The Navy (and US military, in general) has latched on to
hypersonic weapons and, as is typical of the Navy, with absolutely no
supporting evidence or testing that demonstrates that hypersonic weapons will
be effective enough to justify their cost and other negative impacts. We touched on this in a previous post (see, “Conventional Hypersonic Prompt Strike Missile”).
Speaking of cost,
Based
on internal Defense Department estimates on the number of weapons planned, that
amounts to about $106 million per missile for the Army and $89.6 million for
the Navy.[1]
One time use missiles that cost a hundred million
dollars! How can that possibly be
justified?
Here’s a cost for integrating – not producing! – hypersonic
missile components:
Lockheed
Martin won $347 million to integrate at least eight of those glide bodies with
guidance systems, rocket boosters, protective canisters, and so on, arming a
battery of four Long Range Hypersonic Weapon (LRHW) launchers.[2] [ed. = $43M
each]
The 2021 GAO Annual Weapons Assessment report cites a
program cost of $3.96B ($FY21) for a quantity of 11 missiles ($360M each)
without specifying what’s included in the cost.
While there are no reliable unit cost figures for hypersonic
weapons, yet, it is clear that they’re going to be very expensive. The first reference, citing a cost of $90M
per missile for the Navy, is the most authoritative estimate that I’ve been
able to find.
Now, with that kind of staggering cost in mind, how do we
justify hypersonic weapons?
Well, one way would be if the destructive effects were
several levels beyond devastating - a near nuclear bomb level of destructive
power from a single weapon. However, the
destructive effects are nowhere near that level. They will either depend on kinetic energy
alone or use a conventional warhead which limits the size of the explosive
power to conventional levels although that would be added to whatever kinetic
effects there are.
As we’ve repeatedly demonstrated via calculations, kinetic
energy, alone, is rarely sufficient to produce a useful destructive force. Kinetic energy is also a tricky phenomenon to
effectively harness. For example, the
bullet through paper analogy that I’ve often cited renders kinetic energy
unusable. Even when a physically
substantial target is hit, the kinetic energy is likely to be gradually
released (on a relative time scale) as opposed to the instantaneous release
from a conventional explosive. The gradual
release ‘dilutes’ the destructive effect of the kinetic energy
release/conversion.
Here’s an illustrative example of the kinetic energy effects
of a hypersonic weapon. The data is all
speculative as there are no publicly available specifications, that I’m aware
of.
Mass of common glide body = 900 kg
Velocity = Mach 5 = 3800 mph = 1699 m/s
k.e. = 0.5 * mass * (velocity)squared
k.e. = 0.5 * 900 * (3800)squared
k.e. = 1,299,000,000 J
By comparison, a kg of TNT releases 4,184,000 J. Thus, the hypersonic weapon is equivalent to 310 kg of TNT (683 lb). A Tomahawk
missile has a 1000 lb conventional warhead so a hypersonic weapon would be
equivalent to less than 1 Tomahawk missile.
That’s substantial, to be sure, but it’s nothing approaching near
nuclear bomb type of destruction.
Of course, if the warhead is heavier or lighter or the speed
is greater or lesser, that would change the calculation.
The point is that while a weapon that is equivalent to one Tomahawk missiles is potent, it does not justify a hundred million dollar price
tag when that hundred million dollars could buy 50 Tomahawk missiles.
We’ve discussed in previous posts that kinetic weapons (no
explosive warhead) depend on the transfer/conversion of their kinetic energy
into thermal energy and resulting shock/pressure effects. In order for this to happen, the kinetic
projectile must encounter sufficient resistance to quickly and efficiently
transfer/convert the kinetic energy.
This is the bullet/paper problem: a bullet (lots of kinetic energy)
fired at a piece of paper, will do very little damage, leaving only a bullet
size hole as it passes through the paper and the paper will emerge virtually
undamaged because the paper offers insufficient resistance to transfer/convert
any of the bullet’s kinetic energy to the paper target. Similarly, a hypersonic kinetic projectile
that encounters a soft target like a ship will likely pass through, causing
relatively little damage. Conversely, a
substantial, solid target such as a concrete bunker, fortification, or hardened
aircraft shelter will offer sufficient resistance to facilitate the energy
conversion and the target will be destroyed.
