KSP Interstellar Extended Support Thread

[Wiowt]

@FreeThinker

 Magneto inertial engine  ia fusion? But in its desription it sais that it is also electric and needs additional reactor. Besides it stated that engine can use different propellants, isp depends on core temperature and engine can use lithium with isp ~5000. But in fact, it can use only lithium with isp ~2200.

Zpinch looks a bit broken. It gives only 40 kn of trust and only when i set trust around 15%.

Why lithium is only stored in cargo tanks? It is also a fuel.

And most strange thing: refregirator can make water from LqdWater)

Edited November 25, 2018 by Wiowt

[emiliofloris]

On 3/11/2018 at 5:10 PM, FreeThinker said:

Ah yes, I see now that the tweakscaleexponent for the InterstellarResourceConverter is completely missing

You should be able to realize the proper scaling by simply adding or editing any cfg file, and add the following text

TWEAKSCALEEXPONENTS
{
	name = InterstellarResourceConverter
	maxPowerPrimary = 3
	maxPowerSecondary = 3
}

please verify and I will add it to IFS in the next update

I ran into a similar issue, tried the fix but saw no change. Here is what happens:

I have four refrigerators at different scales. Power consumption works as expected, but output is the same for all four. It's not intake-limited, I can turn off one intake and production doesn't change. Another issue:

Time warping reduces production/sec. This seems to be a general problem with KSPIE, looking at the waste heat, MegaJoule and charged particle indicators you can see that the total capacity gets scaled up, for waste heat and charged particles in direct proportion to the time acceleration. The rate of change doesn't. Liquid Argon capacity stays the same, but production rate is scaled down. This seems very strange. Using HyperWarp or physics warp gives the same results.

A minor comment: What does "mT" stand for in the atmospheric intake? I suppose it's the same as "U", so production for Argon is 0.0093*Intake. But how does it relate to the next line?

And another one: Argon production is a lot more profitable than space tourism. In fact my main motivation to try out the refrigerator was rank greed.

 

 

Edited November 25, 2018 by emiliofloris

[xRei]

Hey, I've had an issue with power relays. Specifically, I have a reactor out in Kerbin synchronous orbit with an attached laser generator and a medium sized dish. The laser is generating in the vacuum UV. I also tested far UV and Red Light spectrums. Anyway the problem is that I later launched a double pivoted light mirror to relay the beam. The description of it says it works in 'the uv spectrum' so I assume the three UV beams I tried would work? Well, I couldn't seem to get it to actually relay the beam. I did make sure to click 'relay' on the light mirror for that craft before switching away from it.

As a note, direct LoS with the reactor does work, it's only the relay that I'm having trouble with.

I launched a craft with an inline thermal receiver which was in LoS to the relay but not the reactor (the relay has clear LoS to the reactor) but there was no incoming power. In the network info panel it does show both reactors in the relay network though. I took a screenshot but I couldn't get the forum to inline it, so here's a link: http://tinypic.com/r/2it546o/9

Am I misunderstanding how relays work, or how the light mirror works?

Oh, also on a semi-related note, I downloaded the last 2 or 3 updates for KSPI last night and noticed that the maximum power output of several reactors was decreased... mostly (exclusively?) the fusion reactors, but I couldn't find anything in the balance change notes about it. Was that an intended change? The max upgraded power output of the stellarator for instance dropped from ~15GW to 10GW.

Edited November 26, 2018 by xRei

[FreeThinker]

On 11/24/2018 at 10:49 PM, Wiowt said:

@FreeThinker

 Magneto inertial engine  ia fusion? But in its desription it sais that it is also electric and needs additional reactor. Besides it stated that engine can use different propellants, isp depends on core temperature and engine can use lithium with isp ~5000. But in fact, it can use only lithium with isp ~220.

