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Space Transportation Earth Mars NASA Science

SpaceX Tests Its Raptor Engine For Future Mars Flights (techcrunch.com) 114

Thelasko writes: Elon Musk is preparing to unveil his plans to colonize Mars at the 67th annual International Astronautical Congress tomorrow. As a tease to his lecture, he has released some details about the Raptor engine on Twitter, including pictures. Mr. Musk states that, "Production Raptor coal is specific impulse of 382 seconds and thrust of 3 MN (~310 metric tons) at 300 bar." He goes on to note that the specific impulse spec is at Mars ambient pressure. The Raptor interplanetary engine is designed for use with Space X's Mars Colonial Transporter craft. Musk notes that the "chamber pressure runs three times what's present in the Merlin engine currently used to power Falcon 9," according to TechCrunch. "Merlin has specific impulse of 282 seconds (311 seconds in the vacuum of space), and a relatively paltry 654 kilonewton (0.6 MN) at sea level, or 716 kN (0.7 MN) in a vacuum. You can view a picture of the "Mach diamonds" here, which are visible in the engine's exhaust.
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SpaceX Tests Its Raptor Engine For Future Mars Flights

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  • by bruce_the_loon ( 856617 ) on Tuesday September 27, 2016 @03:19AM (#52967915) Homepage

    In before someone comments that they can't do R&D while simultaneously sorting out the recent problems with the Falcon 9.

    People can multitask, companies even more so. If they were still blowing up every vehicle on the pad, then maybe they'd have a point, but their systems are certainly working better than other programs at their stage of evolution.

    • their systems are certainly working better than other programs at their stage of evolution.

      That depends on which "other programs" you look at. Back in the 1950's and early 1960's when we were still learning rocketry and their were no textbooks? Sure. They're doing much better. Compared to more modern programs... they're doing worse. Much worse. The open question, the only real question, the one with no satisfactory answer... is whether the problems are inherent to a startup with no collective experi

  • 311 seconds of specific impulse in space vacuum is impressive. Combined with such a massive thrust of 3 Meganewtons, this certainly allows - on paper - for lifting heavy payloads onto a trajectory toward Mars. Another point to consider is the speed at which these developments are taking place. They're doing in a couple of years what took the Mercury and Jupiter programs, as preparations for the Saturn program, more than a decade. It remains to be seen, however, how much of this is just for the media and how

    • It's 382 in vacuum for the vacuum version of Raptor. Why mention the 311 s figure of Merlin with the 3 MN that the Merlin doesn't have?
      • The article made a ridiculous comparison between the non-vacuum optimuzed Merlin and the (near) vacuum optimized raptor. The merlin 1d vacuum is 348 sec, not 311.

        300 bar is pretty extreme for an engine. But SpaceX has so far had a good record with engines, so here's to hoping they can carry that forward :)

        • Chances are that even the sea-level version of Raptor will have its vacuum Isp in the 360-370 range anyway, so a comparison is still in order, but the particular mention of Merlin's vacuum Isp that I was responding to was clearly a mix-up.
          • by Rei ( 128717 )

            Chances are that even the sea-level version of Raptor will have its vacuum Isp in the 360-370 range anyway

            "Chances are" in no way that a sea-level version of a vacuum-optimized rocket with an Isp of 384 will have an Isp of 360-370. Merlin-1D vacuum has a vacuum ISP of 348, but the nearly identical Merlin-1D designed for atmospheric use (same thing, just without the nozzle extension) has a sea level Isp of 282 sec.

            • The sea-level versions of advanced kerosene engines already have a vacuum Isp of ~340. Methane will be higher than that, especially at somewhat higher pressure than the RD-1xx line. The and prototype RD-0162 methane engine is already at 356 s of vacuum Isp at 17 MPa. What's so difficult to understand about it? The effect of the vacuum nozzle will be smaller for Raptor because the higher pressure allows for a higher expansion nozzle even for the sea-level version.
              • by Rei ( 128717 )

                The sea level version of the aforementioned Merlin 1D is 311. Not "~340". We're comparing different nozzle versions of an otherwise identical engine. You don't lose a mere 15-25 sec ISP when losing your nozzle extension and operating at sea level. Period. That's just not reality. If you think for some reason that the Merlin-1D is a bad comparison, pick another engine with otherwise identical vacuum and sea level versions, and cite the vacuum ISP for the vacuum version and the sea level ISP for the sea

                • Look, I'm sorry but what sea-level Merlin does or doesn't achieve is totally irrelevant for Raptor - even for sea-level Raptor. The fact is that the 17 MPa LCH4/LOX sea-level RD-0162 is rated for 356 s of vacuum Isp, so the 30 MPa (+76%!) LCH4/LOX sea-level Raptor is definitely going to be in the 360+ s vacuum Isp territory. And that's including the assumption that the sea-level Raptor and vacuum Raptor are going to be identical units with different nozzles - the point is that the nozzles will be less dissi

                  • by Rei ( 128717 )

                    Look, I'm sorry but what sea-level Merlin does or doesn't achieve is totally irrelevant for Raptor - even for sea-level Raptor.

