SpaceX Falcon I Launch III - Build-up Thread

[toddbronco2]

Too quiet, Elon spoke at the royal aeronautical society, nothing informative about Flight 3.
http://www.flightglobal.com/blogs/hyperbola/2008/07/audio-spacex-ceo-elon-musk-spe.html
http://www.flightglobal.com/blogs/hyperbola/2008/07/musk-80-million-to-go-to-the-m.html

I'm guessing they're very tight lipped right now.

Someone should mention to Elon that the Soyuz booster has only 5 engines, not nearly 27...

Only 5 engines? Is that right?  I grant that each core of the Soyuz doesn't have 9 engines, but I thought it had 4 apiece on each of 5 cores for a total of 20 engines.  Musk's assertion doesn't sound that silly then. 

[Skyrocket]

Only 5 engines? Is that right?  I grant that each core of the Soyuz doesn't have 9 engines, but I thought it had 4 apiece on each of 5 cores for a total of 20 engines.  Musk's assertion doesn't sound that silly then. 

This is a general misconception: Do not equate the number of nozzles with the number of engines. The Soyuz has indeed only five engines during launch, each with four main chambers and two (on the strap ons) or four (core) vernier nozzles.

See following link for a diagram of the RD-107 engine:
http://www.lpre.de/energomash/RD-107/img/flow_diagram.jpg

[nobodyofconsequence]

Too quiet, Elon spoke at the royal aeronautical society, nothing informative about Flight 3.
http://www.flightglobal.com/blogs/hyperbola/2008/07/audio-spacex-ceo-elon-musk-spe.html
http://www.flightglobal.com/blogs/hyperbola/2008/07/musk-80-million-to-go-to-the-m.html

I'm guessing they're very tight lipped right now.

They are attempting to look professional right now and let the past be forgotten. They will launch when they are ready for it. Don't expect any chatter as it only serves to add chaos.

Don't know about anyone else, but think that's exactly what they should be doing. We all know pretty much what needs to happen.

[josh_simonson]

So basically it's like five 4 (6-8?) cylinder engines vs nine 1 cylinder engines.

I like that bit about the kestrel not counting since it has no pump.

[jabe]

In the article to which jabe provided a link, there was mention of another, larger article to come.
"Coming up in July NBC 6 News will have a special report on the local research being done by Space-X for future space travel. "
"July" doesn't limit them much.
You are not "losing it", at least not yet.  You still have time. :-P Don't get me started on "old".

I'm glad that someone knew what i was talking about.  Spent a few days trying to find the text I was looking for with no luck.. I'm not passing it off as being old ..at least not yet
I hope it is a good article "coming in july".  I hope Spacex plays it quiet until a week or so before launch...but they better not launch when I'm on vaction camping...there is something about watching a launch live.
I wish them luck..
jb

[toddbronco2]

Only 5 engines? Is that right?  I grant that each core of the Soyuz doesn't have 9 engines, but I thought it had 4 apiece on each of 5 cores for a total of 20 engines.  Musk's assertion doesn't sound that silly then. 

This is a general misconception: Do not equate the number of nozzles with the number of engines. The Soyuz has indeed only five engines during launch, each with four main chambers and two (on the strap ons) or four (core) vernier nozzles.

See following link for a diagram of the RD-107 engine:
http://www.lpre.de/energomash/RD-107/img/flow_diagram.jpg

What typically defines the number of engines?  (not sarcastic, I'm serious)  Is the # of engines defined by the number of turbo pumps or what?  I would have counted nozzles cuz I figured that the gas expanding out of those nozzles provided the thrust and that was more significant than the plumbing.  Is it just the fact that four nozzles are fabricated together in one inseparable assembly that it counts as one engine?  I'd appreciate some clarification.  Somehow I get the feeling Elon Musk may have encountered the same confusion when he was referring to all of the engines on the Soyuz.

[Avron]

Ok.. I wonder if it not time for a little inquiry... Chris? you have the connections...

[Jim]

What typically defines the number of engines? 

Turbo machinery and not the nozzles

[Swatch]

"Design of non-pressure-fed Rocket engines is 90% turbomachinery and 10% other bits and bobbles..."

~one of my professors...

That's why they don't count the nozzles.

[NotGncDude]

I haven't listened to Elon's talk so I can't be sure, but if he was talking in the context of the gas dynamics of the 9 (or 27) Falcon 9 engines firing together then it would make sense to bring up Soyuz 20-something chambers. If he was talking in the context of reliability or complexity then it makes more sense to focus on the turbomachinery.

[Antares]

In the end, the two most important numbers on engines are cost and reliability, not thrust and Isp.  If they were free and perfect, it wouldn't matter how many were on there.  Turbomachinery is worse than combustion devices in both cost and reliability.  More expensive to develop and build.  More things to go wrong.

[Danderman]

What typically defines the number of engines? 

Car engines may have multiple cylinders, and so no one claims that a V-8 is an 8 engine car.

[guru]

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.

[kevin-rf]

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.

I would argue from a performance stand point it would be wiser to use a single BF tank set vs. the the three tanks sets and fancy cross feed of the falcon heavy (or any other all liquid heavy for that matter).

[William Barton]

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."

The analogy with reciprocating IC engines is essentially useless. You could design an engine with multiple fuel pumps and one cylinder, if you thought of a reason to bother. The unifying item in most autombile engines is the crank shaft, but it doesn't have to be. Just as there are duel-cam engines, there could be dual-shaft engines, and it would still be refered to as one engine. That's because the clasical definition of "engine" is, an assemblage of machinery that does work. That's why catapults are classed as "seige engines." 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.

Same thing with motor vs. engine. All we're seeing is traditional usage here, not intrinsic meaning. A motor is something that imparts motion. That's why they're sometimes called motorcars.

[Jim]

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

[Swatch]

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!'  "

[Danderman]

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

AFAIK, there were a few variants of the original Atlas where the two main engines in fact were plumbed with a single turbo pump. I am unaware of Atlas II with that modification.

[guru]

I haven't listened to Elon's talk so I can't be sure, but if he was talking in the context of the gas dynamics of the 9 (or 27) Falcon 9 engines firing together then it would make sense to bring up Soyuz 20-something chambers. If he was talking in the context of reliability or complexity then it makes more sense to focus on the turbomachinery.

I just found this quote from Elon Musk:

'No comment on Merlin 2 yet. We will be releasing a spec to the public in a few months. All we can say at this point is that it will be the world's largest engine, where engine is defined as a single thrust chamber (the only logical definition in my view). The Saturn F-1 was larger, but obviously is no longer in production.' (http://www.nasaspaceflight.com/content/?cid=4254)

This explains why he said 20 engines.

[Chris-A]

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.