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NASA solar sail tech passes crucial deployment test

On Jan. 30, 2024, NASA cleared a key tech milestone at Redwire's new facility in Longmont, CO, with the successful deployment of one of four identical solar sail quadrants. Two 100-ft lightweight composite booms unfurled the 4,300-sq-ft sail quadrant using novel wound tape-measure technology. [Credit: NASA]

 

 

 

 

By Wayne Smith, NASA Marshall Space Flight Center

In his youth, NASA technologist Les Johnson was riveted by the 1974 novel "The Mote in God's Eye," by Jerry Pournelle and Larry Niven, in which an alien spacecraft propelled by solar sails visits humanity. Today, Johnson and a NASA team are preparing to test a similar technology.

NASA continues to unfurl plans for solar sail technology as a promising method of deep space transportation. The agency cleared a key technology milestone in January 2024 with the successful deployment of one of four identical solar sail quadrants. The deployment was showcased Jan. 30 at Redwire Corp.'s new facility in Longmont, CO.

NASA's Marshall Space Flight Center in Huntsville, AL, leads the solar sail team, comprised of prime contractor Redwire, which developed the deployment mechanisms and the nearly 100-ft-long booms, and subcontractor NeXolve, of Huntsville, which provided the sail membrane. In addition to leading the project, Marshall developed the algorithms needed to control and navigate with the sail when it eventually flies in space.

Watch the intricate mechanical system unfurl the solar sail during test deployment in the video below. [Credit: Redwire screenshot]

 

 

The sail is a propulsion system powered by sunlight reflecting from the sail, much like a sailboat reflects the wind. While just one quarter of the sail was unfurled in the deployment at Redwire, the complete sail will measure 17,780 sq ft when fully deployed, with the thickness less than a human hair at 2.5 microns. The sail is made of a polymer material coated with aluminum.

NASA's Science Mission Directorate recently funded the solar sail technology to reach a new technology readiness level, or TRL 6, which means it's ready for proposals to be flown on science missions.

"This was a major last step on the ground before it's ready to be proposed for space missions," said Johnson, who has been involved with sail technology at Marshall for about 25 years. "What's next is for scientists to propose the use of solar sails in their missions. We've met our goal and demonstrated that we're ready to be flown."

VIDEO: Redwire successfully deploys largest-ever solar sail. [Credit: Redwire]

A solar sail traveling through deep space provides many potential benefits to missions using the technology because it doesn't require any fuel, allowing very high propulsive performance with very little mass. This in-space propulsion system is well suited for low-mass missions in novel orbits.

"Once you get away from Earth's gravity and into space, what is important is efficiency and enough thrust to travel from one position to another," Johnson said. "A solar sail achieves that by reflecting sunlight -- the greater the size of the sail, the greater thrust it can provide."

Some of the missions of interest using solar sail technology include studying space weather and its effects on the Earth, or for advanced studies of the north and south poles of the Sun. The latter has been limited, because the propulsion required to get a spacecraft into a polar orbit around the sun is very high and simply not feasible using most of the propulsion systems available today. Solar sail propulsion is also possible for enhancing future missions to Venus or Mercury, given their closeness to the Sun and the enhanced thrust a solar sail would achieve in the more intense sunlight there.

Moreover, it's the ultimate green propulsion system, Johnson said; as long as the Sun is shining, the sail will have propulsion. Where the sunlight is less, he envisions a future where lasers could be used to accelerate the solar sails to high speeds, pushing them outside the solar system and beyond, perhaps even to another star.

"In the future, we might place big lasers in space that shine their beams on the sails as they depart the solar system, accelerating them to higher and higher speeds, until eventually they are going fast enough to reach another star in a reasonable amount of time," Johnson said.

Designfax sidebar: How is the solar sail system deployed?
NASA's giant solar sail is a spring-loaded system that is rolled up in a shell casing, much like a tape measure is wound. The Triangular Rollable And Collapsible (TRAC) boom technology was developed by the U.S. Air Force Research Laboratory (AFRL). The technology is licensed by commercial companies, including Redwire and Roccor. When the system is fully assembled, it will include four 97-ft-long booms that make up the skeleton of the system. The booms deploy the 2.5-micron-thick, 17,780-sq-ft sail as they are unfurled and support the tension loads during flight.

Want to take a dive into the boom and sail design? Take a look at this NanoSail-D presentation from 2008 that is filled with details and images from a smaller-scale demonstration.

This NanoSail-D Boom and Deployment Subsystem slide shows how the solar sail system works using TRAC technology on a much smaller scale (nano satellite). Note how each boom is made of two opposing shapes. In this case, the booms were made of a super alloy called Elgiloy. [Credit: NanoSail-D presentation, 2008 CubeSat Developers Workshop, Edward E. (Sandy) Montgomery IV, NASA Marshall Space Flight Center, and Charles L. Adams, Jacobs/Gray Research, Inc]

 

 

 

 

If you want to get into the real nitty gritty of how the almost 100-ft-long composite booms, made of ultra-thin carbon fiber-epoxy prepregs for this latest project, were developed and tested, go deeper by reading the paper "Solar Cruiser TRAC Boom Development" by Lee Nguyen, Zachary McConnel, Kamron A. Medina, and Mark S. Lake, all of Redwire Deployable Solutions, Longmont, CO. It is filled with test data and details about assembly, load tests and buckling, and more. Of the system design, this paper says, "Compared with other spool-rolled booms, the TRAC boom cross-section provides the highest deployed second moment of inertia for a given flattened height resulting in a high torsional stiffness, which is largely the reason the design has gained recent acceptance for deploying large, lightweight structures in space."

To learn more about solar sails and other NASA advanced space technology, go to nasa.gov/space-technology-mission-directorate.

Published February 2024

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