mrsolarsail

Thanks all. Make sure to check out SolarSailNavigator to see where your ion engines and sails are going. - - - Updated - - - Thanks for all the feedback. See the v1.0.2 branch for the latest changes: https://github.com/bld/PersistentThrust/tree/v1.0.2 I'm making OnFixedUpdate more modular with methods to calculate & apply deltaV and resource consumption.

And I started a new thread to discuss development here: http://forum.kerbalspaceprogram.com/threads/133735-WIP-1-0-4-PersistentThrust-v1-0-1-alpha

PersistentThrust is a plugin that allows propulsion systems to operate during timewarp. The plugin includes a new solar sail part and module that allows a spacecraft to be propelled only by sunlight. It also adds a module with a patch to the stock ion engine that allows engines to thrust during timewarp. This plugin was previously a part of SolarSailNavigator, which allows you to plan maneuvers with solar sails or long duration engine burns. Development discussions specific to this module will take place here instead of in the SolarSailNavigator thread. The source code is available on Github: https://github.com/bld/PersistentThrust The plugin can be downloaded from Github: https://github.com/bld/PersistentThrust/releases Features: Animated solar sail part from KSP Interstellar by SasquatchMarmalade Solar sail module modified from the original in KSP Interstellar Persistent Engine module for operating engines during timewarp Patch to the stock ion engine using ModuleManager with realistic thrust (0.25 N) at the same power level. Use as an example to patch your own engines. Operate any combination of engines and solar sails Consumes any number of engine propellants with mass from the vehicle during timewarp Virtual methods for calculating deltaV, resource consumption, and applying resource consumption Known issues: Disabled during timewarp on a suborbital trajectory due to a bug in perturbing the suborbital orbit Consumption of massless resources during timewarp disabled (e.g. ElectricCharge) due to a bug in how KSP requests resources at high timewarp When the thrust of a persistent engine is too high (above ~5 kN), KSP won't allow switching to timewarp (need to check if this is still an issue in v1.0.8) Changelog: see https://github.com/bld/PersistentThrust/releases Thank you to FreeThinker and Felger for reviewing the code. Thanks to OctarineNoise for the fix to address physics lag.

FreeThinker, I posted a standalone version of my PersistentThrust mod (with PersistentEngine and SolarSailPart modules). It's not on CKAN yet. My next version of SolarSailNavigator will depend on it. The biggest change is that PersistentEngine now scans the propellant list for those with mass (density > 0) and without mass (density == 0), and requests the right amount from the vessel. Currently, massless resources (e.g. ElectricCharge) are not requested by default, because of a bug I found at high time warp when requesting ElectricCharge from a solar powered ion engine spacecraft. I haven't implemented the generic interface we discussed, that would allow custom methods of calculating and applying deltaV and resource changes. https://github.com/bld/PersistentThrust/releases/tag/v1.0.1-alpha

Cool, thanks. I was looking for something to link multiple solar sails together into a linear chain for hauling large payloads, and this could work using EVAs and on-orbit assembly.

Has anyone developed mods to with deployable trusses or tethers? I see that Infernal Robotics allows you to link parts of a spacecraft together with rotating parts. I'm looking for something with connecting parts that expand.

Unfortunately, CKAN seems to be having trouble again installing the right directories from the .zip file I posted to Kerbal Stuff. Edit: I pushed a fix which is on KSP-CKAN now.

I have released a new version with support for multiple sails and engines, and moves the navigation control into any command pod. See the first post for info.

If the PersistentThrust module is loaded, and the ion engine is patched to use it, the GUI should have another "Thrust" display at the top, which shows it in everything from mN to kN. Note there's no "Show Controls" button, as this image is from a development version that doesn't have the navigation controls in the engine. Good point. Calculating the preview trajectory could get pretty slow with a low acceleration vessel in planetary orbit. There are a number of ways I've been thinking of improving things. Like, automatic steering strategies that maximize a particular orbit element, and more efficient & accurate numerical integration of the future trajectory.

You're welcome. Yeah, I figure they buffed the ion engines so much because the game is built around Kepler orbits and high thrust, short duration burns.

Thank you. At the current moment, until KSP-CKAN updates, you will need to download the addon from Kerbalstuff or Github, and install Module Manager. It should work with any engine that is patched to use the "PersistentControlled" module instead of "ModuleEngines". In the next version, it should just be "PersistentEngine", because I will be moving the navigation controls out of the engine part, so it can access all sails or persistent engines in the vessel. At the moment, the module only uses the engine that it is attached to. That's the only restriction I know of, unless a module modifies an engine in a way that's incompatible. I haven't tried making it work in planetary orbits, so there may be some unexpected behavior if you try. Planetary maneuvers are on my TODO list. If you're just using the "PersistentThrust" features, and have the controls off, it should work in planetary orbits, you just won't get a trajectory preview. Combined with something like "Persistent Rotation", you could use time warp to raise/lower an orbit by matching the vessel rotation to the gas giant's surface. One issue I currently have is keeping track of resource consumption other than propellant mass. For some reason, my solar electric test vehicle didn't seem to be balancing energy use by the ion engine with energy generation by the solar arrays correctly at high time warp levels. But, it kept following the trajectory, even if it dropped to 0 ElectricCharge on the batteries. I haven't figured out why that's happening.

