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New Parts to reduce part count


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KSP's main limitation is a slow play speed due to a high part count, so I think we could use some new parts that can replace smaller parts that are commonly used in multiples:

#1) Larger jet engines, reaction wheels, and large diameter LF tanks

#2) Larger wings and control surfaces... no, the Big-2 and FAT-455 are not big enough for me :p

Breaking ground specific:

#3) quad blades for prop/fan/heli blades. I'm thinking that if you were to place these with 2 fold radial symmetry, it would look (and behave) like 8 fold symmetry of the normal blades. A BG motor could thus be 3 parts instead of 9 (when you need to use a lot of blades)

#4) Larger batteries (3.75m ones, double thickness ones), larger RTGs: Now with Breaking Ground, in some of my designs I use 12 heavy rotors... these consume A LOT of power.

In my last reusable eve cargo shuttle, I had 26 large batteries, 12 heavy rotors, 6? RTGs, and 12x8 = 96 fan blades.

Implementing 3.75m batteries that store about 3x more EC (they can be a bit thicker, for the same EC/volume and mass), would save 17 parts. Implementing the quad blad suggestion would lower the blade count to 12x2=24 instead of 12x8= 96, and would save 72 parts.

With these suggestions, many of my 300 or so part designs would come down to 200 or so part counts, and the game would play much smoother

 

Edited by KerikBalm
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On 5/31/2020 at 11:12 PM, KerikBalm said:

#2) Larger wings and control surfaces... no, the Big-2 and FAT-455 are not big enough for me :p

The FAT-455 are known to shear off during high G turns because it is subject to stronger aero force but its attachment is no stronger. Bigger wings won't work.

Agree on battery. Make a 2.5m one with 40000 EC.

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4 minutes ago, TheFlyingKerman said:

The FAT-455 are known to shear off during high G turns because it is subject to stronger aero force but its attachment is no stronger. Bigger wings won't work.

Agree on battery. Make a 2.5m one with 40000 EC.

For your first point, can't the attachment be made stronger? Also you could simply restrict your very large planes to low G maneuvers. Furthermore, you can distribute the weight away from the center, to reduce loading on the center attachment, like the Helios and similar solar planes:

Spoiler

Helios_in_flight.jpg

If you have nearly all your weight at the center, then when you pull G's that puts a lot of strain on the center joint. If you have substantial weight attached to the wing and the tips, then the aeroforces will be distributed over multiple attachment points. I would view it as a design challenge.

For the battery, there is a 2.5m one (with 4,000 EC, not 40,000). A 3.75m one would be great... as would a 2.5m diameter one, but one that is longer (like the FL-T100 vs FL-T400 tanks... same diameters, different lenghts).

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7 hours ago, TheFlyingKerman said:

The FAT-455 are known to shear off during high G turns because it is subject to stronger aero force but its attachment is no stronger. Bigger wings won't work.

You can strut them to reduce this tendency (strut from below to prevent their shearing off when nosing up in a turn, from above to prevent them coming off when nosing down).  You can also add more wings- the more wing area your design has, the less aero forces each  wing part experiences!

The FAT-455 is big, but it's annoyingly not a shape that can be used to build large wings like the "structural" wing parts allow.  There need to be larger structural wing parts.

*OR*, an unpopular opinion with some players here, I know, but it would actually make life simpler to just give us procedural wings in Stock: and then deprecate the other wing parts.  There's a much better argument for it than fuel tanks, as wings often need to be fine-tuned in size/shape to get the plane design you want...

Eventually, everyone would get used to it- and enjoy the better CPU performance, bigger plane designs, and less cluttered part catalog it would allow.

Edited by Northstar1989
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I know everybody hates this answer, but "There's a mod for that!" .... or at least some of your issues.   I'm not sure if it's still current though....   There are welding mods that, for the wings in particular, allow you to create single pieces from multiples.  That way you could create huge wing surfaces, but only deal with one part.   The rest of your suggestions though, the welding mod wouldn't help much at all, if it didn't break the parts completely. 

