Northstar1989

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  1. Don't just automatically assume you know better than another player more experienced than you and post a Craft File: that's just rude. Yours is a grossly suboptimal design: if you're going to use a Mk3 fuselage, it should only be for much larger payloads than that (or MULTIPLE payloads in that weight range). If I were going to lift a payload of that size to orbit, I'd use a long Mk2 fuselage, with 1.875 meter fuel tanks on the payload. This will get you to orbit for much less fuel, as the Mk2 is a Lifting Body and more aerodynamically efficient (in FAR and especially in Stock- which lacks the FAR code that creates Body Lift from ALL fuselages to some degree) than the Mk3 for payloads in that size range. To use a Mk3 (which is really meant for use as a Shuttle fuselage, and is terribly-shaped for horozontal takeoff spaceplanes- meaning I'd probably use a Stail fuselage from OPT instead of not playing Stock-only...) I'd have to be lifting a payload MUCH bigger than that- at which point I would need the extra engines I just talked about.
  2. Comfortable? For optimum efficiency a spaceplane with a Mk3 fuselage requires at least 8-10 jet engines. Any less than that and you're wasting fuel on an excessively-slow ascent and run for speed at altitude. With 1.875 meter supersonic jets, we could do this with just 4 jet engines (each 1.875 meter jet could have 2.25 times the Thrust of a 1.25 meter jet, to get the same Thrust per unit of cross-sectional area: so 4 of these would be equivalent to NINE 1.25 meter jets). This would also generate less Drag- for the same reason four 1.875 meter stacks generate less Drag than nine 1.25 meter stacks: less wetted surface area due to the Square-Cube Law...
  3. A lot more than a comparable rocket (TWR is at least, 1:20 to maybe 1:24, with the mixing chamber ramjets also active). But Effective ISP is much, much higher (in the range of a jet engine just for the ducted rocket performance, 3500-4200 sec Effective ISP, depending on mixing-ratios of LH2:air). This is basically a type of Hybrid airbreathing/rocket engine, much like the SABRE, except that the TWR is actually much better than many jet engines (which typically range from TWR of about 1:6 to 1:12), and the airbreathing Effective ISP a bit lower than some high-end jet engines. The Thrust per unit of cross-sectional area (important for spaceplane design) is also much higher than any jet... The main advantage though (because none of that would nearly justify use of a nuclear reactor inside the atmosphere, from a PR/safety perspective) is that this doubles as a Nuclear Thermal Rocket when you reach the point where airbreathing propulsion is no longer viable (however with an internal Scramjet, rather than Ramjet, this wouldn't be until at least Mach 7-12). So the NTR is actively producing a *HUGE* amount of Thrust (but TWR is still poor as it weighs so much) in the atmosphere when in airbreathing mode (at very low Exhaust Velocity: but since almost all the Working Mass is from the atmosphere, at high Effective ISP), rather than being deadweight all the way until rocket closed-cycle Thrust is desirable... This unfortunately doesn't scale down well- nuclear reactors become less and less efficient in terms of power output per kg of mass the smaller they become, but DOES scale *UP* extremely well. It would also require a rather large, to potentially HUGE airframe (with lots of wing-area, at very low Aspect Ratio due to the vast majority of the time spent in atmospheric being supersonic/hypersonic) if put on a spaceplane (which is where this really shines) both due to the lack of scalability of the engine (you have to build a really huge airframe around a really huge engine) and the need to reduce re-entry and ascent heating (you can fly higher for a given speed with larger wings, helping with heat issues) to reasonable levels... If the payload capacity this design/airframe led to ended up being overkill, I would suggest NOT going the way of the Shuttle- and trying to find huge payloads to justify a huge spaceplane with more payload capacity than you actually need- nor of trying to shrink the whole thing down too far (which will kill the payload-fraction to little benefit, as reactors lose performance very quickly as you shrink them down), but instead suggest increasing the mass budget of the least reliable/reusable or most expensive parts of the design, so heavier/cheaper/more reliable parts with wider safety-margins (and built to higher tolerances of manufacturing error) and built of easier-to-machine materials (high-end Steel instead of Aluminum, for instance: which is far heavier, but more heat-tolerant and much cheaper to machine) can be substituted in instead (one of the reasons the Shuttle was so expensive- a lot of the parts were designed to INCREDIBLY strict margins, leading to a lot of parts that required excessive maintenance or had to be replaced after just a few flights...) You can also add redundancies to the design, increasing mass but allowing use of less reliable (but cheaper) parts that are more likely to fail, to trade-off any excess payload-capacity for lower cost and higher overall vehicle reliability...
