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NASA’s DART mission flew on a falcon 9, but it flew 7 million miles. That’s a lot further away than the moon is, so why would falcon heavy or starship ever be necessary to go there? Why can’t people just go to the moon in a falcon 9? I’m sure there’s a very good reason, I just don’t know it.

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    $\begingroup$ Does the human need to be alive upon reaching the moon? Or on return? $\endgroup$
    – Jon Custer
    Commented Jul 10, 2023 at 19:22
  • $\begingroup$ The DeltaV required from LEO or from the Earth's surface is not all that different to the DeltaV to get a Lunar intercept trajectory. As is pointed out in the answer below (@russelborogove), DART was tiny compared to a human landing system. The feasibility of the refuel system for Starship is already in question, and though the Falcon 9 is a powerful launcher, it is still not designed for a lunar transfer, insertion, etc. I see what you're getting at, but I'm not sure that the question is particularly usefull. $\endgroup$ Commented Jul 10, 2023 at 23:51
  • $\begingroup$ The JFK commitment was "landing a man on the Moon and returning him safely to the Earth". $\endgroup$ Commented Jul 11, 2023 at 9:49
  • $\begingroup$ You should check out Kerbal Space Program, and you'll get a much better handle on why this isn't possible. $\endgroup$
    – Steve
    Commented Jul 17, 2023 at 22:11

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For a given destination - the moon, Mars, or a particular asteroid - you need a rocket sized proportionally to the payload you want to send there. DART was a very small payload -- only 610kg of mass. To land on the moon and return crew safely, you need something like 50 to 100 times larger payload (depending on how many people you want to take and how long you want to stay), which means you need a much more powerful rocket.

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    $\begingroup$ You should also address the main misconception that rocket performance has anything to do with how far a given destination is. (A rocket is not a car,gas mileage does not apply.) $\endgroup$
    – TooTea
    Commented Jul 10, 2023 at 20:42
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First: Falcon 9 is just a launch vehicle. DART is a complete spacecraft in its own right, with its own guidance and propulsion systems. (It was actually two spacecraft: DART itself was the impactor, and it deployed the LICIACube cubesat to observe the impact.) If you just duct-taped a human to the top of the Falcon 9 second stage, you could get them pretty far, but they'd die not long after liftoff.

SpaceX operates the Crew Dragon to put people into low orbit. Where DART+LICIACube together massed 624 kg, a Crew Dragon with 4 crew and 150 kg of supplies masses 9616 kg. That's over 15 times as much mass. Falcon 9 just can't throw that much mass to the moon, and the Dragon wouldn't be able to land on the moon when it got there.

You need a spacecraft capable of maneuvering, landing, and returning the crew. That will all take a much larger spacecraft or a combination of multiple smaller ones, and a much larger rocket to get it on its way to the moon.

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  • $\begingroup$ "a Crew Dragon with 4 crew and 150 kg of supplies masses 9616 kg" – And can only sustain the crew for a week. $\endgroup$ Commented Jul 12, 2023 at 4:44
  • $\begingroup$ @JörgWMittag 10 days, which would be enough for a short trip. And it could be extended...at the cost of adding more mass. The biggest shortcoming is propulsion...and of course the total lack of any way to land on and return from the lunar surface. These will not just add mass, they'll multiply the mass a few times over, just for a minimalist flags-and-footprints landing. $\endgroup$ Commented Jul 12, 2023 at 11:50

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