This week Mars Rising looks at what is without doubt the most perilous aspect of the entire manned mission to Mars. NASA refers to it as ‘The six minutes of terror’, 6 minutes is approximately how long it will take a manned craft to descend to the planets surface.

As narrator William Shatner explains, the dynamics of landing on Mars are a lot different from landing on the Earth, or landing on the Moon. The Moon has no atmosphere, so there is no requirement to make the craft aerodynamic, and if you think back to the Apollo days the  Lunar lander looked ungainly, with all sorts of strange things sticking out. Landing on the Earth is a different challenge, we have a dense atmosphere, so the craft has to withstand great temperatures as it hurtles toward ground, and a example of what can go wrong can be found in the Columbia shuttle disaster in 2003. This dense atmosphere though is a blessing in disguise, it acts like a breaking mechanism to help slow the craft down.

Mars is the worst of all worlds, it has a very light atmosphere, enough to generate a great deal of heat, maybe 4,000 degrees Celsius, but not dense enough to act as an effective break.

There are three distinct phases in arriving safely on the surface, entry, descent, and landing. The scariest part is that you only get one chance to do it right. There are no ‘fly by’s’, no second chances, everything must work the way it was designed.

Assuming the heat shield works and you make it through the entry phase, you still have the issue of traveling way too fast. The traditional approach would be to use a parachute to slow the craft down, but that is a gargantuan task. The lander could well be in the 60 ton range, that is equivalent to 60 Volkswagon Beetles! Parachutes are fragile, one minor problem and it is game over. Another solution would be to use rockets to slow it down, rockets though need fuel, fuel means weight, and weight is the curse of space travel.

The final stage is the actual landing, and that too is fraught with peril. The surface of Mars is an inhospitable place, the astronauts will have about 90 seconds to find a safe place. The current plan calls for support equipment to have been sent in advance to the planet, a living module, supplies, and a rover. Not only do the astronauts have to find a safe landing place, they need to have their support equipment close by. Even overshooting the target by just a few miles would be disastrous.

You can catch Mars Rising in the Science Channel, and this weeks episode Six Minutes Of Terror premiers on Tuesday November 27th at 7pm Eastern, 8pm Pacific.

Simon Barrett

http://zzsimonb.blogspot.com

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