SpaceX does seem to use metric for most things except engine thrust.
Quote from: oldAtlas_Eguy on 06/27/2012 02:24 pmQuote from: 2552 on 06/27/2012 02:15 pmhttps://twitter.com/elonmusk/status/217973460348047360Quote from: Elon MuskMerlin fired at full thrust! Engine weighs half a ton, but has power equal to several Hoover DamsThat seems to be a confirmation that the weight is ~485-490kg.Assuming "ton" = "tonne" (or metric ton).If ton = 2000 lbs, then half-a-ton is 455 kg! But I still think you're right - SpaceX does seem to use metric for most things except engine thrust.cheers, Martin
Quote from: 2552 on 06/27/2012 02:15 pmhttps://twitter.com/elonmusk/status/217973460348047360Quote from: Elon MuskMerlin fired at full thrust! Engine weighs half a ton, but has power equal to several Hoover DamsThat seems to be a confirmation that the weight is ~485-490kg.
https://twitter.com/elonmusk/status/217973460348047360Quote from: Elon MuskMerlin fired at full thrust! Engine weighs half a ton, but has power equal to several Hoover Dams
Merlin fired at full thrust! Engine weighs half a ton, but has power equal to several Hoover Dams
Quote from: MP99 on 06/27/2012 04:35 pmQuote from: oldAtlas_Eguy on 06/27/2012 02:24 pmQuote from: 2552 on 06/27/2012 02:15 pmhttps://twitter.com/elonmusk/status/217973460348047360Quote from: Elon MuskMerlin fired at full thrust! Engine weighs half a ton, but has power equal to several Hoover DamsThat seems to be a confirmation that the weight is ~485-490kg.Assuming "ton" = "tonne" (or metric ton).If ton = 2000 lbs, then half-a-ton is 455 kg! But I still think you're right - SpaceX does seem to use metric for most things except engine thrust.cheers, MartinBut he isn't trying to be accurate here, look at the other side of the equation "several Hoover Dams" - hardly accurate is it. All we can say from this statement is that it is within maybe 10% of "half a ton" where ton could mean tonne.
Things to keep in mind: Would a staged combustion engine weigh more or less than a gas generator engine?Merlin 1D (GG) now has the highest (vacuum) T/W ratio of any engine, even higher than the NK-33.
Quote from: Robotbeat on 06/27/2012 06:46 pmThings to keep in mind: Would a staged combustion engine weigh more or less than a gas generator engine?Merlin 1D (GG) now has the highest (vacuum) T/W ratio of any engine, even higher than the NK-33.From what I've seen explained, the SC engine needs higher strength (due to higher temperature and pressure), but uses smaller diameter diameters, for equal thrust. And since you have the material (i.e. weight) needs decreasing cubically but diameters only decrease to the square, it's quite possible that you'll end up pretty close.Let's remember that the NK-33 is a 45 years old engine. And still it's 130T/W vs more then 150T/W for the Merlin 1D. I don't know if you could apply some tricks of the Merlin 1D to improve the T/W of the NK-33. But I guess it's not necessary impossible to get similar (say, 10%) T/W. How much T/W (and thus fmp) are you willing to sacrifice for the increased isp, that depends heavily on your overall requirements.What I can say, is that SC is a lot more expensive to develop than GG.
The statement that the previous method was plating makes me more curious. It implies that the channels in the 1C chamber/nozzle are on the *inside* face of the central layer. If they were on the outside, then the plating process would just fill in the channels, instead of leaving them open.I don't expect all these details to be known, tbh. I doubt SpaceX wants to share every last detail of their manufacturing process with their competitors.
I believe that the higher pressures in SC mean an engine is less likely to fail in a benign way. To the extent that F9/FH have engine out, it would possibly be compromised by a switch to SC.However, this is OT for updates on 1D.cheers, Martin
Quote from: MP99 on 06/27/2012 07:16 pmI believe that the higher pressures in SC mean an engine is less likely to fail in a benign way. To the extent that F9/FH have engine out, it would possibly be compromised by a switch to SC.However, this is OT for updates on 1D.cheers, MartinBefore we even talk about the performance benefits of a Staged Combustion cycle and if it decreases reliability and safety margins, I think we should why we want to totally change the design of the Merlin in exchange for about 20 Isp. In short, why do we want more performance?The F9 already has payload capacity of the EELVs. The FH already beats them by a factor of 2. That 20 Isp may get you another 2 tons of lift in an F9 and up to 5 on the FH. Really, does have 15 tons instead of 13 and/or 58 instead of 53 help SpaceX expand their launch manifest in any tangible way? If not, why isn't a simpler, safer, cheaper to build engine preferable to one with higher performance?
If they execute on FH and get their flight rate up while maintaining (advertised) prices they win. But even in that scenerio, getting a high isp vac engine would provide a dramatic boost in performance for both rockets.
