But the miniscule interplanetary acceleration of which the old style air/raft would be capable - assuming my supposition is correct about it needing substantial felt gravity to effectively function -
For the interplanetary transfer I described - 54 days from Earth to Venus as an example, that was presuming now DSM needed (which does happen even nowadays at times).
But what about a moon to moon transfer, like Regina-Harcourt?
Quoting myself: "to get anywhere else except to (possibly) a nearby moon."
Assuming they thought about it at all, whoever wrote that rule probably took a moon-to-moon transfer as being an orbital flight, not an interplanetary one.
--
Richard Aiken
"Never insult anyone by accident." Robert A. Heinlein
"I studied the Koran a great deal. I came away from that study with the conviction there have been few religions in the world as deadly to men as Muhammed." Alexis de Tocqueville
"We know a little about a lot of things; just enough to make us dangerous." Dean Winchester (fictional monster hunter portrayed by Jensen Ackles)
"It has been my experience that a gun doesn't care who pulls its trigger." Newton Knight (as portrayed by Matthew McConaughey), to a scoffing Confederate tax collector facing the weapons held by Knight's young children and wife.