
Military technology: Magic bullets - robinhouston
http://www.economist.com/node/21542716?frsc=dg%7Ca
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sbierwagen
Ah, the XM25. Last publicity blitz we saw on this was a year ago, and Gary
Breacher called them out on it: [http://exiledonline.com/xm25-gee-whiz-how-
can-we-be-losing-w...](http://exiledonline.com/xm25-gee-whiz-how-can-we-be-
losing-with-such-cool-stuff/) (Even the file photo is the same!)

The XM25 autocannon is neat. Absolutely nobody denies this. It's also pretty
useless, because any insurgent who engages security forces in a conventional
gun battle is going to die. Nine times out of ten, they're dead; if by
airstrike or just being outflanked and outgunned.

They know this, which is why for the last nine years, the weapon of choice
used by the other side has been the IED or the suicide bomb; where high tech
weapons like the XM25 are rendered entirely useless. While it's nice to see
the Economist running an advertisement for Alliant Techsystems in their
magazine, the XM25 will actually do very little to win CI wars.

~~~
nhangen
That's not entirely true. There are still plenty of gunfights and ambushes
being staged in Afghanistan, especially outside of the major cities.

~~~
mjwalshe
yes its just a replacement for the existing under barrel launchers M203 and
the venerable Vietnam era M79 this gives that gives you a few more tactical
options.

~~~
electromagnetic
"A few more tactical options" is playing down something that can be
monumental.

The howitzer only offered "a few more tactical options", mainly being the
ability to lay down accurate indirect fire whilst still being able to offer
direct fire and defensive fire.

I mean why bother inventing gunpowder or rifling or any other weapons when an
arrow killed people too. I mean sure the rifle was more effective and less
competent soldiers could use it skilfully, but what was the point when we
already had bows and crossbows?

So why bother inventing an accurate method of firing a frag round at 500ft
when the M203 has a max range of 400ft and effective fire at only 150ft.
Granted the AK47 is only effective at 250ft, but that still means the soldiers
will be spraying and praying with grenade fire.

The whole point of making a weapon more accurate and effective is to increase
the enemy combatant losses whilst decreasing civilian losses and soldier risk.

~~~
schraeds
The American battle rifles aren't a weakness, they serve their purpose well.
The military should be focused on things like IED detection, preventing brain
damage from concussive force, battlefield intelligence, social programs
(hearts and minds)... the stuff we are having a hard time doing.

~~~
nhangen
The M4 is accurate, but lacks the power of something like an AK-47, which hits
harder and has a larger round. It's great for clearing a room or working in
tight spaces, but it's not nearly the same as this.

Additionally, they are working VERY hard to improve IED detection, and in fact
are making quite a bit of headway in that regard. The same goes for every
other issue you raised.

There's no reason you can't improve offense while simultaneously improving
defense.

~~~
electromagnetic
Improving offence helps you improve defence. If you make the most dangerous
weapons in the world, then you solely have the ability to figure out the best
ways to defend against them.

The US will have a significant advantage in developing jamming systems against
these types of rounds.

The US isn't afraid of some Afghan insurgent living in a cave from developing
a countermeasure against these new munitions. They're afraid Russia or China
will be capable of developing a countermeasure. The rounds are worthless, or
potentially dangerous, if you can cause premature detonation.

------
jgrahamc
My stab at how the bullet measures its own rotation:

Suppose the bullet leaves the muzzle rotating at 300,000 RPM (quite reasonable
for a rifle). That is 5kHz. It's easily within the capabilities of a Hall
Effect sensor to measure a 5kHz rotation and so I'd make the very centre of
the bullet contain a free rotating magnet. The rifle itself sets the magnet
spinning at some known rate opposite to the rifling. When the bullet leaves
the rifle it is able to measure the time between detections of the magnet and
given the known rifling, the known magnet rotation speed it would be able to
calculate rotations.

Alternatively, the inner magnet could be spinning in the same direction as the
rifling but faster and detect complete rotations of the bullet. Either way I
think Hall Effect + spinning magnet at bullet core would work.

Also, 5kHz is well within the operating range of a micro controller so this
wouldn't need much computer power. Lastly the article says that the weapon is
accurate at 500m and that the shrapnel kills everyone within a few meters.
Also says that the soldier estimates the target distance.

That sounds like there's plenty of room for the measurement to be not too
accurate. Suppose 'several meters' is 5 then you can get away with an error of
1% or so.

~~~
regularfry
I suspect it would be easier to make the front spin and fin-stabilise the rear
than try to make a rotating core. That being said, given a known muzzle
velocity I don't understand why it's not a simple timing problem.