Quote from: CapitalistOppressor on 06/28/2012 10:27 am If they execute on FH and get their flight rate up while maintaining (advertised) prices they win. But even in that scenerio, getting a high isp vac engine would provide a dramatic boost in performance for both rockets.There are two ways to look at this...(1) If that engine costs say $500 million to develop and probably a little more to produce, it may make more sense to simply use the money to give the customers of the next 50 launches a $10 million discount. That's 4~6 years worth and will firmly establish the company as the player to beat in the industry.(2) Another way to look at it however is that SpaceX has hired the minds and made the capital investments to design, develop and qualify rocket engines. Unless they want to immediately layoff their hard won talent pool, they will have to keep them on the payroll. This becomes a fix cost whether they use them to develop a new rocket engine or not. A large part of the development cost of a new engine hence will become an overhead they will have to pay whether they do anything with it or not.But, if it's me, Super Draco and the launch escape application has way higher priority than upgrading the main propulsion engine(s) for the Falcon family. Beyond that, Super Draco can and should be developed into a long endurance engine. Long endurance meaning that it can be fired for 1~2 hours continuously. If you want to go to mars and come back, you need something that can sit in space for up to a year, then fire for that 0.9 km/s mars capture burn, possibly another 1.4km/s for MCO-LMO transition and another 1.4 km/s for earth return. A mission like that will probably need to burn tens of tons of propellant and it'll have to be truly storable propellant (nothing using LOX). You don't need a big engine -- big engines are heavy and need heavy thrust structures. You are just as well served with a tiny engine with a decent Isp burning for a long time. You can burn an RCS class thruster for days, but as the burn time gets ridiculous the thermal problems become questionable for ablatives. However, a Super Draco class thruster burning for 2~3 hours during an insertion burn is not unreasonable.
Superdraco fired for 2 hours is 164,000kg of hypergols unless my math was terribly wrong. Even if there were a rocket that could put such a large spaceship into orbit.... The US would never allow it. crap is dangerous. A leak would be like a small nuclear bomb going off.
Quote from: Idiomatic on 06/29/2012 05:15 amSuperdraco fired for 2 hours is 164,000kg of hypergols unless my math was terribly wrong. Even if there were a rocket that could put such a large spaceship into orbit.... The US would never allow it. crap is dangerous. A leak would be like a small nuclear bomb going off.Actually that's about right if you want a 2 man mission to mass. You'll need about 30 tons in LMO -- that includes a 20 tons for the earth return stack, the rest you leave behind. It takes about 144 tons of MMH/N2O4 to put about 75 tons on TMI from LEO. 75 tons is necessary if you want to put about 30 tons into LMO because you need to lose about 2.3km/s to get from TMI to LMO. So you'll be burning about 140~150 tons of hypergolics in nearly 2-hour burn if you use a Draco class engine.As for putting that in orbit, it is not any more or less acceptable than launching a Titan with its 163 ton core booster loaded with 155 tons of Hypergolics. The difference is that you won't actually light it until it's in LEO where there are no collaterals to hurt if you blow up.
(2) Another way to look at it however is that SpaceX has hired the minds and made the capital investments to design, develop and qualify rocket engines. Unless they want to immediately layoff their hard won talent pool, they will have to keep them on the payroll. This becomes a fix cost whether they use them to develop a new rocket engine or not. A large part of the development cost of a new engine hence will become an overhead they will have to pay whether they do anything with it or not.
T/W of 150 with vac thrust of 161klbf makes the upper weight number of 488kg, 160 T/W would be 457kg, so the bounds on the weight seem to be 457kg < engine weight < 488kg.Stating that the T/W is more than 150 but not saying more than 160 means that it is somewhere between those two,....
Quote from: dwightlooi on 06/28/2012 04:53 amQuote from: MP99 on 06/27/2012 07:16 pmI believe that the higher pressures in SC mean an engine is less likely to fail in a benign way. To the extent that F9/FH have engine out, it would possibly be compromised by a switch to SC.However, this is OT for updates on 1D.cheers, MartinBefore we even talk about the performance benefits of a Staged Combustion cycle and if it decreases reliability and safety margins, I think we should why we want to totally change the design of the Merlin in exchange for about 20 Isp. In short, why do we want more performance?The F9 already has payload capacity of the EELVs. The FH already beats them by a factor of 2. That 20 Isp may get you another 2 tons of lift in an F9 and up to 5 on the FH. Really, does have 15 tons instead of 13 and/or 58 instead of 53 help SpaceX expand their launch manifest in any tangible way? If not, why isn't a simpler, safer, cheaper to build engine preferable to one with higher performance?This post is OT, as pointed out by Martin, but as long as we are living dangerously . . .a persuasive case that the proposed SC engine will burn CH3.http://forum.nasaspaceflight.com/index.php?topic=26995.0Third, SPX launchers would all get a big performance increase GTO and BEO with a high isp vac stage. What you think SPX needs is not what Elon thinks it needs. Elon badly wants to retire on Mars. He is not doing that with a M1d vac upper stage.Fifth, a lot of thread guesstimates point to the re-usability advantages of a CH4 SC engine in the context of Grasshopper. Recent Russian test data support this line of thinking. Elon <3's re-usability, because once he retires on Mars he wants you to be able to join him and that just can't happen unless he achieves his re-usability goals.However, in terms of SpaceX current business you are basically right. M1d on F9v1.1 and FH seem to service most/all of the current launch market, and (claims to) does it at (advertised) world beating prices. If they execute on FH and get their flight rate up while maintaining (advertised) prices they win. But even in that scenerio, getting a high isp vac engine would provide a dramatic boost in performance for both rockets.
Not an update on the engine, but starting my next CAD project.
Quote from: modemeagle on 06/30/2012 12:58 amNot an update on the engine, but starting my next CAD project.Great!Keep in mind though that according to the very latest photo's the turbopump has significantly changed.