11

Maximum isp is multiplied by the molecular mass ratio of lithium compared to Hydrogen, which is 0.577.  But Engine Maximum Isp should indeed be higher, it will be improved next release. But note that its one of the earliest fusion engines available in KSPIE, so don't expect too much

Edited November 26, 2018 by FreeThinker

[FreeThinker]

On 11/24/2018 at 10:49 PM, Wiowt said:

Zpinch looks a bit broken. It gives only 40 kn of trust and only when i set trust around 15%

3

Broken in what sense?

[Friznit]

Please forgive my noobishess but I'm struggling to get my head around the basic concepts.  Please can some kind soul provide or point me in the direction of some basic craft files demonstrating a few simple setups for mission profiles such as Mun, Duna, Long Range Get Me To Somewhere Else Just Not Here™?  I'm about half way through the CTT tech tree and have unlocked the Krusader and Thermal Ramjet nozzle and the Pebble Bed & Open Cycle Gas Core reactors.  Other than trying to get any meaningful dV compared to stock Engines with LFO, one of the biggest issues I'm having is cooling.  The guides and video tut's suggest slapping on various radiators until the Thermal Mechanics Helper shows green, but it seems to require the world's supply of graphine which I'm sure can't be right.  I'm probably missing something really basic but any help would be appreciated.

[Wiowt]

1 hour ago, FreeThinker said:

Broken in what sense?

When i set full trust it doesnt work (0 kn, 0 isp). Works only when i set ~15% trust

6 hours ago, FreeThinker said:

Maximum isp is multiplied by the molecular mass ratio of lithium compared to Hydrogen, which is 0.577.  But Engine Maximum Isp should indeed be higher, it will be improved next release. But note that its one of the earliest fusion engines available in KSPIE, so don't expect too much

But i can just use atilla instead of fusion inertial))) Atilla isp is better and it can use hydrogen(more efficient fuel)

Edited November 26, 2018 by Wiowt

[xRei]

1 hour ago, Friznit said:

Please forgive my noobishess but I'm struggling to get my head around the basic concepts.  Please can some kind soul provide or point me in the direction of some basic craft files demonstrating a few simple setups for mission profiles such as Mun, Duna, Long Range Get Me To Somewhere Else Just Not Here™?  I'm about half way through the CTT tech tree and have unlocked the Krusader and Thermal Ramjet nozzle and the Pebble Bed & Open Cycle Gas Core reactors.  Other than trying to get any meaningful dV compared to stock Engines with LFO, one of the biggest issues I'm having is cooling.  The guides and video tut's suggest slapping on various radiators until the Thermal Mechanics Helper shows green, but it seems to require the world's supply of graphine which I'm sure can't be right.  I'm probably missing something really basic but any help would be appreciated.

To start off it'd likely be easiest to use one of the pre-made engines rather than using the reactors and nozzles. You could aim for the Timerwind for example, which is a powerful rocket engine. If you want highly efficient dv and don't mind mediocre thrust, you could take a look at the 'Lightbulb' engine or the Open Cycle Gas Core Engine.

For radiators you actually don't need to worry overly much about getting the numbers green in the VAB. Those numbers assume 100% uptime on the engine/reactor. Most of the engines will generate little heat while idle, so the number of radiators needed is minimal. Some reactors do have minimum throttles though, like the molten salt reactor which is 30% iirc. Most of the fusion engines and reactors will run cool until you start thrusting.

That said, unlocking more nodes in the thermal management branch will passively improve all your graphite radiators by a significant margin. By the time you get to the last 2 in the line, even small numbers of radiators will give you green in the VAB, excepting the most aggressively hot reactor and electric engine setups. So, if you want to make your life easier with heat, just plonking down some science on the next node of the branch will be a benefit.

