Solar Sails Could Guide Interplanetary Travel, Says New Study (phys.org) 47
A team of scientists led by Slava Turyshev of the Jet Propulsion Laboratory at the California Institute of Technology have proposed merging miniature satellite units with a solar energy process that would create a fast, inexpensive, lightweight mode of travel. Phys.Org reports: Solar sailing is a process by which the pressure generated by the sun's radiation is harnessed for propulsion. Recent innovations in this technology were demonstrated in a successful crowdfunded 2019 mission undertaken by the Planetary Society's LightSail-2 project. The researchers explain, "Solar sails obtain thrust by using highly reflective, lightweight materials that reflect sunlight to propel a spacecraft while in space. The continuous photon pressure from the sun provides thrust, eliminating the need for heavy, expendable propellants employed by conventional on-board chemical and electric propulsion systems, which limit mission lifetime and observation locations."
They say that sails are far less expensive than heavy equipment currently used for propulsion, and that the ever-present continuous solar photon pressure from the sun makes thrust available for a broad range of vehicular maneuvers, such as hovering or rapid orbital plane changes. Solar sails and miniaturization "have advanced in the past decade to the point where they may enable inspiring and affordable missions to reach farther and faster, deep into the outer regions of our solar system," the report says.
The researchers refer to the merging of these two technologies as the Sundiver Concept. "Fast, cost-effective and maneuverable sailcraft that may travel outside the ecliptic plane open new opportunities for affordable solar system exploration," the report states, "with great promise for heliophysics, planetary science, and astrophysics." With enhanced maneuverability, the spacecraft can easily deliver small payloads to multiple destinations if required, and can dock with related modular craft. The reliance on the sun and the miniaturization of the carrier, which requires no dedicated launch site, will prove to be significant cost savers, the researchers add: "A substantial reason for the high costs is our [current] reliance on slow and expensive chemical propulsion, operating at the limits of its capabilities, effectively rendering the current solar system exploration paradigm unsustainable. A new approach is needed."
They say that sails are far less expensive than heavy equipment currently used for propulsion, and that the ever-present continuous solar photon pressure from the sun makes thrust available for a broad range of vehicular maneuvers, such as hovering or rapid orbital plane changes. Solar sails and miniaturization "have advanced in the past decade to the point where they may enable inspiring and affordable missions to reach farther and faster, deep into the outer regions of our solar system," the report says.
The researchers refer to the merging of these two technologies as the Sundiver Concept. "Fast, cost-effective and maneuverable sailcraft that may travel outside the ecliptic plane open new opportunities for affordable solar system exploration," the report states, "with great promise for heliophysics, planetary science, and astrophysics." With enhanced maneuverability, the spacecraft can easily deliver small payloads to multiple destinations if required, and can dock with related modular craft. The reliance on the sun and the miniaturization of the carrier, which requires no dedicated launch site, will prove to be significant cost savers, the researchers add: "A substantial reason for the high costs is our [current] reliance on slow and expensive chemical propulsion, operating at the limits of its capabilities, effectively rendering the current solar system exploration paradigm unsustainable. A new approach is needed."
Nothing new... (Score:5, Informative)
The Sci-Fi Spanish writer "Coronel Ignotus" (pseudonim of Jose de Elola, an military and part of the Spanish regime at his time) wrote in 1918 such a thing in this first novel of this genre: "De los Andes al cielo" (From the Andes to the Sky).
You can read the 3rd edition from the copy at the Universidad Complutense of Madrid for free:
https://eprints.ucm.es/id/epri... [eprints.ucm.es]
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You can also read Arthur C. Clarke's 1972 short story The Wind from the Sun [baen.com] for free at Baen Books.
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You can read the 3rd edition from the copy at the Universidad Complutense of Madrid for free:
Well, I could if I could read Spanish.
There's also a Star Trek: DS9 episode called Explorers [fandom.com]. Although it's a human making the run, he's reenacting an ancient Bajoran trip from Bajor to Cardassia, to prove it could've happened.
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that's just racist.
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he's reenacting an ancient Bajoran trip from Bajor to Cardassia, to prove it could've happened.
Except it couldn't have happened. Not with solar sails. Bajor and Cardassia are in different star systems that are several light-years apart. It would take centuries and have to be a generation ship.
Look, solar sails may be viable for going from Earth to Mars or Venus, but not to another star system. That is implausible.
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They use classic Star Trek space magic to explain it:
When the ship flies into a "tachyon eddy", it is accelerated to warp speeds
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Except it couldn't have happened. Not with solar sails. Bajor and Cardassia are in different star systems that are several light-years apart. It would take centuries and have to be a generation ship.
Look, solar sails may be viable for going from Earth to Mars or Venus, but not to another star system. That is implausible.
Yeah, I covered that in a previous post [slashdot.org], although not about ST:DS9.
