Thought experiment... ultra long range travel

[Liam's Ghost]

The mission: travel thirty thousand light years successfully. then return, bringing a living crew the full way.

Resources: Age of War (2300) level technology, including primitive jumpship technology (up to 200,000 tons). In addition, you have access to cryopods with all the capabilities (and weaknesses) of those published in A Time of War. Each one takes up two tons of space.

This mission is considered to be of utmost importance to your people, so every option for getting the job done (save slow boating, I mean, come on!) will be considered, no matter how resource intensive.

[The_Caveman]

That's about 80 man-years of travel time, not counting stopovers. You're going to need a lot of supplies. Assuming you divide the crew into three shifts and put two of them in cryo-stasis to be cycled every year, you're looking at about 40 cryo-pods and 3000 tons of food and water for a minimum-size JumpShip crew, plus whatever supplies are required by the cryotubes. At minimum. You'll probably want at least double that in case of emergencies, plus extra crew just in case, and any DropShuttle or small craft crews are going to add to the total.

And there's the fuel. You'll have little choice but to refuel multiple times along the way, as even stationkeeping for 29,000 days is going to be a prohibitive amount of fuel to carry.

[Daryk]

Hmmm... 30,000 light years is a minimum of 1,000 jumps.  Do you know what portion of that distance will involve interstellar space?  Stars mean using the jump sail to recharge, thus saving fuel.  If it was ALL interstellar, practically the entire ship would would need to be fuel.

Per StratOps, using the power plant alone burns a base 10 burn days of fuel, less 0.5 burn day per Margin of Success to a minimum of 4 burn days.  With 10 levels of skill in Piloting/Spacecraft, and 7s in REF and DEX, you could have a base -4 target, meaning a minimum MoS of 6 (or 7 burn days per jump).  Throwing Natural Aptitude on top of that won't change the minimum, but it will skew the statistical burn rate down.  A -4 base could also guarantee success in charging the drive in 20 hours, but that would take the full 10 burn days of fuel.  Given the relative weight of consumables for the crew against the fuel, you'll want to save fuel.  The fixed cost of charging the drive with fuel will drive you to the maximum possible ship weight.  At the bare minimum (quick charging every time at 150 hours to maximize fuel savings), you need 6,250 days to make the journey (over 17 years one way, doubled for the round trip).

One possible fiddle is to take the "no failure" for 175 hours of quick charging to mean the minimum fuel is burned (4 burn days, or 79 tons).  This increases your need for consumables (by 1,000 days per leg), but reduces the fuel requirements.  Using stars to recharge for part of the journey will reduce it further.

I just ran the math for the station keeping fuel burn rate, and it's about 2 tons per day.  That means refueling by grabbing icy Kuiper Belt Objects will probably be necessary.

Using fractional accounting, you can design the ship at 199,999 tons, just below the break point for tons/burn day (keeping it at 19.75 tons vice 39.52).  You're going to want to do this, because every single ton counts on a mission like this.  With Compact Core technology (from a later era), you might be able to design a 99,999 ton ship that could make the journey (or a 49,999 ton one with the Illegal quirk).

So anyway, at 199,999 tons:
Engine (Station Keeping): 0.2 x 0.06 x 199,999 = 2,400 tons
Fuel and Pumps: 5,000 tons, 100 tons for pumps (this enables the ship to traverse voids of almost 1,900 light years)
SI (1): 200 tons
K-F Drive (30 LY is the only thing that makes sense given the fixed fuel consumption): 189,999 tons
Sail: 40 tons
Controls: 500 tons
Crew: 85 (15 are officers) (Primitive JumpShips use WarShip crews... yikes!)
Steerage Quarters: 425 tons
Grav Deck (50m): 50 tons
Small Craft Bay: 200 tons
Additional Steerage Quarters: 25 tons
Armor: 10 tons (1 point per facing)
1,050 tons of consumables at 200 person-days per ton = 210,000 person days/90 persons = 2,333 days

That clearly won't work... if you allow modern JumpShip crewing, that cuts things down dramatically:
Engine (Station Keeping): 0.2 x 0.06 x 199,999 = 2,400 tons
Fuel and Pumps: 5,000 tons, 100 tons for pumps
SI (1): 200 tons
K-F Drive (30 LY is the only thing that makes sense given the fixed fuel consumption): 189,999 tons
Sail: 40 tons
Controls: 500 tons
Crew: 16 (3 are officers: CO, XO/Navigator, Engineer)
Steerage Quarters: 80 tons
Grav Deck (50m): 50 tons
Small Craft Bay: 200 tons
Additional Steerage Quarters: 25 tons
Armor: 10 tons (1 point per facing)
1,395 tons of consumables at 200 person-days per ton = 279,000 person-days/21 persons = 13,285 days (not quite enough)

