Worried about KSP magic tech, unrealistic orbital mechanics, and lol-explosions

[Klapaucius]

3 hours ago, Snark said:

No word yet, of course, on how KSP 2 will handle underwater stuff.  I'm a little bit torn about it, myself.  On the one hand, I'd love to have some water-exploration parts to play with... on the other hand, to me it's Kerbal Space Program, not Kerbal Submarine Program, and given how much stuff they've got on their plate, what matters most to me is that they totally nail the "it's about rockets" part without getting too distracted with other things.

I agree you don't want to go crazy with that, but what is the purpose of manned (or Kerballed) space exploration?  It is not actually exploring space per se, but exploring what is in space. That includes planets, and the most interesting planets have atmospheres and some have lakes and oceans.

To me, having some underwater (or undermethane if you are on Titan) support is akin to what the very desired and very overdue aircraft props are in the new DLC-- way to aid in exploring other worlds.  (As much as I like building planes, the real justification is Duna and Eve exploration.)  Unlike interstellar travel, this is very near future tech--probably doable right now if the funding was there:

https://www.nasa.gov/content/titan-submarine-exploring-the-depths-of-kraken/

 

Having said all that, Nate Simpson has also stated that they see KSP2 as having a long lifespan of continuous development.  I think a lot of us (though we know better) are expecting a completed game out of the box. As Scott Manley said in his interview with Nate that he posted yesterday, the main thing is to get the base game correct--the stuff you cannot change later.  I think we can expect many of these other features to trickle out over the next several years.

Edited September 3, 2019 by Klapaucius

[dave1904]

46 minutes ago, Dragon01 said:

Call it a thought shortcut. Metallic hydrogen as KSP devs implement it is not a thing. It may exist in laboratory, or in a gas giant's core. It's not a rocket fuel, and of no practical use due to pressures involved in keeping it in metallic state. The cesium thing is pure technobabble, and there's no place for that in KSP. Again, the problem is going against KSP's educational role. You can't use a game like this to tell people outright falsehoods, because aside from obvious things like Kerbals, everything else in the game is at least qualitatively correct.

Also, the electric engines aren't beyond our reactor technology. We have GW-level reactors in nuclear power plants, hardly any electric engine uses that much power. Submarines use compact reactors that still produce megawatts of power, which is sufficient to power VASIMRs, PITs, MPDs and what have you. What is a problem is: 1). Making a cooling system for one of those small enough (or, more Kerbally, a rocket big enough) for such a reactor to be launched into space. 2). Getting paperwork to actually send one of those into space. 

I stand by my point the we lack the tech for it currently and we are far from sending anything close to MW reactors to space. How can you use a powerplant or a nuclear submarine as an argument? Lacking a cooling system is lacking tech for it. You cannot create paperwork for something that doesn't exist yet and even if it did exist it would not be worth it because as you yourself pointed out I believe NTR are a better solution. 

Noone has ever considered pressurizing MH. Some think it could be metastable. I think the water cooling is quite a funny cooling solution myself  I am not disagreeing with you about MH being improbable and probably even impossible. My point is that to go interstellar they need to be a bit speculative technobabble as you put it. Electric engines are also not a great solution for interstellar travel either. I mean chemical rockets can do it yeah but time.... I am very curious how that will work anyway. 

[Guest]

9 minutes ago, dave1904 said:

I stand by my point the we lack the tech for it currently and we are far from sending anything close to MW reactors to space. How can you use a powerplant or a nuclear submarine as an argument? Lacking a cooling system is lacking tech for it. 

Submarine reactors are low mass, high power nuclear reactors that are in daily use in US and Russian military. If you want to design an MW-class space reactor, your best bet is to start with a submarine nuclear reactor and try to trim the weight down. That we don't have a cooling system operating right now at the same level of readiness doesn't mean we couldn't build it.

