1. Introduction
    1. Physical Description
    2. Operational Details
    3. Comparison with Other Interface Vehicles
    4. Typical Uses
  2. Flame Spiral Industries
    1. Flame Spiral Industries in 2300AD
    2. Current FSI Roton Models
  3. Design Notes


The Roton is a class of vertical take off and landing (VTOL) interface vehicle. Unlike other interface vehicles it is based upon a helicopter concept rather than an aeroplane or missile form. There have been many models of Roton since the first test flight in 2185 however they all have the same basic form.

Physical Description

The main body is cylindrical in form with an aerodynamic nose cone and a slightly flared base. The body contains the Roton's fuel, controls, avionics, cargo and passangers.

Scematic of the Roton

The Roton's propulsion is provided by a horizontal rotor (the number of blades depending upon the model) with each blade tipped with a rocket motor. In early models the rotor was attached to the main body using a slightly modified helicopter rotor assembly fixed to the top of the nose cone. In later models the blades are mounted on a magnetic bearing at the base of the nose cone. The main body of the Roton is prevented from rotating by redundant radial rocket motors, on some of the military variants of the Roton double counter rotating rotors are used which obviate the need for the radial rockets.

The flared base of the main body is an actively cooled heat shield (for re-entry) and de-facto emergency landing gear. The standard landing gear is normally recessed into the sides of the main body and, when deployed, projects over and below the base.

Operational Details

Roton in Hover/Ascent Mode During takeoff and atmospheric flight the rockets power the rotation of the rotor and the blades provide lift in the same manner as the blades on a helicopter. In vacuum the blades are tilted so that rockets are almost vertical to provide a thrust along the axis of the Roton. The slight angle is required to maintain the rotation of the rotor as this provides the means (centrifugal force) to pump the propellant from the tanks in the main fuselage, through the body of the blades, to the blade tip rockets. This arrangement means that the Roton does not require the expensive, heavy and difficult to maintain turbo pumps and pressurised fuel tanks found on other forms of interface vehicle.
Roton in re-entry Mode During re-entry, once injection maneourvers are completed, the rotor blades are raised up so that they trail behind the Roton as it enters the atmosphere base first. The heat shield produces a sufficiently large wake that the blades can freely rotate in a feathered configuration (ie edge on to the flow of air generating no lift). Once the Roton's speed has been reduced by aerobraking the angle of the rotor blades is gradually changed to provide braking. This operation requires no rocket power as the rotor is merely acting as a brake. Once the landing zone is reached the rockets are fired to provide additional control during final approach and landing. In actual fact no power is required to effect a soft landing as the Roton can land using the energy stored in the rotor to halt its decent as it touches down by flaring the blades to increase lift (this is the manoever known as autorotation in helicopters).

The Roton's ability to operate in a vaccuum and to land vertically also means that it is capable of landing and taking off from airless worlds (unlike equivalent space planes).

Roton Landed When not in operation the Roton's blades are normally folded down the side of the main body thereby greatly reducing the hanger requirements.
Roton in Orbital Storage When carried aboard interstellar or in-system vessels Rotons can either be stored in an internal hanger or an external cradle.

Comparison with Other Interface Vehicles

The Roton has many advantages over conventional interface vehicles but has one or two limitations that restrict its usefullness.


  • Simplified operation and maintenance due to centrifugal pumping of propellant and single loading axis.
  • Ability to land and take off vertically therefore requiring minimal planet-side facilities.
  • Ability to perform unpowered atmospheric landings in the event of main propulsion failure.
  • Ability to operate from vacuum and atmosphere worlds.
  • Small storage footprint.


  • Limited down range flight capability. Basically the Roton descends and ascends vertically and can only vary its landing location by approximately 70 km following re-entry.
  • Limited scaleability. The maximum size of a Roton is significantly less than that for a more conventional space plane due to the unique propulsion method. This is similar to the differences in size between conventional aeroplanes and helicopters.

