In the 2013 movie Gravity, two astronauts get stranded in outer space after their shuttle is destroyed by space debris created by a missile strike on a defunct satellite. What follows is an exhilarating story of how the two try to stay alive and return to Earth.
There is almost 7,000 tons of active space debris—from old satellites and spacecraft to lost components and spent rocket parts—orbiting Earth at any given moment. While some of the space junk in orbit decays with time, debris that is located at a higher orbit can take years to disintegrate. Take, for instance, the US Vanguard 1 satellite, launched in 1958—the oldest artificial satellite still circling Earth. Although contact with Vanguard 1 was lost in 1964, it is not expected to disintegrate before 2198.
Now, a low-cost research and development mission that will demonstrate different methods to remove active space debris is aiming to show the way in solving the problem. The RemoveDEBRIS mission, scheduled to be launched later this year, is being led by the Surrey Space Centre (SSC) at the University of Surrey, UK, and is co-funded by the European Commission and other partners, including prominent European space companies and institutions.
“The reason this is so important is because although we can simulate the space environment here on Earth and get an approximation of how moving objects behave, you can’t easily and accurately remove gravity and air at the same time on Earth, which both affect how objects naturally move in space. In order to properly understand the problem of finding, catching and dealing with space junk, we need a practice run in space,” says Simon Fellowes, the programme manager for the mission at the SSC.
As of now, the hardware for the spacecraft has been shipped to the Kennedy Space Centre in Florida, US, and is expected to be launched to the International Space Station (ISS) in a capsule on board a SpaceX rocket in March. On the ISS, the craft will be moved into an airlock and then carefully placed into orbit using the ISS robotic arm. “We expect to be operating the craft in June this year,” says Fellowes on email.
Once the main RemoveDEBRIS satellite platform is in orbit, it will showcase four methods of capturing artificial debris targets. The targets will be two CubeSats (miniaturized satellites provided by the SSC) that will be carried inside the main platform.
The first demonstration involves a net that will be deployed (net capture) at the target CubeSat. The second experiment will see the use of a harpoon, which will be launched at a target plate made of “representative satellite panel materials”. This will be a first-of-its-kind harpoon capture in orbit.
The third experiment using the other CubeSat involves vision-based navigation. Using cameras and LiDAR (light detection and ranging), the platform will send data about the debris back to the ground for processing.
The final experiment will see the RemoveDEBRIS spacecraft deploy a large dragsail to speed up its de-orbiting process. As it enters Earth’s atmosphere, the spacecraft will burn up, leaving no debris behind. “We don’t have much time to run the experiments in space because we intend to deploy the de-orbit sail around November. After the de-orbit sail is activated, we anticipate the RemoveDEBRIS craft will rapidly reduce height and finally burn up in the atmosphere,” adds Fellowes.
The mission, which started five years ago, aims to be a forerunner of missions to start removing some of the largest objects in space. Fellowes says that since this is a demonstration project, the cost (around €15 million or Rs117 crore) is low for a mission of this value.
Space debris problems and theories (like the Kessler Syndrome) about a cascade of collisions have reached such proportions that the ISS recently installed a “space debris monitor sensor” that will measure the size, speed, direction, time and energy of small debris affecting the sensor and the ISS.
Fellowes says the information gathered from this mission, and the experience, will be fed into follow-on missions to deal with targeted objects.
As we push into the final frontier, we are leaving our mark. We have already left more than 400,000 pounds of human-made material on the moon. Rovers and bits of defunct orbiters litter the surface of Mars. And scientists have sent robotic spacecraft hurtling out past Pluto with no final destination.
In our own cosmic backyard, space trash abounds. Between abandoned satellites, pieces of old spacecraft, and spent rocket stages, more than 21,000 pieces of debris orbit Earth. The threat of such debris colliding with expensive satellites or careening to Earth has prompted some wild ideas to tidy the immediate area of space surrounding our planet. Those ideas have ranged from slingshots and nets to gecko-like sticky pads and lasers.
As we explore beyond our own backyard, the stuff we leave behind may not have an effect on us as directly. So should we care? Is it our ethical responsibility to minimize the space junk that we leave in the rest of the solar system? The answers hinge on how humanity chooses to ascribe value to things like life, the natural world, and the unknown potential and desires of of future generations.
