LightSail 2 Spacecraft Successfully Demonstrates Flight By Light (planetary.org) 87
According to The Planetary Society, LightSail 2 has successfully raised its orbit using solar sailing, making it the first small spacecraft to demonstrate the concept. From the report: Since unfurling the spacecraft's silver solar sail last week, mission managers have been optimizing the way the spacecraft orients itself during solar sailing. After a few tweaks, LightSail 2 began raising its orbit around the Earth. In the past 4 days, the spacecraft has raised its orbital high point, or apogee, by about 2 kilometers. The perigee, or low point of its orbit, has dropped by a similar amount, which is consistent with pre-flight expectations for the effects of atmospheric drag on the spacecraft. The mission team has confirmed the apogee increase can only be attributed to solar sailing, meaning LightSail 2 has successfully completed its primary goal of demonstrating flight by light for CubeSats.
The milestone makes LightSail 2 the first spacecraft to use solar sailing for propulsion in Earth orbit, the first small spacecraft to demonstrate solar sailing, and just the second-ever solar sail spacecraft to successfully fly, following Japan's IKAROS, which launched in 2010. LightSail 2 is also the first crowdfunded spacecraft to successfully demonstrate a new form of propulsion. The mission team will continue raising LightSail 2's orbit for roughly a month, until the perigee decreases to the point where atmospheric drag overcomes the thrust from solar sailing. During the orbit-raising period, the team will continue optimizing the performance of the solar sail.
The milestone makes LightSail 2 the first spacecraft to use solar sailing for propulsion in Earth orbit, the first small spacecraft to demonstrate solar sailing, and just the second-ever solar sail spacecraft to successfully fly, following Japan's IKAROS, which launched in 2010. LightSail 2 is also the first crowdfunded spacecraft to successfully demonstrate a new form of propulsion. The mission team will continue raising LightSail 2's orbit for roughly a month, until the perigee decreases to the point where atmospheric drag overcomes the thrust from solar sailing. During the orbit-raising period, the team will continue optimizing the performance of the solar sail.
Sail and atmospheric drag... (Score:2)
The mission team will continue raising LightSail 2's orbit for roughly a month, until the perigee decreases to the point where atmospheric drag overcomes the thrust from solar sailing.
It shouldn't take too much atmosphere for the atmospheric drag to come into action if the sail remains deployed or, do they fold it in at every pass? Folding/de-folding at every pass seems unlikely to me.
https://en.wikipedia.org/wiki/... [wikipedia.org]
To achieve its final "solar sailing" configuration, LightSail extends four 4-meter cobalt alloy booms that slowly spread open the mylar sail material.
Re: Sail and atmospheric drag... (Score:5, Insightful)
How dense do you think space is? We sent a spacecraft through the asteroid belt, and were lucky to see one single asteroid as a dot.
Re: Sail and atmospheric drag... (Score:4, Insightful)
On top of that, solar sails doesn't stop working just because some micrometeorite blasted through it.
The loss in surface area would be insignificant.
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How dense do you think space is? We sent a spacecraft through the asteroid belt, and were lucky to see one single asteroid as a dot.
Agreed. I don't think our asteroid field is like what you see in Star Wars.
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True. Ours doesn't have any potatoes in it.
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Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space.
- Douglas Adams, The Hitchhiker's Guide to the Galaxy
Even on earth, for Pilots, if an airplane cross path with an other that is a mile away, It could be considered a near miss. Having been a passenger on a small Cessna, I had to keep my eyes open and point out to the pilot if I see any airplanes no matter how sm
Re: Sail and atmospheric drag... (Score:1)
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If we are talking Billions of years, and a Huge target, like the Moon (yes, the moon is HUGE compared to anything the Humans on the third rock have built), then yes, there will be many hundreds of hits, but if a mission is planned for 30 years, on something the size of say, the block your domicile is on, then, it becomes many thousands of times less likely.
Just as the two Voyagers passed out to interstellar space
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"How do these things dodge asteroids and stray matter in space if we use these for deep space explorations?"
Who cares? We'll send hundreds.
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Couldn't you rotate the sail so it acts as a wing and boost at apogee to keep the orbit from decaying? Eventually you could achieve escape velocity and go into a heliocentric orbit. This could be useful for interplanetary repeater satellites to get around obstructions.
Re:Sail and atmospheric drag... (Score:5, Informative)
That's exactly what they do, using the momentum wheel to change it's attitude so the sail is only used when it can get the benefit of those photons.
The downside is that although the apogee is risen from 725km to 727km, the perigee has been lowered from 710km to 707km.
This is the reason that the mission duration is just about 1 month. This is the first week & it's proved it, the rest of August will be to see how far they can go. After that it will then begin to deorbit which will last about a year.
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we know it is you all along trying to grab as much attention as you can like you always do!
Is that why you lot constantly pile attention on him and never shut up about the guy like he's the fucking center of you entire existence? Jesus, I dunno what he did to you but get over it. It's getting pathetic now.
