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Post by lawson on Dec 9, 2016 5:26:42 GMT
On a whim I decided to make a container ship. It has 11KT of cargo and space for 300 passengers. The drive is a 25GW MPD with 258Km/s exhaust velocity. With a mass fraction of 1.48 and 6KT of reaction mass, it has 101km/s of delta-V and 1mg0 of acceleration. Should be able to do cargo runs between most planets in 3-6 months without having to worry about transfer windows. So I'm curious to see everyone else's designs. Is bigger always better for cargo-ships? Or is the optimum size smaller? Is 1mg0 and 101km/s enough or is it too much? Would a container ship mount a few mega-laser turrets for self-defense? Would a container ship mount a few mega-laser turrets to generate extra revenue as a laser-broom while coasting, and as a traffic tracking satellite while boosting?
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Post by goduranus on Dec 9, 2016 5:35:30 GMT
In my opinion 1mg may be too little? Maybe add another set of 20 MPDs burning xenon or krypton that have higher thrust/power on the opposite end of the ship?
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Post by cutterjohn on Dec 9, 2016 6:20:00 GMT
That seems more like a passenger ship than a cargo vessel. Cargo ships have, in general, greatly optimized for cost efficiency over speed.
Though I admit transit times of months or years could change their business priorities.
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Post by newageofpower on Dec 9, 2016 7:15:18 GMT
In my opinion 1mg may be too little? Maybe add another set of 20 MPDs burning xenon or krypton that have higher thrust/power on the opposite end of the ship? 1mg can escape from all but deepest gravity wells; you just have to ignore Hohmann transfers and constantly do short, outwards+forwards burns. It's horridly dV inefficient, but with MPD you have dV to burn and no thrust at all. Or you can use tandem drive. Here are some offerings from Altarris Heavy Industries:"The ingenious engineers of Altarris's Ne Plus Ultra Special Projects Department have returned once again, this time in the purely civilian Virgo Product line. Today, we announce our newest release, the [Virgo] Highliner - the fastest Saturine-Martian Passenger transport in existence! For a mere 1.03 Gigacredits, this luxurious and absurdly fast transport can be yours!" "Like all Ne Plus Ultra designs, the Highliner generates 200 gigawatts of power to pump an MPD, achieving incredible fuel/speed efficiencies, and dramatically cutting travel times." "However, we are aware that some retarded special needs captains may wish to take their ship deep within a planetary gravity well, instead of having his passengers board via personnel shuttles or dV-minimizing orbital tetherhooks. For these situations, they can activate up to six Methane Nuclear-Thermal torches and produce nearly 90 miligravities of acceleration, more than sufficient for Hohmann transfer from even Venusian low orbit! Please be aware that applying full drive thrust while in low Jupiter or Uranian orbit is beyond the safe structural integrity rating of the Highliner's Frame and may void your warranty." "Moving over twenty thousand passengers in luxury, the Highliner has seperate Economy, Business, and First Class sections, in addition to seperate Crew Compartments. In a pinch, the Highliner's 7 kiloton cargo bays (normally for shipping First Class client's belongings) can load additional passengers. And of course, the Highliner includes the Award-winning "CancerBGone 1" Anti-Radiation Armor Schema, featuring heavy Boron and Lithium-6 shielding; guaranteed under 25 mSv yearly dosage!" 1. Guarantee does not apply to travelling in Van Allen Belts, within Io's orbital Shadow, or sustained nuclear bombardment. Please refer legal questions to the Ganymede Department of Justice. "For mercantile captains that can't put up with crowds of other people not strictly under their control (we feel your pain) Ne Plus Ultra has developed the [Virgo] Megafreighter!" "New colony ran out of XY or Z? Both sides of a civil war want to buy missiles from you? Want to hide a fleet in your cargo bays? Carrying up to seventy kilotons of cargo (not counting fuel delivery possibilities), the Megafreighter's possibility of making money is only limited by your imagination, and has won the Capitalist of the Year award from New Libertarian Magazine! Buy now for a low introductory price of 634 Megacredits 2!" 2. Offer available while supplies last. Promotion is unavailable in Mercurian and Uranian Orbits. Additional Shipping and Handling expenses may be added for Cerean deliveries."And, of course, the award-winning Radiation-shielding scheme has shown to increase crew morale by 43%! Imagine that, a crew deciding not to mutiny simply because they aren't dying of radiation poisoning! Who would have thought?" "Finally, the long awaited Methane conversion of the original [Cygnus] Ultratanker; the [Virgo] Ultratanker. Found yourself with a futures contract for 300 kilotons of Methane? We're here to help!" "Avoid Bankruptcy! Go really fast! Refuel other multi-hundred kiloton Methane hogs! The Ultratanker, now utilizing the most widespread Civilian fuel, is available for only 772 Megacredits!"
