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Can a spectrogram for a composite material, ie a rock, be derived from chemical, crystallographic, and other data?

Question asked by Julian Grodzicky on Nov 21, 2019
Latest reply on Nov 22, 2019 by Steven Cooke

I'm a first year part-time engineering student at the University of South Australia, involved in a global citizen science project, Space Decentral Project Coral, headquartered in San Francisco, CA. Our team is designing a mission to demonstrate the production of a building material article, ie a brick or paver, by microwave sintering of lunar regolith.


I have a background in electronics, and in geology. My task is to find the optimum microwave frequency/s for sintering lunar regolith. This has implications for C-SWAP (cost, size, weight, and output power level) on our lunar lander.


Microwave sintering and/or melting of lunar rock and regolith has been demonstrated in the literature, but in virtually all cases, the investigators are using a domestic microwave oven and unlimited power from the electricity grid. Our lander will be mobile and quite small, and there is a limit to how many photovoltaic solar cells we can attach to the vehicle, and thus, how much power we can generate. In addition, we need to budget our generated power to other functions on the lander as well. So, our maximum generated power is 0.5-1 kW, and may be less.


I'm pretty sure for our purposes, access to lunar material for analysis isn't an option, so I've been working on another way to get my result, and I wish to ask someone here for a reality check.


Spectrographic data for the lunar material in the microwave frequency region doesn't exist. Believe me, I've looked pretty hard. There are some spectra in the low radio frequency (0.5 - 10 MHz), and plenty in the FIR to VIS region.


I have collected, or have access to, the published chemical, mineralogical, crystallographic data for lunar material. In addition, there are plenty of analyses for terrestrial constituent analogues of lunar rock (basalts). I also am reading the papers for all the past lunar mission microwave remote sensing experiments and data.


My plan is to use this data to forward model, ie derive or synthesise, the microwave absorption spectrum of lunar rock and regolith material, from 1 to, say, 150-200GHz. I realise some of the data has been derived from spectrographic techniques, but for reasons I've outlined above, that option isn't isn't available to me. I presume the principal of reciprocal action applies here.


The maxima should tell me which frequencies are being absorbed the most, and hence presumably heating the material. The higher the frequency my model is valid to, the better, since the microwave source generator, whichever one, would be smaller and lighter, and also the most energetic (Е = hν). In addition, at the high end, I'm starting to get into the Terahertz region, and there are currently some interesting technological developments happening in this region, with higher power level output devices becoming available.


I would test my model from existing analyses of terrestrial basalts, backed up with 2-3(?5) laboratory analyses to validate my method, depending on lab access, and what I can afford.


My current approach is to understand the interaction of matter with microwave radiation. I started from the Wikipedia articles, and have gone on to read about dielectric materials, and relaxation and dispersion mechanisms - Cole-Cole, Cole–Davidson, and Havriliak–Negami. Along the way I have strayed into fractional calculus. My next step would be to start connecting chemical and structural composition with dielectric constant, and to learn how the microwave spectral response is affected by multiple dielectric compositions.


Concurrently, I've identified some gaps in my knowledge, and I'm reading up on quantum mechanics, and the attendant mathematics and physics.


Is there any way I can use spectra or their information in other regions of the EM spectrum for any purpose in the microwave region?


Am I barking up the wrong tree?


Thanks in advance.