Question: Why can solid rockets be both the skinniest and most spherical launch vehicles while liquid fuel rockets have a more limited range of aspect ratios? Are there fundamental engineering principles at work? Simple physics? Or is the devil in the details?
Evidence of solid rocket launch vehicle "noodlicity":
- Scout X-2: 25m: 1.01m = 24.75
Evidence of solid rocket launch vehicle sphericity:
The first stage of this Mars launch vehicle is pretty squat and is just as spherical as a spherical cow. Source: Spaceflight Now's NASA narrows design for rocket to launch samples off of Mars
This diagram illustrates one concept for a two-stage, solid-fueled Mars Ascent Vehicle. Credit: NASA/MSFC
Counterevidence: squat liquid launch vehicles
- SERV "VTOVL orbital launch vehicle. Chrysler ballistic single stage to orbit alternate shuttle proposal of June 1971. This was the most detailed design study ever performed on a VTOVL SSTO launch vehicle. The 2,040 metric ton SERV was designed to deliver a 53 metric ton payload to orbit in a capacious 7 m x 18 m payload bay."
- Apollo Lunar Module