LightSail Aloft!

by Paul Gilster on May 21, 2015

One of the joys of science fiction is the ability to enter into conjectured worlds at will, tweaking parameters here and there to see what happens. I remember talking a few years ago to Jay Lake, a fine writer especially of short stories who died far too young in 2014. Jay commented that while it was indeed wonderful to move between imagined worlds as a reader, it was even more wondrous to do so as a writer. I’ve mostly written non-fiction in my career, but the few times I’ve done short stories, I’ve experienced a bit of this ‘world-building’ sense of possibility.

Even so, it’s always striking how science and technology keep moving in ways that defy our expectations. Take yesterday’s launch of The Planetary Society’s crowd-funded LightSail, which went aloft thanks to the efforts of a United Launch Alliance Atlas V from Cape Canaveral. LightSail violates expectations on a number of fronts. For one thing, the crowd-funding thing, which is a consequence of an Internet era that science fiction writers lustily engaged, but which enters homes on desktop computers that SF had trouble anticipating.

My old saying applies: It’s the business of the future to surprise us, even those of us who keep thinking about the future every day. Another LightSail surprise is its size. Many science fiction tales have covered solar sails dating back to the wondrous “The Lady Who Sailed the Soul,’ from Cordwainer Smith, and Arthur C. Clarke’s “The Wind from the Sun.” We’ve looked at a number of the early stories in these pages over the years. But imagined sails in those days were vast, just like Robert Forward’s gigantic designs, and I can’t think of anyone in those days who anticipated matching up sails with tiny satellites — CubeSats — which have brought space capabilities down from the level of government organizations to small university groups.


Image: The launch of LightSail aboard an Atlas V, as captured by remote camera on May 20. Credit: Navid Baraty / The Planetary Society.

So we have a CubeSat about the size of a loaf of bread that is about to deploy a sail measuring 32 square meters. CubeSats are cheap, and while they can’t mount missions of the complexity of a Juno or a Cassini, I can see a robust future for them. The beauty of The Planetary Society’s effort here is that while CubeSats can be readily orbited, they’ve had no real propulsion capabilities. Until now. So we’re not testing just one sail. We’re testing a broader concept.

Can we get a CubeSat to another planet? I can see no reason why not if it turns out that the solar sail strategy employed here does the job. And if we can get one CubeSat to another planet, we can surely get more. Thus the possibility of future missions designed around ‘swarms’ of CubeSat descendants, deployed on missions in which the components of a much larger spacecraft are effectively distributed among a host of carriers, all driven by solar photon momentum. Perhaps LightSail is the first step in making such a vision a reality.

Remember, too, that LightSail was launched as only one payload among many. Much media attention went into the launch of the X-37B, understandable because the small space plane has been operated with relative secrecy. But the Atlas V carrying LightSail also carried several other CubeSats into space. Contrast this with the early days of the space program, when each rocket lifted a single payload, and consider where miniaturization and improved design have begun to take us. With Mason Peck’s ‘sprites,’ we’re now exploring an even smaller realm some call ‘satellites on a chip,’ where the idea of swarm operations takes on a whole new luster.

We have about four weeks to wait before LightSail attempts deployment of its mylar sail. Even then the craft will quickly be pulled back into the Earth’s atmosphere, returning along the way images and data on spacecraft performance that will flow to the ground stations at Cal Poly San Luis Obispo and Georgia Tech (LightSail was designed by San Luis Obispo firm Stellar Exploration, Inc.) Data return has already begun. You’ll want to follow Jason Davis’ updates on The Planetary Society’s site as this story unfolds. LightSail’s first telemetry file can be downloaded — according to Jason, the early values appear to be ‘nominal or near predicted ranges.’ Here’s the one item that could be problematic:

The team’s only major concern is a line of telemetry showing the indicator switches for solar panel deployment have been triggered. (Look for line 77 in the telemetry file—the “f” is a hexidecimal value indicating all switches were released.) Under normal circumstances, the solar panels do not open until the sail deployment sequence starts, because the sails have a tendency to start billowing out of their storage cavities.

This telemetry reading, however, does not necessarily mean the panels are open. The switches were once inadvertantly triggered during vibration testing, so it’s possible they popped loose during the ride to orbit. We’ll know for sure after flight day four, when we test out the camera system. This is one time we don’t want to see a pretty picture of Earth—it would mean the panels are open.

I’ll be checking in with Jason’s blog frequently during the mission as we get closer to sail deployment. Meanwhile, be aware that the second iteration of LightSail is scheduled for a 2016 flight, this one a full demonstration of solar sailing in Earth orbit, with launch aboard a SpaceX Falcon Heavy to an orbit of about 720 kilometers. The KickStarter campaign supporting the LightSail project can be accessed here. The level of support that has emerged is encouraging indeed, as success with LightSail will energize the entire community of sail researchers.


J. Jason Wentworth May 21, 2015 at 10:46

Let’s hope this is like John Glenn’s landing bag and Apollo 4’s stuck S-IVB vent valve–telemetry errors rather than hardware failures. Also:

Since the plans for the Cosmos-1 solar sail (which unfortunately never reached orbit) included beaming microwaves at it from ground stations in order to see if maser sailing might work for future vehicles, are there any such plans for this first LightSail vehicle? If it produces significant thrust, it could lower the minimum altitude (due to atmospheric drag) at which a solar sail could operate in Earth orbit, which would give solar sails more flexible launch options.

ljk May 21, 2015 at 11:13

A mini demo lightsail and a top secret robot spyplane all in one launch. How Hollywood! :^)

Here is the history of sailing on light:

James Stilwell May 21, 2015 at 14:12

Glad to have the latest info…
Little things may mean a lot…

Ashley Baldwin May 21, 2015 at 15:30

Funny how momentous times pass by without there significance being relapse by many. Cube sats and light sails. Definite major advances with a big future ahead of them. Especially nearer the sun . In future bigger still sails can be constructed by punching out thousands of tiny holes with a diameter less than the wavelength of the solar wind in order to save on mass and thus create a larger , lighter sail with greater effectiveness and room for a larger payload too.