We can’t yet travel around the solar system picking up after ourselves. But we can minimize what we leave behind, scientists say. Some probes, like NASA’s Stardust mission to sample a comet’s dust, can return to Earth at the end of an exploration. For more far-flung missions, scientists have sent spacecraft to a fiery end in a planet’s atmosphere, as they did at the end of the Cassini mission in September.
When we make the decision to protect a place from our mission leftovers, it highlights what we consider to be worth preserving. Current international planetary protection policies place a high priority on preserving places where there might be life.
Guidelines set in the Outer Space Treaty of 1967 direct signatories to minimize contamination of potentially life-bearing worlds. Although these international guidelines are not binding, NASA’s policy aligns with them and scientists are expected to incorporate detailed planetary protection plans into end-of-mission plans for places where there might be life or habitable worlds.
That was the case with NASA’s Galileo mission to Jupiter, says John Rummel, a former NASA Planetary Protection Officer who is now a senior scientist at the SETI Institute. When the probe began to show signs of falling apart, mission scientists worried that they could soon lose control of its trajectory. That possibility was particularly troubling given scientists’ growing suspicion that Jupiter’s moon Europa could be habitable. Furthermore, modeling suggested that Galileo might even be jostled out of Jupiter’s orbit by other satellites if left to its own devices.
“Do you really want to have 36 pounds of plutonium wandering around on its own? Everybody agreed that that was probably not a good idea,” Dr. Rummel says. So he and fellow mission scientists directed Galileo to crash into Jupiter’s atmosphere where it burned up. That plan spared the potentially habitable Europa.
But does responsible stewardship of our solar system only extend to places where life can thrive?
“We should be in the business of protecting what you might call the integrity of these places,” says Tony Milligan, a professor of philosophy and ethics at King’s College London. “There’s something about the uniqueness and the history of these places which makes them worthy of our consideration.”
For some, the potential for scientific discovery adds inherent value to every spec of the universe. For others, the intrinsic beauty of heavenly bodies makes them equally worthy of protection as any canyon or river on Earth. And others still, associate an abstract sense of wrongness when it comes to destruction of nature, here or elsewhere.
“There is an argument to be made for the intrinsic value of nature, that rocks and rivers, whether on Earth or on Mars, have an intrinsic value to them and that there should be some degree of regard for that value,” says Margaret McLean, director of bioethics at the Markkula Center for Applied Ethics at Santa Clara University.
Dr. Milligan points to a thought experiment frequently used by environmental ethicists known as the last man argument. Envision that the last human alive decides to level Mars’ Olympus Mons, the tallest mountain in the solar system, he says. Although it wouldn’t harm humans or any other lifeforms, most people react poorly to that idea. “It just looks as if they’re doing something wrong,” he says.
But mining dead space rocks for resources has also been seen as a way to clean up our own planet while sustaining a ballooning and advancing human population on Earth. “A lot of people are all for solar system mining if it’ll shut down the mine around the corner that is leaching materials into the river,” Rummel says. And if we can extract resources without upsetting the balance of another planetary environment, “I’m all for it,” he says.
So how, then, do we decide what to prioritize?
One generation’s trash …
“How we value things is a sliding scale,” says Dr. McLean. “We have a greater obligation to another human being than we do to a rock.”
That obligation extends to future generations. But how do we know what they will value?
Today, much of society places value in the pristine nature of wilderness. One could argue that a similar kind of wilderness experience applies to, say, the Valles Marineris canyon system on Mars. Future generations might want to hike in a pristine Martian canyon system.
Or they might actually value our space trash, “one era’s debris can be another era’s historic object,” Milligan says. The stuff we’ve left on the moon and are leaving on Mars may be seen by future generations as valuable monuments to human achievement worthy of protecting, too.
Or perhaps they, too, might want to mine ores and other resources found in space, and if we plunder it all right away, what will be left for them?
So what do we do?
When exploring, “leaving no trace is impossible,” says Margaret Race, a senior research scientist in planetary protection at the SETI Institute. “If you really want to have it be pristine, just don’t go.”
And space policy discussions make the assumption that we’re going to explore outer space.
So “what we’re asked to do is to balance the risk with the benefit that we may gain, and to do so in a way that minimizes the risk,” McLean says. And, she says, the interdisciplinary planetary protection dialogues that governments and scientists already engage in are good conduits for finding that balance.
Far above your head right now, whizzing across the majestic canvas of space at 17,500 mph (28,200 km/h), is a load of garbage.