For the record, a reactor of the kind used on Los Angeles-class submarine weights 110T and produces 26MW electric, and 150MW thermal. The first Los Angeles-class was built in 1972 (which is why I was able to find information on its reactor, newer ones are classified). You could launch it on some upgraded versions of Saturn V (it was even the right diameter, about 10 meters). We could have had MW-class space-based nuclear reactors during late Apollo era, if people running the space program really wanted to. Radiators would have been developed, they would have added plenty of weight, but they aren't magic, we've known how to make them way back then. 

Why didn't it happen, then? Money, politics and the Space Shuttle, in a nutshell. We have all the technology and engineering to make a 30MW nuclear reactor that you could launch on a Falcon Heavy. The company trying to build them (Hyperion Power Generation, later Gen4) doesn't appear to have gotten to selling them yet, but again, it's economics and paperwork, not a technological problem. 

[Incarnation of Chaos]

22 minutes ago, dave1904 said:

I stand by my point the we lack the tech for it currently and we are far from sending anything close to MW reactors to space. How can you use a powerplant or a nuclear submarine as an argument? Lacking a cooling system is lacking tech for it. You cannot create paperwork for something that doesn't exist yet and even if it did exist it would not be worth it because as you yourself pointed out I believe NTR are a better solution. 

Noone has ever considered pressurizing MH. Some think it could be metastable. I think the water cooling is quite a funny cooling solution myself  I am not disagreeing with you about MH being improbable and probably even impossible. My point is that to go interstellar they need to be a bit speculative technobabble as you put it. Electric engines are also not a great solution for interstellar travel either. I mean chemical rockets can do it yeah but time.... I am very curious how that will work anyway. 

And this is the line nobody seems to see; we don't have MW capable reactors in space. But it's not because we're still figuring out Fission; it's because of political and engineering reasons. A MW reactor suitable for space isn't speculative; it's literally getting the right people and money to build it. Cooling down the reactor isn't speculative; it's a matter of engineering and radiators. Metallic Hydrogen isn't speculative; it's predicted by physics. Metastable Metallic Hydrogen IS speculative and hasn't been created in ANY experiments so far; IT ISNT a matter of funding/politics/engineering. We legitimately don't know if Metallic Hydrogen can ever be stabilized at room temperature. This is the entire argument that everyone seems to be missing, and what separates it from MW reactors, Orion Drives and even bloody fusion torches and antimatter.

[OHara]

10 hours ago, nejc said:

I'm not sure what this means  ["One of the earlier engines that unlocks the interplanetary progression is metallic hydrogen engines."]

It could mean (and I think it does mean) that metallic hydrogen---with its extremely high energy-density if you believe that Harvard paper---motivates Kerbals to develop magnetic nozzles so they can use its full potential exhaust-velocity without vaporizing their rocket nozzles.   Then the magnetic nozzles and plasma confinement are ready to use with nuclear engines.
At least we are on record saying that we hope that we can pick which parts in the tech-tree that we actually use on rockets (as we can choose in KSP1).

10 hours ago, nejc said:

Didn't Scott suggest this in the interview? To keep the planets on rails, but make spacecraft under n-body influence? Then the developer said that they want to preserve a lot of the core game-play.

Yes, at least I understood that to be his suggestion. 
I could argue with the response;  I think KSP could preserve the core game-play without the SOI approximation.  But, I see how keeping the current SOI system is by far the safer choice for KSP2 from the developers point of view.  Maybe the infrastructure for Rask-Rusk and the constant-acceleration under warp will enable a simpler restricted N-body mod.

Although, the 'custom solution' for Rask/Rusk could be something simpler like the Sigma Binary mod, with the smaller body fully in the SOI of the larger, as if the smaller were a moon of the larger, and then the larger body orbiting the common barycenter, that barycenter having no SOI and existing only as a parent for the larger of Rask/Rusk for purposes of orbital parameters.