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Look, solar sails may be viable for going from Earth to Mars or Venus, but not to another star system. That is implausible.
Except that it is not. And most likely the only way anyway.
If you get s probe to 1% light speed it only needs 400 yeas to Alpha Centauri.
Faster is possible.
And thee are laser assisted ideas.
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ÂPor qué no puedes entender español? Es el segundo idioma mÃs comÃn en los Estados Unidos, la nacionalidad mÃs comÃn aquÃ. Yo hablo un poco de español y se trata de la décima lengua mÃs comÃn utilizada en mi paÃs.
I think I'll go and get that version mentioned - I need to practice my Spanish, and this seems a damned good way to do it.
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Quote: "Well, I could if I could read Spanish."
I encourage you to learn Spanish. Why? It's the second native language in the world (after Chinese), but it's widespread all around the globe (not like Chinese, which more than 90% of native speakers are from mainland China...)
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Let us not forget the rollicking adventures in Revenger by Alistair Reynolds [alastairreynolds.com], with pirate ships using solar sails.
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tacking (Score:2)
Is it really sailing?
I get the basic nature of using a sheet to catch photons and let light pressure push one away from a stellar primary.
But as far as I can tell, there's a single vector there, and you use it or you don't.
Unlike actual sailing where an airfoil effect allows sailing vessels to sail upwind...as close as 35 degrees from the source.
I don't believe that is in any way possible with solar "sailing" meaning it's of pretty limited utility.
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Some suggest that tacking is possible [solarsails.info] to push an objected into a closer orbit with the sun but it is still unproven with no certainty whether it would work while already in orbit around other bodies where gravitational forces become significant enough to be another vector.
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To get to Venus from Earth, you could use a solar sail to move away, and then slingshot off Mars or Jupiter using a gravity assist.
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That would definitely be cool to see, a lot of technical challenges in ensuring a correct approach vector to not end up stuck in an orbit around the assist body or flung off in the wrong direction but then they have done that a ton of times using propellant based propulsion so it wouldn't be entirely new.
Maybe solar sail for primary propulsion with secondary propellant based system for correction? Wouldn't have to be as heavy as a primarily propellant based setup.
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Yes, I said that.
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You forget about gravitational force.
Re:tacking (Score:5, Informative)
But as far as I can tell, there's a single vector there, and you use it or you don't. Unlike actual sailing where an airfoil effect allows sailing vessels to sail upwind...as close as 35 degrees from the source.
For centuries boats couldn’t tack upwind worth crap because they focused on the sail alone and suffered from this same issue. Then someone invented a diode for motion that resisted side to side motion but did not resist forward or backward motion, simply a fixed rudder under the boat. This allowed the physics of upwind tacking to the point a windsurfer (low mass, large surface areas) can actually sail almost directly into the wind.
You might think there is nothing to push off of, but there is actually a magnetic field pretty much everywhere in our solar system and around plasma it’s even stronger. Superconducting magnets are easy to cool in most of the solar system, and once charged to the desired value, will keep exerting a force with essentially no losses. Using both a solar sail and magnet sail allows for pushing from two vectors that typically won’t point in the same direction and thus allows for far more freedom of movement.
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This allowed the physics of upwind tacking to the point a windsurfer (low mass, large surface areas) can actually sail almost directly into the wind.
Huh? Windsurfers can't point particularly high. Not even long boards with daggerboards can get closer than about 45 degrees TWA, and that's only when everything is ideal I mean, you're certainly right about sailing tech and the importance of a good keel; racing monohulls can sometimes get as high as 35 degrees TWA. Of course, when you're on the boat it feels a lot closer to the wind than that, apparent wind angle on a well-trimmed racing monohull can get as high as 10 degrees. But the truth of the matter i
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Huh? Windsurfers can't point particularly high. Not even long boards with daggerboards can get closer than about 45 degrees
No, it’s much tighter, around 10 degrees on the boards I’ve sailed. Further, there is a limit beyond which it’s impractical because you can make upwind headway faster on a broader reach but that’s not the same as not being able to head up wind.
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No, it’s much tighter, around 10 degrees on the boards I’ve sailed.
10 degrees apparent wind, maybe. True wind? Not a chance.
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The difference is that an airfoil produces both a drag force(parallel to the air flow) and a lift force (normal to the airfoil), in addition to the drag force of the keel(normal to the orientation of the keel), while the solar sail only produces the drag component.
While the wind direction is fixed, the airfoil and the ship can be rotated relative to it to produce a variety of net force directions. With a solar sail the direction of the incident radiation and the magnetic field are not free, you can only cha
Re:tacking (Score:5, Informative)
It can't go "upwind", but it can go + or - 89 degrees to the incoming radiation at some level of thrust. That's usually ok.
