An aerospike-ish rocket engine to fly for real.

[Galane]

Assuming Firefly Space Systems has a lifetime longer than its insect namesake. http://www.gizmag.com/firefly-alpha-aerospike-launch-vehicle/32892/

[Streetwind]

Interesting. There's so little hard info about aerospike engines and their pros and cons available, on account of there being no real finished engines to use in comparisons. I hope we can get a bit more out of this one

[Galane]

Looks like a hybrid design of multiple somewhat conventional rocket nozzles in an aerospike styled shroud. Definitely not an annular nozzle, pure aerospike design in the renderings.

[Streetwind]

That's actually how NASA built their linear aerospike. They had several dozen tiny rockets lined up next to each other, burning down along the spike. This is the same thing, except circular.

Having a single combustion chanber with a ring exhaust is actually a bad idea because you need to hold the central plug in place somehow. That generally means having metal struts in exactly the spot where the engine burns the hottest and hardest. That tends to melt anything that isn't actively cooled.