Rocket Engine Q&A

[Robotbeat]

Yeah, took some pictures once of some Mach diamonds from the tip of an air compressor nozzle. Any time you get a sizable pressure drop, you pretty much get Mach diamonds. Unless you’re trying not to.

[JetProp]

I'm looking for article LEMAITRE, A. ─ MARCIQUET, C.: Propellant Electric Pump for low thrust cryogenic propulsive systems. 4th European Conference for Aerospace Sciences (EUCASS), Saint Petersburg, Russia, 2011
Sometime the article was available on the site: http://eucass2011.conferencecenter.ru/cs/upload/gF76bMq/papers/papers/978-1505-1-RV.pdf
but this site is dead.
Please, help find this article...

Sorry my bad English.

[gin455res]

If one had a 1.3m diameter rocket nozzle and combustion chamber but could not 3d print it because it was too big, but could 3d print 4-5  60-65cm diameter nozzles and combustion chambers and connect them together as a multi-chambered engine; which engine would have fewer parts, and which would be cheaper to build?
 
i.e. Does 3d-printing favour/afford multiple chamber rocket engines?

[Proponent]

Though I can't say much about 3-D printing, it's certainly possible to build multi-chamber engines.  That's what the famed RD-107/108 is, not to mention the RD-180, which, in turn, is just half of an RD-170.

To a first approximation, a nozzle is a pressure vessel, so its mass scales as the product of pressure and volume.  For a constant nozzle shape and chamber pressure, then, the thrust-to-weight ratio would actually tend to improve with increasing numbers of smaller nozzles.  And the nozzles will be shorter than a single monolithic nozzle.

On the other hand, while the "good" things about rocket plumbing -- flow rates and cooling requirements -- tend to improve with increasing cross-sectional area, the "bad" things -- viscous losses and leakage -- tend to scale with diameter, i.e., more slowly with increasing size.