How to catch a satellite
Standard space dockings are difficult enough, but a future ESA mission plans to capture derelict satellites adrift in orbit. Part of an effort to control space debris, the shopping list of new technologies this ambitious mission requires is set for discussion with industry experts.
ESA’s Clean Space initiative is studying the e.DeOrbit mission for removing debris, aiming to reduce the environmental impact of the space industry on Earth and space alike.
Decades of launches have left Earth surrounded by a halo of space junk: more than 17 000 trackable objects larger than a coffee cup, which threaten working missions with catastrophic collision. Even a 1 cm nut could hit with the force of a hand grenade.
The only way to control the debris population across key low orbits is to remove large items such as derelict satellites and launcher upper stages.
Such uncontrolled multi-tonne items are not only collision risks but also time bombs: they risk exploding due to leftover fuel or partially charged batteries heated up by orbital sunlight.
The resulting debris clouds would make these vital orbits much more hazardous and expensive to use, and follow-on collisions may eventually trigger a chain reaction of break-ups.
e.DeOrbit is designed to target debris items in well-trafficked polar orbits, between 800 km to 1000 km altitude. At around 1600 kg, e.DeOrbit will be launched on ESA’s Vega rocket.
The first technical challenge the mission will face is to capture a massive, drifting object left in an uncertain state, which may well be tumbling rapidly. Sophisticated imaging sensors and advanced autonomous control will be essential, first to assess its condition and then approach it.
Making rendezvous and then steady stationkeeping with the target is hard enough but then comes the really difficult part: how to secure it safely ahead of steering the combined satellite and salvage craft down for a controlled burn-up in the atmosphere?
Several capture mechanisms are being studied in parallel to minimise mission risk. Throw-nets have the advantage of scalability – a large enough net can capture anything, no matter its size and attitude. Tentacles, a clamping mechanism that builds on current berthing and docking mechanisms, could allow the capture of launch adapter rings of various different satellites.
Harpoons work no matter the target’s attitude and shape, and do not require close operations. Robotic arms are another option: results from the DLR German space agency’s forthcoming DEOS orbital servicing mission will be studied with interest.
Strong drivers for the platform design are not only the large amount of propellant required, but also the possible rapid tumbling of the target – only so much spin can be absorbed without the catcher craft itself going out of control.
Apart from deorbit options based on flexible and rigid connections, techniques are being considered for raising targets to higher orbits, including tethers and electric propulsion.
TOP IMAGE…One capture concept being explored through ESA’s e.Deorbit system study for Active Debris Removal - capturing the satellite in a net attached to either a flexible tether (as seen here) or a rigid connection. Copyright ESA
CENTRE IMAGE…Simulations of orbital debris show that actively removing large items of debris, such as entire derelict satellites, should help stabilise its population and prevent a collision-based cascade effect. ESA has performed a system study for an Active Debris Removal mission called e.Deorbit. Copyright ESA
LOWER IMAGE…All human-made space objects result from the near-5000 launches since the start of the space age. About 65% of the catalogued objects, however, originate from break-ups in orbit – more than 240 explosions – as well as fewer than 10 known collisions. Scientists estimate the total number of space debris objects in orbit to be around 29 000 for sizes larger than 10 cm, 670 000 larger than 1 cm, and more than 170 million larger than 1 mm.
Any of these objects can cause harm to an operational satellite. For example, a collision with a 10 cm object would entail a catastrophic fragmentation of a typical satellite, a 1 cm object will most likely disable a spacecraft and penetrate the International Space Station shields, and a 1 mm object could destroy subsystems. Scientists generally agree that, for typical satellites, a collision with an energy-to-mass ratio exceeding 40 J/g would be catastrophic. Copyright ESA
Here, you can surely learn to play Go because you can actually play. Enjoy!
Before you begin, please remember just 3 rules below.
- Two players (black and white) take turns, placing one stone on the board at a time.
- A stone must be placed on the intersection of the vertical and horizontal lines.
- Once a stone is placed, you can’t move it, although under some conditions it may be removed.
They are just too easy, aren’t they?
Now, you understand half the rules of Go!
