Day 2 of the Metamaterial Films for In-Space Propulsion by Radiation Pressure Incubator
Amber Dubill, RIT
The first day of the OSA Incubator Metamaterial Films for In-Space Propulsion by Radiation Pressure ended with breakout sessions for brainstorming ideas for different types of lightsail missions: Inner Solar System, Outer Solar System, and Laser Driven. Each group developed a roadmap for the development of solar sail technology and metamaterials to enable these types of missions. The integration of the two technologies are one key to furthering exploration of space.
Day 2 of the program kicked off with a panel discussing the harsh environments of space. Joe Minow, NASA, and James Moore, Nexolve, discussed the engineering requirements that need to be taken into account when developing materials for interplanetary spacecraft. The metamaterials that may be used in solar sails need to survive long mission durations while maintaining structural and optical integrity. There is concern about large temperature gradients across sails, fast thermal cycles, electrical charging of the spacecraft, and radiation effects. Joe showed that the environment closer to the sun is exponentially harsher in regards to radiation and solar wind. Harry Atwater, Cal Tech, discussed the space environment scenarios that a laser-driven sail would see over a Breakthrough: Starshot mission lifetime.
The breakout sessions yielded reports to share with the rest of the assembly.
- Inner solar system missions using solar sails would greatly benefit from using metamaterials to offset roll disturbance torques due to imperfections in sails. Near term, a passive method of attitude control using diffractive gratings could be implemented on current reflective sails. This could be crucial to offload mass from the design of a spacecraft. In longer term applications, an actively controlled system using diffractive gratings and reflectivity control devices to enable complete attitude control of sail craft could be developed. These metamaterials will need to be tested to the space environment limits, as many of them have not been considered for use in space. New materials could be developed to mitigate active thermal gradients in the sails, as emissivity properties can be tuned to different wavelengths and desired temperatures.
- Outer solar system missions cannot effectively use solar radiation pressure once outside of asteroid belt. For outer solar sail missions, solar sails are useful in gaining delta v for outer solar system transfers by going towards the sun at first. This community calls for metamaterials to enable multifunctionality of these sails, so that once their use for propulsion is finished, they can be used for sensors, antennas, and other capabilities that are needed for further out missions. Again, angular momentum management using diffractive gratings would be useful. In the long term these sails could enable grand tours of the solar system that are not limited by timeline windows. Darren Garbe, NXTRAC, ended on by noting “We are running out of tricks from the 60s and 70s - we need a new bag of tricks to get out past the outer solar system and beyond.”
- Laser sailing missions may be a bit more far out, but the intermediate steps along the way can provide useful knowledge and technological advancement. There is a need to test these metamaterials and their interactions with the high-power lasers that are needed to provide large propulsive forces. Something like an established laser sailing system may be feasible in our lifetime, but full scale demonstrations could be possible within 20 years. The large cost for the development of these systems may be offset by interest in the other applications of metamaterials in cell phones, UV protection, and passive cooling.
Testing is the next big step for these metamaterials to become mainstream in space missions. The metamaterials need to be tested on the ground to extreme space environment limits and they could be tailored to specific missions. The manufacturing of these materials in larger areas would follow. Integration of these metamaterials into space missions within the next few years is crucial to proving the reliability and efficiency of this technology and can occur as solar sail technology is advancing. The product of the two technologies together could support further advancement of these light sails. Light sails are one enabling technology that could allow humans to explore the universe within this lifetime.
The hosts are looking forward to going through all the detailed notes from the working groups and, with help from the participants, continuing the discussions and work. Stay tuned for more on this topic from OSA, including an overview of the work and details on next steps, in a future issues of Optics & Photonics News.
Attendees of the OSA Incubator: Metamaterial Films for In-Space Propulsion by Radiation Pressure.
One of three working sessions during the program on: Inner Solar Systems, Outer Solar Systems and Laser-Light Driven Sail Missions.