Thanks for letting me know. Seems CKAN only looked at the first folder (SolarSailNavigator) in the .zip file. I'll try putting both in a "GameData" folder and see if it works correctly. Hmm... Do you have Module Manager installed? It's now required for patching the stock ion engine, which usually only shows thrust in kN. Thanks. I appreciate suggestions on making this easier to use. I'll put those on my "TODO" list. Hopefully I'll have more time to improve the usability now that I have the basic functionality.

I've posted a new version that supports ion engines now. See the first post for details.

I updated the version of KSP to 1.0.4 on Kerbal Stuff after testing the plugin. I'm not sure if this will automatically update CKAN, which doesn't show the plugin at the moment. But, you can still get the latest SolarSailNavigator (1.0.2) at Kerbal Stuff and my Github. - - - Updated - - - I think with the changes I'm making, it should be a simple matter of patching the engine part config file.

Thanks for the feedback. - - - Updated - - - Sorry for the late response. I've been traveling a lot lately. I'm working on a version that splits the thrust from the navigation, and supports ion engines and similar low thrust rockets. You can follow the progress at: https://github.com/bld/PersistentThrust - - - Updated - - - Cool. It should be up on CKAN. I'm updating to the latest KSP version to see if the available sail plugin still works. I am making progress on a newer version that separates the thrust model (sail, ion engine, etc) from the navigation. I've been traveling and working a lot lately, and have had less time.

More details: http://www.planetary.org/blogs/jason-davis/2015/20150607-lightsail-deployment-initiatied.html

FYI, LightSail just deployed. http://sail.planetary.org/missioncontrol

Thank you. That feature is on my todo list. The plugin currently saves the maneuver sequence, so I hope I can use that to update the orbit when you leave and return to the sail (or other low thrust propulsion system).

I have released a new version, v1.0.2-alpha, and updated the top post. The plugin now scales the line width to the camera distance, and lets you see how far off you are from a target object at the end of your maneuver sequence. I'll update the tutorials for the new feature. Manually planning a rendezvous trajectory using low thrust is pretty difficult, because there are so many things to adjust (angles, times, number of maneuvers). You can get pretty close, but it may be a good idea to have a secondary propulsion system to close the gap. I plan on implementing an automatic system to fine tune the trajectory for precise rendezvous.

FreeThinker, I got your message, but couldn't reply. I can try to make low thrust engines during timewarp work. Basically, the solar sail force model multiplies the acceleration by the time step size and adds that to the current velocity. It then updates the vessel's orbit to the current position and the updated velocity. The only additional pieces are to get the current throttle setting and to update the mass over the time step. I can just use the rocket equation at constant thrust over the duration of each time step to calculate the change in mass. It will take a bit more effort, but I think I can make it work with the solar sail navigation planning tool. I just need to make it more generic, so that a slightly different force model can be plugged in and used. I think I'd also like to plug in different reference frames as well, since the cone/clock system is pretty sail-specific.

Thanks. I'll check it out. - - - Updated - - - Does anyone know what KSP uses to draw the orbit lines so they are the same width at any zoom level? Is it the Vectrosity VectorLine? I'm currently using LineRenderer, but would like something cleaner looking, like the game's orbit lines. I tried duplicating the Principia plugin's use of VectorLine, but it didn't appear on the map.

You're very well read on the subject. Generally, you just need to numerically integrate the force equation of a sail. The logarithmic spiral is the rare case of an analytical solution. Unfortunately, it's not very useful. I think it would be an interesting exercise to use a rocket to start one and set the sail to the appropriate angle. That's true. I was thinking of setting up some automatic modes like orbit raising to escape, orbit lowering to capture, inclination changes, circularization, etc. I need to work out the equations from those papers. It would work by calculating the optimal sail angle for maximizing the change in semimajor axis, inclination, eccentricity, etc. There are analytical solutions for those steering strategies. I would really appreciate help developing the solar sail tutorial materials. For the next step in the flight school, I wanted to show how orbits work, and how the force on a sail changes them. Then, it would overlap with the KSP plugin. - - - Updated - - - I have heard of the plugin, though I haven't tried it. It probably conflicts with SolarSailNavigator currently. I define a reference frame that rotates with the vessel as it orbits the sun, then forces the vessel to an attitude offset from that frame by the "cone" and "clock" angles. If Persistent Rotation let me define that same scenario, I could just use it. Another feature I'd like to have eventually is spinning sails, like IKAROS.

I'm developing a plugin to help plan flights by solar sail, and I could use some help. The main thread is here: http://forum.kerbalspaceprogram.com/threads/119579-WIP-1-0-2-SolarSailNavigator-v1-0-1-alpha I am currently showing a preview in map mode of the future trajectory using the LineRender, but I'd like something nicer - and constant screen width - like the normal orbit lines in map mode. Is there a good, clear example showing how to do this? Additionally, I want to render small meshes (e.g. squares) to show the sail attitude along the trajectory in map mode, but again, I'm having trouble finding some clear examples. Does anyone have suggestions? Thanks.

I added more pictures in the wiki to explain the "Cone" and "Clock" steering angles: https://github.com/bld/SolarSailNavigator/wiki/Reference-Frames

I hope this can help with that task. With 3-body gravity (sun/planet/spacecraft or planet/moon/spacecraft), solar sails would even make interesting communications satellites themselves. The thrust of a sail can create "artificial Lagrange points" that do things like hover north or south of the natural Lagrange points, with visibility of the polar regions and all satellites in orbit. Here's an illustration of the Sun-Earth ones.