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Power Crazy!
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How time flies! It's already been a year since yours truly launched this little vanity site, and six months since I last found time to update it. Based on that track record, I shouldn't make any rash promises, but let's see if we can't make things a little livelier around here. To start the ball rolling, here's a discussion of one of the more obscure technical issues regarding the mighty mobile suits that populate the world of Gundam's Universal Century.

The basic power source of a mobile suit is the ultra-compact thermonuclear reactor. Fueled by isotopes of hydrogen and helium, this reactor provides the mobile suit with an abundant supply of fusion energy. But how is this energy converted into electrical power, propulsion, and the exotic particles used in the Gundam world's devastating beam weapons? And how is this energy transmitted around the mobile suit's body? Thanks to recent advances in the field of Gundam documentation (1), we can now begin to answer these questions...

Artist's impression of the internal construction of the RX-78 Gundam. Only the core block, chest and waist cooling vents, and leg mechanisms are depicted here. The generator block and propellant tanks have been removed from the left leg to show the connectors beneath.

First, we have the matter of electricity. In addition to avionics and life support systems, electrical power is required to run the actuators and motors that move the mobile suit's joints. Beam weapons also have huge power requirements, and the mobile suit's electrical output appears to be the crucial factor that determines whether it can support these weapons (2).

There are two methods by which electricity can be obtained from a thermonuclear reactor. The primary one is magnetohydrodynamics (MHD) (3), which allows electrical current to be obtained directly from the swirling plasma in the reactor core. Additional power can be obtained by transferring the immense heat - or thermal energy, in technical terms - produced by the reactor to a fluid or gaseous medium, which is then circulated through a turbine.

Consider the famous RX-78 Gundam. The Gundam has a pair of thermonuclear reactors installed in its core block, which also serve as engines when this central block unfolds into an independent Core Fighter. When the core block is connected to the Gundam's body, the reactors' thermal energy is transferred by high-pressure gas to chambers in the Gundam's waist and legs, where it can be used for supplemental power generation (4).

Although the Gundam is equipped with the same reactors as the mass-produced RGM-79 GM, the supplemental generator devices or "sub-generators" in its lower body allow it to extract additional electricity from the reactor heat, giving it a higher overall power output. The standard version of the GM lacks this hardware, but it too can be equipped with sub-generators to create custom versions with higher output (5).

The following table lists the various generator devices installed in the Gundam.

Device NC-3 (x2) NC-5 (x2) NC-7S NC-3M (x2)
Location Core block Backpack Pelvis Legs
Function Main reactors Beam saber
energy supply
Sub-generator Sub-generators (6)

The classic MS-06 Zaku II. In the author's opinion, its trademark power cables are most likely used to transfer thermal energy for propulsion, electrical generation, and cooling purposes. This theory is, however, at odds with the official explanation (10).

A similar mechanism is used for propulsion. Instead of traditional chemical rockets, mobile suits are equipped with nuclear thermal rocket engines, in which propellant is heated by the reactor and then expelled to create thrust. These devices provide substantially greater fuel efficiency than chemical rocket engines (7), allowing the mobile suit to operate for longer periods and reach higher velocities in space. The same concept can be employed to create nuclear thermal jets and nuclear thermal hydrojets, which employ air and water, respectively, as propellants.

Since thermal energy from the reactor is used to generate both electrical power and rocket thrust, these two applications are competing for the same resource. In theory the allocation of this energy can be shifted back and forth depending on the needs of the moment, but in practice, mobile suits which are designed for high-speed combat often forgo the use of electricity-hungry beam weapons, or use external generators to power their weapons.

When this heat isn't being used for either purpose, it has to be disposed of via radiators or ventilation ducts to prevent the mobile suit from overheating. Since electrical generation, propulsion, and cooling all involve extracting thermal energy from the reactor and transferring it to other parts of the mobile suit's body, why not use the same mechanism for all three? The author imagines a network of thermal energy conduits running throughout the mobile suit's body, transferring reactor heat via high-pressure helium gas (8). This provides a handy explanation for the cables and tubes that decorate the exteriors of our favorite mobile suits (9).