Sailing directly toward a star isn't usually necessary in space. Orbital mechanics aren't exactly intuitive here, but I'll try. If I wanted to move toward the sun I wouldn't go directly towards it. That would give me an egg-shaped orbit with my apohelion on the far side moving far away from the sun. To orbit closer to the sun, first I get into solar orbit, then use the sail to generate thrust backwards to reduce my current velocity. That would bring my perihelion on the far side of the sun closer.
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It can't go "upwind", but it can go + or - 89 degrees to the incoming radiation at some level of thrust. That's usually ok. Sailing directly toward a star isn't usually necessary in space. Orbital mechanics aren't exactly intuitive here, but I'll try. If I wanted to move toward the sun I wouldn't go directly towards it. That would give me an egg-shaped orbit with my apohelion on the far side moving far away from the sun. To orbit closer to the sun, first I get into solar orbit, then use the sail to generate thrust backwards to reduce my current velocity. That would bring my perihelion on the far side of the sun closer.
Given the lack of anything comparable to a keel, it seems like your thrust vector is always going to be perpendicular to the angle of incidence of the photon flux against the sail. By orienting the sail almost parallel to the flux you orient your thrust almost parallel to your orbital velocity vector, but you're still going to be thrusting not only retrograde but also radially out. The retrograde thrust will lower your perihelion, but the radial thrust will cause your perihelion to precess at the same time.
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You're not "catching" photons, you're reflecting them, and you can (and generally will) do so at an angle. It's not an airfoil, but the momentum transfer is reasonably similar to sailing. Combined with orbital mechanics, you can go in any direction you like.
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From my vague memories of exploring the concept for a book I was working on and eventually scrapped, you'd use the solar sail to gain momentum, pull the sail when approaching a body, use gravitational sling-shot maneuvers to head back toward the Sun, then not deploy the sails again until you were ready to turn back around, if you didn't use sling-shot maneuvers for your next course correction.
It'd be a handy tool to develop for sure, especially considering how small they can make exploratory vessels that ar
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You're always orbiting something. You don't move directly away from whatever you're orbiting without obscene amounts of thrust - you spiral away from it.
With a solar sail at an angle you can increase or decrease your orbital velocity, which will increase or decrease your orbital radius.
Is this a con? (Score:3)
It could at best 'sail' one way ... down wind. Gravitation assist to redirect towards a sun/star? The concept resurfaces every couple of years usually from someone looking for money. Thomas Gold [wikipedia.org] didn't believe in it and frankly there really doesn't seem to be any evidence that it works as promoted.
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It could at best 'sail' one way ... down wind. Gravitation assist to redirect towards a sun/star? The concept resurfaces every couple of years usually from someone looking for money. Thomas Gold [wikipedia.org] didn't believe in it and frankly there really doesn't seem to be any evidence that it works as promoted.
Kind Sir, this is slashdot, where a giant ass laser is considered a preferred solution. A terawatt space based one makes downwind anywhere you point it.
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Kind Sir, this is slashdot, where a giant ass laser with sharks is considered a preferred solution.
Fixed that for you.
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Also Extremely Slow (Score:3)
https://www.physicsforums.com/... [physicsforums.com]
When a photon hits a solar sail, it gives the sail momentum. If the photon has momentum P and bounces off a stationary sail, it looks like this:
Think of where the energy is in this system. Before it hits, the photon has energy E. After it bounces, the photon still has roughly energy E. But the sail’s moving, so where did it get its kinetic energy? (Remember, energy — unlike momentum — has no direction.)
The answer lies in the word “roughly”. The photon loses a tiny fraction of its energy to Doppler shifting when it’s reflected, but only a tiny fraction. It is this tiny fraction that goes into pushing the sail. This is a phenomenally small amount of energy — far less than a percent of what the photon has. That is, not much of the photon’s energy is being used for motion here.
This is why solar sails are so slow. It’s not that light doesn’t have that much energy, it’s that it has so little momentum. If you set a squirrel on a solar sail and shone a laser on the underside, do you know how much power would be required to lift the squirrel? About 1.21 gigawatts.
This is awful. If we were lifting the squirrel with a motor, railgun, or electric catapult, with 1.21 gigawatts we could send it screaming upward at ridiculous speeds.
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That description is entertaining, but that's about it. For each reflected photon you gain up to twice its momentum, depending on the angle of incidence. It has nothing to do with the energy. Photons don't have much momentum, so it's not a great way to go to the store and get milk, but you don't have to carry reaction mass so the rocket equation doesn't apply. If you're going a decent distance, a solar sail can get you going much faster than a chemical rocket can.
There are proposals, and small scale demonstr
"New" (Score:2)
It would take much too long. (Score:2)
What is new here? (Score:2)
Sails pop up every few years, but not much is done (Score:2)
Then more people will sail across the sky (Score:1)