Space tethers are shaking up the way we think about spacecraft operations. These long cables connect satellites or spacecraft, opening up new mission possibilities.
They use orbital mechanics and electromagnetic forces to generate power, swap momentum, and even propel spacecraft—all without burning fuel.
Space tethers rely on some pretty basic physics, but they’re surprisingly well-suited for orbit. Gravity gradient forces naturally pull tethered systems into a vertical alignment once they’re deployed.
The lower satellite feels a stronger gravitational tug, which helps stabilize the whole setup.
Electrodynamic tethers work by moving through Earth’s magnetic field. Thanks to Faraday’s law, a conducting wire cutting across magnetic field lines produces voltage along its length.
Momentum exchange lets tethered satellites transfer angular momentum between themselves. One can climb to a higher orbit while the other drops lower, all while keeping the system’s total momentum constant.
A typical tether system has three main parts: the base satellite, the tether itself, and a subsatellite. The base satellite handles deployment.
The tether keeps everything connected and, depending on the mission, might be conductive or not.
American researchers started looking into space tethers in the 1960s, mostly as a theoretical exercise. Things got real with Gemini 11 in 1966, when astronauts actually deployed a 30-meter tether to create artificial gravity by spinning.
NASA joined forces with the Italian Space Agency in the 1970s for the Tethered Satellite System (TSS). Mario Grossi and Giuseppe Colombo pitched the idea.
The TSS-1 mission hitched a ride on Space Shuttle Atlantis in 1992. Technical hiccups meant the tether only reached 256 meters, not the planned 20 kilometers.
Even so, the mission showed that gravity gradient stabilization really worked.
TSS-1R followed in 1996 on Space Shuttle Columbia. This time, the tether made it to 19.7 kilometers before an electrical discharge snapped it.
Despite the break, scientists gathered tons of data on electromagnetic effects and current generation.
The US Naval Research Lab launched the TiPS experiment in 1996 using a 4-kilometer non-conductive tether. That system lasted ten years in orbit and gave us valuable survivability data.
Electrodynamic tethers use conductive cables to tap into planetary magnetic fields. They can generate electrical power or create thrust for maneuvering satellites.
The conducting wire acts as both a generator and a motor, depending on which way the current flows.
Momentum exchange tethers move orbital energy between connected spacecraft. The upper satellite gets a boost, while the lower one drops.
This is the heart of tether propulsion, letting payloads shift between orbits.
Tether satellites help researchers study plasma, atmospheric conditions, and space debris. Two connected satellites make a great distributed measurement platform.
Yo-yo despin systems are probably the most common use for tethers. These short cables, with weights on the end, slow down spinning satellites after they separate from rocket motors.
NASA’s Dawn mission used 12-meter versions to kill unwanted rotation.
Formation flying tethers keep multiple spacecraft at just the right distance from each other. The cable connects them, but each satellite can still do its own thing.
This setup is great for big scientific observations.
Space author Michel van Pelt has written a lot about these concepts, spotlighting their potential for future missions and even commercial use.
American researchers usually focus on two main tether types: conducting systems for propulsion by interacting with magnetic fields, and non-conducting versions for mechanical jobs.
Lately, tape tether designs and hollow cathode systems have made deployments more reliable and improved current collection.
Conducting tethers generate electrical current as they move through Earth’s magnetic field. This creates drag or thrust without burning fuel.
The U.S. Naval Research Laboratory’s TEPCE mission showed this in action, using two connected CubeSats and a 1-kilometer conducting tether.
Current flows through the wire and pushes against the magnetic field, creating tether electrodynamic propulsion. That’s how satellites can change orbits or speed up their descent.
Non-conducting tethers, on the other hand, work with mechanical forces. They use materials like aramid fiber for strength and flexibility.
These tethers connect spacecraft for momentum transfer or spin them to create artificial gravity.
Most U.S. projects lean toward conducting tethers, since they offer more options for satellite operations and cleaning up low-Earth orbit debris.
Tape tether designs have become the go-to in American programs. Tethers Unlimited came up with the Terminator Tape, which deploys from small modules.
Georgia Tech’s Prox-1 satellite used this tech to deorbit 24 times faster than normal.
The flat tape shape gives more surface area than round wires, so it interacts better with charged particles. Tapes also tangle less during deployment—a nice bonus.
Universities are always testing new ways to deploy tethers. The University of Michigan’s MiTEE-1 uses a rigid boom instead of a flexible line, which helps them study electron collection with fewer deployment headaches.