Finally, substituting Stasis Tubes for the Small Craft crew (the ship crew is apparently necessary to operate the ship) could stretch the consumables well in excess of 17,000 days, which should be enough:
Engine (Station Keeping): 0.2 x 0.06 x 199,999 = 2,400 tons
Fuel and Pumps: 5,000 tons, 100 tons for pumps (2,531 burn days at station keeping rate)
SI (1): 200 tons
K-F Drive (30 LY is the only thing that makes sense given the fixed fuel consumption): 189,999 tons
Sail: 40 tons
Controls: 500 tons
Crew: 16 (3 are officers: CO, XO/Navigator, Engineer)
Steerage Quarters: 80 tons
Grav Deck (50m): 50 tons
Small Craft Bay: 200 tons
Stasis Tubes for Small Craft Crew: 10 tons
Armor: 10 tons (1 point per facing)
1,410 tons of consumables at 200 person-days per ton = 282,000 person-days/16 persons = 17,625 days (48 years and a bit of margin)

The margin in consumables would enable the Small Craft crew to be wakened a few times during the journey to do refueling operations (capturing an icy KBO and harvesting the water/hydrogen).

EDIT: See my next post... some accidental key combination hit post...

[Daryk]

Damn it... mis-keyed while I was adding a response to Caveman's post... I only got 40 years of travel time, not 80.  Obviously, we're using different charging rates, but I wouldn't have expected it to cause a factor of 2 difference...

[Natasha Kerensky]

Invent L-F batteries.

[Daryk]

They'd still require the same number of days at station keeping, or additional refueling stops (you can only charge both by burning fuel while the sail takes care of the other, and there's not enough room for enough fuel).

[Giovanni Blasini]

Is there anything stopping you from looking for comets or other sources of water or hydrogen and refueling along the way?

[Daryk]

That's actually a requirement for this mission.  There's simply no way to cram in enough fuel.

[The_Caveman]

Damn it... mis-keyed while I was adding a response to Caveman's post... I only got 40 years of travel time, not 80.  Obviously, we're using different charging rates, but I wouldn't have expected it to cause a factor of 2 difference...

I was under the impression that primitive JumpShips were limited to 15 LY jumps, not 30. And I was assuming a standard 175-hour charge. Quick-charging that often would incur too much wear-and-tear.

[Liam's Ghost]

I was under the impression that primitive JumpShips were limited to 15 LY jumps, not 30. And I was assuming a standard 175-hour charge. Quick-charging that often would incur too much wear-and-tear.

Primitive jumpships can have a jump range from 15 to 30 light years. The longer the jump range, the bigger the jump core. At 30 light years, it masses the same as a standard core.

[Daryk]

Ah, there's that factor of two, then.  Glad to know my math was right!  :)

[The_Caveman]

If you can build a modern JumpShip, fit it with a single docking collar and carry a DropShip for use as a self-refilling external fuel tank.

Something like the following:

Code: [Select]

Base Tech Level: Standard (IS)
Level          Era
-------------------
Experimental    - 
Advanced        - 
Standard      2500+
Tech Rating: D/D-E-D-D

Weight: 50,000 tons
BV: 1,020
Cost: 447,412,000 C-bills

Movement: 1/2
Heat Sinks: 101
Fuel Points: 400,000 (40000.0 tons)
Tons Per Burn Day: 8.37

Structural Integrity: 10
Armor: 120
            Armor 
-------------------
Nose           36 
Left Side      30 
Right Side     30 
Aft            24 

Weapons          Loc  Heat 
----------------------------
Laser Bay        AFT    8   
Large Laser                 
Laser Bay (R)     LS    8   
Large Laser (R)             
Laser Bay (R)     RS    8   
Large Laser (R)             
Laser Bay         LS   16   
Large Laser                 
Large Laser                 
Laser Bay         RS   16   
Large Laser                 
Large Laser                 
Laser Bay        NOS   40   
Large Laser                 
Large Laser                 
Large Laser                 
Large Laser                 
Large Laser                 



Carrying Capacity
-----------------
Small Craft (1 door) - 1 unit (2 recovery open)
Cargo Space (1 door) - 4,148 tons

Crew                 
----------------------
Officers             3
Enlisted/Non-rated  10
Gunners              2
Bay Personnel        5
The large lasers are for boring holes in the surface of comets so that buried ice can be extracted.

