Shannon Stirone

For centuries, it has been a dream: traveling through space powered only by the solar wind. It was first imagined in the 1600s by Johannes Kepler, the German astronomer. Centuries later, Arthur C. Clarke moved it into the realm of science fiction in “Sunjammer,” a 1964 short story. Carl Sagan, the cosmologist and co-founder of the Planetary Society, thought it could be more than a speculative fantasy, and began in the 1970s to promote building solar sails for space exploration.

On Tuesday, solar sailing could take its next major step to becoming a proven technique for navigating the voids between worlds.

Last month, the Planetary Society’s spacecraft, LightSail 2, traveled to space aboard a SpaceX Falcon Heavy rocket. After 10 years of planning and over 40,000 private donations worth $7 million, the cubesat has reached a high enough orbit around Earth and some technical issues have been worked out by engineers on Earth. With the press of a button on the ground in California on Tuesday morning, the mission’s controllers hope that the spacecraft’s sails will unfurl, opening the curtain on the next act of spaceflight.

What is solar sailing?

One limitation of space travel is that power sources eventually run out.

But the sun is a source of constant energy. It is always releasing photons into space. While these particles don’t have mass, they have momentum. Solar sailing relies on the ever so gentle nudge of photons to push a sail forward, moving whatever is behind the sail in another direction.

Sailing could be one of the most fuel efficient options for space travel. While the force exerted on a solar sail is about the same as you might feel from the weight of a piece of paper in the palm of your hand, the momentum is able to build, increasing the speed of the sail over time.

For example, NASA’s twin Voyager spacecraft, flying on pure momentum since they ran out of fuel, needed more than 40 years from launch to reach the boundary of our solar system. But if they had solar sails, the lengths of their trips could have been nearly cut in half.

How will LightSail 2 work?

LightSail 2 aims to become the first steerable solar sail ever launched into orbit around Earth. It is a loaf-sized cubesat carrying a boxing-ring-sized solar sail. Made from a thin mylar material, these sails are designed to blossom like a space-lotus and collect the sun’s energy.

The cubesat has a momentum wheel, which allows the Planetary Society’s engineering team on Earth to guide its mylar sails. That will keep the spacecraft at a 90-degree angle to the sun at all times, not unlike the way a sailboat needs to tack into the wind to move.

As LightSail orbits Earth, engineers on the ground will attempt to extend the farthest point in its orbit, called apogee. To do this, the sail must get enough of a push from the sun, and also rely on steering from the ground.

“If everything goes perfectly, we ought to be able to raise the apogee by about 1,640 feet per day,” says Dave Spencer, an aeronautics professor at Purdue University in West Lafayette, Indiana, and LightSail’s mission manager.

What will happen during deployment?

On Tuesday at 11:40 a.m. in California, 2:40 p.m. ET, engineers will send an order to orbit, and over about two minutes, LightSail 2 will unfurl its sails.

During the deployment, two wide-angle cameras on the cubesat will capture 32 images. “It will effectively give us a kind of movie of the sail deployment,” Spencer said.

The primary mission is to last around a month, and after that LightSail could orbit Earth for up to a year. Sometimes it will be visible from Earth with the naked eye, and the Planetary Society will provide updates on where it can be seen.

Eventually, Earth’s gravitational pull will drag the cubesat back toward the atmosphere, where it will burn up.

Has this been tried before?

LightSail 2 follows LightSail 1, launched in 2015 as a test. While accomplishing some of its goals, the test was hindered by a number of engineering snags.

The very first solar sail spacecraft, Ikaros, was launched in 2010 by the Japan Aerospace Exploration Agency. Although it was not steerable, it traveled past Venus. It entered orbit around the sun and was last heard from in 2015.

Early in the next decade, NASA plans to launch, NEA Scout or, Near Earth Asteroid Scout. This small cubesat will use a solar sail to visit a near-Earth asteroid to collect data and send it back to Earth.

This article originally appeared in <a href="https://www.nytimes.com/2019/07/23/science/lightsail-solar-sail.html" id="326b4555-b71e-3ec4-afb5-7453043551b6">The New York Times</a>.

Sailing across the cosmos is finally becoming a reality.

Sailing Through Space on Solar Wind? LightSail 2 Will Try

Engineers in California pressed a button on Tuesday that unfurled the sails on a satellite that can be steered around Earth, advancing long-held hopes for an inexhaustible form of spaceflight and expanding the possibilities for navigating the voids between worlds.

