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by Lewis Taylor Goss

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Jump Drives in Classic Traveller (CT) (1977 Far Futures Enterprises), MegaTraveller (MT) (1987, Far Futures Enterprises), and Marc Miller's Traveller (T4) (1996, Far Futures Enterprises) are used to transport starships vast distances in relatively short amounts of time.  The amount of energy required to jump increases with the volume of the jumping vessel and the number of parsecs the ship is jumping.  The process of jumping is essentially instantaneous, but it takes time to generate the enourmous amount of energy required.

The energy is generated by a High-Yield Power Plant (HYPP)[1], and stored in Energy Sinks (Capacitors) until the ship is ready to jump, a process that can take from a few minutes to a few hours depending on the size of the vessel, power output of the HYPP, etc. The ship is only able to maintain a life-sustaining environment in Jumpspace because of its Hull Grid[2]. When the ship is ready to jump, the Hull Grid is energized by small injections of energy from the Energy Sinks. About 20% of the energy required to jump is used in this way[3]. Once the Hull Grid is energized, the remaining energy is rapidly injected into the Lanthanum Jump Coil, and the ship enters Jumpspace a fraction of a second later.

A dedicated high-speed computer system called a Jump Governor regulates the operation of the HYPP, the transfer of power from the HYPP to the Energy Sinks, and thence to the Lanthanum Jump Coil. The power consumption of the Jump Governor is proportional to the power output of the HYPP.

The standard unit of volume in this set of rules is the kiloliters, or cubic meter. One displacement ton is assumed to equal 13.5 kiloliters in Classic Traveller and MegaTraveller, 14 kiloliters in T4. Not to be confused with the metric tonne(=1000kg), which is a unit of mass.

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Hull Grid

A grid of wires implanted in the outer layer of the ship's hull, spaced at about one meter intervals. The ship is only able to maintain a life-sustaining environment in Jumpspace because of its Hull Grid[4]. For design purposes, the Hull Grid is assumed to occupy no volume, have no mass, and require no surface area. Installation of the Hull Grid does not alter the hull armor rating. The price of the Hull Grid is per kiloliter of total ship volume[5].

Hull Configuration CT
Price(Cr/kl)
MT
Price(Cr/kl)
T4
Price(Cr/kl)
Open Frame - 330 1,500
Needle/Wedge 1,200 264 1,200
Cone 1,100 242 -
Cylinder 1,000 220 1,000
Close Structure 1,300 - 1,300
Box - 286 1,300
Sphere 700 154 700
Flattened Sphere 800 - -
Dome/Disk - 176 800
Slab - - 1,400
Dispersed Structure 1,500 - -
Irregular - 330 -

e.g. a 2,800 kiloliter vessel with a Cylinder Configuration has a Hull Grid installed. It costs Cr1,000 / 220 2,800 = MCr2.8 / 0.616.

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Jump Energy Requirements

There are are two components to the energy requirement: a portion to energize the Lanthanum Jump Coil, and a portion to power the Lanthanum Jump Coil.

To energize the Hull Grid 0.65 MW-hr n ship vol (kl)
To power the Lanthanum Jump Coil 2.60 MW-hr n ship vol(kl)
Total Energy Needed 3.25 MW-hr n ship vol(kl)

E = energy required to jump in MW-hr
n = the number of parsecs the ship is jumping.

e.g. the energy required for a 2,800 vessel jump 2 parsecs is 3.25 MW-hr 2 2,800 = 18,200 MW-hr. A 1 parsec jump requires 9,100 MW-hr.

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Lanthanum Jump Coil

The heart of a jump drive. A coil of Lanthanum, through which massive amounts of energy flow when a ship enters Jumpspace.

TL Min Vol
(kl)
Mass
(tonne/kl)
Price
(MCr/kl)
Surf Area
(m2/kl)
Max.
Jump
9 3.375 2 0.2 1.05 1
10 3.375 2 0.2 1.05 1
11 3.375 2 0.2 1.05 2
12 3.375 2 0.2 1.05 3
13 3.375 2 0.2 0.90 4
14 3.375 2 0.2 0.90 5
15 3.375 2 0.2 0.45 6
16 3.375 2 0.2 0.30 6

L = V / 400

L = volume of Lanthanum Jump Coil in kiloliters
V = total volume of ship in kiloliters

e.g. a 2,800 kl vessel has a Lanthanum Jump Coil of 2,800 / 400 = 7 kiloliters. It weighs 14 tonnes, costs MCr1.4, and requires 3.15 m2 of surface area.

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Energy Sinks (Capacitors)

These accumulate the power produced by the High-Yield Power Plant, to later release it rapidly into the Hull Grid and Lanthanum Jump Coil during jump. It is also possible to install Energy Sinks for use with a Black Globe.