More than 500,000 pieces of human-made debris — colloquially known as “space junk” — orbit the Earth at any given time, NASA reported in 2013. At least 20,000 items in this extraterrestrial scrap heap are larger than a softball, and can include such massive detritus as entire defunct satellites and abandoned launch vehicles.
Such huge obstacles naturally pose a danger to new space missions, according to NASA. But just as dangerous are the many millions of pieces of debris that are so small they can’t even be tracked. “Even tiny paint flecks can damage a spacecraft when traveling at these velocities,” NASA officials wrote. “In fact, a number of space shuttle windows have been replaced because of damage caused by material that was analyzed and shown to be paint flecks.” [10 Futuristic Technologies ‘Star Trek’ Fans Would Love to See]
As more space missions (and more space junk) enter orbit every year, the need to clean up Earth’s outer atmosphere grows ever more pressing, scientists say. Researchers previously proposed using magnets, ultrathin nets and giant harpoons to tackle the trash problem. How to clean up the smallest debris — the millions of particles that are less than 10 cm wide — is a trickier question to answer. Now, in a new paper published in the February 2018 issue of Optik – International Journal for Light and Electron Optics, researchers at the Air Force Engineering University in China propose a solution: just blast the junk with satellite-mounted lasers.
This NASA graphic depicts the amount of space junk currently orbiting Earth. The debris field is based on data from NASA’s Orbital Debris Program Office. Image released on May 1, 2013.
The study researchers ran multiple numerical simulations to model how the orbital path of space debris could be affected by radiation from space-based lasers. Essentially, the idea is to lower the orbital path of the debris enough so that it re-enters Earth’s atmosphere, below about 120 miles (200 kilometers) above the surface, where it would burn up.
The models showed that orbital measurements called inclination, which describes the angle between the plane of orbit and Earth’s equator, and right ascension of ascending node (RAAN), which describes the angle between Aries and the satellite as it crosses Earth’s equator while passing from the Southern to Northern Hemisphere, proved crucial to the calculations. According to the models, small-scale debris cleanup proved most effective when the RAAN of the space-based laser stations matched the RAAN of the debris.
While these resultsmake a strong theoretical case for using space-based lasers as a viable means of cosmic cleanup, the idea of laser junk removal is not new. In 2015, Japanese scientists proposed adding a trash-blasting laser to the country’s Extreme Universe Space Observatory module on the International Space Station, as well as developing a new satellite-mounted laser specifically for debris removal. Using a so-called coherent amplification network laser — which focuses many small lasers into one powerful beam — the satellite could vaporize thin layers of matter off of any debris it encountered, researchers said, forcing the junk downward to burn up in Earth’s atmosphere.
China’s willingness to experiment with rapid debris removal is appropriate considering that the country is considered one of the worst offenders when it comes to space junk, Universe Today reported. In 2007, a Chinese anti-satellite missile test was responsible for what is considered the most severe fragmentation of space junk in history, Space.com previously reported. The incident spewed thousands of new pieces of junk into low Earth orbit, one of which appeared to damage a Russian spacecraft in 2013.
A commercial cargo capsule owned by SpaceX concluded a month-long resupply trip to the International Space Station on Saturday, wrapping up the 13th round-trip flight to the station by a Dragon spacecraft with an on-target splashdown in the Pacific Ocean west of Baja California.
Bringing home 4,078 pounds (1,850 kilograms) of disused equipment, spacesuit gear and spacewalk hardware, and scientific specimens, the Dragon capsule splashed down in the Pacific Ocean at 10:37 a.m. EST (7:37 a.m. PST; 1537 GMT) after a blistering hot re-entry through Earth’s atmosphere.
Traveling northwest to southeast, the unpiloted spaceship plunged through the atmosphere protected by a heat shield surrounded by red-hot plasma as temperatures reached 3,000 degrees Fahrenheit (1,650 degrees Celsius).
Two drogue parachutes deployed to stabilize the Dragon capsule for its final descent, then three 116-foot-diameter (35-meter) orange and white main parachutes unfurled to slow the spaceship for a gentle splashdown at sea, where SpaceX recovery teams were waiting to approach the craft and hoist it aboard a boat to return to port in Southern California.
