The shortest distance between U.S based missiles & the strategic cities of Russia/North korea—and vice versa—is via Canada over the North Pole. Any missile fired by North Korea at the U.S would most likely fly over the North Pole, undoubtedly passing through the Russian airspace.
The other route to avoid flying over Russia is via the South Pole (launching the missile down south) as displayed in the image above. During the Cold War, the Soviets employed the same technique, allowing the missiles to fly over south polar areas to reach the U.S as opposed to going over the North Pole, where much of the US’s early warning radar arrays are located.
Fractional orbit bombardment system (FOBS)
As the Soviets developed ICBM capabilities in the 1950’s & 60’s, the united states also constructed a Ballistic Missile Early Warning System (BMEWS), which employed radars to detect the incoming ICBMs via the north pole. These radars are located at three main sites along Soviet ICBM corridors: Clear Air Force Base, Alaska; Thule, Greenland; & Flying Dales, England.
The Soviets knew that the BMEW systems (soon after detecting ICBM launch) would give about 15 to 20 minutes of warning time for US bombers (like the B-52) to get off the ground and land-based ICBMs to be launched. The Soviets, therefore, developed an orbital weapon system called FOBS (Fractional Orbit Bombardment System) to attack the United States via the ‘backdoor’ i.e, via the South Pole and reduce the warning time to just a few seconds. FOBS would take out the ability to launch the retaliatory strike.
The reason a FOBS would go undetected is, the US at that time had no Ballistic Missile Early Warning (BMEW) radars facing south (all the radars were stationed towards the north). Therefore giving little or no warning of incoming FOBS attack.
Difference between an ICBM and a FOBS capable ICBM
ICBMs travel from continent to continent and follow a sub-orbital trajectory. They exit the atmosphere after being launched, spend most of their flight out of the earth’s atmosphere and re-enter back over the target. They reach apogee/altitudes of 800 to 1200 kilometers on normal trajectories.
Whereas in FOBS, ICBM are fired at a lower, less efficient angle i.e, in depressed trajectory (95 km-300 km) instead of normal optimum ballistic trajectory (800-1200km). The warhead is placed into an orbit (steeply inclined polar orbit) as low as 200 kilometers just like any other satellite. The only difference is, after the satellite placed into orbit circles the earth, where in FOBS the weapon is de-orbited before completing one revolution of earth and hence the name “Fractional”. The weapon system inserted into such an orbit consisted of a nuclear warhead and a de-orbit rocket stage shown in the image below.
Dropping bombs from space isn’t as simple as dropping from an aircraft. We need a propulsion system (like the de-orbit rocket stage) to bring it down from space. The FOBS Weapon system is much the same as a satellite revolving around the earth. Satellites stay up (without falling back to earth) because they move fast enough (29,000km/hr) to defeat the downward pull of gravity.
To force a FOBS weapon system out of earth’s orbit, a retro rocket (also known as braking rocket) is fired for one minute as it approaches the de-orbit entry point. Without such a rocket, the weapon would remain in orbit for years. But first, the weapon system must be re-oriented (for re-entry) and then the retro rocket’s fired to slow down and de-orbit the vehicle, changing the plane of flight from orbital to ballistic. The rest of the flight is the same as a normal ICBM warhead re-entering the atmosphere over the target. The reason we re-orient the weapon system in space is, the target rarely lies directly under the FOBS orbit path.
The main advantage of FOBS is that the enemy would be uncertain when the weapon would be de-orbited onto a target.
Note: ICBMs follow a sub orbital path, Space Rockets go orbital flight, and FOBS travel into partial orbital flight (85% of full orbit). FOBS is just a normal ICBM fired into a depressed trajectory but with an extra de-orbit rocket stage. A missile fired into a depressed trajectory would follow a low orbital path and be difficult for the US radar system to “see.”
How U.S negated FOBS threat?
When the Soviet Union carried out its first successful test of FOBS on Jan 25, 1967—at that time the U.S had the MIDAS early warning satellites, capable of detecting missile launches fired at the U.S from any direction (including over the Antarctic or the South Pole).
But MIDAS had problems, it gave false launch alarms as it couldn’t distinguish between missile launches and sunlight reflected off clouds. Also, because of launch and mechanical failures, the MIDAS satellites were unable to provide the desired continuous coverage of the Soviet Union.
The next generation of missile early warning satellites, called DSP (Defense Support Program), launched in the 70’s succeeded where MIDAS failed & completely removed the possibility of a surprise attack on the United States with ICBMs/FOBS.
Missile early warning satellites had extended warning time from 15 minutes (with BMEWS) to 30 minutes (with DSP satellites).
Note: All hot bodies emit infrared (IR) radiation. Missile early warning satellites carry infrared sensor or heat sensor to detect the hot plume coming out of the back of the rocket and locate its launch, direction of launch and even identify the type of missile.
