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Thread: SpaceX

  1. #2011
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    Raptor tidbits

    Everyday Astronaut @Erdayastronaut
    Want to know how @SpaceX's Raptor engine works? Confused about what the full flow staged combustion cycle is? Why are they using methane? How's the Raptor compare to other rocket engines? My deep rundown on the Raptor is finally up! Great engine @elonmusk https://youtu.be/LbH1ZDImaI8
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    Elon Musk ✔ @elonmusk
    Great video. Couple notes: Raptor designed for subcooled CH4/O2, so propellant density & thrust increase up to ~8%, as needed for mission. 380 Isp & up to 50% thrust/weight improvement over time. Merlin thrust/weight doubled from V1, but Raptor is closer to optimum.
    4:44 PM - May 25, 2019
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    SPEXcast @SPEXcast
    Replying to @elonmusk and 2 others
    What does the improvement path of raptor look like? Mainly propellant changes or improvements to turbopumps/injectors?
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    Elon Musk ✔ @elonmusk
    Propellant stays same, but almost everything else improves. Fundamental goal is minimize cost per ton to surface of Mars.
    4:56 PM - May 25, 2019

    https://twitter.com/elonmusk/status/1132386984444383233

  2. #2012
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    Regarding an earlier post:

    Free Thinker @curiousmind44
    What are your thoughts on ONeil structures @JeffBezos talked about?
    >
    Elon Musk @elonmusk
    Replying to @curiousmind44 @SPEXcast and 8 others
    Makes no sense. In order to grow the colony, youd have to transport vast amounts of mass from planets/moons/asteroids. Would be like trying to build the USA in the middle of the Atlantic Ocean!
    Admittedly, it doesn't matter much at this point, and it is just a Twitter length argument, but I can't agree with that. Building on worlds has severe limitations as well, with sunlight cycles, gravity, surface temperature, etc. issues It probably makes a lot more sense at least to build a habitat near an asteroid than on one, and not even necessarily near an asteroid (since it's the cost of moving the mass that matters, not so much the time it takes). In any case, whether on a world or not, you still need to build a habitat. It isn't like you can just move somewhere and breathe the air.

    Then too, he might just be arguing because it's counter to what Bezos is saying. Ah well.

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  3. #2013
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    Another StarLink swarm video

    https://youtu.be/uZWgD_9qJdE

  4. #2014
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    Quote Originally Posted by Van Rijn View Post
    Regarding an earlier post:

    Admittedly, it doesn't matter much at this point, and it is just a Twitter length argument, but I can't agree with that. Building on worlds has severe limitations as well, with sunlight cycles, gravity, surface temperature, etc. issues It probably makes a lot more sense at least to build a habitat near an asteroid than on one, and not even necessarily near an asteroid (since it's the cost of moving the mass that matters, not so much the time it takes). In any case, whether on a world or not, you still need to build a habitat. It isn't like you can just move somewhere and breathe the air.

    Then too, he might just be arguing because it's counter to what Bezos is saying. Ah well.
    Right. You have to have large amounts of processed materials to build a Mars or Moon habitat. Smelting metals, lots of chemical processing, even large scale water purification all require heavy industries on site.

    And then you have to move it all from wherever you got it, to wherever you build your shelters; On a world, that means overland transport, or flight. And trucks and trains also have to be built or shipped, whereas in space you already have the rockets that got you there which can also ship your cargo, if you can refuel them.

    ADDED: Not to mention, you'd be at the mercy of local gravity levels, but a space station can spin at a full 1G.
    Last edited by Noclevername; 2019-May-26 at 07:27 AM.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  5. #2015
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    Right. You have to have large amounts of processed materials to build a Mars or Moon habitat. Smelting metals, lots of chemical processing, even large scale water purification all require heavy industries on site.