If you still wanna try a reactor/nozzle combo, you could try something simple to start with. Take a pebble bed(which is the reactor equivalent to the timberwind) and stick a nozzle on it. 4 medium extendable graphite radiators should be plenty for that set up, though the pebble bed does get worse as it heats up, which is I believe unique to that reactor, but again it only becomes a problem if you're thrusting constantly or attach a generator to it that's being constantly used. Anyway, supply it with whatever kind of fuel you can. Some reactors and nozzles can't use certain fuel types, but I think the pebble bed and krusader can use liquid fuel. If not, just play around with the 'next propellant' button til you land on sometime good. For starting out, I'd recommend looking for a fuel which is dense (unlike hydrogen, which needs huge tanks to get decent delta v), while still being reasonably good isp. If you look at the window while switching fuels you'll see numbers for expected isp and thrust. For isp, anything above 500 is decent for nuclear reactors. The Open Cycle Gas Core reactor will have much better isp but weaker thrusts than the pebble bed, generally.

To start out, I'd avoid electric engines. They require more set up and unlike the other reactor and nozzle combos, they will murder you with heat and are very fussy to get working with good thrust. The electric engines are more for super efficient(high isp) propulsion, and generally suffer for thrust. In fact, that's a general maxim for most of the tech tree. Things with great ISP tend to suffer for thrust and vice versa.

As a final note, attaching generators to reactors to make electricity will produce a lot of heat if that electricity is being used. Thermal generators are probably the worst offender since their efficiency plummets as waste heat accumulates (and it will no matter how many radiators you stuff onto the ship). Charged Particle converter is unquestionably superior in basically every way, but is harder to use because.. you need charged particles rather than thermal energy, which only comes in abundance once you start getting fancy with fusion reactors and stuff.

Edited November 26, 2018 by xRei

[shifty303]

I recently noticed the wiki mentions research multipliers for the science laboratory when landed on various planets that are higher than when in orbit. Are the multipliers calculated before the research starts? I landed an existing lab that was in orbit around Minmus but didn't see an increase in science per day once landed on Minmus.

[FreeThinker]

On 11/25/2018 at 8:09 PM, xRei said:

Oh, also on a semi-related note, I downloaded the last 2 or 3 updates for KSPI last night and noticed that the maximum power output of several reactors was decreased... mostly (exclusively?) the fusion reactors, but I couldn't find anything in the balance change notes about it. Was that an intended change? The max upgraded power output of the stellarator for instance dropped from ~15GW to 10GW.

Yes, it is intended. Fusion Engine main advantages are higher isp and higher fuel energy density and fuel economy, the main disadvantages are lower power energy densities.

On 11/25/2018 at 4:06 PM, emiliofloris said:

A minor comment: What does "mT" stand for in the atmospheric intake? I suppose it's the same as "U", so production for Argon is 0.0093*Intake. But how does it relate to the next line?

mT stands for metric ton

[ss8913]

@FreeThinker I started a non-warp mission to Duna maybe a week or two ago... couple of updates have dropped since then.. this thing is using plasma nozzles on positron antimatter reactors, with hydrazine propellant.. this thing was fast and powerful and could burn all day when it *left*... something seems to have changed... it runs white-hot almost as soon as I hit the throttle, and the heat starves the reactors at different rates, so I have to use differential thrust to even keep it pushing 3/m/s/s in a straight line.  this thing was capable of at least 5G sustained when it left Kerbin.. what changed?  is this supposed to be how it is or is the heat curve way off?

[FreeThinker]

@ss8913 Well the main change is that the plasma nozzle now requires a significant amount of electric power, (which in the case of positron antimatter might be to high). Perhaps power production on your vessel isn't very efficient, causing the whole system to overheat. To be sure, could you make a screen dump of your kspie power management screens, which include waste heat production and consumption

Edited November 28, 2018 by FreeThinker

[ss8913]

1 hour ago, FreeThinker said:

