Managing the thermal loads inside a non-airbreathing hypersonic vehicle is particularly difficult. The heat generated by the power electronics, avionics, etc. must be removed so that the components do not exceed their maximum temperatures. These vehicles cannot dump the waste heat into fuel or ram air because they carry no fuel and do not have provisions for ram air. This means that the thermal energy resulting from the heat generated must be dumped into an onboard heat sink. Existing solutions to this problem have been passive systems based on solid-liquid phase change materials (PCMs), which store thermal energy as they melt. Since space is at a premium, a heat sink must store a lot of energy per unit volume, while keeping components below their maximum temperature. In this project, three heat sink concepts are tested, i.e., one based on PCMs, a second on thermal to chemical (TTC) energy storage, and a third on a hybrid combination of the first two. For the first, three different PCMs are tested and for the second a single endothermic chemical reaction. The hybrid PCM/TTC concept consists of a single PCM which plays the dual role of PCM and reactant in the endothermic chemical reaction of the TTC energy storage. To enhance heat sink performance, the use of thermoelectric generators (TEGs) and a local coolant loop are investigated. The advantage of the former is that they transform waste heat into usable electricity, reducing the amount of thermal energy that needs to be stored by the heat sink. The advantage of the latter is that it results in a more uniform cooling of the heat source and more uniform heating of the heat sink. Prototypes of each of the heat sink concepts and the coolant loop are designed, built, and tested. Experimental results indicate that all the solutions tested in this project outperform widely used paraffin heat sink technologies on an energy per unit volume basis. Our experiments also show that a local coolant loop is indeed advantageous and that current off-the-shelf thermoelectric generators do not generate enough power to offset the power requirements of the coolant loop. Significant improvements in the ZT factor of the thermoelectric materials used by the TEG would be required. / Master of Science / All electronics produce waste heat and have a maximum operating temperature above which they fail due to overheating. Heat sinks absorb the waste heat and prevent overheating. Non-airbreathing hypersonic vehicles do not have natural heat sinks like intake air or liquid fuel which are commonly used as heat sinks in airbreathing vehicles. Heat cannot be transferred to the environment due to the high temperatures caused by the friction of hypersonic air travel. This means that all waste heat must absorbed by an onboard heat sink. Existing heat sinks in non-airbreathing hypersonic vehicles use paraffin based solid-liquid phase change materials (PCMs) which store thermal energy as they melt. Three novel heat sink options are evaluated in this project, hydrated salt PCMs which absorb energy as they melt, a chemical reaction which absorbs heat as it reacts, and a hybrid system which incorporates one of the hydrates salt PCM as a reactant in the chemical reaction. Because space is at a premium, these options are evaluated by the amount of energy they can absorb (kilojoules) per unit volume (in3) while keeping the electronics below their maximum temperature. To enhance heat sink performance, the use of thermoelectric generators (TEGs) and a local coolant loop are investigated. The advantage of the former is that they transform waste heat into usable electricity, reducing the amount of thermal energy that needs to be stored by the heat sink. The advantage of the latter is that it results in a more uniform cooling of the electronics and more uniform heating of the heat sink. Prototypes of each of the heat sink concepts and the coolant loop are designed, built, and tested. Experimental results indicate that all the solutions tested in this project outperform widely used paraffin heat sink technologies on an energy per unit volume basis. Our experiments also show that a local coolant loop is indeed advantageous and that current off-the-shelf thermoelectric generators do not generate enough power to offset the power requirements of the coolant loop. Significant improvements in the state of the art of thermoelectric materials would be required for TEGs to generate enough electricity from our waste heat load to power the local coolant loop.