Control systems keep tethers from oscillating and hold their orientation steady. Ground stations keep an eye on things and tweak operations if needed.
Hollow cathode devices spit out electrons to finish electrical circuits in space. American researchers have been working to make these lighter and less power-hungry.
The European E.T.PACK project tested cathodes at low mass flow rates, teaming up with U.S. partners.
Old-school cathodes need heavy gas tanks and lots of power. Newer designs use different materials and methods to get around that.
Low-work-function materials make it easier to release electrons.
University labs run cathode tests in vacuum chambers to mimic space before sending them up. NASA’s Educational Launch program helps students try out tiny cathode systems.
Reliable cathodes really matter for long-term tether missions. They need to last months or even years without any fixes.
American companies are pushing to make cathodes that work with little ground intervention.
Electrodynamic tethers create propulsion by running electric current through long wires in Earth’s magnetic field. This generates thrust without fuel—pretty wild, right?
Spacecraft can change orbits and even generate power using these electromagnetic tricks.
Electrodynamic tethers use electromagnetic induction for propellantless propulsion. When a conductive wire moves through the planet’s magnetic field, it creates an electromotive force that drives current.
A typical setup has a long conductive tether and end masses at each end. As the spacecraft orbits, the tether cuts through magnetic field lines at about 7.5 kilometers per second.
This movement triggers a Lorentz force between the field and the electrons in the tether. Depending on which way the current flows, the force can push the spacecraft faster or slow it down.
Some big advantages:
Tether lengths can be anywhere from a few hundred meters to several kilometers. Longer tethers make more force but are tougher to deploy.
Collecting current is probably the trickiest part of running electrodynamic tethers. The system has to pull in electrons from the surrounding plasma to complete the circuit.
Spacecraft use special contact devices at the tether ends for this. These collectors grab electrons from the ionospheric plasma, which is full of free electrons at altitudes between 200 and 2,000 kilometers.
How well the system collects current depends on a few things:
Bare tether designs skip the usual end collectors and just use the tether itself to collect electrons. That makes things simpler and still gets the job done.
Current density can change a lot depending on where you are in orbit and how active the sun is. The best collection happens during high ionospheric density, usually on the daylight side of Earth.
The Tether Electrodynamic Propulsion CubeSat Experiment (TEPCE) brought electrodynamic propulsion to small spacecraft. The Naval Research Laboratory ran this mission to show off key tech for future commercial missions.
TEPCE used a three-unit CubeSat configuration with a kilometer-long tether connecting two end masses. The system generated thrust through electromagnetic effects and kept its orbit pretty stable.
Commercial CubeSat missions can really benefit from tethers:
CubeSat tether systems still struggle with deployment because of their size. Engineers keep working on smaller deployment mechanisms to fit the tight CubeSat form factor.
The tech seems especially useful for satellite constellation management, where lots of spacecraft need frequent orbit changes. Electrodynamic tethers offer sustainable propulsion without the headaches of refueling.
Tethers Unlimited Inc. leads the pack in American space tether development, pushing manufacturing innovation and orbital systems forward.
The University of Michigan has pulled off some impressive tether missions, like MITEE-1. U.S. military and NASA programs keep advancing tether tech for national security and commercial space, too.
Tethers Unlimited Inc. is pretty much the top U.S. space tether company. Robert P. Hoyt and Robert L. Forward started it back in 1994, and it’s been shaping the field ever since.
The company operates out of Bothell, Washington, with about 50 employees focused on space, sea, and air tech. TUI’s specialties include space tethers, orbital robotic assembly, and fabrication technologies.
Some highlights: the Multi-Application Survivable Tether (MAST) experiment, launched in 2007 with Stanford, tested how tethers hold up in space.
TUI also sent the Refabricator to the International Space Station in 2018. It turns plastic waste into 3D printer filament—super handy for on-orbit manufacturing.
Their Spiderfab technology is a big leap forward, letting spacecraft build structures much larger than themselves while in orbit. Think antennas, solar panels, and trusses.
Amergint Technologies bought TUI in May 2020, and now both are subsidiaries under Arka, which broadens their reach.
The University of Michigan has made a real mark on American tether research, running several missions out of its aerospace engineering department.
MITEE-1 (Miniaturized Tether Electrodynamics Experiment) is one of their big efforts, testing how conducting tethers interact with Earth’s magnetic field to create thrust.
