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A Warship

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Tue, 2013-02-05 11:09

Jaberwo

A Warship

This is a Warship I designed for an adventure of my group. Flight Configuration: https://dl.dropbox.com/u/7142719/EP%20Warship/Flight%20Configuration.png Combat Configuration: https://dl.dropbox.com/u/7142719/EP%20Warship/Combat%20Configuration.png All files (with Interior): https://dl.dropbox.com/u/7142719/EP%20Warship/Eclipse%20Phase%20Warship.rar It is largely based upon a fusion-drive freighter which a friend of mine an me made up (picture of unfinished model: https://dl.dropbox.com/u/7142719/EP%20Warship/Shinseikatsu.png). The Freighter was based upon this NASA paper (http://de.scribd.com/doc/31526947/TM-2005-213559). Also I presume warfare in the style Arenamontanus describes in his (sadly unfinished) paper (http://www.eclipsephase.com/comment/18698#comment-18698). I might have gotten some things wrong though, more on my take on how it works later. Finally, the overall layout of the spacecraft was inspired by the ISV Venture Star from Avatar. SPACECRAFT DATA: General: Propulsion Type: Antimatter Propellant: Metallic Hydrogen Length: 767.5m Mass: Ship mass (dry): 3005 metric tons Nominal Payload: 10000 metric tons Propellant mass: 8800 metric tons Propellant Density: 0.6t/m³ Four spherical propellant Tanks, radius: 15m Overall mass (fully loaded and fueled): 21805 t Drive characteristics: Magnetic Nozzle Power: 949 GW Exhaust velocity / Specific Impulse: 1000km/s DeltaV: 500km/s +16km/s reserve Thrust: 1897kN Effective Thrust (due to angled engines): 1783kN Initial acceleration: 0,00826g Reactor, Power plant and Cooling: Overall Power: 1165 GW Required Electrical Power: 583MW Actual Electrical Power: 623MW Thermal Power: 1247MW Low temperature Radiators (13m x 39m): 8 High temperature Radiator: (13m x 39m): 32 I recently read the Space naval combat again and it seems to me that the following does not conflict with it too much. Also, several ideas I had are there as well so they might not be terribly wrong. If you think something about the ship or how it works is wrong or implausible, please write a comment. How it is supposed to work: The spacecraft travels as shown in the picture “Flight Configuration”. When it there is no way for one of the ships (or fleets) to avoid entering combat ranges it shuts off its main engines and retracts the radiators along the truss into their storage areas and starts to cool down by venting coolant. As soon as the asset containers are cold enough they are accelerated along the truss onto careful selected trajectories in order to form a cloud of platforms several thousand kilometers away from the spacecraft and towards the enemy. Then the truss also gets retracted into the front section and the folded armor seals the last gaps, the ship now looks like shown in “Combat Configuration”. Due to the low temperature and the special materials used in the containers their position may not be measured precise enough to guarantee a first time hit. Also a large percentage of them might be Decoys. So the first time someone opens fire or uses an active sensor to identify an asset all hell breaks loose as every object that does something can almost immediately be identified and destroyed with near certainty. Probably only one side has some weapons left after the clouds have met and they will try to get a firing solution for the enemy ship, but maybe it can defend itself and get away. Of course the ship may have been in range before one faction has been eliminated in the cloud. The surviving ships float out of combat range and maneuver to catch the reusable assets, probably plotting a course for a rearming and refueling station. Any repairs are only minor because almost every hit deals catastrophic damage and disables the ship or severely limits the possible course corrections. The armor mostly serves to keep kinetic projectiles above a certain size and therefore makes it possible to dodge or intercept them. It also protects against ‘scorching’ by lasers that put their energy into a big area to hit the ship more easily and fry the sensor systems. I have a half-finished game to represent EP space combat that started as a card game like the one Arenamontanus dreamed up (see the thread where his paper is). Now it’s more like small coin sized chips and needs something more usable than scraps of papers with “laser” written on it, but the few games we tried where quite fun and surprisingly tactical. Of course more balancing is needed and the game instructions are probably pretty hard to understand, especially considering that they are written in German. But at the moment I don’t have time for finishing it.

Tue, 2013-02-05 15:46

NewtonPulsifer NewtonPulsifer's picture

The thrust seems too low.

The thrust seems too low. The core book has antimatter ships at .2 gravities of acceleration. If we pick a point - say when propellant is 50%, as your .2 gravities accel point, then we'd have 17405 tonnes. 0.2 times 9.81 m/sec/sec is 1.962 meters/sec/sec. Multiply that by 17,405,000kg and we need 34,148,610 newtons - or 34,149 kilonewtons. More or less depending on when you decide the .2 gravities accel point is. EDIT: Nice layout pics! Its always cool to see the design of a ship that puts function/feasibility over form (cool 50's fins etc.)

—

"I fear all we have done is to awaken a sleeping giant and fill him with a terrible resolve."- Isoroku Yamamoto

Tue, 2013-02-05 16:04

OneTrikPony OneTrikPony's picture

I like the design except I

I like the design except I think it has a major flaw; It will probably carry a bunch of corporate pirates to a planet where they will be soundly beaten by a bunch of tall blue primitives weilding stone tools while riding six legged lizard horses and pterodactyls. :D Other than that It's good work. ;)

—

Mea Culpa: My mode of speech can make others feel uninvited to argue or participate. This is the EXACT opposite of what I intend when I post.

Wed, 2013-02-06 12:01

Jaberwo

NewtonPulsifer wrote:The

NewtonPulsifer wrote:
The thrust seems too low. The core book has antimatter ships at .2 gravities of acceleration. If we pick a point - say when propellant is 50%, as your .2 gravities accel point, then we'd have 17405 tonnes. 0.2 times 9.81 m/sec/sec is 1.962 meters/sec/sec. Multiply that by 17,405,000kg and we need 34,148,610 newtons - or 34,149 kilonewtons. More or less depending on when you decide the .2 gravities accel point is. EDIT: Nice layout pics! Its always cool to see the design of a ship that puts function/feasibility over form (cool 50's fins etc.)

I have to talk to the friend who helped me with the numbers again, I think under the assumptions in the NASA paper there had to be such a low thrust because anything higher would have made it impossible to cool the reactor. Until he got some more advanced calculations about the radiator temperature we had pretty massive radiators and coolant temperatures where dangerously close to melting tungsten.

