[AR] Re: SpaceX F9 Launch/Update -- Live Link
- From: Alexander Ponomarenko <contact@xxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Wed, 30 Dec 2015 01:14:49 +0100
On 12/29/2015 09:40 PM, David Weinshenker wrote:
No, there's nothing "magic" about gas generator cycles - they're a
simple, effective solution. There's something a bit "demonic" about
staged combustion cycles (from the engine development point of view),
though; it's much harder to develop such an engine incrementally: you
sort of have to get everything working at once in order to test-run
anything.
Well, SC can be developed and tested incrementally. For example, that is
why RD-170 has a lot of flange joints (even more than later RD-171M and
RD-180).
Beside that, SC is not necessarily about (extremely) high chamber
pressure like in engines of RD-170 family. It can be moderate (like in
RD-253 or NK-33), or even relatively low and comparable with chamber
pressure in GG engines (like in BE-4). This makes the design as well as
development easier.
Actually, the development of SC with moderate or low chamber pressure
based on state of the art knowledge about chemical propulsion can be
even easier than development of GG. Especially if you want to use LH2 or
liquid CH4, and especially if you already have previous experience with SC.
I heard that a number of SSME prototypes were consumed in the
process of discovering a safe startup sequence... it wouldn't
surprise me if there were similar experiences "over there",
during the initial development of the RD-180.
Indeed, the development of RD-170 was *very* difficult, with a lot of
consumed prototypes.
But development of RD-180 was fast and smooth because of previous
experience and similar design.
BR,
Alexander
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