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Doomsday Machine

Size Comp
Universe : Prime Timeline
Affiliation :
Class Name : Doomsday Machine
Type : Robot weapon [1]
Unit Run : Only one vessel known to exist 1 built in total. 1 have been lost in all.
Commissioned : Unknown, but probably in excess of 30,000 years ago [1]
Dimensions : Length : 2,772 m [2]
Diameter : 607 m
Mass : Mass of hull estimated to be in excess of 427,000,000,000,000,000,000,000 metric tons. Entire mechanism capable consuming planetary masses.
Armament : 1 [1] x Pure antiproton beam [1]
Defence Systems :   Neutronium [1] Single [1] hull.
Warp Speeds
(TOS scale) :
Maximum Rated : 4 [1]
Strength Indices :
(Galaxy class = 1,000)
Beam Firepower : -
Torpedo Firepower : -
Weapon Range and Accuracy : -
Shield Strength : -
Hull Armour : 999,999.99
Speed : 33
Combat Manoeuvrability : -
Overall Strength Index : 68,285
Diplomatic Capability : None
Expected Hull Life : Indefinite [1]


The Doomsday device was first encountered by the USS Constellation in 2267. The ship found a number of solar systems in which all the planets had been almost totally destroyed. In system L 374 the Constellation discovered that a huge artificial device was destroying and consuming the planets. Commodore Decker engaged the machine, resulting in the wrecking of his ship.

Captain Kirk on the Enterprise responded to the distress call of the Constellation. The Enterprise crew determined that the device was a weapon from some ancient war, programmed to destroy planets and consume them as fuel for its total conversion drive. It was equipped with a weapon which fired a beam of absolutely pure antiprotons, which it used to cut up planets and a tractor beam with which it drew the debris inside. Its consumption rate appeared to be approximately one planet per day,  [1]
indicating a power usage in excess of some 1036 Watts - trillions of times greater than any Starship warp core could manage.

The device was equipped with a neutronium hull [1] which massed nearly a hundred times more than an M class planet. Although it had no shields, this hull rendered it invulnerable to conventional attack. As a final measure, the device generated a general dampening field which blocked subspace communications over a large area and at close range could deactivate the antimatter fuel of a Starship.

During the course of the battle Commodore Decker was killed when the machine swallowed his shuttlecraft. The explosion of the craft apparently inflicted a small amount of damage on the machine; Captain Kirk reasoned that a larger internal explosion might destroy it altogether, so he set the impulse engines of the Constellation on overload and piloted it into the machine. The resultant 97.835 Megaton explosion within the device destroyed its internal mechanism, rendering it permanently inert. [1]

Colour key

Canon source Backstage source Novel source DITL speculation


# Series Season Source Comment
1 TOS 2 The Doomsday Machine
2 Speculative Based on a comparison of the Machine to the Enterprise in 'The Doomsday Machine'.
Series : TOS Season 2
Episode : The Doomsday Machine
Source : Speculative
Comment : Based on a comparison of the Machine to the Enterprise in 'The Doomsday Machine'.


The Doomsday Machine was seen in the TOS episode of the same name. It's a fascinating concept, and the mathematics of it makes for an interesting thought exercise.

There are three possible sources of a length. Firstly, Commodore Decker describes the device as being "miles long", with a maw that could swallow dozens of Starships. However, when we later see it in close proximity to the USS Enterprise the maw scales to some 607 metres across, which makes the whole device 2,772 metres long - only 1.72 miles long.

Later, when Decker pilots a shuttle into the device, we see the shuttle in comparison to the maw. The shuttle looks about the same size as the Constitution class Enterprise had - making the device some forty times smaller than before!

Clearly the shuttle shot is an example of poor special effects. My general policy is that dialogue over-rides effects, which would make the "miles long" statement more important than the 2,772 metre length. However, in this case I've decided to go with the latter figure since Decker was in such an obviously overwrought state when he made the claim.

Some question how a device which is less than 3 km long could consume an entire planet, but in fact this is perfectly possible. We know that the builders had the technology to handle neutronium, and it's not too far a jump to believe that the planet killer compresses the material it eats into this material. The density of neutronium is about 3.16x1018 kg/m3, so an Earth type planet crushed to this density would occupy a volume of only about 2 million m3. Although it sounds a lot the Doomsday machine's internal volume is more than enough to accommodate this volume several dozen times over even at the conservative length, as we shall see shortly.

Looking at the views of the device's maw, we can calculate a thickness of the hull as 86 metres. Spock states that the hull is composed of solid neutronium, so this lets us calculate a mass for it.

First, the density of neutronium. There are various figures around for this, but a value of about 3.16x1018 kg/m3 seems the most common.

