Planet to planet

Gary "XRM" Johnson has words about planet-to-planet propulsion. With a focus on Mars/Earth but also applicable to Venus/Earth.

He boils it down to I_Sp. If I_Sp is chemical - under 500 [N/N] seconds - the fuel will likely all be used by the time you get there. Note that high-thrust solutions like entering/leaving Hohmann tend to the low I_Sp, although overall Hohmann will net you the least overall δV. This means you'll need to make the fuel at the destination. Energy too, I might add. Deimos is looking VERY good here!

Matters get better with 1974 NERVA, 800 s. I don't know that we got NERVA (legally) but we're getting close-enough to that with our HALEU options. 1300 s also exists but, as Johnson points out, these are low-thrust. Honestly I'd leave that to the outer system.

Also from the Earth side, he'll say (later) that propellant should be provided from our own Deimos, namely Luna.

What this means for Venus colonists is that, er, there's not a lot of propellant to be had there. But if you've been reading here early 2011 you knew that. I was hoping to net hydrogen from the planet's coma.