@ss8913 Well the main change is that the plasma nozzle now requires a significant amount of electric power, (which in the case of positron antimatter might be to high). Perhaps power production on your vessel isn't very efficient, causing the whole system to overheat. To be sure, could you make a screen dump of your kspie power management screens, which include waste heat production and consumption

that makes sense.. the only 2 sources of electrical power are a 3.75m nuclear reactor from MKS, which MM-patches to behave like a KSPIE reactor... and 4 400% scaled PB-NUK generators on my little science dropship that goes along with the main craft.. it's probably running that 3.75m MKS reactor+generator at full capacity now, which the craft didn't need to do when it was launched.
I did manage to undock, flip, and re-dock my lander, so i can use the lander engines to get home - positron reactors + Krusader nozzles, which are thermal, and were unaffected by the change... got everyone back to Kerbin orbit, I'll try to recreate the craft with better electrical capabilities and see if I can't solve the thermal issue; I have some fairly big radiators on this thing already, there may be a scaling problem.  will let you know if I can/can't make it run cool enough to be functional.

[FreeThinker]

4 hours ago, ss8913 said:

that makes sense.. the only 2 sources of electrical power are a 3.75m nuclear reactor from MKS, which MM-patches to behave like a KSPIE reactor... and 4 400% scaled PB-NUK generators on my little science dropship that goes along with the main craft.. it's probably running that 3.75m MKS reactor+generator at full capacity now, which the craft didn't need to do when it was launched.
I did manage to undock, flip, and re-dock my lander, so i can use the lander engines to get home - positron reactors + Krusader nozzles, which are thermal, and were unaffected by the change... got everyone back to Kerbin orbit, I'll try to recreate the craft with better electrical capabilities and see if I can't solve the thermal issue; I have some fairly big radiators on this thing already, there may be a scaling problem.  will let you know if I can/can't make it run cool enough to be functional.

Ah yes, that explains it. The main problem here is that there is insufficient power to power the magnetic nozzle,  causing  the magnetic containment field to be too weak to maintain the plasma, causing the plasma to get in contact with nozzle and reactor, causing the whole system to heat up, causing your radiators to get white hot and the overheat prevention mechanic to kick in to prevent the reactor for meltdown, causing the reactor to produce very little power and therefore thrust. Although explainable, the engine should not ask for full power when there is insufficient electric power for the magnetic to function.

Notice that Positron Antimatter reactor can now also be connected directly to a Thermal Nozzle (that does not require power) which will use all available reactor power. The trade of is that the maximum isp is limited 7000s (similar to gas core ) and it generates more wasteheat 

Edited November 28, 2018 by FreeThinker

[Friznit]

I could have sworn I read a reply to my request for help above.  Some very friendly person took the trouble to give useful guidance on how to get started but the post seems to have disappeared.  Unless I'm going mad, which to be honest quite likely under the circumstances.  Did this get moves to a more appropriate thread that I'm missing?

Edit: Nevermind - forum's behaving differently to what I'm used to!

Edited November 28, 2018 by Friznit

[xRei]

On 11/28/2018 at 12:53 PM, Friznit said:

I could have sworn I read a reply to my request for help above.  Some very friendly person took the trouble to give useful guidance on how to get started but the post seems to have disappeared.  Unless I'm going mad, which to be honest quite likely under the circumstances.  Did this get moves to a more appropriate thread that I'm missing?

Edit: Nevermind - forum's behaving differently to what I'm used to!

Yeah, I replied and my comment got deleted.. for whatever reason. If you still need it I can repeat what I said in a private message.

[FreeThinker]

1 hour ago, xRei said:

Yeah, I replied and my comment got deleted.. for whatever reason. If you still need it I can repeat what I said in a private message.

I can confirm I saw the post as well and now I'm confused why it was removed as well. Possibly someone attempted to move or delete another post after it and accidentally removed the post in question by accident. I contacted a mod and hope it can be restored.

[Snark]

Hi folks,

Regarding @xRei's supposedly "missing" post, responding to @Friznit's question.  It's still there, alive and well.  I assume you're referring to this?

