The 150 km Artillery Round That's Trying to Make Howitzers as Dangerous as Missile Launchers

On April 21, 2026, Tiberius Aerospace fired a liquid-fuelled ramjet out of a standard NATO 155mm howitzer at a range in New Mexico, lit the engine in flight, and called it a world first. The round in question is the Sceptre, formally designated TRBM 155HG, and the company claims it can reach 150 km with a circular error probability of under 5 metres. If those numbers hold up in extended testing, a battery of standard howitzers would be able to reach targets that currently require cruise missiles or HIMARS to touch. That's a big "if." But the fact that the engine actually ignited after surviving 18,000 g at launch is not nothing. Let's unpack what Sceptre is, where it stands right now, and what still needs to be proven before anyone should take the claimed range seriously.

What Sceptre Actually Is

Sceptre is a 155mm artillery round with a liquid-fuelled ramjet engine built into it. The ramjet sits in the nose section, fed by a ring-shaped fuel tank in the tail, and it accepts diesel, JP-4, or JP-8, meaning most military logistics chains already carry compatible fuel. The round is 1.55 metres long, weighs 47.5 kg, and fits in any NATO-standard 155mm howitzer using existing propellant charges. No new gun required.

The basic physics of how it works: when the gun fires, Sceptre exits the barrel at approximately Mach 2. That initial velocity is fast enough to start the ramjet, which then accelerates the round to Mach 3.5 within about six seconds. It climbs to over 65,000 feet before gliding down on canards toward the target. Tiberius claims a CEP of 3.5 to 5 metres depending on guidance package, using a hybrid GPS and inertial navigation system.

That 18,000 g figure is not trivial. It's the reason ramjet rounds have historically been difficult to build. Every electronic component, every fuel line, every actuator has to survive a launch force that would destroy most off-the-shelf hardware. The April 2026 test was specifically designed to verify that Tiberius had solved this problem. They apparently had, at least at short range.

What the April 2026 Test Actually Proved

Here is where it's worth being precise, because the coverage around this test has varied from careful to very credulous. What the New Mexico test confirmed: the round survived the gun launch, the ramjet ignited after barrel exit, the stabiliser and canards deployed correctly, and the basic flight profile worked. Tiberius CEO Chad Steelberg described it as proving both the propulsion concept and the broader engineering approach.

What the test did not confirm: the 150 km claimed range, precision at distance, or GPS accuracy under real-world conditions. The test was conducted at a private range where detailed results were not publicly disclosed. Tiberius itself described the next phase as "extended-range testing and certification." In other words, what happened in April was a proof-of-concept for the hardest mechanical problem, which is getting a ramjet to survive artillery launch and ignite cleanly. The range and precision claims are still computational projections until longer test firings validate them.

Getting a liquid-fuelled ramjet to survive 18,000 g and light up is the hardest part of the engineering problem. It doesn't mean the 150 km range claim is validated. Those are two very different things.

This matters because the history of ambitious artillery programmes is littered with rounds that performed spectacularly in early tests and quietly failed later. The US Army's ERCA programme put a 70 km Excalibur round on target in controlled conditions in December 2020, declared it a breakthrough, and then cancelled the programme in March 2024 when the barrel wore out after a few dozen shots and the system proved unworkable in the field. Early test milestones in artillery development are necessary but not sufficient evidence of a combat-ready system.

How Sceptre Compares to What's Already in the Field

To understand why Sceptre is interesting, you need a clear picture of what it's competing against, because "150 km from a howitzer" is genuinely different from everything currently in service.

The Excalibur costs around $178,000 per round in its current form. Vulcano holds the practical combat record after a Ukrainian crew reportedly used it to hit a target at 70 km from a Polish Krab howitzer in August 2022. Both are impressive systems that have proven themselves in actual combat. Sceptre hasn't proven anything at range yet. But if the price point Tiberius quoted holds, around $52,000 per round without payload, and if the range numbers validate, those two data points together would represent a genuinely different value proposition.

There is also a competing ramjet round from Nammo and Boeing, developed under the US Army's ERAMS programme, that targets a similar 150 km range using solid fuel propulsion instead of liquid. The solid-fuel approach is more conventional and avoids the in-field fuelling complexity that Sceptre requires, but it also loses some of the logistics flexibility Tiberius claims as an advantage. Both programmes are still in development. Neither has confirmed actual range at target with accuracy data.

The Problem Everyone Should Be Talking About: GPS Jamming

The most important context for any GPS-guided artillery round right now is what happened to Excalibur in Ukraine. When it was first deployed in 2022, Excalibur had a near-perfect hit rate. By mid-2023, Ukrainian assessments reportedly showed the success rate had dropped to somewhere between 6 and 10 percent. Russian electronic warfare systems were jamming the GPS signal, and without accurate satellite updates the inertial navigation system accumulated errors fast enough to send rounds well off target. Ukraine stopped using Excalibur entirely for a period. The US eventually had to retool the guidance software.

Sceptre uses the same GPS plus INS combination as Excalibur's baseline. Tiberius does claim that flying at 65,000 feet puts the round "above typical jamming range," and there is some validity to that argument. GPS jamming is more effective closer to the ground because the jammer's signal has less atmosphere to compete with. But GPS signals can still be spoofed or overpowered at altitude, and the longer a round is in the air, the more exposure it has. At 150 km range, Sceptre is going to be airborne for considerably longer than Excalibur at 50 km.

