Aerospike Engines - Why Aren't We Using them Now?

Maybe if you included some content in your OP...rather than asking people to watch 15 minutes of tape that might be nothing but bullshit...

...you'd get better reaction.

You've watched the tape. Tell us what you've got to say. Otherwise sit here and talk to yourself. (Hope my comment gives your thread a boost.)
 
Frank Apisa said:
Maybe if you included some content in your OP...rather than asking people to watch 15 minutes of tape that might be nothing but bullshit...

...you'd get better reaction.

You've watched the tape. Tell us what you've got to say. Otherwise sit here and talk to yourself. (Hope my comment gives your thread a boost.)
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Oh dear, so you have to watch a video ffs!
 
Havana Moon said:
Oh dear, so you have to watch a video ffs!
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No I do not, actually.

Haven't...and won't.

I seldom do when someone is so lazy they just post a video without a reasonable OP accompanying.

My guess is lots of people do that.

Why not stop being lazy...if you have a point you think is worth making?
 
Frank Apisa said:
No I do not, actually.

Haven't...and won't.

I seldom do when someone is so lazy they just post a video without a reasonable OP accompanying.

My guess is lots of people do that.

Why not stop being lazy...if you have a point you think is worth making?
Click to expand...

If you don't want to watch it, then up to you! I know about them already, you don't.
 
Havana Moon said:
If you don't want to watch it, then up to you! I know about them already, you don't.
Click to expand...

I'll just say this, aerospike engines are far more efficient than rocket engines with conical nozzles. They were intended to be used to power single stage to orbit craft after the Space Shuttle, but are in a state of hiatus at present.
 
Aerospikes are generalist engines. But staging usually makes more sense, you can use engines that are more efficient in space, and launcher engines that are more effective in atmospheric conditions. Aerospikes would mainly be useful for an SSTO, because they'd remain recently efficient at all altitudes. but an SSTO in general has been sort of the white whale of the space industry. Also it's kind of pointless now that we have reusable staged rockets.
 
He kind of brushed over the x-33. The problem with SSTO's is that it's just marginally possible for them to fly themselves into space and carry any useful amount of cargo. It hurts a great deal to have to carry around a tank at all times. The X-33 tried to develop a novel new lightweight tank, but ultimately it still weighed so much that it couldn't carry any cargo into orbit, it would've only barely been able to lift itself into orbit empty and return. Clearly that is entirely useless. And that's what winds up happening with most SSTO's.
 
We Don't Do Vegetables said:
Aerospikes are generalist engines. But staging usually makes more sense, you can use engines that are more efficient in space, and launcher engines that are more effective in atmospheric conditions. Aerospikes would mainly be useful for an SSTO, because they'd remain recently efficient at all altitudes. but an SSTO in general has been sort of the white whale of the space industry. Also it's kind of pointless now that we have reusable staged rockets.
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There is nothing to stop multi-stage vehicles from using aerospike engines, at least for the first stage. In general a space vehicle fitted with an aerospike engine uses 25–30% less fuel at low altitudes. The Space Shuttle was going to use aerospike engines but was decided against reasons that are still clouded in mystery.

ARCA is carrying on the good work.

http://www.arcaspace.com/
 
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The first stage is the part of the rocket where efficiency actually matters *least* though, in terms of delta v (the total ability of the rocket to change its velocity). Like they intentionally use low isp, high thrust engines based on kerosene in the lower stage just to save on volume in most cases (which is much denser, but less efficient, than the hydrogen often used at higher stages). I can totally see why they wouldn't want to bother with an aerospike there, if it was just a little bit more unreliable or produced less thrust it likely wouldn't be worth it.

Whereas in the upper stage, efficiency increasingly becomes totally critical. Once in orbit you have all the time in the world to change your velocity, so you don't care as much about thrust. But every tiny little bit of extra fuel, requires many times that amount of fuel in the lower stages just to carry it into space.

The extreme version of this of course is the ion engine. Which provides about as much thrust as the force of a piece of paper falling on your hand, but has an isp like 10x anything you can get via chemical means. So it can send things very far out into space given enough time. Unfortunately if it were carrying humans the mass would be too much, it would take years and years to get anywhere and we simply can't wait that much time.

Aerospikes are definitely they are a cool technology though.
 
Tbh mainly all I know about aerospikes is that when I designed rockets with them in Kerbal Space Program, and calculated the delta-v of the resulting vehicle, it never helped out. Almost always there were better alternatives. I did once design an SSTO, but I went for SABRE type engines for that (which are *much* more efficient than aerospikes *while there's enough oxygen in the air for them to combust*), as well as an airplane type liftoff. Maybe I'll try again with an aerospike design.
 
We Don't Do Vegetables said:
Tbh mainly all I know about aerospikes is that when I designed rockets with them in Kerbal Space Program, and calculated the delta-v of the resulting vehicle, it never helped out. Almost always there were better alternatives. I did once design an SSTO, but I went for SABRE type engines for that (which are *much* more efficient than aerospikes *while there's enough oxygen in the air for them to combust*), as well as an airplane type liftoff. Maybe I'll try again with an aerospike design.
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The SABRE engine is truly impressive, especially the cooling system which uses hydrogen fuel to pre-cool the engine intake.

https://www.reactionengines.co.uk/sabre
 
My sabre engine design had the single most complicated launch profile of any vehicle I'd ever designed in the program though. I can't imagine how difficult an actual one would be for actual pilots. Basically you have to accelerate to absurd speeds in atmosphere, to the point where you are stressing the limits of the vehicle, in order to build as much velocity as humanly possible using the highly efficient airbreathing mode. To altitudes where there's barely enough air for the engines to even function, but at speeds such that the craft is burning up even in the thin atmosphere, similiar to reentry.

Then you turn on the rocket mode, and try to point nose up as much as possible to build enough vertical momentum to get you into orbit without losing that horizontal momentum and coming crashing to the ground. Bearing in mind that it is extremely difficult to maneuver a vehicle like that under such high aerodynamic stress. It's a very difficult needle to thread.

And it would be much more difficult in Earths atmosphere actually, KSP makes kind of goes easy on your and gives the home planet a weaker atmosphere and weaker gravity than Earth. LEO on KSP takes a speed of about 3500 m/s to get into, whereas on Earth it takes about 7000-8000 m/s. That extra 4000 is a bitch to get. The game became orders of magnitude more difficult when I installed a mod that gave the home planet similiar parameters as Earth.
 
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