Alex Tolley May 21, 2015 at 19:17

It is amazing what can be done with cubesats today, and imagine what could be possible soon. For example Planet Labs Earth observing have a 5m resolution, compared to the HIRISE telescope on the Mars Reconnaissance Orbiter wit a0.3m resolution, yet vastly less costly. Small solar sails as well as other propulsion methods will now give then the ability to probe other planets and moons. The small scale should allow interesting design experiments at a very affordable price, allowing for a flowering of development ideas. Imagine a fleet of sail propelled cubesats doing observations of planets, moons, asteroids and comets, at very low cost. We wouldn’t be able to keep up with the observations and data streaming in. It would be several new interesting things every day. Or what about launching them from the big mission probes, either at the target body or even on their way?

Would it be possible to arrange a sail race for cubesats in the spirit of Clarke’s {“The Wind from the Sun” (aka Sunjammer)? Perhaps by the 60th anniversary of the story in 2024.

J. Jason Wentworth May 21, 2015 at 22:54

Melikes Alex Tolley’s solar sail race idea! It could be conducted as a publicity/sport, engineering test, and scientific data-gathering event, all in one. CubeSat spacecraft “buses” (especially the 3U type) would enable all of the major solar sail types (square “kite,” heliogyro, and disc sail) to be tested cheaply, to iron out any ‘bugs’ and to gain experience with controlling, maneuvering, and navigating them. After the race (say, past the Moon or one of its Lagrangian points), some or all of the sailcraft could be used to fly by NEOs and/or main belt asteroids, to assay their resource contents. Also:

The “variable albedo” LCD panels (which JAXA’s spin-rigidized IKAROS solar sail uses for attitude control and maneuvering) could also be used in other low-mass, high-performance, spinning sailcraft such as the heliogyro and the disc sail. Such a heliogyro wouldn’t need the cyclic pitch control system of the classic heliogyro design (just the collective pitch system, which is simpler than the cyclic pitch one and puts less twisting stress on the sail blades), and this would lower the required sail blade mass (and thus the vehicle’s mass). A disc sail equipped with the “variable albedo” LCD panels wouldn’t need cold gas jets, torque vanes, or a complicated “sliding payload” system to offset its center of mass for making maneuvers, as did the classic disc sail designs.

Michael May 22, 2015 at 1:20

@Ashley Baldwin May 21, 2015 at 15:30

‘In future bigger still sails can be constructed by punching out thousands of tiny holes with a diameter less than the wavelength of the solar wind in order to save on mass and thus create a larger..’

You mean wavelength of light, there is not a lot of solar wind compared to the amount of light~10000 less. And you are right holes around the wavelength of light can be punched through with nothing more than an electron or reactive ion gun and very, very fast to. Imagine a solar sail deployed edge on the sun and then raked with these beams to remove the excess material, once the material is removed the sail can be rotated, perhaps with the momentum of the adjusted beam to face the sun. But it might be better if be given a final spray of radioactive materials and be used as a fission fragment sail instead.

ljk May 22, 2015 at 9:46

24 hours after launch all systems are nominal (that’s a good thing):

ljk May 26, 2015 at 15:45

I just found this news item on LightSail:

Nothing yet from TPS on their various sites. I would think they would ask for help in tracking their satellite. It is a prototype after all.

Chris Marshall May 26, 2015 at 20:00

Latest update from Planetary Society, they believe that the spacecraft has suffered a software glitch and is currently frozen, they have sent multiple reboot commands to the vehicle without success and may need to wait for the spacecraft to reboot itself, unfortunately they don’t know when that will happen because it is triggered by a charged particle hitting the vehicle.

If they are able to re-establish contact they will most likely deploy the sail manually.

ljk May 27, 2015 at 8:27

Bill Nye & The Planetary Society Issue LightSail™ Test Mission Update
Solar Sail Spacecraft Silenced, Software Glitch Suspected, Team Awaits Reboot

Erin Greeson
Phone: +1-626-793-5100

Pasadena, Ca. (May 26, 2015) – After a successful launch into orbit aboard a United Launch Alliance Atlas V rocket out of Cape Canaveral, The Planetary Society’s LightSail™ spacecraft went silent after two days of communications. The solar sailing spacecraft test mission, a precursor to a 2016 mission, has been paused while engineers explore a suspected software glitch that is believed to have affected communications.

A reboot is necessary to continue the mission. Upon reboot, the LightSail team may initiate manual deployment of the spacecraft’s Mylar® solar sails. Bill Nye (The Science Guy), CEO at The Planetary Society, issued the following statement:

“A problem like this teaches you more about your spacecraft than a mission that’s trouble-free. This is our test flight, and we have a healthy spacecraft in a stable orbit. Soon, we expect our little LightSail to reboot on its own, and we can get down to business up there. After 39 years, I can hang in for a few more weeks.”

For in-depth coverage of LightSail’s test and 2016 missions, follow embedded reporter, Jason Davis at

ljk May 27, 2015 at 8:29

Far more details here:

So they are waiting for LightSail to reboot on its own. Is it designed to do that? Or are they hoping for a miracle?

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