The question is, "How do you test an experimental liquid-fueled rocket engine without personal risk if it all goes wrong?"
The answer is "Do it from a very long way away".
In fact using the equipment that's been developed specially for these tests the engineer can be up to 4km away if necessary, but that's probably not practical.
While the FIDO elements (individual enginlettes, 8 of which form the complete "Cerberus" engine) are being tested and characterised, a great deal of
parametric data ranging from temperatures at various points to fuel flow rates needs to be sent from the engine to the data logger. A command path
to the engine also needs to be in place so that software can control aspects of its operation such as start-up, shut-down and throttling.
To accomplish this, a PC is used as the data logger which also runs specially written software designed to effect engine control. This software interfaces to a 500mW 868MHz
tranceiver via a USB port. The photos on the right show the host-end tranceiver, and you may notice that there is also a GPS antenna which will be
explained in a later article. The USB interface device used is a Cypress CY7C68013-56 FX2, embedded within which is a very handy enhanced 8051 processor core.
At the "hot end" ie next to the engine under test is a compatible tranceiver unit that also houses all of the drive and interface electronics for the engine. In the picture
on the upper right, the box is shown next to the ignition spark generator. Since it is an important design feature that the engines should be able to be restarted in-flight
(in the event of a flame-out, or as part of the mission specs), each enginlette carries its own spark plug and the whole ignition assembly is carried into flight.
The processing power for the hot-end engine interface comes courtesy of the very nicely spec'd (and priced) PIC18F87J11 from Microchip.
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Engine Test Equipment
Photo Credit: NAs / Peter Jones
Remote Control Transmitter
Photo Credit: NAs / Peter Jones
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