Powering Space Stations.

[The Flying Kerbal]

Hey Guys!

Space stations are something I seldom work with so have basically zero experience with them.  However I came up with the idea of putting a science lab into orbit so I could dock vessels returning from other celestial bodies, dump off the science and let the lab get to work processing it.  I got a contract to build a space station in LKO which had to hold so many Kerbals, have a certain amount of mono propellant, and there might have been something to do with liquid fuel too.  So I thought I'd get clever and take the opportunity to launch "SpaceLab", with all the necessary bits and pieces required to fill the contract, and a science lab thrown in for good measure.

I thought I was super smart with this one, I built a "power generation module", basically four solar panels attached to a modular girder adaptor, positioned on one side of the vessel, which would automatically trek the sun as it orbited Kerbin.

And it works(!) - well at least partially...  The problem is that as soon as I jump to another vessel or the KSC, SpaceLab is no longer subjected to simulated physics, the trekking stops and even if the panels are exposed to Kerbol, the batteries aren't recharged.  The lack of trekking could be got around if I attempt another space station, simply put small solar panels on all sides of the vessel, then no matter what direction it's facing, some of them are bound to be exposed to the sun (on the day side of the planet).  However if I can't recharge the batteries unless I'm actually focused on the station, it doesn't really help very much...

So how do those of you who work a lot with space stations power them?  Processing the science is requires a fair bit of electric charge, indeed I don't have enough batteries to power it during its passing through the night side of Kerbin, but that's me being stupid and not adding enough of them in he VAB.  But I'm stumped as to how to keep the batteries recharging during the daylight period of the orbit, so any ideas and suggestions will be very much appreciated.

 

[bewing]

Electricity is not modeled for vessels outside physics range. Their functions (drills/converters/MPLs) do not use any electricity. Their panels/RTGs/fuel cells do not produce any electricity. They will continue to operate forever with exactly what they have.

 

 

[Gargamel]

Orient your station so the panels are on the most normal or anti-normal (ie North or South) side of the station.   That way, no matter the orientation of the rest of the station as it orbits the planet, the panels will always be at maximum exposure.   So when you do jump to the station, it will always be recharging, if it can see the sun. 

Edited July 14, 2018 by Gargamel

[Xd the great]

Or just use sun tracking panels. Position 3 on the lab using symmetry. Guarenteed to have at least 2 absorbing sunlight.

[Kryxal]

In this case, I'd say specifically north and south.  Around any other body, that ends up being sun-relative normal and antinormal (give or take the inclination of the body's orbit).

[The Flying Kerbal]

Thanks everyone for taking the time to answer.

On 7/14/2018 at 9:52 PM, bewing said:

Electricity is not modeled for vessels outside physics range. Their functions (drills/converters/MPLs) do not use any electricity. Their panels/RTGs/fuel cells do not produce any electricity. They will continue to operate forever with exactly what they have.

 

 

Having never used drills, etc. I will accept what you say, but the Science Lab doesn't seem to do that unfortunately... 

 

23 hours ago, Gargamel said:

Orient your station so the panels are on the most normal or anti-normal (ie North or South) side of the station.   That way, no matter the orientation of the rest of the station as it orbits the planet, the panels will always be at maximum exposure.   So when you do jump to the station, it will always be recharging, if it can see the sun. 

I've now done this but don't think it'll solve the problem of batteries not charging when I'm not focused on the space station.  I could be wrong though, time will tell.

 

12 hours ago, Xd the great said:

Or just use sun tracking panels. Position 3 on the lab using symmetry. Guarenteed to have at least 2 absorbing sunlight.

I am using panels which trek the sun, although because of my original plan I admit they may not be in the best position to do so. I'll post an image or two to let you see.

 

9 hours ago, Kryxal said:

In this case, I'd say specifically north and south.  Around any other body, that ends up being sun-relative normal and antinormal (give or take the inclination of the body's orbit).

Yes, after my original plan failed so miserably, and after reading the posting by Gargamel, I have now orientated the space station so the panels are North.

Here are a few images showing the initial orientation of the space station, and one showing it after I changed it so the panels face North:

This shows SpaceLab after initially entering LKO.  As you can see the panels are all fully exposed and facing Kerbol.

The plan was for the panels to follow Kerbol as SpaceLab went through its orbit, the natural rotation of the space station in relation to Kerbin insuring the panels would be pointing in the right direction at all times.

As Kerbol begins to appear over the horizon, the space station has automatically rotated while passing through the night side of the planet, and the panels are sitting in the best position to recharge the batteries during the next period of light.

Everything works fine and dandy while I'm focused on the space station, unfortunately this all stops when I jump to another vessel or the KSC.  The station's natural rotation freezes, and even if the panels are facing Kerbol, the batteries don't seem to charge.

SpaceLab's new orientation.  With half the panels not now fully exposed to the sunlight, unfortunately the science lab consumes more energy than can be produced.  However I should be able to fix that by launching a module with more panels, attaching it to the space station using a Klaw.  This still doesn't resolve the fact that everything "freezes" when I'm not focused on the space station unfortunately. 

However, as my first attempt at a "real" space station, ie one that was going to be of some benefit to my space program, I'm not totally disheartened by its failings.

 

[bewing]

The fact that you are using a modded older version of the game confuses things. Your game might not be behaving normally.

I do not see a battery. I do not see a probe core. I see that your lights are on, and that will use a little EC. 4 of the 1x6 panels will produce 6.8 EC at absolute max output when on the sunlit side of Kerbin, if all the panels are facing Kerbol squarely. When doing research, your station will probably be using about 5.1 EC.

