Found something else of interest to our theme here:
http://www.telegraph.co.uk/culture/...Oscars-Space-talk-The-reality-of-Gravity.html
Oscars: Space talk: The reality of 'Gravity'
The odds are on for 'Gravity' to win best picture at the Oscars. But is it sci-fi? No, says the British astronaut Tim Peake, who’s been learning all about spacewalks and orbital debris at a space-simulation facility in America as he prepares for lift-off next year
Unlike Sandra Bullock’s predicament in 'Gravity', where she is left to fall at the mercy of the laws of physics until rescued by George Clooney, there are other options open to astronauts
By Major Tim Peake
7:00AM GMT 02 Mar 2014
"At 600km above planet Earth, the temperature fluctuates between +258 and -148 degrees Fahrenheit. There is nothing to carry sound – no air pressure, no oxygen. Life in space is impossible …”
I am reminded of the opening lines to the Oscar-nominated movie
Gravity as I tumble through space. Current situation is not good: detached from structure, untethered, tumbling uncontrollably and disorientated. Moving rapidly away from the haven of the International Space Station, I am suddenly extremely thankful that this is only a simulation. In fact, this is not just any ordinary simulator. I am at a cutting-edge facility called the Virtual Reality Laboratory at the Johnson Space Centre in Houston. Here, astronauts train for a situation that is arguably their worst nightmare – drifting off into the eternal vastness of space.
Major Tim Peake next to the Apollo 10 command module (1969)
Unlike Sandra Bullock’s predicament in the movie, left to fall at the mercy of the laws of physics until rescued by George Clooney, we have one last option available. The US spacesuit that is used for conducting spacewalks is equipped with a “jetpack” called SAFER. This discharges high-pressure nitrogen gas to 24 small thrusters located around the spacesuit’s backpack. The astronauts control the thrusters using a hand controller – and if you think that sounds like something from an early James Bond movie, then you wouldn’t be far wrong.
Thankfully, the chances of finding ourselves in such a situation are slim. During a spacewalk, astronauts are protected from becoming detached by a retractable safety tether, anchored to the space station at one end and attached to the spacesuit at the other. However, this thin steel wire is a double-edged sword and astronauts must remain constantly vigilant so as not to get tangled up. In addition, there’s a mantra drilled into all of us rookie astronauts: “You stop, you drop” meaning that as soon as you stop moving from A to B, you “drop” another tether, a short strap securing you to the nearest handrail.
Under other circumstances, flying around in space with a thruster pack must rank up there as one of the most exhilarating feelings imaginable. Only a handful of astronauts have experienced this. I think one of the most inspirational photographs taken from space was during the first of these untethered spacewalks, of Nasa astronaut Bruce McCandless. This image, taken from the Shuttle, shows McCandless floating against the empty blackness of space above a stunning blue Earth. The feelings of isolation and exposure must have been immense.
However, I have no time to dwell on these thoughts. My emergency rescue scenario is extremely challenging, and the small quantity of nitrogen available for propulsion means that you only get one shot – no mistakes.
Thankfully, the SAFER is equipped with an automatic attitude hold that stops the nauseating tumbling motion that will occur if you do not smoothly detach from structure. This happened to Sandra Bullock’s character in
Gravity when high-speed debris knocked her from her shuttle and left her tumbling through space. If you’re lucky, when the tumbling ceases, you will be able to see part of the space station, or maybe Earth, as a reference point. Not so lucky, and precious nitrogen has to be expended in searching for the space station.
Having successfully located it, the nitrogen remaining is already likely to be down to around 50 to 60 per cent, and although the tumbling motion will have stopped, you are still drifting away from structure. As you get further from the space station, other factors such as orbital dynamics complicate matters.
In a nutshell, objects in higher orbits travel more slowly and those in lower orbits travel faster. This explains why our TV satellites are way out at nearly 36,000km (22,369 miles), where they orbit the Earth only once every 24 hours, matching an Earth day and therefore remaining “geostationary”. In contrast, the space station at only 350km (218 miles) altitude travels at 17,500 miles per hour in order to remain in orbit and circles the Earth every hour and a half. These orbital effects become apparent even at relatively short distances, and it is unnerving to watch the space station slipping further away as you drift into a different orbit. Time is of the essence.
My first two self-rescue attempts went well, which was a relief in more ways than one since my instructors had commented that helicopter pilots (such as me) are usually pretty good at this sort of thing – no pressure, then! For my third attempt, the stakes were raised and I was ejected into space at a faster rate and from a more remote part of the space station. Worse still, my SAFER took three attempts to initialise, by which time the space station was beginning to look awfully far away.
As I recovered the situation, a quick check of nitrogen showed a worrying 10 per cent remaining. The nearest handrail to me was off to the right and I was not convinced I was going to make it. With an arm outstretched, I decided to go in hard and fast. It worked, but only just, and I could hear my instructors in the background chuckling at their console. It had been a close call but that’s exactly what these training sessions are for.
Gravity is based on a scenario whereby a Russian satellite incurs a missile strike, causing a cascading collision cloud of space debris. This is not such a far-fetched concept and is in fact known as the Kessler Syndrome. Space debris is a big deal. There are currently more than 600,000 pieces of debris larger than 1cm orbiting the Earth.
To put this into perspective, an object of that size travelling at more than 10 times the speed of a bullet could easily punch its way through the space station and cause a rapid depressurisation. In 2009 there was a collision between an Iridium communication satellite and an out-of-service Russian military satellite. This alone produced thousands of large fragments of debris that, even years later, caused the crew of the space station to take refuge in their Soyuz escape capsule as a precaution while a fragment passed by.
Some 19,000 pieces of space debris are continuously tracked by ground radars. In Europe, this is the job of the European Space Agency Operation Centre in Darmstadt, Germany. On average the space station is required to perform a debris avoidance manoeuvre about once a year when an object threatens to get too close. It is only as a last resort, when an object is spotted too late, that the crew are required to shelter in their Soyuz until the danger has passed.
Gravity’s director, Alfonso Cuarón, said last week that the movie was not science fiction, but a drama of a woman in space. While some scenes employ “heightened reality” (propelling oneself through space using a fire extinguisher springs to mind), I would certainly agree that the movie is based on existing technology and a plausible threat that is taken very seriously.
And if you think it is only the crew of the space station who are threatened by objects in space, don’t forget that we are all hurtling through a very cluttered solar system on spaceship Earth. Only last year, a 20m-wide asteroid slipped through the net, causing an unforeseen air burst over Chelyabinsk in Russia, exploding with 20 to 30 times the energy of the atomic bomb detonated at Hiroshima. Earth has close calls from asteroids more often than you might think – and we have yet to develop our own “debris-avoidance manoeuvre”.
But I digress. This is the stuff of Armageddon… not
Gravity!
Major Tim Peake, Britain’s first official astronaut, is heading into space next year; blogs.esa.int/astronauts/
