Design, Verification and Validation of a Micropropulsion Thrust Stand

At the chair of Space Systems Engineering, students and staff work on the development of small propulsion systems in a wide thrust capability. Especially in recent years low thrust propulsion systems have gained an increased amount of interest in the entire department of Space Engineering. To support the development of these propulsion systems, there is a need for the testing of micropropulsion systems that provide a thrust in the 1 ?N to 5 mN range. This capability complements the existing measurement equipment of the Delft Aerospace Rocket Thrust Stand facility of 0.5 mN to 1 N. To provide a solution to this need, the research question for this research is phrased as: "How can the DARTS facility be upgraded to measure thrust levels in the 1 ?N to 5 mN range and impulse bits in the 1 ?Ns to 1 mNs range?". Using numerical modelling the answer to that question is found in an upgraded design of the TB-2m thrust stand that was developed in 2010 by Perez-Grande. By introducing several improvements, amongst which are the replacement of the sensor system by a capacitive displacement sensor and the use of a segmented counter mass, the range of the TB-2m has been extended and the accuracy has been improved to meet the new requirements. A complementary calibration system is designed that allows an in situ calibration for the measurement of both the thrust and impulse bits. Where typical calibration actuators supply a force that is non-linear with engagement distance and have to rely on displacement measurements to linearize the calibration force, the new actuator is able to provide a force that is independent on the distance to the target. Using a specially designed solenoid that has a linearly varying turn-density along its length, the magnetic field is shaped to provide a constant magnetic gradient. The thrust stand and calibration system are manufactured and tested. Using a previously tested cold gas thruster that is provided by Bradford Engineering, the complete thrust measurement system is validated with hardware-in-the-loop. This process has shown that the pendulum is in a state constant of oscillation. It is expected that this oscillation is removed by the introduction of a Foucault damper in the next design iteration. The validation process has shown that the thrust range is on par with the requirements. Also impulse bits can be measured, but the constant state of oscillation prohibited the detection of the smallest impulse bits of 1 ?Ns. Future experiments have to show whether the required and predicted accuracies are achieved.Space Systems EngineeringSpace EngineeringAerospace Engineerin

Towards a heat transfer based distance sensor for measuring sub-micrometer separations

In this thesis a proof-of-principle demonstration is developed that uses the heat flux between a probe and a sample as a proxy for their separation. The proposed architecture uses a probe that consists of a bilayer cantilever with an attached sphere at its free end. The deflection of the cantilever that is caused by the heat input is measured using the optical beam deflection method. To eliminate temperature dependent effects the temperatures of the probe and the sample are kept constant. Moreover, a total internal reflection microscopy is included to provide an independent measurement of the separation between the probe and the sample. This architecture allows the measurement of the heat flux as a function of only the separation. An equation is derived that relates the output signal of the instrument directly to the heat flux that is absorbed by the probe. It couples the top-level design parameters to the system output and is used to study and design the separate elements. In addition to the design of the instrument, the research contributes a detailed study of the influences of the microsphere and the microcantilever on the heat flux measurement. Structural Optimization and Mechanic

Design of a calorimeter for near-field heat transfer measurements and thermal scanning probe microscopy

Multilayer cantilever beams are used in the measurement of near-field radiative heat transfer. The materials and dimensions of the cantilever probe are chosen in order to improve system performance in terms of sensitivity and noise. This is done using an analytical model that describes the thermo-mechanical and mechanical behavior of the cantilever and its influences at the system level. In the design, the optical reflectance and the sensitivity of cantilever rotation to the heat input are maximized under constraints for thermal noise, temperature drift, and a lower bound for the spring constant. The analytical model is verified using finite element analysis, which shows that the effects of radiative losses to the environment are insignificant for design purposes, while the effects of ignoring three-dimensional heat flow introduces larger errors. Moreover, the finite element analysis shows that the designed probes are up to 41 times more sensitive than the often used commercial-of-the-shelf benchmark and have a four times lower thermal noise. Experimental validation of the designed probes shows good agreement with the theoretical values for sensitivity. However, the most sensitive designs were found to be susceptible to damage due to overheating and carbon contamination. </p

Design of a calorimeter for near-field heat transfer measurements and thermal scanning probe microscopy

Multilayer cantilever beams are used in the measurement of near-field radiative heat transfer. The materials and dimensions of the cantilever probe are chosen in order to improve system performance in terms of sensitivity and noise. This is done using an analytical model that describes the thermo-mechanical and mechanical behavior of the cantilever and its influences at the system level. In the design, the optical reflectance and the sensitivity of cantilever rotation to the heat input are maximized under constraints for thermal noise, temperature drift, and a lower bound for the spring constant. The analytical model is verified using finite element analysis, which shows that the effects of radiative losses to the environment are insignificant for design purposes, while the effects of ignoring three-dimensional heat flow introduces larger errors. Moreover, the finite element analysis shows that the designed probes are up to 41 times more sensitive than the often used commercial-of-the-shelf benchmark and have a four times lower thermal noise. Experimental validation of the designed probes shows good agreement with the theoretical values for sensitivity. However, the most sensitive designs were found to be susceptible to damage due to overheating and carbon contamination. Structural Optimization and Mechanic

Automatic alignment of optical beam deflection system for AFM cantilevers

The optical beam deflection (OBD) technique is used in many Atomic Force Microscopes to measure the motion of a cantilever as it probes the scanned surface. From the measured rotation, surface and sub-surface properties of the sample can be deduced. To maximize the sensitivity of the measurement, the combination of laser and cantilever should be aligned such that the laser impinges on the cantilever as close to its end tip as possible. Table-top AFM systems often use manual alignment. For industrial applications automatic alignment is necessary. This paper describes a method to automate this alignment procedure, using a laser induced thermo-mechanical response to actively bend the cantilever. This method also has applications in the characterization of bi-material cantilevers in a non-contact and non-destructive manner. The details of this characterization and the mathematical derivation are published elsewhere

Non-contact distance measurement and profilometry using thermal near-field radiation towards a high resolution inspection and metrology solution

Optical near-field technologies such as solid immersion lenses and hyperlenses are candidate solutions for high resolution and high throughput wafer inspection and metrology for the next technology nodes. Besides sub-diffraction limited optical performance, these concepts share the necessity of extreme proximity to the sample at distances that are measured in tens of nanometers. For the instrument this poses two major challenges: 1) how to measure the distance to the sample? and 2) how to position accurately and at high speed? For the first challenge near-field thermal radiation is proposed as a mechanism for an integrated distance sensor (patent pending). This sensor is realized by making a sensitive calorimeter (accuracy of 2:31nW root sum squared). When used for distance measurement an equivalent uncertainty of 1nm can be achieved for distances smaller than 100 nm. By scanning the distance sensor over the sample, thermal profilometry is realized, which can be used to inspect surfaces in a non-intrusive and non-contact way. This reduces wear of the probe and minimizes the likelihood of damaging the sample.Structural Optimization and Mechanic

Towards an effective reduction of intensity noise in laser diodes

Structural Optimization and Mechanic

Meta-instrument: An opto-mechanical platform for imaging near-field optical instruments

Structural Optimization and Mechanic

A new horizon: Using heat to measure distance in high performance metrology solutions

Structural Optimization and Mechanic

Reduction of laser diode intensity noise in optical beam defection systems

Structural Optimization and Mechanic