SpaceX Falcon I Launch III - Build-up Thread

[nobodyofconsequence]

What typically defines the number of engines? 

Turbo machinery and not the nozzles

Does this mean that if VAPAK powered AirLaunch LLC's QuickReach makes it to orbit, it will have done so with NO engines?  Look, ma, no turbo's!

[guru]

I don't believe we will see anything new about Merlin 2 for a while let.
Unless, several significant failures occur with Falcon 9's engine bay (or thrust structure) then we might see some new engine development, or Elon will just exit the business.

But down the road if the heavy has problems with 27 engines(if it fly's), or a very unlikely major change in the market for 30+ tons to LEO, we could see a new core stage for 1-4 Merlin 2's.

The quote is actually a couple of years old, so, yeah, he already missed that deadline.  I posted the quote in context to show his definition of what an "engine" is, not to try and get anyone excited over an engine that he probably wouldn't build for a few years, if at all (though, I hope he eventually does). 

[William Barton]

You could plausibly make the argument that because the fuel was cross-fed, the Saturn 1 has one engine with eight nozzles and eight sets of turbomachinery.

No you can't, they are 8 independent engines.  Crossfeeding is a function of have multiple tanks and not multiple engines.  It means that the engines could draw propellants from the various tanks.  It doesn't mean a turbopump from another engine is feeding a different thrust camber.  Crossfeeding WRT to a Delta IV heavy means the core engine can be fed by a strapon tank. 

Turbomachinery does define the rocket engine because a nozzle/thrust chamber (of the engine) can't operate by itself.

triva - Atlas I & II only had two engines in the first stage.  The two  thrust chambers in the booster package were power by one turbopump

Well, by that standard, turbomachinery can't accomplish much by itself either. Take away the nozzle and you've got the burner basket for a modern aerostat. Take away the burner itself and what's left is the basis for a nice fire engine.

If you had six turbopump assemblies feeding four nozzles, how many engines do you have? (I realize that's ridiculous, it's just for the sake of the question.)

I did know about the Atlas, but only because you told me a few months ago. I've learned a lot here.

[William Barton]

Turbomachinery does define the rocket engine because a nozzle/thrust chamber (of the engine) can't operate by itself.

Not to be a devil's advocate, but I would like to point out pressure-fed engines do just fine.   That being said I know what you're trying to get at, and I agree (to a point). 

I actually think guru said it best... depends on what subject you're talking about.  If it's external consideration (pressures, plume interaction, combustion instability, etc), nozzles is the important number, but if its internal consideration (systems, etc inside the rocket) then one looks more at the turbomachinery count since it is much more complicated than other bits (and bobbles).

triva - Atlas I & II only had two engines in the first stage.  The two  thrust chambers in the booster package were power by one turbopump

Wow! I wasn't aware of that... how'd they do the plumbing?

This whole business of what is an engine (turbomachinery vs. nozzles) is a bit of nomenclatural flim-flam. So is the distinction between a liquid-fuel "engine" vs. a solid-fuel "motor."

I love that debate....

"How do you insult a Solid Rocket Designer?  You say 'Did you design this rocket engine?'  "
"How do you insult a Liquid Rocket Designer?  Tell him 'Nice Motor!'  "

Didn't the final design for Rotary Rocket have a spinning engine that used centrifugal force to pump the fuel? If there was no turbomachinery and Finagle knows how many nozzles... maybe you could define such an engine on the basis of the thrust bearing?

Wasn't there a prototype German bomber in WW2 that had four engines driving two props? And the Wright Flyer had one engine driving two props...

[antonioe]

"See the little phrases go,
watch their funny antics;
the men that make them wiggle so
are teachers of Semantics"

Frederick Winsor, "The Space Childīs Mother Goose"

[toddbronco2]

"See the little phrases go,
watch their funny antics;
the men that make them wiggle so
are teachers of Semantics"

Frederick Winsor, "The Space Childīs Mother Goose"

I was serious when I originally asked "what typically defines the # of engines."  I think its interesting that there's so much variety of opinion in such a straight forward question

[Patchouli]

I can see reasons for merlin II on falcon 9 other then reliability issues with the 27 merlin 1Cs.
The main reason would be cost reductions on later vehicles as well as getting more payload by reducing the mass of the plumbing and electrical wiring.
I think we'll see merlin II on unmanned versions of falcon 9 before we see it on manned vehicles as the 9 engines per core on F9 is considered a safety feature.

