https://www.youtube.com/watch?v=UqrVjSfMzMM

https://www.youtube.com/watch?v=3CR5y8qZf0Y


First stage empty is 234,000 lbs,
Second stage empty is 82,000 lbs
Third stage empty is 30,000 lbs.

So, a quad rotor type arrangement - but with throttling rocket engines - and gimbals - on each corner - with BE-4s with a range of thrust from 550,000 lbs to 20,000 lbs - we have 2.2 million lbs to 80,000 lbs.

With a propellant fraction of 0.6 and structure fraction of 0.2 - and payload up to 0.2 we have a vehicle that is capable of two gee acceleration - fully fuelled - 1,170,000 lbs not to exceed weight 234,000 lbs vehicle structure - 234,000 lbs payload weight - 702,000 lbs propellant. This has a five minute hover time. Now terminal velocity of a largely empty tank is about half sound speed. About 384 mph (620 kph, 172 m/sec) So, two minutes at this speed covers 20.6 km (12.8 miles).

A GPS transponder on the vehicle, tracks the vehicle until it is 12 miles above the landing threshold. A platform launches and meets the descending booster mid flight, clamps the hold down clamps at the base of the rocket, and lands the rocket and platform gently - all in a space of four minutes. The cost? Less than $48,000 in propellants!

This greatly simplifies recovery and minimises mass on board the rocket and maximises payload to orbit!

Though this is rather cool! I must admit.

https://www.youtube.com/watch?v=9pillaOxGCo


A 110,000 lbf engine - throttable back to 4,000 lbf - is more scalable

From four of the large engines to twenty of the smaller engines - for the recovery of the big booster. Eight engines in a smaller platform to recover the second stage. Four engines to recover the third stage. Or merely reuse the smaller platform for the third stage as well.

Given the advanced development of the first stage recovery - its probably best not to change it at this point. However, a smaller platform using eight of the 110,000 lbf engines - two on each corner - to zoom up and recover the second and third stages - might be something to consider as a continuing development programme.

It could also recover capsules - and payloads from orbit - or returning from a failed launch.