                    Because pointing out the typical difference between vacuum and sea level performance in hydrocarbon engines is "totally irrelevant" in a discussion about the difference in vacuum and sea level performance in hydrocarbon engines?

                    The fact is that the 17 MPa LCH4/LOX sea-level RD-0162 is rated for 356 s of vacuum Isp, so the 30 MPa (+76%!) LCH4/LOX sea-level Raptor is definitely going

                    • I simply responded to your unsubstantiated claim that '"Chances are" in no way that a sea-level version of a vacuum-optimized rocket with an Isp of 384 will have an Isp of 360-370' because it's actually very plausible that this (360-370 s) is actually the figure range to expect from the engine in question, which isn't a Merlin. Why compare apples with oranges?

                      I see your argument - all engines for a given propellant mixture are identical except for only one varying parameter (pressure). Why it's so simple, why didn't I think of that? ;) *snicker*

                      And that makes Merlin somehow more relevant?

                      Meanwhile, back in the real world, performance varies widely between different engine families, and there are many factors that affect them. What you're doing is equivalent to saying "Because my gasoline hybrid engine is super efficient, then your non-hybrid gasoline pickup truck engine should be too!" If you want to compare the performance of vacuum engines to sea level engines, you need to compare for the same engine.

                      The RD-0162 is the closest unit you can compare the Raptor with. It pushes all its propellant mass through

                    • by Rei ( 128717 )

                      Why compare apples with oranges?

                      Why show how much sea level and vacuum ISPs vary in other hydrocarbon engines? Because they vary that much in all engine, even non-hydrocarbons (same sort of difference in LOX/LH and solids). Methane is not some sort of magical exception to the rule.

                      The RD-0162 is the closest unit you can compare the Raptor with. It pushes all its propellant mass through the chamber. It uses the same propellant mixture. Therefore the real world vacuum performance of the sea-level version Ra

                    • Why show how much sea level and vacuum ISPs vary in other hydrocarbon engines? Because they vary that much in all engine, even non-hydrocarbons (same sort of difference in LOX/LH and solids). Methane is not some sort of magical exception to the rule.

                      Of course it is the case that even a single propellant mixture's performance varies depending on how it's used, but that does not make your comparison of a methane engine to Merlin [slashdot.org] any more relevant - less relevant, if that's even possible.

                      Well, well, well...would you look at that? [imgur.com]? Sea-level Raptor at sea level has an Isp of 334 s, where the by-you-mentioned Merlin 1D has a sea-level performance of the sea-level version at 282 s, as you claim. And you still claim that the sea-level version of Raptor can' [slashdot.org]

                    • by Rei ( 128717 )

                      Well would you look at that indeed! I argued for a loss of 348-282=66 sec in Merlin, and said that Raptor would be somewhat less of a difference but not much, as "chamber pressure has a positive but fairly weak correlation with ISP". You said 384 - "360-370" = 14-24 sec difference.

                      And the reality is... drumroll... the envelope please...

                      384-334 = 50 sec

                      I hope this has been a learning experience for you.

                    • VACUUM ISP. I really don't know at this point if you're trolling on purpose or if you've been simply cognitively challenged since birth. 334 s is a sea-level figure that has nothing to do with my claim about VACUUM ISP.
                • pick another engine with otherwise identical vacuum and sea level versions, and cite the vacuum ISP for the vacuum version and the sea level ISP for the sea level version. The sea level ISP will always be vastly lower, not a mere 15-25 sec.

                  You may have missed the part where I'm discussing the difference between vacuum Isps of the vacuum and the sea-level version of one engine (even in sea-level engines, the operation in diminished pressure is prolonged and therefore relevant), not between the sea-level Isp of the sea-level version and the vacuum Isp of the vacuum version. In case your comprehension is that bad, I'm spelling it out explicitly here. I've been trying to make it obvious by talking about vacuum Isp of sea-level engines explicitly

      • Thank you. I stand corrected.

    • by sconeu ( 64226 )

      3MN is pretty damned impressive. That's roughly half of what an F-1 engine produced.

  • "So they figured out how to get an engine to run on Mars, but they can't figure out how to <Uneconomical goal on Earth>. Will they find intelligence on Earth"?

  • ""Production Raptor coal is specific impulse of 382 seconds and thrust of 3 MN"
    That's impressive, considering they are using coal as the fuel!

  • by Thelasko ( 1196535 ) on Tuesday September 27, 2016 @10:43AM (#52969449) Journal
    SpaceX will be streaming Elon Musk's presentation live on their website. [spacex.com]

IN MY OPINION anyone interested in improving himself should not rule out becoming pure energy. -- Jack Handley, The New Mexican, 1988.

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