On 11/26/2018 at 1:35 PM, xRei said:

To start off it'd likely be easiest to use one of the pre-made engines rather than using the reactors and nozzles. You could aim for the Timerwind for example, which is a powerful rocket engine. If you want highly efficient dv and don't mind mediocre thrust, you could take a look at the 'Lightbulb' engine or the Open Cycle Gas Core Engine.

For radiators you actually don't need to worry overly much about getting the numbers green in the VAB. Those numbers assume 100% uptime on the engine/reactor. Most of the engines will generate little heat while idle, so the number of radiators needed is minimal. Some reactors do have minimum throttles though, like the molten salt reactor which is 30% iirc. Most of the fusion engines and reactors will run cool until you start thrusting.

That said, unlocking more nodes in the thermal management branch will passively improve all your graphite radiators by a significant margin. By the time you get to the last 2 in the line, even small numbers of radiators will give you green in the VAB, excepting the most aggressively hot reactor and electric engine setups. So, if you want to make your life easier with heat, just plonking down some science on the next node of the branch will be a benefit.

If you still wanna try a reactor/nozzle combo, you could try something simple to start with. Take a pebble bed(which is the reactor equivalent to the timberwind) and stick a nozzle on it. 4 medium extendable graphite radiators should be plenty for that set up, though the pebble bed does get worse as it heats up, which is I believe unique to that reactor, but again it only becomes a problem if you're thrusting constantly or attach a generator to it that's being constantly used. Anyway, supply it with whatever kind of fuel you can. Some reactors and nozzles can't use certain fuel types, but I think the pebble bed and krusader can use liquid fuel. If not, just play around with the 'next propellant' button til you land on sometime good. For starting out, I'd recommend looking for a fuel which is dense (unlike hydrogen, which needs huge tanks to get decent delta v), while still being reasonably good isp. If you look at the window while switching fuels you'll see numbers for expected isp and thrust. For isp, anything above 500 is decent for nuclear reactors. The Open Cycle Gas Core reactor will have much better isp but weaker thrusts than the pebble bed, generally.

To start out, I'd avoid electric engines. They require more set up and unlike the other reactor and nozzle combos, they will murder you with heat and are very fussy to get working with good thrust. The electric engines are more for super efficient(high isp) propulsion, and generally suffer for thrust. In fact, that's a general maxim for most of the tech tree. Things with great ISP tend to suffer for thrust and vice versa.

As a final note, attaching generators to reactors to make electricity will produce a lot of heat if that electricity is being used. Thermal generators are probably the worst offender since their efficiency plummets as waste heat accumulates (and it will no matter how many radiators you stuff onto the ship). Charged Particle converter is unquestionably superior in basically every way, but is harder to use because.. you need charged particles rather than thermal energy, which only comes in abundance once you start getting fancy with fusion reactors and stuff.

Here's what's going on:  The post got "voted up".  That made it automatically jump up to the top of the thread.  Since this thread is over 130 pages long and started nearly two years ago, naturally nobody looking at the recent-posts end of the thread thought to look back there, which means it seemed to "disappear".

Additional discussion in spoiler, the upshot of which is that this particular thread is probably ill-suited to the tech-support forum's format, which causes problems like this.

Spoiler

The forum software allows for two different types of "format" for the various subforums.  These formats could be referred to as:

• Standard (suitable for long-running discussion on a topic)
• Q&A (suitable for short, "focused" threads where the OP is a question and the posts in the thread are answers for that question)

Most of the subforums here at forum.kerbalspaceprogram.com are in the "standard" format.  This is a plain-vanilla format that simply presents all posts within a thread in chronological order of posting.  It's the forum behavior that most folks expect, and it's well-suited for long-running discussion on a topic.  For a thread in a "standard" forum, the thread OP is presumed to set some particular topic, which the various posters in the thread can then discuss ad infinitum.