But he does seem very interested in eventually replicating the capability of the old Saturn V vehicles potential markets for such a large vehicle might be launching private space stations, lunar tourism, and supplying NASA and the ESA with a second HLLV.

Maybe a back up plan to Ares V if funding can't be found for it and history has shown it's always good to have a plan B.
Plus a few uses we haven't thought up yet might materialize if a 70 to 100ton class vehicle esp one that may cost the same as a heavy EELV was available.

[antonioe]

I was serious when I originally asked "what typically defines the # of engines."  I think its interesting that there's so much variety of opinion in such a straight forward question

I wasnīt making fun of the question, only of some of the answers...

Let me propose this: the smallest unit that can be started (and possibly stopped) independently, from a purely propulsive standpoint (althought it may tip the rocket if you do so).

Under this definition, the R-7 had five engines.  Saturn V Stage 1 also had five.  Zenit Stage 1 has one engine.

[dunderwood]

Let me propose this: the smallest unit that can be started (and possibly stopped) independently, from a purely propulsive standpoint (althought it may tip the rocket if you do so).

You might have to add exceptions for launch abort systems and RCS thrusters to that definition.  (Unless that's already implied in the 'propulsive standpoint' note.)

[Patchouli]

I'm going to go with 5 turbo-pump fed engines since that is the official count.  But, looking at it slightly differently for a moment - a pressure fed rocket engine is an injector, an ignition mechanism (that also includes chemical mechanisms as in hypergolic), a combustion chamber, a throat, and a nozzle, and maybe some cooling system if you're really fancy.  If you really wanted to push it, you could say that the Soyuz has 20 liquid fueled rocket engines that use pressure provided by five turbopumps.  But, in that case, every liquid chemical rocket engine would be called pressure fed.  Example: the X-33 aerospike had multiple burner assemblies, but since they were attached to two ramp assemblies and used two sets of turbopumps, we say the X-33 would have used two engines.  Likewise, we say the Soyuz has five engines.

On another note, the only vehicle that has ever launched with a comparable number of first stage engines to the Falcon 9 H (27 engines) is the Soviet N-1 (30 engines), which failed on four out of four flights.   I believe the biggest difference between the two vehicles is modern sensors and controls.  Computers can sense and act on redlines in just milliseconds, greatly increasing the usefulness and success rate of the engine-out capability in comparison to early 1970's Russian technology.  In the long run, though, I believe it would be wise for SpaceX to build the bigger 1.2 million lbf engine and add cross feeds to the propellant tanks.

Well more then that the N1 had combined cycle engines while the F9 uses low pressure open cycle engines that operate at only 60 Bar.
The N1 blowing up had more to do with the fact oxygen rich combined cycle engines are a PITA to keep from exploding then the fact it had 30 engines.

The NK series engines  such as the NK33 ran at over 145Bar twice the pressure the F1 ran at and real time controls at the time just were not up to the task of making hundreds of tiny corrections every second.
The Soviets were literally trying to operate an engine that was closer to something developed during the 80s using 1960s computer technology.
I once read story where a Russian engineer talked about the development of the RD170 and how a chamber would melt like wax during a failure because they are running so close to the limits of the materials while open cycle engines they would just split open crack etc but not completely self destruct.

The closest vehicle one can compare Falcon-9 with would be the Saturn IB and F-9H would be like a three core version of the IB.

[nacnud]

Let me propose this: the smallest unit that can be started (and possibly stopped) independently, from a purely propulsive standpoint (althought it may tip the rocket if you do so).

That is what I was thinking, it seems reasonable but I bet there is an exception out there somewhere

[hop]

Well more then that the N1 had combined cycle engines while the F9 uses low pressure open cycle engines that operate at only 60 Bar.
The N1 blowing up had more to do with the fact oxygen rich combined cycle engines are a PITA to keep from exploding then the fact it had 30 engines.