    And then you have to move it all from wherever you got it, to wherever you build your shelters; On a world, that means overland transport, or flight. And trucks and trains also have to be built or shipped, whereas in space you already have the rockets that got you there which can also ship your cargo, if you can refuel them.
    For a habitat of similar size, this argument is not true. Either you take all the required construction components for the habitat to your destination (other planet/asteroid/moon... or space) with rockets, so there is no difference in the amount of material you move by rockets. Alternatively, you mine/make stuff locally on the planet, and in that case a habitat in space would mean you'd have to launch it back into space which will never be easier than on-planet transport (as worst case, you could do that by rockets as well and you could have rockets on the planet and/or in its orbit as something would have brought you and your stuff to that planet).

    Now that doesn't mean a space habitat is never the best decision, though I think for really large habitats you'd better go on-planet. For smaller bases you indeed have the advantage in space that you can pick your gravity, solar exposure. In space you don't have to worry about stability of the surface and the environment is more predictable. Depending on its location, visiting craft could have less of a gravity well issue. Then again, there might be more radiation and micrometeorite issues. And a very important question is: is your final destination the planet or not, and what do you want to do on that planet? So, basically, horses for courses.
    Last edited by Nicolas; 2019-May-26 at 08:53 AM.

  6. #2016
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    Quote Originally Posted by docmordrid View Post
    The StarLink Train....
    Just how bright are these objects, and how bright will they be in higher orbit?

    https://www.space.com/spacex-starlin...sky-video.html

    ETA: they don't seem to have made the heavens above pages yet https://www.heavens-above.com/Satellites.aspx

  7. #2017
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    Quote Originally Posted by Nicolas View Post
    For a habitat of similar size, this argument is not true. Either you take all the required construction components for the habitat to your destination (other planet/asteroid/moon... or space) with rockets, so there is no difference in the amount of material you move by rockets. Alternatively, you mine/make stuff locally on the planet, and in that case a habitat in space would mean you'd have to launch it back into space which will never be easier than on-planet transport (as worst case, you could do that by rockets as well and you could have rockets on the planet and/or in its orbit as something would have brought you and your stuff to that planet).
    Traditionally, you'd mine stuff for an orbital habitat from an asteroid, which has a negligible gravity well. No need to "launch it back into space", it's already in space.

    Some Near Earth Objects can be reached from Earth with less Delta V than a Moon landing.

    But none if this derail is about SpaceX per se, so ...
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  8. #2018
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    At least in the first 3 years it's not about SpaceX, but you never know with those guys.

    (And I do agree that when the discussion is "in space vs 'small' asteroid", it becomes different from "in space vs big planet" in favour of the space solution.)

  9. #2019
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    Quote Originally Posted by grapes View Post
    Just how bright are these objects, and how bright will they be in higher orbit?

    https://www.space.com/spacex-starlin...sky-video.html

    ETA: they don't seem to have made the heavens above pages yet https://www.heavens-above.com/Satellites.aspx
    I've seen estimates of mag 3-5, but dimming as they separate and raise their orbits.

  10. #2020
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    Quote Originally Posted by Nicolas View Post
    At least in the first 3 years it's not about SpaceX, but you never know with those guys.
    Here's hoping!
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  11. #2021
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    Not sure if this has been covered, but.
    https://toughsf.blogspot.com/2019/05...planetary.html
    Starship could be (if refueled in Earth orbit) capable of boosting a "stripped down" payload ...47 days to Mars!
    Blogger "Matterbeam" did the math, extrapolated from Musk's claims (so as always, grain-o-salt)
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  12. #2022
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    Did he take into account that the stainless steel vehicle may be lighter than the composite versions 85t? Less mass in the TPS covering a smaller percentage of the hull, the lighter joinery, stainless steel's structural advantages etc.

  13. #2023
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    Quote Originally Posted by docmordrid View Post
    Did he take into account that the stainless steel vehicle may be lighter than the composite versions 85t? Less mass in the TPS covering a smaller percentage of the hull, the lighter joinery, stainless steel's structural advantages etc.
    The 85-90 ton figures are for the crewed version. It has to have a large habitable volume, life support systems and other contributors to a larger dry mass.

