Artist impression of ESA's Gaia satellite observing the Milky Way (Credit : ESA/ATG medialab; Milky Way: ESA/Gaia/DPAC)
For over ten years, the ESA’s Gaia Observatoryhas monitored the proper motion, luminosity, temperature, and composition of over a billion stars throughout our Milky Way galaxy and beyond. This data will be used to construct the largest and most precise 3D map of the cosmos ever made and provide insight into the origins, structure, and evolutionary history of our galaxy. Unfortunately, this sophisticated astrometry telescope is positioned at the Sun-Earth L2 Lagrange Point, far beyond the protection of Earth’s atmosphere and magnetosphere.
As a result, Gaia has experienced two major hazards in recent months that could endanger the mission. These included a micrometeoroid impact in April that disrupted some of Gaia‘s very sensitive sensors. This was followed by a solar storm in May—the strongest in 20 years—that caused electrical problems for the mission. These two incidents could threaten Gaia‘s ability to continue mapping stars, planets, comets, asteroids, quasars, and other objects in the Universe until its planned completion date of 2025.
There are plenty of problems that spacecraft designers have to consider. Getting smacked in the sensitive parts by a rock is just one of them, but it is a very important one. A micrometeoroid hitting the wrong part of the spacecraft could jeopardize an entire mission, and the years of work it took to get to the point where the mission was actually in space in the first place. But even if the engineers who design spacecraft know about this risk, how is it best to avoid them? A new programming library from research at NASA could help.
Still pic from the high-speed video where ESA researchers conduct a hypervelocity test with their new FML shielding. Credit: Fraunhofer Institute for High-Speed Dynamics
After sixty years of space agencies sending rockets, satellites and other missions into orbit, space debris has become something of a growing concern. Not only are there large pieces of junk that could take out a spacecraft in a single hit, but there are also countless tiny pieces of debris traveling at very high speeds. This debris poses a serious threat to the International Space Station (ISS), active satellites and future crewed missions in orbit.
For this reason, the European Space Agency is looking to develop better debris shielding for the ISS and future generations of spacecraft. This project, which is supported through the ESA’s General Support Technology Programme, recently conducted ballistics tests that looked at the efficiency of new fiber metal laminates (FMLs), which may replace aluminum shielding in the coming years.
To break it down, any and all orbital missions – be they satellites or space stations – need to be prepared for the risk of high-speed collisions with tiny objects. This includes the possibility of colliding with human-made space junk, but also includes the risk of micro-meteoroid object damage (MMOD). These are especially threatening during intense seasonal meteoroid streams, such as the Leonids.
While larger pieces of orbital debris – ranging from 5 cm (2 inches) to 1 meter (1.09 yards) in diameter – are regularly monitored by NASA and and the ESA’s Space Debris Office, the smaller pieces are undetectable – which makes them especially threatening. To make matters worse, collisions between bits of debris can cause more to form, a phenomena known as the Kessler Effect.
And since humanity’s presence Near-Earth Orbit (NEO) is only increasing, with thousands of satellites, space habitats and crewed missions planned for the coming decades, growing levels of orbital debris therefore pose an increasing risk. As engineer Andreas Tesch explained:
“Such debris can be very damaging because of their high impact speeds of multiple kilometres per second. Larger pieces of debris can at least be tracked so that large spacecraft such as the International Space Station can move out of the way, but pieces smaller than 1 cm are hard to spot using radar – and smaller satellites have in general fewer opportunities to avoid collision.”
To see how their new shielding would hold up to space debris, a team of ESA researchers recently conducted a test where a 2.8 mm-diameter aluminum bullet was fired at sample of spacecraft shield – the results of which were filmed by a high-speed camera. At this size, and with a speed of 7 km/s, the bullet effectively simulated the impact energy that a small piece of debris would have as if it came into contact with the ISS.
Artist’s impression of all the space junk in Earth orbit. Credit: NASA
As researcher Benoit Bonvoisin explained in a recent ESA press release:
“We used a gas gun at Germany’s Fraunhofer Institute for High-Speed Dynamics to test a novel material being considered for shielding spacecraft against space debris. Our project has been looking into various kinds of ‘fibre metal laminates’ produced for us by GTM Structures, which are several thin metal layers bonded together with composite material.”
As you can see from the video (posted above), the solid aluminum bullet penetrated the shield but then broke apart into a could of fragments and vapor, which are much easier for the next layer of armor to capture or deflect. This is standard practice when dealing with space debris and MMOD, where multiple shields are layered together to adsorb and capture the impact so that it doesn’t penetrate the hull.
An common variant of this is known as the ‘Whipple shield’, which was originally devised to guard against comet dust. This shielding consists of two layers, a bumper and a rear wall, with a mutual distance of 10 to 30 cm (3.93 to 11.8 inches). In this case, the FML, which is produced for the ESA by GTM Structures BV (a Netherlands-based aerospace company), consists of several thin metal layers bonded together with a composite material.
Based on this latest test, the FML appears to be well-suited at preventing damage to the ISS and future space stations. As Benoit indicated, he and his colleagues now need to test this shielding on other types of orbital missions. “The next step would be to perform in-orbit demonstration in a CubeSat, to assess the efficiency of these FMLs in the orbital environment,” he said.
And be sure to enjoy this video from the ESA’s Orbital Debris Office:
The chip in the ISS' Cupola window, photographed by astronaut Tim Peake. Credit: ESA/NASA/Tim Peake
It is known as the Cupola, an observation and work area that was installed aboard the International Space Station in 2010. In addition to giving the crew ample visibility to support the control of the Station’s robotic arms, it is also the best seat in the house when it comes to viewing Earth, celestial objects and visiting vehicles. Little wonder then why sp many breathtaking pictures have been taken from inside it over the years.
So you can imagine how frustrating it must be for the crew when a tiny artificial object (aka. space debris) collides with the Cupola’s windows and causes it to chip. And thanks to astronaut Tim Peake and a recent photo he chose to share with the world, people here on Earth are able to see just how this looks from the receiving end for the first time.
