its goals. The densities reached were thousands of times smaller than predicted. This was traced to issues with the way the laser delivered heat to the target. Most of its energy energized electrons rather than the entire fuel mass. Further experiments and simulations demonstrated that this process could be dramatically improved by using shorter wavelengths. Further upgrades to the simulation programs, accounting for these effects, predicted that a different design would reach ignition. This system took the form of the 20-beam 200 kJ Nova laser. During the construction phase, Nuckolls found an error in his calculations, and an October 1979 review chaired by former LLNL director John S. Foster Jr. confirmed that Nova would not reach ignition. It was modified into a smaller 10-beam design that converted the light to 351 nm and increase coupling efficiency. Nova was able to deliver about 30 kJ of UV laser energy, about half of what was expected, primarily due to optical damage to the final focusing optics. Even at those levels, it was clear that the predictions for fusion production were wrong; even at the limited powers available, fusion yields were far below predictions. Halite and Centurion, 1978 Each experiment showed that the energy needed to reach ignition continued to be underestimated. The Department of Energy (DOE) decided that direct experimentation was the best way to settle the issue, and in 1978 they started a series of underground experiments at the Nevada Test Site that used small nuclear bombs to illuminate ICF targets. The tests were known as Halite (LLNL) and Centurion (LANL). The basic concept behind the tests had been developed in the 1960s as a way to develop anti-ballistic missile warheads. It was found that bombs that exploded outside the atmosphere gave off bursts of X-rays that could damage an enemy warhead at long range. To test the effectiveness of this system, and to develop countermeasures to protect US warheads, the Defense Atomic Support Agency developed a system using fast-shutting doors that allowed the X-ray burst from a bomb to travel down long tunnels and then close the doors before the nuclear blast arrived. This saved the reentry vehicle (RV) from damage and allowed them to be inspected. ICF tests used the same system, replacing the RVs by hohlraums. Each test simultaneously illuminated many targets, each at a different distance from the bomb. Another question was how large the fuel assembly