Processos de fragmentação são muito utilizados para identificar estruturas em espectrometria de massas. O estudo da dissociação de íons em fase gasosa induzida por radiação infravermelha adiciona dados energéticos aos processos de fragmentação desses íons. O mecanismo de dissociação induzida por radiação infravermelha envolve a absorção seqüencial de fótons, aumentando progressivamente a energia interna do íon até que o limite de dissociação seja atingido. No presente trabalho, a radiação de corpo negro emitida por um fio de tungstênio aquecido é utilizada para promover a dissociação de íons em fase gasosa. A reação é observada em um espectrômetro de massas por transformada de Fourier. Os íons moleculares de o-metilacetofenona, m-metilacetofenona, p-metilacetofenona e o-cloroacetofenona foram estudados com a técnica. A dependência das constantes de velocidade de dissociação com a temperatura de radiação foi explorada, fornecendo valores de energia de ativação de Arrhenius. Os íons estudados apresentaram resultados semelhantes com aqueles obtidos com o íon molecular de acetofenona, com exceção do íon gerado por o-metilacetofenona. Esse íon apresenta valores de constantes de velocidades bem menores e uma energia de ativação bem acima do observado com os outros íons. Tal comportamento levantou a hipótese de isomerização do íon molecular para uma estrutura enólica mais estável. O íon foi então investigado por cálculos teóricos e por reações específicas íon-molécula. Os resultados indicam que a isomerização é possível, o que também explica a lentidão da reação de dissociação observada. / Fragmentation processes are explored in mass spectrometry to identify structures of ions and neutral molecules. The study of ion dissociation reaction in the gas phase induced by infrared absorption also provides energetic data related to the fragmentation processes. The mechanism of the dissociation by infrared radiation involves sequential photon absorption that progressively raises the internal energy of the ion population until the dissociation threshold. In the present work, the blackbody radiation emitted by a heated tungsten wire is used to promote ion dissociation in gas phase. The reaction is observed in a Fourier transform mass spectrometer. The molecular ions of o-methylacetophenone, m-methylacetophenone, p-methylacetophenone and o-chloroacetophenone were studied with this technique. The dependency of the dissociation rates with the radiation temperature was explored, providing Arrhenius activation energies values. The ions cited above and the molecular ion of acetophenone displayed similar behavior, with the exception of the ion produced by o-methylacetophenone. This ion has dissociation rates much smaller than the others and higher activation energy. This behavior raised the idea of isomerization of the molecular ion to the more stable enolic form. The ion was then investigated with theoretical calculation and with specific reaction with neutral molecules. The results show that the isomerization is possible and this explains the observed slowness of the dissociation reaction.

Processos de fragmentação são muito utilizados para identificar estruturas em espectrometria de massas. O estudo da dissociação de íons em fase gasosa induzida por radiação infravermelha adiciona dados energéticos aos processos de fragmentação desses íons. O mecanismo de dissociação induzida por radiação infravermelha envolve a absorção seqüencial de fótons, aumentando progressivamente a energia interna do íon até que o limite de dissociação seja atingido. No presente trabalho, a radiação de corpo negro emitida por um fio de tungstênio aquecido é utilizada para promover a dissociação de íons em fase gasosa. A reação é observada em um espectrômetro de massas por transformada de Fourier. Os íons moleculares de o-metilacetofenona, m-metilacetofenona, p-metilacetofenona e o-cloroacetofenona foram estudados com a técnica. A dependência das constantes de velocidade de dissociação com a temperatura de radiação foi explorada, fornecendo valores de energia de ativação de Arrhenius. Os íons estudados apresentaram resultados semelhantes com aqueles obtidos com o íon molecular de acetofenona, com exceção do íon gerado por o-metilacetofenona. Esse íon apresenta valores de constantes de velocidades bem menores e uma energia de ativação bem acima do observado com os outros íons. Tal comportamento levantou a hipótese de isomerização do íon molecular para uma estrutura enólica mais estável. O íon foi então investigado por cálculos teóricos e por reações específicas íon-molécula. Os resultados indicam que a isomerização é possível, o que também explica a lentidão da reação de dissociação observada. / Fragmentation processes are explored in mass spectrometry to identify structures of ions and neutral molecules. The study of ion dissociation reaction in the gas phase induced by infrared absorption also provides energetic data related to the fragmentation processes. The mechanism of the dissociation by infrared radiation involves sequential photon absorption that progressively raises the internal energy of the ion population until the dissociation threshold. In the present work, the blackbody radiation emitted by a heated tungsten wire is used to promote ion dissociation in gas phase. The reaction is observed in a Fourier transform mass spectrometer. The molecular ions of o-methylacetophenone, m-methylacetophenone, p-methylacetophenone and o-chloroacetophenone were studied with this technique. The dependency of the dissociation rates with the radiation temperature was explored, providing Arrhenius activation energies values. The ions cited above and the molecular ion of acetophenone displayed similar behavior, with the exception of the ion produced by o-methylacetophenone. This ion has dissociation rates much smaller than the others and higher activation energy. This behavior raised the idea of isomerization of the molecular ion to the more stable enolic form. The ion was then investigated with theoretical calculation and with specific reaction with neutral molecules. The results show that the isomerization is possible and this explains the observed slowness of the dissociation reaction.