[Starport/Downport] Location(s) in a system

[DaveChase]

Where do you think your starport should be located at?
(Gas Giant, Primary world, Asteroid belt, Edge of the Jump shadow/limit, other)

Where do you think your downport should be located at?
(Near a city/living area or far away)
(On land, on an island, on water)
(Close to industry or isolated)


Do you need a Starport if you have a downport?
Do you need a downport if you have a starport?

If you have a downport, what is the maximum tonnage of a ship that would be allowed to land?
Or is the ability to land safely the only requirement?

If you have a downport, are all ships required to land there or can they land anywhere they want on the planet?
If they can land anywhere on the planet (downport or just a starport) are they required to inform a Central control or just go where they want to go?

Dave Chase

 

[Evil Steve]

'Port locations would be based on system needs and environment. A starport near a Gas Giant makes sense, especially if the primary world is one of it's moons. I imagine it would be well within the planet's jump shadow for security and safety reasons.

Downports would always be based on need, opposed by viability. If the majority of offworld shipping is because of mining small islands in the high arctic oceans, downports may be farther away, than if the mining is in a major mountain range that borders large plains.

I don't think there's any connection between Starports and Downports as far as one must have the other.

Maximum tonnage would be based on environmental needs. Downports near or in major population centres (like airports today) would have size limits, as would any place where land is at a premium (eg;Hong Kong). Where land is cheap, and not terribly useful (eg;Egypt) just being able to land safely might be sufficient (safely being a completely local definition).

 

[Spinward Scout]

Where do you think your starport should be located at?
(Gas Giant, Primary world, Asteroid belt, Edge of the Jump shadow/limit, other)

This might give you some ideas:

http://www.travellerrpg.com/CotI/Discuss/showthread.php?t=21573

 

[kafka47]

Starports are always on the Main World, as designated by IISS. Multiple starports and spaceports may co-exist throughout a system but only a SPA certified Starport should handle interstellar traffic - as opposed to intra-system.

Its location would depend upon what is the Main World. Usually that rules out most Gas Giants although their moons are fair game as in Regina.

 

[rancke]

Do you need a Starport if you have a downport?
Do you need a downport if you have a starport?

A downport is a starport, or the surface component of a starport if said starport also has a highport.

If you have a downport, what is the maximum tonnage of a ship that would be allowed to land?
Or is the ability to land safely the only requirement?

The largest ships that are designed to land on the surface of a world are 5000T.

If you have a downport, are all ships required to land there or can they land anywhere they want on the planet?

That depends entirely on the local traffic control rules.

If they can land anywhere on the planet (downport or just a starport) are they required to inform a Central control or just go where they want to go?

If there is a system control at all, yes.


Hans

 

[E.D.Quibell]

The largest ships that are designed to land on the surface of a world are 5000T.

Why only 5,000 tonns? Is this cannon or physics, or something else entirerly?

Best regards,

Ewan

 

[Putraack]

If the "main world" is deep in a star's jump shadow, I'd think a highport further out would be desirable, to minimize a jump-freighter's time in transit. Travel to the world would be done by in-system freighters.

Near a gas giant would seem to be useful, then the port could operate the skimming & refining jobs.

 

[mbrinkhues]

I could see multiple "starports" in a system. After all a high port and a downport are okay so why not additional ports near (but inside) the 100D limit. Not in every system but systems along the major trade routes would have them IMTU allowing the big freighters to skip the long trip in-system. They aim for the ports position, drop out at 100D, get refuelled, transfer cargo/passengers and off they go.

 

[far-trader]

A thought popped into my mind reading this question earlier. What if the reason the random UWP is sometimes such a horrid place to make the Mainworld of a system is because that is where the interstellar government put The Starport* for purely defensive reasons?

* In Traveller imo Starport refers to the (singular) official interstellar travel point. Other interstellar and interplanetary ports may exist of course but they are called Spaceports and don't have the same features and facilities. The Starport may have orbital and ground components but it is all the same operation. Highport and Downport are just different terminals of The Starport.

What would be the most defensible position? Deep in the star's jump shadow I think. So anyone jumping into the system, even with a big vector built up, is going to be coming out of jump space at a good long distance from The Starport allowing as much reaction time as possible.

 

[DaveChase]

That is a good point far-trader.

Some possible ideas from the posts (and yours)

A Starport would be what a station is space (or system) is called when placed there as part of a military or Imperium need. Kind of like forts of the past in North America. Civilizations grew up around some of them and you can see it today in their names; Ft Smith Arkansas, (United States).

A spaceport would be the general term used to describe any port/facility that's main purpose is for space craft/ships to land, dock or interact with while in system.

A highport would be part of or the actual station that is in orbit around the planet or in space. (I see most but not all stations being around an stellar body or planetoid.)

A downport would be part of or the actual station that is secured on a planetoid.


(Yeah, I know that these terms have been defined before in publications. I just choose to not include any of it until now. I was trying to see how people would fill in the gaps in their posts.)

But the werid one then is the spaceport that is placed in/on an asteroid. Is it a highport or a downport. :lol:

The answer is yes. All of the above, as long as it gave good service.

Dave Chase

 

[rancke]

A thought popped into my mind reading this question earlier. What if the reason the random UWP is sometimes such a horrid place to make the Mainworld of a system is because that is where the interstellar government put The Starport* for purely defensive reasons?

You could probably use that explanation in a few cases. But generally the starport would be located where it would be of the greatest utility for the greatest number of people, i.e. usually in connection with the mainworld. If the mainworld is outside the solar jump limit, then that's just too bad. At least the planetary jump limit will provide some depth to the defense. When the 'mainworld' is an asteroid belt, the defenders will just have to live with a few nightmares.