For centuries, it was only a dream: traveling through space propelled by the solar wind. It was first imagined in the 1600s by Johannes Kepler, the German astronomer who described the laws of the planets’ orbits. In 1964, Arthur C. Clarke moved it into the realm of science fiction in “Sunjammer,” a short story. Carl Sagan, the cosmologist, believed it could be more than a speculative fantasy and in the 1970s began promoting the building of solar sails for space exploration.

After 10 years of planning and more than 40,000 private donations worth $7 million, that idea took flight Tuesday, as LightSail 2, a spacecraft built for the Planetary Society, co-founded by Sagan, began what its creators hope will be a year of sailing around Earth.

“This is still one of the most feasible pathways to have real interstellar space travel in the future,” said Sasha Sagan, a writer as well as the daughter of the astronomer.

If it succeeds in its mission, it will contribute to overcoming one of the greatest limitations on the outer bounds of space travel — that the power that steers spacecraft, usually hydrazine fuel, eventually runs out.

In contrast, the sun is a source of constant energy. It is always releasing photons into space. While these particles don’t have mass, they have momentum. Solar sailing relies on the ever so gentle nudge of photons to push a sail forward, moving whatever is attached to the sail in the desired direction.

Other fuel sources, such as solar power and ion propulsion, can power spacecraft for decades, but solar sailing could eliminate their need for fuel altogether.

“There is a limitless supply of solar pressure,” said Dave Spencer, an aeronautics professor at Purdue University in West Lafayette, Indiana, and LightSail’s mission manager.

Sailing could be one of the most fuel efficient options for space travel. While the force exerted on a solar sail is about the same as what you might feel from the weight of a piece of paper in the palm of your hand, the momentum is able to build, increasing the speed of the sail over time.

For example, NASA’s twin Voyager spacecraft, flying on pure momentum since they ran out of fuel, needed more than 40 years from launch to reach the interstellar medium. But if they had been powered by solar sails, their trips could have been completed in just over half that time.

Japan’s space agency, JAXA, experimented in 2010 with the first solar sail spacecraft, Ikaros. That probe traveled past Venus but lacked mechanisms for steering. It is orbiting the sun and was last heard from in 2015.

NASA is also experimenting with the technology. Early in the next decade, it plans to launch Near Earth Asteroid Scout. That small cubesat will use a solar sail to visit and study an asteroid.

For now, space agencies will be watching the performance of LightSail 2, a cubesat that is about the size of a loaf of bread.

The spacecraft was launched last month by a SpaceX Falcon Heavy rocket and has since been orbiting Earth while its managers on the ground prepared to unfurl its sails like a space-lotus.

At 11:40 a.m. in California, 2:40 p.m. ET, the mission’s managers sent an order to orbit and received readings indicating that LightSail 2 had successfully unfurled its sails.

“I’m really excited, things went just perfectly” Spencer said.

During the deployment, two wide-angle cameras on the cubesat were to capture 32 images. “It will effectively give us a kind of movie of the sail deployment,” Spencer said.

LightSail 2 is the first steerable solar sail ever launched into orbit around Earth. Its solar sail is about the size of a boxing ring and made from a thin Mylar material. It blossomed Tuesday and began to collect the sun’s energy.

The cubesat has a momentum wheel, which allows the Planetary Society’s engineering team on Earth to guide its sails. That will keep the spacecraft at a 90-degree angle to the sun at all times, not unlike the way a sailboat needs to tack into the wind to move.

“It’s a much more agile solar sail than has been flown before,” Spencer said.

As LightSail orbits Earth, engineers on the ground will attempt to extend the farthest point in its orbit, called apogee. To do this, the sail must get enough of a push from the sun and also rely on steering from the ground.

“If everything goes perfectly, we ought to be able to raise the apogee by about 1,640 feet per day,” said Spencer in an interview before the deployment.

The primary mission is to last around a month, and after that LightSail 2 could orbit Earth for up to a year. Sometimes it will be visible from Earth with the naked eye, and the Planetary Society will provide updates on where it can be seen.

As the spacecraft’s name implies, LightSail 2 follows LightSail 1, launched in 2015 as a test. While accomplishing some of its goals, the test was hindered by a number of engineering snags.

LightSail 2 Unfurls Sails, Next Step Toward Space Travel on Solar Winds

The ability to sail across the cosmos, powered by the energy of the sun, is finally becoming a reality.

