SpaceX Merlin 1C Engine

[Jim]

aero313 - 21/3/2008  11:39 AM

Comga - 20/3/2008  11:47 PM

Crispy - 20/3/2008  1:01 PM
 The only common factor (of the F9 second stage) with Falcon 1 is probably the avionics.

And using the turbopump exhaust for roll control
I have not seen confirmation that each F9 engine has two axis control.  
It looks like the Saturn 1B used single axis steering on each of its eight engines. Can anyone confirm or refute this?

You only need single axis steering.  So long as the hinge axis is on a radial line from the center of the stage, four single-axis gimbals provide both attitude and roll control.  This is how the Minuteman first stage works.  The problem is that without two-axis gimbals on all the engines, I don't thing you have true engine-out capability for all failure modes.

there was talk of shutting down corner engines to limit g loads, this would play to the gimbaling scheme

[Jim]

Comga - 20/3/2008  11:47 PM

It looks like the Saturn 1B used single axis steering on each of its eight engines. Can anyone confirm or refute this?

inner four were fixed and the outer four had 2 axis steering

[meiza]

Musk's still gotta work on showing that big smile when a camera shows up, like the old PR pros.

[William Barton]

daver - 21/3/2008  12:06 PM

Elon Musk and Richard Branson to save the world....or get rich trying.
http://www.iht.com/articles/2008/03/20/business/deal.php

Musk appears to be contemplating the placement of Blair's feet, as in, "Do I tell him what he's just stepped in, or not?"

[William Barton]

Jim - 21/3/2008  12:25 PM

Comga - 20/3/2008  11:47 PM

It looks like the Saturn 1B used single axis steering on each of its eight engines. Can anyone confirm or refute this?

inner four were fixed and the outer four had 2 axis steering

I'm sure you're right, but when you look at the business end of a Saturn I, it looks like the four outer engines have single axis steering oriented in two directions (opposite corners parallel). I don't actually know what I'm seeing, so it's just an impression from the shape of the openings through which the outer four protrude. Would an arrangement like that be considered 2-axis? (Your comments may be terse, but I always seem to learn something.)

[Jim]

William Barton - 21/3/2008  1:03 PM

(Your comments may be terse, but I always seem to learn something.)

just efficient comments, minimal keystrokes.

[Big Al]

I just found a nice 280 page PDF file from the NASA server about the structure and systems for Saturn 1 and 5. The fuel and lox manifolding for the Saturn 1 was indeed complex, no so much for the 5 with a single lox and fuel tank on the first stage. It will be interesting to see how Spacex designs their fuel and Lox feed for the Falcon 9

I also noticed in the section on the H1 that it used a solid fuel start cartrige to get the turbo pump to spin up, what does the Merlin use?

[pippin]

Jim - 21/3/2008  6:25 PM

Comga - 20/3/2008  11:47 PM

It looks like the Saturn 1B used single axis steering on each of its eight engines. Can anyone confirm or refute this?

inner four were fixed and the outer four had 2 axis steering

Are you sure? I thought they had singe axis tangential steering on the outer 4?

[Big Al]

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19710065502_1971065502.pdf
This file is called "Apollo Systems Descriptions" , has everything you ever wanted to know about Saturn. In there they say that the Saturn 1 first stage outer engines can move in an 8 degree square in both pitch and yaw ( suprised me, I thought like pippin that they would have single axis steering only)

[pippin]

Maybe the control authority would have been to difficult for the electronics back then when you lose one of the outer engines. Theoretically you should have enough roll control through the two paired engines to compensate for the roll you induce when pitching/yawing with only one engine but that would be a completely different animal from the "normal" steering.

Thanks for the link :-)

[Big Al]

Which only adds to the mystery of how many of the first stage engines on the Falcon 9 will be gimbaled and will they gimbal in pitch and yaw both?

[Chris-A]

In sort: what was provided then, may be out of date now.

On the space show, Gwynne said all nine engines gimbaled, but was unsure. For the feed lines the pictures show some detail, if you look hard.

[Big Al]

That makes sense, with the close spacing of the engines and the thrust struts look like their the same as a Falcon 1.

[CFE]

On the Falcon IX upper stage, does SpaceX plan on using the Merlin 1C or the standard Merlin 1?  Additionally, how difficult will it be to mod the Merlin for air-start?  Is this a capability that's already been built-in?  If not, it may be quite difficult to pull off (in light of the obstacles to making the SSME into an upper-stage engine.)

[hyper_snyper]

Well it's not like SpaceX has a sprawling amount of ground support equipment as part of their launch concept.  If the Merlin can rely on its own devices for starting at sea level, igniting one mid-flight shouldn't be as crazy as getting the SSME to air-start.

The thing about Merlin that puzzles me is how they're planning on protecting it and anything else vulnerable to sea water when (or if) they start recovering and reusing these stages.

[Jim]

CFE - 30/3/2008  7:50 PM

On the Falcon IX upper stage, does SpaceX plan on using the Merlin 1C or the standard Merlin 1?  Additionally, how difficult will it be to mod the Merlin for air-start?  Is this a capability that's already been built-in?  If not, it may be quite difficult to pull off (in light of the obstacles to making the SSME into an upper-stage engine.)

Air starting an engine is not difficult, only air starting the SSME.  It doesn't use spin start cartridges. hypergol igniters, or boost pumps.  It just uses head pressure

[wannamoonbase]

hyper_snyper - 30/3/2008  8:07 PM
...The thing about Merlin that puzzles me is how they're planning on protecting it and anything else vulnerable to sea water when (or if) they start recovering and reusing these stages.

Great question.  I have been wondering about the effects of being submerged in salt water as well.

That's one big reason I liked the K1's approach to launching over land and using airbags.  To bad some internet billionaire didn't try that approach.  With proper funding maybe it would have worked.

[Lee Jay]

Need a real rocket engineer here.

I've somewhat surmised that the expensive bits of a modern large liquid engine are the controllers, turbo-machinery, valves and plumbing above the combustion chamber.  I'm not sure about the injectors and combustion chamber.  The nozzle seems to be somewhat inexpensive unless its regenerative in which case it's more but not unreasonable.

First of all, that might all be false (hence the first sentence in this post).  But if it's true, wouldn't it be possible to seal all the expensive stuff inside something and just let the salt water flood the nozzle and combustion chamber, thereby saving the really expensive stuff, and at least in the case of an ablative nozzle throwing away mostly what's all used up anyway?

[Patchouli]

wannamoonbase - 30/3/2008  8:55 PM

hyper_snyper - 30/3/2008  8:07 PM
...The thing about Merlin that puzzles me is how they're planning on protecting it and anything else vulnerable to sea water when (or if) they start recovering and reusing these stages.

Great question.  I have been wondering about the effects of being submerged in salt water as well.

That's one big reason I liked the K1's approach to launching over land and using airbags.  To bad some internet billionaire didn't try that approach.  With proper funding maybe it would have worked.

That part also always bugged me but I guess they feel they can just decontaminate it as well as simply avoiding use alloys that are prone to corrosion.

They also could have the stage impact the ocean nose first which would protect the engines from the shock of hitting the ocean at least.

Personally I'd prefer the first stage have a scissor wing or similar but spacex does have some first rate engineers who likely know what they are doing and feel they can solve this problem.

The K1 needed a very large first stage so it could perform that RTL maneuver it also didn't travel far from the launch site.

It also needed very a high performance second stage as well.

The NK-33s are higher ISP engines then the turbine cycle merlin 1C engines Falcon uses which give better mass margins in exchange for higher costs.

As for dragon it's self they seem to be just making sure it's completely seaworthy on the safety issues with splash downs.


Who knows maybe BIll Gates will fund the K1 since it seems every billionaire has a space project and he wouldn't want to be left out.

[madscientist197]

Jim - 30/3/2008  3:01 PM

CFE - 30/3/2008  7:50 PM

On the Falcon IX upper stage, does SpaceX plan on using the Merlin 1C or the standard Merlin 1?  Additionally, how difficult will it be to mod the Merlin for air-start?  Is this a capability that's already been built-in?  If not, it may be quite difficult to pull off (in light of the obstacles to making the SSME into an upper-stage engine.)

Air starting an engine is not difficult, only air starting the SSME.  It doesn't use spin start cartridges. hypergol igniters, or boost pumps.  It just uses head pressure

This is a bit OT, but a rather interesting article on the start/shutdown cycle of the SSME - it's pretty complex, but interesting:
http://www.enginehistory.org/SSME/SSME3.pdf