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with wings I think there should be parts that essentially resemble "B9's procedural lifting surfaces", but with limitations as to not arouse the anger of the "no procedural parts brigade".

basically a selection of wings that are designed for different uses. from a "cheap" frame-and-fabric wings that work best when kept at low speed and small-to medium sized (something you might want to make a high-winged STOL bushplane use) or thin, f104-style razor-wings, that are best kept relatively short and which (if expanded to such a size where they'll flop around) will either "snap in half" or "require so much weight in internal re-enforcement-spars they might offset the advantages of being thin".

and wet-wings and the stuff in between all of these examples as well.

the main thing would be that there wouldn't be a "best wing", not even after(theoretically) all tiers were unlocked, rather each wing would have a specific "advantage" and "sweet-spots" when it comes to scale/shape vs mass/cost/lift-at-[specific-speed-altitude-envelope].. 

far from being "overly restrictive" such a system I'm proposing would basically create more meaningful variety. rather than just 15 different shaped "generic lifting surfaces".

 

 

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On 6/2/2020 at 11:25 PM, Gargamel said:

I know everybody hates this answer, but "There's a mod for that!" .... or at least some of your issues.

I've accepted @Northstar1989 's request in the Addon Discussion board for (a mod for) larger jet engines. Sometime soon(tm) I'll produce a 1.875m form of the Whiplash and a 2.5m jet engine based on Reaction Engines co's SCIMITAR, a child concept to its SABRE, and in addition, a SABRE in 2.5m and 3.75m. Knowing that though, they still came to this thread to contribute to the discussion of a very real problem for those who just don't like part mods, and those who can't use mods if they wanted to (the console crowd).

I've observed @KerikBalm for a long time and I'm a fan of their spaceplane machinations on their own planet mod and in 3.2x Kerbin. I've never seen them use a part mod so I know better than to say "there's a mod for that" ...but...

I'll take this opportunity to tease. :P

On 5/31/2020 at 11:12 AM, KerikBalm said:

#2) Larger wings and control surfaces... no, the Big-2 and FAT-455 are not big enough for me :p

Spoiler

I made these (just the wings). Kerbodyne for scale. ;p

NyZOjJi.png

"There's a mod for it" is the most appropriate answer. :) It's what KSP was made for.

Someone here raised the issue of the weakness of surface attach joints. I've confirmed it. Unfortunately I don't think anything can be done about that outside of MOAR STRUTZ or Squad making the necessary internal changes. (Remember that joint strengths were weakened because reasons! When Squad introduced Autostrut.) The config for the surface attach point doesn't accept a parameter for node size, meanwhile, the stack node size does affect its joint strength.

21 hours ago, betaking said:

far from being "overly restrictive" such a system I'm proposing would basically create more meaningful variety.

That's a pretty nice system design. I can see a variety of heat limits and dynamic pressure limits happening here, and a hard dependency on FAR.

Semi-related/Kinda off-topic: I love that you can kitbash/DIY ducted fans with Breaking Ground's fan engine parts but there are a few very disappointing details about them. I'd really like it if the engine module was extended so that it could produce lift force as it does thrust, then, for example, the propfan or unducted fan engines in mods like Airplane Plus or Near Future Aeronautics could serve their intended purposes a bit more convincingly.

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29 minutes ago, JadeOfMaar said:

The config for the surface attach point doesn't accept a parameter for node size

@JadeOfMaar Maybe I'm imagining things but I thought Squad had added an optional node size to the surface attach node some time ago.

Info here under Node Definitions (node_attach) indicates that it was a thing at some point (not sure how up to date that info is).

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@wasml Recent knowledge suggests that giving a higher stack node size to node_attach makes it weaker not stronger. I haven't tested it deeply. If you have the motivation to test this deeply and further confirm, it would be greatly appreciated. I don't have a sharp eye for joint strength (but I do for drag cubes).