Their researchers focus on electrodynamic propulsion with space tethers—basically, making thrust without using fuel.
Faculty and students work together on deployment mechanisms and control systems. They’re tackling tough problems like tether stability and orbital dynamics.
Michigan teams up with NASA and private companies to keep pushing tether technology. These partnerships connect academic research with real-world space missions.
The university’s work includes building theoretical models for tether behavior and proving them out with small satellite missions.
NASA really gets behind space tether development with a bunch of programs and partnerships. The agency funds projects and opens up testing opportunities for new tether tech.
The U.S. Naval Research Laboratory built the TiPS tether satellite system—a 4-kilometer tether that actually showed off some military uses for space-based ops.
NASA’s Tipping Point initiative put money into Tethers Unlimited’s Dragonfly program, teaming up with SSL. This program pushes in-space manufacturing using systems that deploy by tether.
The Space Force handles national security contracts where tethers come into play. They’re mostly focused on military satellites and space-based defense tech.
Government funding often lands in the hands of small businesses working on tether innovations. NASA gave out $750,000 grants to companies like Tethers Unlimited to help move space technology forward.
Military folks use tethers for satellite constellation management and debris removal. These systems keep costs down for maintaining stuff in orbit.
Federal agencies work together on tether research through the National Space Council. That kind of coordination helps the U.S. stay ahead in sustainable space technologies.
The United States has really led the way in space tether research, running three big experimental programs. These missions dug into electrodynamic power generation, long-term tether survivability in orbit, and deployment mechanisms for future commercial applications.
NASA’s Small Expendable Deployer System (SEDS) program ran three important tether missions between 1993 and 1994. These marked the first time anyone pulled off long-distance tether deployments in space.
SEDS-1 made history in 1993 with the first fully successful orbital tether test. It released a 20-kilometer tether from a spent Delta-II second stage, swung vertical, and then cut loose after one orbit, sending the payload on a reentry path from Guam to Mexico’s coast.
SEDS-2 took off in March 1994 with another 20-kilometer tether. This time, feedback braking kept the swing to just 4 degrees after deployment. The payload sent back data for 8 hours before the battery died, and the tether’s torque spun the system up to 4 rpm.
The Plasma Motor Generator (PMG) experiment used a 500-meter copper wire tether to show off electrodynamic operation. Launched in June 1993, the seven-hour mission proved the current could actually reverse direction, so you could generate power or boost orbits. The hollow cathode assembly managed to link electrical current between the spacecraft and the ionosphere.
The U.S. Naval Research Laboratory sent up TiPS in 1996 to see how long a tether could last in space. This mission stretched out a 4,000-meter tether between two satellites called “Ralph” and “Norton.”
TiPS gave engineers crucial data on survivability for future missions. The system stayed intact for nearly 10 years before breaking in July 2006. That long run proved debris impact models were on point and showed tethers could last way longer than some ground-based tests guessed.
Amateur astronomers sometimes caught sight of TiPS during its decade in orbit. With binoculars or a small telescope, you could spot the satellite pair when the lighting was just right. This glimpse showed that bigger tethers might be visible from the ground, too.
The mission’s long life really challenged those pessimistic ground test predictions. TiPS data made it clear that two-year survival estimates were way too cautious, which gave planners more confidence for longer missions.
NASA teamed up with the Italian Space Agency for two bold Space Shuttle tether missions. These experiments checked out gravity gradient stabilization and plasma electrodynamics using a spherical satellite launched from the shuttle bay.
TSS-1 Mission (1992)
TSS-1 ran into mechanical trouble and couldn’t fully extend the tether. Even with the short deployment, the mission still proved gravity-gradient stabilization worked in space. Scientists picked up some useful data on how deployment dynamics and safety procedures played out.
TSS-1R Mission (1996)
TSS-1R managed a much longer deployment before the tether snapped. The mission measured motional EMF, satellite potential, and tether current. Scientists found current levels three times higher than models predicted, which led to better theories about how tethers and plasma interact.
Both missions pushed electrodynamic tether science forward, despite the hiccups. The experiments proved that when you drag a conducting tether through Earth’s magnetic field, you can generate a lot of electrical current.
Space tethers are actually pretty practical for getting rid of defunct satellites and stopping new debris from piling up. They use electrodynamic drag systems and automated deorbiting tech to tackle the growing threat to commercial spaceflight and satellite constellations.