Closely related to this resistance problem is that a
hypersonic missile will release/convert its kinetic energy slowly as opposed to
a conventional explosive, such as a Tomahawk missile, which releases its energy
instantaneously. When you see videos of
rail gun projectiles impacting targets, the targets are, invariably, steel
blocks multiple feet in thickness and the projectile produces an impressive
fireworks display. However, how many
real world targets consist of steel blocks a few feet thick? A hypersonic body impacting a real world
target, such as a building, is likely going to penetrate straight through the
target, releasing/converting only a portion of its energy. The remainder will be released/converted in
the ground as the body continues to penetrate until it stops. In fact, the body might well pass straight
through the building, leaving only a small hole, and bury itself in the ground
(the bullet through paper analogy). What
effect that underground release/conversion of energy would have on the above
ground structure/target is unknown. I’m
not aware that anyone has done any realistic testing of hypersonic weapon
destructive effects. We desperately need
realistic testing before we continue down the staggeringly expensive hypersonic
weapons path. It’s going to be very difficult
to justify a hundred million dollar, one time use weapon.
A final consideration about target sets is that the
hypersonic missile inventory will likely be quite small.
The
[Pentagon] internal assessment, made available to Bloomberg News, shows an
expected total of … 240 missiles for the Navy.[1]
Thus, we have to not only take into account the cost of a
hypersonic missile but also the inventory level. With very few missiles, we can’t waste them
against anything but extremely high value targets. We also can’t waste them against heavily
defended targets.
Moving on, we’ve noted that hypersonics have a fairly
limited target set. With no guidance
package, they can only be used against fixed targets. In order to effectively release/convert their
kinetic energy, the target has to be physically substantial. Even a ship is likely to see a hypersonic
weapon pass straight through (this phenomenon was seen often in WWII when large
caliber, armor piercing shells would pass straight through a smaller target
ship, causing very little damage.
What does all of the preceding tell us about the hypersonic
weapon target set? It tells us that
valid targets must be:
Fixed targets since hypersonic weapons don’t have guidance packages
Extremely high value targets to justify the cost
Physically hard targets to trigger an effective degree of energy release/conversion
Less defended so as not to waste expensive missiles
This excludes:
Area bombardment / suppression fire
Mobile targets
Physically soft targets such as trucks, tanks, artillery, aircraft, most buildings
Heavily defended targets
Now, let’s consider how many real world targets fall into
the valid target set? The answer is …
not many. Examples might be a very large
headquarters building, hardened aircraft hangars, underground bunkers, nuclear
missile silos, and Chinese submarine pens built into mountains. Even within this set, some of the potential
targets are questionable. For example,
is it really cost-effective to destroy a hardened aircraft hangar with a
hundred million dollar missile as opposed to a couple of Tomahawks?
The harsh reality is that the vast majority of targets are
not valid hypersonic weapon targets.
These would include trucks, tanks, artillery, people, ships, aircraft,
radars, and almost every worthwhile target one might find on a
battlefield.
Thus, hypersonics would seem to be more a one-shot, sniper
type weapon for use against very high value, very constrained targets rather
than a general warfare weapon.
_____________________________________
[1]Bloomberg website, “Hypersonic Sticker Shock: U.S.
Weapons May Run $106 Million Each”, Anthony Capaccio, 12-Nov-2021,
https://www.bloomberg.com/news/articles/2021-11-12/hypersonic-sticker-shock-u-s-weapons-may-run-106-million-each
[2]Breaking Defense website, “Hypersonics: Army Awards $699M
To Build First Missiles For A Combat Unit”, Sydney J. Freedberg Jr.,
30-Aug-2019,
https://breakingdefense.com/2019/08/hypersonics-army-awards-699m-to-build-first-missiles-for-a-combat-unit/