18

It seems to me you've got two questions: 1) Why can open-expander-cycle engines be larger than closed-? and 2) Why aren't there more expander-cycle sea level engines? Your question[s] shows you are already aware of the scalability problems that haunt expander engine designers. Before we can look at where such problems originate, let's talk a bit more about ...


11

It's the turbopump exhaust from the booster (jettisonable) engines. From Spacecraft and Boosters by Gatland p. 222-224 Exhaust stack discharges fuel-rich efflux outside reverse aerodynamic flow at base of missile In other words, the main purpose of the long duct is to get the fuel-rich turbopump exhaust away from the bottom of the vehicle to prevent ...


6

The RL10 is a terribly expensive engine to produce (I've seen estimates of US$25 million per unit), mainly due to its welded-tube nozzle construction. I expect Vinci will be substantially cheaper to produce on a one-for-one basis, let alone two-for-one. Furthermore, export of RL10s is restricted by US law, though I imagine the ESA could get a waiver if the ...


6

The baffles on the F-1 and other engines such as early versions of the SSME (described here) are intended to prevent the occurrence of high-frequency combustion instability in the engine's combustion chamber. Uncontrolled combustion instability can destroy an engine due to excessive vibration force (which may break engine parts) or excessive heat ...


5

TWR was sacrificed for specific impulse in later engines? The NK-33 had a sea-level specific impulse of 297s; the RD engines mentioned above vary from 309s to 311s. My intuition from playing Kerbal Space Program is that this is an unfavorable tradeoff for first-stage engines... In the RD-170 case it's almost exactly an even performance tradeoff; propellant ...


2

It's a decent approximation. The effect of convective heat transfer on the flow is very slight in practical nozzles, since its influence extends only so far as the thermal boundary layer thickness, and this is of the order of the velocity boundary thickness (for typical gases). Radiant heat transfer is also of little importance to propellant ...


2

First, clustering of engines saves a lot of engineering work. You only design one engine, rather than more than one. This is especially valuable in the extremely conservative world of man-rated aerospace. It boils down to modularity. Second, if you're cost-sensitive, and you're trying to mass produce a ship, clustering lets you mass-produce engines. For ...


Only top voted, non community-wiki answers of a minimum length are eligible