I'll post up more tomorrow. In addition to 300kt 200 GW long range monster craft, I've designed an extensive line of smaller, cheaper refuelers and utility vessels. [Altarris] is my tag for most military objects, using Decane, [Cygnus] is granted to Decane-propelled unarmed logistics vessels, whilst [Virgo] is the purely methane-using Civilian line of products.
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Post by dragonkid11 on Dec 9, 2016 7:40:35 GMT
...Jesus Christ.
*Looks at his (Relatively) tiny supply ship.*
I'm feeling pretty inadequate now.
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Post by zuthal on Dec 9, 2016 7:44:53 GMT
Contrary to what you might think, I think a cargo ship would have at least marginal armour - in order to protect against micrometeorites.
Also, those reactors seem maybe a bit unreasonably powerful for what a civilian ship could have - I do not think civvies would be allowed to run weapons-grade fuel, maybe 10% enrichment maximum.
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Post by lawson on Dec 9, 2016 8:25:55 GMT
That seems more like a passenger ship than a cargo vessel. Cargo ships have, in general, greatly optimized for cost efficiency over speed. Though I admit transit times of months or years could change their business priorities. The Stevedore delivers 11kT of cargo using at most 6kT of hydrogen with transit times short enough to make 2-4 trips a year. The low fuel consumption and high utilization should make it a profitable ship even without refitting the ship to also take laser-broom and tracking contracts. The space for 300 passengers takes just over 1Kt of ship mass and adds another revenue source or greatly improves crew morale. The reason Hydrogen is used is because it gives the best exhaust velocity for a given MPD power. It would be interesting to see if switching to Neon improves the ship cost and acceleration.
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Post by newageofpower on Dec 9, 2016 8:42:46 GMT
The reason Hydrogen is used is because it gives the best exhaust velocity for a given MPD power. It would be interesting to see if switching to Neon improves the ship cost and acceleration. My [Cygnus] line use Decane because they support Decane-fueled warships (which use Decane to reduce cross section and increase armor efficiency). I see civilian ships using Methane if we enter a energy-rich version of CoADE or where the gas giant systems are heavily exploited; it doesn't leak the way hydrogen does, and is far more easily extracted/processed/stored than Hydrogen. Plus, production of Hydrogen usually means the catalytic destruction of water - another precious resource in space. Thus, the [Virgo] line uses Methane propellant.
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Post by n2maniac on Dec 9, 2016 8:51:58 GMT
Okay, at some point the cost of the nuclear fuel has to be considered and current ingame models do not do this too well. Looking for some rough numbers... 7-50 GWd/t fuel ( source), lets round it up to 100 GWd/t. That is about 8.6PJ/t or TJ/kg. To exhaust propellant efficiently at 258km/s, we have to put ~33 GJ/kg propellant into it. Divide the two, we need ... a kg of nuclear fuel per 261kg of propellant? Give or take a factor of 10 for my rough source number, but isn't nuclear fuel at least many hundreds of times more valuable than propellants? Does this sound off to anyone else? (Of course ignoring that if it is not enforced ingame, we will willingly ignore the limitation) Also: The reason Hydrogen is used is because it gives the best exhaust velocity for a given MPD power. It would be interesting to see if switching to Neon improves the ship cost and acceleration. ...do you see a noticeable difference by the time the exhaust velocity is in the 100km/s neighborhood? That... really shouldn't be significant at that point...
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Post by lol on Dec 9, 2016 10:39:58 GMT
Contrary to what you might think, I think a cargo ship would have at least marginal armour - in order to protect against micrometeorites. Also, those reactors seem maybe a bit unreasonably powerful for what a civilian ship could have - I do not think civvies would be allowed to run weapons-grade fuel, maybe 10% enrichment maximum. Who an enforce enrichmment limits when reaction wheels running 10 times faster then any modern isotope separation centrifuges are avaliabe? Magnetic bearings in 0G with plenty of power are a child's play.
