How to Sail on Starlight 

10:11 Who's not excited for the upcoming Kepler Space Program!

It's pretty wild how old-school sailing is actually applicable in space.

never forget that count doku had this before it was cool

5:44: This is so 2019: a light-sail ubered to space using a Tesla to zoom around using a mass-less particle as its "energy" source, it's genuinely incredible.

A.C.Clarke wrote "Sunjammer," a short story about a race between solar sail spacecrafts, in 1964 :) (it was republished as "the wind from the sun" in 1972)

Need to understand orbital mechanics? I play KSP, I’ll be fine.

10:11 Oops, I'm sure you meant Kerbal Space Program.

In going to be doing aero/astronautics at uni with spacecraft engineering focus. Hopefully one day I'll be on the team for stuff like this.

CubeSail was going to be the first solar sail demonstration on a cubesat (back in December 2018), sadly it never made comms. Glad LightSail made it! -cubesail software lead

I was surprised at how interesting this video is, it surpassed my expectations! It is very informative about solar sailing, and amazingly well made! Thank you!!

If only it ran on toxic pedantry from YT comments, we'd be colonizing Saturn's moons.

As important as these topics are, what we really need is a video where you say Brilliant. Over and over. I swear each time I click on your vids, it’s crossed fingers, hoping they sponsored you on the video. Your accent is the best marketing they could’ve ever asked for. But love the vid too, 10/10

It’s great to see some serious work on solar sailing. And kudos on another brilliant video!

Did my bachelor thesis exactly on the topic of using a solar sail to move the L1 point closer to the sun. Turns out if you use a spacecraft with a reasonable amount of instruments to monitor the sun, the mass quickly becomes too large for a solar sail. To improve the warning time significantly you need to move L1 a lot closer to the sun (the fastest CMEs are traveling at 3000 km/s so you can do the math). You would need a solar sail with side lengths of 100+ meters, which obviously causes a lot of problems.

4:45 The angle of the force experienced by the sail is at right angles to the sail. The image shows the angle of the sail changing without the angle of the force following it.

I was waiting for this video from June!! Glad it's finally here!. Great job once again

Finally bit the bullet and got year on Brilliant thanks to real engineering. Enjoying it immensely so thanks for 20% off

The gravity exerted by the earth and sun are not the same at Lagrange point 1. If it were, the spacecraft would continue in a straight line instead of orbiting the sun. The earths gravity effectively cancels out just enough of the suns gravity so that the spacecraft orbits the sun slower than in normally would at that distance and instead keeps the same orbital period and relative position with the earth. Easy slip up in a great video. I love all your stuff!

99%: Kepler space program? 1%: random stuff 0%: very educational, love it, keep making more! Come on guys what is this? He spent a 11 minute video educating us and all you care is one second of the video where he accidentally says the wrong word....

Kepler space program?

I love tour chanel. In my school we dont care that much about space but ur chanel always stretches my mind and makes me want to pursue being an engineer

The advantage with ur vids is that i'm working my english and my science at the same time, keep it UP !

thats why you make it bigger, and unfold/unfurl the sail only at the point that it can get enough push to put it in a higher orbit or a hohmann orbit, then to be assisted by a radio or other array at the higher altitude on the dark side of the planet so the perigee gets raised.. middle material can be made out of a very rigid lightweight structure, possibly only when charged or when exposed to a particular type of light. outer material can be a film that can be under tension or expansion under a certain condition like how bimetal thermometers work. another layer outside that can be added to provide rigidity so the sail can be large and slightly curved to act as a reflector for astronomy, or to keep a large many km^2 sail from folding up like a broken umbrella. film relflectance tuning can make the sail so that forces and reflectance are evenly distributed with a central micro satellite weighing down the center. if you want to make some kilometer long arms to pull out the sail, supported by some guide wires to a mast on each side to get you started, go ahead. if its based off of photo-reactive expansion then it will crinkle up, reducing surface area and drag when not exposed to light. hardest part about this is the vapor deposition needed to make the thin film and the materials science for the film choice and structural elements.

Thank you so much for another stunning video. I only understand half of it but I absolutely love it. MORE MORE MORE

I saw you in fat Tony's a month or so ago. You were telling the barber about your channel and I was in the waiting area and remembered I was subbed to you. You got a pretty fresh trim to be fair

"...Or you can dispense with the useless analogies and think of it as a photon bouncing off a mirror..." Thanks so much I hate obfuscatory analogies

My first real engineering after starting engineering!!!

