Sloth Transport Station

[Lagrange]

The best of many hyperspace navigation plans by control roll 5 navigators for L1 jump points has a maximum margin of success of 1 which implies a 1-in-12  risk of KF drive damage in such jumps.  KF drive damage is terrible for logistics, because it increases the odds of further damage and requires a difficult (+5 modifier) repair that takes 10 days according to Combat Operations. 

On the other hand, a single control roll 5 navigator who steadily toils away on Zenith/Nadir solutions for 44 hours over 7.5 days between jumps can potentially choose the best solution, reducing the odds of KF damage to less than 1-in-1000.  Adding an extra navigator who cross checks and works similarly, the odds fall to 1-in-10⁶ which is small enough to not really matter.  Given this, the use of standard Zenith/Nadir transport works fine.  This creates a question: What is the cheapest mechanism for bulk transport between Zenith/Nadir and other planetary locations? 

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Sloth Station
Mass: 99,000 tons
Technology Base: Inner Sphere (Advanced)
Introduced: 3025
Mass: 99,000
Battle Value: 1,064
Tech Rating/Availability: D/X-D-C-C
Cost: 38,030,000 C-bills

Fuel: 250 tons (2,500)
Safe Thrust: 0
Maximum Thrust: 0
Sail Integrity: N/A
Heat Sinks: 93
Structural Integrity: 1

Armor
    Nose: 10
    Fore Sides: 10/10
    Aft Sides: 10/10
    Aft: 10

Cargo
    Bay 1:  Small Craft (72)        9 Doors   
    Bay 2:  Cargo (80421.0 tons)    1 Door   

Ammunition:
None

Dropship Capacity: 1
Grav Decks: 0
Escape Pods: 6
Life Boats: 6
Crew:  11 officers, 54 enlisted/non-rated, 360 bay personnel

Notes: Mounts 75 tons of standard aerospace armor.

Weapons:     Capital Attack Values (Standard)
Arc (Heat) Heat  SRV     MRV     LRV      ERV    Class       
None

The Sloth Transport Station should be thought of as something like ocean shipping.  It's 1/10th the price of a Cavern Dropship, but it requires a longer transit.   Due to the quadratic relationship between time and distance at a fixed acceleration, the 1/10th g drive implies only a factor of 10^0.5~=3.16 time is required, so the standard 1g 9.1 day transit from Earth's Zenith/Nadir to Earth becomes a bit less than 29 days.  This syncs up nicely with the 7.5 day jump cycle implying a full cycle of transport happens every 8 jumps. 

A wide range of cost vs. transport enables both poor and rich systems to benefit from a jump circuit. A poor system might be serviced by one Sloth every 60 days (cost 42M) and a few Skybus (6.7M each).  A moderately wealthy system could be serviced by 8 Sloths with a new one arriving every 7.5 days (cost 336M) plus 72 Skybus smallcraft (482M).  A very wealthy system could be serviced similarly by 3 Caverns operating in a Behemoth mode (cost 1299M but only 9.1 day transit) plus 72 Skybus smallcraft (482M). 

Given the usage mode of the Sloth the transport bays are empty most of the time with planet-based Skybus on one end and a jump circuit based Spacebus on the other end.  Although the Sloth is not militarized, it is of course possible to transport ASF which could form a nasty surprise for any would-be pirate.  Since the Sloth itself is not heavily armored, alternate means of reaching planetary orbit like long range smallcraft are recommended.

The Sloth has a few unusual design elements.  It features 4 smaller engines in a Mammoth style although about a factor of 8 smaller.  These engine swivel 90 degrees off the aft axis allowing them to provide rotational acceleration and deceleration.  Thus, instead of a grav deck, the Sloth itself can spin up to provide a half g at the outer hull with an internal layout designed to support a down=out orientation and a barrel shape.  While spun up, only the aft docking collar and the forward smallcraft bay can function after docking or recovering craft match reference frames.   Of course for rapid (un)loading operations, the Sloth spins down so that every door can be used.  Nevertheless, during month-long transits the crew can enjoy a modest apparent gravity, better than a Scout for instance.

