From: "Adrian Popa" apopa@hrl.com
Date: Wed, 30 Jun 1999 09:18:20 -0700
In the late 1950s while in the antenna lab at Douglas Aircraft Company (DAC), Santa Monica.
I worked with Western Electric (WE) people on the development of the microwave systems for NIKE Zeus. We also worked on the much ballyhood Hecules intercepting Hercules experimental tests.
On the Ajax and Hercules programs DAC was the prime contractor and WE was a subcontractor. On the Zeus (later Spartan and Sprint) programs the roles reversed with WE becomming the prime contractor and DAC the sub. This was the beginning of the electronics costing more than the missiles and aircraft that contained them, something that the airframe manufacturers have had problems with to this day.
DAC fabricated the NIKE missiles and WE supplied the guidance units and microwave assemblies. We lost the command guidance on several of the first Zeus launches and we did all kinds of environmental and vibration testing to try and find the trouble. The Zeus traveled so fast that the antennas burned up in the outter atmosphere.
Special ceramic materials had to be developed to cover the antennas to protect them. We called them eyeballs because they were made of white pyroceramic about the size of baseballs and looked like eyes on the missile. Other misiles such as Thor also were having this loss of telemetry problem and we ended up testing the missile microwave sub systems in a vacuum, something that had not been done before.
What we found was that in the thin atmosphere (about on micrometer mercury pressure) the transmitters in the missiles were forming a plasma glow in the thin air around the antennas cutting off the microwave signals. There is no way to fix the problem except to turn off the transmitters.
Later in the manned space programs this region of the atmosphere became better known as the loss of signal (LOS) region during rentry .
Thanks again for the great web site.
Adrian Popa
Hughes Research Labs
From: "Adrian Popa" apopa@hrl.com
Date: Fri. 1 Jul 1999 4:01 PM
I've been reading more deeply into your NIKE web site and I have more comments.
There is a classic paper "Some Technical Aspects of Microwave Radiation Hazards" by W.W. Mumford in the Feb. 1961 Proceedings of the Institute of Radio Engineers(IRE). Mumford was at Bell Labs at the time and he discusses 45 of the then current high power microwave radar and communications system systems including NIKE. In rank order the worst hazard is the FPS-16 precision track, the HIPAR is 4th on the list , Herc. Imp TTR is 6th, Ajax MTR is 11th and Ajax Acq is 12 th. When I read this article in 1961 it scared the hell out of me for we were expecting our first child and I recalled that we all worked every day with in the hazard zones of the NIKE radars.
The maximum power density in milliwatts per square cm (mw/cm^2) is not at the aperture but at a distance of about 0.1 times the aperture diameter squared divided by the wavelength. At this distance in the antenn near field the power density is or more 5 dB greater than the aperture power density. To reach the arguably safe power density of 10 mw/cm^2 you must keep the following distances away from the aperture when in the center of the beam:
A few of the systems listed include:
| System | Distance in feet for 10mw/cm^2 power density |
| FPS-16 | 1020 |
| FPS-6 | 560 |
| NIKE HIPAR | 550 |
| NIKE Imp. TTR | 400 |
| Ajax MTR | 270 |
| Ajax Acq | 260 |
| TPS-1G | 150 |
| Ajax TTR | 132 |
In those first days of NIKE operation in 1954-55 most of us were not trained in NIKE or radar school, they would come in late 55 & 56. We had some old AAA artillery officers running the battery and a bunch of airplane mechanics learning on the job and from the manuals. I'm still amazed that we got the system to work so well. We often tracked anti-submarine aircraft at negative elevation angles down the Puget Sound and we were often in the beam center less than 100 ft from the apertures! We drew sparks off our tools and some guys could hear the pulse rep rate in there heads. I estimate that we were in fields of about 50mw/cm^2. If you had a wrench (dipole antenna) in your hand or pocket you might get burned from the arcing. Our field telephone lines were draped in the air to the control vans and we would get shocked by the detected microwave energy when using the telephones. Needless to say we stopped using the field telephones when the radars were operating. This problem was also described in the October 1961 Proceedings of the IRE in Oct 1961 by a GE radar engineer.
When I was in engineering school at UCLA in the 1960s they had an air force contract to couple UHF audio modulation into directly (wireless) into the heads of helicopter crewmen for communications purposes . This non thermal phenomenon worked well but they found out that the power density required to have reliable communications was still much greater than 10mw/cm^2 safe limit and the project was stopped before someone's brain was cooked.
The new high power satellite cell phones are opening up this controversy once again.
This weekend I'm going to try to write a note about the great air raid alarm of 1955 when the west coast air defense system all thought WWIII was starting. This has not had much press and I'll have to track down the old newspaper articles on it to refresh the details. Do you recall this day!
Cheers