Second, the volume of the device itself. I will treat it as a conical shell of exterior diameter 607 metres, length 2772 metres and thickness 86 metres. Although the actual shape is somewhat irregular, a cone should give us a reasonable approximation. Firstly we work out the overall volume of the external cone as follows :

Vext = 1/3 [length x pi x r2]
Vext = 1/3 [2772 x 3.142 x 303.52]
Vext = 1/3 x 802,159,052
Vext = 267,386,351 m3

We now take off this the interior volume. Given the 86 metre hull thickness, I'm assuming this to be a cone of diameter 435 metres and length 1,986 metres. Repeating the above calculation with the new figures :

Vint = 1/3 [length x pi x r2]
Vint = 1/3 [1986 x 3.142 x 217.52]
Vint = 1/3 x 295,153,297
Vint = 98,384,432 m3

Note that as mentioned earlier this is more than sufficient to hold the 2 million m3 of neutronium which would result from the compression of an Earth sized planet. The total volume of the hull is given by Vext - Vint

V = 267,386,351 - 98,384,432 = 169,001,919 m3

Multiplying this by the density of neutronium given above, we get a total mass of 5.34x1026 Kg.

On the bare figures this is a pretty impressive mass - it's approximately one hundred times the mass of the Earth! However, this is only to be expected - the machine actually eats planets after all, so it's mass should be significantly larger than a single planet.

Next we have energy expenditure. It's power system is established in the episode to be some form of total conversion system, so if we know the rate at which it consumes mass then we can calculate power consumption. To give us a baseline figure I'm going to assume that the machine eats one planet per day. The mass of the Earth is about 6x1024 Kg, so we can calculate a value for this mass being converted entirely to energy

E = mc2
E = 6x1024 x (3x108)2
E = 6x1024 x 9x1016
E = 5.4x1041 Joules.

Used over one day, this equates to a power of 6.25x1036 Watts, which is about 1.6 times the total output of our own star.

There are factors that could push this figure up or down. To asses these, here is some dialogue from the opening scenes of the episode :

Sulu : "Sir, we're now within the limits of system L 370 but I can't seem to locate-"
Spock : "Captain. Sensors show this entire solar system has been destroyed. Nothing left but rubble and asteroids."
Kirk : "That's incredible. The star in this system is still intact. Only a nova could destroy like that."
Spock : "Nonetheless captain, sensors show nothing but debris where we charted seven planets last year."

Shortly afterwards...

Sulu : "Entering limits of system L 374 sir. Scanners show the same evidence of destruction."
Kirk : "Every solar system in this sector blasted to rubble. And still no sign of the Constellation. Matt Decker's in command what could have happened to him?"
Spock : "Captain the two innermost planets of this system appear to be intact."

Firstly, it's established that the machine does not consume the entire planet, but leaves some rubble behind. It's a matter of opinion what fraction of a planet could be left over and still count as rubble... personally I'd expect that no more than 25% of the planet would be left. This would still leave the device with a power generation capacity greater than that of our sun.

Secondly, and by far the most important, is the number of planets consumed and the time frame over which this consumption has happened. The Enterprise apparently visited five solar systems - L 370 to L 374 - and found total devastation in four of them and near total devastation in the fifth. Taking L 370's seven planets as the average per system, the machine would have destroyed some 33 planets. No time frame is given at this point, but the machine was eating the fourth planet when Decker found it, and it subsequently killed his crew by eating the third planet after he beamed his crew down to it. So the machine has consumed at least two planets since Decker first encountered it. It seems unlikely that Decker has been on his own for more than a matter of a few days, so our one planet per day figure looks about right.

Another interesting point on power consumption is that the machine is apparently from another galaxy. Since there are no planets between galaxies, the device must have done one of several things : either it didn't actually come from another galaxy, or it can cruise at warp speed for centuries with a vastly lower power consumption than normal, or it can cruise indefinitely at sub light speed without fuel.

Option 1 was explored in the novel "Vendetta", which was based on the assumption that the device originated from just outside our galaxy rather than from another. However, since the novels are non canon then Kirk's statement that the machine came from another galaxy remains the only canon source concerning the machine's origin. Option 2 seems unlikely - if the machine could maintain warp speed with a low fuel consumption, why would it have stopped to refuel in the middle of a battle? Option 3 seems to be the most probable. With one planetary mass worth of energy the machine could accelerate to approximately 14% of the speed of light, allowing it to cruise between galaxies in an inert state.

That the machine is equipped with a weapon which fires a beam of pure antiprotons and a tractor beam is established in the episode. That it has a general dampening field which blocks subspace and can deactivate antimatter is established by dialogue between Kirk and Scotty on the Constellation. Quite how one can "deactivate" antimatter is left as an exercise for the more imaginative reader!
© Graham & Ian Kennedy Page views : 57,160 Last updated : 12 Apr 2020