Ship Deck plans..

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Daeglan Daeglan's picture
Ship Deck plans..

I have noticed a decided lack of ships in the game...And a decided lack of deck plans...which made me a little sad...

ORCACommander ORCACommander's picture
there is a ship combat book

there is a ship combat book in the pipeline but it is a few items down the list

SquireNed SquireNed's picture
I think there have been some

I think there have been some homebrew ship plans. I made one for... something. I'd have to dig to find it.

Daimonin Daimonin's picture
Hmm I have some homebrew

Hmm I have some homebrew stuff I can share here.... It's not deck plans, but more of a way to integrate ship combat into the game a little. Yeah, the core book says don't do it, but A: one character invested in pilot, and B: physical transport exists. Therefore C: Someone will try and use a ship in combat.

Dropbox link: https://dl.dropboxusercontent.com/u/17358196/Ships.ods
it's not perfect, and probably has a ton of holes, but I think it'll work till something better comes along. As much as possible is based on the little bit of info on ships that there is (mostly the weapon damage multipliers). Travel times are pretty much BS.

Trappedinwikipedia Trappedinwikipedia's picture
I suspect that deck plans

I suspect that deck plans would be pretty confusing in a setting like EP, where ships are either spun for gravity or simply lack it. There'd be a lot of very 3d spaces and flattened ring projections to contend with. There could definitely be more ship designs though.

Daeglan Daeglan's picture
I have seen it done.

I have seen it done. flattening is not that big of a deal.

If we can flatten a globe...

boomzilla boomzilla's picture
freighter layout

In the canonical adventure "Glory", there is a (somewhat abstracted) layout of a specific freigher. I reproduced the text + images + fan creations on my page here. (It contained spoilers for "Glory", so if you're a player, and your GM intends to run this one, better to not view my page there).

Besides this, I too have thought a lot about spaceship + hab layouts. And have not found a lot of resources, alas. I mean, not a lot of resources in the entire realm of science fiction (not just Eclipse Phase). Difficult for us boring flatlanders to figure out freefall life, I think :)


Daeglan Daeglan's picture
I saw this one and was...

I saw this one and was....unimpressed. I can draw a bunch od squares and put numbers on them. I would not however call it a deck plan.

Chernoborg Chernoborg's picture
In general I think the Devs

In general I think the Devs like to keep things fairly fluid like that. It promotes making it YOUR game than leading you around by a leash.

That said, Atomic Rockets, http://www.projectrho.com/public_html/rocket/, is an excellent resource for figuring out just what should be in any particular ship. I too have spent a fair bit of time doodling up deck plans for EP ships as part of a size comparison thing i did a while ago. They're all pencil on graph paper though so I don't know if that's good enough for your purposes.

Oh, and there's the Annora Arabella , http://www.studio-302.com/?p=41 , from the Quickstart Rules adventure. They're better that the Song Cai Flower but still a bit vague.

Current Status: Highly Distracted building Gatecrashing systems in Universe Sandbox!

boomzilla boomzilla's picture
Quote:

Quote:

I really liked Adam Jury’s attitude on the maps, specifically the lack of a size legend. “The ship is the size you need to have an awesome game!”

I just want detailed measurements on *everything*, dammit! I'm just that sort of nerd. :)

Yeah, EP tends to be loose about this sort of thing. And I'm not even saying that's a bad thing: not every RPer get excited about statting a vehicle using the trig and logarithmic functions you find in a GURPS vehicle builder, haha.

Really, my approach to narrative quantification has disadvantages of its own: the "clomping foot of nerdism". I totally see myself in that :/


ThatWhichNeverWas ThatWhichNeverWas's picture
Handwavium overload.

Atomic Rockets is nice (although I hate the layout) but EP has enough futuretech to make the site of limited use - for example, the vast majority of craft would arguably be Torchships.

There simply aren't enough values for advanced tech - How big does the fuel/propellant tank for a Metal-Hydrogen engine have to be? How much volume do I need for a Stepped heat exchange system? How much fluid do I need for a Droplet Radiator?

More practically, I'm experimenting with using exploded isometric diagrams for actual maps. Results are promising!

In the past we've had to compensate for weaknesses, finding quick solutions that only benefit a few.
But what if we never need to feel weak or morally conflicted again?

Lazarus Lazarus's picture
ThatWhichNeverWas wrote:. .

ThatWhichNeverWas wrote:
. . .There simply aren't enough values for advanced tech - How big does the fuel/propellant tank for a Metal-Hydrogen engine have to be?. . .

That depends upon the maximum Δv you want the ship to be able to obtain. According to Atomic Rockets the projected exhaust velocity for Metallic Hydrogen is 17,000 m/s. Other pages tell you how to convert that to specific impulse and how to use specific impulse to calculate your Δv. Now you're right in that it doesn't actually tell you how big that tank will be but it does mention things such as the fact that the storage has to handle millions of atmospheres of pressure. With that information I could fabricate some rough numbers if I had to. I could do something such as assume that the walls of the container will need to be 30cm thick with the approximate density of iron.

If we assume a ship with a mass similar to the space shuttle's orbiter vehicle while carrying a payload we are looking at around 100 metric tons. If we want a maximum Δv of 10 km/s then 44.53% of the mass needs to be metallic hydrogen. If we assume a density of .8 grams per cubic cm then we need a sphere 2.37m in radius. A 30 cm thick shell with the density of iron would weigh close to 189 tons which tells us that our fuel tank is too heavy (since the tank and fuel are 233% of the total mass of the ship).

So this means we will need to re-evaluate some of our starting hypotheses. Either we have to have a bigger ship if we assume the tank has to remain 30 cm thick with the density of iron (the cube-square rule means that eventually we will reach a point where it is possible), we need to make the walls of the tank thinner (because we are using stronger materials) and/or we need to reduce the density of the walls (we could reasonably have a density anywhere from 2-4.5 if we assume some form of carbon titanium composite).

All of which is a lengthy way of saying that while Atomic Rockets won't give you simple formulas for a ship for Eclipse Phase it will give you a lot of data that can be used to devise a framework.

My artificially intelligent spaceship is psychic. Your argument it invalid.

ORCACommander ORCACommander's picture
Or you can use the time and

Or you can use the time and true method of winging it :P

puke puke's picture
thrust and spin grav

2300AD is probably the longest running (in its various forms) and most supported "hard sci fi" setting with no artificial gravity, but it has a real shortage of deck plans.

I think the best source for this stuff is probably in Jovian Chronicles, if you can find the old books.

It is not always done deck by deck, but they usually give you modular layouts that you can potato-head into your own ships. different areas (engineering, flight deck, living) are denoted, even if not room-by-room plans. Some feature re-configurable habitat rings with modules that adjust their layout depending on if they are under thrust or under spin grav.

I can't think of any better published material, though there are a few websites with old home brew stuff that I have in an old bookmark file somewhere. And their might be something like this back in the ancient history of the Diaspora G+ community, where people shared and collected links for these sorts of deckplans.

