So I had a lot of fun reading the short story "Into Darkness" written by Greg Egan (Axiomatic 2010). I want to play with a few of the concepts of that story. In particular, the general theme of a rescue crew going in to assist in the face of some event where the precise nature of what is going on is poorly understood.
In "Into Darkness" there are randomly occurring events that take place, which I am going to refer to as Anistropic events. From the outside it looks like a giant completely black hemi-sphere suddenly appears. It projects around from a point, with a radius covering up to a couple of city blocks, though the limits on the size are poorly understood. The event appears black from the outside because light does not pass through it, or reflect off it's boundary.
Inside the event, time becomes bound to the spatial dimension projecting from the center around the radius. That is time only moves forward as you move closer to the center. To an observer inside the event, they can see rays of light from outside (the past) but none projecting back from inside. They can move along an arc, or in a line towards the center. But they cannot move away from the center. In Egan's story, surviving an event like this requires one to travel to it's epi-center. After a period of unknown time the event passes, and all matter outside the epi-centre is homogenized. So "runners" volunteer to run in and guide any unlucky folk to the epi-centre.
Naturally this impacts the communications available to the rescue team. If I recall correctly, the ones entering the event don't bother with radios. They don't get much utility, seeing as they can't send signals out, and very limited ability to only send signals to members already "deeper" in than themselves. In principle though, they can receive messages from a command site that was broadcasting from outside the event horizon. Provided they were not standing on the opposite side of the epi-centre to the broadcaster.
In the real world of natural disasters, communications are critical to coordinating an emergency response. Responses over large areas and multiple crews usually use a combination of short-wave radio (which can be blocked by mountains and valleys) and cell networks (which require a bunch of potentially fragile infrastructure).
That was just to give you an idea of the sort of thing I'd like to consider. I want to work on a setting where a team are trying to respond to some situation, but are somehow limited to one-way communication only.
In terms of real world scenarios I can think of at least two.
The first is a air-to-ground operation where the ground team have no radios, and are limited to low tech signalling, (ie rock formations, large logs, smoke). In this setting the air team could be tracking the location and intended movements of the ground team, but have no good way of signalling their own intentions (although they may hover in place / circle a location of interest).
The second is more historical. I'm thinking of the sort of voyages from the age of discovery, from the 13th century, until I guess around invention of the telegram. Any long distance mission really had a general set of orders, from a monarch, or Pope, but had no way of communicating operationally relevant details in any useful time frame. If the voyage encountered pirates, or a new land mass, it was really at the discretion of the ships captain as to how to proceed; be it fight, flight, or lay claim.
I guess time is the biggest obstacle to two way communications. The time it takes for a message to get to the recipient, for them to process it, and for a reply to return to the sender. In my historical case, the time limit on a message is the same as the time it takes to move a person from one location to another (pigeons only work over limited distances). In "Anisotropy" messaging with radio would be instantaneous, but for a runner trying to communicate with onsite command, they are trying to send a message to the past.
Physical obstacles are also part of the problem. The ground team, in my other example, cannot practically get to the air team to listen to any message, and then safely back down. Like wise a large object, or metal barrier, can block radio waves from getting from one site to another.
Returning to the Anisotropic event. I would like to think seriously about how a real world team would go about responding to an event like this. In particular what communications strategies they might develop, knowing that the field-operatives won't be able to talk-back.
Part of my response would be to setup a series of 3-4 transmit stations around the event, at some distance to get a reasonable view into it. These stations would be relaying messages from a central-command, broadcasting general instructions to anyone inside the event (ie "Walk towards the darkness", "Move slowly and calmly", "Avoid climbing or descending").
As for the runners themselves, I would imagine that part of their kit would include flouro-paint-pens and glow sticks. They could leave a trail of breadcrumbs to anyone who enters after them to show the path they had taken. This is more for the benefit of other runners, though. Anyone seeing the trail has no way of knowing if it leads to saftey or a literal dead end. However, a second runner can see the marks and may decide to diverge, to increase coverage of the rescue crew.
This feels to me about the best I can come up with.
Are there other strategies, or solutions that would help in this situation?