Quite a cool design, if I understood it correctly it switches the big classical cone-shaped nozzle into a lot of small nozzles nestled against a central spike, with the surrounding air forming the other half of the (now virtual) nozzle. Weird and almost magical, what's not to like? :)
What's not to like is that it's weird and almost magical.
First, let me say that I really hope they succeed. I want to see more people doing cool stuff in this area.
However, it seems like the opposite of SpaceX and on a similar path as the great spaceflight failures of the past few decades. Firefly is pushing the envelope with composite construction, an unconventional fuel, and an engine design that's never flown to space before.
SpaceX's main innovation is that they're boring. They have boring engines and boring rocket designs and they aim for cheapness and known quantities. Even their unprecedented first-stage reusability program is mainly innovative in how boring it is. Instead of screwing around with lifting bodies or jet engines or delta wings or anything like that, they're just taking a regular first stage rocket, slapping some legs on it, filling it with extra fuel, and giving it some fancy software.
I'd love to see major innovations succeed in space, but I think SpaceX has the right approach. Don't be fancy, just do stuff that obviously works, get it to the point where you can fly it regularly, and then iterate. There have been so many past attempts to revolutionize spaceflight through fancy new technologies and they've all failed miserably. I hope this one doesn't, but I'm not terribly optimistic.
Well, if they work hard on that design, get a half-assed rocket somewhat working and then still fail, while of course a sad moment for them, it would be still of great benefit to humanity. SpaceX or someone else could buy their research and experience and iterate further on that. So good luck to Firefly folks, but no matter how it ends, I think their work will still be a net gain for mankind.
Yup, pretty much. The traditional engine nozzle can only be optimized for maximum thrust at one altitude, while the aerospike maintains thrust efficiency at many altitudes, using as much as 30% less fuel at lower altitudes. Also, for the aerospike design, it doesn't have to be a series of small nozzles. The combustion gases can escape the combustion chamber via a ring. It's more difficult to cool this type of system and adds some weight, but it is an efficient alternative to the traditional engine nozzle for SSTO (single-stage-to-orbit) vehicles.
IIRC, the VentureStar was going to use a linear aerospike. With at least one combustion chamber on each side, it seems an easier design than a ring.
Their design seem to indicate they may want to pump air through the spike body to either cool it or as to use it as "bypass" volume in an inverted turbofan-like design. It's intriguing.
Quite a cool design, if I understood it correctly it switches the big classical cone-shaped nozzle into a lot of small nozzles nestled against a central spike, with the surrounding air forming the other half of the (now virtual) nozzle. Weird and almost magical, what's not to like? :)