At 150 km range, Sceptre is in the air longer than Excalibur at 50 km. More time in the air means more time for electronic warfare to work on it.

Tiberius's published specifications mention EMI shielding at the component level and at wiring harness interfaces, and the company describes the guidance architecture as modular so that anti-jamming upgrades can be swapped in. But the specific measures, whether it uses controlled reception pattern antennas, multi-constellation navigation, or any terminal-phase optical correction, have not been disclosed publicly. For a round that is being positioned partly as a solution for contested battlespaces, that gap in the public specification is the most important open question. Before committing to this system, any defence procurement office should be demanding detailed answers on EW resilience, not just range claims.

The Compatibility Argument Is Actually Sceptre's Strongest Card

Here is the thing about Sceptre that gets underplayed in most coverage: you do not need to buy anything new to use it. Any NATO army with a 155mm howitzer can, in theory, pick up Sceptre rounds, load them into existing guns with existing propellant charges, and immediately have access to 150 km of range. That is not how it works with HIMARS, which needs its own launcher, its own logistics chain, and its own crew training. It is not how it worked with ERCA, which required a completely new barrel.

Tiberius built the round with only 68 unique components in the main structure, mostly from the same titanium alloy, which is a genuinely interesting supply chain design choice. The liquid fuel model is more complex to operate than a solid-fuel round, since you need the company's fuelling station kit on site, but the claimed 20-year shelf life without fuelling until needed reduces the storage risk that comes with solid-propellant ammunition. These operational details matter enormously in procurement decisions, even if they get less attention than range and CEP numbers.

The UK Ministry of Defence signed a trials contract with Tiberius in September 2025, running through late 2025, and the US Defense Innovation Unit is facilitating independent verification testing. Both are prudent low-cost bets on a technology that, if it works, would be transformative. Neither represents a procurement commitment. Think of them as paying for rigorous homework before writing a bigger cheque.

What Still Needs to Happen Before Sceptre Becomes a Real Weapon

Tiberius Aerospace was founded in 2022. That's worth holding in your head. The company has moved quickly, the April 2026 test was a genuine technical milestone, and the UK MoD and US DIU involvement adds credibility. But going from a successful engine ignition test to a round that armies actually order and field is a long road, and it's a road that has ended in failure more often than not for ambitious artillery projects.

The remaining tests that need to happen are substantially harder than what April demonstrated. A short-range flight with engine ignition is one thing. Confirming 150 km range, accuracy at that distance, guidance system performance under electronic warfare, and consistent behaviour across different atmospheric conditions and gun types is a completely different level of validation. Then there's production: Tiberius has announced a licensing model where it retains IP and other manufacturers produce the round, which is an interesting approach but unproven at scale in defence.

What I'd want to see before calling this a breakthrough rather than a promising prototype: a publicly verified test at range greater than 100 km with documented CEP, independent testing of the guidance system under EW jamming conditions, and a named procurement customer committing to production quantity. None of those things have happened yet. The April test proved Sceptre is not vapourware. It did not prove Sceptre is what the press release says it is.

The Bigger Picture: Why This Class of Weapon Matters Right Now

The Ukraine conflict reshaped how Western militaries think about tube artillery. Before 2022, there was a real narrative in many defence establishments that precision artillery was a niche tool and that missiles were the future. What the war demonstrated is that artillery is the backbone of industrial-scale attrition warfare, and that the range gap between howitzers and missile systems is a critical vulnerability when you need fires at volume. HIMARS changed the war in 2022. But GMLRS rockets cost around $150,000 each, production is constrained, and they require specialist platforms.

A 155mm round that can reach 150 km from guns already fielded across the alliance, at a fraction of the cost of a missile, would directly address that problem. It would compress the depth at which rear-area targets feel safe. It would complicate an adversary's ability to keep logistics, command posts, and air defence assets behind a "safe" line. Those strategic implications explain why the UK MoD and US DIU moved quickly to fund Sceptre testing even when the programme is still early. The question is not whether this class of capability matters. It clearly does. The question is whether Tiberius Aerospace can actually deliver it at the performance and price they've claimed.

Where Sceptre Stands Right Now

Sceptre is a real round that has survived artillery launch and lit its engine in flight. That makes it more than a slide deck, and it puts it ahead of most comparable projects that never got this far. The company has UK MoD and US DIU backing, a published price target that undercuts the competition significantly, and a technical approach, flying high and fast to avoid jamming, that is at least plausible as a partial answer to the EW problem that plagued Excalibur.

But the gap between "the engine lit up on a short test range in New Mexico" and "battle-ready round clearing extended-range certification with validated EW resilience" is wide. Tiberius has announced it needs to move to larger ranges for the next testing phase, which is where the real numbers will either hold or fall apart. Anyone who has followed the ERCA programme, or any number of previous ambitious munitions projects, knows that this is exactly the phase where things get hard.

If you work in defence analysis or procurement, the honest position right now is: watch closely, fund the testing, and do not let the marketing outpace the evidence. Sceptre deserves serious attention. It does not yet deserve the certainty of a programme of record. If you want to track the programme's progress, Tiberius publishes test updates through their press room at tiberius.com and the UK Defence Journal has been running solid coverage of the UK government's involvement.