It was decided that since the Indian nuclear tests had given an opportunity to Pakistan to conduct nuclear tests after 14 years of conducting only cold tests, the maximum benefit should be derived from this opportunity. It was, therefore, decided, that multiple tests would be carried out of varying yields as well as the live testing of the triggering mechanisms. Since the tunnel at the Ras Koh Hills had the capability to conduct six tests, therefore, six different nuclear devices of varying designs, sizes and yields were selected, all of which had been previously cold tested.
Immediately afterwards, began the process of fitness and quality checks of the various components of the nuclear devices and the testing equipment. A large but smooth logistics operation also got underway with the help of the Pakistan Army and Air Force. This operation involved moving men and equipment as well as the nuclear devices to the Ras Koh test site from various parts of the country.
There are some plausibility problems with this account. The first issue is that successfully collecting data from an actual nuclear test (an area in which Pakistan had no experience despite years of cold tests) is far from straightforward (see [Teller et al 1968; pp. 150, 167]), and increases in difficulty with multiple tests in a single shaft. Unexpected device behavior or problems anywhere along the tunnel could result in the loss of data on any or all shots. If internal telemetry failed, wholly or in part, it would be very difficult to recover useful results from external seismic measurements with so many devices simultaneously exploded so close together. Six devices constituted a large part of the then available highly enriched uranium, perhaps 90 kg consumed out of 210 kg on hand (although once it had spent a couple of years processing its stockpile of low enriched uranium, this would rise to 800 kg or so). A great deal of Pakistan's immediate nuclear resources would be consumed for quite a gamble on useful results.
Other problems include that according to post-test statements, all of these devices were of basically the same type - fusion boosted fission bombs. Furthermore four of the devices were all in the same low yield range (fractional kiloton to a few kilotons), far less than the tens of kilotons claimed for the other two. It is questionable that so many different systems of this type could be usefully tested. Due to the extensive cold testing, the non-nuclear behavior of these systems should have been well understood and thus variations purely in the implosion assembly design would not merit nuclear testing. By exploding them all once (and the last test only a few days later) there would be no opportunity to analyze the test results and conduct retests, or tests of redesigns.
It is also difficult to credit the implication that such an extraordinarily complex test operation was planned and conducted in 10 days. Admittedly, the preparations for tests dated back years (decades!) so that the test equipment would already be on hand, and the basic procedures would have already have been worked out. Nonetheless, there is a big difference in complexity between a one device test, and a five device test, and it is hard to believe that such an operation could be successfully assembled and executed in such a short time without any prior test experience.
Part of the explanation is no doubt that the numerous tunnel fired cold tests were, or at least could be made to be, pretty fair simulations of actual nuclear test exercises. (At least up to the point of data collection - no amount of cold testing can verify the proper behavior of instruments intended to collect data from an energy density and energy output regime a million times higher.) Also the mobilization of test activity immediately after the first Indian tests, detected by U.S. intelligence, indicates that Azam may be wrong - that the planning for the test exercise was conducted much earlier, even before the Indian test, and these previously laid plans were simply being put into operation. Even if not, test preparations clearly began immediately, and thus had an additional week to be successfully concluded. It is significant that the observed preparation activity began a week before Prime Minister Sharif authorized tests, and suggests that the testing activity may not have been entirely under his control.
The tunnel under Koh Kambaran was 1 kilometer long and is described as L-shaped (just as the Indian vertical shafts were L-shaped). The reason for this is that the shaft leading to the entrance is thus shielded from the device detonation, and energy cannot propagate straight up the shaft from the device to the entrance. The description of the tunnel has having separate assembly rooms indicates that in addition to the L-tunnel at the end, the main tunnel had a number of other side tunnels branching off it every couple of hundred meters.
On 19 May 1998, two teams of 140 PAEC scientists, engineers and technicians left for Chagai, Baluchistan on two separate PIA Boeing 737 flights. Also on board were teams from the Wah Group, the Theoretical Group, the Directorate of Technical Development (DTD) and the Diagnostics Group. Some of the men and equipment were transported via road using NLC trucks escorted by the members of the Special Services Group (SSG), the elite commando force of the Pakistan Army.
[Azam 2000]
According to the Azam the nuclear devices - in sub-assembly form - were flown from Rawalpindi to a designated airfield in Baluchistan (Quetta?) on a Pakistan Air Force (PAF) C-130 Hercules transport aircraft (it is curious that so many would all be entrusted to a single aircraft though). Four PAF F-16s armed with air-to-air missiles provided escort, with secret orders to shoot the C-130 down if it tried to fly out of Pakistani airspace. The F-16s were ordered to keep their radio communications equipment turned off so that no orders, in the interim, could be conveyed to them to act otherwise. They were also ordered to ignore any orders to the contrary that got through to them during the duration of the flight even if such orders originated from Air Headquarters.
Dr. Samir Mubarakmand
at a post-test conference.
The nuclear devices were assembled separately at the test site in individual assembly rooms ("zero rooms") located along the one kilometer tunnel under the mountain Koh Kambaran in the Ras Koh range. Azam states that Samar Mubarakmand personally supervised the complete assembly of all five nuclear devices (implying a very lengthy assembly process since it would have to be sequential, probably lasting more than a day). Diagnostic cables were then laid through the tunnel, and out of the tunnel to the telemetry station which communicated with the command/observation post 10 km away. Afterwards, a complete simulated test was carried out by tele-command. This process of preparing the nuclear devices and laying of the cables and the establishment of the fully functional command and observation post took 5 days (i.e. until about 24 May).
