Please Consider Including Solar Sails in KSP 2! :)

[Multivac]

_{(There are past threads related to this, but they are "quite old!")}

So I've just recently become aware that solar sails might not be a thing in KSP2 (or at least not at launch), but also that the basic mechanic needed to make solar sails work — namely, the ability to make a ship constantly accelerate even when the player isn't actively flying it or focused on it — almost certainly will be in the game. So... I'm basically just here to beg our wise and awesome KSP2 devs to please please please consider having solar sails in the game after all, mostly because I think they are just about the coolest thing ever. :3

The main reason solar sails don't work well in KSP1 (though there are mods for them!) is that they generate only a very tiny amount of thrust, making the Dawn ion engine look like the Mainsail in comparison. Changing your orbit using a solar sail would take ages! However, in KSP2, unlike in KSP1, it seems we may gain the ability to have a ship continue to accelerate even when we aren't "looking" at it, so there will be no need to sit there staring at your screen for hours at a time at x4 physics warp; you'll be able to just set up your maneuver, and then switch away from the ship to do something else while it accelerates. This makes solar sails quite reasonable as a gameplay mechanic — and they are oh so cool.

Here's the thing with solar sails: While they generate only a tiny amount of thrust, they allow your ship to literally be propelled by the very light streaming from the sun (or Kerbol, in KSP's case). Not in the sense of using solar power to generate electricity or anything — a solar sail is literally pushed by light itself, in the same way that a traditional seagoing sail is pushed by the wind. And, much like a seagoing sail-driven ship might never accelerate as quickly as one with an engine, but can keep on sailing as long as the wind is blowing, so too a solar sail can continue driving your spacecraft as long as you're anywhere near a star — no fuel or propellant required. The star itself is your engine!

This means that while your acceleration is low, it is also constant. You don't have to worry about running out of fuel, ever, and so instead of having to plan out short, optimally efficient burns, you can just keep building up your velocity — and with a bit of time, you can reach speeds much higher than what any conventional rocket could hope to achieve before it runs out of delta-v. With solar sails, running out of delta-v isn't really a thing, at least until the day Kerbol goes extinct!  This means that despite its lower acceleration, a solar sail could potentially reach remote destinations much quicker than a traditional rocket could, by gradually building up speed until it's moving much faster than any rocket. This also makes solar sails a practical means of potentially launching ships into interstellar space (especially with something called laser assist, though that would probably need to be a whole additional gameplay mechanic — potentially a very cool one — and I won't get into that here).

As with sail-driven sea craft, you can "tack," in a sense, to control the direction in which you accelerate — solar sails are not limited to accelerating away from a star, just as sailing ships of old were not limited to only sailing with the wind. By angling the sail relative to the incoming light, you can accelerate prograde or retrograde, as with a more conventional engine, thus lowering or raising your orbit! (In terms of gameplay mechanics, I'm imagining something similar to the way solar panels in KSP1 can already tell their angle relative to incoming sunlight, and how much sun exposure they have.)

Another cool thing about solar sails is that they have already been used for actual spacecraft propulsion in real life, and so despite sounding cool and science fictiony, are already a 100% confirmed real, practical means of spacecraft propulsion.

So I, for one, would be super excited to see solar sails in KSP2. What do y'all think?

^{Solar sails: So space travel can look like this...}

^{But feel like this.  (With apologies to Disney!)}

[OHara]

Those earlier threads linked in the OP are interesting, even though they have automatic "This thread is quite old" tags.

I would like to see solar sails in KSP2, but do no expect to see them in the first release.

43 minutes ago, Multivac said:

This means that while your acceleration is low, it is also constant. You don't have to worry about running out of fuel, ever,  [. . .] This means that despite its lower acceleration, a solar sail could potentially reach remote destinations much quicker than a traditional rocket could

The reason I do not expect sails, is that the game designers will make sure that rockets are capable of fast-enough interstellar trips, by setting interstellar distances and rocket performance.  (Somewhat like KSP1 set Kerbin to be 1/10 the size of Earth, allowing 4-minute times to orbit at 2-g-or-less acceleration.)  I guess most players will want more rockets than they will want sails, so we will need to wait for, or make, a mod.

I thought this came up in the podcast (thread) can't remember when during that hour of discussion.  

[Guest]

Previously said I include that Nate wanted to add solar sails but said this is a rockets game. Of course tho you know that modders will make it

[Multivac]

51 minutes ago, The Doodling Astronaut said:

Previously said I include that Nate wanted to add solar sails but said this is a rockets game. Of course tho you know that modders will make it

... Oh. I always thought it was a... "space exploration" game, rather than a "rockets" game specifically...