  4. Adding mass to the trip is kind of the point. It adds a new aspect to mission planning- taking a longer/slower trajectory and saving fuel, vs..a faster one to save life support mass. It also synergizes well with nifty things like Greenhouses- if they added those too.
  5. Because then you need two seperate, both very heavy, engines. A nuclear ramrocket might be lucky to clear a TWR of 15:1 or maybe 20:1 (with enough bypass, Thrust from the scram/ramjets, more modern materials than NERVA, and a more powerful reactor than NERVA) in atmospheric mode- but at least you don't need a seperate system for vacuum thrust. A chemical ducted rocket gets maybe 30:1 TWR, but then you need an entire NTR for outside the atmosphere that weighs at least as much as the ducted rocket- and probably about 5-6x as much (NTR's only get a TWR of maybe 2:1 at best, NERVA only managed 1.38). And your launch stage ends up being much heavier due to only having about 1/4th (or less) the Effective ISP in atmosphere (700-800 sec vs. 3400+ sec). Space Programs are expensive. And haven't achieved but a fraction of what they're capable of. With all the scientific benefits you'd reap (or money you'd save vs. the even more massive budgets necessary to achieve the same things with more conventional rocketry) you could save THOUSANDS of lives here on Earth... For an example of just how many lives a little science can save, consider how many people have died worldwide of Covid-19 (numbering in the hundreds of thousands, and still growing). Now imagine just how many lives could have been saved if we magically had a vaccine back in early March. Ditto for a million other scientific breakthroughs. You save far more lives pushing a space program forward at all costs (through discoveries that save lives here in Earth) than you could EVER possibly lose in nuclear rocketry accidents. The cost:benefit analysis is MUCH more favorable than, say, nuclear power for electricity on Earth (which can give us something like Chernobyl, or Fukushima, and a cost:benefit analysis says we should HALT IMMEDIATELY, because we don't really spend THAT much money on generating electricity by more expensive alternatives... Plus, we need ALL the nuclear fuel we can get for the next 3-5 centuries of space exploration...) As far as I'm concerned, based on the costs and benefits, the anti-nuclear folks can suck it.