On 25 May it was reported by the Associated Press and Reuters that U.S. intelligence officials had said that Pakistani preparations had accelerated in recent days at a site called Raskoh in the Chagai Hills (it later transpired that Ras Koh was indeed the test area, but Ras Koh is a separate mountainous area over 40 km from the Chagai Hills area). Tunneling activities and the setup of explosive monitoring equipment had been observed. "At this point, they could conduct a nuclear test at any time," said one official.
At the same time it had become increasingly likely that any U.S. aid package would fall short of Pakistani expectations. The major inducements suggested at this point - the delivery of 28 F-16s that Pakistan has already paid for and was promised by Pres. Clinton two years ago anyway, and the rescheduling of loans - was not very tempting. Pakistan seemed to be after explicit U.S. security guarantees, something that was unlikely to be offered.
The test tunnel was sealed by the Pakistan Army 5 Corp on 25 May with the assistance and supervision of the Pakistan Army Engineering Corps, the Frontier Works Organisation (FWO) and the Special Development Works (SDW) - a military unit created 20 years earlier specifically to carry out field engineering for nuclear tests. Mubarakmand is said to have walked a total of 5 kilometers along the stuffy tunnels checking and rechecking the devices and the cables before the cables were finally plugged into the nuclear devices. Sealing the tunnel consumed 6,000 bags of cement and was completed by the afternoon of 26 May 1998. 24 hours later the cement had set in the desert heat, and the engineers certified that the site was ready. The fact the tests were ready was relayed to the Prime Minister via General Headquarters.
Late in the day on 27 May the U.S. government reported that Pakistan had been observed pouring cement in a test shaft in the Chagai Hills. This indicated that nuclear test devices were being sealed in, which is the final necessary step before conducting nuclear tests. Officials then predicted that tests could occur within hours.
Pres. Bill Clinton made a last-minute plea to Sharif, Wednesday night. According to presidential spokesman Mike McCurry it was a "very intense" 25-minute call in which the president implored the prime minister not to conduct a test. It was the fourth presidential call to Sharif since India's first explosion on May 11. But the test time had been set - 3:00 p.m. in the afternoon of 28 May 1998.
The Test is Fired
In the pre-dawn hours of 28 May Pakistan cut the communication links for all Pakistani seismic stations to the outside world. All military and strategic installations in Pakistan were put on alert, and the Pakistan Air Force F-16A and F-7MP air defense fighters were placed on strip alert - ready to begin their take-off roll at any moment.
Azam provides a detailed account of the events that day:
At Chagai, it was a clear day. Bright and sunny without a cloud in sight. All personnel, civil and military were evacuated from ‘Ground Zero’ except for members of the Diagnostics Group and the firing team. They had been involved in digging out and removing some equipment lying there since 1978.
Ten members of the team reached the Observation Post (OP) located 10-kilometres away from Ground Zero. The firing equipment was checked at 1:30 p.m. and prayers were offered. An hour later, at 2:30 p.m., a Pakistan Army helicopter carrying the team of observers including PAEC Chairman, Dr. Ishfaq Ahmed, KRL Director, Dr. A.Q. Khan, and four other scientists from KRL including Dr. Fakhr Hashmi, Dr. Javed Ashraf Mirza, Dr. M. Nasim Khan and S. Mansoor Ahmed arrived at the site. Also accompanying them was a Pakistan Army team headed by General Zulfikar Ali, Chief of the Combat Division.
At 3:00 p.m. a truck carrying the last of the personnel and soldiers involved in the site preparations passed by the OP. Soon afterwards, the all-clear was given to conduct the test as the site had been fully evacuated.
Amongst the 20 men present, one young man, Muhammad Arshad, the Chief Scientific Officer, who had designed the triggering mechanism, was selected to push the button. He was asked to recite "All praise be to Allah" and push the button. At exactly 3:16 p.m. the button was pushed and Muhammad Arshad stepped from obscurity into history.
As soon as the button was pushed, the control system was taken over by computer. The signal was passed through the air link initiating six steps in the firing sequence while at the same time bypassing, one after the other, each of the security systems put in place to prevent accidental detonation. Each step was confirmed by the computer, switching on power supplies for each stage. On the last leg of the sequence, the high voltage power supply responsible for detonating the nuclear devices was activated.
As the firing sequence passed through each level and shut down the safety switches and activating the power supply, each and every step was being recorded by the computer via the telemetry which is an apparatus for recording reading of an instrument and transmitting them via radio. A radiation-hardened television camera with special lenses recorded the outer surface of the mountain.
The voltage reached the triggers on all five devices simultaneously in all the explosive lenses with microsecond synchronization.
As the firing sequence continued through its stages, 20 pairs of eyes were glued on the mountain 10 kilometers away. There was deafening silence within and outside of the OP.
A short while after the button was pushed, the earth in and around the Ras Koh Hills trembled. The OP vibrated as smoke and dust burst out through the five points where the nuclear devices were located. The mountain shook and changed colour as the dust of thousands of years was dislodged from its surface. Its black granite rock turning white as de-oxidisation from the radioactive nuclear forces operating from within. A Huge cloud of beige dust then enveloped the mountain.
The time-frame, from the moment when the button was pushed to the moment the detonations inside the mountain took place, was thirty seconds. For those in the OP, watching in pin-drop silence with their eyes focused on the mountain, those thirty seconds were the longest in their lives. It was the culmination of a journey which started over 20 years ago. It was the moment of truth and triumph against heavy odds, trials and tribulations. At the end of those thirty seconds lay Pakistan’s date with destiny.