SpaceX’s Falcon Heavy rocket is set to blast off from Kennedy Space Center in Florida. This will be the third trip for the Falcon Heavy. Its 2018 test launch lofted founder Elon Musk’s Tesla roadster into the solar system, and a second mission in April carried a Saudi communications satellite to orbit.

This time it’s carrying 24 satellites for the Defense Department and other customers, and Musk called it SpaceX’s “most difficult launch ever.” A successful mission could lead to additional business from the United States government for Falcon Heavy.

When is the launch, and how can I watch it?

The launch is scheduled for 2:30 a.m. Eastern time, and the window to blast off lasts until 3:30 a.m. Although the window to take off opened at 11:30 p.m. Monday, SpaceX pushed back the launch time for more checks of ground systems.

An hour before the rescheduled flight time, the company tweeted that it was on track to launch. Local authorities alerted the public in Florida to expect loud noise from the launch and landing attempts.

If the launch gets postponed for any reason, SpaceX can try again Tuesday night.

The launch will be streamed on the internet on SpaceX’s website.

What will Falcon Heavy carry?

The mission is called Space Test Program-2, and is a partnership between the Defense Department, NASA, the National Oceanic and Atmospheric Administration and a number of private companies. The 24 separate satellites — including an Air Force satellite for basic research as well as cremated remains of 152 people — are all packed together in an integrated payload and will be gradually deployed to a variety of orbits. Below is some of the rocket’s most interesting cargo.

— LightSail-2

The Planetary Society’s LightSail-2 cubesat has waited a decade to launch into space. First proposed and championed by Carl Sagan in the 1970s, this satellite is the size of a loaf of bread and is carrying what is known as a solar sail.

Solar sailing is much like sailing in the ocean. Instead of canvas, LightSail-2 will use mylar sails — nearly 20 miles of them — that open wide to collect as much sunlight as possible. Photons from the sun don’t have any mass, but they do have momentum, and that is just enough to slightly nudge the solar sails, like wind on the open ocean. The cubesat includes a momentum wheel so that engineers on the ground can steer the sail.

A week after launch, the massive sails will spread out and begin using sunlight to lift the cubesat into a higher orbit. The goal is to reach 450 miles above Earth, which would make LightSail-2 the first solar sail to use only the power of sunlight to enter a high orbit. It would then orbit Earth for about a year.

“We’ve made all sorts of vital and very significant improvements to the spacecraft. So I’m very excited about this.” said Bill Nye, the “science guy” and chief executive of the Planetary Society.

Proving the technology works would have significant implications for the future of deep space exploration. When robotic space explorers launch, they carry limited fuel. But solar sailing could provide an alternative propulsion method with nearly limitless fuel, improving the prospects of exploring the farthest reaches of our solar system, or even possibly a journey to other stars.

— Green Propellant Infusion Mission

A NASA payload, this small satellite is a test of rocket fuel that is more environmentally friendly.

Most spacecraft use a propellant called hydrazine, which is highly toxic. To even be near hydrazine, a person must wear a protective Hazmat suit.

This new, less toxic fuel is made of a hydroxyl ammonium nitrate fuel/oxidizer blend, called AF-M315E that was originally developed by the Air Force but never used in space. Not only does this green propellant pose less of a threat to humans handling it, but it’s also more efficient.

— Deep Space Atomic Clock

To track missions in deep space, NASA and other space agencies rely on radio signals, waiting for them to traverse the long distances. Robotic probes constantly call home to Earth to confirm the current time and their location. But space agencies need a more timely way to track their spacecraft and their future human missions.

Atomic clocks track vibrations inside an atom like cesium, to measure time accurately. Aboard Global Positioning System satellites orbiting Earth, atomic clocks help precisely triangulate distances traveled over periods of time. But the technology has never been used in deep space. If the Deep Space Atomic Clock is tested successfully, future missions in deep space could navigate the solar system with something like GPS.

Will SpaceX stick the landing?

One of SpaceX’s major selling points for those who need to go to space — including the U.S. military, NASA and private companies — is the cost-effectiveness of the company’s reusable rockets.

The company has landed the booster stages of many rockets, and then reused them. That will also occur with this launch. Its side boosters landed in April; it’s the first time the Defense Department has allowed its hardware to be launched aboard a previously used rocket.