However, there are a few subforums here-- specifically, "Gameplay Questions" and the "Technical Support" subforums-- which follow the "Q&A" format.  This format serves a very different purpose.  For a Q&A forum, the OP is assumed to be a specific question.  The presumption is that the question has some answer, and that the discussion is basically done when an answer is found.  The posts in the thread are presumed to be answers to the OP's question; the focus is on responding to that question.

To better support that goal, the Q&A format has a "vote up" feature.  Anyone who sees an "answer" post in a Q&A forum can "vote it up" by clicking a little up-arrow icon to the left of the post.  This causes the forum to display posts out of chronological order:  instead of simply posting first-come-first-served, it shows the top-voted posts first, up at the top of the thread.  Posts that have equal number of votes (including zero) are shown in chronological order.

It makes sense, when you think about it.  Q&A threads are presumed to be short, by design:  an OP posts a question, and then people post their answers until a consensus is arrived at which ones "best" answer the question, and then it stops.  Usually they're no more than a page or two long for the whole thread.  And it makes sense to bubble up the "best" answer to the top of the thread, from the point of view of the OP (and any subsequent visitors who might have the same question):  there's the "question" post as the OP, and there's the "answer" post right after it.  Saves people from having to rummage through a long thread to find the answer.

The problem here is that this particular thread is ill-suited to the forum's Q&A format.  Because the Q&A format assumes that there is one question per thread, and that question is the OP.  That's not what this thread is.  This thread is a long-running discussion.  Yes, it has questions in it... but that's questions, plural.  Lots of questions distributed over time.

This means that if anyone ever clicks the "vote up" button next to a post... it'll "jump" up to the top of the thread, where nobody thinks to look, which means everyone thinks it vanished.  It becomes practically unfindable, thus exactly precisely defeating the whole purpose of the feature, which is supposed to make answers easier to find in the thread rather than harder.

I'd suggest that a better home for this thread would be under Add-on Discussion-- not because of "topicality", but simply because of the format of this thread is better suited there.  As long as you keep the thread here in Technical Support (which has a "Q&A" format that doesn't work well for it), then this kind of problem is likely to keep recurring.  However, it's @FreeThinker's thread, so it's up to him-- please let us know if you'd like us to move the thread over to Add-on Discussions, which would prevent this type of problem from ever happening again.

[FreeThinker]

10 minutes ago, Snark said:

@xRei@Friznit

Here's what's going on:  The post got "voted up".  That made it automatically jump up to the top of the thread.  Since this thread is over 130 pages long and started nearly two years ago, naturally nobody looking at the recent-posts end of the thread thought to look back there, which means it seemed to "disappear"

 

Lol, I wasn't even aware something could be upvoted. Is this a new feature or something?

[Snark]

1 minute ago, FreeThinker said:

Lol, I wasn't even aware something could be upvoted. Is this a new feature or something?

Well, if by "new" you mean "since we switched to the new forum software a few years ago", then yes, it's "new" in that sense. 

[FreeThinker]

25 minutes ago, Snark said:

@Friznit

Additional discussion in spoiler, the upshot of which is that this particular thread is probably ill-suited to the tech-support forum's format, which causes problems like this.

1

I agree, but I never actually made this poll thread, it was another moderator which accidentally moved this thread from development to support and converted it into a poll. Because it was during the time people all of the forum were losing the discussion threads, I was afraid of this too so I kept it this way, never realizing it would behave fundamentally different. If you could convert it into a regular post (without poll format, but keep it in support), that would be perfect. THat way post will no longer disappear to the top

Edited November 30, 2018 by FreeThinker

[Snark]

13 minutes ago, FreeThinker said:

If you could convert it into a regular post (without poll format, but keep it in support), that would be perfect

Just to be clear, when you use the word "poll" here, I assume you're referring to what I'm calling "Q&A format"?  Because a "poll" is a very specific, other kind of post (that's the kind where someone posts something like "What's your favorite planet?" and then gives a set of multiple-choice questions that people can submit their responses, that sort of thing).  Something completely different, and I assume that's not what you're talking about here.  If I'm correct in thinking that, best to avoid using the term "poll", it'll just cause confusion.

