1. In a method of assisting production of oil from a tar sand wherein first and second nuclear explosives are placed below said tar sand, said first and second nuclear explosives being spaced laterally from each other by a distance such that when said first nuclear explosive is detonated and said second nuclear explosive is thereafter detonated, some of the earth between said second nuclear explosive and said first nuclear explosive will crater into the cavity formed by said first nuclear explosive, and said second nuclear explosive is detonated after said first nuclear explosive and before the cavity formed by said first nuclear explosive collapses, the improvement comprising placing said first and second nuclear explosives below said tar sand in a rock different from said tar sand by a distance of less than 250 feet and less than 3R feet where R is the cavity radius in feet and is determined in accordance with the following equation: where C is a constant ranging between 225 and 345, W is the expected yield of said second nuclear explosion in equivalent kilotons of TNT, d is the average overburden density in grams per cubic centimeter ranging from about 1.6 to 2.7, and h is the depth of burial in feet.

2. An improved method of producing oil from a tar sand wherein a horizontally extended volume of rock different from a tar sand is formed below said tar sand, which method comprises: a. placing first and second nuclear explosives below said tar sand in said rock by a distance of leSs than 250 feet and less than 3R feet where R is the cavity radius in feet and is determined in accordance with the following equation: where C is a constant ranging between 225 and 345, W is the expected yield of said second nuclear explosion in equivalent kilotons of TNT, d is the average overburden density in grams per cubic centimeter ranging from about 1.6 to 2.7, and h is the depth of burial in feet, said nuclear explosives having a yield such that upon detonation the explosions of said nuclear explosives will be contained, said second nuclear explosive being spaced laterally from said first nuclear explosive by a predetermined distance, said predetermined distance being such that when said first nuclear explosive is detonated and said second nuclear explosive is thereafter detonated, some of said rock between said second nuclear explosive and said first nuclear explosive will crater into the cavity formed by said first nuclear explosive, b. detonating said first nuclear explosive to create a first nuclear explosion and a first cavity, c. detonating said second nuclear explosive to create a second nuclear explosion a predetermined time after said first nuclear explosion, said predetermined time being such that said second nuclear explosion occurs after said first cavity is formed by said first nuclear explosion and before said first cavity collapses, thereby causing some of said rock below said tar sand and between said second nuclear explosive and said first cavity to be broken and some of said rock to crater into said first cavity and thereby creating a horizontally extended broken volume of said rock below said tar sand, and d. injecting fluid into said broken volume of said rock to produce oil from said tar sand.

9. An improved method of producing oil from a tar sand wherein a horizontally extended broken volume of rock different from a tar sand is formed below said tar sand, which method comprises: a. placing two or more first nuclear explosives below said tar sand in said rock by a distance of less than 250 feet and less than 3R feet where R is the cavity radius in feet for each nuclear explosive of said first nuclear explosives and is determined in accordance with the following equation: where C is a constant ranging between 225 and 345, W is the expected yield of second nuclear explosion in equivalent kilotons of TNT, d is the average overburden density in grams per cubic centimeter ranging from about 1.6 to 2.7, and h is the depth of burial in feet, b. placing at least one second nuclear explosive below said tar sand in said rock by a distance of less than 250 feet and less than 3R feet where R is the cavity radius in feet and is determined in accoRdance with said equation, said first and said second nuclear explosives having a yield such that upon detonation the explosions of said nuclear explosives will be contained, said second nuclear explosive being spaced laterally from each of said first nuclear explosives and being spaced from at least two of said first nuclear explosives by a distance such that when said first nuclear explosives are detonated and said second nuclear explosive is thereafter detonated, some of said rock between said second nuclear explosive and said at least two first nuclear explosives will crater into the cavities formed by said at least two first nuclear explosives, c. detonating said at least two first nuclear explosives to create first nuclear explosions and first cavities, d. detonating said second nuclear explosive to create a second nuclear explosion a predetermined time after said at least two first nuclear explosions, said predetermined time being such that said second nuclear explosion occurs after said first cavities are formed by said at least two first nuclear explosions and before said first cavities collapse, thereby causing some of said rock below said tar sand and between said second nuclear explosive and said first cavities to be broken and some of said rock to crater into said first cavities and thereby creating a horizontally extended broken volume of said rock below said tar sand, and e. injecting fluid into said broken volume of said rock to produce oil from said tar sand.

16. An improved method of producing oil from a tar sand wherein a horizontally extended broken volume of rock different from a tar sand is formed below said tar sand, which method comprises: a. placing at least one first nuclear explosive below said tar sand in said rock by a distance of less than 250 feet and less than 3R feet where R is the cavity radius in feet and is determined in accordance with the following equation: where C is a constant ranging between 225 and 345, W is the expected yield of said second nuclear explosion in equivalent kilotons of TNT, d is the average overburden density in grams per cubic centimeter ranging from about 1.6 to 2.7, and h is the depth of burial in feet, b. placing at least two second nuclear explosives below said tar sand in said rock by a distance of less than 250 feet and less than 3R feet where R is the cavity radius for each of said at least two second nuclear explosives and is determined in accordance with said equation, said first and said second nuclear explosives having a yield such that upon detonation the explosions of said nuclear explosives will be contained, said at least two second nuclear explosives being spaced laterally from said first nuclear explosive by a distance such that when said first nuclear explosive is Detonated and said at least two second nuclear explosives are thereafter detonated, some of said rock between said at least two second nuclear explosives and said first nuclear explosive will crater into the cavity formed by said first nuclear explosive, c. detonating said first nuclear explosive to create a first nuclear explosion and a first cavity, d. detonating said at least two second nuclear explosives to create second nuclear explosions a predetermined time after said first nuclear explosion, said predetermined time being such that said at least two second nuclear explosions occur after said first cavity is formed by said first nuclear explosion and before said first cavity collapses, thereby causing some of said rock below said tar sand and between said at least two second nuclear explosives and said first cavity to be broken and some of said rock to crater into said first cavity and thereby creating a horizontally extended broken volume of said rock below said tar sand, and d. injecting fluid into said broken volume of said rock to produce oil from said tar sand.