Roton SSTO
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The Roton was to be a single stage to orbit launch fully reusable manned spacecraft, championed by Gary Hudson with technical input from Bevin McKinney and was to be built by the startup Rotary Rocket, Inc (rotaryrocket.com).
It evolved through several guises.
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Helicopter to orbit
The initial design was an unusual helicopter design- the vehicle had rocket engines on the end of a spinning helicopter blades external to the main body. The idea was to use aerodynamic lift whilst in the atmosphere, and after leaving the atmosphere, to use the rocket engines pointing almost straight-down to reach orbital velocity in the conventional way; albeit with what amounted to an external turbopump.
Calculations showed that the helicopter blades modestly increased the Isp by about 20-30 seconds, which essentially carried the blades into orbit 'for free'.
So, no gain. However, during landing, the blades could be used to soft land the vehicle, and this meant that the landing system was mostly free.
So, a company was started to employ this technology to launch small telecommunications satellites into space. However, soon after the company was formed, the telecommunications market crashed; and the company scrambled to redesign the vehicle for other types of payloads.
Helicopter from orbit
The problem was that the target market required heavier payloads. For the helicopter-to-orbit to work, a very large swept area is needed, and this pushed the liftoff rotors outside the commercially available sizes, so they had to be dropped.
The redesigned Roton was a cone-shaped launch vehicle, with a helicopter rotor stuck on top for use during landing. The projected price to orbit of this design was to be $1000 per kg of payload; less than 1/10 of the current launch price; although payload was limited to a relatively modest 3 tonnes.
The company intended to use a unique rotating annular aerospike engine; the engine and base of the launch vehicle would spin at high speed to pump fuel and oxidizer to the rim by centrifugal force. The entire base of the vehicle was designed to act as a truncated nozzle; and later in the flight double as a reentry shield. The engine had a projected ISP of ~355 seconds (3.5 kN·s/kg); which is very high for a LOX/Kerosene engine; and a thrust:weight ratio of 150; which is extremely light.
The vehicle was also unique in planning to use its helicopter-style rotors for landing, rather than wings or parachutes; this concept allows giving controlled landings (unlike parachutes), whilst being 1/5 the weight or less of fixed wings. The rotor blades were to be powered by peroxide tip rockets to permit pinpoint landings. Worryingly, the rotor blades were to be deployed before reentry and some questions were raised about whether the blades would still be present at landing.
Reentry was to be achieved utilising the base as a water cooled reentry shield. This is potentially a good way to survive reentry; particularly for a very lightweight vehicle such as the Roton was to have to been.
The company also designed and pressure-tested a unique exceptionally lightweight, and yet strong, composite LOX tank, which survived a test plan which involved being pressure cycled and ultimately being deliberately shot to test its ignition sensitivity. This composite construction was actually a world first.
A full size, 64 foot (20 m) tall, atmospheric test vehicle was built which successfully flew three test flights in 1999, proving the rocket-rotor concept, but in early 2001, the venture ran out of funds and closed down.
Author Tom Clancy provided some financial support to the company among many others.
The timing of the venture was unfortunate, the Iridium fiasco was coming to a head, and the whole space industry was feeling the pinch. Engine development ceased in 2000 (reportedly 2 weeks before a full scale test was due), and ultimately the vehicle did not attract sufficient funding, failed to secure launch contracts and Rotary Rocket was forced to close.
Some of the engineers that worked there have since set up other rocketry ventures, notably XCOR Aerospace. The atmospheric test vehicle was intended to reside in a helicopter museum near San Diego, California; however an attempt to move it there via helicopter failed due to aerodynamic problems and it currently still resides in Mojave.
Skepticism
The Roton had numerous developmental difficulties, and the CEO, Gary Hudson, although he was a veteran of 5 failed startups prior to Rotary; he did have significant aerospace development experience.
Whether the full-up vehicle would have worked is anyone's guess. However the company had backup plans for boosters in case the vehicle didn't quite have enough performance to reach orbit; and given this, there's no reason at all that it couldn't have successfully launched payloads to orbit.
The equipment Rotary did produce essentially worked, the ATV flew, and a composite propellant tank survived a full test program; which is more than can be said for the composite tank produced by the conventional aerospace community for the X-33 for two orders of magnitude greater cost.
Nevertherless, the Roton was never considered seriously by the aerospace community.
External links
- Roton test vehicle on display at Classic Rotors Museum (http://www.rotors.org/roton/roton.htm)
- Roton article (http://www.astronautix.com/craft/roton.htm) at Encyclopedia Astronautica
- Wired magazine article on Roton (http://www.wired.com/wired/archive/4.05/roton.html)
- Space.com on test flights (http://www.space.com/missionlaunches/launches/roton_thirdflight.html)
- Space.com on helicopter museum trip (http://www.space.com/astronotes/astronotes_may4-may17_03.html)