Houston, we have a garbage problem
Even non-astronomers with a naked eye occasionally discover unusual things in a nighttime sky: brightly shining flying objects that at first glance seem to resemble the beauty of shooting stars. Responsible for them is an equally enigmatic, albeit controversial, American multi-entrepreneur called Elon Musk. His Starlink satellites spin around our planet like an independent web of stars.
According to “Jonathan’s Space Report,” Musk’s SpaceX company in the middle of January this year owned 3,374 of these artificial flying objects in the orbit, and 3,338 of them were active. Growth of that sector is remarkable. In 2019, SpaceX only had 67 satellites in orbit, according to online space news source Spaceflight Now. Today, their number has increased 50-fold. Thousands of other ones are planned to follow. The responsible U.S. government agency FCC just recently approved the deployment of 7,500 second-generation Starlink satellites.
The SpaceX example illustrates the fact that space is becoming an increasingly busy place. Rockets are shooting new satellites into Earth’s orbit almost on a weekly basis. Since Sputnik rang in the race to space in 1957, around 6,400 rockets (as of December 2022) have lifted off and hauled more than 15,000 satellites into the universe, according to information released by the European Space Agency (ESA). Around 9,800 of them are still in space – and about 7,200 of those are still functional. They cover a wide variety of uses: from weather reports and climate data to telecommunications to navigation – everything is handled via outer space. The remaining number of roughly 2,600 satellites have either completed their mission or are defective. They would in fact have to be caused to fall back to Earth so that they would ablate upon re-entering the Earth’s atmosphere. Otherwise, there is a risk of them increasing the amount of space debris by colliding with other objects. The problem is that there is no international space legislation yet. Many satellites are left to their own devices.
the French military reconnaissance satellite “Cerise” was struck by a piece of debris from an Ariane rocket that had exploded ten years earlier. The impact speed was 50,000 kilometers (31,000 milies) per hour.
China deliberately pulverized an obsolete satellite, resulting in 3,000 larger pieces of debris in space.
two satellites collided with each other for the first time – the American communications satellite “Iridium 33” and the Russian military reconnaissance satellite “Kosmos 2251.” The impact speed at an altitude of nearly 800 kilometers (500 miles) was almost twelve kilometers (7.5 miles) per second. The energy released by the crash corresponded to roughly ten metric tons (11 short tons) of TNT explosives. The satellites burst into an estimated number of 100,000 single pieces with a size of one centimeter (0.4 inch) and more.
at an altitude of about 400 kilometers (250 miles), more than 220 dangerous encounters occurred between the international space station ISS and space debris.
More space activities, more garbage
The challenge of managing astro-garbage is not expected to diminish as more and more companies are pushing into cosmic spheres. While government organizations such as ESA and NASA still account for the lion’s share of the worldwide space investments of roughly 78 billion euros in 2021, private-sector players are increasingly reaching for the stars as well. In 2021, companies like SpaceX, Amazon founder Jeff Bezos’ Blue Origin and many others invested 13 billion euros, according to ESA – equating to around 14 percent of global space investments. By 2040, say U.S. investment bankers from Morgan Stanley, sales in the space industry are expected to roughly triple from around 340 billion dollars in 2016 to more than one trillion. Experts estimate that space start-ups around the globe are planning to launch 100,000 satellites into space in the next ten to 15 years.
Behind the United States and China, which has the second-largest number of satellites in space after the U.S., countries and regions that have so far developed little thrust are aiming to join the action in Earth’s orbit. Rwanda, for instance, is gearing up to become a center of an African space industry, having launched initial satellites in 2019. The ambitious aim of the Ruanda Space Agency is to shoot another 330,000 satellites into space. Awesome numbers!