SpaceX confirmed the successful splashdown of the capsule on Twitter. The return marked the end of SpaceX’s 13th operational resupply flight to the space station under contract to NASA. Twelve of the missions have been successful, in addition to a round-trip test flight to the orbiting complex in 2012.
NASA has awarded SpaceX a contract for 20 cargo missions through the end of 2019 — with 13 now in the books — and the space agency has a follow-on agreement for at least six more Dragon resupply flights from 2020 through 2024.
Time-sensitive refrigerated specimens, such as blood and urine, and live rodents that returned to Earth inside Dragon for an experiment investigating muscle wasting in microgravity will be handed over to scientists in the next couple of days. The rest of the cargo will be unloaded from the Dragon’s pressurized module and turned over to NASA and research teams once the capsule travels to SpaceX’s test facility in McGregor, Texas, for post-flight processing.
Other items packed inside the Dragon by station astronauts included specimens from a plant growth experiment that studied how vegetation responds to reduced oxygen, which can occur in flooding on Earth.
The commercial company Made in Space also sent up a privately-funded technological experiment to study how optical fiber could be produced in orbit — perhaps with better quality than the silica-based fiber optic cables manufactured on Earth. The results were aboard Dragon on the trip home Saturday.
The Dragon capsule lifted off Dec. 15 aboard a Falcon 9 rocket from Cape Canaveral, and it arrived at the space station two days later with 2.4 tons of food, supplies and experiments.
The Dec. 15 launch was the first time NASA has entrusted cargo to launch on a previously-flown Falcon 9 rocket booster. The mission also used a recycled Dragon cargo module that first flew on a trip to the station and back in April and May of 2015.
According to NASA, there are more than 500,000 pieces of debris, or space junk orbiting the Earth. At least 20,000 of those objects are larger than a softball. All of the objects, which travel at speeds up to 17,500 mph, pose potential dangers to satellites orbiting the Earth, both now and in the future.
One way to potentially reduce these hazards, and the costs and risks of launching new satellites, would be to build and launch an on-orbit recycling system. Notionally, the system would have the ability to vaporize small existing space debris; recycle and recover manufacturing materials from existing satellites; and even perform in-space manufacturing of structural elements for new satellites.
“Think of this space recycler as an on-orbit refinery, powered by that amazing source of energy in space called the sun,” said Howard Eller, Advanced Missions Tech Fellow, Northrop Grumman Aerospace Systems.
Bringing the Sun into Focus
In its basic form, the recycler would include a large parabolic reflector, perhaps 50 to 100 feet in diameter; a spherical crucible made of material with an extremely high melting point; a set of compartments in which different types of salvaged materials could be stored; and several robotic
arms for capturing “dead” satellites or other space debris.
The recycler’s reflector would concentrate solar energy into a small spherical space, creating an intense source of heat. The heat could be used either to simply vaporize existing small debris, or to heat larger pieces of space debris in the recycler’s crucible. The crucible could be rotated through the thermal flux like a rotisserie grill to heat the debris to a desired and uniform temperature.
Using this approach, explains Eller, “we could selectively melt and capture material of type A, heat the crucible more to melt and capture material of type B and so on.”
Materials melted and captured at each stage of the recycling process could be stored in separate compartments in the form of ingots, or perhaps piped in real time to another part of the recycler as source material for in-space manufacturing operations. Any unneeded leftovers from the recycling process could be compressed into small pieces and vaporized by the solar concentrator.
There could also be self-sustaining aspect to this recycler, adds Eller. “If the mirrored surface of the solar concentrator became contaminated, the recycler could vaporize a piece of scrap aluminum in such a way that material is deposited as a new thin and highly reflective layer on the mirror, effectively recoating it,” he said.
Scavenging the Graveyard
An ideal source of dead satellites for the recycler would be so-called “graveyard” orbits several hundred kilometers above geosynchronous (22,500 miles) altitude. Satellites are typically safe-d (batteries drained, propellant tanks emptied) and placed in a graveyard orbit at the end of their operational lives to reduce the chance of colliding with an operational spacecraft.
According to Eller, a recycler could either be placed in a relatively fixed location in orbit where dead satellites could be brought for recycling, or the entire facility could maneuver from satellite to satellite in a graveyard orbit. In theory, an in-space 3-D manufacturing facility could be attached to the other end of the recycler. As old satellites are ingested (think PacMan) and converted to raw materials, new satellite structures would be produced and pushed out the other end for in-space assembly.
