In typical rockoon a balloon is the lifting body to the upper atmosphere where a rocket is released and ignited. But I would like to ask about a variation to launch small payloads to space.
Instead of attaching the rocket to some kind of platform pointing upwards, to attach rocket to seaplane pointing downwards. Release the rocket attached to seaplane and let it fall till it reaches speed close to 500m/s. Let's assume that rocket is released at 40km and reaches 500m/s at approximately 10km height. Before it hits the denser layer of atmosphere change the direction and steer the rocket upwards by seaplane. Detach rocket from seaplane and ignite rocket. Use atmospheric drag to slow down seaplane and safely land on water. For safety reason let's assume that balloon is filed with helium and lifted from ship offshore with enough clearance to avoid crash issues.
Is this ever tried in practice, or I am missing something which would make this impossible to realize or there are no benefits? If it was tried what were the disadvantages which cause it impractical?
From my point of view this variation provides several advantages to traditional rockoon:
- Starting rocket engine at 500m/s is much efficient than at 0 m/s. Eventually rocket will go much higher, maybe even SSTO is possible with hydlolox. At least you can downgrade tree stage rocket to two stage rocket for the same height.
- You can steer rocket wherever desired with seaplane. Traditional rockoon suffers from drift because ballon cannot be steered, leading to launching rocket in undesired direction.
- Maneuvering is done before hitting denser layers of atmosphere (90% of atmosphere is till 10km) therefore atmospheric drag for rocket should not be a significant problem. Seaplane with supersonic design should not have an issue moving through denser layers of atmosphere.
- Most expensive part - seaplane is 100% reusable and can be made to land by autopilot on water.