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4 hours ago, JadeOfMaar said:

I've accepted @Northstar1989 's request in the Addon Discussion board for (a mod for) larger jet engines. Sometime soon(tm) I'll produce a 1.875m form of the Whiplash and a 2.5m jet engine based on Reaction Engines co's SCIMITAR, a child concept to its SABRE, and in addition, a SABRE in 2.5m and 3.75m. Knowing that though, they still came to this thread to contribute to the discussion of a very real problem for those who just don't like part mods, and those who can't use mods if they wanted to (the console crowd).

Awesome!  I hope this goes well, and isn't too much work for you!

While we're on the topic of larger parts, I also really, really would like to see larger Lifting Body fuselages in Stock (when you don't have FAR, you get Body Lift by giving fuselage parts a Wing module to generate Lift- much like the Mk2 fuselage parts have already...)

Because as cool as the Mk2 fuselage is, it just doesn't meet the Demand for launching larger/bulkier payloads: and the Mk3 fuselage is Shuttle-like, NOT a Lifting Body, and is optimized for vertical rather than lifting ascents...

Meanwhile, not many of the mods for this are satisfactory- I've found Nertea's Mk4 parts to be entirely too heavy, expensive, and unwieldy for what they do, with the Mk4 RCS pods having particularly unjustifiable part-costs, often each RCS port part cost measuring in the THOUSANDS (Nertea is one of those modders that likes to sucker-punch his Career players with excessive part dry-masses and part-costs on his fuselages and engines while you aren't looking...) 

@JadeOfMaaryour OPT fuselages are fascinating, even if many of them are too heavy for their form/function (I suggest looking to the "Stail"parts for better part cost and mass-balancing: although I'll try and get some of my own suggestions to you eventually...)

But problems like the still-unresolved 1 km spawn bug with, some of the Type J fuselages I think you said (which are also the more "modern" versions of the Stail- which I mostly use instead due to their more reasonable part-masses and costs: the latter of which are relevant as I sometimes use them on orbital stages or reusable boosters for their handy side-mounted 1.25 meter nodes, great for attaching smaller engines or docking ports for crew capsules to a 2.5 meter vacuum stack, and cross-sections midway between the 2.5 meter and 3.75 meter diameters...) illustrates *precisely* why we need larger Stock fuselages- ideally SQUAD would just pay you to work with them in making versions of your existing larger Lifting Bodies stock- rather than just mods.

Mods tend to be wracked by bugs: and modders often feel (in my opinion, a bit unjustifiably: projects are meant to be revised and carried forward) a bit guilty at revising earlier modders' work, even just to fix those bugs (like bugs with the recoil system in my Mass Driver mod, or in OPT's 1 km spawn bug), or even at just forking and updating/maintaining antiquated mods without permission (even when the license they are under *specifically* allows redistribution without permission: as it did for my Mass Driver mod- although many modders do opt for *certain* more restrictive licenses I won't name by default, just because they are popular, and they don't bother to investigate alternatives...) and the modders have been absent from the forums for months or years... (as I mostly had before finally returning and asking somebody to take over my mod- which was itself a fork and rebalance of some parts with permission from the even more outdated Stanford Torus Mod...)

Edited by Northstar1989
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1 hour ago, Bej Kerman said:

It's also the most annoying answer. Obviously there's a mod for it, but the minimalists would enjoy a stock version.

I totally agree with that. I've been around long enough to know. :) I stated matter-of-factly but I prior made clear that I know that is something that definitely could do well to be answered by stock.

2 hours ago, Northstar1989 said:

Awesome!  I hope this goes well, and isn't too much work for you!

It's not too much work, but I'm burned out from working on OPT. :D

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On 6/2/2020 at 5:36 PM, Northstar1989 said:

 used to build large wings like the an unpopular opinion with some players here, I know, but it would actually make life simpler to just give us procedural wings in Stock: and then deprecate the other wing parts.  There's a much better argument for it than fuel tanks, as wings often need to be fine-tuned in size/shape to get the plane design you want...

