Error in book? - Red Mars (Kim Stanley Robinson)

[stijnovic]

So I'm reading this book and really enjoying it! It's about the colonization of Mars, very detailed and scientific and quite plausible. Also the characters seem very convincing and for a change the story does not revolve around action. It's really cool to read and understand the jargon that KSP taught me.

But... to me it seems the terms apogee/apoapsis and periapsis are switched. Here's an example right after aerobraking for Mars orbital insertion:

Twelve weightless hours later their new course led them to a

periapsis thirty-five thousand kilometers

from Mars. There they fired the main rockets for a brief thrust, increasing their speed by about a hundred kilometers an hour; after that they were pulled toward Mars again, carving an ellipse that would bring them back to within

five hundred kilometers

of the surface. They were in martian orbit.

Each elliptical orbit of the planet took around a day. Over the next two months, the computers would control burns that would gradually circularize their course just inside the orbit of Phobos. But the landing parties were going to descend to the surface well before that, while

apogee

was so close.

They moved the heat shields back to their storage positions, and went inside the bubble dome to have a look.

During

apogee

Mars filled most of the sky, as if they flew over it in a high jet.

Seems to me that perigee should be close to the planet and apogee should be far away from the planet, or?

[RogueMason]

Well, it should be apoapsis, seeing as apogee applies to just Earth. The rest of it, however, seems alright. If you go and get an encounter with Mun in KSP (or any planet or moon, for that matter), then your fly-by trajectory will have one node; periapsis. The author stated this part fine.

They also never expressed whether the five hundred kilometres part was apoapsis or psoriasis, but it's safe to assume that they meant periapsis here.

The 'apoapsis is so close' bit probably just means that the landers de-orbited at apoapsis. Makes sense, seeing as it wouldn't tale much delta-v to de-orbit at this point as opposed to at the periapsis.

The final bit... Hmm, well that does look wrong. Maybe they meant to say it was high in the sky instead of filling it? Hard to say, really.

[stijnovic]

Thanks for you reply, but it still seems totally wrong to me.

...your fly-by trajectory will have one node; periapsis...

True, but this is 12 hours after the aerobraking, so at this point you are already in orbit (although your periapsis is in atmosphere or lower).

...They also never expressed whether the five hundred kilometres part was apoapsis or psoriasis, but it's safe to assume that they meant periapsis here...

It is also mentioned that after the burn, they get closer to Mars again. How I understand it, they do a burn (increase speed) at apoapsis to raise the periapsis above the atmosphere.

Psoriasis?

...The 'apoapsis is so close' bit probably just means that the landers de-orbited at apoapsis. Makes sense, seeing as it wouldn't tale much delta-v to de-orbit at this point as opposed to at the periapsis...

But do they raise the apoapsis then? That seems inefficient to do after aerobraking?

[Awaras]

No, Stijnovic is right. They perform an aerobraking maneuver in Mars' atmosphere, and then go UP to a 'periapsis' of 35000 km at which point they burn to raise their real periapsis to about 500 km from the surface.

The funny thing is that in MY version of the book, the final quoted passages state 'while PERIGEE was so close' and 'During PERIGEE Mars filled most of the sky'. So they corrected that at some point but not the first passages....

*edit* Well, "corrected", since it should still technically say periapsis, not perigee...

Edited April 24, 2014 by Awaras

[Javster]

There's a scene in a book I read a while ago which I'd like to re-read to evaluate the realism...

[Capt. Hunt]

Actually, it could still be planet specific, but it should be Periareion/Apoareion.

[stijnovic]

Haha, ok good, I thought I was getting crazy.

But it's funny, cause now I see a bit further in the book where Marsion seasons are explained:

This simple situation was complicated by the eccentricity of the martian orbit, which is extreme by terran standards, for at

perhelion Mars is about forty-three million kilometers closer to the sun than it is at aphelion

, and thus receiving about 45% more sunlight. This fluctuation makes the southern and northern seasons quite unequal. Perihelion arrives every year at Ls = 250°, late in the southern spring; so southern springs and summers are much hotter than northern springs and summers, with peak temperatures as much as thirty degrees higher. Southern autumns and winters are colder, however, occurring as they do near aphelion; so much colder that the southern polar cap is mostly carbon dioxide, while the northern one is mostly water ice.

There it seems to be correct, both the apo/peri-part and the helion/gee/areion-part.

[RogueMason]

True, but this is 12 hours after the aerobraking, so at this point you are already in orbit (although your periapsis is in atmosphere or lower).

It is also mentioned that after the burn, they get closer to Mars again. How I understand it, they do a burn (increase speed) at apoapsis to raise the periapsis above the atmosphere.

I could have used some context there to help out. I didn't know they'd aerobraked, you see.

Psoriasis?

Damn autocorrect kept flinging that word out every time I typed 'periapsis'. Obviously missed that one

Oh well, I tried to make sense of something that was never to be made sense of.