XKCD, orbital speed and travelling to Mars

I was scanning stack exchange and came to a VERY interesting question about travelling to Mars (as a kid I was HUGELY interested in space—and even at one time dreamed of being an astronaut :/).

The question seemed to have merit and upon reading it even I said, “Yeah, why don’t they do THAT?”

Even after reading the answers I didn’t really get it (actually, I only partially skimmed some of the comments), but somewhere in there was an XKCD link.

I thought ANY XKCD on this subject has to be cool and so I clicked on it and was given my first lesson in Orbital Speed

But before clicking on it, I had read one comment from Beska that suggested to read such-and-such about it and it would go “from ‘somewhat mysterious’ to ‘obvious'”. I didn’t read such-and-such, but I thought, in xkcd typical humour, it might actually shed some light, and it did!

source: http://www.extremetech.com/wp-content/uploads/2013/03/Inspiration_Mars_trajectory.svg_.png

First, the guys question:

it sounds like a reasonable question

He asked, why take such a long route to Mars, we are virtually flying from one extreme of the inner solar system, to the other extreme and back again, plus some. Why don’t we just fly from Earth’s orbit to Mars’ orbit and wait for it to come?
Sound reasonable?

I thought so. I did realise he was looking at it too simplistically, but I had no idea why. I made an assumption that it was going to be a “spacial awareness” thing and that his question was missing THAT point.

By spacial awareness I mean factors outside of a two dimensional representation of a three dimensional scenario within its own three dimensional scenario.

Ok, I didn’t say it was a SOUND argument! :P

I’ve heard the term “micro-gravity” with reference to the International Space Station and how the astronauts aren’t really weightless and I understand that, but what I didn’t understand was the true nature of orbital speed and the impact it has on the effects of how we feels the Earth’s gravity, nor COULD I get my head around that this “micro-gravity” is about 90% (according to xkcd) of the Earth’s actual pull, which always led me to ask, “then how can they be floating at all?!”

Until now.

Even when I finished reading the article, I got a better idea of orbital speed, and understood it as it related to the Earth, but not to the scenario posed by the original poster. We were FREE of the Earth’s orbit, so why not wait in the depths of Space and wait for Mars (there’s a HUGE hint—MASSIVE hint—in both that statement AND this hint-of-a-hint! :D).

So after reading it, I had a little understanding, and maybe for you, it’s much easier for you to grasp it. But it was while I was typing this post and going to and fro the image above that I had the “OH, YEAH!” moment. Then I started thinking about the micro-gravity equaling 90% of the Earth’s full gravitation effect and started relating the motion of the ISS to that of an aircraft. Why is there no orbital speed effect and micro-gravity/apparent weightlessness there? (because it’s aerodynamics and nothing to do with maintaining an orbit, well, it kinda is an orbit, but aided by the volume of air passing around the wing—aerodynamics).

And somewhere in this post I did have an epiphany and it all DID make sense. And Beska was right.

I started this post as an email to a friend, and the reason I started it was to point out the song fact right at the end of the XKCD article, and to spread an interesting topic. But now, it’s more about the fact that I learned something very interesting tonight, something I didn’t know, something I will never use, but something that is still interesting just the same.

Oh, and just in case you want to read the XKCD article (you may as well, it is very enlightening), feel free to come back and checkout the “Trip to Mars” route map and look at that BIG yellow dot in the middle :D

XKCD article on Orbital Speed

Stack Exchange question: Why don’t we take the shortest route to Mars

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