ICBMs or Intercontinental Ballistic Missiles, have been the iconic image of the cold war since their creation in the late 1950's. They are the natural extension of technology developed by Nazi Germany during World War 2 and further developed by the allies post-war.
Various nations field a variety of designs. The United States primarily have the silo-launched Minuteman missiles for example. There are submarine equivalents called Submarine-launched ballistic missiles, SLBMs, which have similar ranges to ICBMs. Notable examples include the Trident missile system in use by the United Kingdom.
In the following article, we'll take a quick overview of just how ICBMs work. A detailed analysis of the workings of such weapons is not possible, as you can imagine.
What is an ICBM?
On a very basic level, these missiles work by launching from a ground-based launcher, reach Earth's orbit in space and re-entering Earth's atmosphere as they plummet towards their target.
Thankfully, to date, no ICBMs have ever been fired in anger. Despite this, some countries have tested missiles for trial runs according to Philip Coyle. Philip is a senior science advisor to the Center for Arms Control and Non-Proliferation. They are a nonprofit organization based in Washington D.C.
ICBMs work, as the name suggests, by carrying a payload large distances, such as between continents. What the name does not detail is the fact that they can enter low Earth orbit en route to hitting their target. Most will travel over a very long parabola, much like a thrown ball through the air. Just like a ball and ICBM can be launched at any angle of attack.
"They fly straight up against the force of gravity and come down some distance from North Korea … If they're long-range, [the North Koreans] usually drop them on the other side of Japan, which, of course, makes Japan very nervous."
What is important to note is that countries, like North Korea, wouldn't aim ICBMs straight up during an actual attack. Missiles would be aimed towards their intended target. North Korea's Hwasong-15, traveled 1,000 km from its launch site but could travel a lot further.
Some believe it could travel at least 13,000 km from its launch site over a standard trajectory. This, according to a Nov. 28 blog written by missile expert David Wright.
Of course, any distance an ICBM will travel depends on its total weight. 'Dry runs' like the recent North Korean launch will travel further than a 'live' one weighed down with a bulky nuclear warhead.
ICBM launch phases
ICBMs are multi-phase rockets and will go through a preset sequence of events prior to the rocket reaching its target. At takeoff, the ICBM goes through what is called the boost phase. The American Minuteman III ICBM, for example, has a three-stage booster.
During the boost phase, the rockets get the missile airborne. This phase lasts around 2-5 minutes until the ICBM has reached space. ICBMs can have up to three rocket phases with each one ejected, or discard after it burns out.
Rockets tend to be fuelled by either liquid or solid propellant. Liquid fuel rockets tend to burn longer in the boost phase than solid ones according to Coyle. Solid ones, however, "provide their energy in a shorter amount of time and burn faster."
Both liquid and solid fuels can send their rockets equally as far. "But most countries start out with liquid propellant technology because it's well understood," Coyle said. "[As] they graduate, they move to solid propellant to get the faster burn times. It also avoids the hazards of dealing with dangerous liquids that are both flammable and toxic."
Getting up to speed
The second phase of the ICBMs journey is the point where the rocket has reached space. Here it continues along its ballistic trajectory. At this point, the rocket will be traveling very fast indeed. This could be anywhere from 24,140 and 27,360 km/h. This is the stage where the ICBM achieves its greatest speeds.
Such speeds are achieved due to the lack of air resistance in space. Some ICBMs come equipped with to allow them to take a 'star shot'. This lets them use the location of stars to help them orient themselves towards their target, according to Coyle.
The third and final phase sees the ICBM final separation and re-entry into Earth's atmosphere. The nose cone section carrying the warhead separates from the final rocket booster, orientates itself, if needed, and 'drops' back to Earth.
At this point, the ICBM is just minutes from its target. If the ICBM has rocket thrusters these would be used at this point to orientate itself towards its target. Some have more than one warhead per ICBM too.
Countdown to destruction
As you'd imagine it is vitally important that ICBM's have adequate heat shields to survive re-entry. If not they would burn up and fall apart.
North Korea's Hwasong-15, had a total flight time of around 54 minutes according to Wright's blog. This is significantly longer their previous 37-minute test flight on the 4th of July. As well as its 47-minute test flight on the 28th July 2017.
"We all have tested them to show we can do it, [which is] exactly what North Korea is doing now. [But] we've never actually used them in war, and the reason is it would be all-out nuclear war and we'd all be dead," said Coyle.
It's also important to note that American and Soviet manned space mission used modified ICBMs as launch vehicles.
So in a nutshell that's how an ICBM works. Did you already know? Are you concerned with the advancements being made by North Korea? Let us know in the comments below.