How close are orbital starports?

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paltrysum
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How close are orbital starports?

Postby paltrysum » Fri Oct 06, 2017 5:00 pm

I'm sure this would vary a lot from system to system, but typically how close would you imagine an orbital starport to be to the system mainworld? Surely inside 100-diameters. Inside 10 diameters? Inside 1 diameter?
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Re: How close are orbital starports?

Postby Rikki Tikki Traveller » Fri Oct 06, 2017 5:06 pm

I have always envisioned that a Highport would be at the Geosynchronis orbit above the Downport. On Earth that means about 25000 miles up.

I have nothing to base that on, but it seems logical.

For Tidally locked worlds etc. they would be in some orbit that would bring them over the Downport fairly often and would make travel simple.
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phavoc
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Re: How close are orbital starports?

Postby phavoc » Fri Oct 06, 2017 5:08 pm

Most starports are going to be in geostationary (it orbits at the same speed as the planet does) geosynchronous (equitorial orbit around the planetary access). Since thrusters are relatively cheap, station keeping in LEO orbit would be easy. All of these orbits would be around 1 diameter or less.

But, to muddy the waters, busy star systems that are transit points would normally have orbital warehousing and stations at the 100D limit so that cargo ships could more quickly load/unload their cargoes without the delay of flying into the local gravity well. You could find some passenger ships doing the same, but most likely they would be offloaded at major stations around the planet while they wait on their connecting starship. Planets are much more interesting to layover on.
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Re: How close are orbital starports?

Postby Pyromancer » Fri Oct 06, 2017 5:39 pm

I don't see the advantage of a highport in geosynchronous orbit. I'd either put it in orbit at 100D, or not in orbit at all but use thrusters to keep it just above the atmosphere above the downport.
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Re: How close are orbital starports?

Postby phavoc » Fri Oct 06, 2017 7:50 pm

Pyromancer wrote:
Fri Oct 06, 2017 5:39 pm
I don't see the advantage of a highport in geosynchronous orbit. I'd either put it in orbit at 100D, or not in orbit at all but use thrusters to keep it just above the atmosphere above the downport.
Cost is one reason (lower cost of ops). But also, why not? With grav-capable craft there's no reason to park yourself exactly over the official downport. And depending on where all the ground ports are the station handles, geosycnh might be perfect.

For the most part, a port at less than 1D is not a game issue unless the session calls for the location to matter.
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Re: How close are orbital starports?

Postby GarethL » Fri Oct 06, 2017 8:28 pm

phavoc wrote:
Fri Oct 06, 2017 5:08 pm
Most starports are going to be in geostationary (it orbits at the same speed as the planet does) geosynchronous (equitorial orbit around the planetary access). Since thrusters are relatively cheap, station keeping in LEO orbit would be easy. All of these orbits would be around 1 diameter or less.

But, to muddy the waters, busy star systems that are transit points would normally have orbital warehousing and stations at the 100D limit so that cargo ships could more quickly load/unload their cargoes without the delay of flying into the local gravity well. You could find some passenger ships doing the same, but most likely they would be offloaded at major stations around the planet while they wait on their connecting starship. Planets are much more interesting to layover on.
Geosynchronous orbit is in enough of an atmosphere on the earth to cause problems for some operations (that's one reason why GPS satellites aren't geosynchronous) which could cause issues for some ships.

Plus low orbits can be crowded.

It isn't like a few hundreds of diameters is a big deal in traveller, so there's no particular need for Highport to be very close.
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Re: How close are orbital starports?

Postby ShawnDriscoll » Fri Oct 06, 2017 8:31 pm

paltrysum wrote:
Fri Oct 06, 2017 5:00 pm
I'm sure this would vary a lot from system to system, but typically how close would you imagine an orbital starport to be to the system mainworld? Surely inside 100-diameters. Inside 10 diameters? Inside 1 diameter?
200 miles up. Sometimes, they're a space needle.
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Re: How close are orbital starports?

Postby paltrysum » Fri Oct 06, 2017 9:45 pm

So it sounds like they run the full gamut. Well, Senlis Orbital shall be inside 10-diameters, primarily because I want my travellers to get shot without a quick jump being a viable option. :twisted:
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Re: How close are orbital starports?

Postby phavoc » Fri Oct 06, 2017 10:18 pm

GarethL wrote:
Fri Oct 06, 2017 8:28 pm
Geosynchronous orbit is in enough of an atmosphere on the earth to cause problems for some operations (that's one reason why GPS satellites aren't geosynchronous) which could cause issues for some ships.

Plus low orbits can be crowded.

It isn't like a few hundreds of diameters is a big deal in traveller, so there's no particular need for Highport to be very close.
The atmosphere only goes up to about 300 miles. Geosynchronous orbits are 22,000 miles out. There is no atmosphere there. GPS satellites orbit around 12,000 miles up. They orbit at that distance because of signal strength. You may be confusing this with the orbit of the ISS, which is only 250 miles up. Now it actually has atmospheric drag on it. When the shuttles were still around they would always provide a boost for it, now those boosts are provided by the capsules that visit. Lower orbits can also provide more radiation protection, though that's not as big of a deal for Traveller tech.

