← All work ENGINE 01 — 2024-25

BSEP Engine 1

Codename Maleficent

Regeneratively-cooled Inconel 718 bipropellant engine. 5.94 kN in January 2025: the UK student thrust record.

RoleEngine Lead

Integrated campaign 2025 →

Engine 1 at steady state on the AEL thrust stand, a bright plume with Mach diamonds streaming right across a dark test cell

Peak thrust

5.94 kN

Chamber pressure

23.55 bar

Hot fires

The engine

Engine 1 is a 5 kN regeneratively-cooled bipropellant engine running IPA and nitrous oxide, the University of Bristol's first student-built liquid engine. I led it as Engine Lead for BristolSEDS Experimental Propulsion, built for Race 2 Space 2024. Design point: 5 kN at 20 bar chamber pressure, O/F of 3, 0.64 kg/s fuel and 1.93 kg/s oxidiser through a like-like impinging doublet injector. Throat 48.13 mm, expansion ratio 3.36, chamber 119.6 mm across and 307.6 mm long. The chamber is printed in Inconel with regenerative channels, film cooling and 2% PDMS in the fuel as an ablative additive. Minimum safety factor along the engine: 3.37 in the wall, 3.24 in the channels.

CAD section through the chamber showing the converging-diverging contour, the cooling channels in the wall and the injector manifold at the head — Section: chamber, cooling channels, injector manifold.

The Inconel chamber standing on its build plate straight off the printer, rough grey surface and bolt ring at the base — Chamber fresh off the printer.

Chamber stress components plotted against axial position with the yield strength line above them, von Mises peaking at the throat — Wall and channel stress along the engine axis against yield.

Wall and channel safety factor along the engine axis, both dipping to a minimum just past 3 at the throat — Safety factor along the axis. Minimum 3.37 wall, 3.24 channel.

Three burns in one day

10 January 2025, Airborne Engineering's test cell at Westcott. Three hot fires of about 3 s each, stepping the flow rates up between them. Test 1 aimed to match the design flow rates and gave 4.35 kN at 17.48 bar. Test 2 aimed for the design chamber pressure and gave 4.96 kN at 19.62 bar, within 1% of design thrust. Test 3 was the capability demonstrator: 5.94 kN at 23.55 bar, 19% past design thrust, with no damage to the chamber. All figures are means over 1.5 to 3.0 s of each burn, recomputed from the raw DAQ files and matching the test report.

Thrust against time for the three AEL hot fires overlaid: three ascending plateaus at 4.4, 5.0 and 5.9 kN with the 5 kN design line — Three burns, 10 Jan 2025. Design line at 5 kN.Data: Airborne Engineering DAQ

Chamber pressure against time for the three AEL hot fires overlaid, plateaus at 17.5, 19.6 and 23.6 bar with the 20 bar design line — Chamber pressure, same three burns. Design line at 20 bar.Data: Airborne Engineering DAQ

Test 1, 4.35 kN. No audio, AEL cell camera.

Test 2, 4.96 kN at 19.6 bar. Design point hit.

Test 3, 5.94 kN. Capability demonstrator.

Every camera on the three burns

Each burn was covered by the cell camera, a GoPro close in on the stand and a second camera from the side, plus a downrange angle for Test 3. The GoPro cuts run the full sequence, sparkler to vapour; the second-camera clips are tight on the burn itself.

Test 1 from the GoPro, ignition through shutdown. 4.35 kN at 17.48 bar.

Test 1, second camera.

Test 2 from the GoPro. 4.96 kN at 19.62 bar, within 1% of design thrust.

Test 2, second camera.

Test 3, second camera. 5.94 kN at 23.55 bar.

Test 3, refocused on the shock train.

Test 3: 5.94 kN

Test 3 ran at 23.55 bar and an O/F of 3.52; Isp 179.8 s. At steady state the plume carries a train of Mach diamonds. The detail plot puts thrust, chamber, injector and delivery pressures and both propellant mass flows on one time axis; the six-frame strip is the slow-motion camera from ignition through steady state to shutdown. 5.94 kN set the UK student thrust record.

Second 4K still of the Test 3 plume, the Mach diamond train sharply resolved along its length — Test 3, Mach diamonds down the plume.

Three-panel detail of Test 3: thrust, chamber, injector and delivery pressures, and IPA and nitrous mass flows against time — Test 3: 5.94 kN, 23.55 bar, O/F 3.52.Data: Airborne Engineering DAQ

Vertical strip of six frames from the slow-motion camera: faint ignition, growing plume, steady Mach diamonds, then the shutdown fireball — Ignition to steady state to shutdown, six frames from the slow-motion camera.

Test 3 downrange at dusk: 5.94 kN lights the cell.

Test 3 from outside the cell doors.

One millisecond at a time

The slow-motion camera ran at 1000 fps on Test 3. Ignition shows the first flame leave the nozzle and the shock diamonds settle into place along the plume. Shutdown is the reverse: the plume collapses and a fireball rolls around the nozzle. Each clip here is a short cut of a much longer transient. The still is my pick from the slow-motion footage.

Ignition at 1000 fps, shock diamonds forming.

Shutdown at 1000 fps.

Single 1000 fps frame of the Test 3 plume, diamonds visible as bright knots in a pale exhaust against a dark cell — One frame at 1000 fps.

Test day

Three burns, one afternoon in the Airborne Engineering cell at Westcott. The engine bolts to a horizontal thrust stand with the nozzle pointing out of the open cell doors, thermocouples and pressure transducers wired back to the AEL DAQ, and a test-ID board on the back wall that stamps every firing.

Wide view of the AEL test cell with Engine 1 mounted on the thrust stand in front of the blue Airborne Engineering instrumentation wall — Engine 1 in the AEL test cell.

Nozzle-side close-up of Engine 1 on the thrust stand, sensor wiring and feed lines running to the head end — Nozzle side, on the thrust stand.

Ethan standing beside Engine 1 on the thrust stand in the AEL test cell — Test day.

Then the full stack

In September 2025 Engine 1 fired again at Astron Systems, this time as part of HyPower's complete launch vehicle for the EuRoC qualification campaign: vertical tank, horizontal engine. Hotfire 1 lost nitrous to a leak during fueling and gave a 1 s burn at 3.7 kN. Hotfire 2 was the full-duration run, 7 s at 4 kN tapering to 3.6 kN, enough for 30.7 m/s off the rail against EuRoC's 30 m/s requirement. Hotfire 3, with the regulator up to 50 bar, was a 0.86 s partial fill that peaked at 5.58 kN. That campaign has its own page.

Integrated Test Campaign 2025