Solar Sails

[SasquatchM]

Someone write an add-on for me to use!!




Please?

[Scotius]

Holy cow - that's huge

[Fractal_UK]

Someone write an add-on for me to use!!

Please?

Interstellar has an experimental solar sail part module that could control this, it works at physical speeds but it doesn't yet work under on-rails time warp, while that's not surprising - other KSP engines are the same - I'd really like to get on rails working because it makes a solar sail function sensibly.

I can certainly put some more work into it if you're interested?

[SasquatchM]

That would be great! I have no coding skill at all, so I could certainly use your help.

The only other thing I could think of was to make a regular engine powered by whatever the sail collects and just set the flameoutThreshold very low.

[Fractal_UK]

That would be great! I have no coding skill at all, so I could certainly use your help.

The only other thing I could think of was to make a regular engine powered by whatever the sail collects and just set the flameoutThreshold very low.

If you have an install with KSP Interstellar you can try the existing code by replacing whatever MODULE{} you're using to animate that sail in the .cfg file with

MODULE
{
    name = ModuleSolarSail
    surfaceArea = 100 // replace with the actual surface area of the sail
    animName = sailAnim // replace with the name of the animation you're using to deploy/retract the sail
}

Stick to physical timewarp while you have the thing deployed though, there is some code that will try to adjust your orbit during non-physical timewarp and it tends to slowly make your orbit unstable at the moment. I'm fairly sure I can fix it though.

[aeTIos]

Holy moly, that's one big part O.O

[SasquatchM]

With this module is the thrust delivered along the axis of a transform or just away from the sun?

I am also assuming that the area is in meters squared?

1444 square meters currently

Edited January 6, 2014 by SasquatchM

[SasquatchM]

The deploy animation works great, although there doesn't seem to be a retract. I assume the force being displayed is the actual "thrust" being applied to the craft, but I am not seeing a change in the actual vector so far. I also did not let it run for any length of time. Definitely steps in the right direction though.

[Fractal_UK]

The deploy animation works great, although there doesn't seem to be a retract. I assume the force being displayed is the actual "thrust" being applied to the craft, but I am not seeing a change in the actual vector so far. I also did not let it run for any length of time. Definitely steps in the right direction though.

Yeah, I was playing around with the module earlier and though I did write the retraction code, the button never appears - I guess I never got far enough to need it! If you try max physical time warp for a while, you should see a change in your peri/apoapsis.

At present the thrust is just applied parallel to the sail orientation so that needs some work too. I did make a little progress making it work better during timewarp but it's still a little unstable.

[SasquatchM]

Is it based off of the existing solar panels? I noticed it does lose thrust if LOS is blocked. And you say parallel to orientation. I an assuming you mean along the KSP Y axis / model Z axis?

Also, does it receive thrust from both sides and only when deployed?

Edited January 7, 2014 by SasquatchM

[Fractal_UK]

Is it based off of the existing solar panels? I noticed it does lose thrust if LOS is blocked. And you say parallel to orientation. I an assuming you mean along the KSP Y axis / model Z axis?

No, it's not based on the solar panels, it's entirely new code, it uses a proper inverse square curve so should be much more effective near the sun. Yeah, the thrust is applied along the KSP Y axis, which thinking about it is actually all we need because the other components cancel.

Also, does it receive thrust from both sides and only when deployed?

It does receive thrust from both sides. I think in the version you're using it applies thrust while not deployed but that module is very much a half-finished test, I've already fixed some of the problems today.

[SasquatchM]

Nice

The only other issue I can see is the time warp. It does apply thrust, and oddly stabilizes itself at the apoasis.

I think, to really make this functional it is going to have to maintain it's heading relative to the sun, or at least have the thrust always applied in a line from the sun.

I'll admit I may not be thinking about this clearly, but it seems to make sense.

by the way, I really do appreciate all of the work

[Fractal_UK]

I think I've pretty much got it working now, it isn't at all easy to fly with until you get the hang of it. It's pretty powerful in the inner system but going to the outer system is all about making your orbit increasingly ellipitcal so that during the phase close to periapsis you can make the most of all those photons to raise your orbit.

I also decided to lie about the area and pretend the surface area is 100x bigger in order to increase the thrust (the size I've used is still perfectly reasonable for a realistic solar sail, it's just not reasonable to portray in game at that size, so I think that's fine). It probably still needs something to help control it, I'm wondering if I can lock the orientation of the craft relative to the sun because that's potentially helpful. It's pretty cool though, I even got a couple of Duna encounters - I mean, those aren't so useful since I had to eject it from Kerbin to make successful use of it and that is most of the delta-v cost of a Duna mission right there but I could see it shining for Low Kerbol missions, Moho missions and maybe also some Jool missions.

I could certainly see the sense in using it to deploy things like solar power satellites in Low Kerbol orbit because those missions can easily use up a lot of fuel.

Edited January 7, 2014 by Fractal_UK

[Scotius]

Speaking about near-Kerbol solar power plants...is it possible to turn this sail into an enormous solar panel? Below Moho orbit it would generate ludicrous amounts of power

[SasquatchM]

I guess I don't see why not. It is just another module.

[HoneyFox]

I think I've pretty much got it working now, it isn't at all easy to fly with until you get the hang of it. It's pretty powerful in the inner system but going to the outer system is all about making your orbit increasingly ellipitcal so that during the phase close to periapsis you can make the most of all those photons to raise your orbit.

