Friday, October 30, 2009

UAVs vs cruise missiles

I was attending a presentation yesterday and they had a bullet about how using UAVs on a carrier to strike targets would provide cost savings over cruise missiles. My gut said "really?".

So I did some quick analysis about that issue during the presentation.

The assumption is that you wanted 1000lbs of explosive delivered to a target and that you want to maximize the deliveries per dollar spent. Assume you already have a carrier and personnel. Costs are procurement cost for the cruise missile (BGM-109 Tomahawk @ $569,000) or the procurement cost of an F-18E or F-35 ($54,700,000 and $83,000,000 respectively) plus the cost of a bomb (GBU-31 $73100 (MK-84 $3100 + JDAM Tailkit $70,000)) for each use. These costs are from wikipedia and may not be accurate. Feel free to substitute your own numbers. (I for one, do not trust the F-35 data, but I digress) (I used numbers off the top of my head during the presentation, they were fairly close to these numbers)

Assumption: Cost for a carrier UAV will be comparable to a F-18E or F-35. Again, the numbers aren't terribly important, we are just trying to get a feel for how it works

Assumption: ~1000lbs of explosive delivered by a Tomahawk is roughly equivalent to ~1000lbs of explosive delivered by a JDAM. Therefore, we will find the cost for the same # of deliveries.

Assumption: ~80 Aircraft per carrier (could be more or less)

[Cost for Tomahawk option] = [Cost per Tomahawk]*[# of deliveries Tomahawk]
assume: There is enough room for all of the Tomahawks on a carrier (may not be true).

[Cost for UAV option] =
[Cost per aircraft]*[number of aircraft on a carrier] +
[cost per JDAM]*[# of deliveries UAV+JDAM]

Setting the costs equal to each other (so that we can know the "tipping point" where it is better to switch from uav+jdam -> tomahawk or vice vera) and # of deliveries too, we find that that occurs when
[# of deliveries] = [cost per aircraft]*[number of aircraft on carrier]/
([cost per Tomahawk]-[Cost per JDAM])
And [Total Cost] = [#deliveries]*[cost per Tomahawk]

Using the provided numbers,
[# of deliveries low uav cost] = 8825
[# of deliveries high uav cost] = 13390
(note: Original estimate in presentation was 8000-16000 (low-high), so back of the envelope works)

So, going mid-way, about 11,100 deliveries for equal cost. If there are more than 11,100 deliveries wanted per carrier, then we should go with UAV+JDAM. If we envision less than 11,100 deliveries per carrier, then we should go with the Tomahawk. (based on all assumptions, and hand waving away all other things like storage cost, personnel, range, surge sortie rate, etc)

For comparison, if all of the tonnage dropped in Desert Storm was 2000 lb bombs, that would have been 121,248 bombs (not sure I did that right, I considered 1000lb of explosive, but I think it needs to be normalized to tons of TNT?). That would mean about 10.9 carriers of that load.

I don't think that you can fit 11,100 Tomahawks on a carrier, but I think it might be able to handle the weight (not spending time to find out).

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