The Air Force launched an unarmed Minuteman III intercontinental ballistic missile in the early morning hours on Wednesday, testing a new fuse that would set off the nuclear warhead tipping that weapon, as well as its planned successor.

The Air Force development test launch from Vandenberg Air Force Base in California happened one year from the day the U.S.-Russian New START nuclear arms control accord will expire, unless the presidents of those countries agree to an extension.

New START limits the two nations to each deploying no more than 1,550 warheads across 700 intercontinental ballistic missiles, submarine-launched ballistic missiles, and heavy bombers. The U.S. and Russia can extend the treaty for five years past its 2021 expiration, to Feb. 5, 2026.

A development launch uses a spare missile to test new technology. Such launches differ from Air Force operational test launches, in which the service selects a random deployed ICBM from a U.S. silo, disarms it, and launches it from Vandenberg to make sure the missile works as designed.

The missile launched Wednesday flew about 4,200 miles to splash down near the Kwajalein Atoll in the Marshall Islands, some 2,500 miles southwest of Honolulu, according to an Air Force announcement.

This was the second of four launches planned as part of the Air Force’s roughly $2 billion ICBM Fuze Modernization Program, which aims to replace the fuse used to trigger the chemical explosion that sets off the nuclear chain reaction in the W87 warhead. The program’s first test launch was in February 2019, the next is on the slate for March 2022, and the last for November 2022, according to the Air Force’s fiscal 2020 budget request.

The fuse modernization program received about $160 million from Congress for research, development, testing, and evaluation in the 2020 budget year that began on Oct. 1, 2019.

The Air Force conducts fuse modernization design and development at the Department of Energy’s Sandia National Laboratories in Albuquerque, N.M. The service funds the work ― a collaborative effort with the Navy, which is modernizing the fuse on the W88 submarine-launched ballistic-missile warhead through DOE’s Sandia prime contractor, the Honeywell-owned National Technology and Engineering Solutions of Sandia. Northrop Grumman is part of Honeywell’s Sandia team.

The Department of Energy’s Kansas City National Security Campus manufactures the fuses for both the Air Force and Navy programs.

Minuteman III is the silo-based intercontinental ballistic missile that makes up the land-based leg of the U.S. nuclear triad. The missiles would be used to destroy an adversary’s ability to wage nuclear and conventional war on the U.S., and to destroy that adversary’s economy — along with much of its population — to help ensure the foe could not recover from a U.S. nuclear strike.

The Air Force wants to replace its Minuteman III missiles with the Ground-Based Strategic Deterrent (GBSD) beginning in 2030. The GBSD missiles will carry W87-1 warheads provided by the National Nuclear Security Administration, which plans in 2024 to start casting the plutonium cores, or pits, of the warheads at the Los Alamos National Laboratory in New Mexico.

The Air Force projects it will complete the first production unit of the modernized W87 fuse in April 2023. That proof-of-concept unit will be stripped down and examined to prove the design is ready for mass production — something the Air Force expects to start around July 2023, according to the 2020 budget request.

The Air Force plans to make 693 war-reserve fuses, according to the Pentagon’s 2019 Selected Acquisition Report about the modernization program.

There are 400 Minuteman III missiles deployed today. Boeing primed the Minuteman III program. Northrop Grumman looks like the favorite to prime GBSD, after Boeing declined last year to submit a bid for an estimated $25 billion GBSD engineering and manufacturing and development contract.