The RX-78NT1 Alex. This radically redesigned version of the Gundam pioneered a number of new technologies, which were to be widely adopted after the end of the One Year War.

However, this doesn't account for all of the cables. Mobile suits also need to transmit beam energy, in the form of Minovsky particles, to their weapons. The Gundam's beam rifle and beam saber both contain energy capacitors, which store the high-energy Minovsky particles used to form their devastating beams (11). But where the beam rifle's energy supply is self-contained, the beam sabers obtain their energy directly from the mobile suit, and must be plugged into sockets in the Gundam's backpack in order to recharge. When the Gundam uses its sabers for an extended period, they can actually run out of energy in mid-battle (12).

This design flaw is addressed in the RX-78NT1 Gundam "Alex," whose beam sabers can receive their energy either from the backpack sockets or via the mobile suit's manipulator hands (13). Likewise, the arms of the Principality's MS-14 Gelgoog have internal conduits to supply energy to its beam weapons (14). Similar energy conduits, both internal and external, can be seen in later mobile suits such as the RMS-106 Hizack.


(1) Primarily the detailed instruction manuals that accompany Bandai's Master Grade model kits, and the Gundam Museum that opened in 2003 in the Tokyo suburb of Matsudo. Your author assisted with the English translations of the Gundam Museum's display placards and souvenir booklet, which proved very illuminating.

(2) Examples from the original Mobile Suit Gundam series include the MS-R09 Rick Dom (output 1199 kW), which can't use beam weapons at all, and the RGM-79 GM (output 1250 kW) which can support a beam saber or a short-range beam spray gun, but not the full-fledged beam rifle used by the RX-78 Gundam (output 1380 kw).

(3) The displays in the Gundam Museum state that MHD is the primary means of electrical generation.

(4) The Gundam Museum claims that this gas is emitted from the Core Fighter's engines nozzles and collected in the Gundam's waist.

(5) As per the Master Grade GM kit manual. This suggests that the GM retains the Gundam's thermal energy distribution mechanism, and lacks only the sub-generator units themselves.

(6) The Master Grade Gundam kit manual claims that these devices are independent generators, but I've classified them as sub-generators based on the Gundam Museum's explanation.

(7) The efficiency, or "specific impulse," of a solid-core nuclear thermal rocket is estimated at about 900 seconds, versus 300-450 seconds for a chemical rocket engine.

(8) Entertainment Bible 1: One Year War Picture Encyclopedia identifies helium as the coolant used in the MS-06 Zaku II. Since this is also a suitable medium for transferring reactor heat to generator turbines, and its relatively low molecular weight makes it an efficient propellant for thermonuclear rocket engines, it seems like a good candidate for all three applications. Plus, this would explain the significance of the mysterious "helium control cores" attached to the Gundam's skirt armor!

(9) For example, the Master Grade GM Custom kit manual explains that the cables that run down the back of the mobile suit's legs supply energy to its leg thrusters.

(10) The official explanation for the Zaku II's cables is that they transmit hydraulic power to actuators in the mobile suit's joints. This always struck me as absurd, for why would the Zaku need to transmit hydraulic power from its belly to its backback, or from its muzzle to the back of its head? Likewise, early mobile suits like the Zaku II and the Gundam are usually said to use traditional chemical rocket engines, but this seems to defeat the purpose of having a thermonuclear reactor in the first place.

(11) In the case of the beam rifle, electrical power from the mobile suit's generators is used to convert the stored Minovsky particles into massive, fast-moving mega particles prior to firing.

(12) As is comically demonstrated in Mobile Suit Gundam episode 22 - episode 21 in the U.S. release.

(13) This "dual supply device" is described in the Master Grade GM Custom kit manual, which also claims that the GM Custom's arm construction is essentially identical to that of the Alex. Thus, though it's not explicitly stated in the Master Grade Alex kit manual, it seems reasonable to assume that the same energy supply conduits must be present in the Alex as well.

(14) As per the Master Grade Char's Gelgoog kit manual.