On Tue, Jan 30, 2018 at 01:24:13PM +1300, Rupert Boleyn wrote:
> On 30Jan2018 1314, Thomas Jones-Low wrote:
> >http://i.imgur.com/AAGJvD1.png
>
> The low orbit to Venus surface requirement looks off - it's gas
> giant level.

Venus does have a very thick atmosphere.  Reading back over the Reddit
thread where the calculation was done, the assumption was using the
Goddard solution from the surface with reasonable drag parameters.
The problem is that the lower levels of Venus's atmosphere have
densities more comparable to soup than to the air we breathe, and
consequently very strong drag at even modest speeds.

I'd take it with a big boulder of salt, because if we ever do get
something to take off from Venus's surface, we certainly won't try to
get through the first 70 km or so with a conventional rocket.

The launch delta-V's for actual gas giants in the table were
calculated from the Earthlike density levels in their atmosphere.  If
their entries in the table used the same take off from "surface" using
a rocket like Venus, their delta-V's would be even more insane.

- Tim