14 hours ago, KerikBalm said:

A little cesium mixed in isn't going to contain the hydrogen. Cs-H chemical bonds aren't going to help

Probably, the idea of the cesium is that it is easily ionized, so there will be plenty of Cs+ ions created in the hot the reaction chamber. Then these charged ions can be steered by magnetic fields to make a nozzle.  The molecular hydrogen is not going to ionize much, even at 7000K.  Somebody here who knows plasma physics might be able to explain how the Cs sheepdogs can herd those H2 sheep.  I imagine this nozzle cannot hold much pressure of H2, so this might be a low-thrust engine.

There is another area where KSP1 underestimates technology.  The empty fuel tanks have several times more dry mass than one would expect, given their fuel capacity.  This, and the strangely heavy engines, balance out the 1/10 solar system so the game is not too easy.   

Maybe the orbital construction facility could somehow avoid the need for such heavy fuel tanks, so that craft built there could have higher full/empty mass-ratio and thus greater dV, depending less on optimistic assumptions about near-future technology.

[Guest]

I know close to absolutely nothing about this topic (have some undergraduate chemistry studies from nearly 30 years ago but that's it) but I have gotten curious and puttered around digging up stuff about metallic hydrogen. It's quite fascinating really. Some things I've found that either haven't been mentioned or contradict some of the stuff @KerikBalm and others have said here -- note that I have no independent way of assessing who's right here, I'm just reporting what I've found.

• It has not been conclusively demonstrated that metallic H is not meta-stable. That's still an open question. The experiment intended to test this failed because the diamond anvil broke and the (incredibly tiny) sample of metallic H was lost. However, the expert consensus does appear to be that it's unlikely that metallic H is metastable.
• There is some early theoretical research on improving stability and lowering the pressure needed for the phase change by doping and alloying. Some models and early experiments indicate that alloying hydrogen with alkali metals could help: LiH₆, AcH₈, and LaH₁₀ have come up, as has H doped with B or Bo. An experiment using Ar failed however.

I didn't find anything about making hydrogen plasma more manageable by adding Cs though. 

Bottom line -- metallic H as a workable material does appear to be speculative science rather than speculative engineering, but it isn't magic yet. It does require a bit more suspension of disbelief than, say, the Orion or Daedalus drives but IMO not as much as the Alcubierre drive. We have no idea how to go about producing matter with negative mass, whereas we do know what we need to do to find out if metallic hydrogen is metastable enough to be used as rocket fuel, or if it could be made so through alloying or doping.

And even if pure metallic H is proven not to be metastable, it still leaves the door open a crack -- someone could still discover an alloy or a mix of dopants that would do the trick.

[Xd the great]

28 minutes ago, Brikoleur said:

metallic H as a workable material does appear to be speculative science rather than speculative engineering, but it isn't magic yet. It does require a bit more suspension of disbelief than, say, the Orion or Daedalus drives but IMO not as much as the Alcubierre drive. We have no idea how to go about producing matter with negative mass, whereas we do know what we need to do to find out if metallic hydrogen is metastable enough to be used as rocket fuel, or if it could be made so through alloying or doping.

And even if pure metallic H is proven not to be metastable, it still leaves the door open a crack -- someone could still discover an alloy or a mix of dopants that would do the trick.

Aaaaaaand... the dopants and materials used for alloying is so great that ISP drops to 70.

just kidding

[Sigma88]

2 hours ago, OHara said:

Although, the 'custom solution' for Rask/Rusk could be something simpler like the Sigma Binary mod, with the smaller body fully in the SOI of the larger, as if the smaller were a moon of the larger, and then the larger body orbiting the common barycenter, that barycenter having no SOI and existing only as a parent for the larger of Rask/Rusk for purposes of orbital parameters.

I would be surprised if the "custom solution" he talked about is the solution I adopted for SB.

Rask/Rusk look like they have more or less the same mass, this doesn't really give a nice result using SB. it's possible but a bit weird.

I think they developed a tech that allows both bodies to be equivalent rather than having to choose a primary and a secondary (like SB does)

My guess would be having two spheres of influence with the same "priority" so that the craft is under the influence of the closest body, and maybe a third sphere of influence once you are far enough so that the craft orbits the barycenter directly instead of just one or the other.

something like this:

Spoiler

 

Either that or a completely new system with only one sphere of influence (the barycenter) that "automatically" tracks the two bodies and the craft and switches the orbit when needed.