Hans

 

[aramis]

Why only 5,000 tonns? Is this cannon or physics, or something else entirerly?

Best regards,

Ewan

5000T was the largest CT Bk2 design; lots of people limited landing capability to those and smaller. Also, keep in mind, that's 50,000 Metric Tons (±50%) or so... a 747 is roughly 440 Metric tons... we're talking 110x the mass, and about 50x the volume of a 747.

Lots of people thus limit landing vessels that way.

 

[Andrew M]

For comparison the heaviest building moved intact to date is 15,000 metric tons. I was looking into large buildings as a point of comparison for starships that could hold up against their own rocket thrusters. One gee of thrust should feel similar to one gee of gravity to the ship. Maybe inertia-less drives solve that problem somehow.

Really big buildings can cause earthquakes too.

Given these two nuggets of fact it looks like 5000 dTons is a pretty decent upper limit to pick.

 

[Patron Zero]

IMTU, I divided the duties and available facilities of starports-spaceports to 'streamline' the flow and density of inbound-outbound traffic in a particular system.

Outmost are refueling platforms that orbit gas giants, such offer only the most basic of essential 'services' being fuel, life support (water-oxygen) and up-to-date navigational information.

Further insystem would be the shipping terminals, freight waiting for transfer on-off departing-arriving starships or local spacecraft hauling cargo to-from the prime world. Additional services would be available here, repair and maintenance 'slips' for vessels in need of minor attention. Dedicated drydocks may-may not be present as such are decided by demand-volume of traffic in said system.

Highport would be in orbit above the prime world, again based on traffic-need, a space elevator may-may not be present. A combination of port authority and customs house, said facility would be more passenger-personnel oriented with limited cargo-freight operations beyond 'small' packet items.

Starports would be groundside and allow non-starships to load-unload freight for-from mid-system shipping terminals, starships of 200 tons or less would find berthing available with limited services for maintenance or repairs.


Mind the above is said as a general rule but exceptions are determined by factors of a system's available resources, resident population and demand of commerce.

 

[aramis]

Oh, andjust to give an idea of what 50,000 metric tons looks like...

Think USS Iowa or USS New Jersey...

Displacement
Light Displacement: 45231 tons
Full Displacement: 57271 tons
(http://www.fas.org/programs/ssp/man/uswpns/navy/surfacewarfare/bb61iowa.html)​

A 5000 ton ship landing is like drydocking an Iowa Class BB... (I actually estimate her overall volume to be about 8,000 Td...so think all her mass, but in a space only equal to the main deck and below...)

 

[HiverLord]

One other factor in placing Downports is gravity and rotation of the planet.

Especially for planets with higher gravity and larger diameters, the rotation of the planet will affect ("add to") the take-off speeds of vessels. This may not apply as much to smaller-diameter planets, but for larger ones, the added rotational speed will assist vessels with takeoff speed. (I'm sure NASA wishes they had a facility closer to the Earth's equator...)
Admittedly, grav ships have fewer problems with this, as their gravity-assist engines can (hopefully) compensate for the increased gravity. For ships which may be using reaction drives, take-offs and landings can be very expensive, not to mention dangerous (backwash, etc.) But if they do land, the added momentum from the planet's rotation can be a large boost to their take-off speeds.
These factors will generally cause Downports to be placed closer to the planet's equator whenever feasible, especially with Downports which are older/established at lower tech levels/etc.

 

[PFVA63]

Hi

Here's an image that I've posted before, that might be of help. It shows a plot of internal volume for seagoing ships versus their "hydrostatic displacement". Here internal volume represents the total enclosed space within the vessel, taken from some technical papers that I have on these type vessels. Hydrostatic displacement is really a measure of how much the ship weighs, since by virtue of Archimide's Principal, the weight of everything on the ship will be equal to the weight of the volume of the liquid that it displaces. As such, hydrostatic displacement equals the volume of the ship under the water. For a submarine since the density of seawater is roughly 1.025 t/cubic meter, then the total enclosed volume of a submarine will be very close to the "hydrostatic displacement" of the vessel.

Anyway, from the image below you can see that an internal volume of 70,000 cubic meters (or the equivalent of 5000 dtons in Traveller terms) is just a bit smaller than the upper Amphibious ship shown in the plot, which if I am recalling correctly, is the LSD 49 class vessel, as shown below, which is 190m long by 26m wide and has a full load "hydrostatic displacement" of over 16,000t.

To get back to Arimis's point, I wouldn't want to see a streamlined version of something this big trying to land on a planet.

Regards

PF

 

[aramis]

For comparison, the bounding box on that is 177' total height (21' of which is hidden under the water), 610' length, and 84' beam maximum...

That gives a bounding box volume of 9069480 cubic feet... given the roughly 500 cubic feet per Td: she's some 18,139 Td bounding box....

she's less tha half that, tho, in terms of inside the skin volume; the hull is probably about 50'... 610*84*50=2562000cf, or 5124Td, and loses about 2/3x1/5 for the 1/5 length pyramidal prow, leaving 4450Td... but adding roughly 1000Td for the superstructure... roughly 5500Td for LSD49... and a displacement of water of 16400tons laden; 14.9KT metric... and about 1/3 the density of typical FF&S and MT designs... She's the right volume, and the wrong mass. (And she looks mighty big in person. (Numbers from http://www.fas.org/programs/ssp/man/uswpns/navy/amphibious/lsd49.html ) I'd estimate, including external gear, roughly 6000Td...