    The uncrewed version can dispense with all that. Its dry mass is reported to be 60-75 tons. The mass ratio increases to 18-22, as good as that of the Falcon 9 booster stage.

    This tweet from Elon Musk introduces what we’ll be calling the Starship Lite – a stripped-down version with no features meant for re-entry, recovery or holding a payload. It would be a naked steel tank with an engine at the bottom and used solely in space.

    Starship Lite has a mass ratio of 30, from a wet mass of 1200 tons and a dry mass of 40 tons. It is unknown why the wet mass is lower than previously stated. The engines can be optimized for the vacuum environment – the addition of huge nozzles increases their Isp to 380s.

    Going through the deltaV equation again, we find a value of 12.7km/s.
    The bolded difference might be because of the steel build instead of composites, I think.
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  14. #2024
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    That would be a disposable vehicle like StarHopper, without legs or TPS, hauling StarLink based payload swarms in the aft payload bins. Perhaps a nose fairing + payload if needed.

  15. #2025
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    Quote Originally Posted by docmordrid View Post
    That would be a disposable vehicle like StarHopper, without legs or TPS, hauling StarLink based payload swarms in the aft payload bins. Perhaps a nose fairing + payload if needed.
    A glorified Big Dumb Booster?
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  16. #2026
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    Quote Originally Posted by Noclevername View Post
    A glorified Big Dumb Booster?
    Reusable booster, disposable upper stage or a refillable tanker for deep space Starship missions. With a cryocooler (mentioned by Musk) boiloff wouldn't be an issue.

  17. #2027
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    The vehicle could start out sitting in Low Earth Orbit, fuelled and ready to go. It could be a regular Starship that was converted in space instead of returned to Earth. Filling it up would take about 12 tanker launches.

    Alternatively, it could be boosted into an extremely elliptical orbit, reaching out to beyond the Moon in apoapsis (400,000km) and just above the atmosphere in periapsis (200km). Tankers would struggle to match its orbit and deliver more fuel, increasing the number of launches required to fill it up to 70 (!).
    So refills for a Mars trajectory would be expensive in launches? We need that ISRU! C'mon, Musk, get with the ice mining!
    "I'm planning to live forever. So far, that's working perfectly." Steven Wright

  18. #2028
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    ISRU is part of the R&D.

    Starlink 480.jpg

    Starlink is targeted to offer service in the Northern U.S. and Canadian latitudes after six launches, rapidly expanding to global coverage of the populated world after an expected 24 launches. SpaceX is targeting two to six Starlink launches by the end of this year.

    SpaceX
    https://www.starlink.com/

  19. #2029
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    Any date info for the hopper?

  20. #2030
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    They've been doing tanking tests and fitting the umbilical claw, with methane tests in recent days - flare stack lit etc.

    Raptor SN4 is supposed to arrive near the end of this week, with integration and an untethered short hop after a wet dress rehearsal.

    Fins and legs/landing gear on the orbital Starship about the end of June.

    The Super Heavy booster #1 build starts in about 3 months.
    Last edited by docmordrid; 2019-May-28 at 07:53 PM.

  21. #2031
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    Quote Originally Posted by docmordrid View Post
    They've been doing tanking tests and fitting the umbilical claw, with methane tests in recent days - flare stack lit etc.

    Raptor SN4 is supposed to arrive near the end of this week, with integration and an untethered short hop after a wet dress rehearsal.

    Fins and legs/landing gear on the orbital Starship about the end of June.

    The Super Heavy booster #1 build starts in about 3 months.
    Ok, I wish them well

  22. #2032
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    Whoops...

    4th rocket from the left in this NASA doc is the 2017 Starship/Super Heavy.

    Eric Berger ✔ @SciGuySpace (Ars Technica)
    That looks like Starship/Super Heavy under the rockets NASA is considering using for Moon 2024. First time I've ever seen that vehicle on a NASA human exploration chart. Not sure it means much, but it is interesting.

