What kind of technology would be required for a space travelling civilization to have an effective communication system or network that is similar in speed to the telegram? How would it work? This is a world in which FTL is not possible and colonized planets are within the same solar system. Thank you in advance.

  • 1
    $\begingroup$ If FTL is out of question, we already have the technology (directional radio). We would only need to scale this up to a solar system sized network. $\endgroup$
    – Alexander
    Apr 12 '18 at 17:59
  • $\begingroup$ @Alexander What kind of infrastructure would this require, assuming an interplanetary civilization used this for all forms of communication? Could this, in theory, support a system-spanning internet? Would this work for ships in transit between planets? $\endgroup$
    – user49634
    Apr 12 '18 at 18:06
  • 1
    $\begingroup$ We already have an interplanetary internet implemented by NASA and, I believe, also used by ESA! It's based on the Terrestrial Internet, but the protocols are somewhat different since it needs to be tolerant to long delays and segments being out of communication for extended periods. See the Wikipedia article: en.wikipedia.org/wiki/Interplanetary_Internet $\endgroup$
    – Mark Olson
    Apr 12 '18 at 18:10
  • 3
    $\begingroup$ The existing Deep Space Network might do. We just need more machines to make the network more robust. $\endgroup$ Apr 12 '18 at 18:32
  • $\begingroup$ Did you intend to include the hard-science tag? That tag has a very specific meaning that makes any question much, much harder to answer. Hover your mouse over the tag name and read the description for more info. $\endgroup$ Apr 12 '18 at 23:24

The Interplanetary Internet

It's a real project by JPL and Vint Cerf to solve just these problems being encountered by our missions to Mars. It involves designing a new set of protocols to account for the special problems of an interplanetary internet from the distances involved and the fact that the planets are in motion relative to each other. Primarily...

  • Very high latency.
  • Unreliable data links.
  • Changing lines of sight.
  • Severe bottlenecks.

We have a limited number of antennas and transmitters with the power to transmit and receive to/from other planets. They have limited bandwidth. As the Earth rotates other planets, such as Mars, will only be in the sky for an antenna for a certain period each day. The speed of light means you will always have latency measured in minutes or hours.

As planets rotate around the Sun their positions relative to each other change. If the Sun gets in the way, interference from the Sun might degrade or completely block communications. As the distances change, latency will also change. For example, Mars can be anywhere from 3 to 20 light-minutes away from the Earth.

Given these issues, the usual TCP/IP practice where each connection is negotiated, and each packet of data is sent, received, and acknowledged wasn't going to work.

Communicating within one planet is very fast and fairly reliable (for example, between satellites and the ground on Mars), but communicating between planets is very slow and unreliable (for example, communicating between Earth and Mars). This is handled by sending interplanetary communications to a node which can store messages and forward them on to another planet when the link is available.

Here on Earth, the IP (Internet Protocol) and automatic routing means we don't have to care about the details of the network. We just give an IP address. How it gets there, the routing, is taken care of for us. If part of a route is knocked out, the network will automatically reconfigure to send via some other route.

Current spacecraft typically don't have this. They need to manually manage all the details of the route. And if a route is unavailable there's often no alternative, for example between Earth and Mars, they have to store-and-forward when it is available. To solve this the Interplanetary Internet developed BP (Bundle Protocol). Like the IP protocol, it handles the details of sending an interplanetary message, including storing-and-forwarding as necessary.

This also allows multiple space missions and agencies to more easily share their interplanetary network resources. Here on Earth the Internet is a conglomeration of networks run by various businesses, countries, and countries. They make deals with each other at a high level so the result is communication flows freely between these privately owned networks for their users. The Interplanetary Internet would work similarly. Rather than NASA and ESA and JAXA all having to negotiate to use each other's communication resources for every mission, they can all negotiate once to join the Interplanetary Internet and then use its resources.

This also allows resources to be used more efficiently. An antenna which normally talks to Mars could be used to talk to another planet when Mars is below the horizon. Instead of having to be negotiated specially for each antenna, as part of the Interplanetary Internet data would be automatically routed to this idle antenna.

Because of the involvement of Vint Cerf and used concepts from the network-centric Plan 9 Operating System, this lead to the greatest talk marquee in the history of academic talks.

enter image description here

  • $\begingroup$ Out of curiosity, is your answer actually different from Renan's answer? Are NASA's DSN and II projects two different things? $\endgroup$ Apr 12 '18 at 23:26
  • $\begingroup$ @JBH Yes. DSN is NASA's private network, sort of analogous to Prodigy or AOL if you remember such things, with its own protocol. Other space agencies have their own private networks with their own protocols. II provides one protocol that works for everyone and allows all that private hardware to act as one network. Rather than connect to DSN you'd connect to II which might use DSN's dishes. In the OSI Model the dishes of DSN would be at layers 1 and 2 (physical and data) while II would be at layers 3 and 4 (network and transport) maybe 5. $\endgroup$
    – Schwern
    Apr 12 '18 at 23:39
  • $\begingroup$ @JBH For example, with II a JAXA rover on the far side of Mars wanting to get a message back to JAXA on Earth could send a message to an orbiting ESA satellite which might store it until it can get line of sight to the Earth. It might be received by a NASA Deep Space dish which then relays it to JAXA via the terrestrial Internet. When JAXA replies it could be via a Russian dish to a Chinese satellite to their rover. This would happen automatically, each node on the II (the rover, the satellite, the dish) would know how to route the message. $\endgroup$
    – Schwern
    Apr 12 '18 at 23:47
  • $\begingroup$ Yes, I remember both. I remember waiting for long periods to see graphics that make "South Park" look like world-class Disney animation. But... Does that mean both your answer and Renan's answer are needed? It sounds like II is only a protocol, not a physical implementation. The OP would certainly need both. $\endgroup$ Apr 13 '18 at 0:20
  • 1
    $\begingroup$ @JBH Since we're talking about a space fairing civilization we need something which can scale to handle the communications of an entire civilization. DSN is designed for NASA's limited needs, it's really just three big dishes, and does not scale. Like TCP/IP, II is designed to scale. II is just a set of protocols. It obviously needs hardware to work, but it doesn't say what that hardware has to be. It would likely incorporate the same NASA hardware used by DSN, but it can also use other hardware. And II doesn't need the network management part of DSN. $\endgroup$
    – Schwern
    Apr 13 '18 at 0:35

What you want already exists. It is called Deep Space Network:

The NASA Deep Space Network (DSN) is a worldwide network of US spacecraft communication facilities, located in the United States (California), Spain (Madrid), and Australia (Canberra), that supports NASA's interplanetary spacecraft missions. It also performs radio and radar astronomy observations for the exploration of the solar system and the universe, and supports selected Earth-orbiting missions. DSN is part of the NASA Jet Propulsion Laboratory (JPL). Similar networks are run by Europe, Russia, China, India, and Japan.

The DSN supports NASA's contribution to the scientific investigation of the Solar System: It provides a two-way communications link that guides and controls various NASA unmanned interplanetary space probes, and brings back the images and new scientific information these probes collect.

What you need is a similar structure on each major inhabited body, be it a planet or a moon. Probes orbiting the sun may serve as interplanetary relays.

  • $\begingroup$ Out of curiosity, is your answer actually different from Schwern's answer? Are NASA's DSN and II projects two different things? $\endgroup$ Apr 12 '18 at 23:26
  • $\begingroup$ @JBH they are different... DSN has been implemented, while II is still in planning AFAIK. $\endgroup$ Apr 12 '18 at 23:28

You must log in to answer this question.