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In the original Stargate movie, Ra and his followers have ring transporters that can be used to teleport between Ra's ship in orbit and the surface of Abydos. In Stargate SG1, Earth Humans (Taur'i) eventually acquire this technology and install it on their own ships, using it for transporting between a ship and the surface and between nearby ships.

What is the maximum range of a ring transporter? In theory, could one "ring" from Earth to the Moon if one had ring stations in both locations? From Earth to Pluto? To a ship orbiting Proxima Centauri? Further? It stands to reason that there is a maximum range, as there would be no need for the regular Stargate if one could just "ring" anywhere in the universe.

I can think of two instances which give a greater range than Earth to LEO. That gives a lower bound on the range:

Season 3 Episode 12 Jolinar's Memories

gives a range from the surface of a planet to the moon. We don't know specifics of the system, but the range from Earth to Luna is about 1 lightsecond.

Season 8 Episode 10 Endgame

is a bit unclear about exactly where the parking orbit of Osiris ship was, but it might have been somewhere near Luna. Again approximately one lightsecond.

Based on what we saw and heard in multiple episodes, it would seem the transporter rings' maximum effective range is the orbit of a planet.

At least, that's the further they've been used on screen, shown clearly in the movie itself when the nuke is beamed aboard Ra's ship for example.

How far in orbit is never fully established in canon or even mentioned on screen, as far as I can remember, and Stargate Wikia's article on Transportation Rings do not mention the information, leading me to believe that it was never established in any episode.

TLDR

• We don't know of any firm upper limit to the distance the rings can transport.


• It would seem to be limited roughly from the surface of a planet to a close orbit of the same planet.


• The rings are based on similar tech to the Stargates themselves.


• I would assume the rings limitation is based on their capacitors or sensors...

So, there are no firm upper limits that we know of for pretty much anything in the Stargate universe.

Regarding the rings themselves, they are based on tech designed by the Ancients. They convert matter, transport it, and then put everything back together. While they are similar to Stargates they are not the same. I can think of three differences off the top of my head.

1. The simple fact that they can transport matter both ways. We first saw this in the original film.


2. Another big difference is that it is possible to intercept the transport with another set of rings, though I suppose technically it is possible to jump destinations, but doing so is much more complex.


3. One final key difference is that you can also use one set of rings to transport without another set of rings to receive. In this the rings also have the ability to break through materials (i.e. structures) as can be seen in the film Continuum as well as a number of episodes in the series.

Given the obvious advantages of Ring Transportation over the Stargates there must be some flaw or short coming in them that caused the development of the Stargate technology over greater distances.

If Stargates were to have a flaw it would without a doubt be the limit in their capacitors. If a gate's capacitor attempts to store too much energy it will eventually cause the gate to explode, the key to both part one and two of the Redemption episodes. This I believe is also pretty much how Vala was able to destroy the first super gate in Beachhead.

I believe it would be logical to assume that a similar short coming is inherent to the Ring Transporter that keeps a limit to the distances it can travel. An notation in the SG Wiki reinforces my thoughts with mention of a buildup causing rings to explode during the Seth episode.

The other limitation may simply be the sensors in the rings themselves. If there is a "planet to orbit" limit range on the sensors themselves that could be why they are not used over greater distances. Sensors also came into play during the Lost City episodes when the team had to drill through the ice before the rings could be used to transport to anther set that were already within the outpost.

Whether the limit is one of these reasons or something else entirely I would assume with more development the ring tech could be improved and used over greater distances. This would likely never happen (even if the Alterans never left the Milky Way and) given the development of both non-ring transportation and the birth Stargate tech as well...