Edited December 6, 2020 by Multivac

[Meecrob]

5 hours ago, Multivac said:

... Oh. I always thought it was a... "space exploration" game, rather than a "rockets" game specifically...

I get what you are saying but lets be honest: its cool to see a skyscraper shoot flames out its butt and go to space. Not so cool watching a giant blanket accelerate at 0.001m/s for 80 hours straight. I'm guessing they will spend most of their dev time on the "skyscrapers shooting flames" part. Or to put it another way, they are almost guaranteed people will use rocket parts, whereas only us nerds will use solar sails for like a realism playthrough or an IRL mission re-creation.

[Multivac]

1 hour ago, Meecrob said:

I get what you are saying but lets be honest: its cool to see a skyscraper shoot flames out its butt and go to space. Not so cool watching a giant blanket accelerate at 0.001m/s for 80 hours straight. I'm guessing they will spend most of their dev time on the "skyscrapers shooting flames" part. Or to put it another way, they are almost guaranteed people will use rocket parts, whereas only us nerds will use solar sails for like a realism playthrough or an IRL mission re-creation.

I mean, I'd argue that a vast, beautiful, elegant spacecraft literally sailing through space is pretty dang awesome and has quite a bit of romance to it, but I guess I get what you are saying as well.

[Guest]

Nate suggested in a podcast that they might be DLC material. I'm cool with that as they would need a fair bit of programming to work well, so it's understandable that they'd want to focus on rocket-like things for the initial release.

But yes I would very much love to have them. There's a romance to solar sails that appeals to me, a sci-fi version of the high seas in the Age of Sail...

[KerikBalm]

Light sail  plus big arsch laser installation = interstellar propulsion. I'd like to see them combined with a beamed power mechanic, where they (and other types of drives) can be powered by sunlight, or lasers/microwave arrays.

They could lead to cool hybrid craft using sails close to stars and colonies with power beaming arrays, and some other propulsion (chemical, nuclear, purple space magic) at more distant destinations.

[haumea]

A solar sail would be awesome! Cant imagine how you would program one though, I imagine it would be pretty hard to make something like that, but who knows? They made an entire solar system right?

[Guest]

16 minutes ago, haumea said:

A solar sail would be awesome! Cant imagine how you would program one though, I imagine it would be pretty hard to make something like that, but who knows? They made an entire solar system right?

It wouldn't be that hard, but it would need specific programming that's different from a rocket. It would build on the brachistochrone trajectory planning they're already implementing.

I expect you would set your sail angle relative to the sun/star, and it would show you the resulting trajectory; the difference to a reaction engine brachistochrone trajectory would be that the solar sail's acceleration for any given angle relative to the sun/star is a function of distance to the sun/star, which changes as you fly towards or away from it, whereas for the reaction engine it's a function of mass, which changes as you dump reaction mass. Either way it'd have to account for changing acceleration over the course of the trajectory.

Things would get pretty funky when you're orbiting a planet, though, and you'd probably need a different setting for that. Probably something like dialling in the direction you want to go (prograde, retrograde, radial in/out, normal/anti-normal), and the game would figure out the optimal sail angle relative to the star/sun and plot you a trajectory.

Edited December 10, 2020 by Guest

[DerkyJerkyWreaksHavoc]

On 12/6/2020 at 2:45 PM, Multivac said:

_{(There are past threads related to this, but they are "quite old!")}

So I've just recently become aware that solar sails might not be a thing in KSP2 (or at least not at launch), but also that the basic mechanic needed to make solar sails work — namely, the ability to make a ship constantly accelerate even when the player isn't actively flying it or focused on it — almost certainly will be in the game. So... I'm basically just here to beg our wise and awesome KSP2 devs to please please please consider having solar sails in the game after all, mostly because I think they are just about the coolest thing ever. :3

The main reason solar sails don't work well in KSP1 (though there are mods for them!) is that they generate only a very tiny amount of thrust, making the Dawn ion engine look like the Mainsail in comparison. Changing your orbit using a solar sail would take ages! However, in KSP2, unlike in KSP1, it seems we may gain the ability to have a ship continue to accelerate even when we aren't "looking" at it, so there will be no need to sit there staring at your screen for hours at a time at x4 physics warp; you'll be able to just set up your maneuver, and then switch away from the ship to do something else while it accelerates. This makes solar sails quite reasonable as a gameplay mechanic — and they are oh so cool.

