Futuristic space tether system with asymmetrical payloads in Earth orbit.

Space Elevator 2.0: How Motorized Momentum Exchange Tethers Could Revolutionize Space Travel

Mira Elwood in Tech & Innovation August 2025 • 4 min read.

"Beyond Rockets: Exploring the Potential of Asymmetrical Motorized Tethers for Cost-Effective and Sustainable Space Missions"

For decades, the vision of easily and affordably accessing space has captivated scientists and dreamers alike. Traditional rocket propulsion, while effective, is expensive and environmentally taxing. This has fueled the search for alternative propulsion methods, and one of the most promising is the momentum exchange tether.

Momentum exchange tethers (METs) have emerged as a compelling technology for transporting payloads to and from orbit with reduced costs and environmental impact. The concept involves a tether system, often rotating, that exchanges momentum with payloads, effectively 'slinging' them into different orbits. Motorized versions add another layer of control and efficiency.

This article explores the dynamics of asymmetrical motorized momentum exchange tethers (MMETs) and their potential applications in space travel. It delves into the challenges posed by asymmetrical designs, where mass distribution is uneven, and highlights innovative solutions for maintaining stability and rescuing missions. Also, it looks into cutting-edge applications such as tethered payload release from Low Earth Orbit (LEO) and lunar tether delivery and retrieval, paving the way for future space development.

Understanding Motorized Momentum Exchange Tethers (MMETs)

Futuristic space tether system with asymmetrical payloads in Earth orbit.

A motorized momentum exchange tether (MMET) system typically consists of a central facility with a motor drive shaft connected to propulsion sub-spans via a gantry. This setup allows the tether to rotate, generating an increment of velocity that can be transferred to payloads. For instance, an operational motorized MET in a circular LEO could achieve an orbit velocity of approximately 7.6 km/s, with the tether adding around 3.1 km/s. This combined velocity is sufficient to propel a payload beyond Earth's escape velocity.

A critical component of motorized spin is a counter-inertia system. This system, comprising additional tethers and counter-masses attached to the motor stator, ensures that Newton's third law of motion is satisfied. This counter-inertia system is essential for stabilizing the MMET and enabling controlled momentum transfer.

Cost-Effectiveness: MMETs offer a reusable alternative to traditional rockets, significantly reducing the cost per launch.
Environmental Friendliness: By minimizing the reliance on chemical propellants, MMETs contribute to cleaner space operations.
Versatility: MMETs can be adapted for various missions, including payload transfer between different orbits and lunar surface operations.

However, a significant challenge arises when payload mass distribution is asymmetrical. This asymmetry can occur due to payload loss or failure to retrieve payloads, causing the center of mass to shift and potentially destabilizing the tether. While mass symmetry is ideal, research indicates that mission rescue is possible even under asymmetry conditions, provided appropriate control mechanisms are in place.

The Future of Space Travel with Motorized Tethers

Motorized tethers offer the potential for clean, reusable propulsion in space, accommodating various orbits and mission types. Although the dynamics of space tethers are complex, robust guidance, navigation, and control (GNC) systems, along with compensation propulsion, will be essential in practical scenarios, especially under asymmetrical conditions, to prevent failures. Further research and development in tether technology will pave the way for integrating them into future mission architectures, making space travel more accessible and sustainable.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1051/matecconf/201814801001, Alternate LINK

Title: Motorised Momentum Exchange Space Tethers: The Dynamics Of Asymmetrical Tethers, And Some Recent New Applications

Subject: General Medicine

Journal: MATEC Web of Conferences

Publisher: EDP Sciences

Authors: Matthew Cartmell, Olga Ganilova, Eoin Lennon, Gavin Shuttleworth

Published: 2018-01-01

Everything You Need To Know

How are motorized momentum exchange tethers (MMETs) expected to change the landscape of space travel?

Motorized momentum exchange tethers (MMETs) are poised to revolutionize space travel by providing a reusable and sustainable alternative to conventional rockets. They involve a tether system, often rotating, that exchanges momentum with payloads, essentially 'slinging' them into different orbits. The motorized aspect adds an extra layer of control and efficiency, making them a compelling technology for cost-effective space transport.

What are asymmetrical designs in motorized momentum exchange tethers (MMETs) and what challenges do they pose?

Asymmetrical designs in motorized momentum exchange tethers (MMETs) occur when the mass distribution is uneven, potentially due to payload loss or failure to retrieve payloads. This asymmetry can shift the center of mass, destabilizing the tether. However, research indicates that mission rescue is possible even under asymmetry conditions, provided appropriate control mechanisms are in place, ensuring the tether remains stable and functional.

Can you describe the typical setup and functionality of a motorized momentum exchange tether (MMET) system?

A motorized momentum exchange tether (MMET) system typically consists of a central facility with a motor drive shaft connected to propulsion sub-spans via a gantry. This setup allows the tether to rotate, generating an increment of velocity that can be transferred to payloads. For example, an operational motorized MET in a circular LEO could achieve an orbit velocity of approximately 7.6 km/s, with the tether adding around 3.1 km/s, sufficient to propel a payload beyond Earth's escape velocity.

What role does the counter-inertia system play in the functionality and stability of a motorized momentum exchange tether (MMET)?

The counter-inertia system, comprising additional tethers and counter-masses attached to the motor stator, ensures that Newton's third law of motion is satisfied. This system is essential for stabilizing the motorized momentum exchange tether (MMET) and enabling controlled momentum transfer. Without it, the MMET would become unstable and unable to effectively transfer momentum to payloads.

What are the future implications of motorized tethers, and what key technologies are needed to ensure their successful implementation in space missions?

Motorized tethers offer immense potential for clean, reusable propulsion in space, accommodating various orbits and mission types. However, the dynamics of space tethers are complex. Robust guidance, navigation, and control (GNC) systems, along with compensation propulsion, are essential, especially under asymmetrical conditions, to prevent failures. Continuous research and development in tether technology will pave the way for their integration into future mission architectures, making space travel more accessible and sustainable.