On Fri, May 8, 2020 at 5:54 PM James Davies <xxxxxx@hotmail.com> wrote:

CT Book 3, page 23 says:  An air/raft can reach orbit in several hours (number of hours equal to planetary size digit in the UPP); passengers must wear vacc suits and

interplanetary travel in an air/raft is not possible. 

 

Which might have resulted from a misunderstanding of what "orbit" is. The car can lift itself to orbital distance but not attain orbital velocity and just fall back down again. 

I think what might be happening here is that the air/raft can climb to orbit using "simple" cancellation of felt gravity, plus it's modest acceleration to overcome the friction of the atmosphere. The atmosphere thins and felt gravity drops off as altitude increases, so the air/raft's acceleration *could* potentially increase. Yet the rule says that even though it can reach orbit it remains incapable of interplanetary travel.

I take this to mean that the air/raft's propulsion is somehow inextricably linked to felt gravity. Propulsion efficiency drops in close proportion to the felt gravity. Once the latter reaches microgravity strength, the former essentially ceases to function.

The air/raft will never fall back down (at least as long as it has a powered propulsion system), but neither will it be able to accelerate to actual orbital speed. At least, not using it's basic hardware. So everyone needs to wear a booster pack, if they want to actually rendezvous with a ship or station in orbit. Maybe one of the myriad Modular Cutter modules include one designed to let you scoop up such a "speed bump" air/raft without damage. Sort of a meta-scale Bussard Ramjet collector? 

 

--

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.

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