Eventually, everyone would get used to it- and enjoy the better CPU performance, bigger plane designs, and less cluttered part catalog it would allow.

I support procedural wings

On 6/5/2020 at 6:50 PM, betaking said:

with wings I think there should be parts that essentially resemble "B9's procedural lifting surfaces", but with limitations as to not arouse the anger of the "no procedural parts brigade"

I don't have problems with some amount of procedural parts. We already have part variants like the structural tube which has variable mass and size. Payload fairings didn't wreck the game either.

21 hours ago, JadeOfMaar said:

I've observed @KerikBalm for a long time and I'm a fan of their spaceplane machinations on their own planet mod and in 3.2x Kerbin. I've never seen them use a part mod so I know better than to say "there's a mod for that"

Thanks, strictly speaking, I play 3x, not 3.2... but I avoid mod parts to maintain a point of reference with what I see in other designs, and to avoid a problem that I think mods can cause.

I set myself a challenge, and try to solve it with the tools available. So I will mod the kerbol system to change the challenge, but I don't want to veat the challenge by just downloading a potentially imbalanced mod part.

17 hours ago, Northstar1989 said:

Meanwhile, not many of the mods for this are satisfactory- I've found Nertea's Mk4 parts to be entirely too heavy, expensive, and unwieldy for what they do ... (Nertea is one of those modders that likes to sucker-punch his Career players with excessive part dry-masses and part-costs on his fuselages and engines while you aren't looking...) 

@JadeOfMaaryour OPT fuselages are fascinating, even if many of them are too heavy for their form/function

These sort of balance questions are why I would want new parts from squad, as a standard of what is or isn't too heavy.

I can always manually rescale wings, and change values to whatever I want, but then I risk beating the challenges by just modding the parts to be better...

So, I would like to stay stock for the craft, and mod the planets and such.

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Honestly; why the **** are we using batteries for anything that's not a little probe anyway? KSP should go N U C L E A R, and hell i'd even take it in a DLC.

But aside from that tangent i'd also completely support increasing the number of 3.75M, 5M and aero parts available with both procedural and lego-style parts.

(And before anyone mentions; i know there's a fantastic mod for reactors as i currently use it...i really need to buy that dude a cup of coffee/donate some day because it's essentially become stock for me and i feel like a freeloader D:)

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On 6/10/2020 at 9:02 AM, Incarnation of Chaos said:

Honestly; why the **** are we using batteries for anything that's not a little probe anyway? KSP should go N U C L E A R, and hell i'd even take it in a DLC.

Well, the batteries are more like ultracapacitors. They can discharge all their stored energy in a fraction of a second... as fast as you can draw from it. A nuclear reactor would be an alternative to solar panels, RTGs, fuel cells, etc, but not the batteries (more like ultracapacitors in KSP).

Besides, what does the smallest nuclear reactor weigh? does that compete with 1 ton of batteries (more like ultracapacitors in KSP)? 26x of the larger batteries mass only 5.2 tons. Would you propose having a nuclear reactor that masses only 5.2 tons, and can supply >250 EC/second?

I would very much like the larger alternative to RTGs to be a nuclear reactor (and it could use the heat mechanic like the ISRU convertor, and thus need radiators)

Edited by KerikBalm
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11 hours ago, KerikBalm said:

Besides, what does the smallest nuclear reactor weigh? does that compete with 1 ton of batteries (more like ultracapacitors in KSP)? 26x of the larger batteries mass only 5.2 tons. Would you propose having a nuclear reactor that masses only 5.2 tons, and can supply >250 EC/second?

I would very much like the larger alternative to RTGs to be a nuclear reactor (and it could use the heat mechanic like the ISRU convertor, and thus need radiators)

The smallest nuclear "reactor" and generator (one that uses Stirling Pistons) is about 600 kg- NearFuture actually hits the nose right on the head with this one (although, at KSP scale, maybe it should only be 300-odd kg instead).

