Solar sails made out of extreme metamaterials, nanostructured and with some ceramics will be able to withstand over 1000 degrees celsius. They will reach slingshot within 2-5 solar radii of the sun, which is 2 to 4 times closer than the Parker solar probe. The solar sails should cost about $10 million per launch and have 50 kilograms of payload. It will be three times faster than the Voyager probe and could reach Jupiter in 5 months.
The project update was presented at the NASA NIAC 2020 virtual meeting.
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29 thoughts on “Extreme Solar Sails Will Slingshot Around the Sun to 0.1% of Lightspeed”
With regards to the infographics: They should have used a gallon of full fat milk instead of 0.5% fat milk. They would have gotten to 20% of light speed.
Oberth is special, altho the usu, case of orbit being changed most on the opposite of the firing, as the orbit has to return to the place of firing. Prove that, add that you want to get as far away as possible from the orbited body, and it is clear that firing close to the body is the way to do it.
I was thinking how do you make square miles sheets of this gossamer material, then furl and unfurl it. You might need between a thousand to ten thousand sq miles of this material to have a sail large enough to propel a usage payload.
I am thinking a large flat etched surface. You inject the different chemicals need to make the material. You then have to separate the material from the substrate. The material would have to be like Teflon in that it doesn't stick to anything including itself once its cured.
We should do some R&D on it since the material might have commercial uses.
Since he also mentions 3x the speed of voyager, I assume it should read 0.1% instead of 1%. That seems to work and is more realistic of such sail and payload mass being pushed only by the sun.
First, build the sail material and then we can talk.
So, back to the lightsail question. "Extreme Solar Sails Will Slingshot Around the Sun to 0.1% of Lightspeed" or, as Grav Lens Mission describes, spiral down by slowing, or, if sail good enuf, stop dead and drop, then unfurl and head straight on out! This seems extreme, and very extreme, lightsails. Still curious if they are using angle *tack* on sail in the first case, on the way out. ?? I'm more thinking of how sails work when their force is ~= Sun grav, to move stuff around cheaply and perhaps slowly. Humans will have mass drivers and roto thingys to get them going around, and top it off with laser driven sails, but humans are very tiny and light.
I'm not fresh on my math, altho could do competent stuff in the early 70s. "if you do a burn at perihelion, in addition to the speed you pick up
from the burn, you get to keep part of the speed you picked up falling
towards the Sun, because you spend less time at each G level on the way out than you did on the way in. That's it in a nutshell." Now, that makes sense. Don't hover your rocket, launch it! Gravity works over time, all the time, unlike a burn whether short or longer. This is what I call "just the standard orbit stuff", in that you can get more by burning at different places, different rates. It is also related to what I call the *tack* when grav is allowed to work longer for free, by slowing orbit speed to come closer to Sun for example, by grav. Oberth (Wiki version) not really relevant strategically for lightsails, as they max violate the recommendation that the burn be short! *but!* Also, if there is significant fuel mass, as chem rockets would have, would not that be a separate advantage as Wiki seems to say? Again, I am asking, not arguing. Seems that shedding the mass is better even than carrying it out faster. But this may be adding a name to a trivial concern. And, it is NOT the popularly known "slingshot"!
Well, that's Wikipedia for you; Written by a combination of experts in the field and glib, clueless people. It's not surprising to see a mistake or two.
They do give the mathematical derivation, and as you can see, no reference to mass in it. You don't have to throw anything overboard to profit from it.
You do get the most benefit from acceleration at the bottom of the orbit, though, so low acceleration propulsion like solar sails or ion drives don't benefit as much as chemical rockets, because their acceleration is spread out over less profitable parts of the orbit, rather than being an impulse at the best point.
You gain speed falling towards the Sun, you lose it climbing back. But, if you do a burn at perihelion, in addition to the speed you pick up from the burn, you get to keep part of the speed you picked up falling towards the Sun, because you spend less time at each G level on the way out than you did on the way in. That's it in a nutshell.
For a solar sail you also benefit from getting more acceleration the closer you are to the sun, but that's separate from the Oberth gain.
Blue Pizza was me, obviously; I'm having weird issues with this site saying I'm logged in, and then treating me as though I weren't when I post.
Thanks, that was a good clarification.
"own kinetic energy, which at speeds above a
few kilometres per second exceed the chemical component. When these
propellants are burned, some of this kinetic energy is transferred to
the rocket along with the chemical energy released by burning" How does this apply to light?
Changes in the mass of the vehicle have nothing to do with it. Seriously, you need to review the physics; That link the the Wikipedia page for the Oberth effect did get into it. The math isn't that complicated, it's just basic algebra and high school physics if you only use the impulse approximation. Heck, I derived these equations myself on a lark in Jr. high, with no more information than a description of the maneuver in an SF novel.
Notice that none of the math makes any reference to changes in mass?
The idea behind using some of the thrust to stay near the Sun is just that you can continue adding to your speed at perihelion. My I haven't done the math, but my expectation is that you'd just be better off adding as much speed as you could, instead of lowering your speed gain in an effort to maximize your period of higher thrust. You just wouldn't be able to hang around enough longer to make the lowered acceleration worth it. It's a solar sail, the trig works out so that any thrust component pushing you towards the Sun is going to be bought dearly in terms of lost thrust along your travel.