OneTrikPony wrote:
I like the design except I think it has a major flaw; It will probably carry a bunch of corporate pirates to a planet where they will be soundly beaten by a bunch of tall blue primitives weilding stone tools while riding six legged lizard horses and pterodactyls. :D Other than that It's good work. ;)

Not on my watch! http://www.youtube.com/watch?v=kXraSkgssFk&t=1m33s

Wed, 2013-02-06 14:21

NewtonPulsifer NewtonPulsifer's picture

Jaberwo wrote:

Jaberwo wrote:
I have to talk to the friend who helped me with the numbers again, I think under the assumptions in the NASA paper there had to be such a low thrust because anything higher would have made it impossible to cool the reactor. Until he got some more advanced calculations about the radiator temperature we had pretty massive radiators and coolant temperatures where dangerously close to melting tungsten.

There's a NASA paper on antiproton heated hydrogen thrusters? Do you have a link to it?

—

"I fear all we have done is to awaken a sleeping giant and fill him with a terrible resolve."- Isoroku Yamamoto

Wed, 2013-02-06 18:17

Jaberwo

I meant the one I linked to

I meant the one I linked to in the first post, it describes a fusion drive though. When I created this ship I mostly increased the numbers from the fusion freighter we had created before by a factor. I just assumed that AM works just as good as fusion and this kind of extrapolation was okay anyway even if I wouldn't have changed the energy source. I also hoped that anything that couldn't be scaled so easily (it was a factor of 2. something) would be outweighed by the more powerful AM drive. The ship in the paper has a maximum acceleration of 1.9 milli g despite having a 7.9GW reactor and a mass of 1690mt. About 14% of its power has to be radiated. The maximum coolant temperature in our freighter and the warship was about twice as high as with the NASA design. (The problem for me right now is that I don't have the notes and calculations and the adventure the warship was for isn't finished yet, so I can't show my friend this design because he is one of the players)

Wed, 2013-02-06 21:26

NewtonPulsifer NewtonPulsifer's picture

Ah okay.

Ah okay. Here's a non scribd.com link to the paper http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20050160960_2005161... With this design they were trying to replicate the [i]Discovery[/i] from [i]2001: A Space Odyssey[/i] If you've seen the movie they had something like an 18 month trip to Jupiter. To get to Eclipse Phase fusion rockets you're going to need to turn this dial up to 11. Thinks like fusion reactors that are better than tokamaks. Field Reversed Configurations like from Tri-Alpha Energy: http://www.int.washington.edu/talks/WorkShops/int_12_3/People/Weller_H/W... http://nextbigfuture.com/2012/10/tri-alpha-energy-nuclear-fusion-100mw.html Dense Plasma Focus with Magnetic Pinch: http://www.lawrencevilleplasmaphysics.com/ Stuff like that. In addition, you can make x-ray mirrors. You don't need to let the synchrotron and bremsstrahlung impinge on the ship and heat it up. Also, He3/He3 fusion has zero neutrons, so no heat loading there. Discussed here: http://eclipsephase.com/fusion-power-soon Take another look at the diagram on page 17 of the NASA paper. Things are looking MUCH better from a power to heat load perspective, aren't they?

—

"I fear all we have done is to awaken a sleeping giant and fill him with a terrible resolve."- Isoroku Yamamoto

Wed, 2013-02-06 23:09

NewtonPulsifer NewtonPulsifer's picture

Just a warning, they have bad

Just a warning, they have bad math in that NASA paper (EDIT: my bad, its fine). Check out Table 2 on Page 7. They have 6,250 foot-pounds of thrust (red flag here - they're mixing their metric and imperial. That's crap). Okay, so that is 8474 newton-meters. Then they have 1,690 metric tonnes and 1.68 milli-gees of thrust. Except that number is 27,853 newtons. EDIT: My mistake. Messed up my units. 1 foot-pound [i]thrust[/i] equals 4.45 Newtons, so we're good. I hate working with imperial! :) Doh!

—

"I fear all we have done is to awaken a sleeping giant and fill him with a terrible resolve."- Isoroku Yamamoto

Sat, 2013-02-09 21:56

Decimator

If you mount some droplet

If you mount some [url=http://www.projectrho.com/public_html/rocket/basicdesign.php#id--Heat_Ra... radiators[/url] on the engine section, you can leave them extended. An impact against a sheet of droplets isn't going to do anything, and spar impacts would be unlikely. You'll need to carry extra coolant along, but that'd be worlds better than venting coolant to cool off.

Sun, 2013-02-10 02:10

#10

NewtonPulsifer NewtonPulsifer's picture

Liquid tungsten droplets

Liquid tungsten droplets would have a very nice combination of high temperature and low vapor pressure. Hmm.

—

"I fear all we have done is to awaken a sleeping giant and fill him with a terrible resolve."- Isoroku Yamamoto

Sun, 2013-02-10 10:08

#11

Jaberwo

I considered them, but there

I considered them, but there are several problems: As far as I know they are less efficient in terms of cooling per mass. The loss of coolant over the months of transit may still be less than the coolant loss of the open-cycle system (which might act as a heat sink for some time if combat is short) but it might not be that much of a difference, because the losses increase a lot when the ship takes evasive maneuvers. They can't be armored against scorching and "birdshot" kinetic projectiles, at least it would add a lot of mass and the overall maneuverability of the ship in combat would decrease (not sure if it can dodge a significant amount of fire anyway though.) With the folded radiators the armor is closer to the center of mass. Although the ship is almost completely unable to sustain any real hit extended radiators would make it even more vulnerable, but probably not too much. As you said it is improbable for a spar to be hit, but minor damage to the truss would knock out the entire cooling system, leving the ship dead in the water. And in the end you can't cool a ship to low two digit Temperatures (Kelvin) in a short time with normal radiators because the coolant freezes. They also take a long time to get up and running again. The idea is that the ship cools down until it is really difficult to see. Of course the enemy knows where it is from the warm Hydrogen around it and the last known position and course correction, but the accelerated cold assets add to its positional uncertainty which hopefuly makes a difference considering that the ship is farther away from the enemy guns than its "ammunition" (the assets). When the time comes and the ship has to act it has to act quickly. Within milli or microseconds gigantic lasers may have to fire, metallic hydrogen thrusters need to thrust the ship out of the way etc. This heat cannot be carried away fast enough with a ship that is virtually frozen, it needs to be dumped. EDIT: It might be economically viable to have some auxiliary radiator that gets used when the hydrogen has hit the fan and the ship has gone into active mode after a situation where it needed to act. That way the amount of coolant that has to be vented can be reduced. But I could imagine that the ship ist pretty much done with when that happens anyway, so the extra hydrogen might not be worth the effort. I might add that the amount of hydrogen that has to be vented is not that high. I think about 3kg per second for full power.

Sun, 2013-02-10 13:47

#12

Decimator

Jaberwo wrote:I considered

Jaberwo wrote:
I considered them, but there are several problems: As far as I know they are less efficient in terms of cooling per mass.

A droplet radiator has more surface area than a normal radiator, so this is probably not the case. I'll attempt to do the math later for a hard answer.

