In October 0081, after the end of the One Year War, a top-secret plan code-named GUNDAM DEVELOPMENT PROJECT was drawn up along with the reorganization of the Earth Federation Forces. It is the most powerful tactical weapon development plan that is suitable for operational situations such as conflict control that are expected to occur in the postwar world situation. The Federation Forces avoided the option of dealing with this plan only within the military, and signed a secret agreement with Anaheim Electronics, which plans to expand the business scale in the city of Von Braun on the moon, and instructed them to submit various design proposals. Anaheim Corp. acquired small and medium-sized munitions industries scattered throughout the Earth Federation under its umbrella and expanded its business. By doing so, he planned to further develop military development technology. It is one of the most profitable corporate entities associated with the One Year War. In the Gundam development plan, as the second draft of the assault-type heavy attack aircraft, the development name RX-78GP02 = Commonly known as Gundam prototype No. 2 Physalis design prototype. . They arranged the personnel most suitable for the development of the so-called heavy armored mobile suit. As an assault type that takes advantage of its heavy armor, this aircraft was designed with a focus on single-machine attack capabilities, and was also designed to be used in conjunction with the GP01 type, which is dedicated to melee combat. It was a necessary condition for the aircraft to have mobility while satisfying the required payload in ground battles. Therefore, the thermonuclear jet engine, which is the key to mobility, is based on the know-how and actual combat data of Tsimud's masterpiece MS-09, and the armor balance of the aircraft and the layout of the propulsion engine are fully based on such precedents. It was designed to make the most of it. The prototype was completed in UC0083, two years after the start of the project. It is also said that part of the design data of this aircraft influenced the later Gamma Gundam RMS-099 Rick Diaz. However, during the early stages of development, the aircraft was given a different purpose. It is operated as a strategic nuclear attack aircraft. Due to the unavailability of old-fashioned electronically guided weapons and the short effective range of the planned Mk82 nuclear warhead in an operational area under Minovsky particle spraying, it is difficult to get extremely close to the target of attack. There was no choice but to use a mobile suit as a weapon that could be used. Of course, the Antarctic Treaty prohibited the use of nuclear weapons during the war, but some high-ranking officials of the Earth Federation government, which was aiming for new world domination, approved the development of nuclear attack aircraft under the pretext of mopping up the remnants of the Zeon forces. It was decided to Because of this option, the plan is said to have been treated as top secret from the beginning. As a result, in order to quickly withdraw the aircraft from the operational area after a nuclear attack, it is necessary to ensure the protection of the aircraft from radioactivity, countermeasures against the strong electromagnetic pulse, and heat resistance and impact resistance. We are changing the design of each part of the aircraft. In particular, sufficient measures were taken for the enemy search camera and visual field formation control equipment concentrated on the head. In addition, the 60mm Vulcan cannon for close combat is left as it is in the layout as the basic equipment of the Gundam development plan. The completed prototype was given the model name RX-78GP02A. Subtype A is said to be an abbreviation for ATOMIC GUNDAM. The armor material of the aircraft was made into a three-layered composite structure centered on Luna Titanium, and the nuclear warhead launcher was manufactured in a separate assembly type bazooka type exclusively for this aircraft. In order to maintain the impact resistance strength at the time of launch, the base of the launcher Atomic Bazooka, which was specially designed for this machine, is connected to the rear mounted unit, and the separated barrel part is designed to be suspended inside the special shield described later. became. As part of the defense system, the separate protective shield common to the Gundam type was specially designed to cover the aircraft, and a forced cooling device was built in to protect the aircraft during nuclear use. Unlike the standard Gundam design, the large leg armor cannot be covered with a shield, so a cooling device is built in beforehand. The reason why the flexible thruster binder, which integrates the leg propulsion device, the armor layout, and the large rocket engine, which is the key to the movement device, is excessively heavily armored is due to various countermeasures when using this strategic nuclear weapon. In particular, the binders on both shoulders also serve as escape boosters to ensure the mobility of the heavy mobile suit itself, in order to quickly escape from the operational area. Also, assuming that some kind of close combat (MS battle) occurred during the operation, a beam saber was added to the basic equipment like a normal mobile suit. The aircraft weight balance in this design could not have been achieved without the strength design using Luna Titanium, and it can be said that Anaheim was the only company that could achieve it at this point after the war. From the development stage, the GP02A's main purpose was to carry out operations near the hypocenter, so special emphasis was placed on pilot protection by installing a spherical outer shell-type armored bulkhead that is far stronger than a normal MS. . For this reason, the concept of reviewing the core fighter = core block was out of scope for this unit from the beginning, and the spherical vision type cockpit partition wall that was tested in the RX-78NT-1 Gundam Alex developed at the ORGUSS base in North America at the end of the war. introduced together. As a result of emphasizing the character of a nuclear attack aircraft, it was difficult for the Core Fighter II, which was being developed in parallel, to fulfill the purpose of protecting and recovering pilots during operations. It can be said that complication of the design was avoided from the beginning. GP01 and this GP02A, which were rolled out at the Livermore factory of Anaheim Electronics in Von Braun, were mounted on the amphibious assault ship Albion for evaluation tests and transported to the Torrington base in Australia. Major Annabelle Gato, former commander of the Principality of Zeon Space Attack Force 302nd Patrol Squadron belonging to the Delaz Fleet, is aiming for the date and time of the tactical nuclear launch test at the ground base. was able to seize this aircraft, confirming that the old Zeon-affiliated information network was still functioning. Aiguille, who claimed to violate the Antarctic Treaty and oppress space immigrants by announcing the existence of this machine as a nuclear attack aircraft to the Earth Federation government (the Earth Federation government completely denied this statement as Delaz Fleet propaganda). The former Zeon forces remnant Delaz Fleet, led by Vice Admiral Delaz, succeeded in destroying 65% of the participating ships with a nuclear attack at the Federation Forces Fleet Review held in November of the same year. However, due to the pursuit of RX-78GP01Fb, which has been modified for space battle specifications, it was completely destroyed along with the aircraft after the engagement. After that, its existence was completely erased from the records of the Federation Forces. Since then, no information has been confirmed regarding the development of a nuclear attack aircraft.