Rocket Lab stirred up excitement on October 6th with the announcement that they will be responsible for launching the NASA Advanced Composite Solar Sail System Technology Demonstration Mission (ACS3) through a Phase 3 Small Business Innovation Research (SBIR) contract, signalling a further vote of confidence in the fast-growing launch company.
Rocket Lab said in their release that the Electron launch vehicle’s “Kick Stage” — which can use a 3D printed “Curie” engine to deploy satellites in unique orbits before deorbiting — was key to the selection, as ACS3 will be operating at a higher altitude than the other payloads on the mission. Rocket Lab has been launching small and medium-sized satellites since 2017, primarily out of their Launch Complex 1 in Mahia, New Zealand. They opened a second launch site in the United States in 2020 on Wallops Island in Virginia.
Solar sails are a still-experimental form of space propulsion that has featured in science fiction for decades, and is starting to become a reality. Solar sails catch streams of light photons much like a traditional sail catches wind, using the momentum of the billions of photons captured by the sail to push a satellite or spacecraft. While the moment-to-moment acceleration from the sail is slight, given enough time in the near-frictionless vacuum of space they could accelerate to a significant fraction of the speed of light. They can even change directions by changing the direction of the sail, much like how sailing ships will change their sail direction in the wind.
Some experimental solar sails have already been launched: the IKAROS sail by the Japanese Aerospace Exploration Agency (JAXA), NASA’s own Nanosail-D project, and the Planetary Society’s Lightsail projects. NASA also has another solar sail project, the NEA Scout, that will be launching as part of NASA’s Artemis 1 launch.
What makes ACS3 different is its components and size. ACS3’s sails are supported by booms made of a composite polymer material reinforced by carbon fiber. NASA says that “this composite material can be rolled for compact stowage, but remains strong and lightweight when unrolled. It is also very stiff and resistant to bending and warping due to changes in temperature.” The booms will be extended using “an innovative tape-spool boom extraction system designed to minimize jamming of the coiled booms during deployment”.
It is unclear, however, whether these are the SHEARLESS booms on NASA’s technology transfer site, or something more novel and advanced.
These spooled and unrolled booms let the sail fit into an impressively tiny space. The fully-unspooled solar sail will be approximately 9 metres (30 feet) per side, yet the sail and booms will be fit into a 12U CubeSat space: about 23 centimeters cubed (or, as NASA describes it, “about the size of a toaster oven”). NASA is already developing a version that scale up the sails to 500 square meters (5400 sq. ft). If everything works as planned, they are also working on further improvements to the boom technology that would enable solar sails as large as 2000 square metres (21,500 square ft).
You can see NASA’s Langley Research Center presenting and demonstrating the technology in this YouTube video. They said that each boom weighs less than 2 pounds (0.9 kilos) and that:
The goal right now is to use these really long booms to build out more complex structures. We will target rollable straight ladders that could be used as ramps to offload equipment, straight trusses for lunar communication and observation towers and to serve as high stiffness beams for surface construction, and curved trusses to create dome structures. All of these could be assembled together like building blocks.
They also said that these composite trusses may be used for lunar habitats and equipment hangers.
The ACS3 is a collaboration between a number of different entities, including both NASA’s own research centers and private enterprises. From the release:
- NASA’s Langley Research Center in Hampton, Virginia, is designing ACS3’s deployable composite booms and solar sail system.
- NanoAvionics of Columbia, Illinois is designing and building the 12U CubeSat for the ACS3 technology demonstration.
- NASA’s Ames Research Center in California’s Silicon Valley is managing the ACS3 project and will oversee final integration of the solar sail payload and CubeSat.
- The Santa Clara University’s Robotics Systems Lab in Santa Clara, California will provide CubeSat operations support for the ACS3 technology demonstration.
- NASA’s Small Spacecraft Technology program within the agency’s Space Technology Mission Directorate is sponsoring the ACS3 project and is providing the funding for the launch.
- NASA’s Game Changing Development program within the agency’s Space Technology Mission Directorate is developing ACS3’s deployable composite boom technology.
The Langley Research Center also credited the German Aerospace Center (DLR) with developing the unit that stores and deploys the composite booms, as well as “performing structural testing of the booms for the project.”
Rocket Lab CEO, Peter Beck, said that “It seems fitting to launch NASA’s Advanced Composite Solar Sail System on Electron, the world’s first full carbon composite orbital launch vehicle. We’re excited to see composites used yet again to unlock new capabilities in space.”
No date has been set for the launch but NASA says that it would be “no earlier than mid-2022.”