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Year 2317 C.E. traffic report: heavy traffic expected along upper Curiosity sector H-311 going towards Juno boulevard, there is an accident at Exit C right lane, so vehicle leaving for Europa via this exit be prepared to slow down and keep UP or to your left...

Question:

Since all spacecraft must come with fully automatic pilot control (you know the autonomous thingy which allows all space faring vehicles to talk to each other in silent while getting humans or goods to their destination), does that means we would have no need for trafficators?

Note: yes ladies and gentlemen I shall present to you, FTL... you wish!

NO FTL.

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  • $\begingroup$ signal indicators? What signal? I don't get it, what are you talking about? $\endgroup$ – Mołot Jan 20 '17 at 5:57
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    $\begingroup$ Indicators. No. But Position Lights like the red and green lamps on planes or ships are more likely $\endgroup$ – Alexander von Wernherr Jan 20 '17 at 6:35
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    $\begingroup$ The term you are looking for is "trafficator". On cars they signal changes of direction, turning, changing lanes, and braking. $\endgroup$ – a4android Jan 20 '17 at 7:11
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    $\begingroup$ @user6760, you've got stuck between US and UK English :) Trafficator is an unknown term in the UK, we use indicator. "Turn signal" is probably the most universal term to be understood by both groups. $\endgroup$ – Separatrix Jan 20 '17 at 9:18
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    $\begingroup$ -1 The terminology is still a mess. It's still not clear whether you are asking about brake lights, turn signals, or both (or maybe even navigation lights); and you keep using a term that is unknown in the UK. This is an international forum. $\endgroup$ – user3106 Jan 20 '17 at 10:03
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Yes, but...

But not during voyage. During maneuvers near space stations or other locations you want every help you get. Look at the real history of docking in space. Not one time automation failed and people needed to go manual, and use visual aids. You have to assume autopilot may jam. You have to assume that even trained professionals may get stressed out. Or that their radio may fail, making both automatic data exchange and conversation impossible.

Lights are cheap and clearly visible, so if space traffic will get higher, tey will get popular.

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Navigation lights are a theoretical necessity, though you'll need a few more to make up for the loss of up and down. Port, Starboard, Top, Bottom, Bow, Stern. You can now tell at a glance the orientation of any ship. How you light ships that rotate for gravity is not something I'll get into now.

Turn signals are for close maneuvering, it's to allow someone behind to react to something you're going to do with appropriate notice. A nice simple concept, except it doesn't work.


Let's start with a quote from one of the greats, whose work I'm sure you're all familiar with.

Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space.

Why is this relevant? Dispersal of light, ships are not going to be close enough for navigation lights to be seen.

We talk of ships passing in the night

Ships that pass in the night, and speak each other in passing,
Only a signal shown and a distant voice in the darkness;
So on the ocean of life we pass and speak one another,
Only a look and a voice, then darkness again and a silence.

Ships passing in space? They might hear the voice in the dark, but the signal shown will be lost in the night. Points of light against a background of points of light. At best a twinkle in the darkness in the vast spaces between the stars, as bright as your lights might be, the stars are ever so much brighter.


Your turn signal lets cars around you know what you're about to do in good time to slow down or take other basic evasive action. At normal speeds, when you have traction against the ground, and a reasonable means of stopping.

There's a saying with hovercraft, that if you can see something in front of you, you're going to hit it. No traction, minimal brakes.

What all this means to a ship in space at interplanetary or even orbital speeds, is that if you're in a situation where you can both see and need to respond to a turn signal, it's already far far too late. At least nobody will hear you scream.

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  • $\begingroup$ u high, or I just do not get the question and haven't noticed humor tag and Lovecraft. Ah, ok I see comments to the question( $\endgroup$ – MolbOrg Jan 20 '17 at 11:04
  • $\begingroup$ @MolbOrg, I am, with a hint of added poetry and perhaps a touch of humour, explaining why nav lights on starships are pointless. Since we don't have science-based or hard science tags, I've left out the numbers for actual visual distances, orbital and relative speeds etc. $\endgroup$ – Separatrix Jan 20 '17 at 11:23
  • $\begingroup$ yeah yeah, poetry is the best part, for some reason, I immediately recall about Lovecraft after that poetry )). And sure Initially I'm totally missed what OP is asking for, so left the comment in case someone will have the same lost feeling. In the darkness, with space Cthulhu with trafficking lights of humans flashing with flashlights. $\endgroup$ – MolbOrg Jan 20 '17 at 11:39
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Running lights could be a last-ditch emergency system. If they are out, you know that the ship is really dead. If need be, a survivor can try to use morse code with a light.

And don't just consider other ships. What about maintenance techs in a spacesuit? Do they have the full array of autopilot systems?

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Yes but....

The OP describes low speed, terrestrial street style traffic. There's no references to orbital mechanics or interplanetary speeds. Without that setting, discussion about long distance communication by way of signalling semaphores isn't appropriate.

When driving around, or flying around, a vehicle in traffic needs to choose an approach; either it will fly far enough away from all other vehicles so that it has the space to deconflict, or some kind of signalling system will be used to signal intent. Cars on terrestrial roads use a combination of both approaches as proved by "Use your f**kin' turn signal!" and "Keep two seconds between you and the car in front of you."

Whether this is a autonomous vehicle or human controlled, the requirements are the same. You must signal course-intent in close proximity to other vehicles or give so much space that you have plenty of time to evade in case paths do conflict.

How

How course-intent is communicated will depend on the speeds and distances involved. The closer to terrestrial traffic these spaceships are, the more closely they will approximate how cars signal each other. However, the greater the distance between cars, the less useful these signals will be. At beyond-visual-range, an Air Traffic Control service will work far better for ensuring safe passage.

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The idea behind signal indicators is to let other people on the road - err, space road? - know what the driver intends to do. In the case of spacecraft, the only people around will also likely be in spacecraft, so if all of them are fully automatically controlled and are digitally communicating, then they aren't strictly necessary. If some spacecraft could be manually controlled or if there are non-spacecraft entities that would benefit from knowing what vehicles are going to do, then they would still be pretty useful.

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No.

Consider the speeds needed for interstellar travel. If you're on a collision course with another vessel, by the time you've seen it you're going to hit it. If you're going to be 'driving' ships around the sky, then you're going to need radars and computers to stop you from crashing into things.

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  • $\begingroup$ Yet some forward warning time might at least let you fasten your seat belts and maybe help reduce the damage. When the risk is high enough, every little help is good, especially when it's as cheap as some lights. $\endgroup$ – Burki Jan 20 '17 at 16:07
  • $\begingroup$ I think you've missed the point - say you're travelling at 0.01C, walking pace in interstellar terms. That's 3,000 KM per second. Say you can see the ship itself in space at 100km - that doesn't give you time to actually register its existence, much less take avoiding action of any sort. Remember that's the distance to see the ship, let alone the flashing lights on it. $\endgroup$ – Matt Bowyer Jan 20 '17 at 17:06
  • $\begingroup$ Most ships exist to go from somewhere to somewhere. Close to those somewheres they will be travelling much slower. And the lights are still so cheap that even a remote chance of them being helpful would justify their existence. Not as primary security equipment, but as a remotely helpful backup in most situations. $\endgroup$ – Burki Jan 20 '17 at 17:36
  • $\begingroup$ Yes, possibly whilst maneouvring around space stations, etc. $\endgroup$ – Matt Bowyer Jan 20 '17 at 22:23

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