Jaberwo wrote:
The loss of coolant over the months of transit may still be less than the coolant loss of the open-cycle system (which might act as a heat sink for some time if combat is short) but it might not be that much of a difference, because the losses increase a lot when the ship takes evasive maneuvers.

They could always shut the system off while evading, then turn it back on as soon as they aren't.

Jaberwo wrote:
They can't be armored against scorching and "birdshot" kinetic projectiles, at least it would add a lot of mass and the overall maneuverability of the ship in combat would decrease (not sure if it can dodge a significant amount of fire anyway though.) With the folded radiators the armor is closer to the center of mass. Although the ship is almost completely unable to sustain any real hit extended radiators would make it even more vulnerable, but probably not too much. As you said it is improbable for a spar to be hit, but minor damage to the truss would knock out the entire cooling system, leving the ship dead in the water.

This is true. While the spars won't mass a whole lot, they won't be negligible. And yes, the risk of spar damage is nonzero.

Jaberwo wrote:
And in the end you can't cool a ship to low two digit Temperatures (Kelvin) in a short time with normal radiators because the coolant freezes. They also take a long time to get up and running again. The idea is that the ship cools down until it is really difficult to see. Of course the enemy knows where it is from the warm Hydrogen around it and the last known position and course correction, but the accelerated cold assets add to its positional uncertainty which hopefuly makes a difference considering that the ship is farther away from the enemy guns than its "ammunition" (the assets). When the time comes and the ship has to act it has to act quickly. Within milli or microseconds gigantic lasers may have to fire, metallic hydrogen thrusters need to thrust the ship out of the way etc. This heat cannot be carried away fast enough with a ship that is virtually frozen, it needs to be dumped.

Can the existing radiators get the ship that cold in edge-on sunshine? It'll still have waste heat from the computers and systems to reject as well.(which may or may not be negligible, just something to think about) I'm assuming the ship will be crewed by infomorphs so it doesn't need a life support system. Note also that all the polities of Eclipse Phase will have thousands of satellites watching for anything thrusting in their general direction, and once a telescope is locked onto your craft, you won't be able to shake its notice.(unless you don't look like a warship, and maybe not even then, as even the lowliest shuttle is still a kinetic kill vehicle.) Getting the ship as cold as possible is still a good plan though, as that allows the ship to sink more heat.

Jaberwo wrote:
EDIT: It might be economically viable to have some auxiliary radiator that gets used when the hydrogen has hit the fan and the ship has gone into active mode after a situation where it needed to act. That way the amount of coolant that has to be vented can be reduced. But I could imagine that the ship ist pretty much done with when that happens anyway, so the extra hydrogen might not be worth the effort. I might add that the amount of hydrogen that has to be vented is not that high. I think about 3kg per second for full power.

Are you using metallic hydrogen as your sacrificial coolant? Please understand that I'm not trying to tear your creation apart. I simply find engineering challenges compelling.

Sun, 2013-02-10 18:27

#13

NewtonPulsifer NewtonPulsifer's picture

Droplet is way better. I'll

Droplet is way better. I'll post the links when I'm at my laptop. I just checked and tungsten is ferromagnetic. Instead of droplets, use a cloud of tungsten nano particles. This allows you to contain them with electrostatic fields when maneuvering. The particles cannot be molten, however, as they'll lose their ferromagnetism. .....okay got my laptop. From this nasa paper we have 100 square meters per metric tonne, each which rejects 357 kilowatts per square meter (this is a 1350 Kelvin loop). The droplet radiator calculator gets us 13,000 kilowatts per square meter at 1350 Kelvin (this was a link through the projectrho.com link Decimator put up). Unfortunately I can't find the Curie temperature for tungsten through google, so I'll have to go with the highest I could find (cobalt). It has a Curie temperature of 1400 Kelvin, so I'm going to assume tungsten dust can handle 1350 Kelvin too. Re-using the droplet calculator for cobalt 1mm balls and going with a temperature just below the Curie point, we get the same 13 megawatts per square meter, but it is now combat capable because there is no vapor lossage (its not a liquid) and it is maneuver capable due to electrostatic/magnetic confinement. Edit: EP tech actually has super powerful magnets, so paramagnetic things are probably still containable. This would be great for using molten tungsten, which could be very very high temperature, and the vapor could be potentially recaptured via powerful magnets. Radiator effectiveness goes up at the fourth power of the heat of the radiator, so being able to create super high temperature radiators would be a big breakthrough.

—

"I fear all we have done is to awaken a sleeping giant and fill him with a terrible resolve."- Isoroku Yamamoto

Sun, 2013-02-10 19:46

#14

Jaberwo

Decimator wrote:Please

Decimator wrote:
Please understand that I'm not trying to tear your creation apart. I simply find engineering challenges compelling.

Tearing it apart was just what I hoped would happen in this thread! :) I am grateful for every comment that points out some flaw or gives a possible alternative and I know that it can't be right in every little detail, probably not even at every important point. Let's just see how long it can stand under scrutiny. Even if it can't be salvaged to be completely "right" and perfect hard sci fi, I will know how hard it is. Most ships in the official adventures don't even have radiators, but it's still fun to play them.

Decimator wrote:
A droplet radiator has more surface area than a normal radiator, so this is probably not the case. I'll attempt to do the math later for a hard answer.

NewtonPulsifer wrote:
Droplet is way better. I'll post the links when I'm at my laptop. The droplet radiator calculator gets us 13,000 kilowatts per square meter at 1350 Kelvin (this was a link through the projectrho.com link Decimator put up).

I have seen this calculator but I think it is wrong. (Always a risky thing to say about something from projectrho.com I know ;) ) If you check the text with the calculations under the link, you can see that he does not account for the droplets radiating onto each other. As I understand it, only the photons radiated into space carry energy away from the ship. So its no use to just increase the surface area. There is also a text under a picture of radiators a little further up that says that the minimum angle between radators is 90 degrees, because they would otherwise radiate onto each other. But they do that at 90° (at least I'm pretty sure they do) so I think projectrho is not completely right concerning radiators. It seems to me that droplet radiators are like solid ones with holes in them. Their advantages lie elsewhere. So from my point of view they are only used when these advantages outweigh their lower performance. On the other hand it might be possible that because you can make the droplet sheats so thin, there is less mass involved, just greater radiator length and width. If this is true, both possibilities might be usable, I can't say. It probably depends on several factors. But this still doesn't change the other problem: The "reaction time" of any radiator is too long. The coolant can't transport the heat to the radiators fast enough because it is frozen. So the only way to get the heat out fast is to use something that is still liquid or a gas.

Decimator wrote:
They could always shut the system off while evading, then turn it back on as soon as they aren't.

