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Comment by messe | Hacker News Reader

Getting into orbit would be rather difficult, as the probe would have have to match the planets velocity at perihelion. My instinct says it’s probably just on the edge of doable (although I’m not sure on which side), but I haven’t crunched the numbers. It would almost certainly need to be launched on a Delta-IV or Falcon Heavy class vehicle.

EDIT: s/perigee/perihelion. I could say periapse and be neutral, but perihelion sounds cool.

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The speed of Rosetta's comet at perigee is, I think, significantly grater than the max speed of this dwarf planet. The dwarf planet has a much higher apogee, of course, but escape velocity, corresponding to infinite apogee, is finite and not that large, and Rosetta had to go much deeper into the Sun's gravity well. So, as a non-expert who hasn't done the numbers, I'd guess matching pace with the dwarf planet would be easier (requiring less delta V and/or gravity assists) than Rosetta with the comet.

Somewhat unintuitively, thanks to the Oberth effect, it can be easier to reach escape velocity closer to an object, (Humorously portrayed in https://xkcd.com/1242).

Aside: if you are looking to learn more, I cannot recommend Kerbal Space Program enough.

I've been aware of people talking about Kerbal Space Program for years and years, but I lost interest in playing it when I heard it didn't do real N-body gravitational calculations because they were too intensive.

I still find that inexplicable. To me, it sounds like saying "our calculator only does basic arithmetic on four core machines, square roots are too slow".

I'd push back against that interpretation of the developer's design choices. Kerbal's use of patched conic approximations greatly lowers the difficulty of the game (it is a game) for most players; it enables a simple and coherent UI/UX; and it guarantees fixed orbits that make difficult in-space rendezvous like the Apollo program's accessible. Like Minecraft cubes, it creates a reliable foundation of simple abstractions that people can reason about, and build complicated strategies on top of. (Wouldn't Minecraft be unplayable if instead of cubes, it was arbitrary user-defined convex polyhedra? It's like that).

Upping the realism lowers the playability: games and simulators are subtly different things. Otherwise we'd all be playing STK/Astrogator instead of Kerbal, and AutoCAD instead of Minecraft, and sitting in city hall basements debugging spreadsheets in place of Cities: Skylines. The type of limitations that distinguish games from serious simulators are not accidents and not laziness, but deliberate design choices.

I concede this makes certain interesting topics like Lagrange points / halo orbits, masscons, and orbital precession inaccessible. That's part of the tradeoff.

Not really that inexplicable, it’s a video game. It’s not for computational reasons, but to make gameplay easier to reason about; because again, it’s a video game.

The mechanics are simplified, yes, but patched conics is quite a good approximation for many cases, and great for developing an intuition for the basics.

There is a mod that includes n-body calculations called Principia if you’re interested in that.

There's mod though! https://forum.kerbalspaceprogram.com/index.php?/topic/162200...

It’s quite good as well, written in C++ for speed with new versions released every lunar cycle (!). I’ve done some Lagrange orbits with it in the Kerbol solar system. Doing it with Realism Overhaul and Real Solar System is a bit harder…

I think you meant: https://xkcd.com/1244/

Whoops. Yep, that’s the one.

Maybe I’ll be vindicated when it turns out the planetoid is made out of grey goo.

Are you sure that the right xkcd link?

Already noted in a comment below. Too late to edit. It’s 2 off. It should be xkcd.com/1244.

It's difficult to believe that ten years from now, there'd be any serious options other than Starship and its future peers. (Incidentally, the Delta IV is already at end-of-life; ULA is replacing it with Vulcan and its Blue Origin engines. The final Delta IV-H launches are planned for 2023).

https://spacenews.com/ulas-delta-4-heavy-down-to-final-five-...

I more meant that it would take at least that size-class of heavy lift launch vehicle.

With Starship this would definitely be doable, and I’m really optimistic about it; I just wanted to be cautious in my predictions.

I also wouldn’t be surprised if Delta IV’s life gets extended. Vulcan is facing plenty of development delays, and Blue Origin are yet to produce anything useful.

In a few years, can't we look forward to SpaceX making it routine to refuel in orbit? If we assume that's feasible, I wonder what sort of missions it would enable, other than human spaceflight.

Hopefully yes. I was being conservative with my suggestions.

Might there be not some benefits to try to get into orbit around this object, like perhaps a free ride to the Oort Cloud maybe?

There's no such thing as a free ride. If you can soft land on it you're already going to the Oort cloud.

You could get a free ride by having it crash into you, but that's going to be like catching a bus by letting it hit you, at ten thousand miles an hour.

Maybe starship will be ready with orbital refueling in time to make a faster trip. Imagine being able to do a sample return mission from such an object.

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