Smarter, Lighter, Cheaper
The ability to perform on-orbit recycling and manufacturing could also enable a new generation of simpler, lighter and potentially more capable satellite systems. Free from the impact of gravitational forces during launch, satellites could be assembled in space using simpler designs and materials with far less mass and structural strength. As a result, they might look very different from traditional spacecraft buses, which are essentially boxes with one or more solar array appendages.
“If we built a satellite in space, it could be a single panel of any desired length,” explains Eller. “One side could be an array of RF [radio frequency] elements and electronics, like a single large circuit board. You could produce additional panels to serve as solar arrays, or perhaps attach solar cells to the back of the original panel.”
After building this “panelsat” in orbit, you could plug in a module launched from Earth containing all of the electronic components that are currently too difficult to produce in space.
Working the Vision
In the end, admits Eller, space recycling is a vision that should be driven by economics. It makes perfect sense to recycle existing satellites because they are made of the materials most often needed to make new satellites. “But right now there is no financial incentive to get rid of space debris,” he says. “That’s why we should develop this or similar concepts as a nation. If we can figure out a way to convert dead satellites from a waste product into an economic benefit, recycling in space will happen.”
China’s Tiangong-1 space station is currently out of control and is expected to fall back to Earth sometime in March this year. It was launched in 2011 as China’s first space station. The following year, it was visited by China’s first female astronaut Liu Yang. The space station’s orbit is decaying as it heads towards a fiery re-entry into earth’s atmosphere. The space station weighs about 8.5 tonnes and is currently orbiting 370 km above ground. It is claimed to have fulfilled its mission’s objectives.
The Tiangong-1 space station is expected to mostly burn up and unlikely to affect aviation or cause much damage on the ground. A large portion of the space station could melt as it passes through the atmosphere, but some denser parts such as the engines may not burn up. As the Chinese engineers have lost control and cannot fire the thrusters to bring it down in the South Pacific, it is expected to come down, anywhere between Spain and South Australia. It is difficult to be more precise until a few hours before the burn up. However, the Tiangong-1 space station isn’t the only one that has problems for its descent.
On July 11, 1979, the US space station, Skylab I, tumbled back to Earth, scattering debris across the southern part of the Indian Ocean and sparsely populated western Australia. It finally struck the Australian coast. Skylab was America’s first space station, launched in May 1973. The space station that weighed around 80 tonnes was without crew. The 37-tonne Salyut 7 space station by the Russians came down in South America in 1991. The 140-tonne Russian space station, Mir, that was visited by many teams of cosmonauts was directed down into the South Pacific in 2001, and it was last seen by some fishermen as a fragmenting mass of glowing debris racing across the sky. It survived increased solar activity (unlike Skylab I), lasting 20 years.
One future space station, which is expected to be brought down, is none other than the International Space Station (ISS). It has already been up 15 years and is expected to be decommissioned over the next decade. With a mass of 450 tonnes it will make a spectacular sight on re-entry sometime in 2024 or 2025. Many times a year, supply ships that go to the ISS to replenish food, water and other essentials for the astronauts staying in the station, also come crashing down, with a controlled re-entry into the atmosphere.
Graveyard of satellites
It is interesting that over the years, many large spacecrafts have been brought down over a controlled re-entry path into a region in the South Pacific called the ‘oceanic pole of inaccessibility’, that is, an area in the ocean furthest away from land. It lies in the south Pacific around 2,000 km from the South Pitcairn island, a literal no man’s land between Australia, New Zealand and South America.
Scattered over an area of about 1,000 sq km on the ocean floor, this region is a graveyard of various decommissioned satellites, space stations, and other spacecrafts. At last count, around 300 spacecrafts have crashed here. While smaller satellites will burn up, the big pieces of the larger ones, like space stations, will survive to reach the earth’s surface. To avoid crashing in a populated area, they are brought down near the point of oceanic inaccessibility.
However, re-entries done by space stations such as Tiangong-1 face the threat of being hit by some of the man-made trash that are currently orbiting earth. Some are tiny, some are large enough to be seen by telescopes, all pose great risk to orbiting spacecrafts and satellites. The danger is growing as space (around earth) is getting more crowded. Around 25,000 pieces of space junk are big enough to be tracked by the space surveillance network. But most of the debris are under 10 cm in size and cannot be detected.