TL CT&T4
Mass(t/kl)
MT
Mass(t/kl)
Price[6]
(MCr/kl)
Energy Stored[7]
(MW-hr/kl)
9 3.0 1 0.3 650
10 3.0 1 0.3 650
11 3.0 1 0.3 650
12 3.0 1 0.3 650
13 3.0 1 0.3 650
14 2.0 1 0.3 650
15 1.0 1 0.3 650
16 0.5 1 0.3 650

The volume of Energy Sinks required can be computed as follows:

V = E / 650

V = volume of Energy Sinks in kiloliters.
E = energy you wish the Energy Sinks to be able to store in MW-hr.

e.g. the Energy Sinks required to store 18,200 MW-hr have a volume of 18,200 / 650 = 28 kiloliters, weigh 28 tonnes at TL 15, and cost MCr8.4.

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High-Yield Power Plant

A High-Yield Power Plant has been tuned for maximum power production, at the expense of inefficient fuel use. Power Out, Mass, and Price are per kiloliter of power plant[8]. Fuel is kiloliters of fuel per kiloliter of power plant per hour.

TL Description Power Out
(MW/kl)
Fuel
(klf/klpp/hr)
Mass
(tonne/kl)
Price
(MCr/kl)
Min Vol
(kl)
Surf Area
(m2/kl)
9 Fusion 1,733.3 26.7 4 0.2 10.00 0.10
10 Fusion 1,733.3 26.7 4 0.2 2.00 0.10
11 Fusion 1,733.3 26.7 4 0.2 1.00 0.10
12 Fusion 1,733.3 26.7 4 0.2 0.25 0.10
13 Fusion 2,600.0 40.0 3 0.2 0.15 0.15
14 Fusion 2,600.0 40.0 3 0.2 0.10 0.15
15 Fusion 5,200.0 80.0 2 0.2 0.09 0.30
16 Fusion 6,066.6 93.3 1 0.2 0.08 0.35

e.g. at TL-15 a HYPP that is to produce 109,200 MW must have a volume of 21 kiloliters, weigh 42 tonnes, costs MCr4.2, and requires 6.3 m2 of surface area.

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Jump Governor

A dedicated computer system and accompanying connections. The governor finely regulates the transfer of power from the High-Yield Power Plant to the Energy Sinks, and thence to the Hull Grid and Lanthanum Jump Coil[9]. The volume of the Jump Governor must be equal to the volume of the installed Energy Sinks. In In Classic Traveller & T4, a Jump Governor consumes a constant amount of power, no matter how many parsecs the ship is jumping. In MegaTraveller, Jump Governors consume less power when jumping a larger number of parsecs.

Component Mass
(tonne/kl)
CT&T4
Price(MCr/kl)
MT
Price(MCr/kl)
Surf Area
(m2/kl)
Jump Governor 3 0.3 0.145 0.6666

e.g. a ship with 28 kiloliters of Energy Sinks must have a Jump Governor that has a volume of 28 kiloliters, weighs 84 tonnes, costs MCr8.4/4.06, and requires 18.66 m2 of surface area.

The power consumption of the Jump Governor can be computed as follows:

Classic Trav & T4 MegaTraveller
P = O / 2 P = O / (1 + n)

P = power consumption of the Jump Governor in MW.
O = power output of High-Yield Power Plant in MW.
n = the number of parsecs the ship is jumping.

e.g. the power consumption of a Jump Governor on a High-Yield Power Plant that puts out 105,300 MW is

Jump Classic Trav & T4 MegaTraveller
1 54,600 MW 54,600 MW
2 54,600 MW 36,400 MW

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Time to charge Jump Energy Sinks

The process of jumping is essentially instantaneous. Therefore, the primary limitation on how rapidly one may jump is the time required to charge up the Energy Sinks. Should this time exceed two or three hours, the Energy Sinks may suffer severe damage, initiating a process which concludes in the destruction of the ship. The time to charge Energy Sinks may be computed as follows:

T = E 60 / (O - P)

T = time to charge Energy Sinks in minutes.
E = energy required to jump in MW-hr.
P = power consumption of the Jump Governor in MW.
O = power output of High-Yield Power Plant in MW.

e.g. if the energy required to jump is 18,200 MW-hr, the HYPP produces 109,200 MW, and the Jump Governor consumes 54,600 MW, then the time to charge Energy Sinks is 18,200 60 / 54,600 = 20 min.

e.g. if the energy required to jump is 18,200 MW-hr, the HYPP produces 109,200 MW, and the Jump Governor consumes 36,400 MW, then the time to charge Energy Sinks is 18,200 60 / 72,800 = 15 min.

e.g. if the energy required to jump is 9,105 MW-hr, the HYPP produces 109,200 MW, and the Jump Governor consumes 54,600 MW, then the time to charge Energy Sinks is 9,100 60 / 54,600 = 10 min.