There is even a previous thread here on these forums, but I cant remember what is in it. Maybe someone with a little time and search-foo can dredge it up.

puke puke's picture
try these threads!
ThatWhichNeverWas ThatWhichNeverWas's picture
They just keep pulling me back in. Damn you Kerbal!

Lazarus wrote:
That depends upon the maximum Δv you want the ship to be able to obtain. According to Atomic Rockets the projected exhaust velocity for Metallic Hydrogen is 17,000 m/s. Other pages tell you how to convert that to specific impulse and how to use specific impulse to calculate your Δv. Now you're right in that it doesn't actually tell you how big that tank will be but it does mention things such as the fact that the storage has to handle millions of atmospheres of pressure.

You're right till here but going farther is hard. EP's metallic hydrogen is metastable through the use of electromagnetics, and if atomic rockets has numbers for magnetic containment vessels then I can't find them.
I tried using numbers from ITER, but they don't really apply thanks to the lack of shielding and the presence of room-temperature superconductors, so we have to use Handwavium.

An interesting side note is that the propulsion bus of an EP metallic hydrogen ship is going to be a lot shorter than you'd expect.

Lazarus wrote:
A 30 cm thick shell with the density of iron would weigh close to 189 tons which tells us that our fuel tank is too heavy (since the tank and fuel are 233% of the total mass of the ship).

The math is a lot easier to handle if you start with what you need for the Scenario (The payload and structural mass), use the Tsiolkovsky rocket equation to get the propellant/fuel mass for that, and then go from there.

In the past we've had to compensate for weaknesses, finding quick solutions that only benefit a few.
But what if we never need to feel weak or morally conflicted again?

Trappedinwikipedia Trappedinwikipedia's picture
Conveniently there are

Conveniently there are actually semi-official numbers for the masses and delta-vs of published eclipse phase ship classes. They're kind of hard to find, but they're in the eclipse phase naval stuff PDF that Arenamontanus put together a while ago.

http://www.aleph.se/EclipsePhase/EP%20naval%20strategy.pdf

From those numbers, an 11 ton SLOTV gets 17 km/s of dv from 139 tons of of metallic hydrogen.

Lazarus Lazarus's picture
ThatWhichNeverWas wrote:. . .

ThatWhichNeverWas wrote:
. . . You're right till here but going farther is hard. EP's metallic hydrogen is metastable through the use of electromagnetics, and if atomic rockets has numbers for magnetic containment vessels then I can't find them. . .

Actually, I don't recall seeing that metallic hydrogen works that way in EP. I'm not saying that you're wrong, simply that I was working from a different perspective.

Now you're correct, Atomic Rockets doesn't have any figures for the mass of a theoretical magnetic containment vessel, but then it didn't have the requirement that the containment vessel needs to be 6" thick with the density of iron. That was a figure I made up. In a similar vein I could come up with some pseudo-plausible figures based on the size and weight of coils of conductive wire.

Quote:
The math is a lot easier to handle if you start with what you need for the Scenario (The payload and structural mass), use the Tsiolkovsky rocket equation to get the propellant/fuel mass for that, and then go from there.

Actually, that was what I did. I assumed a complete payload and remass total of 100 tons, a specific impulse of 1732, and a target Δv of 10 km/s. That gave the percentage of total mass that had to be metallic hydrogen (44.53%). I had to estimate the density of metallic hydrogen from a couple of publications since people aren't completely sure but that gave me a volume which I was then able to turn into a weight for the vessel holding the remass (by expanding the dimensions of the metallic hydrogen mass).

My artificially intelligent spaceship is psychic. Your argument it invalid.

Lazarus Lazarus's picture
I hadn't seen that before but

Trappedinwikipedia wrote:
Conveniently there are actually semi-official numbers for the masses and delta-vs of published eclipse phase ship classes. They're kind of hard to find, but they're in the eclipse phase naval stuff PDF that Arenamontanus put together a while ago.

http://www.aleph.se/EclipsePhase/EP%20naval%20strategy.pdf

From those numbers, an 11 ton SLOTV gets 17 km/s of dv from 139 tons of of metallic hydrogen.


I hadn't seen that before but I did have access to some of the numbers (specifically the specific impulse estimates for EP). The only reason I used a different Isp for my metallic hydrogen was because I wanted to rely purely on data from Atomic Rockets.

I've only glanced at the PDF but all in all it seems pretty good. It looks like it still retains one of my gripes, that being that specific engines produce specific accelerations, but it hits most of the critical things such as the difficulties of stealth, producing energy, cooling ships, and sensors.

My artificially intelligent spaceship is psychic. Your argument it invalid.

ORCACommander ORCACommander's picture
doesn't the metallic hydrogen

doesn't the metallic hydrogen require an oxidizers? I recal the books mentioning Red Oxygen somwhere

Lazarus Lazarus's picture
No. A metallic hydrogen

No. A metallic hydrogen rocket is powered by allowing the metallic hydrogen to convert back to molecular hydrogen. This generates intense pressures which then propel the craft. It is sort of like how a group of students made a car that is powered by liquid nitrogen except of course the conversion to thrust is direct and it is multiple orders of magnitude more.

My artificially intelligent spaceship is psychic. Your argument it invalid.

ThatWhichNeverWas ThatWhichNeverWas's picture
Standards are so very, very useful.

The PDF's pretty good but I wish the Author'd listed his sources.
My only issues are the same ones I have with Automic Rockets, and arise from inconcistencies / incompatabilities with the Setting - for example, Every Gram Counts only applies to a limited degree in a setting with Commercial Shipping.

Lazarus wrote:
Actually, I don't recall seeing that metallic hydrogen works that way in EP. I'm not saying that you're wrong, simply that I was working from a different perspective.

Now you're correct, Atomic Rockets doesn't have any figures for the mass of a theoretical magnetic containment vessel, but then it didn't have the requirement that the containment vessel needs to be 6" thick with the density of iron. That was a figure I made up. In a similar vein I could come up with some pseudo-plausible figures based on the size and weight of coils of conductive wire.

It's mentioned in the description of Propulsion Systems in the core book: "Although naturally unstable, it can be stabilized with carefully controlled electrical and magnetic fields, and these field generators are an integral part of every metallic hydrogen fuel tank."
In my headcannon Metallic Hydrogen is a Type 2 Superconductor and is stabilized via Flux Pinning, but that's just me.

Actually now that you mention it, would it make sense to have a thread with semi-standardised values for EP tech, and how it effects design?
I kinda like the idea of having a single page with all the numbers/considerations in one place.

In the past we've had to compensate for weaknesses, finding quick solutions that only benefit a few.
But what if we never need to feel weak or morally conflicted again?

Lazarus Lazarus's picture
ThatWhichNeverWas wrote:. . .

ThatWhichNeverWas wrote:
. . .
Actually now that you mention it, would it make sense to have a thread with semi-standardised values for EP tech, and how it effects design?
I kinda like the idea of having a single page with all the numbers/considerations in one place.

It would. We've already got Specific Impulse for the various engines. The next thing I would probably address is the ability of an engine to produce thrust (in a mass to thrust ratio), mass to store remass (especially important for some types of fuel) and power plants (which are a factor for certain engines producing thrust such as ion drives and for storing certain remass such as anti-matter).

