Damon Hill wrote:
I'm rather more curious about the PWR35M engine to be flown on
an upgraded version. Apparently a modified RL10 running on
methane; PW has run tests with methane before but this would be
the first actual flight application. Why methane instead of
hydrogen? Lower Isp, still cryogenic, possible sooting issues?
Not even sure if its a turbopump or pressure fed design; no
real details available on PWR's site.

There's a discussion of its advantages he
http://www.daviddarling.info/encyclo...et_engine.html

But you are taking a mighty big hit in the isp department to use it
rather than LH2.


It will be cool to see the NK-33/AJ-26 finally flying again.
Accounts vary as to what versions of this engine actually
flew on the N-1; apparently the original design was almost
completely redone in the course of the N-1's travails.
This time I hope it vindicates the original designers,

It's surprising that the Kuznetsov design bureau could come up with
something that innovative on their first crack at a rocket engine (they
are a jet engine design bureau).

but given its past history with N-1 and the never-flown Kistler
K-1 it's not hard to imagine a curse having been laid on the
thing, eh?

At least as far as the N-1 went, the problem with it wasn't the engine
itself, it was the plumbing that fed the propellants to the engine and
the foriegn object the one engine ingested on the second launch attepmt.

(Rocket geekery: there's a duct going down the side of the NK-33's
exhaust nozzle that looks all the world like a turbopump
exhaust, but this is a closed-cycle staged combustion design.
It doesn't appear to manifold into the nozzle, and some pictures
seem to indicate the duct has no opening.)

According to this:
http://gravityloss.wordpress.com/2009/10/03/nk-33/
That's the "starter".
I assume it's a solid-fuel gas generator that spins up the turbopump
before it starts running on its own.
Something similar was used on the Titan II's first stage engine, and
made the odd shreiking sound that everyone noticed at engine ignition
during a Gemini launch.
Use of solid-fuel gas cartridges was one way to spin up a turbojet
engine on starting*, and I assume the design bureau just modified the
concept for rocket engine starting.

--Damon, who never met a rocket engine he didn't like

Lookie what I just found:
http://www.ninfinger.org/models/tita.../tii_dwgs.html
All sorts of detail drawings of Titan II engines.

* Let's cartridge start the Canberra bomber, shall we?:
http://www.youtube.com/watch?v=CiXxCgjyKeI

Pat