATED : Sunday, 28 September, 2008, 12:00am

Scientists have made plans for an alternative 'ballistic re-entry' should the Shenzhou VII spacecraft encounter problems similar to those that endangered two Russian Soyuz landings in the past few months, a mainland flight controller said yesterday.

A ballistic method is employed during an emergency and relies wholly on the atmosphere to slow the capsule's re-entry into the Earth's atmosphere.

The procedure means astronauts must endure a gravity overload that makes their bodies eight times heavier than normal and risks missing their landing zone by hundreds of kilometres.

Zhou Jianliang , deputy chief engineer at the Beijing Flight Control Centre, said Shenzhou VII's design was similar to the Soyuz TMA, whose latest two journeys back to Earth ended in extreme discomfort and physical injury to their crews.

Dr Zhou said mission control was fully aware of the implications of the last two Russian re-entry mishaps and was doing all it could to avoid a recurrence.

He would not elaborate on the exact problem.

'Please understand that such information can only be released by relevant authorities. It is a problem of their [Russian] ships,' Dr Zhou said.

'Shenzhou and Soyuz share some similarities but we are prepared. Normally, there should be no problem with a lifting entry [one that employs aerodynamics to provide a gentler experience for astronauts]. But if a problem occurs, we can still bring our boys back safely through a ballistic entry.'

Both Shenzhou and Soyuz spacecrafts are comprised of an instrument module, orbiter module and a re-entry capsule.

When the mission is completed, the orbiter module separates from the spacecraft with an explosion that severs connecting bolts. Then rockets on the instrument module, attached to the re-entry capsule, fire to reduce orbital speed enough to allow gravity to pull the spacecraft into a safe trajectory for re-entering Earth's atmosphere.

The timing of retrorocket firings and the attitude of the spacecraft are key to a successful planned landing.

After retrorockets are fired, the instrument module separates from the re-entry capsule.

It is widely suspected that at that last stage of separation in the Soyuz re-entries, a problem occurred and the two modules entered Earth's atmosphere still joined.

Russian space authorities admitted that that had happened last year but kept silent about a second incident in April this year, after which a South Korean astronaut was admitted to hospital.

In an interview with the South China Morning Post last week, China Institute of Aerodynamics senior researcher Jia Quyao said the problem could be rooted in the returning capsule's aerodynamics.

The mainland space authority said it had nearly doubled its search and rescue capabilities with more fighter jets, helicopters, ships and ground vehicles.

The first flight of Soyuz TMA occurred in October 2002. When it returned to Earth in May 2003, a problem forced it to carry out re-entry in ballistic mode and land 460km away from its target zone. Its astronauts were not hurt.

A similarly troubled Soyuz re-entry occurred in October last year, with the crew surviving after being forced to endure days in the wilderness, surrounded by wolves, after landing off target.

A third mishap followed five months later. The capsule had to undergo a steep descent and huge deceleration that injured the back of Yi So-yeon, the first South Korean astronaut, seriously enough to require months of hospital treatment.