Mass of the hull, which would also include armor, is probably the second most critical thing to get baselined. After that you're looking at sensors, weapons, active defenses, and life support which are probably a lot easier, especially with nanofabrication capabilities (I would assume an awful lot of recycling of resources for life support).

(I say these things will be easy in terms of deckplans since by and large their internal masses and volumes are probably fairly trivial to the overall picture. Being off by an order of magnitude with a lot of these would still only have small impact of a lot of deckplans).

My artificially intelligent spaceship is psychic. Your argument it invalid.

ThatWhichNeverWas ThatWhichNeverWas's picture
Sorry about the Bump.

Just quickly touching base - I've gotten most of my basic design notes together, and am formatting them to be readable by People. I've also got basic values for MH engines, and am currently looking at Hydrogen-Remass storage, particularly Metal-Hydrides.
I also have basic hull-plating, but getting absorption values for x-ray shielding is proving to be annoying.

In the past we've had to compensate for weaknesses, finding quick solutions that only benefit a few.
But what if we never need to feel weak or morally conflicted again?

Lazarus Lazarus's picture
Hydrogen Remass

For liquid hydrogen we can use the Super Lightweight Tank for the space shuttle to give us a baseline.

The SLWT weighed 26,500 kg and held 735,601 kg of fuel/remass. For a HOx engine this would give us a storage/fuel ratio of .036.

Now it is a little tricky to use that for a baseline for pure hydrogen because what the SLWT is holding is both liquid oxygen and liquid hydrogen. However, we're just trying to get a decent estimate for a baseline, so what I did was looked at the volume of the two liquids. 553,358 l is liquid oxygen and 1,497,440 l is liquid hydrogen, so by volume about 73% of the two liquids is hydrogen. If we assume that translates directly to the weight of the storage then about 19,350 kg are used to store hydrogen and the remaining 6,150 kg are used to store the oxygen. 19,350 kg of tank used to store 106,261 kg of hydrogen gives a storage/remass ratio of about .18.

So as a rough baseline every kg of liquid hydrogen probably takes around an extra .18 kg to store. We might want to lower those numbers slightly to account for newer materials technologies in EP but all in all EP's materials don't appear to be vastly superior, so .15, .125, or .1 might be good numbers. My impression is that we probably shouldn't go below half the real world estimate which would be .09 and I think 1/3 should be an absolute limit. That makes .075 as another possibility since it is above the 1/3 limit but I am not crazy about it since it is below the 1/2 limit.

Liquid hydrogen storage is probably one of the really important numbers since I believe most ships are suppose to be fusion/plasma engines and I would assume they wouldn't really have different storage requirements. We might just want to base other storage estimates off of factors of the liquid hydrogen storage such as 5x the liquid hydrogen storage factor for metallic hydrogen.

One other thing to consider with engines is the thrust to weight ratio. The current numbers are pretty unrealistic since if you take one ship that weighs 980 tons and another ship that weighs 480 tons and you stick an identical 20 ton engine in both ships the smaller ship will only have half the acceleration of the larger ship.

Using real world examples again the F1 was the motor for the Saturn rocket booster (a HOx rocket) with a thrust to weight ratio of 94.1 (meaning 1 ton of engine provided 94.1 tons of thrust). Since the EP HOx engine is listed at 4 G's it seems like a good solution to calculate thrust to weight for the various engines is to multiple their original G rating by 25 (giving plasma engines a .25 thrust/weight ration, fusion engines a 1.25 thrust/weight ration, and MH engines a 75 thrust/weight ratio).

My artificially intelligent spaceship is psychic. Your argument it invalid.

Lazarus Lazarus's picture
Plasma and Fusion T/W

The thrust to weight ratios I'm proposing for the plasma and fusion engines are what I would call 'abstract' ratios. In the case of HOx, AM, and MH engines there is no need for a separate power plant for the production of thrust. The AM and MH engines require power for the containment of fuel but in both cases the production of thrust doesn't come from energy being injected into the remass. In the case of both plasma and fusion engines, however, energy is used to excite the remass (I'm assuming the fusion reaction is not self sustaining). That means that part of the weight in their thrust/weight ratios is the power plant that sustains the reactions.

My artificially intelligent spaceship is psychic. Your argument it invalid.

Chernoborg Chernoborg's picture
A useful thread

So this thread. http://eclipsephase.com/space-naval-combat-segway-antimatter-thread ...has one of the devs stats he calculated for the ships in the MRB. I recall him stating that he tweaked the Atomic Rockets numbers to his liking, but they should give you plenty of fodder for your builds.

Current Status: Highly Distracted building Gatecrashing systems in Universe Sandbox!

Lazarus Lazarus's picture
Are you referring to this

Are you referring to this specific post? http://eclipsephase.com/comment/10887#comment-10887

My artificially intelligent spaceship is psychic. Your argument it invalid.

Chernoborg Chernoborg's picture
Yarp! That's the one. I've

Yarp! That's the one. I've been doodling up some designs using those stats as a guideline. I jujst have to scan them and put them up somewhere. I've found that working from the payload back to the engines had yielded the best results. Moving people and cargo are the point of most of these ships so build that part and assume the tech exists to make the rest of it work. Coming up with certain standardized units also helps. Cargo containers were tricky, even now I have doubts about if they're too big. Right now I'm using a 1 sq. meter box as a base unit (the boxes in the hold of the Annora Arabella) , a 2x2x6 meter box as a ground shipping container ( about the size of a tractor trailer ), a 4x4x12 meter box as a non-vacuum rated space shipping container, and a 5x5x15 meter box for external shipping containers (cargo wise it's the same as 4x4x12, just fitted with Whipple shielding and a airlock docking collar on one end).

The Song Cai Flower mentions the ops center being a standard bridge module from any bulk freighter, so that's been factored into my designs as well.

I also figured that fusion containment bottles would be at a roughly similar size across the board , generally a 10 meter sphere with a 10 meter nozzle. AM engines use the same structure since the result is effectively the same, just replacing the machinery to initiate and sustain fusion with the AM containment unit (this is where I think the savings of using AM comes from). Check the DiscoveryII and Afterburning Fusion Engine sections of Atomic Rockets for my preferred take on EP engines.

For the Metallic Hydrogen engines, regarding the tanks themselves, the fuel is effectively a solid slug right? I had the odd idea of the tanks using what I've called the "push pop" configuration. The plate on the bottom of the tank has the sublimation field generators and the top of the tank moves down on top of the slug to maintain contact with the plate. Whether that's done with some kind of hydraulic ram or maybe have the sides of the tank threaded and the top winds down through it I don't know. I could be misreading the nature of metastable metallic hydrogen as presented in the game though.

Current Status: Highly Distracted building Gatecrashing systems in Universe Sandbox!

Lazarus Lazarus's picture
The only problem with those

The only problem with those figures is they don't tell you things like how much of the weight is engine, how much is power plant, etc.. They don't even really tell you how much is fuel although you can reverse engineer that without too much difficulty since they tell you the delta-v of the ship.

