“The first stage burns out after the first 70 km”. There’s very little atmosphere there, so it would effectively free fall for a while first, and then would have to start gliding.
You can’t rapidly get from a fast free fall (almost vertical) to gliding (almost horizontal), or your wings will break of. That means you either need something to rapidly (but not too rapidly) decrease vertical speed, or you need lots of height to make a slow turn (this thing will be falling at thousands of km/hour before it reaches denser atmosphere). I guess “lots of height” is a bit more than 70km for realistically strong wings.
So, you need something to decrease vertical speed. A parachute is the best solution we have for that. If you have that, why add wings, too?
If you launch to orbit, there is a gliding solution that will work: wait for atmospheric drag to slowly bring the booster down to denser atmosphere, but these boosters don’t get into orbit, and even if they did, it would take way too long.
> I guess “lots of height” is a bit more than 70km for realistically strong wings.
A drop test of Dream Chaser prototype was done a few years ago from a helicopter, definitely not 70 km of altitude. The prototype successfully landed onto a landing strip.
I maybe mistaken, but I don’t see how that’s relevant. Dream chaser is designed to return from orbit. These boosters won’t reach anything like orbit, and will have insufficient horizontal speed to start gliding.
Also, if you want to glide these boosters to earth, the challenge is to get them into more dense atmosphere with a low vertical speed. Once you’re there, it’s ‘easy’.
A test dropping them from a helicopter doesn’t test the ability to do that at all; it tests the ability to land after you’ve done that.
That's completely over-engineered. You just need inflatable floats and then the helicopter can pick the booster up within minutes to prevent salt water corrosion.
