All set for take-off

Manned Missions
Last Updated 27 May 2013, 12:58 IST

There has been a lot of buzz around manned space missions in recent times. So, what does it take to be an astronaut and be part of these manned missions to the moon and Mars at some point in the future? The biggest challenge is to be ‘weightless’ for days on end, and handle low-gravity or zero-gravity conditions, writes C Sivaram.

These are times when there is a revival of interest in manned missions to the moon and Mars. The red planet, especially after recent reports of evidence suggesting the presence of water, has become a favourite destination for planned manned space missions.

Dennis Tito, the pioneer space tourist, has announced a plan to send two people on a Mars round trip in 2018, while billionaire Elon Musk has proposed to send as many as 80,000 people to the red planet while charging them half a million dollars each! Richard Branson has similar aspirations while Lansdorp plans to land a crew of four people by 2023.

It has been more than 40 years since the last Apollo manned space flight to the moon in December 1972. A total of twelve astronauts walked on the moon.  However, the moon trips lasted only a week or so. In sharp contrast, a round trip to Mars using the lease energy would take almost three years. Typically, it takes around eight months for a spacecraft to reach Mars after the earth launch. There are called launch windows, which occur about once in two years, for Mars. This would give the optimum trajectory. So there is a waiting period on Mars for the return trip of a little more than a year, then another eight months for the return trip. Thus the total duration works out to about three years.
The astronauts would be ‘weightless’ for more than 500 days (i.e. experience zero gravity) and spend around another 500 days working in the low gravity environment of Mars, which has a surface gravity of only a third of that of the earth.

Astronauts and cosmonauts have indeed spent long durations in space stations such as Russia’s MIR and now the International Space Station (ISS). There are now regular visits by astronauts of different countries to the orbiting ISS. They spend on an average several months in the space station working under zero-g conditions. The record time spent in the MIR space station by Russian cosmonauts is three years! So, several studies have been made on astronauts exposed to low (zero) gravity for long periods of time in both MIR and ISS. Reports have been released which highlight the deleterious effects space travel has on human health during such long missions. This is important in discussing the long duration trips to Mars. While in most cases, there were only minor medical problems during the flight, the real problems began when the astronauts returned to earth. Their bodies had adapted to weightlessness for several months. For instance, the heart no longer has to work as hard to pump blood to the upper parts of the body. But the return to earth’s gravity put extra strain on their hearts; they all had low blood pressure and haemoglobin levels and had trouble standing up. More serious were the effects of microgravity on bone and muscle and they lost up to two per cent of their bone mass each month, in spite of exercising on treadmills etc.

Physical changes

This implies that after a long trip to Mars, astronauts could experience broken bones and blackouts; also they become too weak to work. Several studies of astronauts working on ISS confirmed the problem of muscle wastage. After six-month-long missions, the crew were visibly frail and their calf muscles (on average) generated 30 per cent less power. There was also a 40 per cent drop in the force of slow-twitch fibres, i.e. a drop in muscle power (equivalent to muscles of an 80-year-old person).

Again, tests on rats showed that once their muscles stop bearing body weight, the genes that code for the key proteins, myosin and actin, shut down. Also, astronauts tend to lose appetites which add to their loss of fitness. Many suggestions such as using a giant centrifuge to simulate gravity and developing pills to stop bone and muscle loss apart from special exercises have been made in the past.

Cynics point out that for the cost of a human mission to Mars, we could send about 600 robotic rovers to travel all over the terrain. Moreover, as far as Mars is concerned, statistics are bad, as out of about 40 missions to Mars, only half have succeeded in reaching the red planet. (At lease three have crash landed).

What does it take?

Finally, we come to the stringent selection of astronauts. Getting to the launch pad can be tougher than the travel itself. For instance, the European astronauts who worked on MIR during 1988-89, were selected using a screening process by French and European space agencies. The tests saw 1,065 aspirants brought down to just 13. The candidates were subjected to extensive medical and psychiatric tests. They had to have flawless vision and hearing and also be of the right size to fit into the Soyuz capsule which would ferry them to the space station.

Anyone susceptible to motion sickness would be ruled out. For this, they had to tilt torsos and heads while being spun at thirty revolutions per minute. They were also placed in a centrifuge and subjected to eight times the earth’s gravity for thirty seconds and anyone with irregular heart beat was ruled out.

There was a tilt test (no drop in blood pressure was allowed). They also had to sit in an altitude chamber (at the equivalent of ten km) and brought to sea level in thirty seconds and expected to remain conscious! There was also minimal fitness required — a 40-year-old had to run a kilometre in four minutes and ten seconds. All this was topped off with a final stiff interview. Still not enough! They had to complete a habit training programme before going to Star City for mission space training. They were subjected to monthly medical tests and placed in quarantine for the final two weeks before the actual flight!  In short, it is a long process from aspiration to actual take-off!

(Published 27 May 2013, 12:58 IST)

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