[Reading Science] The 'Space Clipper' with Sails Unfurled... Solar-Powered Space Voyage

NASA, ACS3 Spacecraft Launch
Test of Solar-Powered Propulsion Instead of Rocket
Beginning for Deep Space Exploration

A spaceship (宇宙船·Spaceship) relies on the thrust of rockets to leave Earth and travel through space. However, there is a type of spaceship that overturns this common knowledge. It is a spaceship that sails using sails. The National Aeronautics and Space Administration (NASA) recently conducted an experiment with a space sailboat that uses sails instead of rockets. The announcement of the arrival of a spaceship that travels by sail, something previously only imagined in movies, has attracted the attention of space enthusiasts.

An illustration of NASA's spacecraft ACS3 deploying solar sails in space. Photo by NASA

On the 25th, Rocket Lab's Electron launch vehicle headed to space from the Mahia launch site in New Zealand, carrying Korea's first microsatellite constellation and other cargo. Among the cargo was NASA's commissioned "space sailboat" ACS3 (Advanced Composite Solar Sail System). As its name suggests, the main mission of this spacecraft is to experiment with navigation using sunlight. This attempt is the first trial of a solar sail system made from composite materials. This experiment differs from previous studies on spacecraft propulsion using solar wind.

The principle is as follows. A large metal sail is deployed, and the pressure of sunlight is used to propel the spacecraft forward. Unlike conventional spacecraft, no rocket propellant is needed. NASA is researching solar light propulsion systems for future deep space exploration. For deep space exploration, a low-thrust propulsion system that can be used for a long time is necessary.

ACS3 began its independent journey one hour after separating from the rocket along with Korea's first microsatellite constellation. ACS3's orbit is approximately 965,606 meters above the ground.

ACS3 looks completely different from typical satellites that deploy solar panels to start operation. First, it must unfold four support arms. Then, four triangular sails are deployed. From the surrounding view, a large square-shaped sail is formed. Photos taken during the launch preparation show that ACS3 is noticeably smaller than Korea's microsatellite constellation, but when the sails are deployed, the area reaches about 80 square meters. Because the sails are so large, they can be observed from the ground through telescopes. According to NASA, due to the reflective material of the sail, it becomes as bright as Sirius, the brightest star in space, when illuminated by light.

The sail of ACS3 is being unfolded on the ground. Photo by NASA

The support arms and sails of ACS3 are made from new materials. The main mission is to test sails made of flexible polymers and carbon fiber materials. Compared to past experiments, this sail uses sturdier rods to secure support. It is designed to withstand more sunlight. Keith Wilkie, mission lead at NASA's Langley Research Center, explains that compared to previous sail designs, this one is sturdier yet can bend like a tape measure. Just as a sailboat's sail bends when catching the wind to propel the boat, ACS3's sail stretches and gains propulsion by receiving sunlight. This is what differentiates it from previous sails. Using heavy metals or composite materials makes it difficult to apply to the recent trend of small CubeSat satellites. Thanks to changes in the sail support materials, the supports minimize changes due to temperature fluctuations and can be mounted on small CubeSats. The satellite part of ACS3 was manufactured by NanoAvionics.

ACS3 main body manufacturing process. Photo by NASA

The solar sail will undergo initial flight tests in Earth orbit for the next two months before beginning practice in moving small CubeSats. NASA plans to use the data obtained from this test to design larger space sailboats. The potential target is a solar sail about 500 square meters in size, roughly the size of a basketball court. The ultimate goal is a sail half the size of a soccer field.

There were quite a few challenges during the development process. They had to ensure the sail could be properly deployed and solve the problem of communication difficulties with ground stations when the sail is deployed.