Some discussion of solid (aero-) spike nozzles
here, including (see link in first post) a photo of a launch at Dryden.
Some discussion of solid (aero-) spike nozzles here, including (see link in first post) a photo of a launch at Dryden.
There were actually 2 flight tests of an aerospike design.
One was the LOX/Ethanol the other was the solid fuel design at Dryden.
AFAIK these constitute the only *flight* tests of the concept *ever* and had limited funding and instrumentation.
LASRE was the linear design on the SR71 as part of the X33 programme which never got to hot fire. the core hardware dates from 1973.
BTW NASA and the USAF tested actual aerospike hardware up to 250Klbs in the 1960s including both LO2/LH2 and the insanely dangerous LF2/LH2. One space tug design wrapped the aerospike segments around a conventional bell , both with throttling of 9:1, giving a 81:1 throttling range.
In 1974 the USAF's AFRL had Rocketdyne build a *flight* weight LH2/LO2 gimbaled unit with dual cooling in the 25Klb (RL10) class. Project director was Dr David Hwang (that's the Hwang of Hwang & Huzel).
It was later badly damaged with several segments destroyed in tests but the early tests confirmed performance at flight weight.
AFAIK these constitute the only *flight* tests of the concept *ever* and had limited funding and instrumentation.
I know they've been used on small, in-space monoprop engines. That has been for length limited applications, because the aerospike can be extremely short for it's expansion ratio.
I know they've been used on small, in-space monoprop engines. That has been for length limited applications, because the aerospike can be extremely short for it's expansion ratio.
Is there a reference for this work? They've certainly been *considered* for use in space specifically due to their short length, but I've never heard of them being deployed.
Some of the NASA space tug ideas looked at multiple "scarfed" conventional nozzles (like the RCS pod in the nose of the Shuttle) around an expansion surface while the plus with a conventional nozzle in the centre of it was another space tug concept.
Most organizations would view that as *very* high risk option.
Would it be possible to design a rocket engine with a variable geometry nozzle that could be adjusted on the fly to suit the performance needs of the altitude at that moment?
Would it be possible to design a rocket engine with a variable geometry nozzle that could be adjusted on the fly to suit the performance needs of the altitude at that moment?
Possible yes. Weight disadvantage, complex effects on nozzle flow, and hit to reliability outweigh advantages. Jet engine nozzles are convergent only. Much harder to do this on a convergent-divergent nozzle and maintain good nozzle flow.
California State University Long Beach has a flight test program that flew aerospike experiments several years ago. On this website, scroll down almost to the bottom of the page to see pictures.
Is there a reference for this work? They've certainly been *considered* for use in space specifically due to their short length, but I've never heard of them being deployed.
No. 
Can you elaborate at all, or is it up for publication? Even what country or body did it. An actual flight test on orbit changes the game quite a bit.
I can't really think of a reason for secrecy. People have talked about them (and their expected flight properties) for decades. Their *expected* benefits are quite well understood, as are their problems.
Can you elaborate at all, or is it up for publication? Even what country or body did it. An actual flight test on orbit changes the game quite a bit.
I can't really think of a reason for secrecy. People have talked about them (and their expected flight properties) for decades. Their *expected* benefits are quite well understood, as are their problems.
The fact that it's been used on flight was in some materials that have been publicly distributed (quick Google search doesn't turn it up, though). As for where, that's not for me to delve into. The secrecy is not about the engines, as they were very standard.
It doesn't change the game at all. The fluid mechanics of aerospikes are well understood. Having a small RCS thruster use an aerospike nozzle for packaging reasons doesn't provide any substantial data.
The fact that it's been used on flight was in some materials that have been publicly distributed (quick Google search doesn't turn it up, though). As for where, that's not for me to delve into. The secrecy is not about the engines, as they were very standard.
It doesn't change the game at all. The fluid mechanics of aerospikes are well understood. Having a small RCS thruster use an aerospike nozzle for packaging reasons doesn't provide any substantial data.
Technically it does not. But the fact they were used with *no* problems on orbit is the story. It breaks the classic "won't use them on my vehicle unless proven on orbit"/"can't launch them because they are not proven" mobius strip that seems to affect programme managers.
Hence my surprise. Packaging would have had to be *very* tight to consider something so (apparently) radical.
I would like to know where they were used. I haven't seen such documentation.
Bumping. Is there any reason Glenn's Spacecraft Propulsion Research Facility couldn't be used for testing aerospike nozzles over the entire range of conditions they would encounter during launch? I'm assuming yes, or they would have done it, but it would be good to know the precise reason.
California State University Long Beach has a flight test program that flew aerospike experiments several years ago. On this website, scroll down almost to the bottom of the page to see pictures.
That's what I would call a spike rather than an aerospike, the difference being whether the tail of the spike is solid, as in Cal State's experiments, or gaseous, as in just about all of the other engines discussed in this thread.
If the "virtual bell" of an aerospike nozzle is much wider than the diameter of the rocket, does that mean that you'll get the same drag you'd get with a physical nozzle of the same size? And how does this affect the possibility of parallel staging? Do the magical self-tuning powers of aerospikes extend to allowing multiple overlapping aerospikes without ill effects?
