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Re: starship-design: LINAC efficiency

Roy Bennett writes:
Hello, I am new ish to the list and have not posted before
so forgive me if there's anything wrong with this post.

I assume that by 'turnover' you mean the point at which the
ship turns round in order to decellerate. If this is the
case your ram scoop will be pretty useless as it's facing
backwards. How can a ram scoop ship decellerate?

All the starship voyages that I like are all just about the same, because
they all take about two and a half years one way, as it seems to you anyway.
The way this works out, is that you fiddle around in the system for a couple
of months, and then you boost outward for one year. It takes one year, at
one gravity acceleration, to get within a gnat's ass of C, which is 300,000
kliks per second. At that time, you want to hop around like a little bunny,
time's a-wasting, get that ship cranked around quick as you possibly can, so
you can start slowing down. Your time slippage is radical. The ratio of your
time dilation factor to clocks back home, is something you don't want to
think about, lucky thing you're so busy.

When you have your proper weight again at 1 g, your destination star system
is straight down under your feet, and the home you came from is straight up
over your head. You will have one year of slowing down to do, and then a few
months fiddling around in the system, before you can hop off your ride.
Starship journeys are all alike. When they're done right, that is. If you
you do them wrong, they can get to be a real drag.

Starship journeys done right, at a constant 1 g boost to turnover, then a
constant 1 g boost (the other way) to destination, will all take just about
the same amount of subjective ship time, whether you are going 4 light years
or 400 light years. That's because the real traveling you're doing, is
mostly done during that hectic period near the turn around, while time in
the stationary universe goes whizzing by too fast for you to notice it.

Rocket jockeys, people used to solar system dynamics, get the horrors when
you ask them for a constant 1 g boost. Nobody's that rich, they say. We
starship designers shrug, and tell them that's what we have to have; they
asked us what we needed to get the job done, and we told them. You can
either do it the right way, or you can do it any old way you want, because
it doesn't matter. The difference is, if you do it the right way, you can
get there and back, otherwise not.

When you're slowing down, your ramscoop is gathering in stuff from ahead of
the ship, just like it was in boost phase. The difference is, your jet is
also firing off in the same direction. Design-wise, you have to turn around
that stiff breeze your scoop hauls in. It's made of cosmic rays, or you
might as well call it that, because when you begin slowing down that stiff
breeze is whistling in at awfully close to lightspeed. You don't want to let
the ions blow on anything solid, because it gets eroded fast. The only way
you can turn them is with magnets, so you curl them around into your drive
and blow them all out ahead of you. This has the useful effect of ionizing
everything you're going to run into. What you don't want to deal with, is
neutral atoms coming that fast, because neutral winds can't be turned with

My version of the ram scoop, you may notice, is not attatched to the ship by
material structures. It floats out ahead of the ship a ways, consisting of
thin rings pushed out there by light pressure from lasers, as I said, or
pushed out there by neutral beams, as I didn't say.  These don't have to be
turned around, but the rest of the ship does. My LINAC is going to be long,
and it bothers me to have to turn it around, especially in a hurry.

Johnny Thunderbird