This paper gives a brief overview of the rocket test programmes undertaken at the Westcott (UK) rocket test facility in the last two years, in particular those undertaken at the Airborne Engineering, Nammo Westcott and The Falcon Project test sites. This encompasses a variety of testing for liquid, gaseous and solid propellant rockets, ranging from fundamental propellant research to qualification testing.
As part of a global drive to move towards less toxic propellants, Nitrous Oxide Fuel Blends (NOFB) have been identified as a potential monopropellant to replace hydrazine. The European Fuel Blend Development programme was initiated as a low TRL investigation to further develop European knowledge and capability in this area. TNO undertook a scoping study to downselect to a promising fuel blend of nitrous oxide and ethanol, and performed initial miscibility studies. This fuel blend was then tested with hot firings.
This paper describes the test rig design for mixing and injecting the liquid NOFB, and presents initial results from the first hot firings. The NOFB was found to have good combustion efficiency and performance. No flashback events were seen with the current setup. Two downsides were noted, however: first, that the pre-mixed propellant was found to burn quickly with high heat release, resulting in large heat loss to the copper combustion chamber, and injector face burnout in the final test. Second, that the injector pressure drop was found to be strongly dependent on the temperature of the injector face, because the heat transfer increases the proportion of nitrous oxide that flash boils in the injectors.
A project is underway at Airborne Engineering Ltd. (AEL) to develop a VTVL technology demonstrator. A subscale vehicle, based on a 300N N2O/IPA throttleable bipropellant thruster, has been constructed and was presented at the previous conference. This paper presents details of the subsequent throttle control testing, the throttle control system methodology and testing data.
The throttle control of the nitrous oxide was found to be the most difficult element of the thruster control, because the fluid is self-pressurising in the propellant tank and therefore is in a two phase state throughout the plumbing. The mass flow passing through the throttle valve is therefore highly sensitive to the state of the upstream fluid and downstream pressure, because this governs the degree of flash-boiling.
During static testing, two salient points were noted. First, that the N2O injector pressure drop into the combustion chamber was found to be almost independent of massflow, because of a balance between flash-boiling in the control valve and flash-boiling in the injectors, and second, that the chamber pressure varied almost linearly with the pulse width provided to the N2O servo control valve. The throttle control system for the N2O is therefore designed to use feedback control from the combustion chamber pressure, based on a second order transfer function of the thruster response derived from experimental data. The control loops are shown to perform well enough to proceed to vehicle flight testing.
The unique propulsion requirements for air-breathing space planes have resulted in a R&D programme to investigate various aspects of the Sabre engine technology. These include altitude compensation and the requirement to transition from air-breathing mode to pure rocket mode. This paper describes the challenges involved in the design, construction and operation of a test rig for investigating Sabre nozzle and combustor design using a 20KN subscale engine. Such challenges include precision control and measurement of massflow in non-ideal gases, multi-axis thrust measurement, nozzle wall-pressure profiling and automated analysis of large data sets.
There is increasing interest within Europe in carrying out a robotic Lunar or Martian planetary landing mission. This kind of mission requires the development of technologies such as autonomous landing and hazard avoidance. These technologies require testing in a representative environment, such as on a VTVL (vertical take-off, vertical landing) vehicle. VTVL platforms have been developed in the USA, such as the NASA Morpheus project. However, there is a need for access to such a vehicle in Europe for evaluating technologies such as LIDAR instruments and for validating hazard detection and avoidance algorithms.
To address this need, a project is underway at Airborne Engineering to develop a VTVL technology demonstrator. A sub-scale vehicle, based on a 300N throttleable bipropellant thruster, has been constructed and static tested. The paper will present details of the design and testing of the sub-scale vehicle as well as outline details of the full-sized platform which will be able to flight-test lander instrumentation, payloads and propulsion sub-systems.