After Falcon Heavy’s launch, SpaceX will attempt to land all three boosters back on Earth. The rocket’s two side boosters will touch down at about the same time at Kennedy Space Center, which the company has already done twice. Landing the center booster is more difficult, and the Heavy failed on its first landing attempt aboard a drone ship in the Atlantic Ocean in 2018. But it touched down successfully in April.

While the floating landing platform ship, named Of Course I Still Love You, was 25 miles off the coast of Florida for that return, it will be more than 700 miles away this time.

This article originally appeared in <a href="https://www.nytimes.com/2019/06/25/science/falcon-heavy-spacex-launch.html" id="2c6482a7-e7b1-3b59-aaee-f508bad46c3c">The New York Times</a>.

SpaceX Falcon Heavy's 3rd launch -- how to watch

The world’s most powerful operating rocket will take flight again Tuesday morning.

Last year, two satellites the size of cereal boxes sped toward Mars as though they were on an invisible track in space. Officially called MarCO A and MarCO B, they were nicknamed WALL-E and EVE, after the animated robots from the Pixar movie, by engineers at NASA.

They were just as endearing and vulnerable as their namesakes from “WALL-E.” The satellites, known as cubesats, were sent to watch over NASA’s larger InSight spacecraft as it attempted a perilous landing on the surface of Mars at the end of November.

Constellations of small satellites like the MarCOs now orbit Earth, used by scientists, private companies, high school students and even governments seeking low-budget eyes in the skies. But never before had a cubesat traveled 90 million miles into space.

On Nov. 26, as the InSight lander touched down, its status was swiftly relayed back to Earth by the two trailing cubesats. The operation was a success, and the performance of the MarCO satellites may change the way missions operate, enabling cubesats to become deep space travelers in their own right.

NASA engineers weren’t sure what to expect when the MarCO mission launched in May. “I think it’s opened up so many doors and kind of shattered expectations,” said Anne Marinan, a systems engineer at the Jet Propulsion Laboratory in Pasadena, California. “The fact that we actually got as far as we did with both satellites working was huge.”

About a month after dropping InSight onto Mars, NASA lost contact with the MarCOs. The agency may attempt to wake them up someday, but for now WALL-E and EVE are silently roaming the solar system, proof of a new space exploration technology that almost never got to the launchpad.

Uncanceling the Cubesat Program

The MarCO mission was canceled repeatedly. After all, the primary goal of NASA’s InSight mission was to land a stationary spacecraft on Mars and listen for marsquakes, giving scientists an improved picture of the red planet’s internal makeup.

And multiple spacecraft orbiting Mars already relay information from its surface back to Earth. The cubesats wouldn’t play a direct role in InSight’s success or failure, so it was a challenge to persuade NASA to support a nonessential program using unproven technology.

The MarCO team fought hard, prevailing at last with the argument that at a cost of only $18 million, the idea was worth taking a chance on. If these two tiny satellites worked well, it would mean that not only could similar spacecraft support big planetary missions in the future, but also that cubesats might carry instruments of their own.

Proving the technology’s reach could stretch NASA’s funding, the engineers said, while creating opportunities for wider exploration of the solar system.

As InSight safely touched down on Mars, the MarCOs were zipping past the planet, collecting readings from the landing and relaying them home more swiftly than the satellites currently orbiting Mars could.

“We had some astonishing statistics,” said John Baker, manager of the SmallSat program at JPL. “We ended up getting 97 percent of all the InSight data back. And that’s because we had two small spacecraft at exactly the right position over the planet to receive the signals.”

Having custom cubesats overhead meant that NASA did not need to use other Martian satellites or worry about their alignment at the time of landing. If future missions tow along their own MarCOs, teams back on Earth may always know how their spacecraft are doing.

The creativity of their design contributed to the cubesats’ success. Before they began constructing the MarCOs, the team made 3D models and used yarn to plan how best to run the guts and wiring inside. The MacGyver-like improvisation resulted in part from the program’s low budget.

The cubesats run on solar power, and their propellant is fire extinguisher fluid. Lining the front of both spacecraft are eight pen-width nozzles that spray cold gas. The cameras onboard are off the shelf, and the radio is similar to that in an iPhone.

On their six-month journey to Mars, both cubesats occasionally lost contact with Earth. A couple of months after launch, MarCO B sprang a fuel leak and started spinning out of control. The team thought they’d lost it.

