Forum: Modern Military Aircraft

I've noticed a pattern that air-to-air missiles are either longer for their width, or skinnier for their length, than air-to-surface bombs or missiles (ignoring fins & wings). AMRAAM, for example, is roughly the same length as a handful of much heavier air-to-surface weapons (1000/2000-pound JDAMs, JSOW, Naval Strike Missile) but about half or less of their diameter, while the air-to-surface weapons of the same diameter as an AMRAAM (small-diameter bomb, Hellfire/Brimstone/JAGM) are less than half as long. And compared to those small air-to-surface weapons, a Sidewinder is both narrower and longer, and a 500-pound JDAM is both shorter and thicker than either type of air-to-air missile. And the same comparison seems to hold for foreign air-to-air missiles, which are similar in size and proportions to AMRAAM and Sidewinder.

At first I thought it might be due to an aerodynamic reason such as reduced drag for the skinnier air-to-air missiles, related to flying versus falling, but some of the above air-to-surface weapons are also self-propelled missiles, not bombs. Could it be that even if they are missiles, their net-downward flight path is just easier, making more drag more acceptable?

Or could it be just a coincidence or accidental tradition or a back-compatibility issue, that at some time decades ago somebody designed an air-to-air missile that was skinnier than bombs and everybody since then has just stuck with it?

(There's a reason why I ask: what I see with stealth planes so far tells me that internal bays are easier to set up for long skinny weapons than for thick ones, which made me think of the idea of a bomb in the 350-500-pound range with size and shape close to AMRAAM's, to put in a spot that was designed around AMRAAM or its foreign equivalent. And picturing that just made me wonder why bombs so far have consistently been a different shape from that.)

F-16.net Sponsor

Typically an A/G weapon has a much heavier warhead, resulting in the need for a larger size.

The Aim-54 Phoenix is pretty thick. It also has a very big warhead for an A/A missile.

I was about to ask why, then, the same "short & fat" proportions still applied to even SDBs and JAGMs, but that question itself got me thinking of it as not one general rule but a convergence of two or more separate things: one reason for that shape among the big ones, and another or others for the little ones, just no single reason that applies to them all. Without trying to find a single overall reason for them all, I saw how simple it is. The heavy ones need to be thick in order to fit a reasonable length, JAGM and its predecessors were designed mostly for use by smaller vehicles on which a longer weapon would have been awkward, and SDBs needed to be short enough to fit pairs nose-to-tail where one big one would fit. Three different kinds of weapons, three different reasons not to be as skinny as an AMRAAM or Sidewinder.

Silly me. Embarassed

Wanna know something funny? When I first read about the SDB being designed to fit in the F-22's weapons bay (some 10 years ago), I actually thought it was going to be a long, skinny bomb that would match the AMRAAM's footprint... hey. If one was to build a "square tube" shaped weapon like that with folding fins/wings, a Raptor could carry six of the things in addition to its brace of Sidewinders. Of course, there's the small matter of how much said weapon would weigh (I have no way of guessing); anything less than 1K wouldn't really justify the expense of development.

Yeah, it's dumb idea, but I'll through it out there in the hope that someone will debunk it with a detailed technical explanation.

On the weight of the kind of weapon we were both thinking of: it would be exactly the same frontal silhouette as an SDB but slightly over twice as long, so slightly over twice the volume, so between 400 and 600 pounds at similar density. It would also be comparable in length to JSOW but with 7/13 of the width & height, so 49/169 (about a third) of the weight at similar density (which would put it between 300 and 400 pounds), but JSOW is less dense than usual for bombs, so we can increase that estimate for the fictional weapon, which allows agreement with the original estimate of over 400 pounds. I originally aimed low and called it 350-500, not only because of the lower estimate based on JSOW without accounting for different densities, but also because, if such a bomb were invented, part of its reason to exist would presumably be for use in an F-35's internal AMRAAM spots, which have a weight limit of 350 pounds. (Which is an intriguing limit, since the missile they're putting in there doesn't weigh that much.)

Part of what made me think of the idea of a long skinny bomb is F-15SE, which seemed at first to only be set up to carry air-to-air missiles internally. The pictures don't show anything else and don't make it look like there's extra space for more than that.

But since then I've found a layout of its internal weapon options; apparently each of its four bays is equipped to carry either an air-to-air missile, or two SDBs, or a 500-pound JDAM (which is less than two inches wider than an AMRAAM at its widest point, but still more than I had thought could fit based on pictures and with the missiles being mounted on those little moving parts)... and two of the bays (which must be the lower ones, based on the color image on that same page) could take a 1000-pound JDAM apiece (which is amazing to me because their diameter is twice an AMRAAM's). That allows combinations like 4 JDAMs, or 2 JDAMs + 4 SDBs, that even an F-35 can't carry internally! (At least without some kind of adapter that hasn't been invented yet.) So no such special new long skinny bomb would be especially needed there.

And the other "stealth" planes I was thinking of are either foreign prototypes or only unbuilt plans/drawings, so available impressions of their bay sizes & shapes are not high on detail and certainty.

Forum: Modern Military Aircraft

Length/width ratios for A-to-A and A-to-S weapons