Pros and Cons of Engine Clustering

[pjamas]

Hi, I've just started up a new career, and without having the 2.5m engines unlocked yet, but the 2.5m tanks, I was wondering about the efficency and effectice was of clustering engines, any input? Edited November 22, 2015 by pjamas

[Gaarst]

More engines means more thrust so shorter burns.
But more engine also means more mass so less dV.

If money and rocket size is not a problem, then I would go for engine clusters as it is more practical (also allows to make nice designs). On the other hand, if your craft has to be as small/cheap as possible, then use a single engine.
Of course, keep in mind that you need a TWR of at least 1.2-1.3 for a good ascent stage, if one engine gives you a TWR of 0.5, you're not going anywhere.

[Taki117]

It's a tad outdated, but here's a calculator for engine clustering.

[url]http://blizzy.de/asparagus/[/url]

[ElWanderer]

Clustered engines can work out cheaper (three Reliants cost 3300 compared to 5300 for a Skipper, though you may need to pay for adaptors. Their thrust is similar, though the Reliants have an edge at sea-level) at the cost of being more massive (3.75t plus adaptor versus 3t). For an expendable first stage this is an acceptable trade. Upper stages, you generally want to keep as light as possible.

Clustering is also helpful if, say, you want more thrust than one Reliant but less than a Skipper - why not take two Reliants? Pity most of the adaptors are way up the tech tree.

[Snark]

Also, when you say "clustering", bear in mind that it matters [I]how[/I] you cluster. Aerodynamics are important, make sure you're building something that can get through the atmosphere without wasting too much fuel fighting drag.

It's not such an issue if you've got an appropriate adapter, but the 2.5m-to-multiple-1.25m adapters are way up at the top of the tech tree. If you're attaching the engines radially, make sure you have appropriate nosecones, and (if you have them unlocked) use fuel lines appropriately so you can asparagus them.