Edited September 4, 2019 by Sigma88

[Guest]

Since we're guessing:

(1) Put Rusk and Rask on rails, orbiting a point between them. Don't make that point a barycentre with its own SoI however.

(2) Give Rusk and Rask overlapping spheres of influence so that the point they orbit is within (and masked by) them.

(3) Sum the gravitational force vectors affecting a craft inside the area of overlap. 

I believe this would be a crude approximation of a 3-body solution to the problem, omitting some of the complications but still making it somewhat realistic as well as different enough to be a cool problem. 

I think they could also model it under the hood as patched conics within the closer planet's SoI, modified by a constant acceleration toward the other. They're already doing brachistochrone trajectories with long burns and this is pretty much the same problem, except that the "burn vector" (=acceleration imparted by the other body) changes depending on your position. So they could use whatever system and UI they have to plan brachistochrone trajectories to plan orbits around Rask and Rusk as well.

Edited September 4, 2019 by Guest

[Sigma88]

23 minutes ago, Brikoleur said:

Since we're guessing:

(1) Put Rusk and Rask on rails, orbiting a point between them. Don't make that point a barycentre with its own SoI however.

(2) Give Rusk and Rask overlapping spheres of influence so that the point they orbit is within (and masked by) them.

(3) Sum the gravitational force vectors affecting a craft inside the area of overlap. 

I believe this would be a crude approximation of a 3-body solution to the problem, omitting some of the complications but still making it somewhat realistic as well as different enough to be a cool problem. 

this sounds great, however I wonder if this can be integrated with the current gameplay (providing apo/peri -apsis, orbital period etc)

[dave1904]

11 hours ago, Dragon01 said:

Submarine reactors are low mass, high power nuclear reactors that are in daily use in US and Russian military. If you want to design an MW-class space reactor, your best bet is to start with a submarine nuclear reactor and try to trim the weight down. That we don't have a cooling system operating right now at the same level of readiness doesn't mean we couldn't build it.

For the record, a reactor of the kind used on Los Angeles-class submarine weights 110T and produces 26MW electric, and 150MW thermal. The first Los Angeles-class was built in 1972 (which is why I was able to find information on its reactor, newer ones are classified). You could launch it on some upgraded versions of Saturn V (it was even the right diameter, about 10 meters). We could have had MW-class space-based nuclear reactors during late Apollo era, if people running the space program really wanted to. Radiators would have been developed, they would have added plenty of weight, but they aren't magic, we've known how to make them way back then. 

Why didn't it happen, then? Money, politics and the Space Shuttle, in a nutshell. We have all the technology and engineering to make a 30MW nuclear reactor that you could launch on a Falcon Heavy. The company trying to build them (Hyperion Power Generation, later Gen4) doesn't appear to have gotten to selling them yet, but again, it's economics and paperwork, not a technological problem. 

Or maybe its because we don't need reactors that can power vasmir. Propulsion is not what is stopping us from getting to Mars. Your right about the shuttle and the iss was also far to expensive. Saturn capable booster could have build a long term space station for a fraction of the cost assuming you could get enough launches to keep the costs down. Sls will be a failure to because after all it will never be used. It will probably be cheaper to launch a 100 ton payload over 3 expendable FH missions and assemble them in orbit than using an Sls once. I don't know the expendable FH leo launch mass. I'm just assuming 30tons....Besides that 10 FH will be probably cheaper than 1 Sls launch. 

I think your a bit optimistic with the reactor part but out of curiosity and assuming we had radiators developed. What kind of mass do you think a 30 mw reactor would have including the cooling solution? 

[KerikBalm]

2 hours ago, Brikoleur said:

(3) Sum the gravitational force vectors affecting a craft inside the area of overlap. 

I believe this would be a crude approximation of a 3-body solution to the problem, omitting some of the complications but still making it somewhat realistic as well as different enough to be a cool problem.

