Question: The question [Astronomical ABCD…!](https://astronomy.stackexchange.com/q/23563/7982) suggests a corollary for SXSE.

I'm looking for one example of a rocket with $n$ first-stage engines, for each $n$ for which you can think of an example for. It should be at least built, or very seriously proposed and investigated at a minimum.

I'll start off with some suggestions, items of recent popularity to get the ball rolling, but you don't have to use them.

* **1** - [Falcon-1](https://en.wikipedia.org/wiki/Falcon_1)
* **9** - [Falcon-9](https://en.wikipedia.org/wiki/Falcon_9)

Let's first try without jumping immediately to vehicles with variable strap-on number options, and see how that goes?

Answer: 
British, very seriously proposed and investigated (and the Black Arrow orbited a satellite after it was cancelled): $$\begin{array} {r l}
\text{Black Arrow}^1 & \text{1 engine with 8 combustion chambers} \\
\text{Europa}^2 & \text{2 rocket engines} \\
\text{MUSTARD}^3 & \text{3 engines (one in each of the triamese craft)} \\
\text{Interim Hotol}^4 & \text{4 engines} \\
\text{Skylon D1}^5 & \text{6 engines with 12 combustion chambers/nozzles.}^\* \\
\hline
\text{The BIS Space Ship (1939)}^6 & \text{168 solid motors}^{\*\*}
\end{array}$$

\* two engines per nacelle, two SOMA engines in the tail. All running during the latter parts of the ascent.

\*\* OK, perhaps not *so* seriously

1. <https://en.wikipedia.org/wiki/Black_Arrow>
2. <https://en.wikipedia.org/wiki/Europa_(rocket)>
3. umm...
4. err...
5. <https://web.archive.org/web/20160328220308/http://www.reactionengines.co.uk/tech_docs/SKYLON_Users_Manual_Rev_2.1.pdf>
6. <http://www.bis-space.com/what-we-do/projects/bis-lunar-spaceship>
* 5: [Saturn V](https://en.wikipedia.org/wiki/Saturn_V), first and second stages.
* 8: [Saturn I](https://en.wikipedia.org/wiki/Saturn_I), first stage.