[Daryk]

That's the hard part of 2300 being the baseline... modern drop collars (and KF booms) don't exist yet.

[Giovanni Blasini]

But modern compact KF cores do. They're considered prototype in 2290, but production in 2300.  Assuming someone with a bankroll like the late Terran Alliance, you could conceivably have a compact-core exploration ship in this period.

[Daryk]

In my defense, I did mention compact cores could make this mission a bit easier.  Not sure that was Liam's intent, though...

[Liam's Ghost]

My original idea was to solve the problem with primitive jumpships. I'm not entirely certain I'm against it, though, given the obstacles this presents. I guess I'd like folks to try this with primitive jumpships first before falling back on compact core vessels.

Though I will reiterate that modern jumpships, modern docking collars, and modern jumpship sized crews are right out.

The backstory is a colony fleet (or at least half of it) suffered a catastrophic misjump in 2300 that dropped them somewhere thirty thousand light years from the Inner Sphere (and they don't know it yet, but hundreds of years in the future).

If that sounds a bit asspull, well it is, but it's also going to be a plot point for the "And I Feel Fine" universe, which is basically built on asspulls.  ;D

(though humorous aside, the longest canon survivable misjump was close to seven hundred light years. However that record was only formally established because the jumpship was intact enough to make it back eventually and make contact with Comstar. It's possible, in a silly, out there kinda way, that mankind has been inadvertently seeding the galaxy with settlements through misjumps)

Also, I came up with my own idea for this experiment, but I'm not gonna say what. I wanna see if others can come up with a more practical solution than me. 

[Daryk]

Hmm... I'm not sure it's possible at all with nearly five times the people.  The rules for crew imply you have to have all of them to operate.  Cutting down on the fuel (dramatically) on the assumption you'll be refueling from KBOs periodically might get you there.  I'll run the math...

[Daryk]

Ok, here goes nothing...

Engine (Station Keeping): 0.2 x 0.06 x 199,999 = 2,400 tons
Fuel and Pumps: 1,000 tons, 20 tons for pumps (this enables the ship to traverse voids of almost 400 light years)
SI (1): 200 tons
K-F Drive (30 LY is the only thing that makes sense given the fixed fuel consumption): 189,999 tons
Sail: 40 tons
Controls: 500 tons
Crew: 85 (15 are officers) (Primitive JumpShips use WarShip crews... yikes!)
Steerage Quarters: 425 tons
Grav Deck (50m): 50 tons
Small Craft Bay: 200 tons
Additional Steerage Quarters: 25 tons
Armor: 10 tons (1 point per facing)
5,130 tons of consumables at 200 person-days per ton = 1,026,000 person days/90 persons = 11,400 days

That's 31 years of consumables for all 90 personnel (no stasis tubes).  Since they're only going one way, that should be enough, at least as long as they don't have to traverse any interstellar voids wider than 400 light years.  This also assumes fairly frequent refueling via KBO capture.  If they really need enough to go 30,000 light years TWICE without replenishment, this won't cut it.

[Liam's Ghost]

Since it's been a while, I'll post my original idea.

Stock Aquilla (well, more or less. It would be upgraded to 2300 standards).

By my calculations, the barest minimum of consumable supplies necessary for the trip would be close to twelve thousand tons. And there would have to be stopovers to top off from comets or other KBOs along the way.

Good news though, the Aquilla has space for twenty thousand tons of cargo. We could even up that to over thirty thousand simply by pulling extraneous systems out (primarily the dropshuttle bays).

Bad news, it would take probably eighty years as Caveman indicated. The warranty may very well run out (IE shit breaks down) long before that.

EDIT: Another option might be to use aquillas that keep their dropshuttle bays to set up midpoint stations on the way,  where ships can stop for needed maintenance or resupply (you can put five thousand ton stations in dropshuttle bays). Of course that would take EVEN LONGER and be a lot more resource intensive.

[Daryk]

How far can the Aquila jump again?  I'm thinking 12,000 tons is a bit short...

[Liam's Ghost]

How far can the Aquila jump again?  I'm thinking 12,000 tons is a bit short...

15 light years with a crew of eighty. Going thirty thousand light years and then back would be 4000 jumps.

It should be 11,230 of consumables, unless I screwed up my maths somewhere.

[Daryk]

Ah, a lower crew requirement... that's what was tripping me up.