Electrodynamic tethers let spacecraft dispose of themselves, no fuel needed. The E.T.PACK Initiative got $2.4 million in European funding to create a flight-ready deorbit system with a 500-meter aluminum tape tether.
This system makes electromagnetic drag by interacting with Earth’s magnetic field. The tether generates a current, which creates a braking force and gradually drops the satellite’s orbit until it burns up in the atmosphere.
Terminator Tape works in a similar way. It deploys long conductive strips to speed up orbital decay. These devices kick in automatically at the end of a mission, making sure satellites deorbit within 25 years, just like space agencies require.
Tethers Unlimited built the Terminator Tether for autonomous spacecraft disposal. It doesn’t need any propellant and runs without ground control, making it a good pick for preventing space debris.
Chinese researchers have tried out tethered cubesats that stay connected to the upper stage of the launch vehicle. That way, both the satellite and rocket stage burn up together on reentry, wiping out multiple debris sources at once.
Space tethers help support the Space Sustainability Rating system launched by ESA and MIT in 2022. Companies like OneWeb and Telesat use tethers in their mega-constellation designs to get higher sustainability scores.
Active debris removal missions use tether-and-net capture mechanisms to grab dead satellites. University of Buffalo researchers showed that tether-based capture systems can work reliably when you add machine learning optimization.
These systems figure out the mass and spin of uncooperative debris after capture. Tethers then steer the captured object into a controlled reentry path, stopping breakups that would create even more fragments.
Momentum-exchange tethers can move cleanup missions around without fuel. University of Strathclyde researchers showed these spinning tethers still work, even when they’re hauling off-balance debris loads.
The US Naval Research Laboratory is testing electrodynamic tethers designed to clear out existing space debris that threatens commercial satellites and even space tourism flights.
Engineers have started designing more advanced systems that use spinning cables to swap momentum between spacecraft or create artificial environments. These new ideas turn simple tethers into powerful tools for orbital mechanics and crew comfort.
Momentum exchange tethers act like giant slingshots in orbit, letting spacecraft boost or drop without burning fuel. You connect two objects with a cable, spin them up, and build rotational energy.
When a spacecraft comes up to the lower end of a rotating tether, it can latch on and ride the cable upward. The tether hands off some of its momentum, launching the craft to a higher orbit, while the tether system slows down a bit.
Key benefits:
The best designs use tethers that stretch for kilometers. A 100-kilometer tether spinning once per orbit could toss payloads from low Earth orbit to geostationary transfer orbit. Some say this could cut satellite launch costs by as much as 80%.
NASA’s studies suggest these tethers work best between 400 and 800 kilometers up. That’s where drag is low but the magnetic field is still strong enough for efficient operation.
Rotating tether systems can create artificial gravity by spinning spacecraft around a central point. The spin pushes crew outward against the walls, kind of like gravity on Earth.
Space stations linked by tethers can spin around their shared center of mass. Astronauts inside feel artificial gravity that helps fight bone loss and muscle problems during long trips. The farther you are from the center, the stronger the gravity feels.
Requirements:
If you connect two spacecraft with a 200-meter tether, just 2.1 rotations per minute gives you Mars-level gravity (0.38g). That’s slow enough to avoid most inner ear issues.
The International Space Station could try this for crew rest periods. Deploying a tether system would let astronauts get a few hours of artificial gravity daily, without rebuilding the whole station.
Centrifugal force from spinning tethers opens up some wild possibilities you can’t get with regular spacecraft. Manufacturing benefits from controlled artificial gravity that separates materials by density or helps grow better crystals.
Space-based solar power stations use spinning tethers to keep giant arrays pointed at the Sun. The spin keeps the structure tight without heavy support beams.
Industrial uses:
Labs attached to tethers can switch gravity levels during experiments. Scientists just tweak the spin rate to simulate Mars, the Moon, or whatever they want, all while staying in Earth orbit.
Tethered debris collectors use centrifugal force to bundle up space junk. The spin sorts debris by size and density, making recycling easier. These systems could clean up orbit and supply raw materials for building stuff in space.
New tether designs and high-performance materials have turned space tethers from just experiments into reliable tools for orbit. Engineers now focus on damage resistance and structural integrity in harsh space environments.
The Hoytether marks a real leap in tether survivability thanks to its clever net-like structure. Instead of relying on a single thick cable, engineers weave a web of thin wires, connecting them at regular intervals.