  6. That applies to pure Nuclear Thermal Rocketry. But this isn't a pure nuclear thermal rocket we are talking. You take the power output of the reactor, and then you divide that among a MUCH larger Working Mass in a nuclear ramrocket- similar to how using heavier propellants gives you higher Thrust from a nuke. But there is no Effective ISP cost to doing this here, as the extra Working Mass cones from the air intakes- so you actually INCREASE the Effective ISP while doing this. The problem I was referring to is that a current-generation nuclear reactor weighs a lot, while not producing that much more (and often, less) Thermal Power than a chemical rocket's Combustion Chamber. So TWR suffers. But in terms of raw Thrust: when most of your Working Mass comes from the atmosphere, and the internal propellant merely acts as a means of transfer of heat to this air (similar to how a heat exchanger directly warms the air in a Nuclear Thermal Turbojet- except the bit of internal Hydrogen you add does give a little extra Thrust and Exhaust Velocity by slightly increasing the Working Mass *AND* provides the basis for a ramjet to operate in the Mixing Chamber at higher atmospheric speeds) the main determinant of Thrust is simply how much Thermal Power you can produce. If you can produce more than an equivalent chemical rocket, your Thrust will actually be HIGHER when most of your Working Mass is atmospheric air... The final iterations of NERVA (the -XE models) produced about 1140 MW of Thermal Power. That was enough to produce 246.6 kN of Thrust at 841 seconds (8250 m/s Exhaust Velocity). However if you split that same Thermal Power over enough Working Mass from air to bring Exhaust Velocity down to 2000 m/s (a little over 200 sec ISP, but due to use of atmospheric air, over 3400 sec *Effective ISP*) by dividing it over a bit more than 17x the Working Mass (given the relative densities of H2 and atmospheric air, this only requires a 1.10:1 ratio of atmospheric air volume to H2 volume: whereas ratios of up to 2:1 are easily achievable...) you get 4.125x the Thrust: or 1017.225 kN of Thrust. That's more than the Thrust of a single Merlin engine (9 of which are used to lift a Falcon 9, at 854 kN of sea level Thrust each). And if you used a 2:1 bypass ratio (easily feasible) you could get a little over 1.348 times the Thrust (sqrt of 1.818, which is 2/1.1) instead: or 1371.626 kN of Thrust. At these #'s (note the high EFFECTIVE ISP massively reduces fuel requirements), you'd only need a cluster of 3 NERVA's converted into air-augmented rockets (at a 2:1 bypass ratio) to lift a rocket with a launch stage capable of propelling the Falcon 9 upper stage 7000 m/s, if most of that 7 km/s were provided in-atmosphere where the air-augmented rockets work (not feasible in reality, I know, but a useful thought-experiment). More likely a single, larger reactor, as reactor Thermal Power scales much faster than mass when you scale an individual reactor up (meaning one large reactor is better than 3-4 small reactors). And all this is with 1960's reactor technology. More modern reactors should be able to obtain higher power density (more thermal power per kg of mass: NERVA-XE weighed 18.144 tons, nozzle and all, and included a 1140 MW reactor...) Bottom Line: giving a nuclear reactor this much more Working Mass to play with MASSIVELY increases your Thrust (about 5.56- fold for a 2:1 bypass ratio, BEFORE you include any extra Thrust from an included ramjet/scramjet in the mixing chamber...) Don't get me wrong though: chemical rockets can produce even more Thrust than this as ducted rockets for the same weight (about 4x more Thrust, in fact), at very respectable sea level ISP (up to about 700-1000 seconds Effective ISP, at a 4:1 bypass ratio). But they aren't capable of then acting as a >800 sec ISP rocket once you leave the atmosphere (negating the need for separate, vacuum-specialized engines entirely: and allowing you to make all your staging just about losing/recovering bulky LH2 fuel tanks...)
  7. Let's not forget this thread was about nuclear ramrockets? There are plenty of intelligent things to say about that: like I've been considering the TWR, and am concerned it would be abysmal without a much more powerful nuclear reactor (than what is currently possible with US reactor technology). However talking about a TBCC engine (which the US has been working on its own versions of for a decade at least) as propaganda doesn't say anything about the possibilities for nuclear ramrockets.