In addition, there are many other activities taking place in space: French startup Space Cargo Unlimited, for instance, is planning to open an uncrewed space factory in 2025. “Space offers ideal conditions for producing more efficient products,” says businessman Nicolas Gaume. “New Space” is the name of that journey on which the space industry has embarked. At the end of 2022, the private space company ispace embarked on a trip to the Moon. By 2040, the Japanese startup is planning to build a city on Earth’s satellite. NASA’s lunar mission Artemis (see info box below) is in full swing as well. There’s a lot going on up there above our heads – and that entails major risks. The space explorers are only realizing at a late stage of the game that they’ve been underestimating the astro-garbage problem for a long time.
Collisions have the explosive force of ten metric tons (11 short tons) of TNT
Even at this juncture, experts are afraid that due to the large amount of astro-garbage space flights may hardly be feasible anymore unless corrective action is taken. At a speed of several tens of thousands of kilometers per hour, even the tiniest particles turn into destructive projectiles. That means that the damage resulting from a crash with an extremely expensive high-tech satellite can easily be in the range of billions of euros or dollars. Not to even mention the disastrous consequences that a collision with astro-garbage might have for astronauts.
“When an aluminum ball of just one centimeter in diameter strikes a satellite, it has the energy of a mid-range car driving into it at about fifty kilometers per hour.”Heiner Klinkrad, Space Debris Manager at ESA
The Kessler syndrome – developed by then NASA employee Donald J. Kessler in 1978 – describes the risk that the debris in orbits around the Earth multiplies in a chain reaction – each collision generates new debris and the larger the number of debris the higher the probability of collisions. Most collisions occur when small objects encounter large ones. Kessler warned of a self-intensifying cascade effect resulting in exponential growth of debris. At some point – Kessler mentioned around one hundred years – any crewed space flight would be impossible due to an excessive collision risk.
According to the German Aerospace Center (DLR), many pieces of debris are located at an altitude of around 36,000 kilometers (22,400 miles) and more, where they pose a risk primarily to TV and telecommunications satellites in a so-called geostationary orbit. But even in the low Earth orbit, i.e., up to an altitude of 2,000 kilometers (1,240 miles), tens of thousands of hazardous pieces of astro-garbage are circulating our planet.
Things rushing through the orbit as garbage:
Pieces of debris bigger than ten centimeters (four inches) have been registered by ESA in space at the end of 2022. However, not all objects are catalogued by space monitoring networks. In total, estimates ESA, around 36,500 pieces of astro-garbage bigger thn ten centimeters are shooting through the orbit. Typical of such derelict objects are disused upper stages of rockets, deactivated and destroyed satellites and tools lost by astronauts.
smallest parts larger than one centimeter (0.4 inch), scientists estimate based on statistical model calculations, are whirring through the orbit. Another 130 million of these tiny particles are supposed to be only slightly bigger than one millimeter (0.04 inch). Those particles may be frozen fuel residues or chipped paint. More than likely, the miniature pieces of debris that are unaccounted for amount to far more than 130 million.
More than 640
events have been recorded by ESA to date in which astro-garbage has been created by so-called fragmentations, i.e., due to collisions and explosions.
Circa 10,600 metric tons (11,760 short tons)
That is how much the garbage is assumed to weigh in total, according to ESA.
The most effective way to slow the growth rate of space debris is to ensure at least 90 % of new objects we launch are removed from busy orbital highways at the end of their mission.
Source: 2022 Environment Report of ESA’s Space Debris Office
These are the space cleaners
In 2021, ESA inaugurated its new Space Safety Center. Besides monitoring cosmic weather and investigating solar storms, the center is mainly focused on fighting the problem of space debris. “We demand that from 2030 the object must disappear at the end of every mission,” says Holger Krag, Head of the Space Safety Program at ESA. The implementation of such end-to-end space cleaning requires a competitive landscape of several providers in order to develop price-reducing routines and scaling effects.
Together with Swiss startup Clearspace, ESA intends to launch a robot into orbit that removes pieces of debris and defective satellites with its gripper arms. A kind of cosmic garbage removal service that hugs the debris using a space probe and then hauls it toward the Earth where it ablates in the atmosphere. That is no joke because the first satellites already have a “throw-away handle” installed on their outer shell to facilitate their disposal.
