Just a back of the envelope computation... Phobos’apoapsis 9517580 m. Average radius of Phobos: 11,266.7 m. Volume of Phobos = 5.99072 E+12 m³. Let’s assume a minimum ring width at least equal to Phobos’ diameter (22,533.4 m). The area of such a ring would be: 1.34743 E+12 m². The height of a *solid* ring given the…