I think the cooling system of the ship does not allow for any interruptions, because the temperature would get critical way too fast. But that might be easily overcome by a heatsink or open cycle system that only takes over when heat spikes appear. Maybe the coolant could also be vented in recatchable containers with demolition charges, so you don't leave a prize for the enemy ship if you loose.

Decimator wrote:
Are you using metallic hydrogen as your sacrificial coolant?

Nope, too energetic. It is difficult to cool something with a substance that explodes when it is released from its containment. ;) I was thinking some super cold hydrogen (or something better, if available) and a lot of slush hydrogen. The first for getting the residual heat out of the ship when everything else is already at low temperature and nothing else can cool the ship down any further without producing more heat elsewhere (might be impossible because the heat transfer goes down with temperature and therefore the mass needed for temperatures close to background radiation could be too high) The latter because it has the lowest density at acceptable preassure. It would be used for the regular open cycle cooling.

Decimator wrote:
Can the existing radiators get the ship that cold in edge-on sunshine? It'll still have waste heat from the computers and systems to reject as well.(which may or may not be negligible, just something to think about) I'm assuming the ship will be crewed by infomorphs so it doesn't need a life support system. Note also that all the polities of Eclipse Phase will have thousands of satellites watching for anything thrusting in their general direction, and once a telescope is locked onto your craft, you won't be able to shake its notice.(unless you don't look like a warship, and maybe not even then, as even the lowliest shuttle is still a kinetic kill vehicle.) Getting the ship as cold as possible is still a good plan though, as that allows the ship to sink more heat.

I have to admit that I never considered the Sun. I only envisioned combat in the outer system, so I don't know how much this would change. I assumed that the waste heat in "super cold mode" can be contained long enough so it does not show on the outside during normal combat. So yes, I think it is negligible enough for the scope of my thinking. The crew are all sleeved into infomorphs/simulmorphs, but even they take a back seat in combat which is handled by a super intelligent AGI that might be dangerously close to the kind of systems that lead to the fall. Like I said the cooling is not for stealth as in "they don't know we are coming" but rather for lowering the chance of a first time hit from great distance. This ship will always be watched, from the time construction starts until its end in battle, an accident or a shipyard. The idea is just to make the targeting solution more imprecise and the assets unidentifiable.

NewtonPulsifer wrote:
Edit: EP tech actually has super powerful magnets, so paramagnetic things are probably still containable. This would be great for using molten tungsten, which could be very very high temperature, and the vapor could be potentially recaptured via powerful magnets. Radiator effectiveness goes up at the fourth power of the heat of the radiator, so being able to create super high temperature radiators would be a big breakthrough.

Mon, 2013-02-11 14:44

#15

NewtonPulsifer NewtonPulsifer's picture

Jaberwo wrote:Decimator wrote

Jaberwo wrote:

Decimator wrote:
A droplet radiator has more surface area than a normal radiator, so this is probably not the case. I'll attempt to do the math later for a hard answer.

NewtonPulsifer wrote:
Droplet is way better. I'll post the links when I'm at my laptop. The droplet radiator calculator gets us 13,000 kilowatts per square meter at 1350 Kelvin (this was a link through the projectrho.com link Decimator put up).
I have seen this calculator but I think it is wrong. (Always a risky thing to say about something from projectrho.com I know ;) ) If you check the text with the calculations under the link, you can see that he does not account for the droplets radiating onto each other. As I understand it, only the photons radiated into space carry energy away from the ship. So its no use to just increase the surface area.

You can do a rough back of the envelope analysis. Treat each 1mm drop as a cube for simplicity. They're emitting from each face. They're 2mm apart. At 1 mm apart, they're at 1 unit of infrared photons intensity. 2mm is 2 units, so 1/4 of a unit of infrared photons. So you're emitting 6 units of photons, and eating 8/4 (2) units of photons from your 8 neighbors. So a net of 4 units. This is a naiive analysis of course, because the droplet calculator uses an emissivity rating of 0.07, not 1 of a perfect black body. So a bunch of those photons fired at the droplet neighbors simply reflect. If you were to use a "bead" radiator rather than the droplets, you could actually coat them with a one-way mirror (reflects infrared from the outside but not inside) and not take any of this hit. So worst case (perfect black body), you lose 1/3 of your capacity;real-word case (emissivity 0.07), negligible impact.

Jaberwo wrote:
There is also a text under a picture of radiators a little further up that says that the minimum angle between radators is 90 degrees, because they would otherwise radiate onto each other. But they do that at 90° (at least I'm pretty sure they do) so I think projectrho is not completely right concerning radiators. It seems to me that droplet radiators are like solid ones with holes in them. Their advantages lie elsewhere. So from my point of view they are only used when these advantages outweigh their lower performance.

You can see some NASA papers on droplet radiators here and here.

Jaberwo wrote:
On the other hand it might be possible that because you can make the droplet sheats so thin, there is less mass involved, just greater radiator length and width. If this is true, both possibilities might be usable, I can't say. It probably depends on several factors.

To be honest the droplet radiator system calculator is a rather naive analysis - it assumes any number of pain-in-the-ass engineering possibilities that could make it infeasible don't crop up in that calc in the slightest.

Jaberwo wrote:
But this still doesn't change the other problem: The "reaction time" of any radiator is too long. The coolant can't transport the heat to the radiators fast enough because it is frozen. So the only way to get the heat out fast is to use something that is still liquid or a gas

That's a great point. If you have molten metal as your coolant, and you let it solidify, you'll need to re-melt it (probably through heaters). That potentially adds mass, risk, and complexity. That being said you don't *have* to use a coolant loop per se. You can use a substance that has a very high thermal transfer rate as a solid heat exchanger. Check out isotopically pure diamond: https://en.wikipedia.org/wiki/List_of_thermal_conductivities

NewtonPulsifer wrote:
Edit: EP tech actually has super powerful magnets, so paramagnetic things are probably still containable. This would be great for using molten tungsten, which could be very very high temperature, and the vapor could be potentially recaptured via powerful magnets. Radiator effectiveness goes up at the fourth power of the heat of the radiator, so being able to create super high temperature radiators would be a big breakthrough.