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Couldn't you rotate the sail so it acts as a wing and boost at apogee to keep the orbit from decaying?
How is a wing going to help when you have nothing to generate lift from?
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"It shouldn't take too much atmosphere for the atmospheric drag to come into action if the sail remains deployed or, do they fold it in at every pass? Folding/de-folding at every pass seems unlikely to me."
Sailors have been tacking for centuries.
And now only to send a roadster to Mars (Score:2, Funny)
Re:And now only to send a roadster to Mars (Score:5, Interesting)
I've long been an advocate of using solar mirrors to collect and focus solar radiation to Earth for power, and of solar sails to collect icy asteroids or icy ring material from Jupiter to harvest for water and metals in Earth orbit. It should be much safer and is potentially more economical than Lunar harvesting or shipping water and material to orbit for space stations and spacecraft.
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That sounds like a great way to prolong global warming. The problem with global warming isn't the greenhouse gasses per se, it's that the carbon is causing Earth's atmosphere to retain more heat. The problem with space-based solar power is that it increases the amount of energy the Earth is receiving from the sun. Eventually, that extra energy *will* find its way into the environment, because of thermodynamics. You might end up with less greenhouse gasses emitted with SBSP, but now you're warming up the pla
Science fiction (Score:2)
I've long been an advocate of using solar mirrors to collect and focus solar radiation to Earth for power, and of solar sails to collect icy asteroids or icy ring material from Jupiter to harvest for water and metals in Earth orbit.
How about warp drives powered by unicorn farts? You are talking science fiction. How about we worry about figuring out what solar sails can actually do in reality before we go running off to Jupiter for some ill defined scheme to mine who knows what for undetermined purposes requiring technology we don't have for a space economy that doesn't exist.
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It's hardly "warp drive". It's a matter of scaling up tested engineering, not inventing new physics for utter science fiction. It's also likely to be a far smaller investment, with well defined benefits, than a Lunar base that has to produce water, and aluminum.
Hope (Score:1)
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It's theoretically possible, though expensive. Simply replacing fossil fuel sources with solar power beamed from solar mirrors could be very helpful.
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Most designs reflect the power to a microwave transmitter, which can then beam microwaves to a large scale ground array. The approach is described in numerous NASA papers, and in the "Fallen Angels" storay by Larry Niven and Jerry Pournelle. I admit that I left out mentioning that part as adding complexity to the explanation.
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Now let's make those solar sails reflective and able to block some sunlight from entering the atmosphere. We could actually provide a lot of cooling if solar mirrors are put in place.
How many of these things do you want up there? To block/reflect any appreciable amount you are going to need A LOT of area.
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Slow down (Score:3)
Now let's make those solar sails reflective and able to block some sunlight from entering the atmosphere. We could actually provide a lot of cooling if solar mirrors are put in place.
Oh yes let's put a bunch of space junk into orbit to block sunlight without any clear idea what the actual results would be or what specific problem it would solve. That sounds like a great idea. #sarcasm
You engineer the world climate at our collective peril. We only have one Earth and if we get it wrong we are fucked. Let's not get too excited about geo-engineering our entire planet before we really know WTF we are doing. We're already doing enough damage as it is thanks to our technology exceeding o
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Oh yes let's put a bunch of space junk into orbit to block sunlight without any clear idea what the actual results would be or what specific problem it would solve. That sounds like a great idea. #sarcasm
True, but if things actually do get undeniably bad and look to get worse real quick, launching solar shades would be a rather straight forward engineering solution that wouldn't require the fight to get people/countries to change their life styles (get off oil and coal). Even then, the point which things could changed by lifestyle changes would probably be gone since the lag between entering CO2 and max heat retention due to it is many years*. Many thousands of square kilometers of shade could be placed in
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How long until it gets to Coal Sack? (Score:3)
And Murcheson's Eye?
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2450 Jasper Murcheson explores the region beyond the Coal Sack
2862 Coherent light from the Mote reaches New Scotland
If they're raising it's orbit (Score:2)
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Unlike Kerbin, Earth's atmosphere doesn't have a sharp cutoff where drag drops to 0. At 50 miles/80 km perigee, you're "in space" in the sense that atmospheric drag is low enough that lightweight station keeping thrusters can keep your satellite up, but there's still non-trivial drag. Even at 200 km a satellite won't stay up very long without a little boost now and then, but you're starting to get to where thrusters are more for dodging debris than boosting against drag.
Unless this solar sail can increase
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The perigee initially was 710 km, and has decreased to 707 km. I'm surprised the atmosphere has enough density at that height to accomplish that.
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Looking at their graph of their orbit over time, it seems like they're just getting most of their thrust far away from perigee, and so they're lowering perigee by about the same amount they're raising apogee.
Practically, that doesn't accomplish much. It does demonstrate that they're actually getting thrust from the solar sail, no doubt about that, but thus far not enough to be very useful. You need enough thrust in the relatively small window near perigee to accomplish something.
