Are Photovoltaic Panels less efficient on Minimus? ... If so, why?

[JoeSchmuckatelli]

I built and tested a rover at KSC - it happily drove all over the place at high speed / efficiency - it was like I couldn't lose power.

Got it onto Minimus - after a LOT of tries (couldn't get a rocket into orbit with enough juice left over to get me to Minimus orbit).  What I discovered, however, is that my lander wants to lose power very quickly.

Now - it seems to me that Minimus should be getting effectively the same light output from the sun as Kerbal (it's in Kerbal's SOI, afterall).  So, why the loss of performance?

 

(... and no, I'm not operating on the shadowed side of the moon).

[A35K]

Are you sure the panels weren't obstructed by something on the ship itself? Maybe if it was near the poles (or near sunset/rise) the sun was coming at an angle to the panels, meaning they get less power.

[sal_vager]

Yep, panel and sun angle is a factor, also, moved to gameplay questions

[Snark]

Try right-clicking on a panel and see what it says about power production, that should provide a clue. Try driving in a circle and see how the numbers change with the sunlight angle.

For rovers on vacuum worlds like Minmus, I like to use the rotating solar panels, they do a much better job of staying pointed at the sun so that I've got full operational power as long as the sun is somewhere in the sky.  What I like to do is use a pair of the 1x6 panels, mounted slightly above the horizontal (say, 30 degrees) so that they make a V.  That's low enough that they're reasonably efficient about catching the sun, but high enough that they're less likely to bump into terrain as my rover goes tumbling about.

Also, it's a good idea to load up rovers with plenty of batteries, so that (for example) if you have to go up a hill where your panels don't have a good sun angle for a while, you don't run out of juice halfway up.

 

Edited December 17, 2015 by Snark

[JoeSchmuckatelli]

Yeah, I didn't put any batteries on it, given its charge and KSC performance.  I do have panels on all 4 sides and the top.  

 

Over all its been my biggest accomplishment just to land it, but over all, the mission has been particularly disappointing - rover not working and funds in the toilet

[Deadpangod3]

It may also be possible that with Minmus's large orbit that you may see a TINY fluctuation in power generation on opposite sides of the orbit, but to be a problem would require you to just barely have enough power generation in the first place...

[linuxgurugamer]

9 minutes ago, Deadpangod3 said:

It may also be possible that with Minmus's large orbit that you may see a TINY fluctuation in power generation on opposite sides of the orbit, but to be a problem would require you to just barely have enough power generation in the first place...

I doubt that.  Minmus's orbit may be large compard to the Mun, but it is miniscule compared to the distance to the sun

[Snark]

2 hours ago, JoeSchmuckatelli said:

Yeah, I didn't put any batteries on it, given its charge and KSC performance.  I do have panels on all 4 sides and the top.  

Over all its been my biggest accomplishment just to land it, but over all, the mission has been particularly disappointing - rover not working and funds in the toilet

Ouch.  Yes, you should definitely have batteries for any rover, it's an absolute must.

Beware of "I tested it at KSC"-- if you happened to be testing it when the sun was at a particularly favorable angle (like straight overhead), it could give misleading results.

It's not just a question of "I have panels on every side" -- the angle matters, too.  The rotating panels are so much better than the static ones, because they don't just rotate so that they're in sunlight, but that they're straight at the sunlight so they give max power.

Rovers need a lot of electricity.  They need a lot of solar power to keep going.  To get the same power output as a single rotating solar panel, you'll need a whole lot of OX-STAT panels, and still may not be as reliable.

If you're short on funds and need a boost:  one handy and easy source of ready cash is the "science data from space around <some place you've been>" contract.  Just leave a single satellite parked around each planet or moon you visit, and make sure it has an antenna, solar panels, and (say) a thermometer.  That way, whenever you get the contract, you just hop over to the satellite, take a quick measurement, get the cash.  Takes like 30 seconds and just a few mouse clicks, and is totally repeatable.

Edited December 17, 2015 by Snark

[JoeSchmuckatelli]

26 minutes ago, Snark said:

 

If you're short on funds and need a boost:  one handy and easy source of ready cash is the "science data from space around <some place you've been>" contract.  Just leave a single satellite parked around each planet or moon you visit, and make sure it has an antenna, solar panels, and (say) a thermometer.  That way, whenever you get the contract, you just hop over to the satellite, take a quick measurement, get the cash.  Takes like 30 seconds and just a few mouse clicks, and is totally repeatable.

Hmmm.  I've tried this with both my Munar and Minimus Sattelite - and I've been getting 25 science (if kept) 0 if transmitted - so I've not been transmitting anything.  Wasn't aware I'd get anything by 'burning' the data.

[Snark]

3 minutes ago, JoeSchmuckatelli said:

Hmmm.  I've tried this with both my Munar and Minimus Sattelite - and I've been getting 25 science (if kept) 0 if transmitted - so I've not been transmitting anything.  Wasn't aware I'd get anything by 'burning' the data.

So there are two things.  One is getting science, one is getting cash.

If you want to get science, don't transmit, and bring the satellite physically back to Kerbin to retrieve it.  But that only works once.  If you take a temperature measurement in near-Mun space, and you take it back to Kerbin and get credit for it, then you're not going to get science for subsequent temperature measurements in near-Mun space.  You've mined it out.  (Okay, you can get a little, but it's subject to harsh diminishing returns and not worth the effort IMHO.)

What I just said in my previous post, however, was for getting cash, to satisfy a contract.  "Science data from space around X" is a fairly frequently recurring type of contract.  By all means, the first time you go to the Mun or wherever, keep all the science and bring it back to Kerbin for science points you can use to unlock the tech tree.

