Free returns

Let's hit up The New World on Mars some more. Chapter 3, on how to get there.

How To Live On Mars proferred two zero-energy transfers (plus the "nukey ride" - maybe NERVA, maybe the molten-salt flying Chernobyl, doesn't matter). The two transfers were: the "stinky cycler", and "riding the freight" that is, Hohmann. New World likewise doesn't care to shave traveltime with extra Starships much less nukes.

New World's "six-month" journey corresponds to the 180-plus days of InSight. That's the (semi)Hohmann; that's the freight train. This will return to Earth's 1 AU orbit, yes. But it does not return to Earth. Earth is going to be elsewhere. Once the freight is distributed, whatever is left (like shielding and spent Starships) is going to end up in some fifteenth of an Earth orbit. This route is, I vaguely recall, the VISIT trajectory.

Aldrin's free-return as actually shows up near Earth is not the six-month halfway Hohmann. Aldrin actually takes less time to (flyby) Mars: 146 days per Hop David so five months. Although, if an Apollo-13 is happening, it's quite a bit longer to get to its own aphelion and then all the way back to perihelion which is Earth(ish). Other "cyclers" are possible, some perhaps worthy of a permanent back-and-forth; Zubrin was possibly thinking of these in 2008.

Right now, Zubrin is confusing six-month halfHohmann, which is one-way freight; with the five-month Aldrin, which I deem best for passengers in case of disaster. Thus retarding his latest book a step behind where he was, in 2008; several steps - a giant leap, if you will - behind Gurrea in 2022. (I'm tempted to importune Zubrin for a free return... of his book. He's wrong on clothing as noted. On immigration too.)

In this spirit of 2008 reminder, recall that the five-month Aldrin as a subset of "cycler" requires more oomph to get started, and needs extra propellant - and shuttle - at the destination to inject those passengers into Martian orbit. Plus: once back at Earth, Earth needs some way to slow all the returned material so to catch it all. Zubrin needs maths on all these.

Alternatively: Zubrin needs infrastructure, like a base on Deimos as can do rescue and cargo-transfer. Frankly he needs this anyway. Asteroid and lunar bases are further upstream of necessary tech, before settling Mars. And once we have asteroid bases what do we still need Mars for? Prison?