Boom fires up the engines on XB-1 supersonic demonstrator

The Boom Supersonic XB-1 engines are installed and running. The company released an update on the flight test program progress, including details on the installation and first test runs of the three General Electric J85 engines on board.

The initial round of tests start with just one engine at idle speed. This setting allows for confirmation of basic functionality, as well as testing of other on-board systems powered by the engines.

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From there Boom will activate all three engines. Eventually it will proceed to running at full throttle, including the afterburners. Various throttle shift rates will also be tested.

All of this testing happens with the plane on the ground. Most of it will come without the aircraft moving at all. The key initial tests are run with the plane tethered to the ground via reinforced anchors to ensure it doesn’t move, even at full throttle.

But the plane will ultimately taxi under its own power at Denver’s Centennial Airport where it is under development. The company expects a max ground speed of around 70 miles/hour during the initial round of testing.

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Once it is satisfied with the engine integration and test results, Boom will load XB-1 on to a trailer and dive it to Mojave. The larger, more remote runway will allow for higher speed ground tests (~155 mph). And, ultimately, the company expects to operate the test flight program from Mojave as well.

But not the Overture supersonic jet

While these are all exciting milestones in the development of the XB-1 aircraft, very little of what it demonstrates will translate directly to Boom’s planned Overture supersonic passenger aircraft.

The body shape will be completely different on Overture. And the J85s will not power the much larger Overture aircraft. Indeed, Boom still has not released details on what engines will power its proposed supersonic jet. It did sign an agreement to further research options with Rolls Royce in July 2020.

Also of note: While Boom promises that Overture will run on sustainable aviation fuel (SAFs) the J85s will run on traditional kerosene throughout the test and demonstration flight process. The company says it will purchase carbon offsets to account for this fuel burn. 

The timelines for XB-1’s first flight or further developments with Overture remain unclear. And United’s theoretical 2029 operational supersonic fleet remains relatively unlikely. But still probably possible.

More on Boom’s evolution towards supersonic service:

• Behind the scenes with Boom Supersonic
• Supersonic sound standards set; Boom schedule slips
• United Airlines plans supersonic Boom with new order
• Engine selection “core” to Boom Supersonic’s success