This sounds very interesting, but it might not be possible to raise the temperature any higher than my coolant temperature because it can't get any hotter than the highest acceptable temperature for the materials the reactor is made from, lower even as you need a temperature difference to transport heat. Is there a possibility to catch the waste heat at high temperatures before it's in the first wall of the reactor? All in all I am unsure whether the effort to cool down the ship so much is worth it, if it is possible at all. Less so with the assets. Does it really lower the chances of getting hit significantly?[/quote] I'll admit I can't fathom how an anti-proton annihilation based reactor is going to work. From my point of view it simply would not work. It's going to be useful for thrust (completely open-loop) only. There's no viable way to make electricity from it as compared to an aneutronic fusion reactor. Yes, you can use the brayton cycle but the power/weight would be pitiful. That being said, if this ship also has a fusion reactor for electricity in addition to the antimatter propulsion system perhaps the first wall lining of the fusion reactor could be a tungsten vapor boundary layer, then molten tungsten, then a diamondoid wall layer, then the room-temperature superconductor super-magnets. You'd need a pretty interesting pumping system for the tungsten vapor. Paramagnetically controlled, I guess. I'm not sure how feasible that is. I guess I'd have to crunch the magnetic moment of tungsten vs. say a 100 Tesla magnet system to find out if is feasible. [EDIT: 100 Teslas gets you roughly 40 Gigapascals of magnetic pressure. This is enough to keep metal vapor in its critical point state. So and MHD system with tungsten vapor is definitely do-able. Temperature would be 13892 K! That would cool down ridiculously fast unless you put 99.999% reflective mirrors inside the tungsten vapor channels.] Anyway, we'd probably need 3 cooling loops. Very high, high-med (to preserve structures), low (room temperature superconductors).

—

"I fear all we have done is to awaken a sleeping giant and fill him with a terrible resolve."- Isoroku Yamamoto

Mon, 2013-02-11 19:29

#16

Jaberwo

NewtonPulsifer wrote:You can

NewtonPulsifer wrote:
You can do a rough back of the envelope analysis. Treat each 1mm drop as a cube for simplicity. They're emitting from each face. They're 2mm apart. At 1 mm apart, they're at 1 unit of infrared photons intensity. 2mm is 2 units, so 1/4 of a unit of infrared photons. So you're emitting 6 units of photons, and eating 8/4 (2) units of photons from your 8 neighbors. So a net of 4 units. This is a naiive analysis of course, because the droplet calculator uses an emissivity rating of 0.07, not 1 of a perfect black body. So a bunch of those photons fired at the droplet neighbors simply reflect. If you were to use a "bead" radiator rather than the droplets, you could actually coat them with a one-way mirror (reflects infrared from the outside but not inside) and not take any of this hit. So worst case (perfect black body), you lose 1/3 of your capacity;real-word case (emissivity 0.07), negligible impact.

I'm afraid I can't follow your calculation. Maybe you know of some geometric analysis of the problem in a paper? Or could you expand this calculation a little bit? I am going to read the two papers you linked in more detail later, perhaps that makes it more clear. Also I am pretty sure that there is no such thing as an one-way mirror: Second question: http://what-if.xkcd.com/14/ But perhaps I misunderstood what you meant. It is true that some photons would be reflected with 0.07, and go into space anyway. But overall there would be less photons because of the lower emissivity. I don't think reflecting radiators are a good idea. But it might be more complicated than that. (While we're on mirrors: I checked the x-ray mirror you mentioned earlier. The 99% reflectivity are only bragg-reflectivity, there are still a lot of other possible interactions of x-rays with matter, like compton scattering and absorption. Still the heat load is lower compared to the Discovery II)

NewtonPulsifer wrote:
You can see some NASA papers on droplet radiators To be honest the droplet radiator system calculator is a rather naive analysis - it assumes any number of pain-in-the-ass engineering possibilities that could make it infeasible don't crop up in that calc in the slightest.

While I am not entirely convinced, it seems that LDR require indeed less mass per watt than traditional ones and it might be a good idea to switch to LDRs. But I have difficulties to see why they should radiate more heat per m² than traditional ones and I can't get any useful numbers because my radiators operate at so much higher tempertures. Also, considering the small amount of mass the carbon radiators take up anyway, I wonder if there are some other reasons for traditional radiators or against LDRs. Maintenance and failiure rates perhaps? Real LDRs operate at much lower temperatures, maybe they run into problems with +2500K? Are they still the lighter alternative with these temperatures? The two papers are both below 1000K. What new possibilities arise for solid radiators in 10 AF? You certainly read more than me about these topics, but it seems to me that droplet radiators are not widely used in modern designs although the 1986 paper seems so promising. Is there some kind of catch? If not I might look into changing the design.

NewtonPulsifer wrote:
That's a great point. If you have molten metal as your coolant, and you let it solidify, you'll need to re-melt it (probably through heaters). That potentially adds mass, risk, and complexity. That being said you don't *have* to use a coolant loop per se. You can use a substance that has a very high thermal transfer rate as a solid heat exchanger. Check out isotopically pure diamond: https://en.wikipedia.org/wiki/List_of_thermal_conductivities

Pretty impressive! But if I didn't make a mistake in my calculations the heat transfer over 100m is orders of mgnitude too low with 4m² heatpipe. Still useful over short distances perhaps.

NewtonPulsifer wrote:
I'll admit I can't fathom how an anti-proton annihilation based reactor is going to work. From my point of view it simply would not work. It's going to be useful for thrust (completely open-loop) only. There's no viable way to make electricity from it as compared to an aneutronic fusion reactor. Yes, you can use the brayton cycle but the power/weight would be pitiful.

The specifics of the reactor are not too important, I think, because I have been extrapolating from traditional fusion anyway. Having AM, He3 and all the other sci fi methods at our fingertips, I'm confident that we can simplify matters. If it helps we could let the exact type of reactor be undetermined or maybe change it to AM 'catalyzed' fusion etc. the fact is that there is enough energy for lasers and stuff and thrust is more or less arbitrary (within limits), depending on personal taste. 0.2G might be easy, 1700kN might be just barely possible but it doesn't change much.

NewtonPulsifer wrote:
That being said, if this ship also has a fusion reactor for electricity in addition to the antimatter propulsion system perhaps the first wall lining of the fusion reactor could be a tungsten vapor boundary layer, then molten tungsten, then a diamondoid wall layer, then the room-temperature superconductor super-magnets. You'd need a pretty interesting pumping system for the tungsten vapor. Paramagnetically controlled, I guess. I'm not sure how feasible that is. I guess I'd have to crunch the magnetic moment of tungsten vs. say a 100 Tesla magnet system to find out if is feasible. [EDIT: 100 Teslas gets you roughly 40 Gigapascals of magnetic pressure. This is enough to keep metal vapor in its critical point state. So and MHD system with tungsten vapor is definitely do-able. Temperature would be 13892 K! That would cool down ridiculously fast unless you put 99.999% reflective mirrors inside the tungsten vapor channels.] Anyway, we'd probably need 3 cooling loops. Very high, high-med (to preserve structures), low (room temperature superconductors).

Is the inner vapor layer only interesting for the auxilliary fusion reactor or for any reactor? Radiating at +10000K would be fantastic and change everything. But I have the feeling that this system is a pretty difficult thing to do, if it works at all. Perhaps it's on the horizon 10 AF, but it could also be sci fi even for Transhumanity, As there is no real world example I'd say you either discover that it is impossible because of something basic if you go further or we can't say and it's up to taste.