“Management is slowly encroaching upon the room,” said Andrew Klesh, MarCO’s chief engineer, describing the scene. “We started to look at all the data. We broke apart the problem, and within about 24 hours we had MarCO B back under control.”

Just a day before landing, MarCO B stopped communicating with Earth again. The cubesat came back online just in time. The InSight probe moved into the Martian landing phase that NASA officials know as “seven minutes of terror,” and both spacecraft spoke to Earth the entire time.

The Future Is Getting Smaller

While inexpensive cubesats like the MarCOs may serve as real-time communication relays for future deep-space missions, NASA has more adventurous goals in mind, some of which were hinted at in last week’s budget proposals by the Trump administration.

“When we have big spacecraft, you don’t want to necessarily take it into a very risky situation,” Baker said. “But you can take an inexpensive probe and send it down to search or to get up close to something and examine it.”

Baker and others at JPL are working on planetary cubesat missions. One proposal, nicknamed Cupid’s Arrow, envisions using the spacecraft to study the opaque atmosphere of Venus.

In other proposals, the next iteration of interplanetary cubesats would be scouts deployed by larger spacecraft studying worlds that could be hospitable to life. They could be sent into the plumes of Enceladus, Saturn’s icy moon, which ejects water vapor into space. Or cubesats could descend toward the surface of Europa, the ocean moon of Jupiter.

“These spacecraft will allow us to act as the ‘Star Trek’ probes to go down to the surface of challenging worlds where we might not be able to take the risk of a much larger mission,” Klesh said.

When NASA’s next-generation rocket, the Space Launch System, heads for its first practice orbit around the moon (a launch that is facing delays), it will carry 13 cubesats, some as tests of technology and others as science experiments.

One cubesat, for example, will be tasked with mapping sources of water on the moon for future human exploration. Another, called NEA Scout, is being designed by Marinan to monitor nearby asteroids that could pose potential hazards to our planet.

Private companies are working on shrinking scientific instruments to be placed aboard the next generation of Earth-orbiting satellites. As instruments become smaller, the options for singular scientific missions in deep space become greater, as does the potential for whole fleets of MarCO-like satellites.

Toughening Tiny Travelers

But much work remains before more cubesats can travel beyond the moon. The challenges that come with operating full-size planetary missions apply to small satellites, too. If you want to go to the Jovian system, you need heavy radiation shielding. If you want to go to Saturn, you need more efficient solar panels and ways to keep the tiny spacecraft warm.

“We think we can actually send a small spacecraft all the way to Jupiter,” Baker said. “The problem is, I have to come up with a way of automating the onboard spacecraft so that it can fly itself to Jupiter or you only have to talk to it once a month. Or we create a way for it to only radio home when it needs help.”

These are the kinds of engineering challenges the MarCO team worked to overcome with the journey to Mars.

“It’s really opened a door of possibilities now that we have shown that this has actually worked,” Marinan said. “It’s not an impossible concept anymore.”

The engineers even managed to get around one of the tricker issues with how to collect data and talk to the cubesats. Typically, when a spacecraft calls home, it will spend several hours using NASA’s Deep Space Network, the very expensive phone system for calls beyond the moon.

But these long-distance conversations weren’t an option for the MarCOs. So the team at JPL created new ways of monitoring the spacecraft that allowed them to collect in a one-hour period the data that would usually take eight hours.

“MarCO is a herald of new things to come,” Klesh said. “Not necessarily better things, but different, and a new way of space exploration that will complement all the larger missions that we do.”

As it passed Mars, MarCO B returned the first photo ever taken from a cubesat in deep space. It revealed the copper-colored entirety of Mars in the dark of space, and a small section of the spacecraft’s antenna.

The angle of the photo was intentional — not only to show where we’ve been, but also to hint at where these tiny wanderers could go next.

This article originally appeared in <a id="a9720068-8ad7-48bf-ad6a-07ed2e7e4f57" href="https://www.nytimes.com/2019/03/18/science/cubesats-marco-mars.html">The New York Times</a>.

(Science Times)

Vast space with tiny explorers

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Shannon Stirone

Articles written by the author

Sailing Through Space on Solar Wind? LightSail 2 Will Try

LightSail 2 Unfurls Sails, Next Step Toward Space Travel on Solar Winds

SpaceX Falcon Heavy's 3rd launch -- how to watch

Vast space with tiny explorers