You have to do something special these days to make your flying robot stand out from the swarm - but remorselessly efficient German designers have done just that. They plan to offer small unmanned air vehicles (UAVs) which can be launched and controlled from a submerged submarine.
The UAV in question is called VOLANS (coVert OpticaL Airborne reconnaissance Naval adapted System), and is based on the existing German Aladin drone, a hand-launched job which has already seen service in Afghanistan. "At least three" small folding VOLANS machines can be packed in a pressure-tight tank along with a folding catapult launcher, and the whole thing is mounted on a telescoping submarine mast which works in the same way as a periscope. The multi-purpose mast system, which can alternatively be fitted with a remote-operated heavy machine gun or electronics packages, is called "Triple M".
In order to launch a VOLANS, the sub comes to periscope depth, pops up the Triple M mast above the surface, and fires off an aircraft. The launcher mast can then seal up and slip back below the waves, though if the submarine is to receive any data from the UAV (or change its pre-programmed flight plan) it needs to put up an antenna. Video recorded aboard the drone can be downloaded to the sub later at a prearranged time, however, so there's no need to stay at periscope depth with comms mast up throughout the flight.
If the VOLANS' performance is comparable to the ordinary Aladin, it will be able to stay airborne for up to an hour before its battery runs flat. The only way for the sub to recover drones would be to surface, so realistically the system will mostly be for one-shot use. The drones have a speed of "45 to 90" km/hour, so they could range quite far from their mother ship, though they will only be able to communicate with it from within line of sight - 30km or so.
This sort of thing could be quite handy for submarines, whose great Achilles heel is their lack of sensor range when submerged. Normally a submarine - especially a non-nuclear one, slowed to a crawl when underwater - finds it extremely difficult to find or intercept a target at sea while remaining submerged, unless it is receiving information from elsewhere. Drone reconnaissance could change all that, going some way perhaps towards making conventional subs the terrible threat that former Cold War subhunter navies like to paint them as.
Even if VOLANS doesn't get picked up on radar, however, its C-band video download transmission will localise its mother sub to within a fairly small area of sea. Modern sub-hunting helicopters are said to be able to sweep such areas almost at once* using their new dipping sonars, so a sub skipper launching a VOLANS when up against first-division opposition would probably be signing his own death warrant.
The system's makers say they see it more as a thing for everyday modern missions rather than full-scale maritime combat against big navies. They reckon it might be useful, for instance, to give a special-forces team deploying by submarine a look at their landing area or target before disembarkation.
* The Royal Navy claims that it would need only two of its Merlin HM1s to monitor the whole English Channel.