Since the dawn of space exploration, more than 9,000 satellites have been launched into orbit. As the number of launches continues to rise rapidly, space is becoming increasingly crowded. Alongside the satellites, there are about 100,000 tonnes of debris orbiting Earth, most of which is too small to track. But how much harm can these tiny fragments cause to spacecraft? And how do we protect the International Space Station (ISS) from such threats? Let’s delve into the physics of space impacts and the strategies used to safeguard the ISS, including how these methods are tested on Earth.
Among the myriad objects orbiting Earth, only those larger than a baseball can be tracked. If a spacecraft is on a collision path with a detectable piece of debris, it can maneuver to avoid a crash. However, millions of smaller objects remain untracked, posing a significant risk. For instance, a raindrop weighing 0.2 grams falls with about 0.8 millijoules of energy, but if it were space debris, it would carry over a million times more energy due to its much higher speed. This is explained by the kinetic energy formula, where energy is proportional to mass and the square of velocity.
In the vacuum of space, these small impacts are unavoidable. Even minuscule items like paint flecks have caused noticeable damage to the Space Shuttle’s windows. Micrometeoroids, which originate from beyond Earth’s orbit, can travel at speeds of around 20 kilometers per second. Given the ISS’s size, comparable to a football field, it is constantly at risk from debris. Astronaut Chris Hadfield once photographed a solar array with a bullet-sized hole.
To protect a structure as large as the ISS, engineers employ a “whipple shield” instead of heavy, thick plating. This shield consists of a thin outer wall, a small gap, and a thicker inner wall. The outer wall shatters the projectile into smaller pieces, distributing the kinetic energy across multiple impacts on the inner wall. In some sections, the space between the walls is filled with high-impact materials like Kevlar or aluminum oxide. The ISS uses over a hundred different shield configurations to balance weight and protection effectively.
Fortunately, extensive testing of these impacts can be conducted on Earth. Since typical firearms cannot achieve orbital velocities, scientists developed the Light-Gas Gun in the 1960s. This device uses an explosive charge to move a piston, compressing a sealed gas chamber. A thin bursting disk at the chamber’s end bursts at a specific pressure, allowing the gas to expand rapidly and accelerate the projectile to orbital speeds.
In one experiment, a 7-gram polycarbonate projectile hit an aluminum block at 7 km/s, creating a crater five times wider and deeper than its diameter. Understanding orbital impacts involves examining the process in stages. As the projectile hits, it decelerates rapidly, compressing itself and the target. The pressure raises the temperature enough to melt the impact area and vaporize the projectile, sending a shock wave through the object that can tear apart the material. All of this happens in a fraction of a second, meaning astronauts on the ISS would never see it coming.
Researchers are currently exploring new solutions to enhance ISS protection. While current whipple shields use Kevlar or aluminum oxide, there is potential to replace these with materials that perform Rapid Puncture-Initiated Healing. This involves using a liquid filling in the whipple shield. As debris passes through at high speed, the heat and friction cause the liquid to flow into the hole and seal it as it hardens. One test demonstrated that the liquid could react with oxygen to seal a hole in less than a second.
As we venture beyond our trackable space debris, shields like these will need continuous improvement. Lighter, more easily repairable shields will be essential for long journeys to Mars and beyond. Regardless, we can be grateful for the protective atmosphere we have here on Earth. Thank you for engaging with this topic, and I look forward to sharing more insights in the future!
Engage in a simulation exercise where you track space debris using software tools. Analyze the trajectory of various debris sizes and predict potential collision courses with satellites. Discuss the limitations of current tracking technologies and propose improvements.
Participate in a workshop to calculate the kinetic energy of different space debris sizes and velocities. Use the kinetic energy formula to understand the impact potential of these objects. Discuss how these calculations influence the design of protective measures for spacecraft.
Design your own Whipple shield using available materials. Test its effectiveness by simulating debris impacts with small projectiles. Compare your design with the ISS’s current shield configurations and discuss potential improvements.
Analyze data from a Light-Gas Gun experiment. Examine the impact craters formed on different materials and discuss the implications for spacecraft shielding. Explore how these experiments help in understanding and mitigating space debris impacts.
Research and present on new materials being developed for space shielding, such as Rapid Puncture-Initiated Healing materials. Discuss their potential applications and benefits for future space missions, especially for long-duration journeys beyond Earth’s orbit.
Since the beginning of spaceflight, over 9,000 satellites have been launched into orbit. With the rate of launches increasing exponentially, space is about to get much busier. In addition to every satellite currently in Earth’s orbit, there is around 100,000 tonnes of debris, most of which is too small for us to track. But how much damage can a tiny object really do to a spacecraft? And how do we shield the ISS from such dangers? In this video, we’ll explore the physics behind space impacts and the various methods used to protect the ISS, including how we test these methods here on Earth.