I also decided to lie about the area and pretend the surface area is 100x bigger in order to increase the thrust (the size I've used is still perfectly reasonable for a realistic solar sail, it's just not reasonable to portray in game at that size, so I think that's fine). It probably still needs something to help control it, I'm wondering if I can lock the orientation of the craft relative to the sun because that's potentially helpful. It's pretty cool though, I even got a couple of Duna encounters - I mean, those aren't so useful since I had to eject it from Kerbin to make successful use of it and that is most of the delta-v cost of a Duna mission right there but I could see it shining for Low Kerbol missions, Moho missions and maybe also some Jool missions.

I could certainly see the sense in using it to deploy things like solar power satellites in Low Kerbol orbit because those missions can easily use up a lot of fuel.

Ah, glad you restart the working on solar sails...

Mine has been laid aside for quite a few months. Because i had met some difficulties not being able to transform the velocity in world coordinate system to the one that is used in orbit velocity vector system.

Oh and NathaneKell seems to be interested to write something to allow time-warp orbit velocity manipulating (intended for ion thrusters as he stated), perhaps you can contact with him too.

[Fractal_UK]

Ah, glad you restart the working on solar sails...

Mine has been laid aside for quite a few months. Because i had met some difficulties not being able to transform the velocity in world coordinate system to the one that is used in orbit velocity vector system.

Oh and NathaneKell seems to be interested to write something to allow time-warp orbit velocity manipulating (intended for ion thrusters as he stated), perhaps you can contact with him too.

Yeah, the module is loosely based on the code you sent me but, you're right, it's actually very difficult to get the orbits to update properly with a continuous acceleration - even if you get the velocity alterations right it's easy to lose numerical stability. I think I have finally solved that problem though.

I think I can use this code to make an engine module that works during timewarp but it would have to be an entirely new engine module with new particle effects handling and everything so it's quite a big undertaking. I'll talk to Nathan though.

[HoneyFox]

Yeah, the module is loosely based on the code you sent me but, you're right, it's actually very difficult to get the orbits to update properly with a continuous acceleration - even if you get the velocity alterations right it's easy to lose numerical stability. I think I have finally solved that problem though.

I think I can use this code to make an engine module that works during timewarp but it would have to be an entirely new engine module with new particle effects handling and everything so it's quite a big undertaking. I'll talk to Nathan though.

I guess that you used some way by increasing the interval between updates dynamically according to the time-warp rate, right?

Anyway that's a good news that you finally solved it.

Talking about a new engine module, i didn't even think about particle effect/FX before Luckily the ion thrusters seem to have no flame FX coming out of its nozzle, the only thing needed might be the "heat" effect.

[Fractal_UK]

I guess that you used some way by increasing the interval between updates dynamically according to the time-warp rate, right?

I just used a temporary update to make the acceleration changes to before changing the vessel's orbit parameters to match. I don't know why but for some reason this produces far better results.

I've used a 2x2 structural panel to double as a solar sail.

I spent over 1600 days in space doing this, about 1000 figuring out how to control it and then 600 or so sailing out to Jool's orbit. The thrust is actually more than adequate provided you don't let your periapsis go far above Kerbin's orbit (i.e. spiralling out is a bad idea, better to raise apoapsis and lower periapsis).

Edited January 8, 2014 by Fractal_UK

[HoneyFox]

That is quite different from my guess. glad you have found it.

For the plan to escape. i did that once with solar sail too. the strategy was to first sun-dive as close as possible by a Kerbin gravity slingshot after a full orbit around the sun. the slingshot lowered the Pe to Eve so that the second slingshot happened (yeah that's quite lucky actually) and helped to lower the Pe further. And later i used solar sail to slow down more along the path to the Pe. Finally i turned the sail to the right orientation to begin accelerating after i reached Pe of the orbit around the sun. Yes the acceleration is much bigger than i thought, i even wondered if it might break the joint connecting the sail to the vessel... (that might because i used some coefficient unrealistically large, too ) and due to Oberth Effect & being very close to the sun, i achieved escape orbit of sun quite easily.

Edited January 8, 2014 by HoneyFox

[SasquatchM]

Here is the part I have been playing with if you want it for testing

Meidafire Link

[Fractal_UK]

Here is the part I have been playing with if you want it for testing

Meidafire Link

The code to control it seems to be working really nicely now. The new code can be found here: https://github.com/FractalUK/KSPInterstellar/blob/develop/FNPlugin/ModuleSolarSail.cs .

I'm having some issue with the texture though:

[SasquatchM]

I was messing around with it. It should be reflective yellow-orange on the -y axis and semi-transparent black on the +y side. I was sort of aiming at a look inspired by this . I perhaps should make the yellow side semi-transparent as well.

If you have any texture / model suggestions let me know

Is it sad that I have no idea what to do with the information in your link?

Edited January 8, 2014 by SasquatchM

[Fractal_UK]

I was messing around with it. It should be reflective yellow-orange on the -y axis and semi-transparent black on the +y side. I was sort of aiming at a look inspired by this http://science.nasa.gov/media/medialibrary/2011/01/24/lab_strip.jpg/image_full. I perhaps should make the yellow side semi-transparent as well.

If you have any texture / model suggestions let me know

Ah okay, just wondered why it looked different to what you showed off earlier. Do you want me to take the reflectiveness / semi-transparency into account in the thrust calculations?

[SasquatchM]

I don't think that is needed. I was just tinkering a bit.Curently is the thrust still applied along the y axis and/or is it dependent on the facing in relation to the star?