Regarding a hypothetical Merlin 1E, maybe someone remembers - were there any rumors about it before it was revealed? If yes, how long before?
Rocketdyne engines have been tested to failure and that information has been made public.SpaceX can do what they like I guess. Sometimes the secrecy is a bit annoying.
Quote from: meekGee on 03/24/2013 03:05 amRegarding a hypothetical Merlin 1E, maybe someone remembers - were there any rumors about the 1D before it was revealed? If yes, how long before?What? There have been no 1E rumors.
Regarding a hypothetical Merlin 1E, maybe someone remembers - were there any rumors about the 1D before it was revealed? If yes, how long before?
Quote from: Lars_J on 03/24/2013 05:40 amQuote from: meekGee on 03/24/2013 03:05 amRegarding a hypothetical Merlin 1E, maybe someone remembers - were there any rumors about the 1D before it was revealed? If yes, how long before?What? There have been no 1E rumors.Actually, it is the opposite of rumors about SpaceX developing another evolution of the Merlin 1D. I haven't found it but do recall a statement from SpaceX or Musk himself that there would be NO Merlin 1E. And we heard about the 1D way, way back in the days of Falcon 1. The Falcon 1E was based on SpaceX moving from the Merlin 1C to the 1D.(Sorry if I misinterpreted an earlier post of "1E" to mean the rocket, which was planned, rather than the engine, which has not been planned or announced. I try to be quite explicit above.)
Quote from: Comga on 03/24/2013 03:24 pmQuote from: Lars_J on 03/24/2013 05:40 amQuote from: meekGee on 03/24/2013 03:05 amRegarding a hypothetical Merlin 1E, maybe someone remembers - were there any rumors about the 1D before it was revealed? If yes, how long before?What? There have been no 1E rumors.Actually, it is the opposite of rumors about SpaceX developing another evolution of the Merlin 1D. I haven't found it but do recall a statement from SpaceX or Musk himself that there would be NO Merlin 1E. And we heard about the 1D way, way back in the days of Falcon 1. The Falcon 1E was based on SpaceX moving from the Merlin 1C to the 1D.(Sorry if I misinterpreted an earlier post of "1E" to mean the rocket, which was planned, rather than the engine, which has not been planned or announced. I try to be quite explicit above.)It was Gwynne Shotwell. She was directly asked about it, and the answer was that there will be no 1E. Currenty the 'rumors' hint at a light hydrocabon staged combustion engine.
Revealing several new details of the 1D, Tom Mueller, propulsion engineering vice president, says the engine is designed to produce 155,000 lb. vacuum thrust and have a chamber pressure at “the sweet spot” of roughly 1,410 psia. “We’ve also increased the nozzle expansion ratio to 16 [compared with 14.5 on the Merlin 1C],” says Mueller, who adds that the initial engine “is doing better than we hoped.” The engine is designed for an Isp (specific impulse) of 310 sec. and has a thrust-to-weight ratio of 160:1. “We took structure off the engine to make it lighter. The engine we shipped [for test] to Texas was a development engine and hopefully the production engines will be even better,” he says.The 1D design incorporates many lessons learned from the earlier Merlins and is of a simpler design with an increased fatigue life. “We’ve added the ability to throttle between 70% and 100%. Currently we have to shut off two engines during ascent, and on this we will be able to throttle them all,” he says. The development will also provide the basis for a 1D-Vac version intended for the second stage of the planned Falcon Heavy. “There are no plans to build a 1E. It’s going to be a 1D with the same turbopump.”
Clipped from http://www.aviationweek.com/aw/generic/story.jsp?id=news/awst/2011/08/08/AW_08_08_2011_p27-354586.xml&headline=SpaceX%20Plans%20To%20Be%20Top%20World%20Rocket%20Maker&channel=defense, Aug 2011:-
Quote from: MP99 on 03/24/2013 07:28 pmClipped from http://www.aviationweek.com/aw/generic/story.jsp?id=news/awst/2011/08/08/AW_08_08_2011_p27-354586.xml&headline=SpaceX%20Plans%20To%20Be%20Top%20World%20Rocket%20Maker&channel=defense, Aug 2011:-This URL is broken. Goes to "Page Not Found"
I wonder if "able to throttle them all" means "will throttle them all. Don't you get a better isp at full throttle? Then again, all engines running would help engine out numbers some.
btw - is it even a given that when you throttle down, the ISP remains constant?The requirement to throttle for landing is for a very brief maneuver, so ISP is not of prime importance.So the solution might not be suitable for the long initial burn.
Quote from: meekGee on 03/25/2013 12:40 ambtw - is it even a given that when you throttle down, the ISP remains constant?The requirement to throttle for landing is for a very brief maneuver, so ISP is not of prime importance.So the solution might not be suitable for the long initial burn.Quite difficult that you'd keep isp the same. Even the RD-180 loses some 3 to 5 seconds when throttling. And that's probably one of the most efficient engines ever.
Yes but is Isp equal to fuel consumption? Maybe the Isp drops but the engines use less fuel due to lower thrust.
Quote from: krytek on 03/25/2013 12:56 pmYes but is Isp equal to fuel consumption? Maybe the Isp drops but the engines use less fuel due to lower thrust. Think of ISP has fuel efficiency. Dropping the ISP is the same as saying your car dropped from 30 mpg to 20 mpg. You used more fuel to go the same distance.