Even those which are the size of a paper clip can cause great damage. For instance, a loose fleck of paint caused a crack in the window of the ISS. Though such collisions are rare, half of all dusty junk is caused by debris from two events in 2007. China destroyed one of its own satellites with a ballistic missile, shattering it into thousands of pieces. In 2007, an American commercial satellite collided with a defunct Russian satellite. Even last year, debris from that collision forced the crew of the ISS to evacuate to the Soyuz capsule. Such debris will remain in earth’s orbit for several years.
More than 7,000 satellites have been put in space, but currently only 1,000 are functioning. Within the next decade, the number of satellites could double to 20,000 with planned launches of mega constellations, a large group of satellites to improve global communication coverage, etc. Objects follow different orbits and can cross paths. Satellite technology is necessary for a whole range – from weather to GPS.
Space junk mission
While Tiangong-1 is falling down, Britain is set to launch the ‘Remove Debris: space junk mission’. It will attempt to snare a small satellite with a net and test whether a harpoon is an effective garbage grabber. As stated, over 7,500 tonnes of junk is orbiting Earth, ranging from huge defunct satellites, spent rocket boosters to nuts and belts. Perhaps about a million pieces of such space garbage collisions can cause enormous damage, generating even more pieces of debris, putting spacecrafts and astronauts at risk.
The RemoveDebris mission will first head to ISS on one of the resupply rockets. It has its own space junk on board – small satellites. It will release one of them into space and then will use a net to recapture it. A small harpoon would be fired at a target to see if it can accurately work in a weightless environment. It will finally test future de-orbiting technology. Then, when it descends, it will deploy a large sail to change the spacecraft’s speed to ensure that it burns it up. Earlier, a Japanese magnetic space junk remover did not work as expected.
In short, the increasing space activity in the next decade is expected to multiply space debris in orbit posing risk to astronauts and those of us on ground. Space garbage disposal and its detection are pressing problems that need to be looked into to avoid any untoward situation.
THERE is an awful lot of junk in space. The latest data from the European Space Agency suggest some 7,500 tonnes of it now orbits Earth. It ranges from defunct satellites and rocket parts to nuts, bolts, shards of metal and even flecks of paint. But something as small as a paint fleck can still do serious damage if it hits a working satellite at a speed of several thousand kilometres an hour. There have already been more than 290 collisions, break-ups and explosions in space. Given the likelihood that thousands of small satellites, some only a few centimetres across, will be launched over the next decade, many worry that large volumes of space near Earth will soon be rendered risky places for satellites (especially big, expensive ones) to be.
What is needed, then, is a clean-up. Various ideas about how to do this have been proposed, and some are about to be put to the test. In February a resupply mission to the International Space Station will also carry a satellite, about the size of a domestic washing machine, called RemoveDEBRIS. Once this has been unpacked and prepared by the station’s crew, they will use a robotic manipulator to send it on its way into orbit around Earth.
RemoveDEBRIS has been designed and built by Surrey Satellite Technology, a British manufacturer of small satellites spun out of the University of Surrey in 1985, which is now majority-owned by Airbus. Mission Control for the RemoveDEBRIS project is the Surrey Space Centre at the university. The plan is for RemoveDEBRIS to carry out four experiments. The first two will involve launching from it a pair of CubeSats (mini-satellites 10cm across). These will play the role of space junk.
Once launched, the first CubeSat will inflate a balloonlike structure a metre across, to which it will remain attached, in order to create a bigger target. The mother ship will then approach to a distance of seven metres and fire a net at the balloon. This net is designed to unfurl and warp itself around the target. Once the target is entangled, a cable connecting the net to the mother ship will be tightened, closing the neck of the net. It will then be hauled in, like catching fish.
The second CubeSat will test the sensors of RemoveDEBRIS. This trial will use cameras and a lidar (an optical version of radar) aboard the mother ship to build up a detailed three-dimensional image of the object. If that works it will permit future clean-up vehicles to recognise what they are dealing with, and react appropriately.
In the third experiment, RemoveDEBRIS will extend a 1.5-metre-long arm that holds a 10cm-square target. It will then fire a harpoon at the target. The idea is that harpoons could be used to pierce some items of space debris and, like the net in the first experiment, then haul them in. The final experiment is intended to ensure that RemoveDEBRIS and its captured items do not themselves become space junk. The mother ship will deploy a ten square-metre plastic membrane, supported by four carbon-fibre booms, to act as a “dragsail” that will employ the limited atmosphere at this altitude to pull the craft downward to the fiery death of re-entry.
