The usual way to check whether an unusual exhaust shape is worth anything is to just run it and measure, and that is exactly the problem this build tackles. Engines And More designed a 3D printed aerospike for a triple stage EDF purely to test thrust performance, wanting to see how it differs from a normal exhaust. The result was 370 grams of thrust on 2S, which for a first look at this setup seems like a solid number to work from.
The engine itself is a multi-stage compressor assembly built mostly from white filament, put together as segmented cylindrical sections fastened with metal nuts and bolts. One end tapers into a central exhaust nozzle, while the other has an open circular intake. Motor wiring runs up into the underside of the white housing, and heavy-gauge red and black power leads end in a yellow-and-red DC power connector.
For testing, the whole assembly was mounted on a wooden sliding carriage rig, with strings attached to make the airflow visible. A digital kitchen scale handled the thrust measurement, and an orange cordless drill was used to fit the aerospike nozzle to the exhaust end. The engine sits on a black 3D-printed display stand with two curved support uprights on a flat base, and the electronic speed controller with its ribbed heatsink is mounted inside the lower section of that stand.
One interesting trade-off: the aerospike exhaust area is 20% smaller than the third stage exhaust, done to keep pressure inside and avoid a vacuum. Thrust is currently low because the compressors are high capacity axial units, and a similar aerospike with a normal cone only managed 130 grams six months ago. The normal shape for this EDF still needs printing, and a comparison test with the same exhaust area is planned next. The current unit is also 80mm, up from a previous 74mm EDF.
Project by Engines And More. Watch it on their YouTube channel: