Author Topic: Thought experiment... ultra long range travel  (Read 7697 times)

Daryk

  • Lieutenant General
  • *
  • Posts: 37059
  • The Double Deuce II/II-σ
Re: Thought experiment... ultra long range travel
« Reply #30 on: 14 July 2019, 06:08:18 »
Cool... and I think your 50-ton module could easily fit the fluff of the Invader's hydroponic garden domes.

kato

  • Captain
  • *
  • Posts: 2417
Re: Thought experiment... ultra long range travel
« Reply #31 on: 14 July 2019, 06:55:59 »
Cool... and I think your 50-ton module could easily fit the fluff of the Invader's hydroponic garden domes.
Yeah, that was also what i was thinking of with the size class.

For space applications you'd probably dedicate some space to algae tanks for increased oxygen production and improved water recycling systems though, thus lowering yield a bit. I'd not-quite-randomly go with 15 people instead of 20 supported by such a module in a full supply-independent layout. Would still give an Invader a 25% production surplus with two domes that fits with the fluff.

Giovanni Blasini

  • Lieutenant Colonel
  • *
  • Posts: 7103
  • And I think it's gonna be a long, long time...
Re: Thought experiment... ultra long range travel
« Reply #32 on: 15 July 2019, 13:37:25 »
I blame all of you for this:

Code: [Select]
                    AeroTech 2 Vessel Technical Readout
                                  VALIDATED

Class/Model/Name:  Constitution Class Heavy Cruiser
Tech:              Inner Sphere / 2240
Vessel Type:       WarShip
Rules:             Level 3, Standard design
Rules Set:         AeroTech2

Mass:              190,000 tons
K-F Drive System:  (Unknown)
Length:            288 meters
Power Plant:       *Primitive Fusion (2240)*
Safe Thrust:       3
Maximum Thrust:    5
Armor Type:        Standard
Armament:         
    6 NL35
    2 Barracuda
------------------------------------------------------------------------------
Class/Model/Name:  Constitution Class Heavy Cruiser
Mass:              190,000 tons

Equipment:                                                            Mass 
Power Plant:  *Primitive Fusion (2240)*                             47,880.00
Thrust:  Safe Thrust: 3
      Maximum Thrust: 5
K-F Hyperdrive:  *Primitive KF Drive (15 LY)* (Integrity = 5)       95,000.00
Jump Sail: No Sail (Fusion-Charged K-F)                                   .00
Structural Integrity: 60                                            11,400.00
Total Heat Sinks:    354 Single                                           .00
Fuel & Fuel Pumps:                                                   4,080.00
Bridge, Controls, Radar, Computer & Attitude Thrusters:                475.00
Fire Control Computers:                                                   .00
Armor Type:  Standard  (114 total armor pts)                           129.50
                           Capital Scale Armor Pts
   Location:                            L / R
   Fore:                                 19
   Fore-Left/Right:                   19/19
   Aft-Left/Right:                    19/19
   Aft:                                  19

Cargo:
   Bay 1:  Small Craft (6) with 2 doors                              1,200.00
   Bay 2:  Cargo (1) with 2 doors                                   21,578.00

Grav Decks #1 - 2:  (90-meter diameter)                                100.00
Escape Pods:  48 (7 tons each)                                         336.00

Crew and Passengers:
     25 Officers (25 minimum)                                          250.00
    121 Crew (58 minimum)                                              847.00
      8 Gunners (8 minimum)                                             56.00
     10 1st Class Passengers                                           100.00
    100 2nd Class Passengers                                           700.00
     21 Marines                                                        105.00
     30 Bay Personnel                                                     .00
Weapons and Equipment      Loc        SRV    MRV    LRV    ERV  Heat    Mass
------------------------------------------------------------------------------
2 NL35                     Nose         7      7      7     --  104  1,400.00
2 Barracuda(20 msls)       Nose         4      4      4      4   20    780.00
2 NL35                     FL/R         7      7      7     --  208  2,800.00
1 Small Naval Comm-Scanner                                              75.00
1 Weight Padding                                                       708.50
------------------------------------------------------------------------------
TOTALS:                                              Heat: 332     190,000.00
Tons Left:                                                                .00