~~~
sbierwagen
Muzzle velocity varies quite a lot based on ambient temperature, air pressure,
altitude, and propellant grain size.

~~~
regularfry
Ah, so knowing the muzzle velocity might actually be a red herring - the turns
per metre travelled is going to be a more stable metric.

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Sharlin
Nitpicking a bit, this is a grenade launcher, not a rifle. Explosive 25mm (or
40mm!) rounds are grenades, not bullets.

~~~
humbledrone
The article says that the grenade's travel distance is measured by counting
its rotations, implying that the barrel is, in fact, rifled. (Maybe that
doesn't technically make it a rifle, but it doesn't seem like a terribly
inaccurate term.)

~~~
Sharlin
Technically true; however, in practice, you _must_ rifle the barrel of any
grenade launcher, or else have tail fins on the grenades to prevent
aerodynamic tumbling. Tank guns, cannons, howitzers, and the like typically
have rifled barrels but we don't call them rifles. (Mortars, on the other
hand, use finned ordnance.) AFAIK rifles are usually defined to have a caliber
at most 20mm.

~~~
arethuza
I thought that tank guns these days are usually smoothbore rather than rifled
- with the notable exception of the British Challenger 2:

<http://en.wikipedia.org/wiki/Challenger_2>

~~~
tsotha
The British have been trying to replace that rifled gun with the German L/55
smoothbore, too, but they don't have the money. It wasn't clear at the time
the tank was designed, but the rifled barrel turns out to have been a mistake.
The round for which it was primarily designed (High Explosive Squash Head, or
HESH) hit a sort of technical dead end with the introduction of spall liners
and layered composites in tank armor.

Read the comment by Steven Den Beste, who explains the situation pretty well
(aside from getting the HESH acronym wrong):

[http://www.professorbainbridge.com/professorbainbridgecom/20...](http://www.professorbainbridge.com/professorbainbridgecom/2010/01/challenger-
v-abrams-who-wins.html)

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dimitar
$25 bullets and $25000 rifles are insanely expensive. And I don't see how
better rifles will bring an advantage - most coalition casualties are from
mortar fire and improvised explosive traps - rebels have already lost
preference for gun standoffs. But I'm sure H&K and Alliant will love to sell
lots of these to whatever army is corrupt enough to buy them.

Also... aren't exploding bullets illegal under the Hague convention?

~~~
icegreentea
The Hague forbids bullets that expand on penetration, on the basis that it
creates larger and more traumatic wounds. This round acts more like a grenade.
It explodes (and wounds/kill by shrapnel) near the target. It shouldn't
actually hit the person. Completely different class of weapon. It's more
accurate to call this a grenade launcher than a rifle.

~~~
grannyg00se
It always seems so absurd to me that there are rules around wartime killing.
Once you acknowledge that it is acceptable to take another person's life for
profit you really have little credibility for laying out rules of fairness.

~~~
icegreentea
Well, most of the rules aren't about killing per se, but rather wounding. And
most of the rules are in place so that the stakes of fighting never gets high
enough that we would all have to stop fighting. For example, the Geneva
Protocol that bans chemical and biological weapons pretty much because aside
from killing, those who were wounded were an enormous burden, and terrible for
morale (aside from any ethical reasons).

In that case, losing the ability to use those weapons was deemed to be
outweighed by the consequences of having to deal with them being used on you.
Also, since they could be potentially huge and unpredictable force
multipliers, it made war all the more predictable, which is good from their
perspective.

Long story short, nearly all rules of war exist because they are beneficial to
abilities of the parties to conduct war. The rules do no exist to make killing
fair. They exist so that parties may conduct war in a way they agree with.

~~~
grannyg00se
"Long story short, nearly all rules of war exist because they are beneficial
to abilities of the parties to conduct war. The rules do no exist to make
killing fair."

That actually makes perfect sense. Although I find it rather disturbing.

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ilaksh
In this era of global mass instantaneous communications, every citizen of
every country is our neighbor. There is no excuse for the continued existence
of this disgusting military industrial complex.

The only things keeping this going are racism, ignorance or misperception
fueled by propaganda, and a sick, inhuman and outdated Social Darwinism.

We just cannot permit criminals and thugs to continue to have control.

------
__alexs
Surely it's just a 1 axis accelerometer and perhaps a lookup table or some
basic maths?

The military sure do like to make themselves seem important. Super secret
alien assault rifles being attacked by unspecified hackers from unknown
locations. Yep, better keep funding new and exciting ways to kill people.

