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Aerospike Engines - And why they are not used...

Grendal

SpaceX Moderator
Jan 31, 2012
6,037
7,674
Santa Fe, New Mexico
Thorough discussion of the aerospike engine by Tim Dodd, the Everyday Astronaut, design and why it is not used. Should hopefully be interesting for those who enjoy the details and fundamentals of rocket engines. EA spoke with Elon about aerospikes in his interview at the Starship update in Boca Chica recently.

 

Electroman

Supporting Member
Supporting Member
Aug 18, 2012
6,400
7,551
TX
For lazy bums like me, without going into the minutia can someone post a one paragraph TLDR of what is Aerospike engine and how it fundamentally differs from the normal (Bell shaped engine?) one.

Thanks
 

Uncle Paul

Well-Known Member
Nov 1, 2013
6,299
7,598
Canyon Lake,CA
Take away is that Aerospike has some exhaust control advantages, the cost to develop them is high and they are much more complicated, making them much heavier. The benefits in power are offset by weight, reliability and cost.
 
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bxr140

Active Member
Nov 18, 2014
2,993
4,759
Bay Area
For lazy bums like me, without going into the minutia can someone post a one paragraph TLDR of what is Aerospike engine and how it fundamentally differs from the normal (Bell shaped engine?) one.

A traditional nozzle can only be geometrically optimized for only one altitude/pressure, so total thrust is sub-optimal throughout flight except for one instant.

An Aerospike better optimizes thrust performance over a wider range of altitudes and especially low altitudes, essentially using the changing ambient pressure and a bit of pixie dust to continuously self-adjust exhaust flow to an optimized geometry. The end result is better efficiency throughout flight and more thrust when you need it most--at low altitudes when the vehicle is the heaviest.
 
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Uncle Paul

Well-Known Member
Nov 1, 2013
6,299
7,598
Canyon Lake,CA
Tesla says that since they are at low altitude for very little time, the complexity of the Aerospike, the extra weight and the lower reliability makes if not the best for them. Since they do not need the extra power, it is better for them to just use standard rockets. Bell housing with the Aerospike would be too big for them to gimble properly for return to Earth vectoring.
 

RDoc

S85D
Aug 24, 2012
2,755
1,706
Boston North Shore
I'm still amazed that NASA chose the Venture Star, way back when, as the Shuttle replacement. Unless, of course, the whole point to the exercise was to NOT replace the Shuttle.
 

Electroman

Supporting Member
Supporting Member
Aug 18, 2012
6,400
7,551
TX
A traditional nozzle can only be geometrically optimized for only one altitude/pressure, so total thrust is sub-optimal throughout flight except for one instant.

An Aerospike better optimizes thrust performance over a wider range of altitudes and especially low altitudes, essentially using the changing ambient pressure and a bit of pixie dust to continuously self-adjust exhaust flow to an optimized geometry. The end result is better efficiency throughout flight and more thrust when you need it most--at low altitudes when the vehicle is the heaviest.
Thanks. This feels like kind of roughly synanomous to multiple gears on an ICE to to provide optimal torque at various speeds.
 

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