Metal hydrogen is a solid but that doesn't mean you need to push the entire body of fuel around to the motor. The fuel in the SRBs of the space shuttle doesn't move at all. Of course there's also the fact that those can't be refueled and they can't be started and stopped.

One possible design for a metal hydrogen motor would be to have fuel be in some sort of standardized plates. Since there is an electromagnetic field stabilizing the hydrogen you could lower the field over certain plates and allow them to begin converting into gaseous hydrogen. Depending on how much you lower the field would vary how rapidly the plates convert. You might go from back to front or you might go from the center of the column out (similar to how solid rockets burn).

My artificially intelligent spaceship is psychic. Your argument it invalid.

ThatWhichNeverWas ThatWhichNeverWas's picture
Designs...So...Suboptimal...

Lazarus wrote:
We might want to lower those numbers slightly to account for newer materials technologies in EP but all in all EP's materials don't appear to be vastly superior, so .15, .125, or .1 might be good numbers.

This is one place I disagree, and it's honestly the cause of most of my problems – when I look at the properties of the materials which are in common use in EP construction the numbers are... well, let's just say that the values I actually calculate look like I made them up.
Carbon Nanotubes are the prime offender as even small amounts of them in a composite can give pretty ridiculous performance improvements – for example, depending on which sources I use I get Specific Stiffness values running from 1000 to over 20,000 Mm^2/s^2.

Chernoborg wrote:
So this thread. http://eclipsephase.com/space-naval-combat-segway-antimatter-thread ...has one of the devs stats he calculated for the ships in the MRB.

I'm really not a fan of those numbers. Even from a pure storytelling point of view, the dimensions are aggravatingly small; an MH-LLOTV is a 16m*25m squat cone! What am I supposed to do with that? It may be useful for aerobraking or Warships, but for everything else it's just impractical.
I realize I'm overreacting, but both the GM and Engineer in me are grinding their teeth.

---
An odd thing about MH engines is that they should arguably be able to scale their mass-flow rate to a nigh-arbitrary degree because for all intents and purposes metallic hydrogen is a compressed gas, so the thrust/weight ratio can be pretty much whatever you need.

Quick clarifier: should I put what I've got here, or make a new thread?

In the past we've had to compensate for weaknesses, finding quick solutions that only benefit a few.
But what if we never need to feel weak or morally conflicted again?

Lazarus Lazarus's picture
ThatWhichNeverWas wrote:. .

ThatWhichNeverWas wrote:
. . .This is one place I disagree, and it's honestly the cause of most of my problems – when I look at the properties of the materials which are in common use in EP construction the numbers are... well, let's just say that the values I actually calculate look like I made them up.
Carbon Nanotubes are the prime offender as even small amounts of them in a composite can give pretty ridiculous performance improvements – for example, depending on which sources I use I get Specific Stiffness values running from 1000 to over 20,000 Mm^2/s^2.

Yeah. I've actually considered CNTs myself. I came to a realization a while back that most likely an awful lot of the things that we assume are fabricated from metal (guns, synthmorph frames, vehicle hulls, etc.) are quite likely made out of things such as CNT composites. This wasn't so much for performance reasons but because carbon is going to be much easier to get a hold of then metals.

If you would like to provide your figures I for one would love to see them. I'm pretty good with a lot of the physics but I'm not as good with the specifics of material sciences. The only thing I would suggest is that you take into account that there's going to be more than simply structural strength involved with some of the materials. As an example you can probably produce a CNT composite interior wall that is more than strong enough at only a few millimeters of thickness but if it is going to transmit sound straight through it then people are not going to be happy with it. You're also not going to be able to run wiring or tubes for carrying materials through such a thin wall. Filling it with an aerogel is a lightweight solution that deals with the noise but it still adds mass and such a solution is probably not viable since it makes retrofitting parts way more difficult. One possible idea is dual layers with each consisting of structural substrate and a layer of baffling/insulation/shielding such as an aerogel separated by an airgap (not completely separated as there would be anchors running from one structural surface to the other to keep them spaced appropriately but the majority of the space between the surfaces is an airgap).

Quote:
I'm really not a fan of those numbers. Even from a pure storytelling point of view, the dimensions are aggravatingly small; an MH-LLOTV is a 16m*25m squat cone! What am I supposed to do with that? It may be useful for aerobraking or Warships, but for everything else it's just impractical.
I realize I'm overreacting, but both the GM and Engineer in me are grinding their teeth.

The main thing I would use those figures for is to double check proposed solutions. The stats for the LLOTV don't really produce a vehicle you would have your party adventure in but that's because the LLOTV (large lander and orbit transfer vehicle) isn't much more than a vehicle for moving cargo from a transport ship to the surface of a planet. It's sort of the spaceship equivalent of one of the large trash barges you see move up and down the Hudson, although in this case it transports useful cargo rather than garbage. It probably has a relatively tiny bridge, a fairly specialized engine, and a small amount of fuel/remass and absolutely no living quarters. It is entirely possible it doesn't even have sanitary facilities as operators are expected to hold it for the few hours they are on the ship or else use their vacuum suit's facilities. Any adventures you have concerning one probably deal with things like stowing away on one, hiding something on one, or robbing one.
Quote:
An odd thing about MH engines is that they should arguably be able to scale their mass-flow rate to a nigh-arbitrary degree because for all intents and purposes metallic hydrogen is a compressed gas, so the thrust/weight ratio can be pretty much whatever you need.

No. I'm going to disagree with you here. It's not really a compressed gas. The energy comes from the metallic hydrogen sublimating to its gaseous form as the fields are turned down, so it's kind of like a dry ice rocket. That pressure has a very definite upper limit as beyond that the metallic hydrogen simply wouldn't sublimate. In theory you might be able to squeeze a little more energy out of it if the solid itself is held under pressure but it would be extremely complicated and the amount of energy would be relatively small compared to what you are already getting. In all likelihood the mass of the extra equipment required to harvest this energy would probably be greater than the benefit (I realized this when I was working up an alternate concept of using metallic hydrogen to power a plasma or fusion drive. Yes, the extra pressure would, in theory, enable a higher specific thrust but it would be a relatively small amount compared to the Isp of the plasma and fusion engines and the extra mass would bite into that. In the end you might still wind up with a small benefit but it wouldn't be worth the additional complications that would make repair and maintenance much more costly)

Quote:
Quick clarifier: should I put what I've got here, or make a new thread?

I'm all for adding it here. If things get too messy with multiple proposals strung throughout the thread one of us can eventually recompile it into a new thread, but for now it would probably complicate matters more to have the separate ideas in multiple threads.

My artificially intelligent spaceship is psychic. Your argument it invalid.

ThatWhichNeverWas ThatWhichNeverWas's picture
Nanotubes and Diamond are also great heatpipes.