  8. The publication I linked was not from the Chinese state media. It was from a U.S. Air Force publication, 2 years ago. No corrections have been required to these articles since. These aren't multiple engines they are looking at designing. This is a single, multi-stage engine they are ALREADY building the factory to manufacture. The design work was apparently done years ago, in a highly secretive manner... You would know all this if you read the publication. EDIT: The engine in question (TBCC engine) has already been built and tested on test-stands, as of last year. Next step is putting it on an aircraft: https://m.economictimes.com/news/defence/china-successfully-completes-hypersonic-engine-test/articleshow/67435297.cms
  9. P.S. And if you think 3-mode engines are insane, the Chinese recently opened a factory to assemble FOUR mode engines: turbofan, ramjet, scranjet, and (ducted) rocket all in one: https://www.airuniversity.af.edu/CASI/Display/Article/1604494/chinas-opening-a-factory-to-build-engines-for-hypersonic-missiles-and-spaceplan/ What I suggested is actually simpler than this, in that it does away with the turbofan and Scramjet parts entirely (*OR* swaps the Ramjet for a Scramjet) and uses the ducted rocket to achieve ramjet speed (Mach 2) instead.. Only the heat source for the rocket is a nuclear reactor rather than combustion- and the nuclear rocket uses pure LH2 for propellant. So some supplementary (conventional) ducted rockets might still be necessary to provide extra Thrust (still lighter/simpler than adding an integral turbofan, though!) The Chinese engine is also designed to operate off LOX/RP-1 (Kerosene and Liquid Oxygen) rather than Liquid Hydrogen. And is planned for use in the FIRST stage of a horizontal takeoff launch-system: with a reusable rocket launching off its back at the edge of the atmosphere (at speeds of at least Mach 7-8, likely, based on the engine capabilities) and propelling itself with rockets alone the rest of the way to orbit...
  10. Actually not. The rocket part of a ramrocket generates Thrust even when stationary. The rocket exhaust ignites the fuel-air mixture in the mixing chamber, so you get some (stationary Thrust from the ramjet part of this mutt of a rocket and a ramjet... (even with the scram-rocket version, the rocket itself will produce Thrust up until you reach the supersonic speeds necessary for the Scramjet part to ignite. And, this can be combined: for instance the proposed RBCC cycle is an all-in-one Ducted Rocket, Ramrocket, and Scramrocket...) The KSP ramjets actually perform much like ramrockets would IRL (substantial stationary Thrust, higher Thrust at speed) except that their ISP is much too high for a ramrocket, and they don't consume Oxidizer as a ramrocket would. A similar, related concept is a turboramjet- which uses a small rocket to pull in additional air and sustain combustion in a ramjet even beyond speeds/altitudes where a ramjet would normally be capable of operation. The rocket is placed a bit differently in such a design, though, and is much smaller relative to the ramjet. The bigger problem is that it's nuclear, and hence radiation is going to be a real concern. You probably wouldn't want to activate the reactor on the ground anyways (indeed not until you were already at a fairly high altitude). This would thus be an engine for the speed-run of a spaceplane, or the second (seperable/decoupling) stage of a two-stage spaceplane. You don't need to ignite all engines on the ground in a SSTO spaceplane. Indeed many proposed designs don't (having rockets you don't use until altitude, plus maybe briefly at takeoff), or use multi--mode engines which switch operations in flight (RBCC has *THREE* modes, for instance: Ducted Rocket, Ramrocket, and Scramjet). Re-read what I wrote (with the clarification here). Any type of ramrocket design usually behaves as a Ducted Rocket at low speeds. Ducted ("air augmented") Rockets produce Thrust and ISP slightly better than a rocket at first, increasing to the 700-800 second range by about Mach 3-4 (but a ramrocket will see ignition of the ramjet in the mixing zone long before this point...) Two-Stage Spaceplanes are entirely feasible: with the upper stage spaceplane that actually achieves orbit riding piggyback on a larger spaceplane (technically only a plane, but to really get the most out of this it needs to be a much, much, much larger, faster, and more efficient