True, the integral NASA engineer Jack Parsons (Frater Belarion) was no Satanist. He was a Thelemite through and through, a disciple of Aleister Crowley and 8°=3□ Magister Templi in the A∴A∴, and emphatically anti-Christian, who at one point had embarked on a series of intensive rituals known as 'Babalon Working'.
He was intent, informally following the ritualistic practice of Thelemite organization the A∴A∴, on performing "the Crossing of the Abyss", attaining union with the universal consciousness, or "All" as understood in Thelemic mysticism, and becoming the "Master of the Temple".Following his apparent success in doing so, Parsons recounted having an out-of-body experience invoked by Babalon, who astrally transported him to the biblical City of Chorazin, an experience he referred to as a "Black Pilgrimage". Accompanying Parsons' "Oath of the Abyss" was his own "Oath of the AntiChrist", which was witnessed by Wilfred Talbot Smith. In this oath, Parsons professed to embody an entity named Belarion Armillus Al Dajjal, the Antichrist "who am come [sic] to fulfill the law of the Beast 666 [Aleister Crowley]". Viewing these oaths as the completion of the Babalon Working, Parsons wrote an illeist autobiography titled Analysis by a Master of the Temple and an occult text titled The Book of AntiChrist. In the latter work, Parsons (writing as Belarion) prophesied that in seven years—on the condition that he lived—Babalon would manifest on Earth, supersede the Abrahamic religions and convert the world to Thelema.
If you would like to learn more about Parsons, see: