This idea has been kicked around in pieces before, though I think this particular combination may be unique.
Mount a Roton blade system on top of the shroud of a standard launch vehicle. Power it up before launch such that it is supplying perhaps 20% of the total thrust at sea level. At the 10/1 Isp gain early on, this would be a serious enhancement to the vehicle performance.
If there is a launch vehicle problem, the payload and shroud are detached to be accelerated out of harms way by the already thrusting Roton unit using it as an LES system.
The Isp gain will fade as it climbs out until in vacuum the tip rockets are at perhaps Isp 300 which is less performance than the main propulsion system. When the shroud is ready for detachment, it is separated from the launch vehicle and pulled away by the Roton unit.
The Roton unit is used to control the shroud reentry and to guide it to a recovery vessel where it auto rotates to a landing.
johnhare
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Care to do the maths on how big those blades would need to be to provide 20% of the thrust of an F9?
I can handle the idea of a Roton-inspired payload cover recovery system, but it ain’t gonna do a thing during launch except add mass.
[Aside: Every time Roton comes up, I still have to remind myself that they not only test flew the ridiculous thing, they did manned test flights.]
You and your inconvenient facts. I get about 150 foot diameter with a high disk loading. Not trivial. And likely not compatible with other launch vehicles either. I came up with 20% thinking in terms of sizing the tip rockets large enough to pull a payload clear if necessary in near vacuum conditions.
I think a helicopter-style liftoff is only interesting for tiny launch vehicles. For anything bigger, just using more engines and brute-forcing the problem is much simpler and reliable.
My point is that on anything larger than the ATV, rocket engine mass compared to dry mass is small enough to justify adding more engines.
I share Paul451’s view that Roton’s landing system might be an interesting option, but it must be compared to re-startable engines for a powered landing.