If space-debris capture systems like this succeed, then future missions could start to go after some of the most worrying bits of junk. Such ventures could be commercial, according to Guglielmo Aglietti, director of the Surrey Space Centre, if governments (probably acting collectively) were willing to pay to keep space clean so as not to damage their own activities and those of their citizens. There are already guidelines to try to limit the accumulation of space junk. Defunct satellites should be disposed of within 25 years, either by being tipped into re-entry or parked in an out-of-the way “graveyard” orbit. But the rules are not always followed and a lot of older debris remains in orbit. A bounty on removing the most threatening hulks might even see the launch of a new space business.
This article appeared in the Science and technology section of the print edition under the headline “Junk hunting”
Space may be big, really big, but Earth orbit is getting a bit crowded as space debris accumulates and threatens operational spacecraft. Riding aboard the last Dragon cargo mission to the International Space Station was part of the answer to this problem. NASA’s Space Debris Sensor (SDS) will be installed on the outside of the station, where it will spend the next two to three years monitoring debris between 5 mm to 0.5 mm in diameter to learn more about their characteristics.
Currently, there are over 1,400 operational satellites orbiting the Earth at distances from a few hundred to tens of thousands of miles above the planet. Over the past 60 years since the first Sputnik, our civilization has become completely dependent on these satellites. Without them, everything from the internet to commerce to national defense would be crippled overnight. Today, we depend on satellites for much of our long-distance communications and data transmission, weather monitoring, navigation, defense reconnaissance and many scientific investigations.
The problem is that over the decades many of these satellites have died and the rockets that launched them into space are also often in orbit, along with a great deal of miscellaneous space debris. This miscellaneous junk is the result of spacecraft breaking apart, including booster upper stages shredding themselves after over-pressurizing their tanks or the propellant inside vaporized, satellites blowing up when their discharged batteries generate volatile gases and droplets of solidified metal coolants from old Soviet nuclear-powered satellites.
According to NASA, there’s over 170 million items of debris ranging from discarded boosters to flecks of paint. In all, there are over 5,500 tonnes of debris circling the Earth with 98 percent made up of 1,500 objects in low Earth orbit. These include not only dead satellites and boosters, but a glove lost by US astronaut Ed White during his historic Gemini 4 spacewalk in 1965, a camera lost by Michael Collins on the Gemini 10 mission in 1966 as well as another lost by Sunita Williams of STS-116, a thermal blanket lost during STS-88 in 1998, 15 year’s worth of rubbish bags from the Russian Mir space station, a pair of pliers, a US$100,000 tool bag and the ashes of Star Trek creator Gene Roddenberry.
The potential damage from this debris as it travels at about 22,000 mph (35,400 km/h) is huge with even particle as small as 3 mm posing a threat to manned and unmanned spacecraft.
“Debris this small has the potential to damage exposed thermal protection systems, spacesuits, windows and unshielded sensitive equipment,” says Joseph Hamilton, the SDS project principal investigator. “On the space station, it can create sharp edges on handholds along the path of spacewalkers, which can also cause damage to the suits.”
It’s pretty common for old satellites and other “space junk” to come falling back down to Earth. While hundreds of pieces of debris come down each year, scientists are nervously watching a 19,000-pound space station’s course because its out-of-control route is making it impossible to figure out where it will crash.
The Chinese space lab, named Tiangong-1, is set to crash back down into the planet at some point in March. China reportedly lost control of the lab nearly two years ago in June of 2016. The Chinese government later released an estimate that predicted Tiangong-1 would come down at some point in late 2017. The vague guess has led experts to conclude that the country’s space agency has lost all ability to direct the crashing station’s course or know where it will land.
“Even a couple of days before it re-enters we probably won’t know better than six or seven hours, plus or minus, when it’s going to come down,” Harvard astrophysicist Jonathan McDowell told The Guardian in 2016. “Not knowing when it’s going to come down translates as not knowing where its going to come down.”
According to reports, there’s only a 1-in-10,000 chance that the massive space lab will actually crash into a populated area and damage buildings. While the odds are slim, scientists have only been able to narrow the crash zone down to between the 43° North and 43° South latitudes; an area that still includes parts of every inhabited continent on Earth.