ABM: Under The Dome – Safeguard

U.S. ABM system still fail tests.  No dome of protection from current ABM choices?

Another test of our  antiballistic missile defense system this last June;  it failed again.    AviationWeek&SpaceTechnology, began its coverage with “another test failure casts doubt …”  Yahoo News reported that the June’s launch was the 16th test of the new intercept hardware, of which 8 have worked.  This is different from:  the 8th successive kill of an incoming warhead in 16 tests.

click for list of our other ABM posts

This post is the first of several planned to review what has been done in American missile defense efforts.  This is what we cover, this post —

  • We start with an overview of why we try to do missile defense; basic ideas and terms used in this effort.
  • Discuss discussion of the Safeguard system,  our first (successful) attempt to provide ABM (Anti Ballistic Missile) interceptor protection.

Click any image to see  its expanded form.  Other posts discuss the current confusing situation, and why we are proceeding the way we are.

ABM issues form a shifting field of study


Fig 1   15 kT test, 1953

Attack missiles are usually divided into categories, as shown in this table.  They describe the distance between the target and the launch point;  but notice that the missiles range from relatively short range and slow to transcontinental and nearly orbital speeds.

A payload will range from high explosive (hundreds of equivalent TNT-kilograms) to thermonuclear (millions of equivalent TNT-tons), Fig 1.  It makes sense to work to assure one does not drop in on us.

Acronyms- Attack missiles

Acronyms_ABM_txtIt is hard to mount a good missile defense —  even if you had 10 to 30 minutes to prepare, how would you stop the warhead from arriving at over 10 thousand miles per hour?

When is the best time to stop the attacking missile?  During the rocket’s  initial launch (boost phase)?  Here it is  a slow, compact target at its most vulnerable . Or, after the engines have been shut down and the payload is coasting through its trajectory (midcourse ballistic phase)?  For long range missiles, this is the longest time the reentry vehicle is available to attack.  Or, during the terminal phase, its reentry just seconds before it strikes? This is when it is moving fastest, but all aids

The table show the current categories for  ABM techniques.  MDA was recently changed from NMD, because mobile systems from the Army and Navy are becoming competitive to silo-based multi-staged rockets that the agency actually directs.

TBMD recently changed its  T to stand for Terminal,  because the military’s rockets all are meant to kill the attacking missile during re-entry, the final, terminal part of the ballistic trajectory.

The frequent  shifting of words indicate an instability in ABM strategies. For example, when was the last time the categories  battle tank and aircraft carrier were changed?  The ABM situation will remain in flux until a functioning system has finally been devised.

MCTR controls how international rocket sales done.  MCTR criteria indicate when ABM sales are legal, and were used against India some time ago.

Safeguard  ABM Shield

We start with our  historical ABM system.  Safeguard was developed in the 1960s, tested in 1971, and installed to guard our North Dakota ICBM field in 1976.  Safeguard was deactivated 4 months after dedication.  There is a lot of political manipulation that we will not go into here, though Wikipedia has a nice description.   In case of attack, Safeguard would have worked as designed.


Fig 2   Nike Zeus-A test

In the 1950s, the successful Nike system (N-Ajax and N-Hercules) was developed to protect against bombers.  Nike Hercules were distributed all around the world.  In 2013, the last  installations are being dismantled (60+ years later).  The Nike Zeus was to do the same for missiles, but as it turned out, attack missiles are too complex for a simple Hercules-like solution.  Fig 2, courtesy US Army, shows a Zeus-A launch at the Kwajalein testing island, early 1960s.

The kill  task was split into parts, a midcourse interceptor to remove most of the warheads and a terminal phase interceptor to remove the reentry vehicles that slipped past.




Fig 3   Spartan on display in North Dakota

The Zeus-A was not up to the designated job and quite a different -B model was designed.

Ultimately, the Nike Zeus-B become the LIM-49A Spartan, shown in Fig 3.   (Astronautix, and Nuclear ABMs for the tale.)

The Spartan mission was a GMD for  midcourse interception.  It was to reach the vicinity of the warheads and detonate a 5 MT H-bomb.

No atmosphere, so no shock waves;  the intense x-rays from the explosion would ‘cook’ the electronics and convert the incoming warhead(s) to duds.  Destruction by x-rays – no contact necessary.


Catch the leakers.  Sprint  (Fig 4) was our original solution for the warheads that escape Spartan’s  GMD net  and enter the terminal reentry phase .


Fig 4   Sprint Launch





An H bomb was no solution to an intercept below several km where the interceptor had to operate.  Such an “air burst”  bomb most efficiently converts explosion energy into destructive shock waves.

So they used an enhanced neutron emission bomb, the original neutron bomb that caused such political concern in the 1960s and 1970s –  very small nuclear explosion with ultra high yield of neutrons to destroy the bomb’s electronics.

SecToImpact_txtThe Challenge: Reentry starts at about 100 km up, where dense atmosphere starts, the decoys burn away, and the  real warheads are revealed.  Simplified arguments say that at this point we have less than 15 seconds to launch our interceptor and remove the now-known threats.

These 15 seconds are the challenge to effective TBMD.

The Solution:  Sprint, Fig 5, was designed at the farthest part of the cutting edge engineering, sometimes called “bleeding edge technology.”  It used primary explosive material as its fuel (secondaries like dynamite require an initiator to start)  The advantage of a primary such as nitroglycerin is that it burns with much more rapidly.   The disadvantage is that it occasionally decides for itself when to ignite.


Fig 5    Sprint at Kwajalein


Fig 6    Top: Sprint launch, Bot: designed for HiBEX prototype.