Calculated Factors:
Total Cost:        969,228,000 C-Bills
Battle Value:      12,474
Cost per BV:       77,699.86
Weapon Value:      7,424 (Ratio = .60)
Damage Factors:    SRV = 233;  MRV = 233;  LRV = 188;  ERV = 80
Maintenance:       Maintenance Point Value (MPV) = 223,649
                   (94,221 Structure, 121,010 Life Support, 8,418 Weapons)
                   Support Points (SP) = 174,777  (78% of MPV)
BattleForce2:      Not applicable


Code: [Select]
                    AeroTech 2 Vessel Technical Readout
                                  VALIDATED

Class/Model/Name:  New WarShip
Tech:              Inner Sphere / 2300
Vessel Type:       WarShip
Rules:             Level 2, Standard design
Rules Set:         AeroTech2

Mass:              200,000 tons
K-F Drive System:  (Unknown)
Length:            288 meters
Power Plant:       Standard
Safe Thrust:       3
Maximum Thrust:    5
Armor Type:        Standard
Armament:         
   12 NL55
    2 Barracuda
------------------------------------------------------------------------------
Class/Model/Name:  New WarShip
Mass:              200,000 tons

Equipment:                                                            Mass 
Power Plant, Drive & Control:                                       36,000.00
Thrust:  Safe Thrust: 3
      Maximum Thrust: 5
Kearny-Fuchida Hyperdrive:  Compact (Integrity = 6)                 90,500.00
Jump Sail: No Sail (Fusion-Charged K-F)                                   .00
Structural Integrity: 60                                            12,000.00
Total Heat Sinks:    354 Single                                         41.00
Fuel & Fuel Pumps:                                                   5,369.00
Bridge, Controls, Radar, Computer & Attitude Thrusters:                500.00
Fire Control Computers:                                                   .00
Armor Type:  Standard  (180 total armor pts)                           239.50
                           Capital Scale Armor Pts
   Location:                            L / R
   Fore:                                 30
   Fore-Left/Right:                   30/30
   Aft-Left/Right:                    30/30
   Aft:                                  30

Cargo:
   Bay 1:  Small Craft (6) with 2 doors                              1,200.00
   Bay 2:  Cargo (1) with 2 doors                                   37,527.00

Grav Decks #1 - 2:  (90-meter diameter)                                100.00
Escape Pods:  48 (7 tons each)                                         336.00

Crew and Passengers:
     26 Officers (26 minimum)                                          260.00
    118 Crew (59 minimum)                                              826.00
     14 Gunners (14 minimum)                                            98.00
     10 1st Class Passengers                                           100.00
    100 2nd Class Passengers                                           700.00
     21 Marines                                                        105.00
     30 Bay Personnel                                                     .00
Weapons and Equipment      Loc        SRV    MRV    LRV    ERV  Heat    Mass
------------------------------------------------------------------------------
2 NL55                     Nose        11     11     11     11  170  2,200.00
2 Barracuda(20 msls)       Nose         4      4      4      4   20    780.00
2 NL55                     FL/R        11     11     11     11  340  4,400.00
2 NL55                     L/RBS       11     11     11     11  340  4,400.00
2 NL55                     Aft         11     11     11     11  170  2,200.00
1 Small Naval Comm-Scanner                                              75.00
1 Weight Padding                                                        43.50
------------------------------------------------------------------------------
TOTALS:                                            Heat: 1,040     200,000.00
Tons Left:                                                                .00

Calculated Factors:
Total Cost:        1,516,283,304 C-Bills
Battle Value:      15,147
Cost per BV:       100,104.53
Weapon Value:      14,195 (Ratio = .94)
Damage Factors:    SRV = 220;  MRV = 220;  LRV = 175;  ERV = 73
Maintenance:       Maintenance Point Value (MPV) = 196,015
                   (75,315 Structure, 97,000 Life Support, 23,700 Weapons)
                   Support Points (SP) = 180,066  (92% of MPV)
BattleForce2:      Not applicable
« Last Edit: 15 July 2019, 13:49:28 by Giovanni Blasini »
"Does anyone know where the love of God goes / When the waves turn the minutes to hours?"
-- Gordon Lightfoot, "The Wreck of the Edmund Fitzgerald"

idea weenie

  • Major
  • *
  • Posts: 4855
Re: Thought experiment... ultra long range travel
« Reply #33 on: 15 July 2019, 21:25:02 »
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.

50-ton module divided by 20 people, is 2.5 tons per person

So assuming Steerage quarters (5 tons, 1 ton of food per 200 man-days) vs Long-term Steerage Quarters (7.5 tons, 1 ton of food per 500 man-days), let's run the numbers:
5+1/200 * X = 7.5 + 1/500 * X
1/200 * X = 2.5 + 1/500 * X
1/200 * X - 1/500 * X = 2.5
5 * X - 2 * X = 2500
3 * X = 2500
X = 833 days

For 2nd Class (7 tons vs 9.5 tons):
7+1/200 * X = 9.5 + 1/500 * X
1/200 * X = 2.5 + 1/500 * X    (This is identical to above, so it will be 833 days as well)

So for any trip over 833 days (aka over 2.28 years), adding this hydroponic facility will make sense.

Of course, this might be basic algaeculture, where you are eating flavored plant paste, instead of various types of hydroculture plants, plus fish, shellfish, etc.

kato

  • Captain
  • *
  • Posts: 2417
Re: Thought experiment... ultra long range travel
« Reply #34 on: 16 July 2019, 11:18:41 »
Calculation gets a bit more complicated when one takes it not as 2.5 tons per person but "one 50-ton module for every 20 people, round up" - which isn't that uncommon a way to phrase a rule in BT after all.

Algaeculture in space sounds nice, but water on spacecraft is always an iffy thing - you really don't want that to get anywhere, necessitating rather heavy and cumbersome redundant enclosures. It's the main reason why the German Space Agency isn't growing its space tomatoes with a (rather wet) euglena-based urine recycling system on ISS for example, but on its own separate satellite.

idea weenie

  • Major
  • *
  • Posts: 4855
Re: Thought experiment... ultra long range travel
« Reply #35 on: 16 July 2019, 19:24:19 »
Calculation gets a bit more complicated when one takes it not as 2.5 tons per person but "one 50-ton module for every 20 people, round up" - which isn't that uncommon a way to phrase a rule in BT after all.

True, I was figuring that people would try to optimize for it so they would have as close to a multiple of 20 people as practical.

For example, the Caveman ship would need to support its current crew of 20, and need 50 tons of hydroponics
Daryk's ship would keep enough for all 120 people, using 300 tons of cargo.  This drops consumables to 4830 tons, but those consumables will last 2,415,000 man-days, for 120 people will be ~20,000 days, or ~55 years.
Giovanni's first design would need to support 315 people, so would need 800 tons of hydroponics.  Giovanni's second design would need to support 319 people, so would also need the 800 tons of hydroponics.

Algaeculture in space sounds nice, but water on spacecraft is always an iffy thing - you really don't want that to get anywhere, necessitating rather heavy and cumbersome redundant enclosures. It's the main reason why the German Space Agency isn't growing its space tomatoes with a (rather wet) euglena-based urine recycling system on ISS for example, but on its own separate satellite.

BT Dropships handle liquid hydrogen on board, a fusion power plant, plus the associated plumbing that lets everyone keep going whether under thrust or not.  I figured compared to that algae in tubes would be fairly simple to handle.  If not, some sort of basic plant to provide nutrition would be used, and the crew would soon be grumpy if that was all they had to eat

kato

  • Captain
  • *
  • Posts: 2417
Re: Thought experiment... ultra long range travel
« Reply #36 on: 17 July 2019, 07:39:07 »
No real need for plant paste or eating algae.