Yeah, no.  Anything that uses 1000 kg of batteries is horribly unrealistic- at that point any space agency would just build a nuclear reactor (the Russians actually launched a few small space-capable nuclear reactors to Low Earth Orbit many decades ago...) or add more solar panels (depending on how far the probe was going from the sun...)

Nuclear reactors in space have been done before.  One of them (Kosmos 954) even crashed in northern Canada and caused a minor diplomatic incident:

https://en.m.wikipedia.org/wiki/Kosmos_954

Edited by Northstar1989
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6 hours ago, Northstar1989 said:

The smallest nuclear "reactor" and generator (one that uses Stirling Pistons) is about 600 kg- NearFuture actually hits the nose right on the head with this one (although, at KSP scale, maybe it should only be 300-odd kg instead).

Yeah, no.  Anything that uses 1000 kg of batteries is horribly unrealistic- at that point any space agency would just build a nuclear reactor (the Russians actually launched a few small space-capable nuclear reactors to Low Earth Orbit many decades ago...) or add more solar panels (depending on how far the probe was going from the sun...)

For reference, a tesla model S reportedly has a 540 kg battery, already over half a ton. It supplies a 615 kW motor.

What is the power output of such a small reactor? The SNAP reactor is even smaller: 

https://en.wikipedia.org/wiki/SNAP-10A  "The SNAP-10A reactor was designed for a thermal power output of 30 kW and unshielded weighs 650 lb (290 kg)" - Note, that's Thermal power, not electrical power, which would be much less. It was reported to be designed to produce 500 watts for 1 year, and reached a peak of 590 wats before shutdown. Assuming a linear scaleup, a 1 ton design would get you a 2.34 kW output. Scaling up the Tesla battery to 1 ton gets you 1.14 MW. Nearly 500x higher power output.

The point of 1000 kg of ultracapacitors would not be to provide for long term energy duration, but to meet short term power demand. If you need a high electrical power output, for a short duration, then batteries recharged by a small reactor are better than a big reactor that can supply the power continuously.

Capacitors are even better... KSP batteries function more like capacitors anyway.

Current capacitors have a much lower specific energy (Wh/kg) than Li-Ion batteries, but future ultracapacitors may be able to exceed them.

Any electrical pulsed drive (particularly, pulsed fusion drives, such as a dense plasma focus design) would use capacitors to supply the power for the pulses, not a secondary fission reactor.

If we were to make an aircraft to explore mars, its would be lighter if it used batteries/ultracapacitors to supply the power during flight, with solar/RTG/nuclear to recharge between flights...

Which is incidentally what I'm doing with some craft in KSP, and why I'm asking for bigger batteries.

Quote

Nuclear reactors in space have been done before.  One of them (Kosmos 954) even crashed in northern Canada and caused a minor diplomatic incident:

https://en.m.wikipedia.org/wiki/Kosmos_954

Yea, I know... sort of irrelevant though, no? Nobody was disputing that.

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23 hours ago, KerikBalm said:

Well, the batteries are more like ultracapacitors. They can discharge all their stored energy in a fraction of a second... as fast as you can draw from it. A nuclear reactor would be an alternative to solar panels, RTGs, fuel cells, etc, but not the batteries (more like ultracapacitors in KSP).

Besides, what does the smallest nuclear reactor weigh? does that compete with 1 ton of batteries (more like ultracapacitors in KSP)? 26x of the larger batteries mass only 5.2 tons. Would you propose having a nuclear reactor that masses only 5.2 tons, and can supply >250 EC/second?

I would very much like the larger alternative to RTGs to be a nuclear reactor (and it could use the heat mechanic like the ISRU convertor, and thus need radiators)

Now i'm not sure how much Nert bent for "Gameplay Reasons" with it, but the smallest reactor in NFE is half a ton and supplies 40 EC per second and costs around 13,000 fueled. Now it also needs radiators to dissipate heat, and with those it creeps up to 0.6 tons. But just with those numbers you could use 8 of those reactors at the same mass (5 tons) and generate >300 EC per second.