Here's the thing with solar sails: While they generate only a tiny amount of thrust, they allow your ship to literally be propelled by the very light streaming from the sun (or Kerbol, in KSP's case). Not in the sense of using solar power to generate electricity or anything — a solar sail is literally pushed by light itself, in the same way that a traditional seagoing sail is pushed by the wind. And, much like a seagoing sail-driven ship might never accelerate as quickly as one with an engine, but can keep on sailing as long as the wind is blowing, so too a solar sail can continue driving your spacecraft as long as you're anywhere near a star — no fuel or propellant required. The star itself is your engine!

This means that while your acceleration is low, it is also constant. You don't have to worry about running out of fuel, ever, and so instead of having to plan out short, optimally efficient burns, you can just keep building up your velocity — and with a bit of time, you can reach speeds much higher than what any conventional rocket could hope to achieve before it runs out of delta-v. With solar sails, running out of delta-v isn't really a thing, at least until the day Kerbol goes extinct!  This means that despite its lower acceleration, a solar sail could potentially reach remote destinations much quicker than a traditional rocket could, by gradually building up speed until it's moving much faster than any rocket. This also makes solar sails a practical means of potentially launching ships into interstellar space (especially with something called laser assist, though that would probably need to be a whole additional gameplay mechanic — potentially a very cool one — and I won't get into that here).

As with sail-driven sea craft, you can "tack," in a sense, to control the direction in which you accelerate — solar sails are not limited to accelerating away from a star, just as sailing ships of old were not limited to only sailing with the wind. By angling the sail relative to the incoming light, you can accelerate prograde or retrograde, as with a more conventional engine, thus lowering or raising your orbit! (In terms of gameplay mechanics, I'm imagining something similar to the way solar panels in KSP1 can already tell their angle relative to incoming sunlight, and how much sun exposure they have.)

Another cool thing about solar sails is that they have already been used for actual spacecraft propulsion in real life, and so despite sounding cool and science fictiony, are already a 100% confirmed real, practical means of spacecraft propulsion.

So I, for one, would be super excited to see solar sails in KSP2. What do y'all think?

^{Solar sails: So space travel can look like this...}

^{But feel like this.  (With apologies to Disney!)}

Eh... good idea EXCEPT for one problem.. how do we accurately calculate Delta V and thrust from the solar sails accurately when its tiny photons hitting these sails not Hypersonic thrust plumes. Also, Solar Sails is still a technology that hasn't really proven itself and is hard to scale accurately because it involves a lot and I MEAN a lot of theorem. So although i am for solar sails, i am not for the complexity for these sails. Also, this isn't real life its a video game and needs to be both Expert and Noob friendly not just one side of the story. another thing is how do we accurately measure photons from stars that don't exist? i guess KSP2 isn't supposed to be world accurate but still... You can't even affect the thrust or turn it off because there is always light in the universe (and no I'm not speaking biblically)which means that a light sail is basically a super efficient solid rocket booster that can't be throttled or turned off.   Y'all get what i mean? 

 

Edited December 10, 2020 by DAFATRONALDO2007 IN SPACE

[Multivac]

On 12/10/2020 at 10:22 AM, DAFATRONALDO2007 IN SPACE said:

Eh... good idea EXCEPT for one problem.. how do we accurately calculate Delta V and thrust from the solar sails accurately when its tiny photons hitting these sails not Hypersonic thrust plumes. Also, Solar Sails is still a technology that hasn't really proven itself and is hard to scale accurately because it involves a lot and I MEAN a lot of theorem. So although i am for solar sails, i am not for the complexity for these sails. Also, this isn't real life its a video game and needs to be both Expert and Noob friendly not just one side of the story. another thing is how do we accurately measure photons from stars that don't exist? i guess KSP2 isn't supposed to be world accurate but still... You can't even affect the thrust or turn it off because there is always light in the universe (and no I'm not speaking biblically)which means that a light sail is basically a super efficient solid rocket booster that can't be throttled or turned off.   Y'all get what i mean? 

 

With respect, I don't actually think any of this is quite true.

I don't think calculating the thrust on a solar sail would be that much harder than simulating the thrust of a rocket engine. It would be a bit more complex, since it would vary with distance from the star and the angle of the sail relative to the incoming light, true, but this doesn't seem prohibitively complex compared to, say, jet engines that vary their thrust based on available intake air, or several other mechanisms we already have in KSP1. Solar panels in KSP1 already vary their power output based on their angle relative to the incoming sunlight, for example, so why couldn't a solar sail vary its thrust in a similar way?

