Comments by "H. de Jong" (@h.dejong2531) on "Could NASA 3D Print a New F-1 Rocket Engine?" video.

  1.  @ScienceBusted  The low density gas causes a tiny amount of drag. We can see this: satellites in orbits below ~1000 km slowly lose altitude due to this drag. The ISS loses about 25-50 km of altitude per year, so it regularly uses thrusters to boost itself back to its target altitude.
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  2. one cubic decimeter.
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  3. The reason we haven't been back yet is not "because we can't", it's because we decided to do other things.
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  4. It's unlikely we'll see a return of engines this large. We're moving towards reusability, and that's much easier to do when you have lots of smaller engines so you can just run one and get the small amount of thrust you need to land the stage. A stage with 5 F1 engines you'd have to throttle down one engine to under 10%, and it turns out throttling down a rocket by that much is difficult.
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  5. Yes. RocketLab has flown hundreds of 3D printed engines in their missions already.
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  6. We haven't forgotten how to do it. We can still do this today, but nobody in his right mind will want to because we have better methods for fabricating a nozzle.
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  7.  @papalaz4444244  I disagree with Curious Droid. We can build F-1 engines now using the same production method that was used in the 1960s. But that's a much more expensive and less reliable method than we have available today, so if we wanted to build an F-1 we'd redesign it to use modern manufacturing methods.
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  8. That's backwards, the Imperial system is the outdated one.
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  9.  @TheEvilmooseofdoom  or the same way the rocket engine itself works: by cooling the print head.
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  10. You're melting one drop at a time, instead of a whole vat as you'd do with casting. Old methods can be energy-intensive too.
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  11. 3D printing is being used by several rocket companies right now. RocketLab prints entire engines, as do others.
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  12. Why do you get so upset over a wrong answer one guy gave 10 years ago? We haven't been back to the moon yet because we decided to do other things (Space Shuttle, the ISS) which left no room in NASA's budget for manned lunar missions.
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  13. The injector manifold, and the nozzle were both complex. The nozzle consisted of hundreds of tubes brazed together. The manifold had tons of small holes.
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  14. The F-1 was built using lots of manual labor, e.g. brazing together thousands of tubes to make the nozzle. We can still do this today, but nobody in his right mind will want to because we have better methods for fabricating a nozzle. Those methods replace those thousands of tubes with one part milled on a CNC machine, followed by chemical deposition of the outer layer of the nozzle.
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