Doing this means that it won't be a conice section, so patched conics would have to be out.... they claim to have a "bespoke solution", but any such solution needs to throw out patched conics.

3 hours ago, Brikoleur said:

I know close to absolutely nothing about this topic (have some undergraduate chemistry studies from nearly 30 years ago but that's it) but I have gotten curious and puttered around digging up stuff about metallic hydrogen. It's quite fascinating really. Some things I've found that either haven't been mentioned or contradict some of the stuff @KerikBalm and others have said here -- note that I have no independent way of assessing who's right here, I'm just reporting what I've found.

• It has not been conclusively demonstrated that metallic H is not meta-stable. That's still an open question. The experiment intended to test this failed because the diamond anvil broke and the (incredibly tiny) sample of metallic H was lost. However, the expert consensus does appear to be that it's unlikely that metallic H is metastable.

I've already addressed this in another post, you're talking 2017 results, we have Jun 2019 results

 

3 hours ago, Brikoleur said:

• There is some early theoretical research on improving stability and lowering the pressure needed for the phase change by doping and alloying. Some models and early experiments indicate that alloying hydrogen with alkali metals could help: LiH₆, AcH₈, and LaH₁₀ have come up, as has H doped with B or Bo. An experiment using Ar failed however.

I didn't find anything about making hydrogen plasma more manageable by adding Cs though. 

Bottom line -- metallic H as a workable material does appear to be speculative science rather than speculative engineering, but it isn't magic yet. It does require a bit more suspension of disbelief than, say, the Orion or Daedalus drives but IMO not as much as the Alcubierre drive. We have no idea how to go about producing matter with negative mass, whereas we do know what we need to do to find out if metallic hydrogen is metastable enough to be used as rocket fuel, or if it could be made so through alloying or doping.

And even if pure metallic H is proven not to be metastable, it still leaves the door open a crack -- someone could still discover an alloy or a mix of dopants that would do the trick.

And I already addressed that too in the second half of this linked post

4 hours ago, OHara said:

Probably, the idea of the cesium is that it is easily ionized, so there will be plenty of Cs+ ions created in the hot the reaction chamber. Then these charged ions can be steered by magnetic fields to make a nozzle.  The molecular hydrogen is not going to ionize much, even at 7000K.  Somebody here who knows plasma physics might be able to explain how the Cs sheepdogs can herd those H2 sheep.

They can't.

It seems you're describing something like turning a plasma window into a rocket nozzle, which can't be done as far as I can tell, because of the magnetic coils needed to shape the field. So to have a plasma cylinder, the interior wouldn't be plasma (just like you can't have a plasma torus without enclosing it on all sides, a plasma torus is not going to be a rocket nozzle)

 

 

 

[dave1904]

12 hours ago, Incarnation of Chaos said:

And this is the line nobody seems to see; we don't have MW capable reactors in space. But it's not because we're still figuring out Fission; it's because of political and engineering reasons. A MW reactor suitable for space isn't speculative; it's literally getting the right people and money to build it. Cooling down the reactor isn't speculative; it's a matter of engineering and radiators. Metallic Hydrogen isn't speculative; it's predicted by physics. Metastable Metallic Hydrogen IS speculative and hasn't been created in ANY experiments so far; IT ISNT a matter of funding/politics/engineering. We legitimately don't know if Metallic Hydrogen can ever be stabilized at room temperature. This is the entire argument that everyone seems to be missing, and what separates it from MW reactors, Orion Drives and even bloody fusion torches and antimatter.

People get it and understand your point but are not bothered by it. I'm honestly not. Mods fix my problems. 

[Guest]

7 minutes ago, dave1904 said:

I think your a bit optimistic with the reactor part but out of curiosity and assuming we had radiators developed. What kind of mass do you think a 30 mw reactor would have including the cooling solution? 