Nor is there anything inherently complex about solar sail technology, as compared to rocket engines. The hardest part in real life is manufacturing the material out of which the sail is made, which must be lightweight, strong, and highly reflective; but in a computer game, any material can have any simulated properties we want. Plus, a solar sail has almost no moving parts, aside from those needed to deploy it! The concept of relying on photon pressure may seem complex, but at the end of the day, the mechanism is basically "thing pushes other thing," not really more complex, in basic principle, than a 17th-century canvas sail on a wooden ship being pushed by the wind.

Also, saying that "Solar Sails is still a technology that hasn't really proven itself" really isn't true at all! As I mentioned in my original post above, it has already been used on at least two real-life space probes, both of which worked as intended. Solar sails may not be in widespread use, but they absolutely are a proven technology that we know works, and that has already been used to propel real-life spacecraft. There are literally already real-life space missions that you couldn't copy in KSP2 unless solar sails were included.

As for "turning off" a solar sail, that can be as simple as turning it edge-on to the sun. Again, just as a solar panel in KSP1 that is edge-on to incoming sunlight won't produce any power. Optionally, a mechanism could be included to retract or partially retract a solar sail; in real life such a mechanism might be too complex or heavy to be practical, but in a KSP game, it needn't be any more complex to implement or control than any other deployable part.

As for the balance between realism and noob-friendliness, solar sails could fall anywhere on this realism-noobishness spectrum, depending on how they're implemented. After all, literally every piece of technology in KSP, including every single conventional rocket engine, must face the same balancing problem! Even the most basic rocket engine could be made incredibly complex if the game's designers wanted to; we could all be fiddling with fuel pumps and tank pressure levels just to get a basic Reliant to work. The programmers found a good balance between fun and realism instead, simplifying some aspects of how a rocket engine works while simulating other aspects with a fair amount of realism. And why couldn't the exact same thing be done for solar sails? If the game's designers choose, they could make solar sailing as simple as pushing a button to deploy the sail, and then using your standard WASD controls, or maybe a few buttons on the sail part's right-click context menu, to change how much thrust it's producing, and in which direction. As with ion engines, they could improve the sail's thrust-to-weight ratio compared to real life, and take other steps to make it newb-friendly. The new continuous thrust controls that are already to be included in KSP2 should help with this, by giving the player an easy way to plan out the sail's trajectory as it accelerates.

So just because solar sails are different from traditional rocket engines, and seem like such a crazy and far-out technology at first glance, does not actually mean they need to be any more complex in terms of gameplay than any number of engines and other devices we already have in KSP1, or that we already know are going to be included in KSP2.

[mcwaffles2003]

On 12/10/2020 at 9:49 AM, haumea said:

A solar sail would be awesome! Cant imagine how you would program one though, I imagine it would be pretty hard to make something like that, but who knows? They made an entire solar system right?

Shouldn't be hard as there are only a few rules to them:

 

• Force is quadratically and inversely proportional to distance for the sun

Spoiler

• Force is linearly proportional to surface area of the sail 
• Force is proportional to the Cos²(angle between the incident and reflected ray)   [Cos once for reducing force for larger angles of incidence deflecting the light less and another cos for shrinking light/m² as angle of incidence increases]

Spoiler

• Force is in the direction opposite the normal vector bisecting the region between the incident and reflected ray

Spoiler

And that's about it.

Edited December 19, 2020 by mcwaffles2003

[Incarnation of Chaos]

I mean i wouldn't mind them in KSP2, but...

We're going to have torch ships, Orion and potentially Von Neumann machines. Solar Sails just seem kinda out of place in that context, they would be fantastic for deceleration and as massive Wipple shields to protect against the interstellar medium.  But in stock? I can already see most people just seeing them as much, much worse Ion Drives. I guess i'm mostly just saying i think introducing solar sales alone wouldn't be the best way to do it, they'd be better coming with additional mechanics making them useful for things besides propulsion (The Japanese probe used LCD patches as a supplement for it's reaction wheels and RCS, now that's something I'd love).

Like a partially configurable sail, where you could decide on a number of "Bands" and what materials they'd have. That way you could use them as gigantic standalone solar panels if you wanted, with the according weight penalty. Then again, I'm just expecting something like that the come via mods in the end.