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Post by lawson on Dec 9, 2016 16:49:44 GMT
The reason Hydrogen is used is because it gives the best exhaust velocity for a given MPD power. It would be interesting to see if switching to Neon improves the ship cost and acceleration. My [Cygnus] line use Decane because they support Decane-fueled warships (which use Decane to reduce cross section and increase armor efficiency). I see civilian ships using Methane if we enter a energy-rich version of CoADE or where the gas giant systems are heavily exploited; it doesn't leak the way hydrogen does, and is far more easily extracted/processed/stored than Hydrogen. Plus, production of Hydrogen usually means the catalytic destruction of water - another precious resource in space. Thus, the [Virgo] line uses Methane propellant. Excellent reasons to choose Decane or Methane. We should let the market decide! Realistically, I would expect most cargo ships to be able to use multiple types of reaction mass so they can fill up on whatever is cheap locally. Hydrogen leaking out of tanks is a pain in the rear, but I don't expect it will be hard to work around. Double walled tanks and a compressor to recycle whatever leaks into the gap should cut the leak rate to practically zero. Also, Hydrogen isn't hard to get if you scoop it out of a gas giant and ship it using a Stevedore class ship refit as a hydrogen tanker. Hydrogen gets even cheaper if you can arrange to only ship during Holman transfer windows. (should be able to get a mass ratio of 1.1 or lower!)
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Post by lawson on Dec 9, 2016 16:55:00 GMT
...do you see a noticeable difference by the time the exhaust velocity is in the 100km/s neighborhood? That... really shouldn't be significant at that point... Yes I see a noticeable difference. Don't have time right now to make examples. I'm guessing 25GW methane MPD would only get up to the 180Km/s ballpark. I've also been assuming that cargo ships would want to minimize propellant mass ratio for a given delta-V to maximize cargo capacity.
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Post by amimai on Dec 9, 2016 17:30:48 GMT
I present the Nostalgia for Infinity! Built during the golden age of interstellar trade, the Nostalgia for Infinity, a veritable flying city capable of holding over 10,000 passengers in the lap of luxury while also carrying over 150kt of trade goods and up to 1/2 of its fuel tank for trade purposes is one of the largest freighters ever built. Capable of making a round trip to Jupiter
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Post by thorneel on Dec 9, 2016 18:09:17 GMT
However, we are aware that some retarded special needs captains may wish to take their ship deep within a planetary gravity well, instead of having his passengers board via personnel shuttles or dV-minimizing orbital tetherhooks. For these situations, they can activate up to six Methane Nuclear-Thermal torches and produce nearly 90 miligravities of acceleration, more than sufficient for Hohmann transfer from even Venusian low orbit! Why use nuclear-thermal instead of resistojets? You should have enough available power from the (now unused) MPDs, resistojets are way lighter and cheaper, and you can reach higher temperature, and as such higher efficiency. My dual-engines are always MPD/resistojet for this reason. I present the Nostalgia for Infinity! You do like ominous ship names, don't you? (Also, does it come with pre-installed hypometric weapons?)
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Post by amimai on Dec 9, 2016 18:30:17 GMT
However, we are aware that some retarded special needs captains may wish to take their ship deep within a planetary gravity well, instead of having his passengers board via personnel shuttles or dV-minimizing orbital tetherhooks. For these situations, they can activate up to six Methane Nuclear-Thermal torches and produce nearly 90 miligravities of acceleration, more than sufficient for Hohmann transfer from even Venusian low orbit! Why use nuclear-thermal instead of resistojets? You should have enough available power from the (now unused) MPDs, resistojets are way lighter and cheaper, and you can reach higher temperature, and as such higher efficiency. My dual-engines are always MPD/resistojet for this reason. I present the Nostalgia for Infinity! You do like ominous ship names, don't you? (Also, does it come with pre-installed hypometric weapons?) its only the year 2250, the night is still young. also I just realised, I can fit a whole fleet inside the cargo bays of this thing, and its hull is wider then 95% of my ships are long... that is sort of terrifying Possibly even more terrifying is that such a ship would probably be commercially viable shipping bulk cargo up to Jupiter and Uranus, then running gas back to earth in vast volumes. A single run could provide fuel for all normal space traffic around a planet for months, and since something this large or larger is the only way to make a round trip without using up much fuel, it would hold a near monopoly on such trade runs.
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