Mon, 2013-02-11 23:55

#17

NewtonPulsifer NewtonPulsifer's picture

Jaberwo wrote:

Jaberwo wrote:
I'm afraid I can't follow your calculation. Maybe you know of some geometric analysis of the problem in a paper? Or could you expand this calculation a little bit? I am going to read the two papers you linked in more detail later, perhaps that makes it more clear.

Looks like we don't need to. The droplet radiator equation was already at the projectrho.com page. (0.5 * b * h)/(4r2 + 4r*q + q2) * 4*π*r2 =q covers the distance between drops.

Jaberwo wrote:
Also I am pretty sure that there is no such thing as an one-way mirror:

Very true, but the existence in EP of an invisibility cloak implies it would be not only possible but already old tech. Feasible? Maybe not - the metamaterials might break down under than kind of heat (or high temperature ones might not work as well but an 80/20 split would still be nice).

Jaberwo wrote:
Second question: http://what-if.xkcd.com/14/ But perhaps I misunderstood what you meant.

Back at you. You'll have to spell that one out for me, I'm not following you either with that link :)

Jaberwo wrote:
It is true that some photons would be reflected with 0.07, and go into space anyway. But overall there would be less photons because of the lower emissivity. I don't think reflecting radiators are a good idea. But it might be more complicated than that. (While we're on mirrors: I checked the x-ray mirror you mentioned earlier. The 99% reflectivity are only bragg-reflectivity, there are still a lot of other possible interactions of x-rays with matter, like compton scattering and absorption. Still the heat load is lower compared to the Discovery II)

Umm. Don't know how to put it. Good info here: http://www.xtal.iqfr.csic.es/Cristalografia/parte_05-en.html Basically, if the x-ray Bragg reflected, it *cannot* do any of the other interactions. [img]http://www.xtal.iqfr.csic.es/Cristalografia/archivos_05/bragg2.gif[/img] As you can see in the above image, if a photon is Bragg reflected (also called Brag diffraction), it can't also Compton scatter. So a Bragg reflectivity of 99% necessarily means only 1% of the photons could interact in some other manner. Keep in mind the diamond x-ray mirror only works on certain planes of the diamond, but that's not a deal breaker for its usefulness. [EDIT= I should mention you can dramatically reduce the amount of x-rays in a fusion reactor by running it in "hot ion" mode where you keep the electrons cooler than the ions. This trick had slipped my mind.]

Jaberwo wrote:
While I am not entirely convinced, it seems that LDR require indeed less mass per watt than traditional ones and it might be a good idea to switch to LDRs. But I have difficulties to see why they should radiate more heat per m² than traditional ones and I can't get any useful numbers because my radiators operate at so much higher tempertures.

It is higher surface area is all. Some kind of hi-tech radiator foam/lattice/mesh coated in one-way mirrors that focuses and shoots the infrared photons out the rear of the ship (or potentially redirect to front for a nice search light or infrared laser) might be the way to go. No need to have exposed radiators. Might be too Star Trek for you, though, but does improve the low-signature potential. Here's another Star Trek-ish one - what about neutrino cooling? EP tech has some way of creating and trapping neutrinos for communications. Might it be used as a way to radiate waste heat away as neutrinos?

Jaberwo wrote:
Also, considering the small amount of mass the carbon radiators take up anyway, I wonder if there are some other reasons for traditional radiators or against LDRs. Maintenance and failiure rates perhaps? Real LDRs operate at much lower temperatures, maybe they run into problems with +2500K? Are they still the lighter alternative with these temperatures? The two papers are both below 1000K. What new possibilities arise for solid radiators in 10 AF?

You certainly read more than me about these topics, but it seems to me that droplet radiators are not widely used in modern designs although the 1986 paper seems so promising. Is there some kind of catch? If not I might look into changing the design.[/quote] No one's ever stuck a full-on nuclear reactor in space yet (frankly no one could boost the mass!) - so there's simply never been a need for a droplet radiator. It's a solution in search of a problem right now. The other problem is failure mode. A fission reactor just cannot be turned off immediately. If your droplet radiator had a malfunction it'd likely stop working 100% and you'd likely cook the whole spacecraft (very unlikely to have this failure with an old school radiator) - so you're likely to have regular radiators as backup, reducing its advantage. This isn't as much of a problem with a fusion reactor (many versions shut down in less than a milisecond).....but viable space-borne fusion reactors are of coure still sci-fi. So we're not likely to see a real droplet radiator attempted until we see a high power fission reactor in space.

NewtonPulsifer wrote:
That's a great point. If you have molten metal as your coolant, and you let it solidify, you'll need to re-melt it (probably through heaters). That potentially adds mass, risk, and complexity. That being said you don't *have* to use a coolant loop per se. You can use a substance that has a very high thermal transfer rate as a solid heat exchanger. Check out isotopically pure diamond: https://en.wikipedia.org/wiki/List_of_thermal_conductivities

Pretty impressive! But if I didn't make a mistake in my calculations the heat transfer over 100m is orders of mgnitude too low with 4m² heatpipe. Still useful over short distances perhaps.[/quote] A 2000 Kelvin difference on hot and cold end of a 4m² isotopically mostly pure diamond (at the 200,000 number) heatpipe 100m long results in a [b]10 gigawatt[/b] transfer. Depending on your assumptions that may or may not be enough. Increase the Kelvin difference and you get a linear improvement. That's 1400 metric tonnes of diamond, though. As a potential heat sink it is 0.63 joules per gram per degree - about 1/7th of water. That's only 882 megajoules for a 2000 degree change (so you have like .1 seconds to shut things down before you start getting into the yellow/red zone).

Jaberwo wrote:

NewtonPulsifer wrote:
...100 Teslas gets you roughly 40 Gigapascals of magnetic pressure. This is enough to keep metal vapor in its critical point state. So and MHD system with tungsten vapor is definitely do-able. Temperature would be 13892 K! That would cool down ridiculously fast unless you put 99.999% reflective mirrors inside the tungsten vapor channels...
Is the inner vapor layer only interesting for the auxilliary fusion reactor or for any reactor? Radiating at +10000K would be fantastic and change everything. But I have the feeling that this system is a pretty difficult thing to do, if it works at all. Perhaps it's on the horizon 10 AF, but it could also be sci fi even for Transhumanity, As there is no real world example I'd say you either discover that it is impossible because of something basic if you go further or we can't say and it's up to taste.