plane than something like a 747) that then flies back to the runway independently. This allows the upper stage to only be equipped with engines that work well at high speeds/altitudes, such as the nuclear ramrocket I refer to here (a CONVENTIONAL ramrocket doesn't actually need the booster to get off the ground: as the rockets within the ramrocket usually produce enough Thrust acting as air-augmented rockets without complete combustion yet occurring in the mixing chamber to reach speeds where the ramjets will operate efficiently. And I repeat myself: the primary rocket produces a sufficiently hot/fast exhaust stream for the ramjet to start producing a little Thrust even on the runway...) A diagram would be helpful, and maybe I'll produce one if you still don't understand. But this is a textual illustration of how both ramrockets and some designs of ducted rocket work: Primary Rocket --> Mixing Chamber --> Nozzle - The mixing chamber is where the 'primary' rocket exhaust is mixed with air. In a ramrocket, the rocket simply operates fuel-rich, and the mixing chamber is designed to encourage/allow for combustion of the air with the fuel-rich rocket exhaust. But this ramjet combustion is not NECESSARY for the rocket to produce a fairly large Thrust through the Air-Augmentation and nozzle on its own (indeed most Thrust comes from the primary rocket EVEN WHEN the ramjet is operating...) - The primary function of the mixing-chamber is to provide extra Working Mass for the rocket. This roughly doubles the Thrust if you mix the rocket exhaust in a 3:1 ratio with air and no ramjet combustion occurs, for instance. The ramjet combustion is actually a minor optimization to the design (typically providing around 10-20% extra Thrust in a conventional ramrocket design: although Nuclear ones would benefit more sue to their anemic base-Thrust levels)- ramjets don't produce that much Thrust at reasonable sizes in real life, unlike in KSP. - The Nozzle, is s nozzle. You can use a typical bell nozzle, or opt for an Aerospike. Aerospikes should work very, very well here as ducted rocket exhaust is much cooler than in a conventional rocket (although you also have less unburnt fuel from the turbopump available for Regenerative Cooling) and the nozzle needs to be larger to accommodate the high Mass Flow Rate from all the extra Working Mass from the atmosphere (larger rockets are, paradoxically, EASIER to keep cool: due to effects resulting from the Square-Cube Law, which reduce the relative surface area exposed to hot gasses... I *highly* recommend the Everyday Astronaut article on Aerospike Nozzles for more detail on precisely why...) A HTHL spaceplane is a FULLY reusable spacecraft. Earth isn't Kerbin. You have to reach incredibly high speeds in the atmosphere (by Mach 4 or 5 your plane is already catching fire magnificently: orbital velocity on Earth is around Mach 20, I believe) to have any chance of reaching orbit with a spaceplane, due to the much larger radius of Earth. A ramrocket isn't even designed for speeds that high. We're talking a propulsion system that operates best between about Mach 2-5 (ramrockets have a much wider performance window than ramjets, as the rocket exhaust stabilizes ramjet combustion at low speeds or pressures), and operates mostly as a ducted rocket (with lower ISP) from stationary to about Mach 2 (although, as said, you still see a *little* combustion in the mixing chamber even at takeoff). Its Thrust never drops to zero- or any less than the Thrust/ISP of the primary rocket. This differs from the conventional (HydroLOX primary rocket) design in that the rocket is nuclear. Once again, this means less Thrust (but higher ISP due to lighter exhaust gasses) when operating as a ducted rocket, but much, much more Hydrogen in the mixing chamber potentially subject to combustion (meaning instead of adding 10-20% Thrust, you might add 40-50% or more with a sufficiently large mixing chamber...) Normally a ramjet would "choke" on this much Hydrogen in one place: but the nuclear reactor superheats the Hydrogen to a much higher temperature than compressive heating would normally pre-heat the intake air of a ramjet to, and as a result the ramjet should able to operate at much higher Mass Flow Rates across a much wider performance envelope... (even so, the need to dilute the Hydrogen a bit is why the mixing chamber should be designed larger than for a ducted rocket...)
