Unmanned Aerial ASW

One of the common ideas for future ASW operations is to use unmanned aircraft.  However, I have seen no detailed discussion of such a UAV and there are significant problems associated with the concept.  More generally, there is a tendency, now, to simply say “unmanned” in response to every military problem or function and then consider the discussion finished, as if unmanned is the automatic and complete solution to everything.  Diversity is the same way – you say “diversity” and all further discussion stops.  No one bothers to question whether diversity actually offers any inherent benefits.  But, I digress …

Is unmanned aerial ASW feasible?  Is it effective?  Is it cost effective.  Is it …?

Let’s take a closer look at surface ship unmanned aerial ASW possibilities.

One of the key benefits is that the ASW-UAV is presumed to be significantly smaller than the standard SH-60 type helo and, therefore, more aircraft can be carried by a ship thus expanding ASW coverage.  This would certainly be true if the smaller ASW-UAV carried the same amount of sonobuoys, dipping sonars, torpedoes, comm gear, MAD detectors, radar, etc. that the SH-60 does.  Unfortunately, herein lies the first problem with ASW-UAVs – they’re small.  They can’t carry the same load of gear.

Let’s look at the Navy’s standard UAV, the Fire Scout MQ-8B, which would, presumably, be the UAV of choice for the surface ship ASW-UAV role.  Here are some publicly cited weights of interest.

Payload = 600 lb

Empty Weight = 2073 lb

Max Takeoff Weight = 3150 lb

So, we’ve got a 600 lb payload to work with.  What does ASW gear weigh?  Here’s some weights for the common torpedoes used in ASW.

Mk46 = 508 lb

Mk50 = 800 lb

Mk54 = 608 lb

We see, then, that the Fire Scout’s entire payload is consumed by a single torpedo.  But wait, don’t we need dipping sonars and sonobuoys and radars and other stuff?  Here’s some weights for the sonobuoys.

Sonobuoys = ~20 lb each

Sonobuoy Launcher  = ~8 lb each

So, for a load of, say, 24 sonobuoys, that equates to 672 lbs and that’s without any of the supporting electrical, power, computer, and comm gear needed to actually operate the sonobuoy launch system.

MQ-8B Fire Scout

 All right, we can see where this is going.  I won’t even bother to cite weights for MAD gear, radars, etc.  The MQ-8B Fire Scout clearly isn’t going to be able to carry an entire ASW equipment fit.  The MQ-8B’s successor, the MQ-8C, however, is much larger so maybe it can carry the necessary equipment.  Here’s a few pertinent spec’s for the “C” model.  The “C” is based on the Bell 407 model, by the way.

Length = 41 ft  (24 ft for MQ-8B)

Rotor Diameter = 35 ft  (27 ft for MQ-8B)

Max Weight = 6000 lb

Payload = 500 lb

Despite being larger, the payload is actually a bit smaller than the “B” model.  On the plus side, the base “C” model, in its commercial Bell 407 version, is capable of carrying a 2,560 lb external sling load.  Although that doesn’t help as far as mounting ASW equipment it might offer the possibility of carrying torpedoes.

Regardless of the exact payload, the problem with the “C” model is that it isn’t all that much smaller than a full size SH-60 helo.  Here’s some dimensions of the SH-60 for comparison with MQ-8B/C values in parentheses.

Length = 64 ft  (41 ft for the “C”, 24 ft for “B”)

Rotor Diameter = 53 ft  (35 ft for the “C”, 27 ft for the “B”)

Clearly, the “C” isn’t going to gain us multiple airframes in the same space as the SH-60 as UAV proponents like to claim.

MQ-8C Fire Scout

 Another claimed benefit is endurance and, like all unmanned vehicles, can potentially offer greater endurance by eliminating the crew fatigue issue.  However, also like all unmanned vehicles, endurance does not eliminate mechanical issues.  Aircraft, whether manned or unmanned, suffer from mechanical issues and it is often these problems that wind up limiting an aircraft’s endurance especially for helos and especially for aircraft operating in a more stressful environment such as rapidly changing speed, direction, and altitude, as an ASW helo would, and operating close to the water surface and subject to wind, spray, fog, rain, etc.  Extremely high endurance UAVs, in contrast, operate at high altitudes, above the effects of weather, at constant speeds, and with little maneuvering – a much less mechanically stressful environment.

Endurance is also limited by equipment quantities.  For instance, if we want to use an ASW-UAV for 8-12 hours of continuous ASW coverage we would need to include a sizable quantity of sonobuoys – far more than an SH-60 typically carries.  That increases the weight and requires more space which means the UAV must be larger, thereby negating the UAV small size benefit.  Conversely, if we want to keep the UAV small then it will have to return to the ship for reloading of sonobuoys on a more frequent basis, thereby negating the endurance benefit.

So, where does this leave us?  We can design an unmanned helo to carry all the requisite ASW equipment but the resulting size will push us back near the manned SH-60 helo and won’t gain us the several UAVs per ship that would offer the potential for greatly expanding our ASW coverage.

Alternatively, we could design small UAVs that would each carry a single “function” of the ASW fit.  For example, one UAV could carry sonobuoys, another could carry MAD and a dipping sonar, and one could carry the anti-submarine torpedoes.  This should sound familiar, by the way.  You’ll recall that the Drone Anti-Submarine Helicopter (DASH) of the early 1960’s carried a single torpedo or depth charge and was used as a weapons transport platform to attack a target located by the host ship.

The problem with splitting the ASW equipment among multiple UAVs is that now multiple UAVs are required to perform the complete ASW operation on a single target.  Again, this won’t result in a net increase in ASW aircraft or coverage.

Finally, communications are a persistent problem for UAVs.  They have a disturbing tendency to wander off, never to be seen again.  The problem will be exacerbated operating just off the surface of the water.  At those altitudes it is unknown how far effective control comms can be maintained.  It may not be possible to control an ASW-UAV at useful distances from the host vessel.  Of course, operating in an electromagnetically challenged environment may also preclude effective ASW-UAV operations.

In summary, ASW-UAVs are a potentially beneficial concept.  Eliminating crew fatigue as a limiting factor on endurance is a tremendous potential benefit.  Smaller UAVs offer the possibility of expanding ASW coverage.  The practical problems, however, do not seem readily solvable at this time.  This is a concept well worth pursuing as a developmental effort but I do not see a practical use in the near future.

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