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The Science Behind Drag Sails: A Solution for Satellite De-orbiting

Illustration of a drag sail deployed in orbit, showcasing its role in deorbiting small satellite missions and advancing Small Sat mission technologies.

What is a Drag Sail and How Does it Work?

Drag sails are thin-film membranes deployed via lightweight booms, designed to increase aerodynamic drag on satellites in Low Earth Orbit (LEO). By providing a large surface area, drag sails leverage the residual atmospheric particles in LEO to create resistance, which gradually reduces a satellite’s velocity and altitude until it reenters Earth’s atmosphere and burns up.

Deployment of a drag sail can be triggered by a command from the satellite’s host system or autonomously based on pre-programmed deployment times. This dual capability ensures the sail can function even if the satellite’s primary systems become inoperative. For example, NASA’s NanoSail-D2 successfully demonstrated how drag sails can operate independently to de-orbit a satellite efficiently.

The structure of a drag sail typically includes radiation-hardened electronics, ensuring reliability in the harsh conditions of space. Lightweight booms, often made of carbon-fiber composites, deploy the sail, while the material itself is designed to withstand atomic oxygen exposure, temperature extremes, and micro-meteoroid impacts. These design features ensure the drag sail remains operational throughout its mission.

Advantages of Drag Sails as a De-orbiting Solution

Drag sails offer several advantages that make them one of the most practical solutions for satellite de-orbiting, particularly for missions in LEO:

  1. Passive Operation: Unlike active de-orbiting systems requiring propulsion or external commands, drag sails function passively once deployed. This minimizes the need for additional onboard power or fuel.
  2. Compact Storage: Drag sails are designed to fold into small, compact volumes, making them ideal for small satellite missions where space is at a premium.
  3. Cost-Effectiveness: With their simple mechanical design, drag sails are less expensive to manufacture and integrate than complex active systems, making them an attractive option for cost-conscious missions.
  4. Regulatory Compliance: Drag sails enable satellites to meet international orbital debris mitigation guidelines, such as the 25-year de-orbiting rule or the newer 5-year requirement for altitudes below 800 km.

Reliability: Radiation-hardened components and life-tested materials ensure long-term deployment reliability, even after years in orbit.

For example, the CanX-7 (pictured above) mission deployed a segmented drag sail that successfully increased its altitude decay rate from 0.5 km/year to 20 km/year, allowing the satellite to comply with de-orbiting regulations.

Proven Missions and Current Drag Sail Technology

Numerous missions have demonstrated the effectiveness of drag sail technology. Here are a few notable examples:

  • NanoSail-D2 (2010): Deployed from NASA’s FASTSAT mission, NanoSail-D2 showcased the potential of drag sails by demonstrating a low-mass, high-surface-area sail. The mission reentered Earth’s atmosphere within nine months of deployment.
  • CanX-7 (2017): Developed by the University of Toronto’s Space Flight Laboratory, this mission deployed four modular drag sails. Each module had its own telemetry and command system, allowing independent operation to mitigate risks.
  • Exo-Brake (2017-2022): NASA Ames’ Exo-Brake program used tension-based drag devices for precise reentry targeting. For instance, TechEdSat-13 demonstrated autonomous navigation to specific Earth locations during reentry.
  • ADEO-N2 (2022): High Performance Space Structure Systems (HPS) deployed its ADEO-N2 drag sail from D-Orbit’s ION carrier, achieving a high Technology Readiness Level (TRL) of 9.
  • SBUDNIC (2022): A $30 drag sail developed by Brown University students reduced orbital decay time by five years, showcasing how low-cost solutions can contribute to debris mitigation.

These missions underline the growing maturity and reliability of drag sail technology, with applications ranging from small CubeSats to larger spacecraft.

Key Features of High-Performance Drag Sails

To ensure effectiveness and reliability, high-performance drag sails incorporate several critical features:

  1. Radiation-Hardened Electronics: Drag sails must operate reliably in the radiation-rich environment of space. Hardened electronics prevent failures caused by solar flares or cosmic rays.
  2. Durable Sail Material: The membrane material must withstand exposure to atomic oxygen, UV radiation, and temperature fluctuations. Materials like Kapton or Mylar are commonly used due to their durability and lightweight properties.
  3. Life-Tested Batteries: To ensure deployment even after years in orbit, drag sails use batteries that remain functional for extended durations.
  4. Modular Design: Many drag sails, such as the CanX-7, feature modular designs that allow for independent deployment of multiple sail sections. This mitigates the risk of total mission failure if one section malfunctions.
  5. Customizability: Advanced systems like the ADEO series allow tailoring of sail sizes and configurations to match specific satellite geometries and de-orbiting requirements.

The Role of Drag Sails in Advancing Satellite Decommissioning

With the increasing density of satellites in LEO, the risk of space debris and collisions has grown exponentially. Drag sails play a pivotal role in mitigating this risk by providing a reliable, passive means of satellite de-orbiting. They are particularly valuable for small satellite missions and CubeSats, which often lack the resources for active de-orbiting systems.

Drag sails also align with global efforts to promote sustainable space operations. By enabling satellites to de-orbit within regulatory timelines, they help prevent the accumulation of debris and ensure the long-term usability of orbital environments.

Moreover, innovations in drag sail technology continue to expand their applications. From tension-based designs like NASA’s Exo-Brake to inflatables like Surrey Space Centre’s InflateSail, the variety of available systems offers mission planners a wide range of options tailored to their needs. These advancements are not only reducing costs but also making drag sails more accessible for a broader range of missions.

Conclusion

Drag sails represent a proven and practical solution for satellite de-orbiting, offering reliability, simplicity, and cost-effectiveness. By accelerating orbital decay through aerodynamic drag, they address one of the most pressing challenges in modern space exploration: the growing problem of space debris.

From missions like NanoSail-D2 and CanX-7 to cutting-edge technologies like ADEO and Exo-Brake, drag sails have demonstrated their ability to meet de-orbiting requirements across a range of satellite sizes and mission profiles. With continued innovation, these systems will play an increasingly important role in ensuring the sustainability of space operations.

For mission planners and engineers, understanding the science and applications of drag sails is critical for designing spacecraft that are not only effective but also environmentally responsible. Drag sails are more than just a tool—they are a step forward in humanity’s efforts to maintain the usability and safety of outer space.

Discover more information about drag sail products in the ‘De-Orbiting Devices’ category of the SmallSat Catalog. Orbital Transports delivers complete small satellite programs, from initial concept to completed mission, offering cost-effective, low-risk solutions by coordinating supply chain partners and connecting technologies into an overall mission package.