    Typical Uses

    Roton's have had many uses over the years but have tended to gravitate to several more specialist niches rather than for more general interface use. Thus its unlikely that you would find a Roton on the Air France Paris to LEO run but you may find them tucked away in the corners of small airfields, or even just the corners of fields, all over human space.

    The Rotons uses have been determined by its special abilities particularly the ability to operate with only minimal support facilities. Some of the more common uses are as follows.

    Planetary Survey

    The Roton can land and take off (with the provision of suitable landing gear) from any relatively small area of flat firm ground. Consequently it makes an ideal survey vehiclefor the exploration of new planets. Its ability to operate in a vacuum also means that survey ships only need to carry a single interface vehicle to be able to operate on worlds both with and without an atmosphere.

    Corporate Interface Vehicle

    With no need for a long runway and no blast damage during takeoff or landing Rotons can operate from the same pads as tilt rotors and helicopters. Thus Rotons are often employed by corporations and individuals requiring fast convenient access to orbit without the need for airport checkins and drives to the international airport.

    Special Forces

    The Roton's ability to drop from orbit and land with little or no noise or light (the autorotating rotor is exceedingly quite when landing without rocket power) in unprepared locations makes it an idea special forces interface vehicle. Roton's are in service with the militaries of many nations (their use by the Legion Etranger during the Elysian revolt was particularly noteworthy) and specialised variants are produced under license by a number of aerospace companies.

    Marine Assault

    The Roton is frequently used as a second wave assault vessel following on after the the landing zone is secured by drop capsule troops. The ability to land without the need for a runway makes it ideal for the supply and reinforcement of the first wave forces (and equally as useful in extracting them should the need arise).

    Flame Spiral Industries

    FSI Logo

    Flame Spiral Industries (FSI) was founded in 2182 in Aukland, New Zealand by Naruma Partridge. Partridge, an Aerospace Engineering student from Aukland University, had used the Roton concept (originally proposed before the Twilight War in the US) as the design study for her Masters Degree. She was convinced that with recent French advances in composite construction that the Roton was now a practical possibility. What was more she had also managed to persuade several financial backers of the same thing.

    Within three years FSI had produced a prototype vehicle capable of sub orbital flight. With no indigenous space program FSI were forced to go abroad for orders for their new interface vehicle. Although the Roton could not compete head to head with conventional Scram Jet Shuttles its VTOL capabilities made it eminantly suitable for a number of specialist applications.

    FSI Rotons of a variety of designs soon found themsleves in service with many governments and organisations both in the Earth System and elsewhere. Although FSI are more than competant to produce civilian models they did not have the expertise (or access to modern military technology) to enter the military market. Consequently specialist military rotons were and are manufactured under license from FSI by the aeorspace companies of a number of major powers.

    Flame Spiral Industies in 2300AD

    Under construction.

    Current Flame Spiral Industies Rotons

    FSI currently produce three basic models of roton for civilian use. Customers can specify a wide range of options to tailor the basic models to their specific needs.

    Comparison of Three Roton Models

    Common Features

    All the FSI Roton models are delivered with the following features as standard. Model specific features are listed below with the relevant model descriptions (HL-90, ML-95 and E-99). In addition their are also a number of options which can either be specified when ordering or delivered as separate kits for retro fitting or upgrading.

  • Qualified to DSVAVI119 Standards (Civil Interface Vehicle Registration) under either manual or automatic control.
  • Standard aerospace traffic control (conforms to requirements of OQC LEO TCT 2284) transponder.
  • Comms equipment capable of interfacing with all common low orbit communication nets (conforms to requirements of OIN 450991-2287).
  • Cryogneic fuel storage and transfer fittings to OIN 23407-2262.
  • Standard paved landing apron landing gear struts with lightweight pads. Wheeled jacks to allow ground movement of Roton over a prepared surface. Note Roton can only be safely moved when empty of both fuel and cargo.
  • Internal power provided by closed circuit fuel cell.
  • Single set of general purpose blades supplied (suitable for use on all worlds with atmospheric pressures between 0.9 and 1.1 atmospheres and gravity between 0.9 and 1.1G).
  • Workstation for pilot and co-pilot/engineer.
  • Autopilot qualified for automatic landing at Class 2 or better airport and automatic docking to requirments of OQC LEO ADR 2293. All Rotons are therefore capable of operating autonomously between suitably rated destinations.
  • Life support for pilot and co-pilot/engineer of 24 hour duration.
  • Crew airlock to OIN 100998-2212 standard.
  • Unpressurised cargo bay.

    Note : Fuel and cargo masses in the following specifications are calculated using the SC Naval Architects rule of 1/6 total mass in fuel for single orbital flight from a 1.0G world. The numbers in brackets are real world values.

    FSR HL-90 : Heavy Lift

    The HL-90 is FSI's heavy lift vehicle capable of transporting over 300 tonnes of cargo or over 100 passengers (depending upon configuration) from a landing apron less than 100m in diameter to Low Planetary Orbit. The HL-90 is an extremely flexible vehicle capable of operation both in the core from well maintained facilities with high levels of support and on colony worlds where both the facilities and support are minimal.

    The HL-90 is the ideal vehicle for interstellar vessels requiring a significant interface capabiliity or for orbit terminals where access is required to landing zones other than major spaceports.

    Flame Spiral Industries FSR HL-90 Heavy Lift Roton
    Body DiameterMetres9.5
    No. of BladesMetres6
    Blade LengthMetres9.7
    Rotor DiameterMetres28.9
    Dry WeightTonnes10.9
    Fuel Mass (See Note)Tonnes63.2 (361.5)
    Cargo Mass (See Note)Tonnes304.9 (6.6)
    Reflected SignatureRadial (Rotor Folded)3
    Radial (Rotor Deployed)7
    Radiated Signature1

    FSR ML-95 : Medium Lift

    The ML-95 is FSI's most popular model. It gives the user the ability to quickly and efficiently transport both cargo and personnel from the base of the gravity well to low planetary orbit. The ML-95 is ideal for smaller (less than 100 tonnes) more valuable cargos or medium sized groups (50 or less) of passengers. As such it makes an excellent interface vehicle for interstellar vessels where docking space is limited or for regular ground/orbit routes with only limited demand.

    Flame Spiral Industries FSR ML-95 Medium Lift Roton
    Body DiameterMetres6.5
    No. of BladesMetres4
    Blade LengthMetres6.7
    Rotor DiameterMetres19.9
    Dry WeightTonnes5.0
    Fuel Mass (See Note)Tonnes20.0 (112.6)
    Cargo Mass (See Note)Tonnes94.8 (2.1)
    Reflected SignatureRadial (Rotor Folded)3
    Radial (Rotor Deployed)2
    Radiated Signature3

    FSR E-99 : Executive

    FSI's Executive Roton is designed with the busy corporate executive in mind. It provides direct access from planet side corporate facilities to orbital holdings for a small group of key staff or a high priority cargo. The low support requirements of the Roton design mean that the E-99 can be based at virtually any size of facility with day to day maintenance provided by the crew. Compared to other executive interface vehicles the E-99 requires only a 50m diameter landing pad and a basic cryogenic fuelling station rather than a major runway and full spaceport maintenance facilities.

    Flame Spiral Industries FSR E-99 Executive Roton
    Body DiameterMetres4.0
    No. of BladesMetres3
    Blade LengthMetres4.8
    Rotor DiameterMetres13.6
    Dry WeightTonnes2.2
    Fuel Mass (See Note)Tonnes5.6 (30.8)
    Cargo Mass (See Note)Tonnes25.8 (0.6)
    Reflected SignatureRadial (Rotor Folded)2
    Radial (Rotor Deployed)3
    Radiated Signature1


    The following options and kits represent only those most commonly requested by FSI's customers. FSI also provide more specialist kits for a variety of uses and have a number of partner organisations who can meet a wide range of requirements. Customers requiring any modifications not listed here should contact FSI for further information. Customers should note however that FSI do not supply military hardware or fittings for their Rotons. Military customers should contact one of FSI's licencees (list available on application) who produce a wide range of Rotons (either modified versions of FSI models or custom designs) for military applications.

    Construction Options

    The following options are normally only available if specified at the time of ordering as they require changes to the internal structure of the Roton during construction. Modifications which provide similar facilities can of course be retro fitted but the use of space and vehicle performance can be significantly degraded.

    Any of the construction options can be specified for later implementation in which case the appropriate changes are made to the Roton's structure but the additional equipment is not installed. Thus in the case of passenger facilities the required support points for the internal passenger cabin and interfaces to power supplies etc would be provided but the cabin itself would not be installed. In these cases the required modifications typically take up 5% of the final volume/mass requirement but allow the retro fitting of the option at some later date.

    Cargo & Passenger Facilities

    The basic FSI Roton's are supplied with an unpressurised cargo bay however it is possible to subdivide the cargo bay during construction to provide a combination of passenger accomodation and cargo space. Typically each additional passenger requires 2.5 tonnes of cargo space to provide full life support facilities and standard class accomodation. Increasing the luxury of the accomodation increases the space requirements (business class typically 3.0 tonnes, first class 3.5 tonnes per passenger). The precise requirements depend upon the required layout and any additional faclities required (eg. sanitary facilities, catering etc.).

    In the HL-90 and ML-95 models there is an additional 10 tonnes requirement for a separate passenger airlock (in the E-99 the passengers utilize the crew airlock).

    Pressurised Cargo Bay

    The cargo bay may be pressurised and fitted with a docking hatch to the OIN 101332-2266 standard. This provides a sealed entrance to the cargo bay but not an airlock facility.

    Both the pressurised and non pressurised versions of the cargo hatch use a combined hinge and slider mechanism that pushes the door cover out and away from the main body and then upwards so that the cover is held vertically above the cargo bay entrance. This allows easy access for docking tubes with the minimum of interference from the cover. In the pressurised version the pressure door itself slides vertically upwards within the door frame above the entrance.

    Control Options

    All FSI's Rotons are supplied with both manual and automatic controls. If specifeid when ordereing however Rotons which are only required to operate under a fully controlled aerospace regime can be supplied with automatic controls only resulting in an additional 7 tonnes of payload.

    Option Kits

    All option kits can be fitted to Rotons either during original production or later either by FSI or by the customers own maintenance personnel.

    Heavy Duty Landing Struts

    The standard Roton landing struts are designed for use on prepared landing zones and require a flat, hard and solid surface to function correctly. The heavy duty struts are designed to cope with less ideal conditions and are capable of supporting a fully loaded Roton on rough terrain and slopes of up to 10% when the appropriate landing feet are used.

    All Rotons are supplied with light weight landing pads designed to match the standard struts. FSI supply a number of alternative landing feet all of which require the use of heavy duty struts.

    Wheeled Landing Gear

    If landing on a prepared strip a Roton with wheeled landing gear can be rolled into position. Wheeled landing feet obviates the need for jacking the standard light weight pads thus reducing turn around times at busy airports. Note that the roton can only be safely rolled when empty of both fuel and cargo.

    Heavy Duty Landing Pads

    These pads are more robust and have larger surface areas than the standard light weight pads. They are also articulated to accomodate uneven landing surfaces. The use of heavy duty pads allows the Roton to land on unprepared landing sites provided that the ground is firm and the slope not more than 10% across the landing area. Heavy duty pads can be used with the standard wheeled jacks supplied with the Roton to allow ground movement.

    Disposable Inflatable Landing Pads

    In the event that the Roton is required to land on soft ground heavy duty landing pads can be fitted with inflatable pads which are inflated prior to touch down. The inflatable pads act to increase the load bearing area thus allowing the Roton to land on soft ground without sinking in. The pads are detached for lift off to prevent problems of ground adhesion and to avoid the need for complex recovery mechanisms.