Off the top of my head it would only work in a fusion reactor. Mostly because it is easier to keep the hot electrons, protons, and alpha particles in the center of the reactor and the tungsten on the edge because of the big electric charge/mass ratio difference. In addition the simple mass difference is enough to take advantage of if you spin the reactor like a centrifuge (dense tungsten goes to the outside walls). A nanoparticle fission reactor would have even more massive uranium/plutonium particles that would want to be at the edge rather than the tungsten, and also another big negative, the neutrons from the fission reactor would react with the isotopically pure diamonds (making them partly C13 instead of pure C12) degrading your potential of using it as a high temperature structure and heat pipe at the same time. In addition the fission fragments are large and energetic, so harder to contain with magnets (leading to a very big heat loading on the structure). There's a dozen different ways to attain fusion. To get one that puts more power out than is put in (and is light enough for military aerospace and has the required power density) is the trick, right? The big problem of using a magnetic trap to contain tungsten vapor (or even plasma - a bottled plasma arc) is you're probably containing it with [i]room temperature superconductor based magnets[/i]. This doesn't nix the possibility, but its a big engineering complication. You need an awesomely well done reflective surface to protect those magnets from radiated photons. MIT has done 99.999% already though (1 to 100,000) but just don't scratch that reflective coating off or get it too dirty! That'll pop your breakers right quick.

—

"I fear all we have done is to awaken a sleeping giant and fill him with a terrible resolve."- Isoroku Yamamoto

Tue, 2013-02-12 06:07

#18

Arenamontanus Arenamontanus's picture

I like this design a lot!

I like this design a lot! I think droplet radiators are good when you accelerate in a regular way, mainly straight ahead. If you try to dodge the droplets will tend to scatter - good improvised chaff if you are really desperate, but probably not what you want. Overall, this design doesn't look like it would be good for close quarter fighting. It is a carrier of assets, not a battleship. So it will likely do its best to stay far away from trouble: the ideal mission is taking a habitat from afar, and then moving in to take control. So the low acceleration is perfectly fine: if you need it, you are likely doing something wrong.

—

Tue, 2013-02-12 16:06

#19

Jaberwo

NewtonPulsifer wrote:Looks

NewtonPulsifer wrote:
Looks like we don't need to. The droplet radiator equation was already at the projectrho.com page. (0.5 * b * h)/(4r2 + 4r*q + q2) * 4*π*r2

That's not what I meant, this is just the surface area of a bunch of spheres. I would like to know how the calculation of the effective surface area is done (with or without perfect emissivity), that is the surface area that is not occluded by something. I need this so I can make LDRs of the right size that radiate as much heat as the traditional ones. I don't want to use a calculation that does not account for the droplets occluding each other.

NewtonPulsifer wrote:
Very true, but the existence in EP of an invisibility cloak implies it would be not only possible but already old tech. Feasible? Maybe not - the metamaterials might break down under than kind of heat (or high temperature ones might not work as well but an 80/20 split would still be nice). Back at you. You'll have to spell that one out for me, I'm not following you either with that link :)

This link was just the first thing that popped into my mind when I read one-way mirrors. If you scroll down to the second question xkcd explains that there are no one-way mirrors with a nice picture. Metamaterials are a totally different matter of course. But I agree with you on the degrading problem. I don't think it would work. To clarify the x-ray thing: Does the mirror you consider reflect every x-ray photon but one out of 100 - 1000 regardless of incident angle?

NewtonPulsifer wrote:
No one's ever stuck a full-on nuclear reactor in space yet (frankly no one could boost the mass!) - so there's simply never been a need for a droplet radiator. It's a solution in search of a problem right now. The other problem is failure mode. A fission reactor just cannot be turned off immediately. If your droplet radiator had a malfunction it'd likely stop working 100% and you'd likely cook the whole spacecraft (very unlikely to have this failure with an old school radiator) - so you're likely to have regular radiators as backup, reducing its advantage. This isn't as much of a problem with a fusion reactor (many versions shut down in less than a milisecond).....but viable space-borne fusion reactors are of coure still sci-fi. So we're not likely to see a real droplet radiator attempted until we see a high power fission reactor in space.

I was refering to conceptual designs rather than real world examples. Like the Discovery II or the other spacecraft you linked to. They are both rather modern concepts (in terms of the date they were released), but both use solid radiators. Why? I have yet to see a full concept of younger date with a LDR, so that was why I asked you as I assume you might know of some or the reasons for their absence.

NewtonPulsifer wrote:
A 2000 Kelvin difference on hot and cold end of a 4m² isotopically mostly pure diamond (at the 200,000 number) heatpipe 100m long results in a [b]10 gigawatt[/b] transfer. Depending on your assumptions that may or may not be enough. Increase the Kelvin difference and you get a linear improvement. That's 1400 metric tonnes of diamond, though. As a potential heat sink it is 0.63 joules per gram per degree - about 1/7th of water. That's only 882 megajoules for a 2000 degree change (so you have like .1 seconds to shut things down before you start getting into the yellow/red zone).

10GW is not good enough. More than 50GW need to be radiated. And 1000K is more or less the maximum delta T because otherwise radiators would get too big on one end and the reactor would melt on the other. The weight alone makes it impossible and we are only talking about 100m. A few tons of open cycle coolant don't seem too bad compared to this.

Arenamontanus wrote:
I like this design a lot!

Glad you like it. I was very inspired by your paper, please finish it! :) I would like to go a little bit away from the reactor and radiator engineering and talk about the general mode of operation. It would be also quite interesting to know how easily a traget x can get hit at distance y with weapon z etc. If not in absolute numbers, in relation to one another. Will missiles kinetic weapons and lasers all be used at the same time?

Thu, 2013-02-14 15:49

#20

NewtonPulsifer NewtonPulsifer's picture

Regarding liquid drop

Regarding liquid drop radiator calcs - the calculator used that was linked to the projectrho.com website uses an emissivity of 0.07 - that's like shiny aluminum foil. Really not that great. Graphite is like 0.98 - almost a perfect blackbody (1.0). Note emissivity of photons is also your..err.."absorptivity" of the same.link So if you're going to use shiny drops of molten metal and only use one plane of drops, you can ignore the re-absorption. That said I suppose I could draw a circle/sphere from one drop that bisects the other drops and subtract out the slice of surface area from the sphere. Simple enough. Need some paper and free time... Multiple planes of drops on top of each other would require some calculus.

Jaberwo wrote:
To clarify the x-ray thing: Does the mirror you consider reflect every x-ray photon but one out of 100 - 1000 regardless of incident angle?

