The engine
A compact, water-cooled rotating detonation combustor for liquid oxygen and liquid methane. Small enough to instrument closely, and built to answer one question well: does the wave hold, and what does it deliver?
From design record r3. Values change only with test-facility data or a written review.
The layout is decided. Contours, wall thicknesses and orifices are not, and stay open until the facility numbers are in writing.
Schematic section. Shows the decided layout, not released geometry.
Meters liquid oxygen and liquid methane into the channel. Replaceable, so the same head can fire every chamber length.
About 30% pressure drop at 350 psia. Orifices not yet drawn.
The ring the detonation front runs around, between the outer body and the centerbody.
85 mm outer diameter, 5 mm gap.
Deionised water runs through both the outer wall and the centerbody so the copper survives a sustained firing.
Channel cross-section and manifolds under review.
Contracts the annular flow to a single throat and expands it to make thrust.
Expansion ratio 4 for screening. 29.19 mm ideal throat.
A separate starter that fires a detonation into the channel, then is isolated so the wave has to sustain itself.
Mixture, energy and qualification still to define.
Shows that the wave is rotating and measures what the engine delivers.
Four dynamic-pressure stations, 250 kS/s per channel or faster, plus thrust, flow and chamber pressure.
Each choice below answers the research question directly. The alternatives are real engines too; they just answer different questions.
The research question is whether a liquid-methane spray can hold a rotating detonation. Methane is also the clean, reusable fuel of modern upper stages.
Set asideIsopropanol and ethylene would light more easily, but each answers a different question and needs a different injector. RP-1 was set aside for soot.
While the combustor itself is the experiment, the feed system should be as simple as possible.
Set asideTurbopumps belong to a later generation.
Large enough to be a real engine, small enough to instrument closely. Tests will span 1.5 to 2.5 kN.
Set asideFilling the largest envelope the facility could allow.
A firing of five seconds or more rules out heat-sink hardware, which survives well under a second.
Set asideHeat-sink and ablative chambers. Regenerative methane cooling comes later.
Starting the wave from an independent, isolated source lets us show the detonation sustains itself.
Set asideA compact internal igniter, left for a later article that learns restart.
One injector head, three hot-section lengths: 38, 51 and 64 mm. Every firing adds a point to one clear experiment.
Set asideOne long firing at a single, arbitrary length.
Each belongs to a later generation. Stacking them onto the first engine is how ambitious student engines stall.
The experiment is how chamber length changes the wave. The injector head stays fixed while the distance from injector face to throat changes between runs.
A shorter chamber is lighter and loses less heat. A longer one gives the wave more room to settle. Measuring both ends of that trade on one head is worth more than one long firing at a single point.
We borrow methods from published work, not hardware. None of these are copied, and none of their numbers are our design loads.
| Engine | What it is | What we take from it |
|---|---|---|
| NASA MARLENMarshall Space Flight Center | Gaseous methane and oxygen, water-cooled. | The chamber-length experiment, modest contraction and water calorimetry. |
| AFRL / Purdue 76 mm RDREAir Force Research Laboratory | Gaseous methane and oxygen. | A channel gap of about 5 mm and a culture of proving the wave, not assuming it. |
| NASA GRCop-42 RDREMarshall Space Flight Center | Printed copper, long-duration firings. | Print-then-CT-scan discipline for cooled copper. |
| Purdue water-cooled RDREPurdue University | Around 118 starts on one engine. | A water loop as the way a university engine survives repeated firings. |
| ARIS PEGASUSETH Zurich student team | Liquid oxygen and liquid propane, 750 N first fire. | Proof a student bi-liquid RDRE can detonate, and a disciplined fire-day process. |
Restart and long life come later. The first article has to deliver these three results together.
| Result | What has to be true | How we will show it |
|---|---|---|
| Prove rotation | A detonation front is still travelling around the channel after the starter is isolated. | Four unequally spaced dynamic-pressure stations, sampled at 250 kS/s per channel or faster. |
| Measure thrust | Calibrated numbers for how the engine performed, not just whether it lit. | Calibrated thrust stand, propellant flow metering and chamber pressure. |
| Survive the run | The hot section holds together through a sustained firing of at least five seconds. | Water cooling on both channel walls and a post-test inspection. |
Each stage retires a specific risk before the next one starts.
Freeze the first article through independent numerical and design review.
In progressBuild the copper hot section and CT-scan every cooling channel.
NextFlow water and propellant simulants, then check every valve, sensor and abort.
PlannedFire, measure, inspect, and publish what the hardware showed.
Planning target: spring 2027These block a drawing release. Each is a place where outside help moves the engine forward.
Help with oneSettle one channel cross-section, then choose between printed GRCop-42 with CT inspection and machined OFHC copper.
Help that fitsMetal additive, CT inspection
Bound the local heat flux on both walls for a liquid injector. Most published data is for gaseous propellants.
Help that fitsAnalysis and mentorship
Lay out the orifices and define a flow test that checks the design independently of its own assumptions.
Help that fitsCNC and microdrilling, cold-flow
Choose the mixture and energy, and qualify the starter on its own stand before it meets the engine.
Help that fitsSpecialist engineering
Enough channels sampled at 250 kS/s or faster, with each sensor port's response measured.
Help that fitsSensors and data acquisition
Written numbers for delivered propellant flow, flange pressure, cooling water and the engine mount.
Help that fitsTest facility
Resonance needs manufacturing, measurement and research partners, and students who want to own a piece of the engine.