The Roton, developed by Rotary Rocket Company, was an attempt at SSTO using a helicopter rotor for takeoff and landing. This particular concept was cone-shaped with a tip-jet rotor on top and an aerospike at the bottom. Unfortunately, they never managed to raise enough money for a prototype beyond the initial helicopter propulsion, let alone full SSTO.

In theory, there are advantages to this system:

  • The helicopter "first stage" can get the rocket out of the thick atmosphere and its problems (unoptimised engines, aerodynamic constraints)
  • The helicopter part can be used to slow down the craft and control its landing, instead of using extra mass for parachutes or fuel for a suicide burn

On the other hand, the thing does have a goofy Wunderwaffe look that make you wonder who the hell thought that could have been a good idea.

Beyond the failure (or the looks) of this particular project, could such a concept, using a helicopter rotor as a first stage and for landing, be made to work with decent performances compared to conventional rockets?

  • $\begingroup$ Are you asking specifically if it would be workable as an SSTO, or whether rotor-assisted launch and landing for the first stage of a 2STO might be worthwhile? $\endgroup$ Nov 14 '18 at 18:13
  • $\begingroup$ @RussellBorogove Ideally as a SSTO, but not necessarily. If reuse is a concern, a 2STO with two reusable stages may also work, after all. $\endgroup$
    – Eth
    Nov 14 '18 at 18:33

I think you misunderstand the nature of the helicopter blades.

While they did intend to land under aerodynamic lift on the blades at the very end of the landing path, for takeoff they actually wanted to use the blades as centrifugal pumps.

One of the really hard part of rocket engines is the need to build a pump that can move fuel and oxidizer at the amazingly high rate an engine needs to consume it.

For the SSME, it is said:

The HPOTP consists of two single-stage centrifugal pumps (a main pump and a preburner pump) mounted on a common shaft and driven by a two-stage, hot-gas turbine. The main pump boosts the liquid oxygen's pressure from 2.9 to 30 MPa (420 to 4,350 psi) while operating at approximately 28,120 rpm, giving a power output of 23,260 hp (17.34 MW)

That is a truly astonishing amount of power in a very small space all things considered.

For the Roton, using the helicopter blades, with engines at the tips you spin them up slowly, and they can suck the fuel through centrifugal, or centripetal (I forget which is which, since I have not done Physics in decades) force, and you get a high powered turbo pump almost as a side effect.

That was the original design, as I understood it.

Later they switched to a different engine design, still rotary, but this time on a disk on the bottom of the vehicle.

Then finally they switched to some other engine as they ran out of funds to develop their unique engine. Their plan was to get to orbit, with the temporary engine then finish their engine.

  • $\begingroup$ Agreed, that was a truly bizarre engine design and I remember eagerly watching to see if they would ever build the thing. $\endgroup$ Nov 15 '18 at 2:12
  • $\begingroup$ Wow, so this wasn't a helicopter-rocket hybrid but a helicopter-turboprop-rocket hybrid. Could something like that have possibly worked as advertised? $\endgroup$
    – Eth
    Nov 16 '18 at 19:08
  • $\begingroup$ They thought so at first. $\endgroup$
    – geoffc
    Nov 16 '18 at 19:11

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