Lazarus wrote:
If you would like to provide your figures I for one would love to see them. I'm pretty good with a lot of the physics but I'm not as good with the specifics of material sciences. The only thing I would suggest is that you take into account that there's going to be more than simply structural strength involved with some of the materials.
The most comprehensive resource I've got for CNTs is “Carbon nanotubes: properties and application” by Valentin N. Popov, which gives yield strengths from 11 to 63 GPa and Young's Moduli from 0.9 to 1.8 TPa. Density is harder because it depends on the size of the tube – The lowest value I've seen is 0.037g/cm3 and the largest is 1.6 g/cm3.
You're absolutely right about structural strength only being a part of the story, but it's illustrative of how different we need to think about EP tech. It also makes materials which would be ideal except for their low strength suddenly viable in compound form.

Lazarus wrote:
As an example you can probably produce a CNT composite interior wall that is more than strong enough at only a few millimeters of thickness but if it is going to transmit sound straight through it then people are not going to be happy with it. You're also not going to be able to run wiring or tubes for carrying materials through such a thin wall. Filling it with an aerogel is a lightweight solution that deals with the noise but it still adds mass and such a solution is probably not viable since it makes retrofitting parts way more difficult.
That's pretty close to what I had in mind for the lowest level of bulkhead actually – a cellular foam of Diamond/CNT composite “cells” filled with a metallic aerogel to help block non-visible light, also known as SpaceLumber :P
Practically what it means is that the mass of CNT in a composite to provide tensile strength is usually going to be negligible compared to the other materials, and so a material's strength can be largely discounted as a consideration. It's only in purely structural members that it becomes relevant.

Lazarus wrote:
No. I'm going to disagree with you here. It's not really a compressed gas. The energy comes from the metallic hydrogen sublimating to its gaseous form as the fields are turned down, so it's kind of like a dry ice rocket. That pressure has a very definite upper limit as beyond that the metallic hydrogen simply wouldn't sublimate. In theory you might be able to squeeze a little more energy out of it if the solid itself is held under pressure but it would be extremely complicated and the amount of energy would be relatively small compared to what you are already getting.
Not what I meant :P
The energy Metallic Hydrogen provides is released when it is removed from containment – and that's it. There are no reaction chambers or extraneous features necessary because it's all implicit in the mass of the tank - you just have to “open the valve”.
This means that if you want to get more thrust you just need to push it out of containment quicker, increasing the Mass Flow, with the only limitation being the forces the tank can withstand.

In the past we've had to compensate for weaknesses, finding quick solutions that only benefit a few.
But what if we never need to feel weak or morally conflicted again?

ThatWhichNeverWas ThatWhichNeverWas's picture
What Have I Done....

Basic Shipbuilding Design Assumptions – Part 1.

- 1. Fusion Power and Molecular Construction.
Fusion means that power is available in abundance. Molecular construction means that items that would be infeasible because of their complexity are easy to get. On the other hand, items which make use of rare elements are harder to get.
What this means is that systems that are power hungry or complex are more desirable than simple ones which use up more resources – a simple example is that magnetic bearings and magnetic levitation are more desirable to use than actual bearings or lubricants. If something in the real world wouldn't be practical because of manufacturing difficulty, then it is absolutely used in EP.

- 2. Altered Carbon.
Carbon is amazing, it's allotropes more so. In EP we have mass-produced synthetic diamond nanotubes and all sorts of fullerines. Individually these have incredible potential which magnifies exponentially when they are used in compounds materials – and if you can mass produce both you can have compounds which consist purely of both. For convenience, I'll refer to all diamond/fullerine composites as NRSD (Nanotube-Reinforced Synthetic Diamond)
As a rule of thumb, any structure made out of NRSD will weigh from two to twenty times less than if it was made out of steel, or up to ten times less than one of Carbon Fibre, depending on the exact purpose of the structure, with the largest difference in purely tensile structural members.

- 3. Room temperature superconductors.
Assuming the performance of the Room Temperature Superconductors available in EP is roughly equivalent to those currently used with a higher operating temperature, then the effect they have on technology cannot be understated. Not only can power be transferred with effectively no loss, incredibly high magnetic fields can be created generated with small devices without huge cooling systems to support them, drastically reducing their operating costs.
Electrodynamic Bearings and Maglev systems can be created anywhere, making them almost perfectly efficient, and any device that employs Magnetic Confinement can be significantly smaller due to the reduced coolant requirements.

- 4. Power Storage.
Working from the values given in the Corebook gear section, Superconducting batteries can provide a Specific Energy of 35-46 MJ/kg and and Energy Density of 14-19 MJ/L, depending on quality and manufacturer - this is approximately 1000 times higher than what we can achieve today.
We can use this to give a general density of ~2.45g/cm^3 for pure superconductor structures.

- 5. Life support.
Using Makers and recycling, life support is almost a closed system; food and water can be recycled nigh indefinitely, with oxygen/CO2 being the only significant exception.
Looking at Vacusits, life support packs and the GEV, we can see that an almost perfect recycling system is small/light enough to be man-portable and we can reasonably assume that larger versions are even more efficient, so the volume/mass of the life support system is going to be defined by the amount of reserves being carried.
I think that food and water would be transported together as feedstock, with a mass/volume of 30kg/25L per person per day of reserves, minimum one. Oxygen is harder to calculate but NASA's value of 0.8kg/PersonDay seems reasonable, stored either as water ice or compressed in NRSD pressure tanks, both with a volume of about 0.9L/PersonDay. Given this relatively low mass/volume ratio, it's fair to assume that the amount of oxygen held in reserve is going to be relatively large.

- 6. Ship Size and Classification.
The primary factor influencing a ship's design is it's range, or more precisely it's "travel time". The longer the ship is away from shelter/port at a time, the more radiation it's exposed to, the more self-sufficient it must be and the greater the crew's requirements for mental health.
(H+) - Ships that will be underway for less than a few days (H+) have low requirements – these are xLOTVs, Fighters, Orbital Tugs and the like. These ships aren't intended for independence, so they only need basic hull plating and no dedicated reactors – their requirements can be met purely through nuclear and superconducting battery storage. These ships will usually use MH engines due to their simplicity and low incidental mass cost.
(W+) - The next level is those that have a range up to weeks. These will have more room for the crew and dedicated reactors for power, using plasma or fusion propulsion. They'll also have proper armor and a Parasol (see below).
(M+) - Ships that can go up to months at a time begin to resemble small habitats, with serious plating and power/fuel capabilities. These are your destroyers and scum barges.
(Y+) - Above this level ships are pretty much indistinguishable from full-blown habitats, capable of indefinite survival given sufficient raw materials.

- 7. Armor.
I've had some trouble finding numbers for the radiological environment of space, so I've abstracted from the best ones I found.
In (my) EP, ships are first assembled as clusters of NRSD pressure vessels which become the cabins and storage spaces, which are then wrapped in a secondary hull of mass-produced, modular armor "tiles" separated by a vacuum-gap, each of which is easily manufactured and replaceable. W+ and larger ships will pretty much always have the capability of manufacturing/recycling tiles onboard.