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Jump Fuel Required

All of the fuel consumed by the jump drive is consumed by the High-Yield Power Plant while charging the Energy Sinks. Once the vessel has entered Jumpspace, no more fuel is consumed by the jump drive. The amount of fuel consumed may be computed as follows:

F = V R T / 60

F = volume of Jump Fuel consumed in kiloliters.
V = volume of High-Yield Power Plant in kiloliters.
T = time to charge Energy Sinks in minutes.
R = kiloliters of fuel used per kiloliter of power plant per hour.

e.g. if a TL 15 HYPP has a volume of 21 kl, and the time required to charge Energy Sinks is 20 min, then the jump fuel consumed is 21 80 20 / 60 = 560 kl.

e.g. if a TL 15 HYPP has a volume of 21 kl, and the time required to charge Energy Sinks is 15 min, then the jump fuel consumed is 21 80 15 / 60 = 420 kl.

e.g. if a TL 15 HYPP has a volume of 21 kl, and the time required to charge Energy Sinks is 10 min, then the jump fuel consumed is 21 80 10 / 60 = 280 kl.

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Maintaining Jump

When in Jumpspace, the Hull Grid needs to be powered from the ship's main power plant. The power required to maintain the Jump Field is

P = V / 75

P = power required to maintain Jump Fiel in MW.
V = volume of ship in kiloliters

e.g. 2,800 kiloliter vessel requires 37.33 MW to maintain its Jump Field.

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Example #1: TL 15 J-2 Drive for Cylinder 2,800 kl ship (Standard Design)

CT & T4 MT
Hull Grid - - MCr 2.8 MCr 0.616 -
Lanthanum Jump Coil 7 kl 14 tonnes MCr 1.4 MCr 1.400 3.15 m2
Energy Sinks 28 kl 28 tonnes MCr 8.4 MCr 8.400 - 18,200 MW-hr
High-Yield Power Plant 21 kl 42 tonnes MCr 4.2 MCr 4.200 6.30 m2 109,200 MW
Jump Governor 28 kl 84 tonnes MCr 8.4 MCr 4.060 18.66 m2
Total 84 kl 168 tonnes MCr25.2 MCr18.676 28.12 m2
Jump Jump Energy
(MW-hr)
Governor Power
(MW)
Time
(min)
Fuel
(kl)
Comment
1 9,100 54,600 10 280 -
2 18,200 36,400 15 420 MegaTraveller
2 18,200 54,600 20 560 Classic Trav & T4

Except for minor changes in the price of the Jump Drive, this is the same as one gets as using the Jump Drive tables in Book 5: High Guard (1980, Far Futures Enterprises), the MegaTraveller Referee's Manual (1987, Far Futures Enterprises), or Starships (1996 Far Futures Enterprises).

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Base Time to Charge Jump Energy Sinks for Standard Designs

In order to determine the time to charge Energy Sinks for standard Jump Drive designs (i.e. identical to the result of High Guard, the MT Ref's Manual, or Starships, the following chart and formula will be useful:

TL T0
min
9 15.0
10 15.0
11 15.0
12 15.0
13 10.0
14 10.0
15 5.0
16 4.3
Classic Trav & T4 MegaTraveller
T = 2 n T0 T = (1 + n) T0

T = time to charge Energy Sinks for standard Jump Drive designs
T0 = base time to charge Energy Sinks for standard Jump Drive designs
n = the number of parsecs the ship is jumping.

e.g. the time to charge Energy Sinks for a TL 15 ship with a standard Jump-2 drive is

Jump Classic Trav & T4 MegaTraveller
1 10 min 10 min
2 20 min 15 min

Example #2: TL 15 J-2 Drive for Cylinder 2,800 kl ship (Variant Design)

CT & T4 MT
Hull Grid - - MCr 2.8 MCr0.616 -
Lanthanum Jump Coil 7 kl 14 tonnes MCr 2.1 MCr 2.100 3.15 m2
Energy Sinks 28 kl 21 tonnes MCr 8.4 MCr 8.400 - 18,200 MW-hr
High-Yield Power Plant 7 kl 14 tonnes MCr 1.4 MCr 1.400 2.10 m2 36,400 MW
Jump Governor 28 kl 84 tonnes MCr 8.4 MCr 4.060 18.66 m2
Total 70 kl 140 tonnes MCr23.1 MCr16.576 23.92 m2
Jump Jump Energy
(MW-hr)
Governor Power
(MW)
Time
(min)
Fuel
(kl)
Comment
1 9,100 18,200 30 280 -
2 18,200 12,133 45 420 MegaTraveller
2 18,200 18,200 60 560 Classic Trav & T4

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Designer's Notes

[1]Miller, Marc W. "Jumpspace." the Journal of the Travellers' Aid Society 24 (1985): pp. 34-38.
[2] see [1].
[3] Digest Group Publications. Starship Operator's Manual. 2nd ed. 1988, p. 13.
[4] see [1].
[5] the idea that the price of the Hull Grid should depend on the Hull Configuration is originally due to Danny M. Moody, TML nightly, December 6, 1993, vol. 65, #7. (msg 6425). Actual prices are due to me.
[6] Miller, Marc W., et al. Book 5: High Guard. Game Designers' Workshop, 1980, p. 31.
[7] Miller, Marc W., et al. MegaTraveller Referee's Manual. Game Designers' Workshop, 1987, p. 95.
[8] see [6], p. 64.
[9] see [3].

If you have comments or suggestions, email me at ltgoss@d0tam3.tamu.edu

This article written and submitted by Lewis Taylor Goss, 1996