# Why do cruise missiles look different than subsonic jet aircraft?

They both fly. They both carry loads.

Why do cruise missiles look too different from subsonic jet aircraft?

• Part of it may be the huge power/weight ratio difference. – Ron Beyer Feb 2 '17 at 22:51
• ...or a bunch of fragile humans and equipment to keep them comfy. – acpilot Feb 3 '17 at 3:15
• And they don't have to worry about doing takeoffs and landings. – jamesqf Feb 3 '17 at 6:47
• Frankly, considering the difference in mission, I think those look remarkably similar. – FreeMan Feb 3 '17 at 19:24

They are designed to fly at one Mach-altitude combination only. Regular aircraft have to take off and land (low Mach, low altitude) and cruise (high Mach, high altitude). Cruise missiles are launched either from aircraft or accelerated by a booster rocket so their flight starts at a high Mach number already. Next, their nap-of-the-earth flight means they never go high, but stay low for the whole duration of the flight.

To minimize wing surface and, consequently, drag, the cruise missile has a higher wing loading than any aircraft. The published data only gives mass and wing span, so I needed to guess the wing area:

• BGM-109 Tomahawk: 1192.5 kg, 2.67 m wing span. If I assume an aspect ratio of 6, the wing area is 1.188 m² for a wing loading of 1004 kg/m².
• Boeing AGM-86: 1430 kg, 3.7 m wing span. This one has an aspect ratio of maybe 10, so the wing area is around 1.37 m² for a wing loading of 1044 kg/m².

For comparison, a typical airliner wing loading is around 600 kg/m², which is also the maximum wing loading of the B-52. Using Wikipedia data, the maximum wing loading of the B-1B is even almost 1200 kg/m², but the published area is for the outer wing only, linearly extended to the center. If the large delta is added, the wing loading drops below 1000.

At the other end of the scale, typical glider wing loadings range from 30 kg/m² (without water ballast) to 55 kg/m² (with full water ballast). A typical GA airplane with a stall speed below 61 knots has 60 kg/m² to 70 kg/m², a TBM-700 can reach up to 180 kg/m² while jet fighters range between 300 kg/m² and 500 kg/m².

Next, the cruise missile needs to be stored, so it must be compact. In case of the Tomahawk, it is designed for the 21 inch torpedo diameter standard. The AGM-86 is mounted on a rotary launcher, and the trapezoidal fuselage cross section makes most use of the available space. Since it never needs a runway, the foldable fins can be arranged symmetrically for best control effectivity and to avoid cross coupling between yaw and roll. For maximum range the cruise missile stays out of the transsonic speed regime, so little to no wing sweep is needed. In the end, cruise missiles have a very straightforward and functional design.

AGM-86 on rotary launcher (picture source)

• Hi, Peter. The AGM-109 is mounted on a rotary launcher, and the trapezoidal fuselage cross section makes most use of the available space - Some notes: 1) Tomahawks are actually round, not trap. 2) The Tomahawk isn't air-launched from rotary launchers (it's only ship-, sub-, and [briefly] ground-launched( because... 3) The AGM-109 never saw service, having lost to the AGM-86B ALCM. The BGM-, RGM-, and UGM-109 served well. – Hephaestus Aetnaean Feb 3 '17 at 5:58
• They are designed to fly at one Mach-altitude combination only...For maximum range the cruise missile stays out of the transsonic speed regime 4) Some cruise subsonically but then use a supersonic terminal stage (eg, the Russian Klub). Others are purely super/hyper-sonic, but either their ranges are correspondingly shorter, or their weights are correspondingly massive. Soviet anti-ship missiles were in/famous for this (eg, P-700 Granit / SS-N-19 Shipwreck --- 7 tonnes, ramjet powered). – Hephaestus Aetnaean Feb 3 '17 at 6:25
• They are designed to fly at one Mach-altitude combination only...For maximum range the cruise missile stays out of the transsonic speed regime 4)  5) Altitude sometimes depends on mission and present range to target, sometimes starting high to increase range, gradually lowering to stay under the radar horizon, before popping up to dive onto the target at high speed. – Hephaestus Aetnaean Feb 3 '17 at 6:27
• ... the foldable fins can be arranged symmetrically for best control effectivity and to avoid cross coupling between yaw and roll... [for subsonic cruise] little to no wing sweep is needed. 6) Some tradeoffs are made to facilitate stowability and to reduce signature. The AGM-86 ALCM, AGM-129 ACM, and AGM-158 JASSM are some examples. – Hephaestus Aetnaean Feb 3 '17 at 6:48
• @HephaestusAetnaean: I am sure your answer would be so much better! Pity that you never wrote it. – Peter Kämpf Feb 3 '17 at 17:12

Airplanes are expected to land, refuel, and be reused.

Missiles are not expected to have the same life-cycle.

In fact, looking at certain Japanese Kamikaze planes (like the MXY7 Ohka, pictured) from later in the war, they more closely resembled missiles than traditional airplanes:

• Credit your image sources, please. The color picture looks like it came from Wikipedia – FreeMan Feb 3 '17 at 19:44