So, the new "Gravitational Lens" story has a totally different idea, just slow down and get close to Sun by grav/tack, orbit move as usual, then rely on extreme efficiency to just shoot straight away. Not trying to speed up orbit, just go straight away fast.
The question I have is then how this applies to light sails, where the *burn* has no effect on the mass of the craft. What you say is certainly true of chemical rockets. My phrasing would be for that, that the Sun grav pulls the fuel (reaction mass) in to max orbit speed, nearest, and then you dump it as exhaust before it slows going uphill, outwards. Lightsail just in orbit, will not have reaction mass to consider. Light pressure of course depends on distance. So, how is the *special* lunch being cooked? "using some of the thrust to stay down there longer" would in the *tack* theory be using grav to stay closer, while angling sail faster in orbit direction, rather than straight away from Sun, as sail angle, not actual path. I am not arguing, just asking and pondering. I also think lightsails are extremely cool.
Hope that image isn't supposed to be to scale.
No. Trust me, I used to do orbital mechanics calculations by hand for fun as a teen. (Yeah, big time nerd.)
The Oberth effect is actually due to kinetic energy being the square of velocity. By using the Sun's gravity to boost your speed when you make the burn, you get more kinetic energy from it than you otherwise would, and end up traveling faster once you've moved away from the Sun.
Think of it this way: Without the burn, you'd spend exactly as much time in the Sun's gravity approaching and leaving, and net out zero. But by speeding up close to the Sun, you spend less time subject to the Sun's gravity on your way out, and retain some of the speed you gained falling towards it. Mathematically the same thing.
The bottom line is, yes, you do gain from doing your burn as close to the bottom of a gravity well as you can, if you didn't start there anyway. I can't really say whether using some of the thrust to stay down there longer would be profitable, though. I kind of doubt it, though.
That relies on a similar thing as the rocket equation uses in a *bad* way, to have to have fuel carried to the speed of the rocket before burning. Not sure light works that way, but possible! Seems like the light will not care, unless you are already really moving. Usu "slingshot" means the standard gravity assist by passing a planet, in the sun's grav. So the (my) question is whether there is anything to *tacking* by staying close to the light, or is the force of the light better used at higher speeds, as fuel is, or both.
Not so! The Oberth effect has frequently been called a "slingshot", though it annoys the experts.
If the gravity of the Sun is the only operational gravity, you get no extra energy or speed interacting with it, just the standard orbit stuff.
His math is way off. At 1% of c, a spacecraft would cover 1000 AU in 1.6 years not 20 years. The spacecraft would be moving at 0.08% the speed of light or 12.6 times slower.
Still, it's not bad for $10 million or, even if it was $90 million overbudget, $100 million.
The classic gravity well maneuver works fine for the Sun, is also called a 'slingshot', and supplies at least a discount lunch.
No. But if you give your sail the opposite charge of the particles hitting the sail, you can effectivly double the force. Or, at least, that is what my physics professer said when we were discussing solar sails in his office 12 years ago.
I don't know if I was the first, but this idea of approaching the sun and then deploying a solar sail to get maximum acceleration to go to other solar systems was my idea. And I was bouncing it off him.
If it was good enough for the Enterprise to time travel, it’s good enough for this.
For the Sun's gravity lens missions, the farther you are the better it gets.
It starts becoming usable around 600 AU, from there and up to 1200AU it's several years of useful observations.
Short transit times are all well and good, but none of these fast "exploration" missions explain how they'll slow down at the target and actually, well, you know, explore.
Flying by at 0.01c is not exploration.
An ion thruster, constantly pushing it toward the sun will allow it to make many more orbits around it and closer, reaching a much faster speed. And as ion thruster become progressively more powerful, the slingshot solar sail speed will also increase. If you can position an E-sail to pull it toward the sun, that will be even more powerful.
And furthermore, this is clearly NOT the standard "slingshot" we get by passing a planet, as that is a three body effect requiring the Sun gravity being modified by the planet's. Here, only the Sun gravity is present, so central force field rules apply, no free lunch for you! Also, perhaps the thought should start with the Sun grav being the wind, and the light being the water/keel?
Well, not exactly like sailboat, in that the sunlight *is* like the wind, but clearly will always be faster than the craft. But sort of like tacking, in that the gravity holds the craft near the Sun for the sideways slingshot, for longer accel period in strong light than straight out would, in a quickly decreasing sunlight intensity. Of course, the sail is at an angle, for less accel but in a different direction, than straight out. A trade off certainly. That is why I said "Looks like", I am not certain if it helps, and certainly not certain of why, by some clear understanding of a *trick* factor!
But can you tack, and therefore go faster than the wind without a keel?
Looks like it *tacks* against solar grav to go faster forward in orbit, rather than straight away from Sun. More intense light for longer. Sailboats can go faster tacking than straight ahead of the wind.
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