I'll do one better: I can calculate that. This article claims that Hyperion/Gen4 designed a mini-reactor (for terrestrial use) that weighs 20T, produces 30MW electric and 70MW thermal:
https://www.nextbigfuture.com/2008/10/power-to-overall-weight-ratio-aspect-of.html
This seems credible enough for estimations, so let's go with that. The reactor produces 70MW of thermal power, out of which 30MW is used. This gives 43% efficiency, which is pretty good. Efficiency for Brayton cycle is given by 1-(T1/T2). T2 is the input temperature (what the reactor makes), T1 is the output temperature (what goes into radiators). So, with 43% efficiency, the ratio output/input ratio is 0.57. According to Wikipedia, the temperature in the primary coolant loop is supposed to be 500 degrees Celsius. For the equation we need to convert to Kelvin, so 773K. Multiplying that by temperature ratio, we get 440K, or 163 degrees Celsius. This is hotter than the ISS cooling loop, and that's great... because radiator power is A*s*T^4. A is area, s is Stefan-Boltzmann constant (about 5.7*10^-8) and T is temperature. To reject 40MW at 440K, you would need 18700 square meters of radiators, assuming perfect black body radiators (in reality, you'd need more, depending on what you make them out of). ISS radiators are about 3 kilograms per square meter, if we only consider exposed panels. That gives about 56 tons of radiators. The total mass of the reactor+cooling therefore works out to 76 tons. You could launch this, plus the actual VASIMR, the turbine (the 20T figure doesn't include it) several tons of structure, spacecraft systems and propellant, on Block 2 version of the SLS.

Math saves the day again.  Note, this is not an optimal reactor design for space use. A truly space-optimized reactor would run very hot, to take advantage of temperature being to fourth power in the Stefan-Boltzmann law, and could sacrifice some thermal efficiency in order to increase its output temperature, and decrease radiator mass. Due to that T^4, radiator area plummets if you increase the temperature. A dedicated design study, as opposed to a few minutes with Google and the Windows calculator, would likely find multiple ways of cutting the overall mass of the system down. 

Of course, the fact that we don't need such a reactor played the biggest role. NTR propulsion works fine for Mars. But don't say we do not have the tech for that. It's the same as saying we don't have the tech for a Moon landing, because Saturn V tooling is gone, and its replacement is still on paper (the SLS block currently under construction doesn't quite measure up). We could, with modern technology, build a 30MW space nuclear power system able to be launched with an LV that we could also build with modern technology. No magic needed, except to turn all those bureaucrats into toads so you can launch it (and you probably wouldn't need that much magic for that, either  ).

[Guest]

2 hours ago, KerikBalm said:

And I already addressed that too in the second half of this linked post

That article discusses one possible alloy (LiH₆).

Again, I am a complete layman in this area but I still get the strong feeling that you're jumping the gun if you're summarily dismissing all possibilities of a metastable hydrogen alloy or doped mixture as "magic." AFAICT the evidence just isn't in. High-pressure physics is hard, computer models have limited predictive power, and a lot of the experiments just haven't been made. I'll agree that it seems unlikely, but "unlikely" isn't "magic."

Edited September 4, 2019 by Guest

[Mr. Peabody]

I have observed two major groups of players during my tenure on the forum:

1. True space enthusiasts who would like KSP to become a more realistic space "simulation."
2. Players who don't really care whether KSP is realistic and just want to have fun with a great game.

The differences between these two camps is irreconcilable. It is literally impossible to please both. Therefore, KSP devs have attempted to walk a thin line, making the game just realistic enough to pacify the enthusiasts while still making it easy enough for regular players and those who may not have enough time for a realistic simulation. I must admit that I am of the second group. I just don't have the time to build and fly realistic spacecraft/aircraft.

I read somewhere that only 25% of KSP players have landed on the Mun. That may or may not be an accurate indication of the skill level of most KSP players. If the majority of players want a simulation, then it is only fair that the devs take the game in that direction. If the opposite is true, than it should certainly remain as it now is.

