HARM AGM-88A Missile

Although I don’t usually commemorate the date, on this day in 1977 I started my first job as an engineer for Texas Instruments in Dallas.

My first (and only) work there: design of the HARM AGM-88A missile for the U.S. Navy (actually, a joint development of both the Navy and the Air Force, but we interfaced mostly with the Navy.)

Overview of the Missile

There’s a lot out there for the very technically minded on this weapon (such as the Australian and Dutch sites here) but I’ll try to present the simple view.

HARM stands for High-speed Anti-Radiation Missile.  “Radiation” in this case isn’t a nuclear facility but a radar installation.  The missile’s purpose is to take out radar installations and thus blind the enemy combatant to incoming planes or whatever other airbore weaponry that the U.S. military decided to delopy against an enemy.

The missile is the direct descendant of the Shrike and Standard ARM missiles used in Vietnam.  The Shrike was produced by Texas Instruments and that is what put TI in the missile business.   The Missile and Ordinance Division (which was contracted to develop the HARM) was at the company’s central facility in Dallas at the time, although it was later moved to Lewisville, TX.

The primary Navy point of contact for us was the Naval Weapons Centre in China Lake, CA.  Tests on the prototypes were conducted there and they were excellent people to deal with, although Navy projects in particular suffer from excessive mission expansion.

The missile (as shown in the photo above, with two of its wings removed to fit in the rack) is divided into four parts:

  1. The Seeker, at the very front of the missile.  A plastic nose cone (radome) covers the antenna, which seeks out and locates the radar installations.  The electronics to process this information are also there.
  2. The Warhead, where the explosive charge to destroy the target is contained.  During the test program, this was the Test Section, which contained telemetry (as was the case with the space program) to monitor the missile’s flight status and enable us to evaluate both its performance and our modelling of same.
  3. The Control Section, where the wings were rotated to alter the course of the missile during flight.
  4. The Rocket Motor, which propelled the missile away from the aircraft from which it was launched (it’s an air-to-surface missile) and bring it up to the velocity necessary to reach its target.  The HARM is ballistic in the sense that the rocket motor only operates during the first few seconds of flight.

The video below is a good overview of the mission of the missile, from an early (around 1980?) video.

At the time the missile was developed, the main enemy was Soviet.  However, most of the action it has seen has been, unsurpisingly, in the Middle East.  Its first use came in 1986 in Libya; it was also used in the 1991 Gulf War and 2003 Iraq invasion.

Development

If you read the development history of this missile, one thing that strikes you is the length of time it took from start to finish.  Developing HARM took most of the 1970’s and early 1980’s, and this is a fairly simple weapon compared to, say, a fighter or a large warship.  There are two main reasons for this.

The first is, of course, the bureaucratic nature of government.  It’s tempting to say this is the only reason but it isn’t.  Much of that is due to getting funding through Congress, which can be an ordeal for all kinds of projects.  And, of course, changes in administration don’t always help either.  Right after I came to work at TI Jimmy Carter was inaugurated, and funding for the project was put on some kind of “hold.”  My job wasn’t affected but some people’s was.

The second is that our military doesn’t like to leave anything to the imagination or chance if it can help it.  It wants to cover all of its bases and make sure whatever is buys is operational in all environments and meets all of the threats it’s intended to meet.  With radar installations, this leads to the complicated sets of modes that you see described both in the linked articles and in the videos, including the obvious one: shutting off the radar to try to throw the missile off course.   Given that the electronic counter-measures (ECM) environment is very fluid, this leads to a constant cycle of revision during development to meet changes in the field.  In an era when such changes had to be hard-coded into the electronics, meeting this took time.  (Later versions of the missile went to the “soft” coding that is routine today with virtually every electronic device.)

My Work

But another challenge–and one I was involved in–concerned the missile’s electronics and controlling the temperature they operate at, from the time the plane is launched until the missile hits its target.  This is an easier problem to explain now that it was thirty years ago.

In order to function properly, electronic devices have to be kept below certain temperatures.  There are two basic sources of heat.  The first is the electronics themselves, as anyone who has tried to operate an aluminium MacBook or MacBookPro wearing shorts will attest.  To get rid of that heat usually requires a fan of some kind, which isn’t an option on the missile.  (The avionics for it, stored on the aircraft, is another story altogether; it’s similar to the box for a desktop computer, although it has to operate in the thin air of elevated altitudes.)

The second source is external.  For most electronic devices on the earth, that means when the room temperature is too high, or the ventilation is inadequate, either heat is introduced to the unit or not allowed to escape.  That’s why it’s important for your computer or any other heat-generating electronic device to be properly ventilated.  With any kind of air or space craft, at elevated speeds heat is generated by friction with the air.  The most spectacular (and tragic) demonstration of this took place in the 2003 disintegration of the space shuttle Columbia.  Since the HARM’s most sensitive components are located at the front of the missile, that only added to the challenge.

To meet that challenge was, from the standpoint of most engineering in the 1970’s, “the shape of things to come.”  We used simulation software for everything: flight, component stress, heat, you name it.  The aerospace industry was the leader in the development and implementation of computer simulation techniques such as finite element and difference analysis, things that are routine in most design work today.  Most of the work we did was in “batch” mode, and that meant punching a batch of Hollerith cards and taking them down to the computer centre for processing.  Interactive modes via a terminal were just starting when I left, as were plotting graphics.  Today most any flight and flight related wargame posesses the same kinds of simulation we did then, only more, and the graphics to watch what’s going on.  That last was, in my view, the biggest lacuna of our simulation; we only saw and interpreted numbers.

The Company

Texas Instruments was one of the early “high tech” (“semiconductor” was the more common term at the time) companies like Fairchild and later Intel.  It had a breezy, informal (if somewhat spartan) work environment, complete with an automated mail cart which followed a (nearly) invisible stripe in the hallway to guide it to its stops.   It encouraged innovation and creativity in its workforce through both its work environment and its compensation system.  The only time coats and ties came out is when the “brass” (in this case military) came.  That was, from a corporate standpoint, the biggest challenge: keeping the Missile and Ordinance Division, an extension of the government (as is the case with just about any defence contractor,) creative, while at the same time trying to keep the bureaucratic mindset and procedures from oozing into the rest of the company.  Our Division was, to some extent, “quarantined” from the rest of TI to prevent the latter from taking place.

For me, it was a great place to start a career, and I got a chance to work with great people on an interesting project.

My thanks to Jerry McNabb of the Church of God Chaplains Commission (and a former Navy chaplain) for the photos.