If a micrometeorite or space junk smacks into a traditional tether, the whole thing usually fails. But with a Hoytether, those redundant pathways keep the system running, even after several impacts. Each little wire only carries a bit of the total load, which is kind of brilliant.
Key Features:
This interconnected setup spreads out both electrical current and mechanical loads. As a result, space missions relying on tethers have a much better shot at lasting through long operations.
NASA has put the Hoytether to the test on several missions in low Earth orbit. It seems especially promising for electrodynamic tethers—where current has to keep flowing, even if something gets dinged by debris.
Aramid fiber forms the backbone of many real-world space tether systems. This synthetic polymer stands out for its high strength-to-weight ratio and ability to shrug off space radiation.
Kevlar is the most familiar aramid fiber here. It boasts tensile strength over 3.6 GPa, and space-grade aramid keeps its properties from -150°C up to +150°C.
Modern tape tether designs use flat ribbons woven from aramid fibers. Flat tape gives more surface area for electrodynamic effects and stays flexible during deployment.
Aramid fibers do a better job resisting atomic oxygen erosion than many other options. That’s pretty important in low Earth orbit, where atomic oxygen slowly chews up exposed materials.
Lately, engineers have started wrapping aramid cores with protective outer layers. These composites help shield the fibers from UV radiation and particle impacts while keeping the aramid’s strength intact.
Space elevators could totally change how we reach orbit. Instead of rockets, they use a cable stretching from Earth’s surface all the way through geostationary orbit. The cost per kilogram could drop from $10,000–$25,000 down to just $100–$400.
A space elevator cable anchors to the ground and stretches about 62,000 miles up. Earth’s rotation keeps it taut, with one end on the ground and the other past geostationary orbit—about 22,236 miles high.
These systems need ultra-strong materials to work. Carbon nanotubes look like the top candidate right now, thanks to their incredible strength-to-weight ratio. The cable has to handle huge stresses but still be light enough to build.
The main parts of a space elevator include a ground anchor, climbing vehicles (like elevators), the ultra-strong cable, and a counterweight past geostationary orbit. Climbers move up and down, carrying stuff and people to different altitudes.
At geostationary orbit, spacecraft can dock and launch to other places without burning tons of fuel. No need to reach 17,500 mph with rockets just to get to orbit.
Material requirements are tough: the cable needs tensile strength over 130 gigapascals, with low density, for a length of 100,000 kilometers. Steel and Kevlar just don’t cut it, so carbon nanotubes are really the only hope right now.
Space elevators could become permanent infrastructure, supporting all sorts of space activities at once. They’d act like highways in orbit, letting cargo and passengers move continuously, not just when rockets are ready.
This setup could support space manufacturing facilities in orbit, where microgravity and vacuum make it possible to produce stuff you just can’t on Earth. Think advanced metallurgy or perfect crystal growth.
Commercial space tourism might finally make sense if getting to orbit gets 99% cheaper. We could see space hotels and research labs operating profitably with reliable, affordable access.
Asteroid mining becomes practical too, since cargo transport no longer costs a fortune. Resources from asteroids could help build lunar bases or prep Mars missions, without launching everything from Earth.
As space business grows, more elevators could handle the traffic. With climbers running in controlled conditions, weather delays matter less than they do for rockets.
The gentle acceleration also helps. It’s way better for sensitive cargo and passengers who can’t handle rocket g-forces. That opens up space travel for more people and lets us send delicate scientific gear safely.
Small satellites—especially CubeSats—have become the go-to for testing electrodynamic tethers. 3U CubeSats demonstrate deployment, and the MiTEE-1 mission explores miniaturized tether operations. These little platforms let researchers test out concepts cheaply and work toward bigger, scalable solutions.
The 3U CubeSat, at 10 cm × 10 cm × 34 cm, has become the standard for tether demos. It’s just big enough for deployment hardware and electronics.
TEPCE Mission Performance The Tether Electrodynamic Propulsion CubeSat Experiment split into two 1.5-unit CubeSats, linked by a 1-kilometer conducting tether. Running current through the system produced drag thrust by pushing against Earth’s magnetic field.
Terminator Tape Success Tethers Unlimited’s Terminator Tape worked on the 71-kg Prox-1 CubeSat. After it deployed in September 2019, the satellite deorbited 24 times faster than models predicted without the tether.
Some missions use bare electrodynamic tethers from 100 to 500 meters long. The DESCENT mission, for example, deploys a 100-meter bare tether between two 1U CubeSats to test deorbiting.