I can understand where the space "nerds" are coming from. You guys eat, sleep, and breathe space. But it's like a movie adaptation of your favorite book. There are some zealots who really want the movie script to mirror the book, but what is interesting as a book may not be enough to capture an audience's attention in a movie format. Therefore, in order to appeal to the "masses," the producers add scenes to the movie that are not included in the original book. This drives the "zealots" nuts, but it makes the movie more interesting for the majority of those concerned. It's like that with KSP too. The diversity of the player-base is one of the factors that makes KSP a great game. It is my hope that the devs can come to a solution that is agreeable to everyone.

[Xd the great]

7 minutes ago, The Dunatian said:

It is my hope that the devs can come to a solution that is agreeable to everyone.

Or just let modders do their work and make the game hardcore.

[KerikBalm]

47 minutes ago, Brikoleur said:

 

That article discusses one possible alloy (LiH₆).

Again, I am a complete layman in this area but I still get the strong feeling that you're jumping the gun if you're summarily dismissing all possibilities of a metastable hydrogen alloy or doped mixture as "magic." AFAICT the evidence just isn't in. High-pressure physics is hard, computer models have limited predictive power, and a lot of the experiments just haven't been made. I'll agree that it seems unlikely, but "unlikely" isn't "magic."

What you said previously

Quote

There is some early theoretical research on improving stability and lowering the pressure needed for the phase change by doping and alloying. Some models and early experiments indicate that alloying hydrogen with alkali metals could help: LiH₆, AcH₈, and LaH₁₀ have come up, as has H doped with B or Bo. An experiment using Ar failed however

I linked to LiH6... one of the ones you mentioned. They can't just pull a metal out of thin air and say that solves it... thats speculative science. Also the studies are showing that the increased stablity comes with decreased pressure required to metalize it. This decreased pressure also means decreased energy storage. These alloying experiments still show the need for >100 GPa to keep it stable (and not much more to form it). The data is showing that the storage pressure is still way way too high, and that the stored energy is much lower. That means you lose your Isp advantage, while still having ridiculously heavy tanks.

As long as storage required mechanical pressure exerted by tanks, we might as well be proposing storing energy in a spring... Even if the metastability allows you to relax the pressure by a factor of 2, that's just 2x better than mechanical storage, as in a spring...

[Guest]

20 minutes ago, KerikBalm said:

thats speculative science

I agree that it's speculative science. I disagree that it's MAGICK!!!!111one

[nejc]

29 minutes ago, Brikoleur said:

I agree that it's speculative science. I disagree that it's MAGICK!!!!111one

It's the difference between handwavium and unobtainium. Handwavium being magic, unobtainium being speculative science.

At least for me this distinction is not important here, because we have a solution that includes neither. Beefed up project Timberwind NTRs would only be speculative engineering.

1 hour ago, The Dunatian said:

I have observed two major groups of players during my tenure on the forum:

1. True space enthusiasts who would like KSP to become a more realistic space "simulation."
2. Players who don't really care whether KSP is realistic and just want to have fun with a great game.

The differences between these two camps is irreconcilable. It is literally impossible to please both.

In most cases it is irreconcilable yes. But in this particular case using more powerful NTRs wouldn't make any difference for group 2, but would make a difference for group 1.

[dave1904]

4 hours ago, Dragon01 said:

I'll do one better: I can calculate that. This article claims that Hyperion/Gen4 designed a mini-reactor (for terrestrial use) that weighs 20T, produces 30MW electric and 70MW thermal:
https://www.nextbigfuture.com/2008/10/power-to-overall-weight-ratio-aspect-of.html
This seems credible enough for estimations, so let's go with that. The reactor produces 70MW of thermal power, out of which 30MW is used. This gives 43% efficiency, which is pretty good. Efficiency for Brayton cycle is given by 1-(T1/T2). T2 is the input temperature (what the reactor makes), T1 is the output temperature (what goes into radiators). So, with 43% efficiency, the ratio output/input ratio is 0.57. According to Wikipedia, the temperature in the primary coolant loop is supposed to be 500 degrees Celsius. For the equation we need to convert to Kelvin, so 773K. Multiplying that by temperature ratio, we get 440K, or 163 degrees Celsius. This is hotter than the ISS cooling loop, and that's great... because radiator power is A*s*T^4. A is area, s is Stefan-Boltzmann constant (about 5.7*10^-8) and T is temperature. To reject 40MW at 440K, you would need 18700 square meters of radiators, assuming perfect black body radiators (in reality, you'd need more, depending on what you make them out of). ISS radiators are about 3 kilograms per square meter, if we only consider exposed panels. That gives about 56 tons of radiators. The total mass of the reactor+cooling therefore works out to 76 tons. You could launch this, plus the actual VASIMR, the turbine (the 20T figure doesn't include it) several tons of structure, spacecraft systems and propellant, on Block 2 version of the SLS.

