"Allen W. McDonnell" wrote in
:
Why should mariner 10 in 1973 require 1 Venus flyby to set up 3
Mercury flyby's and the 2004 Messenger mission require one Earth
flyby, 2 Venus flyby's and 3 Mercury flyby's before it actually goes
into orbit in 2011?
Mariner 10 did fly-by's of mercury, Messenger will enter orbit. Orbit
requires plenty more delta-v than flyby only.

Getting to Mercury is less energy intensive than
getting to Jupiter.

Nope.
Jupiter is so much easier to reach that it is actually *cheaper* in delta-v
to fly out to jupiter and slingshot back to reach Mercury than to do a
direct transfer from earth to Mercury. The trip via Jupiter would just take
a *very* long time.

NO planet is as hard to reach as Mercury.

Add to this the non-trivial complexity of having your spacecraft withstand
over several years the solar intensity which is more than 11 times that we
get on Earth.

Now factor in a minuscule budget that only pays for a delta-II launch.
Without the multiple slingshot-flyby's, the launch would have demanded a
Delta-IVH or possibly even something more.

Its a miracle the mission is doable at all.