    IMG_20190528_161230.jpg
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    Andrian @SomeAndrian
    It means NASA's new bold plan will indeed be a ticket purchase on a Starship flight
    12:45 PM - May 28, 2019

    https://twitter.com/SciGuySpace/stat...13670871019521

  23. #2033
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    Another, same presentation

    Imagery like this needs approval...

    Eric Berger ✔ @SciGuySpace
    More Starship/SuperHeavy in NASA graphics describing the Moon 2024 program.
    12:47 PM - May 28, 2019

    IMG_20190528_164551.jpg

    https://twitter.com/SciGuySpace/stat...14550278090752

  24. #2034
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    Quote Originally Posted by docmordrid View Post
    Another, same presentation

    Imagery like this needs approval...

    Eric Berger ✔ @SciGuySpace
    More Starship/SuperHeavy in NASA graphics describing the Moon 2024 program.
    12:47 PM - May 28, 2019

    IMG_20190528_164551.jpg

    https://twitter.com/SciGuySpace/stat...14550278090752
    Looks like F9 and F9H on that one as well.
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  25. #2035
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    The first image has some scale issues right? Or is this the lesser know "somewhatsuperheavy" launcher?

  26. #2036
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    Quote Originally Posted by docmordrid View Post
    Whoops...

    4th rocket from the left in this NASA doc is the 2017 Starship/Super Heavy.

    Eric Berger ✔ @SciGuySpace (Ars Technica)
    That looks like Starship/Super Heavy under the rockets NASA is considering using for Moon 2024. First time I've ever seen that vehicle on a NASA human exploration chart. Not sure it means much, but it is interesting.

    IMG_20190528_161230.jpg
    |
    Andrian @SomeAndrian
    It means NASA's new bold plan will indeed be a ticket purchase on a Starship flight
    12:45 PM - May 28, 2019

    https://twitter.com/SciGuySpace/stat...13670871019521
    My personal opinion is that if NASA has any hope of putting humans on the Moon by 2024, they will have to at least give serious consideration to both existing hardware and stuff in the short pipeline, such as the various SpaceX rockets.
    At night the stars put on a show for free (Carole King)

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  27. #2037
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    Quote Originally Posted by Nicolas View Post
    The first image has some scale issues right? Or is this the lesser know "somewhatsuperheavy" launcher?
    Scaling issues, plus it's an outline of the 2017 Starship which was 6 meters shorter. It's now 118 meters - a friggin monster.

    Super_Heavy-lift_launch_vehicles (1024).jpg
    Last edited by docmordrid; 2019-May-29 at 03:32 AM.

  28. #2038
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    Kathy Leuders is NASA's Program Manager for Commercial Crew.

    Eric Berger ✔ @SciGuySpace (Ars Technica)
    Kathy Lueders says SpaceX is still working toward a crew launch of the Dragon spacecraft by the end of this year. She offered a big caveat. "I would say we need to close out the anomaly investigation. I think that's the big thing."
    2:51 PM - May 28, 2019

    https://twitter.com/SciGuySpace/stat...45683128799232

  29. #2039
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    Quote Originally Posted by docmordrid View Post
    Scaling issues, plus it's an outline of the 2017 Starship which was 6 meters shorter. It's now 118 meters - a friggin monster.

    Super_Heavy-lift_launch_vehicles (1024).jpg
    The size difference of the item placed on the moon is quite incredible between Saturn 5 and Starship. Sure, a lot of Starship's volume will be empty tanks by then, but still.

  30. #2040
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    Quote Originally Posted by Nicolas View Post
    The size difference of the item placed on the moon is quite incredible between Saturn 5 and Starship. Sure, a lot of Starship's volume will be empty tanks by then, but still.
    Orbital refuelling + reusability makes for a huge difference in capability.

    Launch mass

    Lunar Module: 16.4t (extended version)
    Starship: ~1,335t

    Internal volume

    Lunar Module: 6.7 m3
    Starship: ~1,100 m3 (habitat + upper cargo deck)
    Last edited by docmordrid; 2019-May-29 at 01:38 PM.

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