In particular I'm wondering; when an engine is throttled I have assumed the Mach number will stay constant, i.e., this number characterise a particular nozzle/throat/chamber design - and using this number one can calculate the exhaust pressure if given the chamber pressure (see spreadsheet for 90% throttle, for example).
Quote from: malu5531 on 02/24/2014 08:42 amIn particular I'm wondering; when an engine is throttled I have assumed the Mach number will stay constant, i.e., this number characterise a particular nozzle/throat/chamber design - and using this number one can calculate the exhaust pressure if given the chamber pressure (see spreadsheet for 90% throttle, for example). That assumption isn't quite correct, because the Mach number will change as the ratio of specific heats changes, and that ratio, of course, changes with chamber pressure.
kremlinology on the available Merlin data
A "staged combustion Merlin" would be a whole new engine. Not much would be in common.
Quote from: Lars_J on 03/04/2014 04:16 amA "staged combustion Merlin" would be a whole new engine. Not much would be in common.Well, the rocket would be in common. Seems like a lot of commonality to me.I know that the prop pumps are a very expensive part of the engine and they would need to change the turbine/pumps and routing, but would they need to change the feeds and engine attachments, nozzle? Would an SC cycle engine even fit into the space available?I think an important consideration is their long term plan for retaining the Falcon 9 in their operational inventory which I don't know.
Quote from: Lars_J on 03/04/2014 04:16 amA "staged combustion Merlin" would be a whole new engine. Not much would be in common.Well, the rocket would be in common. Seems like a lot of commonality to me.
Has anyone else considered that SpaceX may modify the Merlin D in order to achieve Elon's projected 15% increase in thrust (12 to 17 % depending on how you figure)?I have been wondering if maybe, just maybe they might convert the Merlin D engine fueling system to a staged combustion cycle. That would give them the performance and it is not totally unreasonable now that they are gaining experience in staged combustion by working on the Raptor engine. Building a smaller staged combustion engine than the Raptor makes some sense, and building one for LOX/RP-1 seems logical since they are familiar with and have available everything that goes into building and testing LOX/RP-1 engines.What do you think about a staged combustion Merlin D+?Would it be possible/practical/acceptable to test a SC Merlin D + on the Falcon 9 while leaving 8 of the engines as is?
They may yet produce a M1E version, being engineering driven company I'd be surprised if they didn't tweek the M1D. Reducing the manufacturing cost of engine is one reason to make a new version, 3D printing may add significant cost savings if they are not already using it.