Out of all the objects orbiting Earth, only those larger than a baseball can be tracked. If a spacecraft is on a collision course with a piece of debris, it can perform a maneuver to avoid destruction. However, for the millions of tiny objects that can’t be tracked, a collision could still be catastrophic. For example, a raindrop weighing 0.2 grams falls with about 0.8 millijoules of energy, but the same raindrop as space debris would have over a million times more energy, despite its speed being only 1,000 times faster. This is due to the formula for kinetic energy, where mass is directly proportional and velocity is squared.
When operating in the vacuum of space, these tiny impacts are unavoidable. Even small items like flecks of paint have caused visible damage to the Space Shuttle’s windows. Micrometeoroids from outside Earth’s orbit can travel at even greater speeds, around 20 kilometers per second. Given that the ISS is the size of a football field, it is constantly exposed to debris. Astronaut Chris Hadfield captured a photo of one of the solar arrays with a bullet-sized hole in it.
To shield something as large as the ISS, rather than using heavy thick plating, engineers use a “whipple shield.” This consists of a thin outer wall, a small gap, and a thick inner wall. The outer wall doesn’t significantly reduce the speed of the impact but shatters the projectile into finer pieces, spreading the kinetic energy across many smaller impacts on the inner wall. In some areas, the space between the two walls is filled with high-impact materials like Kevlar or aluminum oxide. The ISS features over a hundred different shield configurations to balance weight and protection.
Fortunately, extensive testing of these impacts can be conducted on Earth. Since typical firearms cannot generate orbital velocities, scientists invented the Light-Gas Gun in the 1960s. This device uses an explosive charge to move a piston and compress a sealed chamber of gas. The end of the chamber has a thin bursting disk that bursts at a specific pressure, allowing the rapid expansion of gas to accelerate the projectile to orbital velocities.
In one experiment, a 7-gram polycarbonate projectile collided with an aluminum block at 7 km/s, creating a crater five times wider and deeper than its own diameter. Understanding orbital impacts involves examining the process in stages. As the projectile collides, it decelerates rapidly, compressing both itself and the object. The pressure increases the temperature enough to melt the impact area and vaporize the projectile, sending a shock wave through the object strong enough to tear apart the material. All of this occurs in a fraction of a second, meaning astronauts onboard the ISS would never see it coming.
Currently, researchers are exploring new solutions that could provide even greater protection for the ISS. While existing whipple shields use Kevlar or aluminum oxide, there is potential to replace these materials with one that performs Rapid Puncture-Initiated Healing. This involves using a liquid filling in the whipple shield. As debris passes through at high velocity, the heat and friction stimulate the liquid to flow into the hole and seal it as it hardens. One test showed that the liquid could react with oxygen to seal a hole in less than a second.
Shields like these will need to be continuously improved as we send humans beyond our trackable space debris. Lighter shields that are easier to repair will also be crucial for long journeys to Mars and beyond. Regardless, we can be thankful for the atmosphere we have here on Earth. Thank you for watching, and I’ll see you in the next video!
Space – The vast, seemingly infinite expanse that exists beyond the Earth’s atmosphere, where celestial bodies and cosmic phenomena occur. – The study of space involves understanding the gravitational forces that govern the motion of planets and stars.
Debris – Fragments of material, often from spacecraft or satellites, that orbit in space and pose potential hazards to other objects. – Engineers are developing new technologies to track and remove space debris to prevent collisions with operational satellites.
Energy – The capacity to do work or produce change, often measured in joules or electron volts in the context of physics. – Solar panels on spacecraft convert sunlight into electrical energy to power onboard systems.
Impacts – Collisions between objects, which can result in the transfer of energy and momentum, often studied in the context of celestial bodies and spacecraft. – The impacts of micrometeoroids on spacecraft surfaces can cause significant damage over time.
Shielding – Materials or structures designed to protect against harmful radiation or impacts from debris in space environments. – Engineers must design effective shielding to protect astronauts from cosmic radiation during long-duration missions.
Protection – Measures or systems implemented to safeguard against potential hazards, such as radiation or physical impacts, in engineering and space exploration. – Thermal protection systems are crucial for ensuring the safe re-entry of spacecraft into Earth’s atmosphere.
Velocity – The speed of an object in a particular direction, a vector quantity crucial in determining the motion of objects in physics. – Calculating the velocity of a satellite is essential for maintaining its orbit around Earth.
Materials – Substances or components used in the construction and design of engineering projects, often selected for their specific properties. – Advanced composite materials are used in spacecraft construction to reduce weight while maintaining strength.
Astronauts – Trained individuals who travel and work in space, conducting experiments and operating spacecraft systems. – Astronauts aboard the International Space Station conduct experiments to study the effects of microgravity on biological systems.
Experiments – Scientific procedures undertaken to test hypotheses, often conducted in controlled environments such as laboratories or space stations. – Experiments in zero gravity provide unique insights into fluid dynamics that cannot be observed on Earth.