MiTEE-1 is part of NASA’s Educational Launch of Nanosatellites, focusing on miniaturized tether research. The University of Michigan built this 3U CubeSat to study electrodynamics for satellites as small as 200 grams.
Instead of a flexible tether, MiTEE-1 deploys a rigid 1-meter boom. This makes it easier to measure electron current collection with a 200-volt variable-bias power supply.
Key Technical Components:
MiTEE-1 looks at how spacecraft charge up in Earth’s ionosphere. The data helps design future mini-tether systems for propellantless propulsion on tiny satellites.
The team aims to develop 10–30 meter electrodynamic tethers for picosatellites and femtosatellites under 1 kilogram.
Space tethers interact with charged particles to create new propulsion systems. Electric sails use plasma interactions to get thrust from solar wind—no propellant needed.
Moving tethers through plasma generates electric fields that stretch out far beyond the wire itself. This is the foundation for some pretty advanced propulsion ideas.
Electrodynamic tethers cut through Earth’s magnetic field lines as they move. That motion creates electrical current via electromagnetic induction. The current flows through the tether and completes its circuit in the surrounding plasma.
Plasma conditions change a lot depending on altitude. In low Earth orbit, atomic oxygen erodes tether materials. Higher up, plasma density shifts and affects current and performance.
Key plasma interaction factors:
Researchers have found that real current values often run about 50% higher than theory predicts. That just shows how complex plasma dynamics can get up there.
Electric sails are a wild new way to use plasma-tether tech for deep space. These systems string out multiple thin tethers, charge them to high positive voltages—sometimes several kilovolts—and interact with solar wind particles.
The tethers push away positively charged protons in the solar wind. Each one forms a plasma sheath extending about 10 meters, making the “sail” much bigger than the wire itself (which is less than 0.1 mm wide).
Electric sails keep working well even far from the Sun. They provide thrust at distances six times beyond what regular solar sails can manage. That makes electric sails really interesting for missions to outer planets or even interstellar probes.
Arrays of tethers form the sail. Each wire adds to the total thrust, though a single tether performs a bit better by itself than in a group. Still, the overall effect is what matters.
No propellant needed here, so electric sails are perfect for long missions where you just can’t bring enough fuel.
Space tether technology faces tough problems, especially with material durability and space environment survival. At the same time, regulatory frameworks lag behind the pace of innovation. Still, the potential for deep space exploration is hard to ignore.
Space tethers have to survive some of the harshest conditions out there. Micrometeorite impacts are a constant worry, since fast-moving particles can cut cables or weaken them.
The space environment brings other hazards. Atomic oxygen in low Earth orbit eats away at materials. Temperature swings from -250°F to 250°F make cables expand and contract, stressing every connection.
Electrodynamic tethers deal with even more. Plasma interactions and harsh radiation chip away at materials, making them less conductive and weaker over time.
Key Survival Challenges:
Carbon nanotube tech looks promising for better durability. These materials beat Kevlar in strength-to-weight ratio. NASA keeps testing new composites for long-term space use.
Right now, space regulations don’t really cover tethers specifically, so missions face uncertainty if they want to deploy these systems. The FAA handles launches, but tether rules are still pretty vague.
International coordination gets tricky when tethers cross multiple orbital zones. Agencies have to agree on deployment notifications and how to avoid collisions.
Safety is another concern. If a tether breaks, it turns into more space debris, which could threaten other satellites. Mission planners need solid backup plans for failures.
Regulatory Gaps Include:
The Commercial Space Transportation Advisory Committee has started looking at tether-related policies. New rules will probably require backup systems and real-time monitoring for any tether deployment.
Space tethers bring some unique advantages for missions that go beyond Earth’s orbit, especially where traditional propulsion just can’t keep up due to fuel limits.
Electrodynamic tethers don’t really work in deep space because the magnetic fields out there are too weak. But momentum exchange tethers? They’re still in the game.
Future Mars missions might use tethers to move cargo between orbiting spacecraft and landers on the surface. That could cut down on fuel use and let us deliver bigger payloads to planetary surfaces.
Asteroid mining could be another big win for tethers. They might move materials between mining sites and processing stations—no need for complicated docking procedures.
Deep Space Applications:
NASA’s Artemis program looks at tether systems for lunar operations. These early uses could show if tethers really work in deep space before we get too ambitious with Mars.
