A backdated post from USCRPL about the Fathom development campaign, as of right now Fathom II still holds the student altitude rocketry record of 144,000ft.
With the eventual goal of flying an 8 inch-diameter space-shot rocket (similar to our previous space shot attempts, Traveler I and Traveler II), Fathom was designed as a 6 inch-diameter subscale test. Designed to reach a maximum speed of Mach 4.5 and experience a maximum dynamic pressure of 11,000 psf, Fathom was intended to anchor and validate our aero and flight dynamics models for an eventual space-shot. The vehicle was also designed to test and qualify many of our other technologies, including our thermal protection systems. Scaling the design down from our future space-shot led to Fathom’s target altitude being set to 180,000 ft.
(As we already know, Traveler III was not recovered from its space shot attempt but work continues on Traveler IV.)