Analysis of a spacecraft life support system for a Mars mission

This report summarizes a trade study conducted as part of the Fall 2002 semester Spacecraft Life Support System Design course (ASEN 5116) in the Aerospace Engineering Sciences Department at the University of Colorado. It presents an analysis of current life support system technologies and a preliminary design of an integrated system for supporting humans during transit to and on the surface of the planet Mars. This effort was based on the NASA Design Reference Mission (DRM) for the human exploration of Mars [NASA Design Reference Mission (DRM) for Mars, Addendum 3.0, from the world wide web: http://exploration.jsc.nasa.gov/marsref/contents.html.]. The integrated design was broken into four subsystems: Water Management, Atmosphere Management, Waste Processing, and Food Supply. The process started with the derivation of top-level requirements from the DRM. Additional system and subsystem level assumptions were added where clarification was needed. Candidate technologies were identified and characterized based on performance factors. Trade studies were then conducted for each subsystem. The resulting technologies were integrated into an overall design solution using mass flow relationships. The system level trade study yielded two different configurations--one for the transit to Mars and another for the surface habitat, which included in situ resource utilization. Equivalent System Mass analyses were used to compare each design against an open-loop (non-regenerable) baseline system.     

Unusually strong magnetic fields in Titan’s ionosphere: T42 case study

Observations of unusually large magnetic fields in the ionosphere indicate periods of maximum stress on Titan’s ionosphere and potentially of the strongest loss rates of ionospheric plasma. During Titan flyby T42, the observed magnetic field attained a maximum value of 37 nT between an altitude of 1200 and 1600 km, about 20 nT stronger than on any other Titan pass and close to five times greater in magnetic pressure. The strong fields occurred near the corotation-flow terminator rather than at the sub-flow point, suggesting that the flow which magnetized the ionosphere was from a direction far from corotation and possibly towards Saturn. Extrapolation of solar wind plasma conditions from Earth to Saturn using the University of Michigan MHD code predicts an enhanced solar wind dynamic pressure at Saturn close to this time. Cassini’s earlier exits from Saturn’s magnetosphere support this prediction because the Cassini Plasma Spectrometer instrument saw a magnetopause crossing three hours before the strong field observation. Thus it appears that Titan’s ionosphere was magnetized when the enhanced solar wind dynamic pressure compressed the Saturnian magnetosphere, and perhaps the magnetosheath magnetic field, against Titan. The solar wind pressure then decreased, leaving a strong fossil field in the ionosphere. When observed, this strong magnetic flux tube had begun to twist, further enhancing its strength.     

Anthropogenic trigger of substorms and energetic particles precipitations

The high-frequency (HF) emission in near-Earth space from various powerful transmitters (radio communications, radars, broadcasting, universal time and navigation stations, etc.) form an integral part of the modern world that it cannot do without. In particular, special-purpose research facilities equipped with powerful HF transmitters are used successfully for plasma experiments and local modification of the ionosphere. In this work, we are using the results of a complex space-ground experiment to show that exposure of the subauroral region to HF emission can not only cause local changes in the ionosphere, but can also trigger processes in the magnetosphere–ionosphere system that result in intensive substorm activity (precipitations of high-energy particles, aurorae, significant variations in the ionospheric parameters and, as a consequence, in radio propagation conditions).     

Spin parameters of Low Earth Orbiting satellites Larets and Stella determined from Satellite Laser Ranging data

Satellite Laser Ranging (SLR) measurements contain information about the spin parameters of the fully passive, geodetic satellites. In this paper we spectrally analyze the SLR data of 5 geodetic satellites placed on the Low Earth Orbits: GFZ-1, WESTPAC, Larets, Starlette, Stella, and successfully retrieve the frequency signal from Larets and Stella only. The obtained signals indicate an exponential increase of the spin period of Larets: T = 0.860499·exp(0.0197066·D) [s], and Stella: T = 13.5582·exp(0.00431232·D) [s], where D is in days since launch. The initial spin periods calculated from the first month of the SLR observations are: Larets: T_initial = 0.8239 s, Stella: T_initial = 13.2048 s. Analysis of the apparent effects indicates the counter-clockwise spin direction of the satellites. The twice more heavy Stella lost its rotational energy more than four times slower than Larets. Fitting the spin model to the observed spin trends allows determination of the spin axis orientation evolution for Larets and Stella before their rotational period becomes equal to the orbital period.     