Unfortunately, that's not possible.  Whether a thread is in "standard" or "Q&A" format is a property of the forum where it's located, not a property of the thread itself.

• If a thread is located in a Q&A subforum, then the thread will have the Q&A format, with "vote up" buttons.
• If a thread is located in a "standard" (i.e. not Q&A) subforum, then the thread will be the way you want it, in simple chronological order.

So basically you have two choices.  Either leave the thread here, in which case this type of problem is bound to recur in the future; or else move it to a "standard" format subforum, like Add-on Discussions, in which case the Q&A features will go away and it'll just be chronological the way you want it.

If it were my thread, I'd move it-- just my two cents.  But it's your thread, so I leave it up to you.

[Friznit]

Thanks Snark - I found it on the front page.  Either way, many thanks to @xRei for your helpful insights into getting me started.  Let's say I've lobbed a 60T or so upper stage into LKO, is there a go to fuel for high ISP to get to Somewhere Else™ or do I just keep hunting for the optimal triumvirate of Fuel Density, TWR and ISP to suit my mission profile?  i assume it's the latter approach given there are so many variables and preferences.  LH2 does require very...bulbous ships (and no I'm not fat shaming your rocket)

[FreeThinker]

4 hours ago, Snark said:

Just to be clear, when you use the word "poll" here, I assume you're referring to what I'm calling "Q&A format"?  Because a "poll" is a very specific, other kind of post (that's the kind where someone posts something like "What's your favorite planet?" and then gives a set of multiple-choice questions that people can submit their responses, that sort of thing).  Something completely different, and I assume that's not what you're talking about here.  If I'm correct in thinking that, best to avoid using the term "poll", it'll just cause confusion.

Unfortunately, that's not possible.  Whether a thread is in "standard" or "Q&A" format is a property of the forum where it's located, not a property of the thread itself.

• If a thread is located in a Q&A subforum, then the thread will have the Q&A format, with "vote up" buttons.
• If a thread is located in a "standard" (i.e. not Q&A) subforum, then the thread will be the way you want it, in simple chronological order.

So basically you have two choices.  Either leave the thread here, in which case this type of problem is bound to recur in the future; or else move it to a "standard" format subforum, like Add-on Discussions, in which case the Q&A features will go away and it'll just be chronological the way you want it.

If it were my thread, I'd move it-- just my two cents.  But it's your thread, so I leave it up to you.

Ok I understand, lets get this fixed and move it to discussion thread as you suggested.

[xRei]

3 hours ago, Friznit said:

Let's say I've lobbed a 60T or so upper stage into LKO, is there a go to fuel for high ISP to get to Somewhere Else™ or do I just keep hunting for the optimal triumvirate of Fuel Density, TWR and ISP to suit my mission profile?  i assume it's the latter approach given there are so many variables and preferences.  LH2 does require very...bulbous ships (and no I'm not fat shaming your rocket)

LH2 is usually(always?) the superior choice for ISP, and it has good thrust, but as you pointed out it requires huge tanks because it has crappy density. If the awkwardness of the tanks isn't an issue, LH2 is always a solid choice. If you play around with the ISRU stuff that comes with the mod pack, LH2 is also fairly easy to create in situ, so that's another benefit. If you have mods that let you create vessels in orbit (Like Extraplanetary launchpads), even better, since then you don't have to care about lugging those huge tanks into orbit.