[The_Caveman]

The standard rules assume water and food used by the crew is simply lost. In reality a spaceship is a closed system. Waste, sweat, exhaled water vapor and carbon dioxide, all of it stays onboard the ship until you do something with it.

What's more, that stuff is damn useful: hydrogen, oxygen, carbon, nitrogen, and trace nutrients--plant food. 5kg per person per day really adds up over decades of travel, and you'd have to be an idiot to vent all of that into space.

If all water (along with most of the atmospheric humidity) and human waste are recycled into onboard gardens instead, that would cut your supply requirements drastically. You'd have a fixed cost for the mass of the gardens, but you'd be recycling that same mass over and over.

The big hurdle remains having enough fuel to cross interstellar voids. You'll burn LH2 like crazy charging the KF drive between hops and even cracking comets to refuel puts serious limits on how far you can make it. You might not be able to plot a course "as the crow flies" and instead stick to regions of space that have usable stars, though it would increase the length of your journey.

[kato]

You'd have a fixed cost for the mass of the gardens, but you'd be recycling that same mass over and over.

I've calculated basic hydroponic systems based on larger-scale vertical farm proposals, and in an optimized fashion for that crew of 80 you could get away with a 150-ton installation tended to by two men in order to provide (vegetarian) 2000 kcal meals for the crew.

Notably though this does not produce sufficient oxygen and does need a minimal water intake itself. Provided you're able to recycle your water on a similar scale to the oxygen production of the gardens (45%) you'd save realistically about 65% on provisions compared to standard operations.

If you want to abstract that, just house-rule something like 50-ton modules supplying 20 men each that lower "consumption" cost to 1 ton per 500 man-days.

[Maingunnery]

What about abstracting that tonnage into having first-class quarters for everyone?

[kato]

Works out fine for the base mass cost, though personally i prefer to have the discrete "separate module" in order to differentiate such ships from "standard" ships.

[The_Caveman]

I wouldn't count on hydroponic gardens to provide all your oxygen anyway. They're for feeding the crew. The main benefit the plants have, atmosphere wise, is scrubbing the air of contaminants so it's healthier and smells better--with a side benefit of regulating humidity.

You'd want to do your primary air recycling chemically, but even that could be significantly offset by lining all the corridors in the ship with "greenwalls". This would also have serious psychological benefits for the crew. And it would facilitate water recycling, as wastewater and condensation could be filtered through the plant beds first.

On a short-term basis it would only offset your supply requirements, but long-term almost none of the consumables used by the crew should actually be lost. Even discarded clothing, if made of natural fibers, could be ground into fertilizer for the gardens. Carbon and oxygen captured into the life-support scrubbers could be recycled periodically as there is abundant electrical power to crack molecules. Water lost to the air might not be economically feasible to recover on short-term missions, but over years simple condensers would capture it for recycling.

I'd go as far as making special long-term quarters that were heavier than first-class berths to account for the extensive recycling equipment--which would need to be multiply redundant on a decades-long voyage.

And unless you launch with a single-sex crew, you'll need a little extra passenger capacity to account for any happy accidents that occur along the way.

[Liam's Ghost]

I've calculated basic hydroponic systems based on larger-scale vertical farm proposals, and in an optimized fashion for that crew of 80 you could get away with a 150-ton installation tended to by two men in order to provide (vegetarian) 2000 kcal meals for the crew.

Notably though this does not produce sufficient oxygen and does need a minimal water intake itself. Provided you're able to recycle your water on a similar scale to the oxygen production of the gardens (45%) you'd save realistically about 65% on provisions compared to standard operations.

If you want to abstract that, just house-rule something like 50-ton modules supplying 20 men each that lower "consumption" cost to 1 ton per 500 man-days.

Neat stuff.

"scribbles down notes" gonna use these figures in my next Denizens entry.

[Daryk]

I hope Cray sees those numbers too... We might someday get them in the rules!  :thumbsup:

[kato]

The interesting part about the numbers is that they don't really impact "regular" gameplay due to the timespans involved.

Such a hydroponic facility is only viable if your ship spends literally years in space without resupply - for the simplified version (first-level quarters for everyone) the break-even point in mass is 27.4 months, for the abstracted version ("50-ton module for every 20 crew, round up") it can get rather higher to extreme numbers.

Originally developed the module for colonization myself - a quick-fix CF75 vertical farm single-hex, two-level building that can be rolled off a dropshuttle as a superheavy tracked trailer and within 3 weeks setup time supports up to 150 people long-term with the extra required supplies amounting to 1 ton per 1400 man-days (!) - and those are 97% products one could produce in other similar modules. Scalable.