The Emdrive Programme – Implications for the Future of the Aerospace Industry
Two other groups, one in China and one in the USA are working on EmDrive projects. We understand that significant progress has been made in both theoretical and experimental work, within these groups. Reports have also been received of work in a further two countries. In the UK we have started the initial performance tests of our first flight thruster. It is anticipated that this thruster will be flown on a technology demonstrator mission.
The main object of this paper is to describe the results of a recent design study for a Hybrid Spaceplane. This vehicle utilises hydrogen cooled, superconducting EmDrive thrusters to provide the static lift. Acceleration is provided by hydrogen fuelled conventional jet and rocket engines. The results of a number of numerical analyses show remarkable performances for different missions. These include sub-orbital passenger transport, Earth orbit payload delivery, and a Lunar landing mission. This design study followed on from the first phase of an experimental, superconducting thruster programme.
It is estimated that the unmanned flying car proposal, using four, liquid hydrogen cooled, versions of the experimental thruster, could begin flight trials in 3 years time.
Superconducting Cavity Thruster and a Proposed Flying Car Demo
The experimental superconducting emdrive
The design of the vehicle results from iterating a mass, power and thrust analysis with inputs from four mission analyses. The mass, dimensions and performance of the jet engines are scaled from the data available for the AMT Titan UAV engine. The power generator is based on an uprated ROTAX 503 aero engine driving a high speed 36 kW alternator.
For 6kW of microwave input power at each thruster, the total lift thrust is 573kg. Thus for an estimated total vehicle mass of 477kg, the vehicle would start to accelerate upwards. However as the average velocity goes above 1m/s, the lift thrust approaches the vehicle mass, and acceleration stops. This is simply the principle of the conservation of energy at work, with energy used to accelerate the vehicle being lost from the stored energy in the thruster, hence lowering the Q.
Clearly, to achieve a useful rate of climb, the jet engines need to be rotated to give vertical thrust and the lift engine operation needs compensation to avoid losing stored energy.
The flight envelope was investigated by running 4 numerical mission analyses. These gave a maximum rate of vertical ascent of 52m/s (170ft/s) and a maximum speed of 118m/s (230 knots) at a maximum altitude of 12.6km (41,300ft). If the altitude is restricted to 1.34km (4,400 ft) then a full liquid hydrogen fuel load will give a maximum range of 97km (60 miles).
Hybrid EmDrive Spaceplane Proposal
The basic Hybrid Spaceplane (HSP) concept is a VTOL carrier vehicle using eight EmDrive lift engines, two hydrogen fuelled jet engines with vertical lift deflectors and up to six hydrogen/ oxygen fuelled rocket engines. Electrical power would be provided by two fuel cells run on the boiled-off hydrogen gas from the lift engines, and liquid oxygen.
The overall dimensions are 35.5 meters long, 13.3m wide and 7m high. Carrier dry mass is 61.1 Tonnes. Maximum fuel load, liquid hydrogen (LH2) and liquid oxygen (LOX) is 190.5 Tonnes.
The mission analyses show the highest g level to be 0.58 g and maximum velocity in air to be 180 km/hr. However the design is aerodynamic (drag coefficient is estimated at 0.35) and the vehicle is capable of a glide landing in an emergency. Control surfaces for this situation are provided by the twin fin and tailplane configuration. A 2 meter scale model is shown on the right above.
The London to Sydney sub-orbital mission starts with a vertical take-off with the spaceplane in a horizontal attitude. Lift is provided by the EmDrive thrusters and vertical acceleration by the jet engines. At 12km altitude the ascent rocket engines are fired to maintain the climb to a cruise altitude of 96km At this height, the orbit engines are fired to accelerate the spaceplane to a cruise velocity of 4km/s. At 90 minutes into the flight, deceleration starts, using the lift engines in a braking mode. Note that when used for deceleration, the EmDrive lift engines are not subject to the dynamic thrust limitation, as no energy is being lost from the stored energy in the resonant cavity. Descent and a vertical landing are controlled by both the lift engines and the jet engines.
For the LEO (Low Earth Orbit) and GEO (Geosync Earth Orbit) missions the spaceplane carrier vehicle can be viewed as a “space elevator without cables”.