11 August 2006

Smart Artillery Shells?

The Excalibur 155mm artillery shell is expected to be fielded by the Army in a few months, with an improved version expeccted to arrive two years later. It has been in development for a very long time, and they still don't work when its cold. The also don't live up to their promised accuracy:

The first Excaliburs, that will reach U.S. and Canadian troops this Fall, will have a range of 23 kilometers, and reliability of only about 75 percent.

This is far less than the Department of Defense was promised when the program began.

The pitch for the new shells, including the expected performance that R&D still hasn't been able to pull off, is as follows (paragraph breaks added for easier reading):

[A] new version of Excalibur will be ready, one with a range of over 35 kilometers (and eventually up to 60 kilometers). These versions will have reliability of over 90 percent. . . .

In the past, the army had lots of artillery fire power, but it wasn't very accurate. Infantry had to back off hundreds of meters before the bombers or guns could let loose on the enemy. If you didn't back off, you risked friendly fire casualties. . . .

The "dumb" shells can, at best, land with 75 meters of the aim point. Excalibur can hit within 15 meters, on the first shot, at any range. Infantry can use that kind of accuracy to stay close to the enemy, and quickly rush them after a smart bomb, or shell, has landed. Using Excalibur will also mean much less ammo will be needed, and there will be less wear and tear on the guns, and their crews.

While the first Excalibur shells going to the troops cost about $80,000 each, that price is expected to come way down, real fast. In five or ten years, the price of a smart shell will be under $5,000. That's still over ten times what a dumb shell costs, but the many advantages of smart shells make the price difference worthwhile.

Longer range, with greater accuracy, for tens times as much per round as the current "dumb" version sounds good. Don't cancel the project yet. Maybe R&D will make good on their promises this time.

But, how do Excalibur shells compare in cost and utility to comparable sized short range missiles like the Hellfire missiles used on the Army's Apache AH-64 helicopters, or smart bombs dropped from ground attack aircraft?

Both the Excalibur and the Hellfire have a similar sized explosive punch, about 100 pounds. "Smart" bombs are bigger, but the Air Force is hot to develop the "small diameter bomb" which would be about 250 pounds.

Hellfire missiles now cost about $100,000 each, a little more than Excaliber shells do now. In both cases, the bulk of the cost (this week's front page story in the Onion about the rising prices of rocket fuel notwithstanding), is in the guidance system. For what it's worth, "smart" bombs are expensive too, again due to the cost of the guidance system. Presumably, any decrease in cost for one system should be matched in the other systems to a great extent.

Back in the age before missiles had sophisticated guidance systems, and were called rockets instead, cannon based artillery was much more accurate than rockets. And historically, one of the reasons to have the big cannon barrel is to get greater accuracy.

Indeed, the same principle is one of the reasons that big long sniper rifles are more accurate than pistols. A long barrel makes it easier for a solidier's inherent clumsiness of perhaps +/- a millimeter in the case of a rifle or pistol, and more for a cannon, into a far smaller change in the direction that the business end is pointed. A millimeter change in the direction of a 150 mm pistol may make the difference between pointing it due North, and perhaps 2 degrees East. In a 3000 mm long gun, it may make the difference between point it due North and perhaps 0.1 degrees East. And, the better you point a gun in the right direction, especially at long ranges, the more accurate your shot.

But, this doesn't follow when the shell has a guidance system. A missile, delivered from a moving object buffeted by the wind, with no cannon barrel at all, is capable of being just as accurate as an artillery shell, so long as the target is within range, when both have similar GPS guidance systems. And, if the several dozen ton delivery system that is the long barrelled self-propelled howitzer isn't adding a whole lot of value in the accuracy department, the justification for the Excalibur starts looking more like intraservice politics (i.e. the cannon based artillery colonels want to keep their jobs and budget share within Army brigades and divisions), and less like a budget choice that makes military sense.

After all, when you buy a missile, you can use a pretty cheap delivery system. The canceled Crusader self-propelled howitzer, at about $24 million each, would have cost ten times as much as the vehicle now used in the multiple rocket systems of the Army, which cost about $2.4 million each. Basic, non-supersonic, non-stealthy ground attack aircraft designed to support ground troops are expensive, but not nearly as expensive as fighter aircraft optimized for stealth and air to air combat like the F-22 and to a lesser extent, the F-35. The cancelled Crusader vehicle (visualize a tank with a really long barrel and a trailer to carry extra ammunition), at about $24 million, wouldn't have been that much less expensive than a basic ground attack aircraft. The F-35 was originally budgeted to be in the $30 million a piece range, although cost overuns have changed that number for the worse. Take away some of the F-35 features not important when air to air combat isn't a major concern, and the price comes down.

Of course, right now we have more late model Paladin howitzers than we know what to do with, so this is a sunk cost. In contrast, we would have to buy new multiple rocket launchers or ground attack aircraft, at great expense, to replace that capability. So, for the short term (meaning until existing howitzers wear out), as a transitional measure, the Excalibur program may make good sense. You may get a lot more bang for your buck buying new and better shells, rather than new and better cannons.

But, as the Army looks ahead to the long term (the time frame of its so called "Future Combat System"), it isn't at all obvious that it makes sense to buy a big, heavy cannon based missile delivery system (and that it was a howitzer with projectiles of the Excalibur variety really is), rather than using a smaller and less sophisticated delivery system.

In the alternative, a comparably (to the self-propelled howitzer) priced aircraft that can be brought to the theater and moved from theater to theater more quickly, to deliver missiles with a similar impact, also looks attractive. As we move to an environment where two or three or more small wars at the same time, or the need to go to distant conflicts on short notice, seems more likely, highly mobile systems start to make sense. If you have to move projectile delivery systems by ship, you need one set of artillery in each combat zone. If you have aircraft, you can bring the same projectile delivery system from one battlefield to another in hours or days, eliminating the need to have a separate set for each conflict.

1 comment:

andrew said...

Seven years later the shells are more expensive or the same, not cheaper.