  11. So, in looking at Air-Augmented ("ducted") rockets recently, and considering nuclear propulsion, this idea came to mind (I think I've read about it before- will post links for background when I have time) Basically, it combines the features of a nuclear thermal rocket (aka. 'NERVA' aa the most famous example) or a nuclear thermal turbojet, with a ramrocket (itself the hybrid of a Ramjet and an Air-Augmented Rocket). So, it looks something like this: air enters into intakes (and probably then a pre-cooler passing some heat to Liquid Hydrogen as a heat-sink: ala. "SABRE" intakes in real life) and enters a mixing chamber. Separately, Liquid Hydrogen is passed over a nuclear reactor's heat-exchanger, just like in NERVA or any similar design. The exhaust from the nuclear heat-exchanger then enters a mixing-chamber with the intake air, exactly like how any ducted rocket works (basically, ducted rockets mix the exhaust from a Combustion Chamber with intake air BEFORE ejecting it through a rocket nozzle- this is all there need be to such a design... If the air is pre-cooled first, heat management becomes easier and you can use more heat-resistant materials or a lightweight heat-vulnerable Aerospike Nozzle, without them melting, but this is not usually done...) However because there is Oxygen in the intake air, and the nuclear reactor exhaust is superheated Hydrogen, there is the possibility for Ramjet-style combustion. This is how a ramrocket normally works (the ONLY difference here is that instead of Hydrogen-rich combustion products from a conventional rocket combustion chamber entering the mixing/ secondary combustion chamber, you have 100% Hydrogen from a nuclear reactor's heat exchanger entering it instead...) This Hydrogen is afforded the opportunity to combust (this is also why you want pre-coolers: to allow compression and cooling of the intake airflow by Compressors to speeds/temperatures usable for a Ramjet even in very high speed/altitude flight), and you get additional energy from this Ramjet-style combustion, which gets you extra Thrust after you pass the exhaust through a rocket nozzle as with any ramrocket... Basically, it's a nuclear thermal turbojet, but with the addition of an integral ramjet for extra Thrust and higher Exhaust Velocity (which also means the whole thing is useful at higher speeds than a normal nuclear turbojet). The secondary combustion/mixing chamber could even be designed as a Scramjet: although that creates problems with no longer having any static thrust on the runway... (due to having low TWR, very high Effective ISP, and being optimal for high-speed atmospheric use: this is best used on a horizontal-takeoff spaceplane...) Other notables: - The airflow would be possible to close off at the point of the intake, or possibly also downstream, allowing for operation as a pure (but very heavy) nuclear thermal rocket once you leave the performance envelope for airbreathing propulsion. Thos is similar to the Rocket-Based Combined Cycle ("RBCC"- basically a ducted rocket, ramrocket, and closed-cycle rocket all in one...) propulsion system, except that the initial heat source is a nuclear reactor rather than a primary rocket combustion chamber. - This works best with lighter/more powerful next-gen nuclear reactors, like Molten Salt Reactors (not coincidentally, previous investigation into nuclear thermal turbojets looked at using MSR's for the reactor componemt...) - Nuclear Reactors with TODAY's tech actually eject COLDER exhaust than a rocket combustion chamber. The reason for their high ISP is due to using a pure exhaust of nothing but Hydrogen... This means that, if you further diluted this already-lower heat with colder-still atmospheric air, you would have exhaust temperatures very usable for an Aerospike Nozzle: these nozzles normally having tendency to melt without a lot of extra weight for heat-managenent.