From the paper (emphasis added) "Ultrahigh-reflectance mirrors are essential optical elements of the most sophisticated optical instruments devised over the entire frequency spectrum. In the X-ray regime, super-polished mirrors with close to 100% reflectivity are routinely used at grazing angles of incidence. However, at large angles of incidence, and particularly at normal incidence, such high reflectivity has not yet been achieved. Here, we demonstrate by direct measurements that synthetic, nearly defect-free diamond crystals [b]reflect more than 99% of hard X-ray photons backwards[/b] in Bragg diffraction, with a [b]remarkably small variation in magnitude across the sample. This is a quantum leap in the largest reflectivity measured to date, which is at the limit of what is theoretically possible.[/b] This accomplishment is achieved under the most challenging conditions of [b]normal incidence[/b] and with [b]extremely hard X-ray photons[/b]." So it does seem useful. Any incidence including normal (dead-on like a bathroom mirror). Their dynamical analysis shows it should reflect up to 17MeV (although they only actually tested with considerably less power).

NewtonPulsifer wrote:
Increase the Kelvin difference and you get a linear

Jaberwo wrote:
10GW is not good enough. More than 50GW need to be radiated.

That seems about 5%. Is that assumption based on Deuterium/Helium 3 fusion with around 5% neutrons causing the heat load?

Arenamontanus wrote:
I like this design a lot!

Jaberwo wrote:
Glad you like it. I was very inspired by your paper, please finish it! :) I would like to go a little bit away from the reactor and radiator engineering and talk about the general mode of operation. It would be also quite interesting to know how easily a traget x can get hit at distance y with weapon z etc. If not in absolute numbers, in relation to one another. Will missiles kinetic weapons and lasers all be used at the same time?

We'll probably need a whole new thread for that :)

—

"I fear all we have done is to awaken a sleeping giant and fill him with a terrible resolve."- Isoroku Yamamoto

Sat, 2013-02-16 06:46

#21

athanasius athanasius's picture

i suggest to consider another

i suggest to consider another aspect for droplet radiator, the mass of the radiator: conventional radiators use a working fluid mass + structural mass, droplet radiator can be considered using only fluid mass (the assumption is that rhe machinery inside the ship is the same and scale lineary with thermal dissipation). Increasing thermal dissipation the structural mass need to be accelerated so you have a decrease of acceleration or an increase in thermal dissipation needs. Droplet radiators are also duble pruposed, can be used as a cloosed loop or as open without changes. The armor needed for normal cruise is more than enought for withstand normal kinetic penetrators, traveling you expect to be hit by micrometeors and leftovers from other ships (EP space is very transport intensive), whipple shields can be a bit oversized and work: i don't expect your enemy use multy Kg penetrators accelerated at very hy Km/s. For X-ray mirror i doubit that can be used for rad shielding, the problem for long range space travel is rad exposure, is simple to deflect charged particles from solar wind (magnetic shielding) mut hard photons need huge masses for shielding and hy Z elements for optimal efficiency.. so why NASA work so hard for find a solution to this problem. I think si possible to use them for boost efficiency of propulsion redirecting some part of energy but i suppose it's a thin effect that can be usefull if the production is economical enought!

Sun, 2013-04-14 00:40

#22

Prophet710 Prophet710's picture

So what would it take to make

So what would it take to make a ship not look like an emaciated ship skeleton. Something more Star Wars or Star Trek esque? <<<<

—

"And yet, across the gulf of space, minds immeasurably superior to ours regarded this Earth with envious eyes. And slowly, and surely, they drew their plans against us."

Sun, 2013-04-14 16:13

#23

Jaberwo

The big problem are the

The big problem are the radiators. They have to be as thin as possible and need to be in a 2D plane and you need lots of them. Also you don't need much structural mass, because the acceleration is not very high (at least with the ships I did so far) On the other hand you need to watch the bending moment so there shouldn't be much mass anywhere else than in front of your engine. Additionally there is not much reason to put everything in a hull, except if you need armor, and even though my ship has it it still looks like you said. No problem for me because I love ships like that. (By the way: most realistic ships look like that) I could try to think of something along your lines if you want, but I guess you have to choose between realistic or cool. I mostly go for cool, but often try to think about the realistic way long enough for it to start feeling cool.

Sun, 2013-04-14 19:25

#24

athanasius athanasius's picture

the armored hull is necessary

the armored hull is necessary for long range travel, micrometeor impacts that impact from all directions are common and if you are far from home no one can help you if there is damage at key elements of the ship. During battle i think it's useless for direct hits but protect from fragments of explosions. i think cool ships will be our future, you must add butterfly wings of radiator to your favored ship and it's ok. the structural mass of radiators can be mitigated if you dispose them so that the shipp "pull" them along, most materials have a great tensile strenght but a limited compression resistance.

Mon, 2013-04-15 04:39

#25

Smokeskin

Anything that wants to

Anything that wants to maneuver fast will want to be relatively compact too. Long structures have much greater rotational inertia and the structures are put under a lot of stress during rotation or hard acceleration along anything but the long axis. I imagine a warship will want to be able to vector thrust quickly in any direction in order to produce a random trajectory - otherwise it'll be a sitting duck against kinetic kill weapons.

Mon, 2013-04-15 12:17

#26

nezumi.hebereke nezumi.hebereke's picture

I feel pretty comfortable

I feel pretty comfortable that the Jovians have basically given that up already if they're big enough to support biomorphs. But I hear what you're saying; TIE Fighters are better than X-Wings (all else being equal).

Mon, 2013-04-15 14:27

#27

NewtonPulsifer NewtonPulsifer's picture

Jaberwo wrote:The big problem

Jaberwo wrote:
The big problem are the radiators. They have to be as thin as possible and need to be in a 2D plane and you need lots of them. Also you don't need much structural mass, because the acceleration is not very high (at least with the ships I did so far) On the other hand you need to watch the bending moment so there shouldn't be much mass anywhere else than in front of your engine. Additionally there is not much reason to put everything in a hull, except if you need armor, and even though my ship has it it still looks like you said. No problem for me because I love ships like that. (By the way: most realistic ships look like that) I could try to think of something along your lines if you want, but I guess you have to choose between realistic or cool. I mostly go for cool, but often try to think about the realistic way long enough for it to start feeling cool.

But if EP has 90% Carnot efficient photovoltaics (that also work at high temperatures - say 1200 degrees Celsius), can't you just absorb the IR radiation from the radiators in layers? If you can extract most of the IR radiation in say 15 layers (and only the first layer needs to be super high efficiency), there would be much less reason to have the radiators splayed out in a 2D radiator shape (maybe). If you have 1 way metamaterial mirrors (or at least more photons in one direction than the other) this becomes even easier. You can "roll up" your radiators and tuck them into the hull, and any "waste" IR photons that aren't worth trapping you can funnel (via the metamaterial mirrors) into a point beam of ER radiation to use as a continuous communication beacon?

—

"I fear all we have done is to awaken a sleeping giant and fill him with a terrible resolve."- Isoroku Yamamoto