The first line of defence ships have is a magnetic shield to deflect charged particles generated by superconductors embedded in the tiles. These generate a field strong enough to deflect almost all incoming charged particles whilst creating another to negate the field within the ship proper. These weigh 5.4kg/m2 of armour.
The main structure of the plate is a foam of diamond microspheres filled with compressed polyethylene with a standard mass of 50kg/m2. This mass is sufficient to make Neutron radiation largely meaningless – any source capable of delivering a meaningful dose through it will incinerate the ship entirely.
The killer is ray shielding. There are AFAIK no ways to artificially enhance a shield's X-ray cross-section, you simply have to pile on the mass with high Z materials (i.e. Lead) providing the most bang for your buck.
H+ ships can get away without any significant shielding, but W+ and larger should have a coat about 3cm thick to reduce the ambient to acceptable levels, massing at about 341kg/m2. Higher fluxes from solar weather or hostile weapons require a depth of 5+ cm with mass of 568kg/m2 , but it's possible to cheat.
The thing about Solar X-Rays and Xasers is that the vast majority of the time they come from a single direction – the Sun and the hostile ship/fleet respectively. Accordingly, you usually only need to have a single axis of the ship armoured to that level, ideally the axis with the smallest cross section. Most of the time this will be the Prow.
Ships with this "Parasol" shadow shield can orientate themselves between burns so that their thickest armour faces the largest radiation source, turning the whole ship into a faux stormshelter. This may take more mass than an actual storm shelter, but is infinitely more convenient.
H+ ships intended for extended independent use may have a partial of full Parasol to allow it to act as a de-facto shelter.
Finally, the plates have conduits allowing them to connect to the ship's coolant network.
In short: Basic Hull plating is about 350kg/m2, Normal is 695kg/m2 and Parasol/Combat armour is 925kg/m2 and higher.

- 8. Every Gram Counts.
Common wisdom is to absolutely reduce the amount of mass a given ship will have because increasing it's deltaV requires exponentially larger amounts of fuel.
However, this is slightly dampened in EP, partially due to the presence of fuel depots and fuel refineries, but mostly because it's become an economic venture: rather than shifting as much as possible within budget, the goal is to make the greatest profit on a mission with a set deltaV.
Assume we have a Unit-Payload consisting of an amount of cargo and the fuel to ship it to it's destination, and a drive unit of arbitrary mass to get it there. We know this is profitable, so we can ship another Payload for the same or slightly lower profit... or we can attach the second Payload to the first and ship them together. The deltaV doesn't change so the mass requirement is roughly the same, but we no longer have the cost of the second drive unit, so the shipment is actually more profitable.
As a general rule, large ships are more desirable because the ratio of profitable cargo to the rest of the ship drops the larger the ship gets. This is balanced by the ever decreasing profitability of the cargo, but plotted together on a graph we are given a curve of profitability to Payload, with the maximum profit occurring before the maximum is reached.
This means that any ship is going to have a generous budget of extraneous mass which they can carry and still be "worthwhile", proportional to the mass of the ship and the profitability of the cargo.

- 9. Metallic Hydrogen Engines.

Metallic Hydrogen engines are incredibly versatile, requiring no mass beyond their storage to be used and capable of extremely high thrust/weight values depending on how the tank is configured.
Simple versions are nothing more than a storage tank, which forms a simple magnetic nozzle when the hydrogen is released. More advanced systems may use separate storage tanks, passing grains of MH to the tank which serves as the engine.
W+ and higher ships will usually use more efficient plasma/fusion drives, but many will use MH for combined attitude control and point defence.
Unfortunately I haven't been able to find anything on RL metallic hydrogen storage, so this is all derived from what I “want” it to be capable of.
Using a Exhaust velocity of 16km/s, the ratio of Remass to Remass Storage cannot exceed 1/R, at the maximum possible deltaV the drive can produce, as deltaV above that amount converges to infinity.

In my head it's reasonable for a ship to be able to get from any planet in the solar system to any other. The mission table from Atomic Rockets gives a maximum value of 33159m/s to get from Mercury to Jupiter. 1/R for this value is ~0.126. In order to make the math simpler and give a buffer we can reduce this to 0.12, which gives a maximum deltaV of 33924m/s.

To be continued (when I get time) :D

In the past we've had to compensate for weaknesses, finding quick solutions that only benefit a few.
But what if we never need to feel weak or morally conflicted again?

Zoolimar Zoolimar's picture
Questions

1. Fusion Power and Molecular Construction.

What about dependence on ship origins and intended purpose?

Mars and Jupiter probably don't care that much about using rare materials or metals in construction.

Additionally there is a good reason real world militaries ascribe to a KISS principle. Magnetic bearings and similar designs are a good thing for a vessel not intended for combat but any ship that is supposed to be hit by laser and proton beams probably won't be that happy about them due to possible charges messing with generators.

7. Armor.

What about boron carbide/boron nitride as armour and protection against radiation?

It's also possible to use small fuel tanks with hydrogen as shielding and armour - before combat you will remove air from ship crew quarters to tanks so there will be no risk of reaction with oxygen. I think I also seen somewhere a solution with hydrogen being "dissolved" in fullerene. Not as mass effective as liquid but much more effective as armour. So you can combine part of the fuel tanks as a multi-purpose system.

Synths ans infomorphs don't care about oxygen so for them hydrogen as shielding will be even more effective.

Lazarus Lazarus's picture
ThatWhichNeverWas wrote:. . .

ThatWhichNeverWas wrote:
. . .
The energy Metallic Hydrogen provides is released when it is removed from containment – and that's it. There are no reaction chambers or extraneous features necessary because it's all implicit in the mass of the tank - you just have to “open the valve”.
This means that if you want to get more thrust you just need to push it out of containment quicker, increasing the Mass Flow, with the only limitation being the forces the tank can withstand.

No. Your ultimate limitation is the pressure at which metallic hydrogen will remain metallic. When you reach that pressure the metallic hydrogen will stop sublimating into gaseous hydrogen which in turn will stop the pressure from increasing. Beyond that the only way to increase the pressure would be to heat the gas and according to the 2D phase diagrams I'm looking at you would need to heat it to around 10,000 Kelvin before you begin to see an appreciable increase in pressure.

While that is certainly within the realm of possibility you are now looking at a hybrid system where you need to have a power plant generating a great amount of heat and you are no longer simply 'opening a valve'.

My artificially intelligent spaceship is psychic. Your argument it invalid.

Lazarus Lazarus's picture
Zoolimar wrote:. . .

Zoolimar wrote:
. . .
Mars and Jupiter probably don't care that much about using rare materials or metals in construction. . .

Why wouldn't they care? It is still a limiting factor and those materials are valuable (and in fact I'm not sure how Jupiter is in any significantly better position than a lot of outer planets since you can't mine Jupiter).

My artificially intelligent spaceship is psychic. Your argument it invalid.

Lazarus Lazarus's picture
ThatWhichNeverWas wrote:. .

ThatWhichNeverWas wrote:
. . .Metallic Hydrogen engines are incredibly versatile, requiring no mass beyond their storage to be used and capable of extremely high thrust/weight values depending on how the tank is configured.
Simple versions are nothing more than a storage tank, which forms a simple magnetic nozzle when the hydrogen is released. . .