Having stations closer to the planet means faster transit times to/from them. A lot is going to depend upon the needs of the planet and type of traffic it is getting.
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Re: How close are orbital starports?

Postby PsiTraveller » Fri Oct 06, 2017 10:36 pm

I had thought of a central starport located "up" from the Sun a certain distance, above the plane of the planets. This puts the Starport and warehousing in a location that is hypotensually constant for all the planets. The Starport can act as a waypoint for all the various raw materials in a system.

Systems with asteroid belts also get cycling habitats/colonies/processing modules that orbit through the system and act as mobile platforms for all sorts of ship based economy/defense/smuggling/adventure.
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Re: How close are orbital starports?

Postby Infojunky » Sat Oct 07, 2017 4:31 am

Rikki Tikki Traveller wrote:
Fri Oct 06, 2017 5:06 pm
I have always envisioned that a Highport would be at the Geosynchronis orbit above the Downport.
Well that is the assumption according to 40 years of Fluff...
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Re: How close are orbital starports?

Postby GarethL » Sat Oct 07, 2017 9:38 am

phavoc wrote:
Fri Oct 06, 2017 10:18 pm
The atmosphere only goes up to about 300 miles. Geosynchronous orbits are 22,000 miles out. There is no atmosphere there. GPS satellites orbit around 12,000 miles up. They orbit at that distance because of signal strength. You may be confusing this with the orbit of the ISS, which is only 250 miles up. Now it actually has atmospheric drag on it. When the shuttles were still around they would always provide a boost for it, now those boosts are provided by the capsules that visit. Lower orbits can also provide more radiation protection, though that's not as big of a deal for Traveller tech.

Having stations closer to the planet means faster transit times to/from them. A lot is going to depend upon the needs of the planet and type of traffic it is getting.
Mmh, under further investigation you are correct, I must be misremembering something,

I do recall that the reason the GPS satellites aren't lower is that precise positions of the satellites is crucial to the operation of the system, and that they where placed in the orbit that they where to make that easier, as any lower and turbulence is a factor.
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Re: How close are orbital starports?

Postby Dagorlad » Sun Oct 08, 2017 12:05 pm

In my setting, many systems amongst the more populous regions have multiple freight hubs orbiting the star just outside the 100d jump horizon - anywhere between 3 and 6 of them, depending on the volume of trade and the distance to the inner worlds. The idea is that interstellar freighters would jump in-system, cruise to the nearest hub and then offload their cargo, exchanging it for out-bound cargo for their next jump. A network of in-system freight haulers shuttle the goods to the planetary destinations. This provides jump-capable freighters up to four trips a month without wasting large amounts of time travelling in normal-space when the planet is in the wrong side of the sun.
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Re: How close are orbital starports?

Postby phavoc » Sun Oct 08, 2017 4:12 pm

From a pure safety standpoint you'd want orbital warehouses and stations at the 99D limit rather than at the 100D or beyond. The reason for that is safety, and security. It means that a ship exiting jump space would not be an immediate hazard to a station. As the rules stand a ship retains its heading and speed when exiting jump space. So a station or facility would only have the protection of it's own 100D sphere to prevent a ship dropping in on top of it. And since they cannot maneuver they'd be sitting ducks - messy accidents waiting to happen.

While speed and efficiency are the wherewithal of any merchant line, safety and security trump them.
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Re: How close are orbital starports?

Postby baithammer » Sun Oct 08, 2017 9:30 pm

Placement would be based on the specific functions required by the world.

For an example, a world that disallows outsiders landing any vehicle on planet would have the starport out at the 100 diameter limit and provide shuttle services to the surface.
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Re: How close are orbital starports?

Postby phavoc » Mon Oct 09, 2017 3:25 am

If it's in the Imperium a ground element can always exist. World's within Imperium space cannot stop the building of an imperial starport on the surface. They can restrict access to the rest of the planet, but that's it.
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Re: How close are orbital starports?

Postby baithammer » Mon Oct 09, 2017 3:46 am

Was meaning civilian traffic as its rather difficult to convince the Imps not take a look around.
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Re: How close are orbital starports?

Postby phavoc » Tue Oct 10, 2017 2:01 am

baithammer wrote:
Mon Oct 09, 2017 3:46 am
Was meaning civilian traffic as its rather difficult to convince the Imps not take a look around.
Generally speaking, if a world decides it hates off-worlders and does not allow for spacecraft to go anywhere but the spaceport, it could legally shoot down anything (Assuming it's both high tech and xenophobic) that strays away from the starport. Zealous enforcement on the planetary authorities part might get their ground batteries smacked via orbital strikes to teach them a lesson, but planets have the ability and legal authority to enforce their local laws. That's an extreme example, but for the most part it's up to them on how they want to deal with outsiders - so long as they stay within the Imperial guidelines.

None of this is necessairly applicable outside the Imperium.
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Re: How close are orbital starports?

Postby Condottiere » Tue Oct 10, 2017 2:26 pm

Anyone can build a spaceport, presumably, in the Imperium.

Starports are administered by the Imperium itself, and probably with a little bit of arm twisting, aren't limited to a single dirtside facility and one orbital satellite.

Though I wonder if that authority is systemwide, or only per planet.

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