To feed 20 people we only need about 9 tons of edible biomass per year - and that's the equivalent of two harvests per year on 7500 m², with bog-standard "normal" farming. Coincidentally those 7500 m² actually pretty closely match art for the Invader's domes when you measure proportions in those.

It gets a bit iffy when accounting for mass, since we only have about 5.5 kg per m² remaining. Sufficient for lightweight supports (even without taking BT space magic armor into account), but for growth medium we'd likely be talking something like wet cotton or similar lightweight substrate rather than soil.

The_Caveman

  • Lieutenant
  • *
  • Posts: 1246
  • A Living Fossil
Re: Thought experiment... ultra long range travel
« Reply #37 on: 17 July 2019, 15:57:03 »
Fears about water damage from gardens are rather overblown IMO. For one, BT spacecraft don't spend much time in actual zero-g, even stationkeeping thrust is close to lunar gravity. Second, it's easier to manage liquids and particles in a microgravity environment than you'd think. You mostly need good ventilation and air currents will take care of the rest. BT spacecraft also aren't the jungles of exposed wiring and computer boards that our impossibly primitive present-day spacecraft are.

Considering you can get quite a bit more than two traditional harvests a year out of high-intensity hydroponics, you should accordingly need a lot less surface area as well, which helps beef up the density of the grow boxes. The Invader, with its two large domes, is probably devoting a lot more than 50 tons to its garden facilities anyway. They explicitly produce enough for a surplus to be sold to other ships.
Half the fun of BattleTech is the mental gymnastics required to scientifically rationalize design choices made decades ago entirely based on the Rule of Cool.

The other half is a first-turn AC/2 shot TAC to your gyro that causes your Atlas to fall and smash its own cockpit... wait, I said fun didn't I?

Maingunnery

  • Lieutenant Colonel
  • *
  • Posts: 7155
  • Pirates and C3 masters are on the hitlist
Re: Thought experiment... ultra long range travel
« Reply #38 on: 17 July 2019, 16:05:43 »

I expect that any future space crops will be genetically engineered to rapidly grow in zero/low-G environments, like jungle growth rates or higher.
Herb: "Well, now I guess we'll HAVE to print it. Sounds almost like the apocalypse I've been working for...."

The Society:Fan XTRO & Field Manual
Nebula California: HyperTube Xtreme
Nebula Confederation Ships

Daryk

  • Lieutenant General
  • *
  • Posts: 37059
  • The Double Deuce II/II-σ
Re: Thought experiment... ultra long range travel
« Reply #39 on: 17 July 2019, 16:40:56 »
As long as they don't hit kudzu rates, the ship will survive...

kato

  • Captain
  • *
  • Posts: 2417
Re: Thought experiment... ultra long range travel
« Reply #40 on: 19 July 2019, 08:08:31 »
The Invader, with its two large domes, is probably devoting a lot more than 50 tons to its garden facilities anyway. They explicitly produce enough for a surplus to be sold to other ships.
With those 50 tons you can sell off 40% of your harvest after feeding everyone onboard.

Daryk

  • Lieutenant General
  • *
  • Posts: 37059
  • The Double Deuce II/II-σ
Re: Thought experiment... ultra long range travel
« Reply #41 on: 19 July 2019, 15:41:21 »
To buy meat, of course...  ^-^

idea weenie

  • Major
  • *
  • Posts: 4855
Re: Thought experiment... ultra long range travel
« Reply #42 on: 20 July 2019, 22:45:14 »
To buy meat, of course...  ^-^

And get paid for dealing with other ships' sewage, so you don't run out of biomass on board?