Difficulties in the study of cosmic radio noise absorption at 30 MHz using riometer at low latitude station,Kolhapur (Lat-16.8°N,Long-74.25°E)

A dual dipole antenna has been installed at low latitude station Kolhapur (Geographic 16.8°N, 74.25°E), Maharashtra, India for the study of cosmic radio noise absorption using Solid State Riometer (which operates at 30 MHz) during pre phase of 24th solar maxima. The aim for this type of study over Kolhapur was to know the response of lower (D region) ionosphere over low latitude by cosmic radio noise absorption using riometer technique during quite period as well as sudden ionospheric disturbances (SID). The observations are being taken for 3 years. Two different sites (∼40 km away from each other) were used for the installation of riometer equipment assuming minimum local noise. It is found that solar noise to cosmic radio noise hence resulting in signal saturation. The night time signal is relatively free of interference but sometimes local noise is responsible for spike-like signatures. Hence it is concluded that Kolhapur (a low latitude station) is not suitable for the study of cosmic radio noise absorption on 30 MHz with riometer and dual dipole antenna. Proper choice for operating frequency of riometer and antenna gain is suggested for low latitude use of this technique for ionospheric deviative and nondeviative absorption studies.     

Time-dependent stresses in a beam under a load moving along its surface

We studied the time-dependent processes in a beam under the action of the load that is normal to its surface and moves with the constant velocity. It was found that the maximum stresses are realized in the fixed beam section at different moments of time depending on the travel speed of external load. With increasing the load movement velocity, the maximum stresses in the region of beam clamping are reduced, while the levels of local normal and shear stresses in the limits of its action increase more significantly approaching to the limiting values in accordance to the known experimental fact that at high rates the beam failure is caused by shear stresses.     

General Relativity Accuracy Test (GReAT): New configuration for the differential accelerometer

We presents the results of an activity concerning the test of the Einstein Weak Equivalence Principle with an accuracy of about 5 × 10⁻¹⁵. The experiment will be performed in an “Einstein elevator” using a differential accelerometer with a final sensitivity of about 10⁻¹⁴ g_⊕/Hz^1/2. The differential accelerometer is spun about an horizontal axis at a frequency in the range 0.5–1 Hz in order to modulate, during the free fall, the signal from a possible violation of the Equivalence Principle. In the paper the perturbing effects with the same signature of the possible violation are analyzed and constrained. The experimental results obtained in the laboratory with a first prototype of the differential accelerometer are discussed, comparing this results with those obtained using a new prototype.     

Kink-like mode of a double gradient instability in a compressible plasma current sheet

A linear MHD instability of the electric current sheet, characterized by a small normal magnetic field component, varying along the sheet, is investigated. The tangential magnetic field component is modeled by a hyperbolic function, describing Harris-like variations of the field across the sheet. For this problem, which is formulated in a 3D domain, the conventional compressible ideal MHD equations are applied. By assuming Fourier harmonics along the electric current, the linearized 3D equations are reduced to 2D ones. A finite difference numerical scheme is applied to examine the time evolution of small initial perturbations of the plasma parameters. This work is an extended numerical study of the so called “double gradient instability”, – a possible candidate for the explanation of flapping oscillations in the magnetotail current sheet, which has been analyzed previously in the framework of a simplified analytical approach for an incompressible plasma. The dispersion curve is obtained for the kink-like mode of the instability. It is shown that this curve demonstrates a quantitative agreement with the previous analytical result. The development of the instability is investigated also for various enhanced values of the normal magnetic field component. It is found that the characteristic values of the growth rate of the instability shows a linear dependence on the square root of the parameter, which scales uniformly the normal component of the magnetic field in the current sheet.     

HORACE: A compact cold atom clock for Galileo

HORACE (HOrloge à Refroidissement d’Atomes en Cellule = clock based on atoms cooled from vapour cell) is a compact cold caesium atom clock developed in SYRTE at Paris Observatory. This clock can operate both on ground and in microgravity environment. Design of HORACE is based on isotropic light cooling, allowing performing the whole clock sequence (cooling, atomic preparation, Ramsey interrogation and detection) at the same place. Compared to more conventional cold atom clocks such as atomic fountains, the use of isotropic light cooling simplifies both the optical part of the setup and the detection sequence, and leads to a drastic size reduction of the physics package. Very good short-term performances have been demonstrated at SYRTE since relative frequency instability of 2.2 × 10⁻¹³ τ^−1/2 has been obtained. Optimization of the long term stability is still under progress and current results show relative frequency instability around 3 × 10⁻¹⁵ in 10⁴ s of integration. With these performances, HORACE appears as a good candidate both for Galileo’s ground segment clock and for onboard Galileo clock.     

Theoretical and experimental study of a method for the protection of spacecraft from high–speed particles

In this paper, we perform numerical simulation and experimental determination of the limiting resistance of the spacecraft design elements used when developing anti-meteorite protection of spacecraft as well as protection against space debris. One possible way to increase the efficiency of protective shields and satisfy the requirements of the mass characteristics of the latter is the use of mesh barriers.