On the October DARE test day, the solid propulsion team had the first successful tests of the DXS (DARE eXperimental Solid) Icarus engine development. The DXS Icarus engine was designed for implementation in Project Aether, one of DARE’s flagship projects. Aether is one of our research vehicles, designed to reach supersonic speeds whilst only flying to low altitudes. This makes it more suitable for a launch from closer European launch sites, simplifying the logistics significantly. The project was originally halted due to issues with the previous engine, the DXS Asimov. However, over the last year the Solid Propulsion Team has worked to develop the new engine, Icarus, which is a vast improvement on its predecessor.
Icarus is also developed using KNSB (“Rocket Candy”) as a propellant, which uses sorbitol as a fuel and potassium nitrate as an oxidizer. However, the quality of the propellant has been vastly improved through the application of a vacuum just prior to casting, and by compressing the propellant during curing. This allowed us to obtain densities of 95% of the theoretical value, which is important for improving the reliability and predictability of the engine behavior. Unlike the Asimov, the Icarus engine utilizes a star shaped core, to provide the high initial thrust required to carry Aether out of the tower. It will also have a stronger, carbon fiber casing, a simpler nozzle design, and it uses snaprings to replace the radial bolts previously used to secure the bulkheads.
An Icarus engine is composed of 7 grains, each with propellant mass of 5.7 kg. Two of these single grains were tested in October at our test facility in the Netherlands, with two different nozzle designs. The first motor reached a simulated operating pressure of about 2 MPa whilst the second averaged at a simulated pressure of 4.5 MPa. Tests at different pressure were performed in order to properly verify the reliability of the simulation tool written by the team is over a range of pressures.
While both tests were successful, the measured pressure data showed the engines to be operating at lower pressures than intended. The first test had a mean operating pressure of around 1.5 MPa and the second, 3.5 MPa. Investigations are currently ongoing as to the cause of this, but is currently thought to be the result an error with the simulation tool.
Over the next few months, a series of further single grain tests will be performed, which will focus on improving the reliability of engine, ensuring it is operating at the design pressure, and verifying the design of the carbon fiber casing. At the same time, the design of the full-scale motor will be worked on, to allow for several full-scale engine tests to occur throughout next year. These will qualify Icarus for flight, to hopefully provide Aether with its maiden flight!
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