Still, it's a step. Hopefu
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> Practically, that doesn't accomplish much. It does demonstrate that they're actually getting thrust from the solar sail
It seems valuable, to me, to work out solar sail mechanics in orbit, where tracking and telemetry are rather easy.
Perfect it here, then send one proven-reliable craft out to the planets or the stars with confidence.
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Yes, you've just described the difference between "research" and "practical". Hopefully the one leads to the other.
Re:If they're raising it's orbit (Score:5, Interesting)
The perigee initially was 710 km, and has decreased to 707 km. I'm surprised the atmosphere has enough density at that height to accomplish that.
The thing about orbits is in where you input the energy. I suspect the perigree is along the side of the planet that they are boosting the energy with the sun behind the vector the craft is following. This will raise the orbit on the apogee side (in this case the side where the craft is heading toward the sun). But the rub is that when heading toward the sun, they are turning the sail to the side to reduce the effect of the sun yet not eliminating it. This means some thrust is being applied against the vector and is assisting the drag to lower the perigree. I think *both* effects are showing that the lightsail is effective.
The next challenge is how to use a craft with a lightsail to boost the whole orbit. Charged ionic particles are sticky. Turning the sail to sort of tack doesn't work like we want. The particles hit, transfer momentum in a vector directly away from the sun, bounce a small bit as they are drastically slowed from the collision and apply a tiny amount of force against the vector they were directed to(this part is actually similar in many ways to wind). On a sailing vessel we use a neat trick called a keel to apply a lifting body under a dense fluid and convert the force the wind applied into a drag against the dense fluid and that is what lets us vector the force in the direction we want.
Lightsails are waiting for space keels to be invented.
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Why deorbit instead of just heading out? (Score:2)
Does anyone know why they don't just try to sail out of earth's gravity well? It would surely take a very very long time, but since the sail doesn't use fuel...
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No, you can't just keep raising orbit to escape. I probably won't do a great job explaining this but I will give it a try. If you don't "get it" after this the problem is probably my explanation.
When Lightsail raises its orbit it actually slows down. Orbital mechanics aren't the most intuitive thing in the world. However as the orbit gets higher and the orbital velocity lowers the escape velocity lowers. Remember, it's still 1.4x your current velocity, so if you orbital speed drops from 7402m/s to 7400
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Getting out of Earth's gravity well is going to require hitting escape velocity which is always 1.4x (square root of 2 to be exact) your current orbital velocity. For this cubesat the orbital velocity is probably around 7500m/s (figure 7200-7600 is the range, not sure what it's altitude is) so you need to kick your velocity up to around 10,500m/s to get out.
That, uh... not happening with solar power.
To deorbit it you just wait for the little bit of atmosphere out there to slow it down enough to bring it ba
Losing orbital energy is a success? (Score:5, Informative)
Re:Losing orbital energy is a success? (Score:5, Interesting)
I'd call it a successful demonstration. They raised apogee just with solar pressure; that's all they really wanted to show. If they were able to kick the thing out into an orbit far enough away from Earth that the atmospheric drag wasn't overcoming the total energy produced by the solar sale then they could stay up indefinitely, or at least as long as the cubesat still functioned.
But getting that far into orbit is expensive, and they had to piggy back on other experiments just to get where they ended up.
I can't help but wonder if this would be useful for cubesats in lunar orbit. There's no atmospheric drag there (or at least much much less than near Earth) and the sucker is "lumpy" mass-wise so things don't like to stay in orbit there. A little solar boost might solve that problem. Maybe. I'm sure people smarter than me have tried working through it.
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Full disclosure/virtue signalling. I donate a little money (employer match!) to the Planetary Society in support of projects like this. I like the fact that there is an org that will pursue some basic, applied, science that hasn't been fully fleshed out by the national space administrations. Japan has done little solar sail work, the US has, and the Planetary Society is adding to this knowledge and experience.
I would love to see them try and pursue some of the laser propulsion type experiments as wel
Re:Losing orbital energy is a success? (Score:5, Informative)
Drag alone can not raise the apogee, only lower it since the force is always in the retrograde direction. The raised apogee is proof that the solar sail has produced thrust even if the total orbital energy has decreased. It means the sail works even if it is not enough to make the craft stay afloat. The test will probably give them lots of data which they can use to verify the sail works according to calculations or perhaps find unexpected side effects. Since reality doesn't have a quick-save/load button it is common practice to build small scale test vehicles before building the real thing.
As long as the sail works, atmospheric drag can be reduced by just putting the craft on a bigger rocket and sending it into a higher starting orbit.
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Thanks for the math: that makes a lot of sense. But I think they didn't prove much if they have a net energy loss. Why didn't they position the thing to increase orbital speed, thus moving the entire orbit further out? THAT would be the real proof.
the post is a little light (Score:2)
(get it?) ...but seriously, I'm curious how well its performed according to theory and where they have explainable variations or unexplainable variations.
Expanding Universe (Score:2)