However what you're asking seems more like an analogue of the "Garnet" reactor; which is between the 1MW and the Sterling reactor. It masses at 2 tons, costs 100,000 fueled and generates 400 EC/sec. It also needs 800kw of cooling and thus another 0.2 tons of radiator are needed to cool it.

Basically if his reactors are even close to realistic, there's no real reason to use massive stacks of batteries instead of nuclear reactors. Even accounting with the mass of radiators and decay, they're superior in every way. And you can still mount batteries to allow running essential equipment when powered down, and the fuel isn't exhausted until the reactor is actually active (Which is fairly realistic; U-235 takes 150,000 years before it's first halflife). So you can have multiple reactors to extend a mission.

That all being said; i have no impressions of batteries/capacitors going away. But with actual reactors they'd end up serving their actual role as energy storage, instead of being used as a buffer for magical infinite EC tubez slow recharge times between ion burns and taking up massive amounts of dry mass (Which actually is reasonably realistic; batteries have terrible energy density.)

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22 hours ago, KerikBalm said:

For reference, a tesla model S reportedly has a 540 kg battery, already over half a ton. It supplies a 615 kW motor.

What is the power output of such a small reactor? The SNAP reactor is even smaller: 

https://en.wikipedia.org/wiki/SNAP-10A  "The SNAP-10A reactor was designed for a thermal power output of 30 kW and unshielded weighs 650 lb (290 kg)" - Note, that's Thermal power, not electrical power, which would be much less. It was reported to be designed to produce 500 watts for 1 year, and reached a peak of 590 wats before shutdown. Assuming a linear scaleup, a 1 ton design would get you a 2.34 kW output. Scaling up the Tesla battery to 1 ton gets you 1.14 MW. Nearly 500x higher power output.

First of all, 30 kW of thermal power gets you 5-9 kW of electricity at a reasonable (16-30%) conversion efficiency.  This requires extra mass though (Stirling Pistons are much less efficient: hence why that design was only 1-2% efficient).

Nuclear reactors DON'T scale linearly- their power output scales exponentially (the power per kg of fuel squares, if I recall) with the fuel mass- which also increases as a percentage of the reactor mass the bigger you go.  So a 1 ton reactor might produce 400 kW of thermal power instead of the 103 kW you'd get for a linear scale-up.  And since you'd be able to fit in a proper generator at that scale, within your mass budget (the 290 kg included the Stirling Pistons in its mass budget as well), you'd get 80-120 kW of electrical power from it: 160-240x that of the tiny reactor with Stirling Pistons!

22 hours ago, KerikBalm said:

The point of 1000 kg of ultracapacitors would not be to provide for long term energy duration, but to meet short term power demand. If you need a high electrical power output, for a short duration, then batteries recharged by a small reactor are better than a big reactor that can supply the power continuously.

Capacitors are even better... KSP batteries function more like capacitors anyway.

Current capacitors have a much lower specific energy (Wh/kg) than Li-Ion batteries, but future ultracapacitors may be able to exceed them.

Any electrical pulsed drive (particularly, pulsed fusion drives, such as a dense plasma focus design) would use capacitors to supply the power for the pulses, not a secondary fission reactor.

If we were to make an aircraft to explore mars, its would be lighter if it used batteries/ultracapacitors to supply the power during flight, with solar/RTG/nuclear to recharge between flights...

Which is incidentally what I'm doing with some craft in KSP, and why I'm asking for bigger batteries.

Pulsed Fusion is a niche purpose: and nobody disputes that would rely on capacitors.

But most uses of power: such as an ion thruster, require constant power output.  You can supply more power for a long burn with nuclear power than you can with batteries/capacitors plus solar.

RTG's *are* a nuclear power source: just an incredibly inefficient one.  They supply a lot less power per kg per second than proper reactors.