  12. A while ago there was this excellent discussion on air intakes and drag in KSP: This is still an important topic (would be even more so if the dev's could give us some larger airbreathing/jet engines, so spaceplanes are actually useful without massive engine-spam!) and I wanted to continue to draw attention to the idea, discuss it, and see if anything has changed. Also, there were some nuances to Right's graph (re-posted below for convenience) that I don't think really got any proper discussion- and couldn't be discussed there now without nero'ing a very old thread... Note, for instance, the shape of the Shock Cone Intake performance curve (or lack thereof). I think many players sub-optimally assumed the most efficient Spaceplane ascents involve keeping all your engines lit throughout your entire ascent. However I have increasingly found this is NOT the case-especially with the 2 stage spaceplane designs I have been experimenting with lately (a smaller Spaceplane optimized for high-altitude, high-speed operation rides piggyback atop a larger plane that breaks off. Awesome in Sandbox/Science, but requires a mod like Flight Manager for Reusable Stages so you can fly the lower stage back to actually be useful in Career...) Often it is better to have some engines- particularly Ramjet engines- you only ignite at higher altitudes and speeds, keeping your demand for IntakeAir (and Thrust production) relatively flat as you ascend... (this is even MORE true with modded parts like the Air-Augmented rockets from, I think, Mk2 Expansion: which, realistically for a ducted rocket, perform better at high speeds not only in terms of Thrust, but ISP...) If you have engines you only ignite at high altitude+speed (or simply don't throttle all the way up until you reach high speed/altitude due to heating issues, aerodynamic stability- particularly with dynamically unstable designs that become less stable at higher speeds, or not having your wings rip off due to aero forces in FAR!) then the Shock Intake curve suddenly looks a lot more appealing: note these curves are for constant altitude- the Shock curve ends up being flattened (in terms of rate of IntakeAir production) by reduced air density at higher altitude... Other things notable: - The Divertless Radial Supersonic Intakes appear to have the smallest performance-drop of any intake other than the Shock Intakes between Mach 3 and higher speeds (the slope of their curve is much more gradual, even controlling for their lower peak), making them often the second-best choice for high-speed planes (as well as great for fine-tuning *precisely* how much intake you have, so you don't have any more than needed...) - Engine Pre-coolers have, surprisingly (and unrealistically, given the whole POINT of using them in real life would be high speed+altitude performance) a steeper curve relative to the amplitude of their peak than the Adjustable Ramp Intake (aka the stock RAM-effect intakes). This makes them more poorly suited for high speed/altitude operations, at least as intakes (again, this is unrealistic- and the dev's ought to rebalance these to make them more useful). That being said, form-drag (from frontal cross-section mainly) becomes much more punishing at higher speeds, at least in FAR, so they actually do work well at high speed planes- but for all the wrong reasons (in real life, Pre-Coolers aren't even intakes at all, but allow you to cool/compress airflow before it reaches the engines so they "think" they're actually operating at lower speeds/altitudes. This would be easily simulated in KSP by simply having them decrease the airflow speed and altitude any engines they are connected too "see"- and indeed this is EXACTLY how they used to or still do work in KSP-Interstellar, which included special code to make pre-coolers work realistically: at least in older versions for sure...) In real life, they would produce a lot of intake Drag (as you slow the airflow more) and provide no direct intake functionality- yet be CRITICAL for a horizontal-takeoff spaceplane ascent... - On the topic of pre-coolers, again: there has been some mention that they are highly heat-conductive (wicking heat away from engines), yet this is somehow a BAD thing (as it causes them to absorb more heat from the atmosphere). It seems to me most players don't understand the Stock heat conduction system well, or how to use this properly. The best parts to attach pre-coolers to (on the other side of the engine) are large, heavy parts with a lot of cross-sectional area (so these parts in turn can pass the heat they absorb from the pre-coolers to other parts). This is entirely because the Stock heat model assumes an entire part is all at a constant temperature, to make the calculations manageable. Anyways, this makes good parts to attach Pre-Coolers to things like the long Mk2-Mk1 adapter, the Mk2 Bicoupler, the flat (rear) end of Mk3 parts, or especially large cross-section mod parts with inline 1.25 meter nodes (like the "Stail" to 2.5 meter adapter with shoulders in OPT Aerospace, or the Mk4 Adapters in Mk4 Expansion...) The parts they are attached to should, ideally, in turn be attached to even larger parts (like a Mk2-3 adapter in front of a Mk2 Bicoupler). The key is to wick heat away from the pre-coolers as quickly as possible so they can wick more heat away from the engines in turn. Not that engine overheating is THAT big of a problem in Stock (except for with the NERVA nuclear rockets- a part intake air precoolers would be USELESS for in real life, unless you were air-augmenting them... Or modded nuclear turbojets, like those in Mk2 Expansion- where at least the use of pre-coolers is realistic) - The Small Circular Intake has a relatively flat curve that LOOKS like it would be well-suited to high-speed operations: but in reality they tend to explode at high speeds, as they have terrible heat-tolerances...
  13. 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) 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... 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).
  14. 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! 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.
  15. 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