The United States had no Ballistic Missile Early Warning (BMEW) radars facing south. So, in addition to the existing BMEWS radar stations at Alaska, Greenland, and England, a new phased array radar called PAVE PAWS, a cold war early warning radar was added at Beale Air Force Base in California (West Coast), and Otis AFB in Massachusetts (East Coast) as shown in the below in image, expanding angular coverage of the CONUS (Continental United States) and rendering the FOBS unusable in its original role.
Furthermore, the outer space treaty of 1967 prohibited the use of space for placing nuclear weapons into earth’s orbit. The Soviet Union claimed that the FOBS weapon system would never complete full orbit and continued testing with FOBS until it was banned under SALT ll (Strategic Arms Limitation Talks 2) negotiations in 1979.
North Korean EMP attack
In an ICBM, the guidance system is responsible for directing a missile during flight and does fine trajectory corrections. North Korea might have the ICBM range or the FOBS technology, but they lack the necessary guidance capability to deliver nuclear warheads with accuracy. (Here’s link to my article on Guidance systems)
An EMP attack doesn’t need accurate guidance systems because the area of effect is very large (maybe hundreds to thousands of kilometers) and an EMP explosion anywhere over the U.S could cause the same devastating effects. Also, for an EMP attack, you don’t need a re-entry vehicle or heat shield as the detonation is carried outside the atmosphere.
Here are some possible ways an EMP attack could occur:
1) using ICBMs 2) with FOBS 3) using Space rockets (4) and via satellites.
North Korea has experience of launching its space rockets down south. It launched two of its satellites KMS 3-2 and KMS-4 southward into an inclined polar orbit using a UNHA-3 space launch vehicle. Space launch vehicles (SLV’s) need not even be converted into true ICBMs; payloads could be inserted into a low earth orbit (say approx. 200km) and then brought down on their intended targets after orbiting a long way around the planet, similar to the Fractional Orbit Bombardment System (FOBS).
An EMP attack could also be made by a satellite in polar orbit, one which orbits around North & South Poles. A satellite that does nothing would be suspicious, so you’d have to stick a nuclear warhead inside an operational satellite: one that generates enough signal traffic to give a plausible explanation for its existence.
North Korea could make nukes small enough to fit on such satellites which pass over the U.S on a trajectory optimum for an EMP attack. KMS 3-2 and KMS-4 in polar orbits fly over the United States every day at an altitude of 500km which is an optimum height for putting an EMP field over all 48 contiguous United States.
The EMP commission warned that North Korea might even have a super-EMP weapon.
FOBS detection and interception
Early warning satellites can detect and track missile launches from almost anywhere in the world. So the North Korean ICBM launch or FOBS going undetected is highly improbable. Detection of ICBMs isn’t a problem, but the interception is.
Patriot, Aegis, and THAAD ballistic missile defenses aren’t designed to stop ICBMs. They are capable of countering only short, medium and intermediate-range ballistic missiles. The only system capable of defending the United States from a North Korean ICBM attack is the Ground-based Midcourse Defense (GMD) system.
There are currently only 44 Ground-Based Interceptors (GBI), with 40 located at Fort Greely in Alaska and the remaining 4 missiles at Vandenberg Air Force Base in California emplaced in underground silos.
GMD interceptor missile silo at Fort Greely, Alaska
GMD interceptors have succeeded in destroying the target in 10 out of 18 tests, which gives a 50% kill probability for each individual missile. With that 50% probability, if the U.S shot 4 interceptors at a single threat, it would have a 94 percent chance of taking down the missile (ICBM).
So with a total of 44 interceptors, assuming 4 per target, we can intercept only 44/4 =11 ICBMs.
The GMD interceptors at Vandenberg AFB (West Coast) counter ICBMs launched eastward from Pyongyang, while the North Korean ICBMs launched over the Arctic or the North Pole are countered by the interceptors in Alaska. North Korea launching ICBMs westward is most unlikely as it is opposite to the direction of the earth’s rotation.
There are no GMD missile interceptors currently facing South, making the Southern US largely defenseless against North Korean ICBM’s approaching the U.S via the Antarctic or the South Pole (like FOBS).
However, in the event of a conflict, the two North Korean satellites carrying the missile would be shot by a US Anti-satellite weapon (ASAT). But we actually don’t know whether the satellites are armed with nuclear warheads.
“On-orbit” inspection is one method for detecting nuclear weapons in orbit, where the suspect satellites would be subjected to neutron irradiation from an orbiting inspector satellite. Emission of delayed neutrons from the target would reveal the presence of fissionable material. While shielding a nuclear warhead might pose difficulties with inspection in orbit.
In conclusion, the US is at risk of being hit with a nuclear missile through an EMP attack from the south by North Korea because we lack GMD intercepters in the south. However, it is unlikely because the satellites carrying the missile would be shot down by a US Anti-satellite weapon. But we are more likely to be hit from the North because of the shorter distance from North Korea, via Russia, to the US.
Bachelor in Electrical Engineering, PGDC Thermal power (O&M) under Ministry of Power