Re: how could you travel to callisto using today's technology?

Hi Jen!

A good place to start finding Callisto information is at the Nine Planets 
website:

 http://www.seds.org/nineplanets/nineplanets/callisto.html

Humans have, of course, already sent probes to study Callisto.  The last 
of these, Galileo, is still in orbit around Jupiter and has produced 
enormous amounts of new data on that planet and its satellites.

So we certainly have the technology to launch craft to Jovian orbit and 
conduct robot operations there. However, your question seems to suggest 
whether we could send people to study Callisto.

Using today's technology, the answer would be a borderline "yes": but it 
would be an extraordinarily difficult and costly venture, difficult if 
not impossible to "sell" to politicians or the public. 

To date, no humans have ever travelled beyond 400 000 km from the Earth - 
and Callisto is 1500 times further away. Three cosmonauts survived over a 
year in low Earth orbit, with regular supply craft supporting their 
needs, but Galileo took nearly six years to reach Jupiter (having used 
flybys of Venus and the Earth, twice, to boost its speed and reduce its 
need for propellant) and Galileo is, of course, a one-way trip: there are 
no plans to bring it home.

No doubt any potential space travellers to Callisto would prefer to come 
back! In practical terms this means that they would have to carry return 
propellant with them, plus all their life support and logistical needs 
for at least twelve years. Solar flares and the immense radiation fields 
of Jupiter would require heavyweight shielding, and scientists have 
little evidence on how weightlessness would affect the body over a decade 
or more. 

Galileo masses just over two tonnes in Jupiter orbit, and was launched 
with a rocket stage from the space shuttle Atlantis in 1989. Any manned 
craft would necessarily mass hundreds of times more than this, and would 
require multiple shuttle launches to assemble the craft in Earth orbit.

So the answer is yes, it would be technically feasible to send people to 
Callisto, using today's technology, but it would be extremely difficult. 

Finally, there's other "real estate" near by that would help prepare 
explorers for long range journeys like this: long-duration bases on the 
Moon, trips to Mars and near-Earth asteroids would be essential to gain 
experience and the technologies needed for future deep space explorations.

Regards,

Andy Goddard