No mass beyond their storage tank and their nozzle, and the weight of that storage tank is not insignificant. If it were to operate solely by maintaining pressure it would need to withstand something in the neighborhood of 15,000,000 psi which would probably require massive walls. In EP, however, we are told that people use magnetic fields to keep metallic hydrogen metastable. While this removes the massive walls you probably needed it does still require weight in the form of magnetic field generators as well as the power plant that generates the energy to generate the fields, and that is probably not insignificant.

Based off the 3 G figure estimated in EP as the capability of a metallic hydrogen engine I came up with an extremely rough approximation of a 45:1 power to weight ratio for your 'standard' setup. That means that with an 'average' size tank and an 'average' nozzle setup 1/15th of the mass of the ship is taken up with fuel, nozzles, the physical components of the storage tank (walls, magnetic field generators, etc.) and the portion of the power plant necessary to power the coils.

My artificially intelligent spaceship is psychic. Your argument it invalid.

Zoolimar Zoolimar's picture
Resources

Quote:
Why wouldn't they care? It is still a limiting factor and those materials are valuable (and in fact I'm not sure how Jupiter is in any significantly better position than a lot of outer planets since you can't mine Jupiter).

You can't mine Jupiter (bar hydrogen) but you can mine its moons and trojans. Except for heavy elements you can find almost anything there. So besides radioactives most other materials won't be that big of a problem.

The same goes for Mars with Belt and Saturn with moons. Though depending on what groups control asteroids/moons there may be a need for trade.

This elements are rare only in comparative sense. Solar system is enormous in size. If not for danger of exsurgents and TITANs all of transhumanity could have easily lived on Ganymede and still would have a room for growth.

ORCACommander ORCACommander's picture
iirc ine one the books there

iirc ine one the books there is a trade flow diagram

Also there are the bounties promised by the reliably unreliable pandora gates

Lazarus Lazarus's picture
Zoolimar wrote:. . .but you

Zoolimar wrote:
. . .but you can mine its moons and trojans. Except for heavy elements you can find almost anything there. So besides radioactives most other materials won't be that big of a problem. . .

Even the moons and trojans are largely icy bodies. The minerals that do exist tend to be silicates so they probably aren't the greatest of bodies to be mining.

While your statement about rarity being a comparative state is true that doesn't mean it isn't a problem. There could be a million tons of something but if you have to sift through a billion tons of raw material to get 1 kilogram it is still going to be extremely valuable. In the same vein while there might be copper and gold locked up in the rocky parts of Europa if you have to dig down to the core to get them that's going to be a problem.

My artificially intelligent spaceship is psychic. Your argument it invalid.

Zoolimar Zoolimar's picture
If I remember right up to

If I remember right up to Nickel it shouldn't be so hard to get. At least on Jupiter moons and in the Belt. Don't remember about Saturn.

Elements heavier than Nickel start to get progressively more rare and hard to mine unless they are in some asteroid. With Io probably being the main source of them which gives many opportunities for games (volcanoes everywhere).

Lazarus Lazarus's picture
Actually, 'rarity' is a weird

Actually, 'rarity' is a weird and funny thing. Some of the heavier elements are probably easier to get out of asteroids than to mine them on Earth (and that's not even figuring for the problems of the post apocalypse). The reason is because the asteroids have relatively no gravity and so there's nothing that really causes the heavier elements to migrate. In the case of bodies that have a noticeable amount of gravity heavier elements tend to settle towards the core during formation. Vulcanism can bring those up toward the surface if the density is reasonably close to the density of the mantle but in the case of very dense elements very little gets pushed to the surface.

That's why one of the tests is to look for things such as iridium when they want to ensure that a rock is a meteorite and not a terrestrial rock. Earth probably has a higher percentage of iridium than the rocks out in the belt but it is all buried down near the core.

My artificially intelligent spaceship is psychic. Your argument it invalid.

ThatWhichNeverWas ThatWhichNeverWas's picture
Insert title here.

Zoolimar wrote:
1. Fusion Power and Molecular Construction.

What about dependence on ship origins and intended purpose?

Mars and Jupiter probably don't care that much about using rare materials or metals in construction.

Ship origins and purpose don't apply at this level, and rarity only to a limited degree.
Yes, Military vessels are more likely to use technologies employing "rare" materials, but those materials will be as energy rich as possible to minimize the amount of the material used.

Zoolimar wrote:
Additionally there is a good reason real world militaries ascribe to a KISS principle. Magnetic bearings and similar designs are a good thing for a vessel not intended for combat but any ship that is supposed to be hit by laser and proton beams probably won't be that happy about them due to possible charges messing with generators.

Simple is relative. Physical bearings means you're dealing with wear and tear, lubricants, potential shrapnel, the possibility of misalignment, and so on. Magnetic bearings are for all intents and purposes solid state.
And if a ship is getting charges in the interior from weapons fire, they have much more important things to worry about.
Like the crew's flesh boiling.

Zoolimar wrote:
What about boron carbide/boron nitride as armour and protection against radiation?

It's also possible to use small fuel tanks with hydrogen as shielding and armour - before combat you will remove air from ship crew quarters to tanks so there will be no risk of reaction with oxygen. I think I also seen somewhere a solution with hydrogen being "dissolved" in fullerene. Not as mass effective as liquid but much more effective as armour. So you can combine part of the fuel tanks as a multi-purpose system.

Boron X-ide is fine against low energy particles, but doesn't do jack against high energy stuff. If you want to protect against high energy neutrons then you need a high atomic number material, and anything thick enough to block them is going to stop slow neutrons dead.

The problem with using your fuel tanks as shielding is that... well... you'll be using the fuel, so your protection decreases over time. Hydrogen tanks also leak and can be punctured, creating a ever-so-handy stream of gas to destabilise the ship and prevent repairs.
Using a hydrogen-rich solid prevents these issues, and PE is the most hydrogen-rich solid I could find. It's also really easy to work with.

Lazarus wrote:
No. Your ultimate limitation is the pressure at which metallic hydrogen will remain metallic. When you reach that pressure the metallic hydrogen will stop sublimating into gaseous hydrogen which in turn will stop the pressure from increasing.

Presumably the pressure required to contain Metastable Metallic Hydrogen is significantly less than that required to contain Metallic Hydrogen mehanically, because otherwise why bother.
From this it's safe to assume that the tank would rupture long before the hydrogen stops sublimating.

Lazarus wrote:
No mass beyond their storage tank and their nozzle, and the weight of that storage tank is not insignificant.
...
That means that with an 'average' size tank and an 'average' nozzle setup 1/15th of the mass of the ship is taken up with fuel, nozzles, the physical components of the storage tank (walls, magnetic field generators, etc.) and the portion of the power plant necessary to power the coils.

I'm not sure what you're getting at here.

-
I've been trying to get some figures together for fusion reactor mass, and failing utterly.
Think it would make sense simply to use Atomic Rockets values for Fusion/Plasma/AM drives?

In the past we've had to compensate for weaknesses, finding quick solutions that only benefit a few.
But what if we never need to feel weak or morally conflicted again?

Lazarus Lazarus's picture
ThatWhichNeverWas wrote

ThatWhichNeverWas wrote:
Lazarus wrote:
No. Your ultimate limitation is the pressure at which metallic hydrogen will remain metallic. When you reach that pressure the metallic hydrogen will stop sublimating into gaseous hydrogen which in turn will stop the pressure from increasing.

