if it took four years for a message to cross the void from where you are to the recipient, you certainly wouldn't want to wait a full eight years to see they didn't send a receipt message and only then retransmit.
eight years is some awful latency.
you'd probably want to send each message at something like a fibonacci over the months. so, gaps of (1, 1, 2, 3, 5, 8, etc) would mean sending the message on months (1, 2, 4, 7, 12, 20, 33, etc) until you got a confirmation message that they had received it. they would similarly want to send confirmations in the same sort of pattern until they stopped receiving copies of that message.
spreading the resends out over time would ensure not all of your bandwidth was going to retransmissions. you'd want that higher number of initial transmissions in hopes that enough of the message makes it across the void that they would have started sending receipts reasonably close to the four years the initial message would take to get there.
if you had the equivalent of a galactic fido-net system, it could be decades and lifetimes between messages sent to distant stars and messages sent back.
if it takes a large amount of energy to send the data, we probably wouldn't want to run the equipment all the time. strong pulses would let the equipment cool down or recharge capacitor banks or whatever during downtime.
interstellar dust and other debris floating through space could cause interference, not to mention radiation from everything else around us, and our own sun shining right next to our little laser.
might want to move the laser out onto pluto or something to avoid having it right up against the sun.
Also, our signals are usually going very short distances very quickly and are very protected from solar/cosmic waves by the ionosphere. What kind of data loss could you get transmitting in open space across vast distances and time?
Determining theoretical interstellar link rates is a fairly straightforward link budgeting exercise, easier in fact than most terrestrial link calculations because you don't have multipath to worry about.
You'd need a mission whose purpose is to emplace compute stations.
That's why we can't have nice things.
1. exactly what prefixes need to be buffered based on the received interest messages from deep space 2. exactly which data rate is possible at any given time 3. exactly how much data needs to be sent from the buffer in each transmission
optimizing for high latency really pushes your design choices around compared to our comparatively very low latency uses here on earth. its pretty interesting to think about.
It would be more like a handful of satellites, some orbiting earth, some orbiting mars, and then a handful of relay satellites serving as intermediaries.
Don't count on playing e-sports competitively, though.
The lag under ideal conditions would be insane, about 2.5 minutes each way (when the planets are "only" 40 million kilometers apart), but with repeaters and overhead probably closer to twice that.
> throw tons of datacenter and compute that's anywhere more than a few light-seconds from the nearest existing datacenter
I think I'm misinterpreting the comment.
We wouldn't need to blanket the solar system in data centers to be able to communicate with other planets. We would only need enough connections so that no matter where in their respective orbits they are, there is a line of radio "sight" that is clear enough for high bandwidth communications to work.
I don't have access to the specifics, but I imagine something between 5 and 10 satellite data centers orbiting the sun in between earth and mars would be enough to maintain communications with minimum delay regardless of when in the solar year the comms take place.
Once you take into consideration the sun, plus the fact that the you'd need to cover the full disk to keep all data centers within a few minutes of another one in an unbroken chain back to both planets, I just don't get the math involved here.
But, I'm also terrible at both math and visualization, so I readily concede I may be missing something obvious.
The inner circle has Earth's orbit in it. The outer circle is Mar's orbit.
The middle circle would be a ring of relatively stationary satellites in between them.
And in the center of all 3 circles is the Sun, which will not allow radio signals to pass through.
I drew a crappy illustration to demonstrate: https://ibb.co/tP2rkzS0
When Mars and the Earth are on opposite sides of the sun, a satellite ring can transmit around the sun and keep the communication lines open.
Having a ring of relay satellites gives you a set distance to transmit from Mars. The satellites can then transmit their received data from the one that is closest to Mars to the one that is closest to Earth, which would then send the data to Earth.
This is helpful for a variety of reasons, but the most important one is that with this setup, even when the Sun is in between Earth and Mars, you could still send data around the sun.
Constant communication, no communications breakdowns. Even if 1 satellite failed for some reason, a bit of maneuvering would allow the others to backfill the gap until it could be repaired or replaced.
Even when Earth and Mars are close together, it would still be smart to use the relay so that the power levels are easily calculated and maintained.
There will be some lag as each satellite would need to cache the data before retransmitting, and it would need to store that data for a short period as well in case of failure, so assume that it would double the time for each stop under ideal locations, so to get information 4 light seconds away would take approx 8 seconds, and a minimum of 16 seconds for a response assuming they started replying the instant they received.