Sometimes the calcs do themselves, and I cannot complain.
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1. Ion Cube energy
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2. Thermal Energy Plant
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The Quarantine Enforcement Platform Energy Core houses energy equivalent to a 100 megaton nuclear explosion, which can be directed at vessels overhead or to strike targets in orbit.
4. Seaglide speed
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5. Seamoth speed
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6. Cyclops speed
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Final Results
1. Ion Cube energy = 5 kilotons
2. Alien Thermal Plant energy reading (per second) = 0.239 of TNT
3. Quarantine Enforcement Platform Energy Core = 100 megatons
4. Seaglide speed = 10m/s
5. Seamoth speed = 13m/s
6. Cyclops speed = 8m/s

1. Ion Cube energy

Ion cubes each contain the energy equivalent of 5 kilotons of TNT. All too simple.

2. Thermal Energy Plant

Alien Thermal Plant
The Alien Thermal Plant is the smallest of the four main Alien Bases. It can be found in the Inactive Lava Zone, within the Lava Castle. It was built around one thousand years ago. The generator is the source of power for all of the Alien technology on Planet 4546B. There are two locked doors...
(The above link also has an audio clip if need be). The Thermal Plant has a massive local energy reading in the 1000 megawatt range. 1000 megawatts is equal to 1000 megajoules per second, or 0.239006 tons of TNT. The Alien Thermal Plant stores most of this energy within battery-like devices (possibly the ion cubes), which would explain why they also have enough energy to power everything else on the planet, such as below...
3. Quarantine Enforcement Platform Energy Core

4. Seaglide speed

Seaglide (Subnautica)
The Seaglide is a handheld deployable vehicle which increases the user's top speed when held. It can be crafted by using the Fabricator. The Seaglide occupies six slots in the player's inventory. It has a top speed of 11 m/s (24.6 mph, 39.6 km/h, 21.4 knots). The Seaglide consumes energy when...
Seaglides can move at speeds of up to 36km/h, or 10m/s.
5. Seamoth speed

Seamoth
The Seamoth is a fast, safe mode of transport, but remember that swimming is good for your glutes and endorphin levels.PDA The Seamoth is a small, versatile one-person submersible and spacecraft capable of sustained high-speed travel over considerable distances. It boasts an omnidirectional...
Seamoths can move at top speeds of 13m/s (or 46.8km/h)
6. Cyclops speed

Cyclops
The Cyclops is a player-controlled submarine that is constructed using the Mobile Vehicle Bay. It is equipped with a vehicle bay capable of storing a Seamoth or Prawn Suit and can be modified with a range of different upgrades. At 54 meters long, 12 meters wide and 14 meters tall, the Cyclops is...
Cyclops submarines have a top speed of 8m/s (or 28.8km/h).
Final Results
1. Ion Cube energy = 5 kilotons
2. Alien Thermal Plant energy reading (per second) = 0.239 of TNT
3. Quarantine Enforcement Platform Energy Core = 100 megatons
4. Seaglide speed = 10m/s
5. Seamoth speed = 13m/s
6. Cyclops speed = 8m/s