Aerospike Rocket Engines- You learn something new every day.

So, yesterday I heard that a new startup in Texas was looking to build a launcher for small satellites. The company is named Firefly, and of course, a quick google search found mostly pics of Serenity and Mal Reynolds. But one thing caught my eye, was a reference to aerospike engines, which the company plans to use. That lead to the question, what the hell is an aerospike engine?

You’re familiar with a liquid fueled rocket engine, right? Let’s look  at a typical engine. The is the RS-25, a derivative of the Shuttle Main Engine intended for the future SLS platform.

Pumps mix fuel and oxidizer in a combustion chamber that then flows out the bell. Simple enough.

Aerospike engines kinda turn the bell idea upside down. The flame exhaust goes outside of a wedge, and uses ambient air pressure to shape the plume.

Confused? So was I.


In spite of extensive testing and several developmental models, the aerospike has never flown to space. Whether Firefly Systems changes that remains to be seen.

4 thoughts on “Aerospike Rocket Engines- You learn something new every day.”

  1. While the aerospike is kind of cool, it’s kind of ironic that they’re emphasizing the low-cost aspect of it as being important to the X-33 that was eventually canned due to basically infinite cost overruns. I’m still bitter because they should have picked the Douglas design which, not only was actually manufacturable, unique among the X-33 proposals, but which had actually flown scale-model tests.

    That’s when I figured out that NASA was basically useless for developing new hardware.

  2. Ah, the eternal promise of the aerospike!
    For even more fun: back in the mid-90s, someone (Gary Hudson?) tossed out an idea: take a basic round aerospike, mount it on a suitable bearing and whatnot, and cant the combustion chambers so it spins, thereby becoming its own high-pressure propellant pump.
    I still wanna try that one. Might make thrust vectoring a little interesting, though….

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