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17 hours ago, Incarnation of Chaos said:

Basically if his reactors are even close to realistic,

They are, if you assume 1 EC=1kW.  However 1 EC does far, far more than 1 kW could ever do in reality in an ion thruster- and far less than it would do in terms of powering probe cores.  For the game scale/balance they're right on the nose, though.

KSP-Interstellar has next-gen reactors which are amazingly more efficient for space use, though, and are ALSO true to real-life science.  The difference is, the past tried/true tech represented in NearFuture is outdated and EXTREMELY marginal for space use (ironic given the name "NearFUTURE"- it's all nearPAST), whereas Interstellar has the kind of next-gen (ACTUAL future) tech that will probably take humans to Jupiter and such... (Mars is entirely doable with conventional rocketry: aka SpaceX)

17 hours ago, Incarnation of Chaos said:

and the fuel isn't exhausted until the reactor is actually active (Which is fairly realistic; U-235 takes 150,000 years before it's first halflife). So you can have multiple reactors to extend a mission.

You can prolong the reactor life a lot more if you turn down the power levels.  At lower power levels they produce less EC, but consume fuel more slowly.  You can also reprocess fuel (turning a % of it back into usable fuel), and can swap in fresh (possibly reprocessed) fuel with an engineer while the reactor is powered down...  You get longer mission life for a launch mass with a single reactor and regular fuel swaps than you can with multiple reactors...

17 hours ago, Incarnation of Chaos said:

That all being said; i have no impressions of batteries/capacitors going away. But with actual reactors they'd end up serving their actual role as energy storage, instead of being used as a buffer for magical infinite EC tubez slow recharge times between ion burns and taking up massive amounts of dry mass (Which actually is reasonably realistic; batteries have terrible energy density.)

The way most players use batteries doesn't make much sense: they'd often be better off just loading on more (LARGER!  This is a thread about larger parts after all: and we need larger panels than the Gigantor!) solar panels and setting the throttle to whatever the panels can sustain, while they go off and do something else for a bit (or use a mod allowing thrust while in higher time-warps).

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7 hours ago, Northstar1989 said:

First of all, 30 kW of thermal power gets you 5-9 kW of electricity at a reasonable (16-30%) conversion efficiency.  This requires extra mass though (Stirling Pistons are much less efficient: hence why that design was only 1-2% efficient).

And when we're talking relatively low masses and the need to radiate into vacuum, that mass becomes considerable. I'm not sure at what point it becomes preferable to a thermocouple like on a standard RTG (after all, there is a reason RTGs use thermocouples)

Quote

Nuclear reactors DON'T scale linearly- their power output scales exponentially (the power per kg of fuel squares, if I recall) with the fuel mass- which also increases as a percentage of the reactor mass the bigger you go. 

I don't think this is right, and would be oversimplified at any rate. The neutron flux goes up, but at a certain point, the reactor power will be the same per unit mass, as the fuel rods heat to their maximum temperature (any hotter and they melt), and their maximum output is limited by cooling. Now a reactor has to reach a sufficient neutron flux for a chain reaction, but this required flux goes down as enrichment goes up. A tiny reactor of normally enriched uranium won't be able to sustain a chain reaction. Highly enriched uranium can do it. Basically, as you scale the reactor down, the enrichment needs to go up. IIRC, the reactors used in space used very highly enriched uranium.

Quote

Pulsed Fusion is a niche purpose: and nobody disputes that would rely on capacitors.

But most uses of power: such as an ion thruster, require constant power output.  You can supply more power for a long burn with nuclear power than you can with batteries/capacitors plus solar.

For sure, but I'm not talking about long duration power demands. I'm talking about limited duration atmospheric flights on other worlds.

Quote

RTG's *are* a nuclear power source: just an incredibly inefficient one.  They supply a lot less power per kg per second than proper reactors.

Yea, I know, I should have said nuclear *reactors*. RTGs use spontaneous nuclear reactions/decay, but they aren't a reactor that causes additional nuclear reactions.

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