But if you want only density, stuff like kerosene, liquid fuel, HTP are all pretty good. Even monoprop. Some of the fuels come with better thrust even than LH2. I use LF and HTP a lot when I can get away with it though. The hybrid mixture fuels also tend to offer great thrust when you have a reactor/combo that works with them. That's your FUELNAME-lox fuels (fuel + liquid oxygen), like hydrolox. The biggest issue with a lot of those denser fuels is that they aren't always compatible with some of the more ISP/efficient reactor types, which tend to rely on stuff like noble gasses, such as xenon, krypton, etc. Many of those reactors can also use Liquid CO2, which has decent density and thrust. Some can use HTP also. As you said, you kind of have to play around with it each time you design a craft. There's a lot of variables involved since many of the reactors and nozzles can only use certain fuels, and some of the tech nodes will unlock additional fuel choices later on(IIRC). LH2 is the gold standard since it can be used with almost everything and the ISP is always excellent... if it just wan't for that awful density..

Beware liquid Xenon, it's insanely expensive.

For simplicity sake, I also really recommend the MIC Fusion Rocket for efficiency. It's actually one of my favorite engines in the game. It needs only 2 things in abundance: a small bit of power to run, and lithium for fuel. Lithium is pretty dense fuel, but requiring megawatts of power to run does mean you'll need a reactor on the ship, but the requirements are small, so it doesn't need to be a big reactor. IIRC it's around abouts ~30MW for the unupgraded, 2.5m fusion rocket. The mod comes with a nuclear reactor that has a built in generator (it sits in the utilities submenu) which is often what I use early on in career mode for cheap MWs. The storage tanks you need for lithium are found in the fuel storage tech line. Another nice thing about this rocket is that it has upgrade tech nodes all over the place, so as you unlock more tech it's being upgraded passively all the time. It's efficiency is high enough that with enough lithium you can go anywhere in the Kerbol system with a moderate sized payload pretty easily, even before it's fully upgraded.

Quick note about generating electrical power: right click on the generator(or reactor/generator combo) and it'll show you what the efficiency is expected to be. The efficiency of the normal generator starts really low, and as you upgrade tech nodes at the bottom of the tree, it increases. But importantly, you have to remember to multiply the maximum expected power of the reactor you're using (in GW or MW) by that number, and that's how much actual electricity you'll generate. So if your nuclear reactor says it produces 100 MW total output and your efficiency is currently 40%(0.4), expect less than 40 MW of actual power. I say expect less because generators perform worse as temperature rises, and it very quickly will while it generates electricity. Upgrades help a lot though. And as I mentioned in the other post, the charged particle converter is much better since it's efficiency doesn't drop with temperature increases, but those charged particles are harder to get.

The moral of the story is that if you are using the normal generator for powering your engines, bring enough radiators to offset the at least some of the heat. For the MIC Fusion Rocket, something like 4 medium graphite radiators should be okay. If the generator starts producing less power than you need for maximum thrust with your fusion rocket, the rocket will automatically throttle itself down, so it'll still work, just less effectively. I'd say a general rule of thumb is that you want at least twice as much expected power from your generator than what you need for the rocket's fusion maintenance. Maybe 3x as much at low tech levels if you want be to be sure that you can run the engine at max thrust near constantly.

Later on you can use the colliding beam fusion reactor which uses charged particles to make highly efficient electrical power. It's all in one so you don't need to attach the converter. It starts off large in the VAB, but upgrades will allow you to shrink it down. For mid-late game tech tree, this is one of the best ways to get easy, carefree power.

So if you want 30MW of power and you currently have 30% efficiency, then a reactor which makes 300 mw will have a max electrical output of 100mw/mjoules (300 x 0.3), and assuming heat drops the efficiency of the generator down to 11%, you'd still have 33MW of electrical power. So take your MIC Fusion Rocket, include your choice of reactor/generator for power, 4 graphite radiators and a big tank of lithium. That's enough to shove a 2.5 command pod, a science module, a lander and some other crap to just about anywhere in the system.

Also don't forget that you can time warp with many of the engines in KSPI to offset dealing with obnoxiously low thrust.

 

Edited November 30, 2018 by xRei