
In the hot afternoon of 28 May 1998, an Mi-17 transport helicopter laboured its way towards the towering Chagai Mountain range in Western Pakistan.
It's passengers were about to witness the pinnacle of more than thirty years of hard work, and an investment of several hundreds of millions of US dollars. Five nuclear devices had been placed into a double s-shaped tunnel drilled into the tall mountain looming ahead of them.
Traveling inside the helicopter's passenger compartment was the heads of Pakistan's two rival nuclear organizations:
PAEC Chairman
Isfaq Ahmed and
KRL Director
Abdul Qadeer Khan.
It was the Pakistani Atomic Energy Commission, under the leadership of Munir Ahmad Khan, that had established much of Pakistan's nuclear infrastructure by the time A.Q. Kahn returned to the homeland. In 1976, Munir Kahn celebrated his 50th birthday looking back at a long international career within the International Atomic Energy Agency. His organization was firmly in control of the country's embryonic bomb programme.
Munir Kahn liked to operate silent and deep. To him, the 10 year younger A.Q. Kahn must have been an annoying up-start: brash, careless and ruthless.
The younger Khan had ambition, plans and stamina. He assumed control over his laboratory after a vicious power struggle with the older Khan and the much larger PAEC. He did so with relative ease, indicating that he had plenty of political cover from Pakistan's highest political strata.
Twenty years later, there was in effect two bomb programmes in existence in Pakistan. KRL had exclusive control over uranium enrichment. It had also branched into the shaping of uranium metal into cores, weapon design, and delivery vehicle research, development and testing. PAEC was doing parallel work in all these areas. It also controlled the nuclear power plants (and access to the plutonium route to the bomb).
What happened within this two organizations during the 1980s and 1990s is largely uncharted. It is likely that they started work on several designs: both domestic and imported. The KRL design was clearly acquired from China. The origins of PAEC designs are mostly unknown.
It is quite likely that the organizations proceeded on several tracks at once, much like the Soviet Union did 40 years earlier. The first Soviet design was much more powerful and efficient than the US Manhattan Project design. But since Fuch had leaked detailed specifications to the Soviets, Stalin and Beria thought it was prudent to proceed with constructing proven designs first. Something similar could have happened in Pakistan.
Irrespective of which bomb design was tested in 1998, however, PAEC held one trump-card; it owned and controlled the test site. KRL had no suitable sites of their own, and had seemingly been relegated to the back seat.
It is possible that the heads of PAEC and KRL had laid their rivalries aside during this day. In less than an hour, Pakistan, a developing nation in which only about half the population knew how to read and write properly, was about to take an overt step into an exclusive but dangerous club. Pakistan was about to test their first series of nuclear weapons.
Anatomy of a test site
The
Chagai test site is located about 935 kilometers southwest of Islamabad. It is a harsh area of our planet, with very little rainfall. Its rock is very dry, which minimizes the risk of venting and contamination of the local water table. It does ensure that the detonation is firmly coupled to the rock, however, making it easier for others to estimate the yield of the detonations.
The site itself is unassuming from the air (see my
placemark). A dirt road leads up to the site from a dried up river bed. A support camp is located about a kilometer south of the presumed tunnel entrance, which is served by a number of small shacks and a small unpaved road.
The site was known to US intelligence, however. They had been monitoring the test range ever since India's test a couple of weeks earlier. According to a 26 May 1998
CNN report:
"They continue to make preparations and appear to be very close to being in a position to conduct a test should they decide to do so," said a U.S. intelligence official who spoke on condition of anonymity. "The level of preparation should suggest that they do indeed plan to conduct a test."
U.S. spy satellites have been monitoring activity at the Chagai Hills test site in western Pakistan. In particular, they have noted tunneling activity that typically precedes an underground test. The satellites also have observed the laying of explosive monitoring equipment and the setting up of observation and measuring posts.
The double s-shape and Khan's arrival
According to Dr. Samar Mubarakmand, the current PAEC chair, the site was surveyed and prepared between 1977 and 1982. He claims that PAEC personell arrived to the complex on 20 May and that they prepared for the test for a week. On the morning of 28 May 1998, the Pakistani Army moved in to seal the tunnel and clear the range for the pending shot.
A.Q. Khan is reportedly posing in the tunnel in the picture above. Supporters of PAEC often claim that Khan arrived to the site only 30 minutes before the test. This view is difficult to reconcile with the photograph. The photo must have been taken some time before the test - and definitively before the tunnels were sealed. Of course, Kahn could also have been snapped in some other tunnel, somewhere else.
The tunnel had a double s-shape configuration. According to a
speech by Mubarakmand:
The designing of the tunnels is also a very intricate thing. It is not just blasting a hole into a mountain. Again there is a lot of science. I shall tell you why. If you have a straight tunnel and you put the bomb at the end of the tunnel, you plug the tunnel with concrete and explode the bomb, the concrete is really going to blow out and so all the radioactivity is going to leak out through the mouth of the tunnel. We did not want this to happen. The tunnel is not designed safe but is designed in the form a double-S shape and when we detonate the bomb, the pressures are very great. They move the mountain outward and you use the force of the bomb to seal the tunnel. When the rock expands under the explosion, the rock moves in the direction so that it seals the tunnel. So the tunnel collapses inward by the force of the tunnel. This is how you seal the tunnel through the force of the bomb.
The tests
Unsurprisingly, underground nuclear tests are as violent as their above-ground cousins. The Pakistanis would have needed to ensure that their tests were appropriately separated from each other. According to the now-defunct PIADS, the yield of two devices was 25 kilotons and 12 kilotons respectively. The remaining three devices were in the sub-kiloton range.
Since the tunnel was s-shaped, this would have left some room to deploy the devices at a safe distance from each other. The cavity from the largest test would have had a 50 meter radius. To use a tired analogy, the Statue of Liberty would have just fitted inside the newly formed space.
As a rule of thumb, horizontal tunnel tests are generally spaced with a minimum shot separation distance of twice the combined cavity radius plus 30 meters. Chagai-1 would have been placed at some 205 meters from Chagai-2. Chagai-2, in turn, would have been placed some 130 meters from the sub-kiloton devices, which would need to have been spaced at approximately 83 meter intervals. In other words, all five tests would have fitted comfortably within the tunnel.
It is not clear how successful the test was. The yield estimates are consistently lower than Pakistani declarations. This indicates that one or several devices did not perform as planned. It remains unknown to this day which device failed and which device worked as planned. It doesn't matter that much, however, since Pakistan demonstrated its ability to detonate a nuclear weapon.
Over the next ten years, Pakistan and India would work towards perfecting their arsenals, and develop suitable delivery systems. This silent arms race is still surging ahead.