Whilst The Astronef proved more than capable of extra-terrestrial flight as demonstrated by Earl Redgrave's tour of the Solar System in 1895, the quantity of R-Gravitons needed for such travel restricted the numbers of astronef employed by the Great Powers in the ether at the turn of the century. Indeed, it was an older technology based on that employed by the Baltimore Gun Club with its Columbiad cannon after the American Civil War which was to prove the low cost answer to the Great Powers need to get troops to Mars following the Olympian invasion and subsequent Martian Rebellion of 1903.
All the Great Powers constructed huge cannon to fire shell like troop transports, first to Mars and subsequently the Moon, Venus and Ganymede. These transports have extremely strong hulls to withstand the pressure of firing and landing, but the crew have limited control of the craft in flight and a reasonably fixed course must be maintained to ensure the landing zone on the target planet is hit.
The transports, whilst escorted by astronef, do sport limited weaponry and indeed it was an astro-transport that engaged in the first space battle in humanities history when a convoy carrying troops to the Red Planet as part of the retaliatory invasion against the Olympians was attacked by Martian craft.