Math saves the day again.  Note, this is not an optimal reactor design for space use. A truly space-optimized reactor would run very hot, to take advantage of temperature being to fourth power in the Stefan-Boltzmann law, and could sacrifice some thermal efficiency in order to increase its output temperature, and decrease radiator mass. Due to that T^4, radiator area plummets if you increase the temperature. A dedicated design study, as opposed to a few minutes with Google and the Windows calculator, would likely find multiple ways of cutting the overall mass of the system down. 

Of course, the fact that we don't need such a reactor played the biggest role. NTR propulsion works fine for Mars. But don't say we do not have the tech for that. It's the same as saying we don't have the tech for a Moon landing, because Saturn V tooling is gone, and its replacement is still on paper (the SLS block currently under construction doesn't quite measure up). We could, with modern technology, build a 30MW space nuclear power system able to be launched with an LV that we could also build with modern technology. No magic needed, except to turn all those bureaucrats into toads so you can launch it (and you probably wouldn't need that much magic for that, either  ).

We don't lack the technology for the saturn v. We would have to redevelop the whole manufacturing part of it and redesign the whole rocket most likely since it was basically hand build. Sad thing is a redesigned saturn with improvements would be cheaper than the sls. I wouldn't be surprised if the launch cost of the sls was 500 million plus. The funny thing is that your vasmir, reactor and radiotors would be most likely way cheaper to assemble in orbit with FH. SLS is already a failure. 

I cannot understand why you say we have the technology but would need design a reactor and radiators optimized for space. Is that not lacking technology? Just because I say we lack the technology does not mean we lack the understanding to develop it. Anyway I'm going to Google the term technology nice post. 

 

[Guest]

1 minute ago, dave1904 said:

I cannot understand why you say we have the technology but would need design a reactor and radiators optimized for space. Is that not lacking technology? Just because I say we lack the technology does not mean we lack the understanding to develop it. Anyway I'm going to Google the term technology nice post. 

We have the technology. What we don't have is an operational design (we do have plenty of paper ones, though). With the knowledge and information we have, we could start one. Check out the TRL concept: https://en.wikipedia.org/wiki/Technology_readiness_level

There's quite a lot of steps between a technology and a physical device that uses it. We do have all the technology needed to build a Saturn V. What is missing is engineering and tooling needed to economically produce it. There's also a lot of stages between something that has been demonstrated, and something that can be mass produced. However, what matters is that going through all those is a matter of money and dealing with bureaucracy. No amount of dough will make metallic hydrogen metastable, but it might get you a 30MW nuclear reactor in orbit. The US might have political reservations about this, but you could probably bribe the Russians to clear it for launch (though you'd also have to donate to their SHLV program to get it on track).

[Tw1]

With the engines, I do hope they're not going to be too op. One good thing about KSP1 is dispite the tech tree, most parts do have their neche. 

Hopefully, the need to mine or pay excessive prices for some reasorces offsets the more powerful engines, so they have their niches. 

(I really hope they do something better with career this time. I would like to play with cost being an issue but remain uninterested in the current game mechanics) 

[KerikBalm]

I just hope they have LANTR NTRs to go alongside the metallic hydrogen-water engine, and a nuclear lightbulb or liquid core NTR to go along with this technobable about cesium doped metallic hydrogen with a magnetic nozzle.