Sprint was pushed from its silo by a piston, shown schematically in this Fig 6. The piston mechanically tilted the rocket toward the target.  It ignited with 100 g acceleration and triggered its N bomb when it came within range of the warhead.  End of incoming threat.

100 g – imagine a 200 lb (98 kg) man becoming 10 tons in an instant. Flesh would turn to paste, most metal objects would be crushed by their own weight

To an observer, Sprint sat quietly in its silo, there was an instant flash and it was as though it had disappeared.

If Sprint missed its target it had to self destruct  a  second or so after expected contact,  or it delivered its neutron bomb into friendly territory.

Sprint was a complex of engineering issues. It moved so fast that its shell became incandescent and the  air around it turned into a glowing plasma.  The body had to be cone shape to survive the acceleration stresses.  The design of  guidance electronics to survive high g stresses and EMP from the plasma environment must have been challenging,

A Sprint  prototype, called HiBEX,  successfully accelerated at 400 g.  Sprint  accelerated at 100 g, its burn lasted longer and it was more agile.  So the HiBEX operation diagram of Fig 5 is not quite right for the Sprint image.

Safeguard – Requiescat In Pace

The Safeguard system was designed, tested and finally proven over the 15 or so years ending in 1971.  Only one ABM base was allowed by the treaty with the Soviet Union, with 30 Spartans and 16 Sprints.  It opened in 1976, near Nekomo, North Dakota.  In time of war, the missiles would have done their job as advertised.  In the absence of an overwhelming saturation attack,  almost certainly no warheads would have detonated on our ICBM missile silos.  However, the base  was closed 4 months later.  There were many bad decisions in those days.  This was not one of them.


Fig 7  Operation Argus. 3 high altitude shots 1958

Closing our ABM base was astonishingly clear minded.   Although no enemy warheads might have gotten through, there would have been plenty of nuclear explosions; almost certainly no one in a 10 mile band about the ICBM field would have survived– it is possible that Safeguard defense might even have disabled ICBM launch, prohibiting revenge retaliation.

The Sprint missile suffered many mishaps.  It had a reasonably good record for a missile but a bad one for a delivery system of neutron bombs. Nuclear weapons ought to be like family cars, with about 1 failure in 100,000 firings  (if fewer, maybe your own side is destroyed).


Fig 8  Op Argus launch 1958 Aug-Sep

Safeguard and Operation Argus    Mishaps during the 0.2 seconds of launch promised disaster, but even with no launch issues, the 20 Sprints would detonate  as low as 5000 ft ( nearly 1 km) above the surface in a last attempt to stop the incoming H-bombs.  But, the Spartan midcourse missiles would have detonated thirty 5 MT bombs between 60 miles  (100 km) and 350 miles (560 km).

Figs 7, 8:  In August and September of 1958, Operation Argus fired three small 1.7 kT plutonium bombs above the South Atlantic at altitudes of 100, 182 and 466 miles (160, 290, and 750 km).

This shot generated electrons moving in magnetic field lines between Earth’s N and S poles.  They disabled radar and radio and caused EMP current surges that burned out circuits in solid state boards.  The man-made radiation belt was an actual dome, not of safety, but of destruction.

Safeguard would release 150 MT of energy and would send EMP shocks everywhere.  Only the very most hardened sites would survive, certainly not civilian power, communication, or any other electronic equipment.

News of the top secret tests leaked out within a few months.  By 1959 everyone understood what exo-atmospheric nuclear explosions could do, even just in testing.  At this time the U.S. was covered in a copper wire and cable web that would have blown completely.

Military shifted to microwave communication but did not focus on the heightened susceptibility of  microchips to the heavy EMP of a nearby nuclear burst.

American leadership ignored the lessons from Argus!   We designed and built Safeguard in the 1960s.  Even in the 21st century, our power grid is still copper webbed across the land.  Our shift to cell phones puts communication into unshielded microcircuits with their extreme EMP sensitivity.  We are actually more susceptible to nuclear strikes than in 1958.

Safeguard did anything but form a wonderful dome of safety.  Its shutdown made us finally safe from our own “friendly” destruction.

Next in the   ABM: Under The Dome   series will be an analysis of modern choices.

Charles J. Armentrout, Ann Arbor
2013 July 22
Listed under   Technology  …   Technology > Aerospace
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About LastTechAge

I am a physicist with years of work in fusion labs, industry labs, and teaching (physics and math). I have watched the tech scene, watched societal trends and am alarmed. My interest is to help us all improve or maintain that which we worked so hard to achieve.
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4 Responses to ABM: Under The Dome – Safeguard

  1. ABE says:

    It will be interesting to read the whole series of articles – you packed a LOT of information into this summary.

    I’m not sure I like where this is headed. They spend all our money – and can’t arrange a competent defense system? “Leave it to the experts” doesn’t seem to be working. I’m hoping to hear your thoughts on improvements.

    The only good part? IF we can only do this, then less technologically oriented countries (ie, North Korea, China, Iran) are having even bigger problems.


    • LastTechAge says:

      Insightful comment, ABE. I don’t like where this is heading,either.

      What I did not include due to information loading was that the Russians installed a number of Safeguard-like nuclear ABM sites. I believe only 4 are left and those around Moscow. The use the Galosh (51T6) midcourse interceptor and the Gazelle (53T66) enothermic interceptor. Gazelle is pretty secret, for example no pictures are available. But it is expected to look like our Sprint.

      Everyone has a big problem with ABM, and maybe that will be the final eulogy.
      Charles Armentrout


  2. Jordan says:

    In Fig. 5, that’s a Sprint at WSMR, not Kwajalein. You can see mountains in the background.


  3. Pingback: Nuke Opera 2020: “World-Wide Delivery in 30 Minutes or Less” — Missile Types and Speeds | Doomsday Writer!

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