If the Moon or Mars will we . . .

Message text written by INTERNET:ssi_list@...
>It would still start from near to zero
speed, but having 10km less to travel should allow a considerable save in
the amount of fuel needed,<

Speed is what you need. The distance makes essentially no difference.
There is an advantage due to lower air pressure. For example the space
shuttle main engines have a specific impulse of about 370 seconds at sea
level, but over 450 seconds in vacuum. You would have to trade this
against the complications of the balloon launch to see if it is worthwhile.

Lynn