~~~
gvb
No. An accelerometer measures _change_ in acceleration.

When the round is fired, it will experience a _huge_ acceleration from the
propellant along its axis plus a very large rotational acceleration as the
rifling spins the round from 0 revolutions per second to a large number of
revolutions per second.

Once the round leaves the barrel, it is falling at a constant acceleration
(9.8m/s, freefall, 0G, "weightlessness"), so it will not be able to measure
the earth's gravitational force. It also will be spinning at a constant rate
because there is no outside force increasing or decreasing the spin rate, thus
no rotational acceleration. While there will be acceleration due to the
centripetal effect of the rotation, that acceleration is constant and thus not
usable with an accelerometer for counting revolutions.

~~~
gvb
I got it wrong in my first sentence - in order for an accelerometer to be
used, there has to be _changes_ in acceleration proportional to distance
travelled. Per the rest of the discussion, there isn't any.

~~~
robotresearcher
You still have it wrong. An accelerometer measures acceleration.

Users usually calibrate the device at rest to get a good estimate of G so that
it can be subtracted from accelerations measured later. Is that what you mean?

~~~
gvb
No. A falling object is at "0G", it is "weightless" (in a "drop seat" type
carnival ride, when the ride triggers, you have no force on your butt). A
bullet is a falling object after it leaves the gun. You cannot measure earth's
gravitational attraction from the bullet's frame of reference because it is 0.
Therefore, you cannot use earth's gravitational attraction to measure the
bullet's spin rate because the value is zero, and zero has no direction
information.

~~~
robotresearcher
Sure, once the bullet is moving ballistically you can't measure G. My argument
was with the statement that accelerometers measure changes in acceleration.
They don't.

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ck2
I guess our economy will never completely bottom out as long as we can export
death.

Just wait 'til your local police get these for "domestic terrorism crowd
control" (aka protesters) with the shrapnel replaced by "less lethal" rubber
bullets while drones fly overhead for more accurate targeting.

Oh it would never happen, right? What if a congressman owns stock in the
company?

~~~
GFKjunior
ATK contributes large amounts to politicians. They spend millions on lobbying
and hundreds of thousands on individual PACS.

[http://influenceexplorer.com/organization/alliant-
techsystem...](http://influenceexplorer.com/organization/alliant-
techsystems/5d9b2621e7974bccadf150adf3334de7?cycle=2012)

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antihero
Ah, humanity, always figuring out better ways to murder other humans.

~~~
awakeasleep
Yep. It'll be great for this company once the regulations are loosened and
they can begin selling to all the countries onnafrica, the middle east,
western Europe, and Asia. Bad for everyone else though.

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TomGullen
Sounds like a good way to counter this sort of weapon would be to have human
shields. I'm not sure if that's an improvement on the situation if they start
to adopt those sort of tactics.

Enemies will simply adapt to new weapons they face. Much like a bucket of
paint would be quite effective against and remote control mini tank.

Whilst the engineering feat is impressive, it is still important to note that
at the receiving end of such ingenuity is a writhing half dead corpse so it is
with hesitation I would ever celebrate such innovation.

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domwood
It's a grenade launcher, not a rifle. (you can have rifled barrels in a
grenade launcher, doesn't make it a rifle) and a TOT detonation's hardly the
most amazing thing ever. It's just another example of mobile infantry
artillery, it's expensive and it's just another horrible way to die.

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kkartik
Am I the only one horrified by both the technology, and the general apathy to
the moral implications of military tech in the comment thread.

~~~
Sukotto
The morality is in deciding when it is worth ending a human life. What tool
you use is a distant second, at best. In war, once you have decided to kill a
person, the moral course is to kill them as quickly and effectively as
possible. Preferably with as little pain as possible.

The tools are horrible, because war is horrible. If you're opposed to their
use, you need to act at the political level (to stop unnecessary war from
happening) or the strategic level (to win the conflict in a way that does not
require direct, physical confrontation)

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Tycho
Regardless of the tactical implications of this particular weapon... the fact
they're now making computerized bullets makes me wonder where else this path
will lead.

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Freestyler_3
But if they move you have to restart :\

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mikemoka
Smart bullets, that is the best oxymoron I heard in my whole life.

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Generic_Name
Well it works well enough in modern warfare 3, though slightly noobish...

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zackzackzack
Wonder how long before people the article: "The gun that fires computers with
bullets in them" or something to that effect.

~~~
jsh2134
price of those bullets reminds me of Chris Rock's bit on gun control
<http://www.youtube.com/watch?v=OuX-nFmL0II>