Presumably the pressure required to contain Metastable Metallic Hydrogen is significantly less than that required to contain Metallic Hydrogen mehanically, because otherwise why bother.
From this it's safe to assume that the tank would rupture long before the hydrogen stops sublimating.

Yes, it is presumably less than that (otherwise why even mess around with the magnetic fields to make it metastable) but the figure of an ISP of 1600 is very close to what you would get from the Atomic Rockets estimates which are not for metastable metallic hydrogen. This makes a lot of sense since you would want to get as much pressure as possible from the hydrogen currently providing thrust so you would no longer by stabilizing hydrogen as it passes through the nozzles.

So back to the initial point, you can't increase the pressure of the hydrogen gas indefinitely. At a certain point the pressure would interfere with sublimation. Thus there is a maximum effective pressure which means a maximum exhaust velocity and a maximum ISP of around 1600. That's why to get the higher ISPs you have to use plasma, fusion, and antimatter drives.

Quote:
Lazarus wrote:
No mass beyond their storage tank and their nozzle, and the weight of that storage tank is not insignificant.
...
That means that with an 'average' size tank and an 'average' nozzle setup 1/15th of the mass of the ship is taken up with fuel, nozzles, the physical components of the storage tank (walls, magnetic field generators, etc.) and the portion of the power plant necessary to power the coils.

I'm not sure what you're getting at here.


Mainly that the idea that the only weight is the mass of the hydrogen and the nozzles is not correct. These other components add up to a fairly significant amount to the point where on an 'average' metallic hydrogen propelled ship about 1/15th of the mass is taken up by the nozzles and all the ancillary equipment such as the physical tanks, the field generators, and the power plant to support them (1/15th because with a power to mass ratio estimate of 45:1 and 3 g's of acceleration you need to have 3/45ths or 1/15th of the ship mass used for nozzles and the ancillary equipment).

On a hydrogen-oxygen powered rocket with the same thrust you would only have 1/20th of the ship's mass used for the nozzle and the ancillary support (e.g. the tanks holding the fuel). If the nozzles for the two engines were the same mass then for a metallic hydrogen rocket 1.6% of the ship's mass would be being consumed by these ancillary components. Personally I think the nozzles for the metallic hydrogen engine probably weigh a little bit less than the nozzles for a hydrogen oxygen rocket so these extra components probably end up being more like 2-2.5%.

2.5% of the ship's mass may not seem like these components are taking up much weight but since the nozzle for a metallic hydrogen ship only take up around 3-3.5% of the ship (I'm just guestimatting .5-1% for the mass of the ship for the tank walls) those parts are pretty significant.

My artificially intelligent spaceship is psychic. Your argument it invalid.

MrWigggles MrWigggles's picture
For EP, I would assume there

For EP, I would assume there there no real such thing as rarity. There arent any natural materiel that are rare. EP isn't post scarcity, so even though there is de facto infinite of any element you want, you're limited by infrastructure to extract it, and process it. So... I guess there is rarity but not from quantity but of logistics.

Lazarus Lazarus's picture
MrWigggles wrote:For EP, I

MrWigggles wrote:
For EP, I would assume there there no real such thing as rarity. There arent any natural materiel that are rare. EP isn't post scarcity, so even though there is de facto infinite of any element you want, you're limited by infrastructure to extract it, and process it. So... I guess there is rarity but not from quantity but of logistics.

There are plenty of materials that are rare. Radioactives are probably the biggest one because they are only created in supernovae and they decay but there are other materials that are likewise only created in supernovae but in relatively small amounts.

Sure, in the universe there may be billions of tons of these materials but in EP people don't have access to the entire universe. What's more there can still be issues with obtaining the element that makes it rare. As an example, Aluminum is the third most common mineral in the Earth's crust yet until the very end of the 19th century it would have been a 'rare' material to work with because it was locked up in bauxite ore. In a similar vein if some element doesn't naturally clump up and as a result you have to process millions of tons of material just to obtain a couple of kilograms of material it can be considered 'rare'.

My artificially intelligent spaceship is psychic. Your argument it invalid.

ORCACommander ORCACommander's picture
actually with our current

actually with our current tech level ball bearings are more reliable and longer life than magnetic bearings

Zoolimar Zoolimar's picture
Insert another title here

ThatWhichNeverWas wrote:
And if a ship is getting charges in the interior from weapons fire, they have much more important things to worry about.
Like the crew's flesh boiling.

Bridge (or "bridge" in case of infomorphs) of the ship probably has additional internal shielding that can alleviate lesser hits. And any hit by a proton beam that goes through armour layer will bear a risk of charges with varying power levels.

ThatWhichNeverWas wrote:
The problem with using your fuel tanks as shielding is that... well... you'll be using the fuel, so your protection decreases over time. Hydrogen tanks also leak and can be punctured, creating a ever-so-handy stream of gas to destabilise the ship and prevent repairs.
Using a hydrogen-rich solid prevents these issues, and PE is the most hydrogen-rich solid I could find. It's also really easy to work with.

Than what about using same metallic hydrogen as storage for fusion fuel and shielding ?

About decrease in protection it is an interesting point. If we are not talking about passenger ships than crew area even in the case of biomorphs should not take more than 5% of the ship mass. So how much in percentage of ship mass consists of fuel tanks and what is their volume comparatively to crew occupied area?

You probably can designate shielding fuel tank as "emergency reserve" and use it only in most dire circumstances in cases then danger of getting irradiated will give way to much more immediate concerns. Or using it only on the last part of the journey for manoeuvring at your destination or last parts of deceleration burn.

ThatWhichNeverWas wrote:
I've been trying to get some figures together for fusion reactor mass, and failing utterly.
Think it would make sense simply to use Atomic Rockets values for Fusion/Plasma/AM drives?

Probably. Maybe cut about 5-7% of drive mass for high tech of the setting ?

Lazarus Lazarus's picture
Zoolimar wrote:. . .Than what

Zoolimar wrote:
. . .Than what about using same metallic hydrogen as storage for fusion fuel and shielding ?

Metallic hydrogen requires a magnetic field to keep it metastable. If the field were to turn off your fuel tanks would quite literally explode.

Metallic hydrogen is stored inside tanks, even though it is metallic. While the tanks probably aren't strong enough to keep the hydrogen compressed (the pressures necessary to keep metallic hydrogen metallic without the magnetic field McGuffin are massive) they are probably strong enough to prevent an explosion by venting excessive pressure outside the ship.

My artificially intelligent spaceship is psychic. Your argument it invalid.

Chernoborg Chernoborg's picture
Rough sketch

I put up a rough sketch of a bulk carrier design I've been working on. Would this http://eclipsephase.com/sites/default/files/bulkcarrier01_1_0.jpg be like what you're looking for? I'm working on putting labels and explanations on there, as well as probably moving the bridge module to its own page, but I've been itching to get it on here for a while now.

Current Status: Highly Distracted building Gatecrashing systems in Universe Sandbox!

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