Since the Sloth is so cheap and efficient, it is also often used to service other interplanetary routes.

Tradeoffs

Tonnage  99k tons is convenient as something capable of taking and delivering the full load of the Cavern dropship.   You could easily go for a larger capacity, but that damages economical use by  basic colonies.  You could also go smaller, but since only 30% of the cost is related to size the gains from doing so are not that significant.

Smallcraft Bays The 72 smallcraft bays simply match the Cavern dropship to allow full speed (un)loading.  You could go larger, but since 38% of the cost is the smallcraft bays the expense is nontrivial.  You could also go smaller, but that would damage the ability to (un)load at full speed during a 2 hour window.

Grav Deck or not? A grav deck is quite expensive on a basic space station like this as even a small one increases the price by 60%.  The Scout jumpship is listed as using transit drive (.1g) to simulate gravity, which is typically in play for the Sloth by default.  There are no rules for spinning the entire station, but the discussion appears a logical consequence of SI 1 (limiting to a half g), and the relative ease with which a station could be spun whether by swiveling main engines (rapidly) or attitude thrusters (somewhat more slowly).

Zenith/Nadir or L1 jump points?  Sticking with a control roll of 5 seems to require the use of a Zenith/Nadir point.  However, with a Control roll of 3, it appears that jumps into and out of L1 jump points could be made routine at every other stop on a Jump Circuit.  The economic implications of that are massive, since transport to/from an L1 jump point is radically quicker.  For example, a single Sloth could ferry things back and forth between every jump and smallcraft could simply transit directly planet<->jumpship eliminating the need for any transport large craft associated with particularly small colonies.  A control roll of 2 goes even further, potentially allowing every jump to be to and from an L1 jump point.  ToW lists navigation/KF-drive as a simple basic skill suggesting that plotting a jump with a target number of 3 requires as much training as gunnery with a target number of 4.  Altogether, there is quite a bit of room for a society to particularly emphasize well-trained jump navigators, and benefit from doing so. 

Comments welcome.

Variants

The Way Station variant exists for jump circuit support.  Since individual stops on the jump circuit last 2 hours, a shift for cargo haulers lasts 4 stops.  Hence, every 4 stops, crews must rotate.  If L1 jump points are in use (via control roll 3 jump navigation), that can typically be on a planet.  Sometimes there may be no planet in a system, or the navigators may only be able to handle Zenith/Nadir jumps.  In those cases, the Way variant provides a place for up to 1600 crew to stay for the 7.5 days until the next hop on the jump circuit.

Since the Way Station is designed for deep space, it features a 245m full-g grav deck and quarters for everyone.  It also (somewhat controversially) features fairly heavy armor, under the reasoning that the Way Station is far from exterior support with a large number of people on board to protect.  Although it features no offensive weapons, aerospace fighters can be housed in the smallcraft bays, depending on the security situation.

All of this comes at considerable additional cost.  However, since a Way Station is needed only once every 4 stops, the cost is amortized down to being similar to the cost of a single Sloth station.

The variations from the Sloth are:

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Way Station
Battle Value: 5,474
Cost: 149,730,000 C-bills

Armor
    Nose: 52
    Fore Sides: 52/52
    Aft Sides: 52/52
    Aft: 52

Cargo
    Bay 1:  Small Craft (72)        9 Doors   
    Bay 2:  Cargo (67997.0 tons)    1 Door   

Grav Decks: 1 (245 m)
Escape Pods: 135
Life Boats: 135
Crew:  11 officers, 54 enlisted/non-rated, 360 bay personnel, 1600 passengers

Notes: Mounts 390 tons of standard aerospace armor.


