Dark star aircraft set to be deployed.

Key Points: Speculation continues regarding a hypersonic successor to the SR-71 Blackbird, often called SR-72 “Son of Blackbird,” potentially capable of Mach 6+ speeds for ISR and strike missions.

-Hints from developer Lockheed Martin, including cryptic social media posts and collaboration on the similar “Darkstar” aircraft in Top Gun: Maverick, fuel beliefs such a program exists.

However, despite these intriguing clues suggesting development is underway, concrete details about the aircraft’s capabilities, status, and even confirmed existence remain highly classified and speculative.

For many decades, Lockheed’s SR-71 Blackbird held the lofty title of the fastest air-breathing crewed aircraft ever built.

Developed during the Cold War, the SR-71 was designed to conduct high-speed reconnaissance missions at altitudes in excess of 80,000 feet. It relied on sheer speed — over Mach 3, or three times the speed of sound — to simply outrun enemy air defenses.

Since its retirement in the late 1990s, speculation has persisted about a hypothetical successor.

Boeing X-37 spaceplane has a top speed of Mach 14.1, which is an incredible 10,827 mph; but even though it's operated by the U.S. Space Force, it's not really a military plane. Any aviation buff knows the fastest plane ever was the SR-71 Blackbird, but it was retired back in the 1990s.

Mar 24, 2025.

Space force briefing.

AFNS) -- The X-37B Orbital Test Vehicle-7 (OTV-7), the U.S. Space Force's dynamic unmanned spaceplane, successfully deorbited and landed at Vandenberg Space Force Base, California, March 7, 2025 at 02:22 a.m. EST.Mar 13, 2025

The U.S. Space Force landed the X-37B at Vandenberg SFB, California, to exercise its rapid ability to launch and recover its systems across multiple sites. X-37B’s Mission 7 was the first launch on a SpaceX Falcon Heavy Rocket to a Highly Elliptical Orbit. While on orbit, Mission 7 accomplished a range of test and experimentation objectives intended to demonstrate the X-37B’s robust maneuver capability while helping characterize the space domain through the testing of space domain awareness technology experiments.

The successful completion of the novel aerobraking maneuver demonstrated the agile and flexible capabilities the X-37B provides the United States Space Force. Drawing on decades of lessons learned from previous space missions, this technique involves the use of atmospheric drag over the course of multiple passes to change orbits while expending minimal fuel.

“Mission 7 broke new ground by showcasing the X-37B’s ability to flexibly accomplish its test and experimentation objectives across orbital regimes. The successful execution of the aerobraking maneuver underscores the U.S. Space Force’s commitment to pushing the bounds of novel space operations in a safe and responsible manner,” said Chief of Space Operations Gen. Chance Saltzman.

Next engines in development.

Pulsar quantum fusion engine.

Image: Pulsar)

The company says its in-house team has been working on the project for a decade and it is "rapidly advancing toward in-orbit testing, with components of the system’s power supply set for demonstration later this year" and then demonstrated in orbit in 2027. They hope for a production-ready Sunbird in the early 2030s.

The Sunbird concept is for the fusion-powered 'tugs' to be permanently based in space, able to dock on to spacecraft and propel them at high speed over vast distances. Pulsar Fusion says it foresees a compact nuclear fusion engine providing both thrust and electrical power for spacecraft, including as much as 2 MW of power on arrival at a destination.

The company says that unlike the large amounts of fuel required for a chemical rocket, the relative tiny amounts of the deuterium and helium-3 fuel mix required means "a spacecraft would launch with a fixed supply, sufficient for missions like Pluto in four years, with no mid-flight refuelling needed".

Pulsar describes itself as a "space propulsion systems and services company delivering intelligent propulsion now and delivering the future through fusion propulsion". It uses Hall Effect Thrusters, which generate thrust by ejecting neutral plasma. In 2023 Pulsar Fusion formed a partnership with US-based Princeton Satellite Systems to use artificial intelligence to design a hyper-fast space rocket, with the aim being to create a deep space rocket engine with a 500,000 mph (800,000 km/h) potential.

CEO Richard Dinan said: "Pulsar has built a reputation in this industry for delivering real technology - not just talking about it. We've recently commissioned not one, but two of the largest space propulsion testing chambers in the UK, if not all of Europe. Pulsar is now an international space propulsion testing powerhouse, and we have ambitious plans to grow rapidly from here."

Based in New Jersey.

Princeton Satellite Systems, Inc. is a small company specializing in advanced aerospace and energy technology. Our agility and focus on software development enables us to rapidly develop innovative solutions to a wide range of exacting control problems. Our commercial software products enable our customers to pursue the same types of demanding, state-of-the-art applications.