Another ESA idea is an aluminum-plated braking sail (“Drag Augmentation Deorbiting System”) that is supposed to gently push satellite carriers from their orbits in the direction of the Earth’s atmosphere where they burn up. Currently, the model has been developed for “deorbiting” small satellites in a range of up to 100 kilograms (220 pounds). However, the same project is also conceivable for medium-sized to large satellites, according to ESA.
The German Aerospace Center (DLR) is working on space debris disposal technologies as well. One of the ideas being pursed is to decelerate pieces of debris using a high-performance laser until they drop into the Earth’s atmosphere where they burn up. However, such powerful lasers would need their own powerplants. Another DLR approach is not to have defective satellites crash to Earth right away but to try to repair them first. For this “on-orbit servicing” a safe approach to the defective satellite using a flying service unit including a robotic arm must be achieved. That’s not an easy objective but initial tests with partners on the ISS have already been run.
To collect garbage or otherwise dispose of it, the garbage must first be localized. This is the approach pursued by German startup Vyoma. The company intends to gather real-time data with its own satellites to localize astro-garbage. Plus, the data helps predict and thus prevent potential collisions. However, at speeds of several tens of thousands of kilometers per hour, that poses a major challenge. The first of the two Vyoma satellites is planned to be launched in 2024. Commercial and institutional customers are said to exist already. “That will be sufficient for developing a catalog of objects that are larger than 20 centimeters,” according to Vyoma. Subsequently ten other monitoring satellites are planned to follow. All of them are supposed to be ablated in the atmosphere without any residues at the end of their mission.
Startup Okapi Orbits is gathering data as well – not for disposing of astro-garbage but for preventing accidents. The data is migrated into collision avoidance software for satellites. An artificial intelligence analyzes the information and in case of an emergency recommends a potential evasive maneuver to customers.
Manuel Metz from DLR views the many different approaches in a positive light. “My impression is that industry is seeing a prospective market here. There are various approaches in several countries that are being tested.” Exactly that is the right course of action, says the expert. In view of the complexity of the task, it’s only logical that there must be more than one appropriate solution. Maybe an unbiased approach to technology will also be the key to success in resolving this extra-earthly problem.
Technology from Schaeffler on board of the lunar mission
With Schaeffler Aerospace GmbH, the Schaeffler Group has been an important partner for aerospace companies for more than half a century. A few weeks ago, the “Artemis 1” lunar mission of Schaeffler’s partner NASA was successfully launched. Also on board was technology from Germany’s Lower Franconia region. Engineers from Schaeffler Aerospace in Schweinfurt developed ball bearings for high-speed engine pumps and delivered them to the United States. All of it top secret!
The engines are supplied by Aerojet Rocketdyne. “With more than twelve million horsepower, the Aerojet Rocketdyne RS-25 is the most powerful propulsion unit existing on our planet,” says Armin Necker, Managing Director of Schaeffler Aerospace. The rocket is equipped with four RS-25 engines. Each has a weight of more than three metric tons (3.3 short tons) and a diameter of around two and a half meters (eight feet). The turbo pumps in which high-precision bearings from Schaeffler Aerospace are installed perform a particularly important job of pumping the fuel at a pressure of around 450 bar and the oxidator oxidation at around 300 bar into the combustion chamber. The high-pressure pumps achieve speeds of around 35,000 and 24,000 revolutions per minute without being lubricated by oil or grease because liquid hydrogen and oxygen are colder than –200 degrees centigrade (–328 degrees Fahrenheit). The bearings are lubricated only by the rocket fuel, i.e., liquid oxygen and hydrogen, cooled down to –200 degrees centigrade. For the rolling bearings, Schaeffler developed the extremely robust and corrosion-resistant material Cronidur 30 that is also being used in many other applications.