But subsequently, you're still going to see "science data from space around the Mun" contracts popping up, even though you have already gotten all the science possible from munar orbit.  To satisfy the contract, all you need to do is transmit the science, even if it's worth 0 points because you already returned that science result.  And to do that, you don't have to launch a new satellite, and you don't have to bring anything physically back.  Just switch to the satellite, take a temperature (or whatever) measurement, transmit it, bang you're done.  Sure, the contract is probably not worth a ton of money (maybe 30-40K for space-around-Mun), but heck, not a bad return for 30 seconds of effort.

[FancyMouse]

I thought the bug that dark-side of Minmus still receives solar power is still not fixed?

[Drew Kerman]

9 hours ago, linuxgurugamer said:

I doubt that.  Minmus's orbit may be large compard to the Mun, but it is miniscule compared to the distance to the sun

I've seen at times my Minmus Comsats orbiting at 1,150km produce 2.01Ec/s while they are rated at 2Ec/s at Kerbin. Dunno if this would be noticeable from the surface of Minmus tho

[NathanKell]

If exposure is the same between two solar panels (i.e. sun at the same angle in both cases), then their charge rate will only vary based on:

1. If there's atmosphere (atmosphere decreases incoming solar flux)

2. The skin temperature of the panel (hotter panel = lower efficiency).

If---if--the exposure is the same in both cases for you, sounds like the issue might be that the panels in space--with no atmosphere to convect with and cool in--heat up a lot and become less efficient.

[MaverickSawyer]

3 hours ago, Gaiiden said:

I've seen at times my Minmus Comsats orbiting at 1,150km produce 2.01Ec/s while they are rated at 2Ec/s at Kerbin. Dunno if this would be noticeable from the surface of Minmus tho

 

10 minutes ago, NathanKell said:

If exposure is the same between two solar panels (i.e. sun at the same angle in both cases), then their charge rate will only vary based on:

1. If there's atmosphere (atmosphere decreases incoming solar flux)

2. The skin temperature of the panel (hotter panel = lower efficiency).

If---if--the exposure is the same in both cases for you, sounds like the issue might be that the panels in space--with no atmosphere to convect with and cool in--heat up a lot and become less efficient.

Yeah, I've seen slightly higher-than-expected performance from supercooled (-30*C or colder) panels. It's usually ~0.01-0.05, depending on the situation and the size of the panels. On some of the Near Future panels (100 EC/sec), I've gotten almost an extra tenth of an EC per second from cooling... but it's not worth the power required to do that. 

Edited December 18, 2015 by MaverickSawyer

[linuxgurugamer]

8 hours ago, Gaiiden said:

I've seen at times my Minmus Comsats orbiting at 1,150km produce 2.01Ec/s while they are rated at 2Ec/s at Kerbin. Dunno if this would be noticeable from the surface of Minmus tho

That could simply be floating point error.

Also, were those Comsats closer to the sun or further away?  Look for the difference on the same panel, in different parts of the orbit

Edited December 18, 2015 by linuxgurugamer

[Drew Kerman]

3 minutes ago, linuxgurugamer said:

That could simply be floating point error.

Also, were those Comsats closer to the sun or further away?  Look for the difference on the same panel, in different parts of the orbit

I considered floating point, but the Comsats were indeed showing this when Minmus was orbiting closer to the sun than Kerbin. The math is pretty precise for all this, out to many more than two places in the game. At worst numbers in the game get rounded out to like 10 decimal places (at least that's what kOS puts out)

[linuxgurugamer]

2 hours ago, Gaiiden said:

I considered floating point, but the Comsats were indeed showing this when Minmus was orbiting closer to the sun than Kerbin. The math is pretty precise for all this, out to many more than two places in the game. At worst numbers in the game get rounded out to like 10 decimal places (at least that's what kOS puts out)

But what were they showing on the opposite side of the orbit?

[cantab]

Illumination angle has been well covered. Now that the rover is on Minmus, the most obvious solution is simple: wait until the Sun shines on the solar panels more directly. Less obviously, consider disabling the motors on some of the wheels. Chances are two-wheel-drive will suffice. If that still doesn't help, you'll probably just have to keep tapping the forward instead of holding it down.

Of course driving on Minmus presents other challenges anyway.

[JoeSchmuckatelli]

5 hours ago, cantab said:

...

Of course driving on Minmus presents other challenges anyway.

Yeah, I noticed.  It's like the ground has the consistency of talc.

[Drew Kerman]

21 hours ago, linuxgurugamer said:

But what were they showing on the opposite side of the orbit?

I never checked 

[linuxgurugamer]

1 hour ago, Gaiiden said:

I never checked 

Untili you do, you can't be sure.  It would be easy enough to test.  Send up a comsat using Hyperedit to the orbit, warp until the satellite is in the proper location and check it, then warp to the other side of the orbit and checkagain.

[Wemb]

On 17/12/2015 at 9:23 PM, Snark said:

What I just said in my previous post, however, was for getting cash, to satisfy a contract.  "Science data from space around X" is a fairly frequently recurring type of contract.  By all means, the first time you go to the Mun or wherever, keep all the science and bring it back to Kerbin for science points you can use to unlock the tech tree.

Yup and once you have the tech to put decent satellites up (not exactly sure which item on the tech tree unlocks this, but it's not just the stayputnik), they you will get a lot fo satellite launch missions - and for this it's definitely worth the time to develop an optimised launch vehicle that puts one (or more!) up into LKO with the minimal amount of rocket.  Satellites can be very lightweight compared to a manned mission and with a spark engine and a sensibly small fuel tank can pootle around Kerbin and it's moons and are a cheap (if dull) way to acquire cash.  

Wemb