Audiokinetic Jukebox: Program 2 at White Night Festival 2014
NGV Australia: The Ian Potter Centre, 7pm 22nd February to 7am 23rd February
RMIT University’s Audiokinetic Experiments lab presents Darrin Verhagen’s Audiokinetic Jukebox: Program 2, an installation at NGV Australia for White Night Festival 2014.
The Audiokinetic Jukebox is a single participant, immersive artwork integrating sound, movement, vibration and light into a multisensory aesthetic experience, developed by Darrin Verhagen at RMIT’s Audiokinetic Experiments (AkE) Lab.
The project repurposes a motion simulator which tilts a chair on an x-y axis. At its base is a transducer which delivers additional levels of fine vibration. The audience member sits in the chair, in headphones, eyes closed, with abstract visuals (driven by the music) projected directly into their faces. The end result is powerfully immersive, dynamic and stimulating.
The curated works in Program Two range from hypnotic drone through to cinematic sound design, from Noise to K-pop. Darrin Verhagen’s two pieces of Power Electronics transform the abstract assault of an extreme genre into the visceral exhilaration of vehicular travel. Robin Fox’s sinusoidal ambience and intense colourfields explore the theories that light can stimulate the pineal gland into producing DMT. Adam Hunt homages Nine Inch Nails with industrial pop which oscillates between gentle threat and gleeful violence. And James Paul blasts pop music, crafts science fiction and replaces the senses with raw stimuli.
Open one night only at the NGV Australia: The Ian Potter Centre.
The Gladiator Spider can make an expandable sticky web like a net. When an insect passes below it, it stretches out the net, lunges downwards and flings the net over the prey.
Complete Me is an action-packed text-based adventure game in which you control Hair Ghost, a ghost with hair.
Explore strange worlds in an attempt to put the hair back on your corpse, interact with scary ghosts, and do what you have to do to survive
(and so you don’t look like a bald fool at your funeral.)
You can pick up a digital copy at a pay-what-you-want price here.
Johann Georg Hagelgans. Cabalistic Map—Vision of the Second Coming. Sphaera Coelestis Mystica. 1739.
Powers of Ten™ (1977) - Directed by Charles and Ray Eames
“Powers of Ten™ takes us on an adventure in magnitudes. Starting at a picnic by the lakeside in Chicago, this famous film transports us to the outer edges of the universe. Every ten seconds we view the starting point from ten times farther out until our own galaxy is visible only as a speck of light among many others.”
Powers of Ten™ helps us to understand the relative scale of the universe by zooming out according to a logarithmic scale based on a factor of 10. Watch the second half of the video for the amazing magnification part of the film!
In this movie from NASA’s Cassini spacecraft, the gravitational pull of Saturn’s moon Prometheus creates patterns in Saturn’s F ring. This movie also happens to show a small trail of icy ring particles dragged out when a tiny object punches through the ring.
Prometheus, which averages 53 miles or 86 kilometers across, is the bright body moving up and down in the frame. The delicate strands of the F ring run across the top of the frame. The trail, made of icy particles dragged out of Saturn’s F ring, varies from about 47 miles (75 kilometers) long to 155 miles (250 kilometers) long over the course of the movie.
Scientists think the trails, also called “mini-jets” by Cassini scientists, are created when small objects about half a mile (1 kilometer) in diameter punch through the F ring and drag icy ring particles behind them. The objects creating the trails were likely originally formed by the pull of the moon Prometheus on tiny F ring particles.
As the moon works its way around Saturn, its gravitational attraction sometimes parts channels in the icy particles of Saturn’s F ring and sometimes pushes together sticky snowballs. The moon’s continued progress around Saturn pulls some of the snowballs apart over time and adds material to others. These trails appear to be the telltale signs of surviving, evolved snowballs that strike through the F ring on their own. Scientists have been able to use Cassini images to track the objects and be sure they have different orbits from the F ring. The collisions occur at gentle speeds, on the order of 4 mph (2 meters per second). The F ring is the outermost of Saturn’s main rings, with a radius of about 87,129 miles (140,220 kilometers).
Credit: NASA/JPL-Caltech/Space Science Institute