Technology

Sun lights new space exploration horizon

 By Esteban Pages

On May 20, 1976. Carl Sagan sat for an interview with then-“Tonight Show” host, Johnny Carson. In it, Sagan presented an innovative prototype: a solar sail meant to conquer cost-effective space exploration. Fast forward 40 years later, and former Carl Sagan alumnus and current CEO of the Sagan-founded Planetary Society, Bill Nye, is on the cusp of fulfilling his teacher’s vision…

Solar power and space exploration

Solar-powered space travel ambitions trace back as early as 1958, when the very first solar-powered satellite, Vanguard 1, was launched. It showcased PV-based power generation as a viable technology before it stopped transmitting in 1964.
Today, innovation and scientific research have propelled solar-based space aircraft to a whole new level, as attested by International Space Station (ISS), a state-of-the art, world-class laboratory in space result of the cooperation between Roscosmos (Russia), NASA (USA), ESA (Europe), JAXA (Japan) and CSA (Canada).
ISS is equipped with four sets of solar arrays counting a total of 262,400 high efficiency monocrystalline silicon solar cells over an area of 2,500m2, mounted on blankets that can fold or deploy as needed, including gimbals to rotate the arrays to face the sun. These solar arrays are said to have the aggregate capacity of producing between 84 to 120kW of electricity, “enough to provide power to more than 40 homes”, cites ISS data.
The flagship of this international scientific achievement is also rather costly. Business Insider reports its development and construction cost close to US$150 million, while The Verge claims it costs only NASA US$3 to US$4 million per year to operate its sector of the ISS. The former is even considering handing over its operation to the private sector by opening it up to commercial space travel.

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The International Space Station (NASA)

The quest for cost-effective spacecraft

Moreover, NASA’s FY 2019 President’s budget states deep exploration systems alone cost $4,558.8 million while exploration research and technology amounted to $1,002.7 million. Together, both concepts comprise close to 30% of the total $19,892.2 million assigned to NASA.
The capital-intensive nature of space travel and exploration calls for innovative means to answer to humanity’s thirst for pushing the boundaries of space, albeit doing so with an optimized use of resources and technology. Elon Musk’s SpaceX venture provided a first alternative by focusing on reusable rockets.
In line with SpaceX’s philosophy, driven by the potential to materialize Carl Sagan’s solar sail dream, The Planetary Society set out to develop an operational solar sail as early as 1999, Cosmos 1. Six years later, it launched on a Russian Volna rocket but failed to reach orbit. In 2009, it began development of the LightSail, launched aboard an Atlas V rocket and successfully completed its mission in 2015.
The Planetary Society reached yet another milestone on June 25, 2019, as the LightSail 2, an upgraded version of its 2009 predecessor, was launched aboard a SpaceX Falcon Heavy rocket inside its Prox-1 carrier spacecraft. It is in orbit at the time of writing.

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Planetary Society's Solar Sail (Planetary Society)

Then Planetary Society’s solar sail project

The Planetary Society’s Solar Sail development expenses add up to $7 million from 2009 to 2019, which on its own stands as a considerable achievement. Stellar Exploration, Inc. is responsible for its design and construction. This innovative technology uses CubeSats, small, standardized satellites with a simplified manufacturing process, as it leverages hardware products ready-made and available to the general public, providing a cost-effective alternative to traditional satellites.
CubeSats’ Achilles’ heel, however, is propulsion. That’s where solar sailing comes in as its reflective sails utilize sunlight’s momentum for propulsion. Besides the reduced costs, The Planetary Society boasts that “a solar sail-propelled spacecraft could reach distant planets and star systems much more quickly than a rocket-propelled spacecraft because of the continual acceleration that solar sailing provides”.
The latest version of this scientific breakthrough, the Solar Sail 2, consists of a lightweight aluminum alloy hull, torque rods and a momentum wheel for maneuvering; an RF monopole antenna and dual 2-megapixel cameras with fish-eye lenses for solar sail imaging; four solar arrays and eight rechargeable lithium-ion batteries for eclipse operation; and weighs in as little as 5kg. When closed, it is barely bigger than a loaf of bread. When fully deployed, the total sail area reaches 32m2, as large as a boxing ring.

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A PhoneSat, a CubeSat module that uses commercially available smartphone technology to collect data on the long-term performance of consumer technologies used in spacecraft (NASA)

The LightSail 2 odyssey

As planned, the LightSail 2 team was successfully released from its Prox-1 carrier vehicle on July 2, 2019. The Planetary Society reported it “deployed its radio antenna and began transmitting health and status data, as well as a morse code beacon indicating its call sign. The mission team received LightSail 2’s first signals on 2 July at 01:34 PDT”.
On July 3, 2019, after confirming the LightSail 2 was healthy in orbit as intended, the mission team based at Cal Poly San Luis Obispo in California prepared the aircraft’s sail deployment by going through each element of the team’s 73-step checklist to ensure all systems were a go by performing various tests.
Part of the tests included taking test pictures from the solar panel-mounted cameras. In them, the LightSail 2 caught the earth’s spherical shape, facing the sun. The Planetary Society claims the pictures were uploaded unmodified.

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One of the test pictures taken by the LightSail 2 (The Planetary Society)

The solar sail’s deployment was originally scheduled for July 8, 2019, but the team decided to postpone it until July 21, 2019 so they can perform additional tests and software updates for the aircraft’s optimal performance. Alas, the team has made available a mission control dashboard so you can keep track of the SolarSail 2’s most up-to-date progress, including its position relative to the earth.

READ MORE: Using the Sun to orbit the Earth by Peter Ward

about the author
Esteban Pages