Thunderbolt

  • Master Sergeant
  • *
  • Posts: 279
  • ex scientia, ad astra
Re: Thought experiment... ultra long range travel
« Reply #43 on: 15 September 2019, 01:30:26 »
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...
Isn't the standard op to burn for a few hours onto a polar orbit, and coast the rest of the time?  If so, you'd only need a few hours of station keeping fuel over each star

"Hovering" is the obvious option, however powering onto a polar orbit is a very clever fuel saver

For K/G/F spectral classes of stars, the standard proximity point would have at least a 2 year = 720 day orbital period, only half a degree per day, or a few degrees of arc while you're recharging your drive

In terms of metric distance covered, would be at most about 10 km/s x 500,000s = 5M km (for K class star PP, where you're at the distance of Mars from the Sun, but only circling a 0.5Msun star, so the orbital speed v2/D = GM*/D2 --> v2 = GM*/D decreases by the sqrt(2) from Mars' 15 km/s to about 10 km/s)





So apparently you can be off by a few M km (and even in motion w.r.t. the central star at up to 10 km/s) without endangering your HS transit, allows JS to disperse & spread out from the PP jump harbor region far enough apart to unfurl sails, charge & jump out without affecting each other

One potential issue is that stars move relative to each other at about the same rates ~10 km/s, so your distance tolerance translates into about 1 week or so of relative stellar motion

But if you're jumping blindly into uncharted remote systems 30 lyr = 1500 weeks distant, very plausibly you're well beyond jump tolerances

So might have to account for observation time after each jump, charting & evaluating proximate stars, determining relative motions and estimating actual true present space locations so as not to misjump

So, if you can save fuel by getting onto polar orbits around the central star, then perhaps you could convert your fuel DS into an observatory DS ?  Your HS calculations have to be quite accurate

kato

  • Captain
  • *
  • Posts: 2417
Re: Thought experiment... ultra long range travel
« Reply #44 on: 15 September 2019, 02:07:31 »
Isn't the standard op to burn for a few hours onto a polar orbit, and coast the rest of the time?  If so, you'd only need a few hours of station keeping fuel over each star
At 10 AU from a G2V star you need about 9.4 km/s delta-v to achieve orbit from a relative-zero velocity. This delta-v is equivalent to constant thrusting against the star's gravitational pull at the same distance over a timeframe of about 440 hours - or 2.5 recharge periods. Unless you plan to stay around it is therefore more fuel-efficient to "hover".

Of course technically you don't need stationkeeping at all if you're just hopping by to catch some sunrays. Just jump in a bit further out and let the star drag you in to save fuel. Even just one AU would be enough for a G2V to still be well outside the safe jump limit after one recharge period.

Thunderbolt

  • Master Sergeant
  • *
  • Posts: 279
  • ex scientia, ad astra
Re: Thought experiment... ultra long range travel
« Reply #45 on: 15 September 2019, 03:31:55 »
At 10 AU from a G2V star you need about 9.4 km/s delta-v to achieve orbit from a relative-zero velocity. This delta-v is equivalent to constant thrusting against the star's gravitational pull at the same distance over a timeframe of about 440 hours - or 2.5 recharge periods. Unless you plan to stay around it is therefore more fuel-efficient to "hover".

Of course technically you don't need stationkeeping at all if you're just hopping by to catch some sunrays. Just jump in a bit further out and let the star drag you in to save fuel. Even just one AU would be enough for a G2V to still be well outside the safe jump limit after one recharge period.
+1 m/s/s
x
10,000 s
=
+10 km/s

aka 3 hours ?

As for free falling, the acceleration of gravity at 10 AU from a G2V star would be around...

(1/2000)2 * 274 ~ 280 / 4e6 = 7e-5 m/s2 = 0.7 micro Gs

even after a million seconds (most of a fortnight) that's still...

d = 1/2 a t2 ~ 3e-5 e12 = 3e7 m = 3e4 km = 30,000 km

v = a t = 7e-5 e6 = 70 m/s

so IDK why you couldn't just free fall for a week, sliding down in towards the star by a few planetary widths, and accelerating up to, what, half of one AT2 MP ?

IDK why you would necessarily have to bother trying for any delta-v at all, other than perhaps wanting to "disperse laterally" sideways away from the proximity point jump harbor to make room for yourself and future arrivals