My story takes place on a dark, dusty planet full of canyons and tunnels. The atmosphere is compositionally similar to Earth’s, but it is too dark and cloudy for humans to see properly.

The humans colonizing this planet in the far future are at war, so they build their best soldiers advanced combat suits. These include a short-range (150ft max) sound-based detection system. As visibility is limited, and combat occurs in small spaces, the reading from the system is processed by the suit and visually rendered inside the soldier’s visor, allowing them to “see.” While it is less precise than light-based vision, high frequencies and advanced processing allow soldiers to be able to see (and shoot) their enemies. Combatants would use relatively modern firearms in very small, tight spaces.

Would this be a feasible scenario? I found this related question, but figured these suits do not need long-ranged capability, instead needing quick, precise information over a small area.

  • $\begingroup$ Sounds like any combat would be an absolute slaughter. Too much scope for cliff and tunnel collapses, and explosives in confined spaces are especially dangerous. Unless you have a considerable surplus of "best soldiers", no-one should be sending a human to do a drone's job. $\endgroup$ Feb 19, 2022 at 10:31
  • 1
    $\begingroup$ @SeanBoddy Good point- a better excuse would be useful. I was thinking that the aliens have extremely sensitive sight but poor hearing, so the humans intentionally ridding their tunnels of as much light as possible gives them an advantage with sonar. The atmosphere isn’t breathable anyway if that makes a difference; it’s just similar enough to Earth’s for sound to travel in a similar manner. $\endgroup$
    – Mark Price
    Feb 20, 2022 at 0:29
  • 1
    $\begingroup$ Why does this need to be sonar, or any other active system? Why can't your people just use sensitive microphones which don't scream their own location? Further, what percentage of your audience will spot any problems? Whether you're building this world for the page, the screen or the game-board, who will know what you've glossed over? $\endgroup$ Feb 21, 2022 at 22:08
  • $\begingroup$ @RobbieGoodwin One man land submarine. $\endgroup$
    – DKNguyen
    Feb 22, 2022 at 5:17
  • $\begingroup$ @DKNguyen Why did you Post that, and why to me? What does it mean? What's a "land submarine"? $\endgroup$ Feb 23, 2022 at 23:42

3 Answers 3


Well, bats seems to be perfectly capable of moving into caves without bumping into objects, so echolocation in narrow environments should not be a big problem.

The real problem is that to make it work, your soldiers will need to have the suits constantly "shouting", which is the more advanced version of lighting a cigarette in the dark of the night: it will declare the suit position to anybody who has ears to ear.

Additional problem, which can be solved or mitigated with some engineering, is that many soldiers in the same environment will end up saturating it with the emissions from their suits. It will be like trying to listen to your friend while being in a loud hall where everybody is talking.

  • $\begingroup$ I'm not sure your last point holds water... there are some extremely populous bat colonies in the world which roost inside dark caves. They manage to get too and from home without thousands of them smashing into the walls of the cave every night. $\endgroup$ Feb 19, 2022 at 8:04
  • 2
    $\begingroup$ @StarfishPrime, that's why I said that it can be solved or mitigated with some engineering. Nature is a wonderful engineer. $\endgroup$
    – L.Dutch
    Feb 19, 2022 at 8:07
  • $\begingroup$ Would it potentially be wise to turn the system on and off in short bursts? It would be riskier, but one would potentially be less easy to detect. $\endgroup$
    – Mark Price
    Feb 19, 2022 at 14:39
  • 1
    $\begingroup$ @MarkPrice, it would look like being under a stroboscopic lamp in a disco $\endgroup$
    – L.Dutch
    Feb 19, 2022 at 14:46
  • $\begingroup$ Why use the suits as emitters? They could "shoot up a flare" that emits sounds, quite some distance away from themselves. Also, the emissions can happen at precisely controlled times with irregular but known delays between them, so that soldiers with equipment that knows the scheme can pick out their own returns from the crowd with ease. $\endgroup$ Feb 19, 2022 at 18:32


Keith Morrison and Sean Boddy nailed down the problem in the question you linked. Anyone relying on an active sensor system will have the use of that sensor system detected at a greater range than it will allow them to detect targets.

Imagine that you are at one end of a L-shaped tunnel, not shining any lights and not making any noise. If someone at the other end of the tunnel shines a light then they will not see you but the light they are shining will be visible at the bend and you will know they are there. If they speak then the sound will reflect around the corner and you will here them. If they send out a pulse of high frequency sound that their suit can read then your suit can detect it.

Passive detection systems are preferable where possible, but passive sonar may be difficult where there is presumably enough constant wind to keep large quantities of dust suspended in the air. (Without the wind the dust will settle and your environment will not be as described.) So if the only alternative is active detection systems then don't have the soldiers emitting the active signals. Instead, deploy a network of tiny mobile sensors and/or drones that emit the echolocation pulses and transmit the battlefield picture to the soldiers in their suits. That way, all the enemy knows when they detect a pulse is that there is a sensor in the area, they don't know whether it is a decoy, forward recon or providing targeting information to a squad of soldiers just around the corner.

The same principle applies whether you are using sonar, radar, or any system that relies on emitting a pulse and detecting a return. If sonar echolocation suits the flavour of your world then go for it. (Guessing that the reason you want sonar may be due to the suspended dust of the world interferes with getting returns in much of the EM spectrum, whether by accident or design.)

Note that all of this is assuming relatively symmetric warfare. If the humans are fighting against a non-sapient or primitive enemy that cannot detect the source of high frequency sound bursts then the echolocating humans can operate with impunity.

  • $\begingroup$ Remote sensors could work well, actually, though they cut down on versatility a little. I should have added that the humans are fighting against primitive aliens as you described. I was shooting for a mechanic where the aliens can hear the sonar clicks, but either lack the intelligence or ability to tell exactly where they are coming from. $\endgroup$
    – Mark Price
    Feb 19, 2022 at 14:36

Yet another frame challenge..

Why not use a thermal imaging camera ?


With echo location, movement of the soldier can be corrected on the fly, by software, but a range of 150 feet is not spectacular.. Sound based systems have low resolution and they will require controls and a special interactive HUD in the helmet of the soldier.

The sound can be detected by the enemy.

Not solid state

For military purposes operating in dusty and dirty environments, a sound based system has the disadvantage of (micro-) moving parts. The sound detector, e.g. a microphone of some kind, can easily get damaged and it would get cluttered with dust particles. It needs to be protected, reducing sensitivity.

The alternative

Our 21th century military and industry are already using infrared cameras..

A good thermal camera can look through smoke and dust. Check out


enter image description here



You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .