Type: demonstrator for SSTO launch vehicle
Powerplant: 1 x rotary RocketJet™ aerospike engine
and several Derived Fastrac Engines
Designed by: Rotary Rocket Company, Redwood City, California
Drawing from the general principles of that concept, Hudson and his newly-formed company aimed for the Roton to provide unparalleled operability, reliability, and safety while providing single-stage-to-orbit capability. To achieve the goal of an SSTO space vehicle required both high performance rocket engines and a lightweight vehicle structure to contain propellants and cargo. Several comsat constellation projects in low earth orbit began around this time and they promised to provide a solid market for a low cost vehicle that could carry replacement satellites to orbit. Excitement grew that finally low cost access to space was at hand.
Getting to orbit was only part of the challenge, however. The other key aspect of a reusable vehicle was return from space. The Roton was to accomplish this using conventional thermal protection to moderate the heat of reentry into the earth's atmosphere. The Roton would also utilize a deployable helicopter rotor to provide braking, stability and soft landing capability. The natural autorotation of the external rotors deployed during the return flight would enable a slow, controlled, descent to a soft precision landing. This would make the Roton capable of safely returning itself and its cargo to the ground at any point in flight, a technology dating back several decades. Vertical takeoff and landing also minimized land overflight and the effect of sonic booms, and needed only a small site for flight operations. The Roton would also land without any fuel on-board, enhancing safety. Reusability also ensured that individual vehicles could be flight tested repeatedly. Consequently, prior to achieving operational status, the Roton was to be put through more flight tests than many expendable rockets encounter in 10 years of operation.
High engine performance was achieved through the breakthrough technology of the RocketJet™ rotary aerospike engine. This engine featured an innovative blending of jet and rocket engine technology. RocketJet™ technology was proprietary to Rotary Rocket Company. The company's propulsion expertise was unique in the industry and ensured the propulsion system was exactly tuned to the vehicle, resulting in both high efficiency and high performance. This also gave the company total control over the key strategic business issues of engine cost and availability. The RocketJet™ engine automatically compensated for the decrease in atmospheric density as the vehicle ascended to orbit, maintaining outstanding engine efficiency and high vehicle performance. The engine rotated about the Roton's longitudinal axis, generating the centrifugal force necessary for pumping the propellants at high pressure to the engine's banks of multiple combustion chambers. This eliminated the need for complex and fragile turbo pumps as used in the Space Shuttle and most existing rockets. The engine would burn conventional jet fuel and liquid oxygen, and at take-off the Roton would carry less fuel than conventional transport aircraft. These propellants also produced an exhaust that was virtually benign to the environment. Tests of this innovative, patent-pending, propulsion system were conducted.
Powered by its rotary RocketJet™ aerospike engine burning liquid oxygen and jet fuel, the Roton was to deliver cargo to low earth orbit and return for reuse without discarding or expending any component. As with a conventional jet aircraft, only liquid propellant was consumed during a flight, and no refurbishment was required to prepare the vehicle for another flight. If a problem developed during flight the Roton could, in most instances, terminate the flight and return safely to the ground. A fleet of Rotons would provide fast, reliable and economical service in the same manner as any of today's airfreight companies, fundamentally changing the economics of carrying cargo to space. This contrasted strongly with the current industry practice of simply throwing away an expensive launch vehicle each flight.
A lightweight vehicle structure was obtained though the extensive use of sophisticated composite materials. These materials had already been used successfully in the DC-X program and in dozens of advanced aircraft, many of which (including the McDonnell-Douglas DC-X aeroshell) had been built by Scaled Composites, the integrating contractor for the Roton. Scaled was responsible for building the Roton's composite airframe, propellant tanks, cargo bay fairing, rotor, and thrust structure/heat shield. Rutan even named the Roton "the most important project ever to come in the doors at Scaled Composites."
"The third and last flight occurred on October 12, 1999. The ATV climbed to 75 feet and accelerated while traveling 4,300 feet down Mojave's main runway. We were shook by a thundering airframe vibration of about two Gs while in forward flight. The vibration disappeared in hover. We later discovered it was caused by the impingement of the rotor wake, which was energized by the rotor tip rocket exhaust, onto the airframe. The vibration caused several airframe components to break loose, including the propellant catalyst tank, which was found hanging by its plumbing lines. If the catalyst plumbing had failed, the tip rockets would have stopped, and the ATV would likely have crashed." — Marti Sarigul-Klijn, Cdr., USN (ret.)
Unfortunately, when Iridium and GlobalStar went bankrupt, investment in Rotary and several other startup RLV companies disappeared and Rotary closed in 2000. However, before the company shut down, it did manage to test the rotor landing system with three low altitude flights of the full scale ATV (Atmospheric Test Vehicle). Head of Rotary Rocket Gary C. Hudson left the company earlier to work at HMX and to pursue other interests. The Mojave facility was closed after an auction of most of its contents. Rights to the various technologies, e.g. composite fuel tanks, that were developed by the company were sold to XCOR, a company founded by several former Rotary employees.
the ATV was roughly comparable to the MDA DC-X in that it was a landing system technology demonstrator. However, it differed from the DC-X in that on completion of the ATV test flights, the Roton vehicle low speed aerodynamics and control laws would have been measured in full scale, rather than the subscale of the DC-X and the X-33. The ATV also tested the manufacturing methods for the liquid oxygen and kerosene tanks for the orbital Roton vehicle. The Roton was to enter base first, so the ATV did not need to perform comparable tests to the rotation maneuver which was necessary for the DC-X to demonstrate for the operational Delta Clipper side entry profile. The ATV was only a big, hydrogen-peroxide powered helicopter, but it demonstrated a level of commitment and follow-through toward an operational SSTO vehicle in its structures and configuration that the DC-X lacked.
Population: 1 [N990RR]
Following specs for unbuilt Roton C-9 PTV (Propulsion Test Vehicles)
Gary Hudson on the Roton/ATV debacle
If you were given $300 million today to build a RLV, would you still
go with the basic Roton approach?