For those of you curious about how an Aerospike engine works...

[HafCoJoe]

This gem popped up after watching a video someone posted on the KSP Facebook group. It explains a ton about the linear aerospike. Though KSP includes a circular Aerospike, most of it's concept operates the same way.

Feel enlightened yet?

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If a mod thinks this would fit better in science or a different forum feel free to move it. I just thought that the general populace should know more about this thing.

[Whackjob]

Very informative.

The poofy 80s hair can stay in the 80s, though.

[Wallygator]

At 00:19 the dude flipping his hand-held igniter in the air and pocketing it. Hilarious!

[xtoro]

Cool stuff! Explains why the ISP is similar in atmo and in vacuum, which I didn't know. Makes sense now though. But I wonder if they should have even higher ISP when compared to bell housing engines.

[HafCoJoe]

Before I saw this I had a general idea of why it works but this video makes my previous knowledge trivial

[Streetwind]

Whenever I see one of these promotional videos explaining why the linear aerospike is so great and how much it has already been developed, I really don't understand why nothing ever came of it...

[ToyotaTim]

Whenever I see one of these promotional videos explaining why the linear aerospike is so great and how much it has already been developed, I really don't understand why nothing ever came of it...

This, I also want to know what happened with the aerospace nowadays... :/

[Darnok]

http://www.gizmag.com/firefly-alpha-aerospike-launch-vehicle/32892/

[SpacedCowboy]

A five hundred million dollar high tech pea shooter.

[Nich]

Wow I had no idea the aerospike was so old.

[cantab]

Whenever I see one of these promotional videos explaining why the linear aerospike is so great and how much it has already been developed, I really don't understand why nothing ever came of it...

There's got to be a catch, indeed. Here's one discussion of rocket nozzles in general, http://web.archive.org/web/20070517170702/http://www.pwrengineering.com/articles/nozzledesign.htm , mentions performance issues at low subsonic speed. Perhaps a bigger issue is cooling, I can see the aerospike design being more challenging to cool if you don't want a simple ablative nozzle.

[OhioBob]

Cool stuff! Explains why the ISP is similar in atmo and in vacuum, which I didn't know. Makes sense now though. But I wonder if they should have even higher ISP when compared to bell housing engines.

Aerospike engines are better than bell nozzles over a broad range of atmospheric pressure, but they are typically less efficient than a bell nozzle when operating in the environment for which the bell nozzle has been optimized. Therefore, if the engine is to operate in only one environment, e.g. a vacuum, it is better to use a bell nozzle. Aerospikes should be considered only when they are to operate through a region of significantly changing ambient pressure.

[Cydonian Monk]

Wow... You could replace most of the narration of that video with the Turboencabulator script and still have the same video. Aside from quoting performance numbers, that air pressure forming a synthetic bell graphic, and saying how much it cost for them to go nowhere, the video really doesn't say much.

[Streetwind]

There's got to be a catch, indeed. Here's one discussion of rocket nozzles in general, http://web.archive.org/web/20070517170702/http://www.pwrengineering.com/articles/nozzledesign.htm , mentions performance issues at low subsonic speed. Perhaps a bigger issue is cooling, I can see the aerospike design being more challenging to cool if you don't want a simple ablative nozzle.

Well, I considered that too, but they did say in the video that they successfully did a 540+ second test firing - AKA over 9 minutes, pretty much a full burn from pad to orbit. If they were able to keep it cool during that test, it would have been kept cool during flight.

Theoretically.

[Frozen_Heart]

Aerospike engines are better than bell nozzles over a broad range of atmospheric pressure, but they are typically less efficient than a bell nozzle when operating in the environment for which the bell nozzle has been optimized. Therefore, if the engine is to operate in only one environment, e.g. a vacuum, it is better to use a bell nozzle. Aerospikes should be considered only when they are to operate through a region of significantly changing ambient pressure.

Would theoretically be a better launch engine though. Aerospike first stage, bell second stage.

I assume the main reason these haven't been developed is simply funding.

[Kryten]

Whenever I see one of these promotional videos explaining why the linear aerospike is so great and how much it has already been developed, I really don't understand why nothing ever came of it...

Too expensive to be economical for an expendable vehicle, still not efficient enough to make reusable SSTO feasible.

[Red Iron Crown]

Too expensive to be economical for an expendable vehicle, still not efficient enough to make reusable SSTO feasible.

Might be useful for something staged similarly to the STS, where the main liquid engines burn for the entire ascent even though it's a multistage design.

[HafCoJoe]

Thanks for moving it Sal xD It's job was done. I'm glad it got the views that it did

[Kryten]

Might be useful for something staged similarly to the STS, where the main liquid engines burn for the entire ascent even though it's a multistage design.

Simpler aerospikes like the plug-nozzle design can also be useful for rockets with simple, low-pressure engines, as the gain in Isp relative to bell-nozzle designs increases with decreasing chamber pressure. That's why firefly are trying it with their pressure-fed alpha vehicle, and why a few obscure Ilse groups such as Garvey worked on them.

[benzman]

One advantage that was claimed for them was that you could make a big engine by mass-producing small ones and stacking several in a line. And you could 'throttle' it by turning a few off.

[fortraan]

On 8/15/2015 at 7:36 AM, Streetwind said:

Whenever I see one of these promotional videos explaining why the linear aerospike is so great and how much it has already been developed, I really don't understand why nothing ever came of it...

Because we have stuff like SRBs. But, with reusable spaceplanes such as Reaction Engines Ltd.'s SKYLON being developed we may see a spaceplane that uses an aerospike engine.

[fredinno]

On August 15, 2015 at 5:36 AM, Streetwind said:

Whenever I see one of these promotional videos explaining why the linear aerospike is so great and how much it has already been developed, I really don't understand why nothing ever came of it...

Cooling issues, higher costs, and the fact engine development is VERY expensive. That's why Atlas V uses RD-180.

On August 15, 2015 at 0:57 PM, Kryten said:

Simpler aerospikes like the plug-nozzle design can also be useful for rockets with simple, low-pressure engines, as the gain in Isp relative to bell-nozzle designs increases with decreasing chamber pressure. That's why firefly are trying it with their pressure-fed alpha vehicle, and why a few obscure Ilse groups such as Garvey worked on them.

Wouldn't that still make the rocket uneconomically expensive?