I don't see any evidence that was the case. The root causes seemed to be a programmatic issues: rushed schedule, poor quality control, insufficient testing.

[Patchouli]

Well more then that the N1 had combined cycle engines while the F9 uses low pressure open cycle engines that operate at only 60 Bar.
The N1 blowing up had more to do with the fact oxygen rich combined cycle engines are a PITA to keep from exploding then the fact it had 30 engines.

I don't see any evidence that was the case. The root causes seemed to be a programmatic issues: rushed schedule, poor quality control, insufficient testing.

Those were contributing factors esp the lack of a test stand for the N1 first stage.
But one failure I read that happened often would be an engine would explode and then take out it's neighbor and cause a chain reaction.
Faster realtime controls might have shut down the offending engine before it explodes.
Though ground testing the whole first stage or at least the entire first stage engine assembly and thrust structure would have uncovered that failure mode.

[stockman]

do we need an N1 thread to continue this discussion? Any chance the thread can get back on topic of the next falcon launch?

[Patchouli]

Someone just was comparing F9 to the N1 but I think spacex did the right thing delaying the third F1 flight because of the weld defect vs risking that the weld might fail.
They need a success vs another failure they can learn from.

[nobodyofconsequence]

Well more then that the N1 had combined cycle engines while the F9 uses low pressure open cycle engines that operate at only 60 Bar.
The N1 blowing up had more to do with the fact oxygen rich combined cycle engines are a PITA to keep from exploding then the fact it had 30 engines.

I don't see any evidence that was the case. The root causes seemed to be a programmatic issues: rushed schedule, poor quality control, insufficient testing.

Those were contributing factors esp the lack of a test stand for the N1 first stage.
But one failure I read that happened often would be an engine would explode and then take out it's neighbor and cause a chain reaction.
Faster realtime controls might have shut down the offending engine before it explodes.
Though ground testing the whole first stage or at least the entire first stage engine assembly and thrust structure would have uncovered that failure mode.

At the risk of continuing OT - what you're referring to was Korolev's simplistic approach to flight dynamics control with a engine shutdown mechanism that attempted to correct for off axis thrust imbalance by shutting down engines.

N1 is a bad analogy for any other LV including F9. A one of a kind for a time that shouldn't have been and will never come again. Too bad, because it sullied the reputation of damn good engines NK 33/43. And yes they have impressive operating characteristics. Should be interesting what OSC gets them to do.

[Patchouli]

I wish we could have gotten to see what Kistler could have made them do also off topic but I wonder if the first stage on OSC's Taurus II could be reusable like the Falcon rockets?
BTW does anyone have specs on the number of reuses the Merlin 1C is supposed to be good for before requiring refurbishment?

I think that last question is back on topic well at least back to talking about Falcon.

[A_M_Swallow]

But down the road if the heavy has problems with 27 engines(if it fly's), or a very unlikely major change in the market for 30+ tons to LEO, we could see a new core stage for 1-4 Merlin 2's.

30+ tons to LEO.  Sounds like the Ares 1-zz lifting the Orion.

[Antares]

1) I do not believe a pressure-fed liquid 'thing' like VAPAK or AJ-10 is an engine.  It is a motor, like a solid.  There is no energy transfer going on internally.

2) how about this definition: the number of pairs of fuel and oxidizer inlets.... because consider that an SSME has FOUR turbopumps.  Definitely not 12 engines on an orbiter.

3) Recall that SpaceX's VP of Propulsion was one of the main designers of a 1.07M lbf engine that got close but never went into production.  Methinks he's out to realize his dream.  Dang, that sounds like fun.  Where's my resume?

I think we'll need a new thread when F1.3 finds a dependable range date.

[Jim]

I wish we could have gotten to see what Kistler could have made them do also off topic but I wonder if the first stage on OSC's Taurus II could be reusable like the Falcon rockets?

No, because it would reduce payload to orbit.  Also Spacex has yet to prove reuseability