Solar sail test successful so far!

Originally published at:


Relishing the pure joy of such a thing existing.



You can contribute to the mission here:


the first spacecraft to orbit the Earth powered by sunlight

And all those dudes floating up there with solar panels just have them … for looks?


During launch LightSail 2 was enclosed within Prox-1, a small satellite built by Georgia Tech students.

Now that’s what I call project-based learning. Must be so cool for them to see. In college I wrote some ok Sociology papers…(and, TBF made some fun absurdist Flash games…)


I think interstellar travel is more of a long term project. From their website:

To give a specific example of solar sail speed, LightSail 2’s 32-square-meter sails accelerate it at just 0.058 mm/s². In one month of constant sunlight, the spacecraft’s speed would increase by a total of 549 kilometers per hour, roughly the speed of a jet airliner at cruising speed.

I leave it as a simple exercise to the reader to determine, when it will reach Earth’s escape velocity…


For certain values of “simple”, one presumes.

Having recently read just a bit about Buzz Aldrin’s substantial contributions to the development of practical orbital maneuvering and docking, I won’t be taking that bait.


Probably a good idea to boost it far enough away from earth that it doesn’t have to escape our gravity on its own.

I’m so glad to see this is out there and gaining speed. After the first one didn’t make it, I was worried we wouldn’t get another try.


I think the technology is awesome, but had a crazy thought that Armageddon wouldn’t have been anywhere near as butch (but 1000% more entertaining) if instead of Aerosmith, we had Christopher Cross…

…and instead of Bruce Willis, we had Alan Arkin’s captain from So I Married an Axe Murderer…

“Now that sounds like a lot of fun.”


6 years, 6 months, 20 days, approximately.


Bajorans beat us by about 400 years…


If you ignore a lot of little pesky details, about 23.6 months.

LightSail 2 started at an orbital height of 720 km, so its orbital velocity was approximately 7.49 km/s. (Courtesy of Casio Computer Co.'s calculator)

Escape velocity is approximately 11.1 km/s, and LightSail 2’s speed increase is 0.1525 km/s per month.

But in reality, the answer is “never.” Per the LightSail FAQ:

LightSail 2 will then begin swinging its solar sails into and away from the Sun’s rays as it circles the Earth, giving the spacecraft enough thrust to raise its orbit (technically, the orbit semi-major axis) by several hundred meters per day. This portion of the mission will last 1 month.

LightSail 2’s attitude control system does not have the precision to maintain a circular orbit. Therefore, as one side of the spacecraft’s orbit rises, the other side will dip lower, until atmospheric drag overcomes the forces of solar sailing, ending the primary mission. The spacecraft will remain in orbit up to a year before succumbing to destructive reentry.

Though LightSail 2 cannot raise its orbit indefinitely, this would be possible by angling the sail more precisely during each orbit.


Ow gawd. IDK if it’s the Gin & Tonic, the antibiotics, or both - but I misread the headline “Solar sail test successful, so fart”.

I am going to bed now. And might not come back soon, because of shame.


Those are for generating electricity, not for motive power - the power to make course changes.


Yes, “power” is the wrong word. Probably should have stuck with the source page’s text:

first spacecraft in Earth orbit propelled solely by sunlight


Wow, way to take something neat and just moan about the wording, you pedantic debbie downer. And, for the record, ‘powered’ is a perfectly cromulent English-language synonym for ‘propelled’.

I award you no points, and may god have mercy on your soul.


I don’t think it’s pedantry — this is a big distinction, and why solar sails are so interesting.

Getting power from the sun in space is easy. But turning that power into propulsion isn’t. Even ion thrusters need consumable fuel. And I wouldn’t hold my breath for anyone to prove the EmDrive works.


Only the meanest possible reading of TFA could conceivably confuse ‘powered the lights’ with ‘powered the wheels’.

Extra points for @DonatellaNobody and @johnawerner. And of course to Wolfram Alpha.

I think this is a great example how bad humans are with small and large numbers. Given an acceleration of 0.058 mm/sec^2, I would have guessed a much longer time. Then again 6 years before leaving earth is probably only useful for certain missions. The Apollo program could still be running today…

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“…with sails unfurled!”