It would not help much (going up is only about 15% of the effort of going to orbit, the rest is sideway acceleration) and it would add a lot of complexity and cost.
Define "more efficient"? You would need to build new storage system for the lifting gas and add a lot of systems to manage it. On the other end you can just make the existing tanks slightly bigger and put a bit more fuel in them...
Efficient as in reducing the overall weight of a rocket to overcome materials physical limits. Am I wrong in thinking that bigger isn’t always better, the same way insects do not reciprocate the same damage as an elephant from falling from relative heights. I imagine though that the balloons, no matter the capacity of weight they would negate, would need to be detached within the first minute once the acceleration of the rocket out paced their natural lift. Again, minutely more efficient, but not worth the engineering/cost effectiveness.
electric_ionland t1_iv1edkk wrote
It would not help much (going up is only about 15% of the effort of going to orbit, the rest is sideway acceleration) and it would add a lot of complexity and cost.