由太阳光驱动的宇宙飞船将从SpaceX火箭上发射（在线收听）

Sunlight-Powered Spacecraft Set to Launch Aboard SpaceX Rocket

A major experiment in solar sailing is set to launch this month.

Solar sailing is a method that can push, or propel, a vehicle through space. A spacecraft is attached to a large solar sail to capture wind pressure from sunlight. This pressure is the force for movement.

A small spacecraft is set to demonstrate this technology after being launched from a rocket on June 22. The spacecraft, called LightSail 2, will launch from a Falcon Heavy rocket built by American aerospace company SpaceX. The rocket will launch from Florida’s Kennedy Space Center.

LightSail 2 is a small spacecraft that weighs about five kilograms. It was designed by a not-for-profit group, The Planetary Society. Such small spacecraft are known as CubeSats. These provide a low-cost way for scientists, governments and private organizations to carry out space experiments.

LightSail 2 will be part of a U.S. Department of Defense operation that will also launch about 24 satellites. The Planetary Society launched a similar spacecraft in 2015 called LightSail 1. That spacecraft successfully tested the sail deployment system.

American scientist, writer and television star Carl Sagan, along with others, created the Planetary Society. Bill Nye currently leads the organization. Nye says the operation will attempt to raise the first solar sail spacecraft to orbit Earth.

In a statement, Nye added that this month’s launch could complete one of Sagan’s major goals. "Forty years ago, my professor Carl Sagan shared his dream of using solar sail spacecraft to explore the cosmos. The Planetary Society is realizing the dream," he said.

The Planetary Society said citizen donations have paid for the project. Nye said thousands of people from all over the world came together to support it. He said the society was created to “empower people everywhere to advance space science and exploration.” Now, he said: “We are go for launch!"

A main goal of the operation is to demonstrate the power of sunlight to propel spacecraft without the need for costly rocket fuel.

Light is made up of particles called photons. Photons themselves do not have any mass. But when they travel through space they can pick up momentum.

The sail used with LightSail 2 has a very bright surface that can reflect light. When the photons in the light hit the solar sail, it creates momentum. This momentum results in small pushes as the photons repeatedly strike the sail.

Once in space, LightSail 2 will deploy its solar sail system, which covers a total area of about 32 square meters. Over time, it will seek to raise its orbit using the small, continual pushes from solar photons.

The sail will turn towards the Sun for half of each orbit, “giving the spacecraft a tiny push no stronger than the weight of a paper clip,” the Planetary Society said in a statement. “For about a month after sail deployment, this continual thrust should raise LightSail 2's orbit by a measurable amount.

Project officials say they expect LightSail 2 to fly to an orbit of 720 kilometers high. The spacecraft might be able to be seen in the night sky to observers within 42 degrees of the equator, they added.

“This will be the first time navigating by light in Earth orbit,” Nye told the NBC’s Mach website. He noted that the amount of orbital energy needed to move LightSail 2 forward can be increased by changing the position of the sail.

When a solar sail faces the Sun directly, photons push the spacecraft forward, away from the Sun. But the sail can move in other directions permitting control over where it travels, the society said on its website.

I’m Bryan Lynn.

Words in This Story

cosmos – v. the whole universe

advance – v. develop or progress

momentum – n. the force that something has when it is moving

reflect – v. send back or bounce off

paper clip – n. small piece of metal used to hold pieces of paper together

thrust – n. upward push or force

navigate – v. find the right direction to travel by using maps or other equipment