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On Fri, 8/11/17, via tml list <xxxxxx@simplelists.com> wrote:

 Subject: Re: [TML] What class of Port is this?
 To: xxxxxx@simplelists.com
 Date: Friday, August 11, 2017, 2:13 PM

 On 11 Aug 2017 at 17:37, Phil
 Pugliese (via tml list) wrote:

 > p.s.
 Anyone ever think about a situation where a planet might
 have a
 > HiPort but no DownPort?

 Well, a size 0 world might do
 that. Ditto for worlds with the
 stranger
 atmosphere types.

 And
 that's almost certainly the case with all red-zoned
 worlds and
 some amber.

 There could be other reasons as well, say
 there's a religion that
 considers the
 planet holy (think Mecca). They might only allow
 specially crewed and putified shuttles to
 land.

 And some of the
 stricter government types might have similar
 restrictions.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Well, 'asteroid' belts aren't really worlds or planets in my book.
Even if a starport was 'anchored' to one of the larger 'rocks', I don't think it would actually be considered a down port.
Not as long as unstreamlined ships could dock.
And there are red zone worlds that must have down ports, Andory & Candor in 5sisters/spinward marches for example.
They are Droyne worlds that are capable of starflight. In fact there's even a Droyne trading company hq'd there!
Also, elsewhere in the 'Marches, there's Victoria, (where the weird starship in the 1st CT LBB double adventure, AnnicNova, came from.
I believe that the writeup for the system was published in a CT JTAS article.
Lastly, a lot would depend on the specifics of the Imperial Charter granted to a specific system. I can see where the ImpGov would insist on a downport, w/ it's attendant extrality zone, for various reasons.

I can see where it might happen but I think it's be pretty rare.

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