The explosion of the Tsar Bomba was so powerful as its seismic shock wave was measurable on its third trip around the globe.
The explosion of the Tsar Bomba was so powerful that its seismic shock wave was measurable on its third trip around the globe.
The explosion of the Tsar Bomba was so powerful as its seismic shock wave was measurable on its third trip around the globe.
The explosion of the Tsar Bomba was so powerful that its seismic shock wave was measurable on its third trip around the globe.
The correct idiom is "so [adjective] that [result]." This structure is a "clause of consequence": it explains the consequence of having the quality of the adjective. Here, what follows the word "that" is a consequence of the fact that the bomb was "powerful."