Improvised UNSC bomb

This Unidentified UNSC bomb was used to destroy the UNSC base known as Crow's Nest during the Battle of Tsavo in November 2552. Little is known about the bomb, other than the fact that it has a large blast radius.

Battle of Crow's Nest
When the Covenant attacked the UNSC Crow's Nest base, Lieutenant Commander Miranda Keyes ordered for a bomb to be set in the operations center of the base. She explained to SPARTAN John-117 that it was a "going away present" for the Covenant, and that it would kill every one of them present in the base. She then ordered Sergeant Major Avery Johnson to start the timer on the bomb's detonator as soon as the wounded Marines were evacuated. Unfortunately, the Jiralhanae were able to kill most of the Marines, disarm the bomb, and take control of the operations center. The Master Chief, however, was able to kill the Brutes and re-arm the bomb. He escaped down an elevator into the motor pool below the hangar, just as the bomb detonated, killing all Covenant forces, and destroying the entire base.

Trivia

 * The large bomb appears to have smaller charges mounted on its main body casing. It is connected to many smaller bombs throughout Crow's Nest, destroying most of Crow's Nest, except the basement and the motor pool.
 * It appears that these bombs can also be found on the level Sierra 117. After the cutscene where Johnson is thrown into the small room, jump down off the cliff and turn behind (once enemies have been eliminated, or in Theater) towards the gate. Stored within the gate are two more bombs, probably duds.
 * The large bomb appears to be non-nuclear. It is likely a thermobaric weapon, which is commonly used to take out enemies in caves or tunnels. Thermobaric bombs generate a lot of air pressure as the result of a fireball effect, which comes from the dispersion of a compound like aluminum oxide or iron oxide. This effect generates a fuel air mixture, and it removes most of the oxygen from the tunnels or caves, causing lungs to collapse.
 * It appears to be the UNSC equivalent of the Anti-Matter Charge that was found on Cairo Station in Halo 2.
 * It has been a joke at Bungie about how Miranda, in the original Halo 2 script, was supposed to "weld a thermobaric bomb to the Master Chief's armor" in a deal with the Prophet of Regret. Jason Jones, on the Halo 3 Legendary Edition commentary, said he wanted to put this in Halo 2, and was going to add this to Halo 3. This bomb may be a reference to it, as Miranda is in charge, and the Master Chief has to arm it.

List of appearances

 * Halo 3
 * Crow's Nest