How do you fly the solar sail?

[Izack]

I suggest, a "solar sail autopilot" must hold determined angle to sun, and work properly even on high time accelerations (x100 or even x1000).

I'd settle for some thing that told me the ideal angle, and then AttitudeMFD could handle the rest. Instead of course corrections during the flight, the player would occasionally have to re-determine the nominal angle and reorient the sail accordingly.

 

[CigDriver]

I looked through the code a few nights ago to move the docking port to the far end of the sail and noticed all the interesting stuff in the code. It looks to me all that is missing is some way to activate the paddles. They are animated and there is code that changes the force on the sail. i didn't dive deep enough to see if it was all active, plus the math in there is way over my head and coding abilities

The sail with the docking port moved to the end of the trusses didn't work too well. The DG has a hard time rotating it, and I didn't see any acceleration based on the solar pressure. It might work if you launch it into interplanetarry space though.

 

[vonneuman]

I would like to take on the project of a low thrust mfd. With out a mesh this will be much simpler then the space plane I have been working on for a week. But I have a question for the more experienced mfd makers. For this to work the mfd will have to know what angle the sail is to the sun. That means that the mfd will have to get it's heading from some source. My question is can the mfd get up-to-date information on the ship's heading by reading the scenario file? If not how can the mfd get that information? I will also need a way of calculating how much thrust the ship's engine is giving off.
Right now I am trying to make sense of this paper on the calculating the fight paths of solar sails:http://www.spacesailing.net/paper/200408_Providence_Dachwald_Sail.pdf
I haven't taken anything more then high school trig and physics so for me it is pretty intense stuff. Might take a while.

 

[BrianJ]

The possibilities for a bit of solar sailing are the most interesting new feature in Orbiter 2010, for me. It's got me thinking about just what the optimum attitude for the sail is for reducing/expanding it's orbit. And what would the logistics be for an attitude control system using the "steering paddles" ? etc. etc.

I suggest, a "solar sail autopilot" must hold determined angle to sun, and work properly even on high time accelerations (x100 or even x1000).

IEATMFD will hold the vessel attitude relative to velocity vector at high time accelerations, but it works by setting the vessel attitude mathematically so you may think that is "cheating" - depends on what you want to do with the simulation.

I looked through the code a few nights ago to move the docking port to the far end of the sail and noticed all the interesting stuff in the code. It looks to me all that is missing is some way to activate the paddles. They are animated and there is code that changes the force on the sail. i didn't dive deep enough to see if it was all active, plus the math in there is way over my head and coding abilities

Yes, it looks like it just needs some key commands to set the paddle rotations. Anyone have the time to fix it?

Cheers,
Brian

---------- Post added at 11:06 AM ---------- Previous post was at 10:50 AM ----------

vonneuman - thanks for the link to that .pdf, at a quick glance it looks like it answers a lot of my questions about solar sailing :thumbup:

Good luck with your project, if you get into the OrbiterAPI, you can see that you can access just about any parameter for a vessel from an MFD, no problem.

 

[jedidia]

My question is can the mfd get up-to-date information on the ship's heading by reading the scenario file?

You don't need the scenario file for that. You can get all parameters from the vessel directly, and there are functions for transforming all parameters between global and local reference (i.e. relative to the sun or to any body you are currently orbiting). The real trouble here is the math involved, you can't do it without some serious skill in differential and integral math (actually you can, but then you'd have so many iterations that the thing would be awfully slow, and not as precise...)

 

[CigDriver]

[clip...]For this to work the mfd will have to know what angle the sail is to the sun. That means that the mfd will have to get it's heading from some source. My question is can the mfd get up-to-date information on the ship's heading by reading the scenario file? If not how can the mfd get that information? [...clip]

Here is a bit of code I wrote to determine the angle of the sun to a solar array. While not exactly what you need it may be helpful:

  //Check to see what the angle between the sun and solar arrays
    VECTOR3 lspos, rspos;//holder for relative position from sun
    VECTOR3 lppos = {0,0,1};//solar panels tangent always point along z axis
    VESSEL * v = oapiGetVesselInterface(vesselObject);//identify our vessel
    v->GetGlobalPos(rspos); //relative sun position
    rspos = -rspos/length(rspos);//invert and normalize sun relative position
    MATRIX3 R;//holder for rotation matrix
    v->GetRotationMatrix(R);//get rotation matrix
    lspos = tmul(R,rspos);//inverse rotation
    sunAngle = (((acos(dotp(lspos,lppos)))*(180/PI)));//calculate angle

I've never written a MFD, so some of the code may need to change since this was written for a ship .dll.

 

[vonneuman]

That code will work great.

 

[JEL]

I was attempting to fly the solar sail that comes with 2010 but I can't turn it. There is nothing in the Orbiter manual about how to fly it. It doesn't rotate or anything like that. Can someone help me?

If you're interested then here's an alternative way to play around with radiation-pressure in Orbiter:

Make a new vessel with this in it's config-file:

ImageBmp = Images\Vessels\Default\nasa_mmu.bmp
MeshName = mmu
Mass = 1
Size = 1000
MaxMainThrust =  	10000000
MaxRetroTrust =  	10000000
MaxHoverThrust = 	10000000
MaxAttitudeThrust = 10000
CameraOffset = 0 0 0
CrossSections = 1 1 1
;RotResistance = 10000 10000 10000
Inertia = 10000 10000 10000
;GravityGradientDamping = 0.0
PropellantResource1 = 1 1
Isp = 100000000000


; === Docking ports ===
BEGIN_DOCKLIST
0.0 0.0 0.0   0 0 1    0 1 0
END_DOCKLIST


; === Attachment specs ===
BEGIN_ATTACHMENT
P 0 0 0  0 -1 0  0 0 1  XS
P 0 0.9 0.1  0  1 0  0 0 1  GS
END_ATTACHMENT

This will give you a controllable vehicle that reacts to radiation-pressure.

Then make a scenario with it in orbit around the sun, or you can even do one with it landed on the sun, and it will shoot off into deep space.

Or you can set it up around the earth or moon and watch how it reacts when it crosses the radiation-pressure 'horizon' (when coming out of the planet shadow and into sun-light).

Not a realistic vessel, but atleast a clear and easy way to see some actions of the radiation-pressure in Orbiter