So, for an experiment -- could you note your exact EC battery levels and your UT time, switch focus to some distant ship for exactly one game minute, switch focus back, and tell us the exact level of EC in your batteries?

 

[The Flying Kerbal]

Thanks for the answer brewing.

I'm at work at the moment so will carry out you experiment when I get home this evening.  However although you can't see any batteries or a probe core, rest assured they are there, it's just that I like to hide things like that by offsetting them inside the structure.

[Zhetaan]

5 hours ago, The Flying Kerbal said:

However although you can't see any batteries or a probe core, rest assured they are there, it's just that I like to hide things like that by offsetting them inside the structure.

Consider leaving the resource panel in the screenshot; that and the other UI elements will help to show that the station has sufficient control and power storage.  It's not that we don't believe you; it's that showing the information means we don't need to ask.

Your power situation unfortunately leaves something to be desired; if the panels only produce 6.8 EC/s at absolute maximum output and your lab consumes 5.1 at minimum output, then you will have problems because it means that your daytime recharge rate is at most 1.7 EC/s.  The closer you orbit Kerbin, the more of your orbit is spent in the dark, and if you do not have enough panel to charge the station in the day to make it last the night, then you will run out of power every orbit.  You can make your panel situation better by boosting to a higher orbit (one where the darkness time is one third or less of the orbital period), but while that means you spend less of a percentage of your orbit in darkness, it also increases the total time spent in darkness, which necessitates more batteries.

My suggestion to you is to dock a power module to the lower docking port (have docking ports on both ends so you don't lose your docking point) that consists of at least three of the 1.6 solar panels in a column arranged in trilateral symmetry (for a total of nine panels), a few Z-400 batteries (I prefer to arrange them between the solar panels), and preferably a level 2 or better probe core (that list starts with the Okto-2, I think).  The level-2 cores include normal/antinormal hold, which is helpful with docking and can be exploited for better power control, too.

If you set your station to normal (not north), then with the panel arrangement I described, you will never run out of power in daylight (I leave provision of sufficient batteries for night and eclipses to you); the minimum power output of a trilateral set is just over 1.5 times the maximum output of any one side, so each side needs to produce only two-thirds of your total.  If your current set of four can run the station in full sun, then you need two and two-thirds panels on each leg of a trilateral set, which is why I specify three.

That said, @bewing has a point:  because you're running 1.3.1 or earlier (the 2.5-m RCS tank gives it away), do please understand that if you really have found an EC bug, there's no official support for it.  We'll help you as much as we can, but the developers have moved on from this version.

[OHara]

What you've shown so far, FlyingK, could be consistent with usual behavior for KSP, versions 1.0−1.4.

As bewing said, while you are away the game does not simulate solar flux, but lets the battery level stay where you left it, and assumes the labs had power to convert data to science if there was charge when you left.  Assuming that holds true for your game, you could be noticing that the lab quickly drains the batteries when your just-right-sized solar panels are not oriented perfectly.

Satellites in low orbit keep a fixed orientation to the stars, under SAS or in time-warp while you watch them, but when you are somewhere else the game remembers their orientation relative to the planet [*], so if you come back half a day later the station has rotated 180° relative to the sun.   Thus Gargamel's advice to point the axis of panels along the north-south line.  (* I would call this a bug, but a minor one)

If you lift your station high enough, >250km over Kerbin,  the game leaves the station in fixed orientation relative to the stars while you are away.  That would leave your original design working well for about 1/4 of a year, until Kerbin orbits to the other side of the sun, taking your station with it.  Gargemel's advice helps here, too.

[The Flying Kerbal]

Ok guys, I'm back!   Apologies for not posting a reply last night, visitors came in unexpectedly and pushed the whole space program off schedule, did NASA have this problem when planning on sending Neil and the boys to the moon?

It looks like the charge does indeed freeze when I'm away from the station.  Ok it might actually jump up a point or two when I switch back, but that slight boost is the same whether I'm away for one minute or ten (an few alarms triggered and I had to deal with a couple of things during testing).

Yeah Zhetaan you're right about the lack of power generation.  As I said previously, my original plan had been to have the station orientated so the panels faced antinormal while passing over the daylight side of the planet.  This would also have made docking much easier as the docking ports are on both ends of the station.  I am indeed planning on launching a new module with more panels and additional batteries and attaching it to the side facing south using a Klaw.  That should resolve any problems the demand placed on my present generations system by the greedy science lab is creating when processing data.

Having tested how the recharging works while away from the space station, I have now turned off all science processing, recharged the batteries fully, and now started processing again as SpaceLab crossed the terminator and started its journey over the night side of Kerbin, now I'm not focused on it and will go back after it has started going over the sunlit side to see if the processed science has increased.

If there's a bug then I'm in trouble, but I'll cross that bridge when I come to it.  I have 1.4 and the DLC, but for some reason I just can't warm to it.  I have had problems with contracts not completing even though all test conditions had green ticks beside them, I think that hasn't helped.  So I'm still on 1.2, working on flying a Kerbal to Duna and bringing it home again.  Lifting the station into a higher orbit, would involve me sending a new module with an engine to propel it as I jettisoned the original and deorbited it.  It's doable but I would prefer to keep it in its current orbit if possible.

For those interested, here is a screenshot showing the UI and various figures:

Anyway, thanks to every one of you for taking the time to help me with this!

 

[Mahnarch]

What if you got a really long extension cord....

[The Flying Kerbal]

2 hours ago, Mahnarch said:

What if you got a really long extension cord....

That's just silly.  What happens for example, if a low flying aircraft accidentally cuts through the extension cord?  You really didn't think this one out, did you?