Jupiter, with its powerful magnetic field, actually creates new possibilities for electrodynamic tethers. Missions to Europa or Ganymede might use tethers for generating power or nudging orbits.
US agencies have developed space tethers for all sorts of jobs—satellite propulsion, power generation, orbital debris removal, and scientific research.
These systems run into challenges with material strength, but they still offer some sustainable options for space operations using electromagnetic interactions and momentum exchange.
NASA and the US Naval Research Laboratory are pretty focused on tethers for propulsion that doesn’t need chemical fuel. Electrodynamic tethers can generate electric power and also provide thrust or drag for orbital tweaks.
Space agencies have also worked on momentum exchange tethers to move satellites between different orbits without using any propellant. These use gravity gradient forces and controlled releases to shift spacecraft up or down.
Researchers have sent tethered payloads through the upper atmosphere for sampling missions. The TiPS mission, for example, kept a tether working in orbit for over six years.
Scientists use tethered satellites to study plasma and electromagnetic phenomena in Earth’s magnetosphere. These setups let them get measurements from multiple points, which is tough with just one spacecraft.
Electrodynamic tethers interact with Earth’s magnetic field to create forces that push satellites up or down. The direction of the electric current in the tether decides if you get thrust or drag.
When running in power generation mode, tethers turn orbital energy into electricity and create drag, which brings satellites lower. This makes it possible to deorbit spacecraft without burning extra fuel.
If you want to raise a satellite’s orbit, you run the tether in thrust mode, which needs onboard power. The electromagnetic interaction with Earth’s magnetic field then pushes the satellite higher.
Momentum exchange tethers shift energy between connected spacecraft using gravity gradient effects. SEDS missions showed that you can deploy a 20-kilometer tether and keep it stable with feedback control.
US space programs now use high-strength synthetic fibers like Kevlar and Spectra to build tethers. These materials handle the mechanical stresses of orbit without being too heavy.
Researchers see carbon nanotubes as the next big step for tethers. They’re much stronger for their weight, which could let us build even longer tethers or try things like space elevators.
Some tethers use bare wire designs that collect current directly from space plasma. This skips the need for heavy plasma contactors but still keeps the system electrically connected.
Deployment tech has come a long way, too. Early systems used simple friction brakes, but now we have feedback-controlled releases. SEDS-2 proved you can deploy a tether to a stable vertical position if you control the release carefully.
NASA teams up with international partners, like the Italian Space Agency, for big tether missions such as the Tethered Satellite System. By sharing expertise and splitting costs, they get more done.
Universities, like Stanford, push tether research forward through projects like MAST, where they launch CubeSats linked by tethers. This not only drives innovation but also helps train future space engineers.
Military groups, especially the Naval Research Laboratory and Department of Defense, fund and test tether tech. The PMG mission showed off dual-mode operation thanks to this kind of collaboration.
Private companies like Tethers Unlimited Inc. also get involved. Their work brings fresh ideas and helps move new tech from the lab into real space missions.
Deployment failures have caused the most headaches for space tether missions so far. Some missions, like TSS-1 and STEX, couldn’t fully extend their tethers or had to end early because of deployment issues.
Material strength still limits how long tethers can be and how much they can carry. The forces in orbit are intense, and most synthetic fibers just can’t handle it for really big jobs.
Space debris is a big risk for tethers because they’re so long and easy to hit. The TSS-1R tether, which was almost 20 kilometers, got severed before it could fully deploy—proof that long tethers are vulnerable.
As tethers get longer and missions get more complex, the control systems get harder to manage. Keeping everything stable while dealing with electromagnetic forces demands advanced feedback systems, which add weight and cost.
Electrodynamic drag systems offer a way to deorbit dead satellites and space junk without sending up extra spacecraft or making direct contact. These tethers create electromagnetic drag, slowly pulling objects down until they eventually reenter the atmosphere.
Teams working on active debris removal would actually attach tethers to big pieces of debris to speed up their descent. They rely on the electromagnetic drag to clear out dangerous clutter in a more controlled way.
For prevention, engineers now add tethers to new satellites so they can drop out of orbit on their own when their missions wrap up. That means fewer dead satellites hanging around, which sounds like a win for everyone.
Researchers keep exploring how tethers might grab and remove clusters of debris from sensitive orbital zones. If these ideas work, maybe we’ll finally get ahead of the growing space junk problem—and show the world we can keep space sustainable.