I remember reading a science fiction story many years ago about solar sailing. Photons for the win!

Thanks you brilliant for making this show possible

Thoughtful presentation. Well done.

In the March 1964 issue of ‘Boys Life’ magazine, Arthur C.Clarke’s story ‘The Sunjammer’ was the tale of futuristic spaceship pilot John Merton, his trusty ship Diana, and an epic space race of ten ‘sunjammers’; racing pods propelled by gigantic solar sails (the pods, big enough for one man, were tethered to the huge sails by gossamer thin lines, like gigantic parachutes). Deployed to catch the sun’s rays, the race was won by the first sunjammer to drift past the moon.

Seriously.... Kepler Space Program? Great video, I demand more!

Excellent episode, thank you!

i herd "ksp" and searched to find if they are making another ksp, and they are. WOOOOOOOOOOOOOO!

just a heads up L1 isn't where the earth and sun's gravity cancels out, it's where earth's gravity on the object cancels out enough of the sun's gravity such that the effective remaining gravity of the sun is the same as it is at earth's height. (giving your orbit the same periodicity).

Nice video!!! RESPECT!!! Real engineering please do a video about f-104.

Technological a great project to determine technological transmission for phones etc . perhaps, thank you for explanation.

Im pretty certain only a small portion of that light wavelength is being captured by the sail. Imagine being able to get the stronger shorter wavelengths. That is probably where the viability of this sail will be used. So just from the top of my head, I would try a lead lined sheet and see if that can stop even more of these smaller wavelengths. So just think of it as a net with smaller holes.

Great stuff! keep it coming.

Good day,Everybody i just want to say that i really enjoy watching these videos

"To control it's roll and stabilize its position. A huge moment that proved the viability of solar sails." -- I'm not sure if that was meant to be an engineering joke or not, but I found it hilarious

Always a pleasure to watch ur vids !

I'm hyped for Keplar Space Program!!!

If some of the photon's energy is transferred to the sail, does the reflected photon have a slightly longer wavelength?

Third year orbital mechanics class I took 3 years ago is actually helping me understand a youtube video Ha!

@realengineering Congrats on the 2M subscribers!

The solar sail technology was SUCCESSFULLY used for the mars orbiter mission conducted by the Indian space research organisation (ISRO) IN 2014

Dam , all of this is soo exciting !

Excellent work 👍

Just going to say there were some very good animations in this video I know how hard and time consuming they are and this video had textbook examples of a good animation

I'd be very interested in a video on how we could prepare or mitigate the effects of a large solar event! 2 hours doesn't seem like much time

Maybe this might be useful in terraforming Venus as an array of sunblockers. These would also be useful as signal boosters for communicating between Earth and Mars when they are on opposite sides of the Sun.

I’m more of a fan of the Keebler Space Program. Little elves solar-sailing cookies

It was just yesterday evening that I was curious and started a research about means of space traveling along with warp engines, ion thrusters, Nasa's NEXT project.... and now this video drops!

Another really cool application of solar sails is fast travel to the outer solar system, if you could make a sail thin enough so that the force of gravity from the sun equals the force of solar pressure, then any solar sail on an escape trajectory from the Earth would travel in a straight line (as gravity and light pressure both decrease by the inverse square law). This would allow you to reach somewhere like Saturn in just 1-2 years, as gravity wouldn't slow you down.

Love the Channel, Keep up the good work :)

If you have a sail that can hangout in one altitude above the sun it could do so in any other since gravity and intensity of sunlight both drop with the square of the distance.

Nice video and keep it up!!

Zubrin in the book "Exploring Space" shows a solar sail in a very close approach to the Sun could achieve a hyperbolic excess velocity approaching 1% light speed and experience 20 g acceleration. If I remember correctly beryllium was suggested as a possible material to handle the heating.

Astounding

I remember the movie AVATAR where the ship ISV venture star uses a solar sail to travel from Earth to Pandora. It was cool

This is great!

Cool, could a sail be large enough to be used on a crew sized craft? To help with acceleration to Mars or further, possibly used with ion thrusters, also, does PV panels work as a sail enough to contribute at all? Great video!!

