Planetary Transfer Calculator | Hacker News Reader

Planetary Transfer Calculator

transfercalculator.com

99 pointsT-A26 comments

If you're interested in this kind of stuff, the NASA General Mission Analysis Toolkit (GMAT) is open source and is actively used to do navigation analysis for multiple missions which are currently flying.

http://gmatcentral.org/

A mouse over description for TMI MTO MCO and MOI would be great, those acronyms are meaningless to me. Edit - found as labels under ΔV Breakdown heading

Could also use an explanation of what it means to "calculate a transfer". Like, the ΔV? The travel time? All possible parameters? Frustrating that if you click on "What It Does", it doesn't clarify.

Most orbital calculations are "optimizations." You are looking for either the best time or most efficient orbit that your craft can achieve. Most of the time you are guessing at initial conditions that will produce a desired orbit and then moving down a gradient to a local optima.

Other times you are looking to predict the velocity and position of an orbital body at a certain time. Since there are many large planets in the solar system this requires non-linear differential equations that can only be solved (at this time) using an approximate calculation using methods such as the Euler or Runge-Kutta method in a computer.

https://en.wikipedia.org/wiki/Runge%E2%80%93Kutta_methods

I've often seen artist renditions of how our solar system looks, and a lot of people complain that it isn't a flat disk, that all of the planets are trailing behind the sun as it flies through our galaxy. What I've always been interested in is what that then looks like in our section of the galaxy. https://www.youtube.com/watch?v=C4V-ooITrws is probably the best example of the trailing nature that I've seen. Does anyone have suggestions for the movement through the galaxy bit as well?

That video has some flaws which are covered in this helpful article from Phil Plait https://slate.com/technology/2013/03/vortex-motion-viral-vid...

> It’s wrong. And not just superficially; it’s deeply wrong, based on a very wrong premise.

If you read further down in Phil Plait’s article, the video is based on a conspiracy-theory-style paper written by a crazy guy.

Are there examples of better videos? I haven't seen any, and I'd really love to. I want to understand what our solar system actually looks like, and the video I linked is the closest thing I've seen (even if wrong).

The Sun and planets basically do form a disk. The fact that the solar system as a whole is also moving through the galaxy is not relevant to its shape, basically because any external forces (like the tidal force, a difference in force between radially separated points on orbiting object) are not strong enough to affect that shape.

My understanding is that the solar system formed out of a volume of gas and dust. Over time, gravity caused that volume to collapse inward; this in turn led to a bulging in the plane perpendicular to the axis of rotation. This is the same reason that the Earth bulges at the equator. But since a volume of gas and dust is rather less dense than Earth, nothing opposes gravity condensing it further. So it gradually flattened into a thick disk.

Wikipedia’s “Protoplanetary disk” page explains this process with far more fidelity than I ever could. My point is, there’s a good reason the solar system is a disk: it was formed that way to begin with.

I'm writing a Sci fi novel and I can use this to help me build narratives! So cool!

Track Starman and his Tesla from the Falcon Heavy test, and the Monolith from 2001. Switch to "The Expanse" mode and calculate transfers with Epstein Drive.

A++

Greetings. I'm a complete idiot when it comes to space. Still trying to wrap my head around "direction," navigation and just how to see or look in space. Would love a portable version of this program. Finally, can someone offer up the difference between Planetary Transfer Calculator and Space Engine? Thanks

Someone already mentioned it upthread, but I highly recommend playing "Kerbal Space Program" to gain a better intuition of orbital mechanics. I'm no rocket scientist but that game really helped me wrap my head around how things like orbital transfers work without actually learning any of the math behind it.

Thank you very kindly. I will take a look at it post haste.

Does that use the real trajectories of the planets (such as give by the JPL ephemerides) or or eliptical approximations ?

Interestingly a transfer from Earth to Jupiter ends up with Jupiter coming up on the ship from behind at twice it's velocity - I would never have guessed that to be the case, one always imagines a ship arriving at a somewhat relatively static object.

Basically, everything in space is a moving target.

If you'd really like to nail home an almost intuitive understanding of orbital mechanics, I recommend Kerbal Space Program. Imagine Minecraft NASA. You plan, build, launch, and fly space missions using a simplified physics model. It's insanely fun and addictive, as long as you can get past the frustrations of early failures.

I cannot recommend this game enough. I've got hundreds of hours in, and I'm at the point where I've got huge spreadsheets carefully planning out mission parameters to spec the requirements for my new heavy launch platform to colonize the solar system. I'm even assembling a long-term research station in orbit that will eventually be parked around a gas giant.

What you actually want is KSP modded with Principia to give you an n-body simulation of the solar system.

https://github.com/mockingbirdnest/Principia

The existing SOI model is still good enough to give a more intuitive understanding of orbital mechanics. Also did they ever fix the Jool system in Principia? Never played with it but iirc there was an issue with Jool where one of the inner moons would very quickly be ejected from the system.

Given that it's a toy solar system, it's entirely possible that there's no stable configuration for Jool's system with its full set of moons :/

Fun! A way to add gravity assist and multiple gravity assists would be a great feature.

Still gotta wait for 11 years approx to reach Saturn even travelling in high speed.Long wait will try to post a reply back from Saturn once i land there safely.

You know Saturn is a gas giant, right?

WFSMC? Working from Saturn's Metallic Core?

Stellarium[0]

[0] http://stellarium.org

Stellarium is a planetarium software. It doesn't help you calculate interplanetary transfers, so if you're just mentioning it because it's a tangentially related and undeniably great piece of software, you might want to elaborate a bit.

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