Why aerospikes?

[CalculusWarrior]

I've heard of the amazing powers aerospike engines had in versions prior to 0.18, but then they were nerfed and I can't seem to find a use for them on my ships. They have generally high efficiency, but I've always found that they have too little thrust to put them on my main ship, and they're too heavy for me to want to use them on landers.

About the only applicaton I can think of is for spaceplanes, but other than that I'm stumped.

Am I missing a crucial application of aerospike engines? Can I somehow make my rockets super efficient and powerful?

[rryy]

They are useful for taking odd from Eve, and may be useful for a first stage engine at takeoff, but an LV-T30 can probably do as well or even better than the aerospike. They can really only outmatch the LV-T30 when you need to use a rocket at low altitudes for long periods of time.

Edited April 22, 2013 by rryy

[ThatBum]

I do think they're intended for spaceplanes, once the air-breathing engines die out.

Some real-life info on them.

[Francesco]

there is a niche for them (Eve return crafts, as suggested) - but if you're looking for maximum efficiency, usually the LV-T30 wins.

so I don't think you're missing anything here

[AmpsterMan]

I only ever use them on spaceplanes too. I like how they look much better

[SalmonellaDingDong]

I've never used them. I always see people using them on planes, however.

[Qumefox]

I personally think they were nerfed a bit too hard myself. Yes they were OP before, but for most part, they aren't even an option now for the vast majority of builds.

[Mastodon]

only time I have used them is for my SSTO, as you can see below (center engine). but I honestly only used it because of its compact size and because that seemed to be what everyone else used. never tried any other rocket. maybe I should do some testing some day...

[loppnessmonsta]

I use them on my main lifter designs. I take a big orange fuel tank, slap a Mainsail on the bottom, then use the new girder parts (The really wide I-beams seem to have just the right height to work without part clipping) to attach 8 aerodynamic tails. From there I add a small fuel tank and an aerospike on each, then add struts and fuel lines.

Since this is all on the center tank, and I use asparagus staging for almost everything, they're burning the entire way up. And that makes fuel efficiently more important than usual. Since the mainsail has thrust vectoring, and the aerospikes don't it made it a pretty powerful mix, since you don't want TOO much vectoring, but not too little, either. Combined with a set of aerodynamic control surfaces at the front of the rocket, it makes it fairly easy to control.

If I wanted raw power the whole way up, I suppose I could use the T30s, but I have plenty of room for brute power on the outer tanks, which burn at a lower altitude, where brute power matters more.

[Deadpangod3]

I love aero spikes, aero spikes are what delivered my first rover to the mun

[Temstar]

Aerospikes are pretty bad for spaceplanes too, with the possible exception of the few and far in between "pure rocket" SSTOs. Most SSTOs these days can climb to 20km+ on their jets, by which point the air is so thin rocket engine Isp are pretty much their vacIsp anyway so aerospike's high atmIsp is no advantage. That said, if we compare aerospike to three LV-909s for vacuum operation, we get same weight, same Isp, same low profile but 25kN more thrust. So in the rare event that you're building some kind of huge Mun lander that need three LV-909 engines (or a poodle), consider replacing them with an aerospike and launch the lander upside down on the top of the rocket instead.

That and Eve return vehicles, not only because aerospike can get 388s inside that 5atm atmosphere, but also because the engine is a 0.2 low drag part. Only downside is that it's low drag moves your centre of drag up, which makes the rockets a lot harder to control.

[CalculusWarrior]

I'm a long way off from attempting an Eve return mission, but thanks for the tips!

[cardgame]

Even for spaceplanes I don't see the point of using an aerospike over the LV-909. Since it weighs so much less, it doesn't upset the balancing act that is spaceplane building and operation, and 175 thrust isn't really needed in my experience.

[ThatBum]

They're a lot shorter than the T-30s/45s. I guess that's a benefit if you use it on a spaceplane, so when you're taking off it doesn't smack the engine into the ground.

[Brotoro]

A disadvantage of the aerospike is that it is not a thrust-vectoring motor.

[opticalshadow]

unless your leaving eve, there is no point to the aerospike, it got nerfed beyond use.

[bsalis]

The higher ISP over the other chemical LT engines more than overcomes the slightly heavier weight. I did some math after the nerf to find out.

[tomf]

a cluster of 4 spikes with 27 tones of fuel and tank on top is a very effective asparagus stage. e.g.

Central rocket weighing 70t lifted by a mainsail

6*4 spike clusters with 27 fuel each gives almost the same dv as 6*4 lv-30 clusters with 36 t each, but weighs 50t less on the launchpad

[RoboRay]

The primary advantage of aerospikes is that they are equally efficient in atmosphere as in space. So, the place to use them is where a craft will be operating in both environments. Spaceplanes, yes. Vertical SSTOs, yes. Even long-burning boosters for launches from Kerbin, Laythe or Eve, are all good applications for aerospikes. They have a narrow niche where they are the superior choice, but it does exist.

[Matrix Aran]

I've used them for my Laythe landers as ascent engines, the extra ISP in an atmosphere is always welcome, the fact they perform well in orbit makes them equally useful for the earlier de-orbit burns. Also, though not really a performance consideration, I love these things for their low profile. Compared to most other engines they're rather small and compact which makes it easier to design a nice stable set of landing legs without having to worry about engine clearances.

As others have said, these are really a niche set of engines, rather than a workhorse engine. They still have their uses for those who can find them, and if you don't want to use them there are of course alternatives.