Congrats on 2 million subs

Kepler Space Program, ofc, how could I forget XD for real tho, love your vids, don't stop being awesome

8:00 Mariner showed that sunlight can be used for orientation. Lightsail showed it can be used as thrust.

I like this video so much thank you

Baby steps, you gotta walk on sunshine before you can sail!

8:07 Takes place at Cal Poly San Luis Obispo (where I currently go)...Crazy!

I learned about this in middle school and I never thought anybody would ever do it

loved it

amazing video

I would love to see the mechanics of deployment. 💖😎

What about the debris in the space. Don't they damage the sails? Like piercing it and making tine holes which would reduce the total available area for the momentum transferring?

We can't really say the program was a waste, because we still learned that it's impractical to have a solar sail at that height.

Great vid.

So light is a solid!

When you showed a clip from the ksp2 trailer I half expected to hear, "This video is sponsored by Private Division"

Can you make a video about Silicon Carbide power devices and its uses in EVs and Industrial applications? It is one of the trending fields in power electronics right now. Would love to see you describe what SiC is capable of!

Thanks for using my song “Forgotten Years”! I watch your videos all the time :)

Can't wait for KSP2!!!

So if the early warning system sees a solar flare and sends up the message saying so. Wouldn't it's message get here the same time the solar flair does?

4:15 *cough* Snooker *cough*

I wonder if solar sail craft could get a boost by traveling along the gravitational focal lines where the light of distant stars would be concentrated by gravitational lensing.

Got to love momentum from 0kg "objects".

10:09 Smoothest fucking Ad read/transition in human history.

KSP 2 animation at 10:11, can't wait for it to release.

I appreciate that there is an equation that describes the quantity of momentum that light transfers to an object on reflection. However, I have not been able to locate a detailed description of the interaction between photons and atoms that explains the specific mechanism of that transfer. For example, does the photon interact with the electron shells, which then interact with the nucleus? Any guidance on this would be appreciated.

I have always wondered how you create your animations and drawings with the blue background. It looks so professional. Do you use some specific program or a program like photoshop?

One interesting thing about lightsail2, shadow of the earth have a con shape, so before reaching perige can catch some solar light and rise a little high of the orbit.

I want to visit *habitable exoplanets*

I learned the drawbacks of solar sailing in the hard way, while playing High Frontier.

This is actually cool.

Even Kepler uses solar wind pressure to to keep itself oriented.

Shouldn't the drag at perigee cause apogee to be lowered? That is sort of what I would expect from Kerbal Space Program

Debris is blocking the view do a barrel roll!

Solar sails are an option for interplanetary, or even beyond, exploration. _IF_ you can be patient enough for your instrument package to get to it's destination!

yes i have a decent understanding of orbital mechanics i play kerbal space program

greetings everyone. how ingenious the human mind is. success.

One thing I've never understood about the solar sail issue, and this could be because of ignorant enthusiasts overhyping the technology's capabilities. One substantial design requirement for anything to last in space long term is the ability to withstand high velocity impacts of very small objects. Even when you're not sitting in Low Earth Orbit, there's a fair bit of dust floating around out there - not a lot, but when a dust particle the side of the head of a pin can impact with several times the amount of energy delivered by most firearms, it doesn't take a lot to do some major damage. (As I recall the immediate assumption with the Apollo 13 explosion was such an impact and they ruled it out because there wasn't enough damage for it to be a fragment of dust, so it had to be an oxygen tank exploding...took me a bit to parse that oxygen tank explosions rate lower than dust impacts in space) Conversely, solar sails need to be quite large in surface area (increasing the odds of an impact with dust as well as the amount of collisions with photons), and quite light...which suggests that it probably lacks the required strength to withstand the impact of one of these dust particles. It strikes me that if you're using solar sails for anything ambitious enough for them to be a significant technology, like the examples given in this video, the odds of destruction by dust particle would be unacceptably high, rendering the phenomenon more an interesting curiosity that can occasionally be used for smaller scale solutions like the probe we sent to Venus and Mercury rather than the primary driving force of the vehicle. I'm probably missing something here, because minds much more knowledgeable about space exploration are putting time into developing this technology. Anyone know what I'm missing?