CubeSat Active Thermal Control via Microvascular Carbon Fiber Channel Radiator

Small spacecraft rarely have space for any thermal control subsystems and often must perform operations in “burst” mode as a result. The few spacecraft who do have control rely on low-complexity thermal control systems which conduct heat to the bus structure and then radiate the heat away. These simplistic techniques are sufficient for low power missions in Low Earth Orbit (LEO) but are not capable of dumping the heat produced in new mission profiles that are in development. This is due to small spacecraft incorporating increasingly advanced subsystems which have difficult thermal control requirements such as propulsion systems or high-power antennas. The University of Illinois at Urbana-Champaign, in partnership with NASA Ames Research Center, is developing a thermal control system for small spacecraft. This control system uses a deployable radiator panel made from carbon fiber with micro-vascular circulatory system for coolant. This paper is a follow-up on the previous year’s SmallSat conference. A bench prototype of the thermal control subsystem was designed and built. The prototype underwent a range of thermal and vibration tests at NASA Ames. Test results and lessons learned are presented. Moving forward, test conclusions will require some design parameters to be changed and the subsystem will reach TRL 6 by the end of the two-year program

The effects of nitroxyl (HNO) on soluble guanylate cyclase activity: interactions at ferrous heme and cysteine thiols

It has been previously proposed that nitric oxide (NO) is the only biologically relevant nitrogen oxide capable of activating the enzyme soluble guanylate cyclase (sGC). However, recent reports implicate HNO as another possible activator of sGC. Herein, we examine the affect of HNO donors on the activity of purified bovine lung sGC and find that, indeed, HNO is capable of activating this enzyme. Like NO, HNO activation appears to occur via interaction with the regulatory ferrous heme on sGC. Somewhat unexpectedly, HNO does not activate the ferric form of the enzyme. Finally, HNO-mediated cysteine thiol modification appears to also affect enzyme activity leading to inhibition. Thus, sGC activity can be regulated by HNO via interactions at both the regulatory heme and cysteine thiols

The Gauss House

The focus of my research is the development of a hardware-in-the-loop (HWIL) attitude determination and control (ADC) simulator for the University of Illinois Cube Sat, IlliniSat-2. IlliniSat-2 measures the Earths magnetic field to determine its pointing direction, much like a digital compass. With this in mind, I developed a simulator to manipulate the magnetic field around the satellite to make it perceive itself to be in orbit. The cage depicted here is a triaxial Helmholtz Coil, which I have nicknamed the Gauss House. There are over 1.5 miles of copper wire wound around the six square rings composing the cage. By selectively running different currents through each coil, I can create a uniform magnetic field within the cage in any direction. Furthermore, by replicating the magnetic field experienced by a satellite running in a real-time software simulation, I am able to convince IlliniSat-2 that it is tumbling in orbit, which allows us to test how the assembled satellite actually functions prior to launch. The arrows depicted here represent the magnetic field created by the Gauss House; the blue arrows represent our desired uniform magnetic field direction. IlliniSat-2 is located at the center of the cage. The background is its perceived orbit

A novel magnetic field approach to simulate spacecraft attitude determination and control

The University of Illinois is developing a CubeSat bus, known as IlliniSat-2, which will be capable of achieving 3-axis attitude control via magnetic torque coils and attitude determination via Kalman-filtered magnetometer data with an optional Sun vector measurement. This innovative new attitude determination and control (ADC) method is more sophisticated than those traditionally employed on CubeSats and will require extensive pre-flight testing to ensure that IlliniSat-2 functions properly after it is launched. To accommodate such testing, a hardware-in-the-loop ADC simulation suite, known as CubeSim, is being developed. CubeSim uses a large triaxial Helmholtz coil, known as the HC3, to dynamically manipulate the magnetic field around a CubeSat to simulate an orbital environment. In the case of an IlliniSat-2 bus, the HC3 testbed allows the CubeSat to determine its attitude in real-time. CubeSim will also receive control feedback from the CubeSat and update the simulated attitude accordingly. This thesis will discuss the development of CubeSim, including the theory and design of the HC3 and the associated software interfaces. Results from initial simulations and testing will be presented and the path for future work will be discussed