Lockheed E-XX
The Lockheed E-XX is a planned United States Navy aircraft based on the EC-130J and intended to replaced the Boeing E-6 Mercury in the TACAMO role, communicating with US nuclear ballistic missile submarines. The current E-6 aircraft were built in the late 1980s, and while they are expected to fly into the 2030s, the underlying platform is aging and support costs are increasing. Because of this, in 2020, the Navy began a program to develop a new platform. This program will take several years to complete, and the E-6 will continue to fulfill the role in the meantime.

Development 
The US Department of Defense has relied on the Boeing 707 platform for decades, going back to the KC-135 in 1956 that technically predates the 707 itself, which did not fly until 1957. Boeing continued production of various military aircraft using the basic platform until the last E-6 Mercury aircraft were delivered in 1991. Since then, spare parts for the platform have gotten harder to find and operations have become more expensive.

By 2015, both the Air Force and Navy realized that they had to look ahead to new platforms to manage their nuclear arsenals in combat. The Air Force had already retired its KC-135-based EC-135C aircraft in 1998, turning over its Looking Glass mission to the Navy's E-6 fleet while continuing to fly the Boeing E-4 as the National Emergency Airborne Command Post. But the E-4, built in the 1970s and based on the Boeing 747-200, was also aging and in need of replacement.

For a few years, the Air Force and Navy considered a unified replacement that would move the E-6's combined TACAMO and Looking Glass mission to a single new aircraft run by both branches. In 2018, this program was envisioned to replace the E-4, E-6, and the C-32A (based on the Boeing 757 and often used as Air Force Two) with a single aircraft under the moniker NEAT (combining National Airborne Operations Center (NAOC), Executive Airlift, Airborne Command Post (ABNCP), Take Charge and Move Out (TACAMO)).

However, in December 2020 (Fiscal Year 2021), the US Navy announced that it awarded a contract to Lockheed Martin for the purchase of three EC-130J-30 Hercules aircraft to be used as testbeds for the TACAMO mission, signaling that the two branches would go in different directions. The aircraft were fully funded in FY2023. One aircraft is to be used for air vehicle testing while the other two are planned for mission systems testing, "allowing simultaneous mission system, flight and ground test, and correction of deficiencies." The aircraft selection represents a return to the C-130 platform by the Navy, which for years used the EC-130Q (an older variant despite the higher letter) for the TACAMO mission prior to adoption of the E-6 Mercury.

The selection of the C-130 platform, which is much smaller than the E-6, was surprising to some who expected something based on the larger P-8 Poseidon (based on the Boeing 737) or the much larger KC-46 Pegasus (based on the Boeing 767). The Navy has justified its decision based on the reduced mission, cost savings that come from commonality with other US military C-130 uses, and the ability to deploy to a much wider range of bases around the world. With the C-130's reduced runway requirements compared to any of the above jets and design features that emphasize austere and even rough-field capabilities, the E-XX's operations would become less predictable to adversaries.

The Navy envisions purchases of three production aircraft in FY2027 and another six in FY2028.

Funding 
Since the FY2022 NDAA, Congress has appropriated over $400 million in development funds, including $48.6 million for the first contracts in 2022 and $502 million in 2023. The Navy requested substantially less funding in FY2024, asking for $213.7 million. As of the FY2024 funding request, the program is expected to cost $3.125 billion over the period from FY2022 through FY2028.

Design 
Many details about the design have not been publicly released partially due to the classified nature of its mission but also because the project is still in development. The Navy described its mission in the FY2024 budget request:The TACAMO mission provides an airborne capability for survivable, endurable and reliable airborne command, control and communications between the United States (U.S.) National Command Authority (NCA) and the U.S. strategic forces. This mission is critical in the deterrence and management of a nuclear conflict. A dedicated communications platform, TACAMO aircraft feature the ability to communicate on virtually every radio frequency band from very low frequency (VLF) up through advanced extremely high frequency (AEHF) using a variety of modulations, encryptions and networks, minimizing the likelihood an emergency message being jammed by an enemy.

The specific model selected, the EC-130J-30, is  longer than the base model, providing more space for crew and equipment. Lockheed has presented an artist's conception of the aircraft that shows enlarged and extended landing gear fairings, multiple domes extending from the fuselage, and two wire antennas capable of extending from the rear of the aircraft.

Known planned capabilities include electromagnetic pulse (EMP) hardening and cybersecurity hardening, as well as an upgrade of the trailing wire communications system currently fielded on the E-6. This system extends a  long wire from the tail of the aircraft to enable VLF communications with submerged submarines.

One notable mission change in the transition from the E-6 Mercury to the E-XX is the deletion of the capability to act as the Air Force Airborne Command Post (ABNCP) with the capability to communicate with nuclear bomber fleets and ICBM silos. At one time, the Boeing EC-135C Looking Glass fulfilled the ABNCP mission, but when it was retired by the Air Force in 1998, the E-6 took over. With the Air Force expecting to handle those duties using the planned Survivable Airborne Operations Center aircraft, that capability will no longer be needed aboard the Navy's TACAMO platform.

See Also

References 

United States Navy
Aviation
Aircraft