[Daryk]

Your jump point argument aligns well with Cannonshop's fan fiction universe.

[Lagrange]

In that case, the calculation details.

With a control roll of 3 ("regular" equivalent training), you need a margin of success of 1 to avoid any chance of KF drive damage.  The desired roll is 10=3(base)+2(KF jump generally)+4(to L1 jump point)+1(MoS), so the odds of success are 1-in-6 (either 10,11, or 12).  The odds of failure are 5-in-6.  The time required is (2d6-MoS)*30 minutes allowing 12 attempts per jump cycle succeeding with probability 1-(5/6)^12 ~= .89.  That's not reliable enough, but adding 3 more astrogators it becomes 1-(5/6)^48 ~= .9998 which seems good enough.

With a control roll of 2 ("veteran" equivalent training), you need a margin of success of 0 to avoid any chance of KF drive damage.  The desired roll is 8 = 2(base)+2(KF Jump)+4(to L1), so the odds of success are 15-in-36.  Thus one astrogator doing 12 calculations has a probability of success of 1-(21/36)^12 ~= .0016.  That's not good enough, but 2 astrogators are sufficient.

At control roll 1 ("elite" equivalent training), a single astrogator is sufficient.

The above is for Zenith/Nadir <-> L1 jumps.   For L1<->L1 jumps an extra +2 penalty applies.  Thus, with a control roll of 2 (i.e. 1-in-6 chance of success), you need 4 astrogators, with a control roll of 1 (i.e. 10-in-36 success) 3 astrogators, and with a control roll of 0 (i.e. 15-in-36 success) just 2 astrogators.

[idea weenie]

This is why there needs to be a roll modifier for in-system observation, and for L1-component observation.

In-system would be where you are using a telescope to look at the two bodies creating the Pirate point, and using that data to plot numbers.  Instead of trying to guess the points from up to 30 ly away, you are looking at ~7 light-hours away (roughly Pluto's orbit).

L1-Component observation means your observation point is either located on or orbits one of the two bodies that makes up the pirate point.  I.e. a space station in orbit over Terra would be able to get a boost when calculating the Sol-Terra and Terra-Luna pirate points, but not when calculating the Sol-Mars pirate point.  You'd need some rule to say that the point has to be within a certain distance to get the bonus, to avoid someone putting a space station into orbit around Sol and arguing they can get bonuses for all the Sol-(planet) pirate points.


You then have a contract with Comstar or WoB so freighters can get from one system to another easily.  A freighter at one WoB-controlled system wants to go to another WoB-controlled system, and is willing to pay extra for PP calcs.  The Jumpship captain sends a message (with payment) requesting arrival coordinates for a certain time frame (tighter timeframe = higher fee).  The local HPG sends a message to the destination HPG, requesting up to date calcs for the time frame.  The receiving HPG calls up its calculations, selects one of them, and sends back the coordinates and timeframe the coordinates are good for.  The freighter can then proceed to the destination system's Pirate Point, cutting days off the transit time.  If no calcs were good, the Jumpship captain gets refunded.

The other option is that system A sends its list of Pirate point calculations to all systems nearby, and forces a fixed schedule on them.  This will reduce the efficiency, but it only requires regular daily HPG comms, rather than almost on-demand HPG comms.

(This Pirate Point network would also do wonders for rapidly moving troops around the WoB Protectorate.  An attacker has to spend 10 days transiting normally, and 1-2 days before they will land a cargo Dropship shows up with 3* their troop strength.)

[Daryk]

This is where my "Expanded TDS trait" comes in to play, making it possible for a single astrogator to "not fail" regularly.

[Lagrange]

Added the Way Station variant, which has a different role supporting crews every 4 (or potentially more) stops on the jump circuit.

[Lagrange]

Tweaked this for use in circuits with the Arc recharge station.   Due to the use of a recharge station, the required fuel quantity is greatly reduced, which makes the Sloth about 10% cheaper.