    Extended Duration Life Support

    The standard Roton life support systems are simple low maintenance units albeit with a limited duration of 24 hours (48 hours on emergency settings). It is assumed that all life support functions will be provided by ground or obital facilities when the Roton is not in flight.

    If longer duration life support is required (if for instance no ground based facilities are available and the local atmosphere is unbreathable) additional recycling and storage systems can be fitted to extend life support duration to one month between servicing and re-supply.

    Internal Cargo Ramp

    Where limited ground facilities are available an internal cargo ramp can be used to allow foot and vehicle access to the Roton cargo bay. The ramp module is housed by fitting a false floor in the cargo bay to provide the space for the ramp and its associated machinery.

    When deployed the ramp can withstand loads of up to 100 tonnes and (assuming a flat landing ground) has a slope of 33%.

    Internal Cargo Handling

    The Roton cargo bay can be fitted with an electrically operated hoist and arm to facilitate the movement of cargo. The crane is fitted to the roof of the bay and allows the movement of cargo throughout the cargo space. The crane is remotely operated by a banksman within the cargo bay or by the flight engineet from the cockpit.

    The internal cargo handling cannot move cargo out of the bay but is capable of loading vehicles present in the bay. The crane's maximum safe working load is 20 tonnes.

    Cargo Airlock System (CAS)

    For Roton's fitted with a pressurised cargo bay it may often be necessary to transfer cargo to vessels or facilities lacking the appropriate docking equipment. To meet this eventuality FSI supply a versatile cargo airock system (CAS). The CAS consists of a robust, double skinned, fabric tunnel supported by a combination folding strut / inflatable frame. One end of tunnel is attached to the cargo hatch while the other is fitted with an airtight door.

    HL-90 with Airlock and Internal Ramp

    The CAS can be fitted either internally (within the cargo bay) or externally. If deployed externally in zero-G the CAS simply protrudes from the side of the Roton, on the ground the CAS can only be deployed externally in combination with the cargo ramp. The CAS can be deployed automatically in all three configurations provided that sufficient clear space and proper support is available. The CAS is sized to pass cargo up to 20% of total cargo capacity of the cargo bay but can be contracted to sizes down to 5%. If deployed within the cargo bay the CAS takes up the relevant cargo volume plus an additional 2% for the structure itself.

    The CAS consists of four square inflatable frames (with each side of each frame being capable of being inflated or deflated independently). The corners of each frame are linked to the corners of the next by four inflatable horizontal beams thus the overall structure consists of three

    All the CAS functions, apart from the Roton's pressure hatch, are operated by the compressed gas system used to inflate the structure. During deployment the structure is unfolded by light weight struts, the main supports are then inflated sequentially.

    As the CAS can be fitted to any hatch conforming to the OIN 101332-2266 standard FSI also supply the system to non Roton users.

    Deployable Cargo Crane

    For cargo unloading, where ground facilities are limited, the Roton can be fitted with a support frame and motorised hoist capable of moving loads up to 20 tonnes from the cargo bay up to 15 metres from the cargo bay door (typically on to the load bed of a ground vehicle).

    HL-90 with Cargo Crane and Internal Ramp

    The frame consists of telescopic rail that extends from the top of cargo supported by legs at 5 metre intervals. The whole structure deploys automatically from the cargo bay door and is compatible with the Internal Cargo Handling System, Cargo Ramp and the Cargo Airlock System (CAS).

    The Cargo Crane can be deployed automatically provided that a flat paved surface is available for the support legs however if no prepared surface is available, or there is a significant slope, manual assistance is required. The CAS / Crane combination can also be deployed automatically to produce an airlock structure through which cargo containers can be trasnported by crane.

    It is not possible to combine the crane with both the CAS and the internal ramp unless the ramp can be deployed horizontally. FSI supply an optional kit for the internal ramp which allows it to be used in this manner. With the the crane option in use the first half of the ramp's length (which is covered by the airlock) is horizontal while the final half slopes to the ground. This configuration increases the ramp's slope to 50% and decreases the airlock's capacity to 10% of the cargo bay volume.

    Flotation Kit

    Rotons with a pressurised cargo bay can be fitted with a flotation kit which will enable the Roton to float in the event of having to make a forced landing over water. The kit consists of inflatable flotation bags that support and stabilise the Roton allowing it to float in the water (up to two thirds submerged depending upon loading).

    In order to successfully land on water the Roton must have less than 10% fuel remaining and make a soft landing. Fuel can be vented in flight in emergencies, to reduce the risks of explosion on landing, and an unpowered (autorotation) landing is within the parameters of the flotation kit.

    In Flight Winch

    In many circumstances a Roton may need to transfer cargo or personnel without actually touching down. To facilitate such transfers an in flight winch can be fitted above and to the right of the cargo hatch to transfer loads of up to 500kg to and from a hovering Roton. The winch is stored behind a hinged fairing during high speed flight but once the airspeed slows to below 100 km/h the winch can be deployed above the open cargo bay door.

    In Flight RPV Launch Rail

    Roton's used in survey and reconaissance work are often required to deploy Remotely Piloted Vehicles (RPVs). In order to allow the use of air deployable RPVs Rotons can be fitted with a launch rail which allows the RPV to be ejected from the cargo bay while the Roton is in flight.

    Once the Roton is in low speed flight within the atmosphere the cargo bay door is opened and the launch rail deployed. The rail protrudes 5m from the cargo hatch and into the centre of the cargo bay. Once the rail is deployed the RPV is attached to the launch sled (adapters are available for all common makes of air deployable RPV) within the bay. The sled is then elecromagnetically propelled along the rail, releasing the RPV with sufficient horizontal momentum to carry it beyond the downwash of the rotors (where the RPV can deploy its wings, rotors or gas bag in safety). The sled then brakes for the remaining length of the rail and is returned to the cargo bay to allow the process to be repeated.

    The launch rail cannot be fitted in combination with either the Deployable Cargo Crane or the Cargo Airock System. The launch rail and crane do however use common attachment points and fittings allowing the two systems to be easily and quickly exchanged.

    In Flight Sensor Deployment Mast

    Because of the need for streamlining during re-entry many of the sensors with which are routinely used for survey work are fitted cannot be permanently deployed. The aerials and antennas for such sensors can however be deployed using a mast system housed within the body of the Roton covered by a fairing during high speed flight. Once the speed has dropped to less than 200 km/hr the fairing opens and allows the mast to deploy with the antennae.

    A variety of formats are available allowing a range of antenna sizes and constructions to be utilised. The mast is fitted with standard power supply and comms cabling facilitating the attachment of third party equipment. The mast and the elctro-mechanical deployment system is also designed to enable propriety power supply and communications cabling to be used where required.

    Optimised Rotor Blade Sets

    The blades supplied with each Roton are a general purpose set capable of operation on most inhabited worlds. As a consequence of their adaptability the blades are not as efficient nor is their performance as great as blades designed for any given set of conditions.

    Rotor Blade sets optimised to the planetary conditions are available for all core, colony or outpost worlds within the operational parameters of the Roton (atmospheric pressures between 0.8 and 1.2 atmospheres and gravity between 0.8 and 1.2G).

    Design Notes

    The Roton is a real world reusable launch vehicle. The Rotary Rocket Company have already flown a test version which they plan to develop for a sub orbital flight in 2000. Their version will use a standard rocket engine to reach orbit but will descend on rotor blades.

    The original concept for the Roton was proposed by HMX and also used the rotors for lift off as per my 2300 version.

    Both the web sites linked to above have a wealth of technical details, and the Rotary Rocket site has videos of test flights, animations of operations etc.. I can recommend both of them.

    My 2300AD version of the Roton is an adaptation of the real world designs and is probably less efficient in that it uses liquid hydrogen as fuel (as per the 2300AD standard). One of the real world advantages of the Roton is its use of kerosene. This obviates the need for cryogenic cooling of the fuel and improves the efficiency of the centrifugal pumping.

    Version 1.0


    Copyright J.M. Pearson, 2000