19 research outputs found
Planetary and asteroid missions. Getting there: Anchoring spacecraft to asteroids
In this hardware project, the students developed ideas for attaching objects to the surface of small moons or asteroids. A device was designed, and built in the university machine shop, that uses a projectile shot into concrete, thereby attaching a model spacecraft to the landing site
Lifting Mechanism for the Mars Explorer Rover
A report discusses the design of a rover lift mechanism (RLM) -- a major subsystem of each of the Mars Exploration Rover vehicles, which were landed on Mars in January 2004. The RLM had to satisfy requirements to (1) be foldable as part of an extremely dense packing arrangement and (2) be capable of unfolding itself in a complex, multistep process for disengaging the rover from its restraints in the lander, lifting the main body of the rover off its landing platform, and placing the rover wheels on the platform in preparation for driving the rover off the platform. There was also an overriding requirement to minimize the overall mass of the rover and lander. To satisfy the combination of these and other requirements, it was necessary to formulate an extremely complex design that integrated components and functions of the RLM with those of a rocker-bogie suspension system, the aspects of which have been described in several prior NASA Tech Briefs articles. In this design, suspension components also serve as parts of a 4- bar linkage in the RLM
Tactile Robotic Topographical Mapping Without Force or Contact Sensors
A method of topographical mapping of a local solid surface within the range of motion of a robot arm is based on detection of contact between the surface and the end effector (the fixture or tool at the tip of the robot arm). The method was conceived to enable mapping of local terrain by an exploratory robot on a remote planet, without need to incorporate delicate contact switches, force sensors, a vision system, or other additional, costly hardware. The method could also be used on Earth for determining the size and shape of an unknown surface in the vicinity of a robot, perhaps in an unanticipated situation in which other means of mapping (e.g., stereoscopic imaging or laser scanning with triangulation) are not available. The method uses control software modified to utilize the inherent capability of the robotic control system to measure the joint positions, the rates of change of the joint positions, and the electrical current demanded by the robotic arm joint actuators. The system utilizes these coordinate data and the known robot-arm kinematics to compute the position and velocity of the end effector, move the end effector along a specified trajectory, place the end effector at a specified location, and measure the electrical currents in the joint actuators. Since the joint actuator current is approximately proportional to the actuator forces and torques, a sudden rise in joint current, combined with a slowing of the joint, is a possible indication of actuator stall and surface contact. Hence, even though the robotic arm is not equipped with contact sensors, it is possible to sense contact (albeit with reduced sensitivity) as the end effector becomes stalled against a surface that one seeks to measure
Ion engine propelled Earth-Mars cycler with nuclear thermal propelled transfer vehicle, volume 2
The goal of this project was to perform a preliminary design of a long term, reusable transportation system between earth and Mars which would be capable of providing both artificial gravity and shelter from solar flare radiation. The heart of this system was assumed to be a Cycler spacecraft propelled by an ion propulsion system. The crew transfer vehicle was designed to be propelled by a nuclear-thermal propulsion system. Several Mars transportation system architectures and their associated space vehicles were designed
Manned mission to Mars with periodic refueling from electrically propelled tankers
In a joint study by students from the Ecole Polytechnique Feminine, France, and the University of California, Los Angeles, a mission concept that had the objective of evaluating the feasibility of a non-nuclear, yet fast, manned mission to Mars was considered. Ion-engine propelled tankers are postulated that would provide mid-coarse refueling of LOX and LH2 to the manned ship. The scenario is therefore one of a 'split mission', yet with the added feature that the cargo ships include tankers for mid-course refueling. The present study is a continuation of one first conducted last year. Emphasis this year was on the design of the tanker fleet
The Mars Exploration Rover Instrument Positioning System
During Mars Exploration Rover (MER) surface operations, the scientific data gathered by the in situ instrument suite has been invaluable with respect to the discovery of a significant water history at Meridiani Planum and the hint of water processes at work in Gusev Crater. Specifically, the ability to perform precision manipulation from a mobile platform (i.e., mobile manipulation) has been a critical part of the successful operation of Spirit and Opportunity rovers. As such, this paper describes the MER Instrument Positioning System that allows the in situ instruments to operate and collect their important science data using a robust, dexterous robotic arm combined with visual target selection and autonomous software functions
Reactions of Fe<sup>+</sup> and FeO<sup>+</sup> with C<sub>2</sub>H<sub>2</sub>, C<sub>2</sub>H<sub>4</sub>, and C<sub>2</sub>H<sub>6</sub>: Temperature-Dependent Kinetics
We present the first temperature-dependent
rate constants and branching
ratios for the reactions of Fe<sup>+</sup> and FeO<sup>+</sup> with
C<sub>2</sub>H<sub>2</sub>, C<sub>2</sub>H<sub>4</sub>, and C<sub>2</sub>H<sub>6</sub> from 170 to 700 K. Fe<sup>+</sup> is observed
to react only by association with the three hydrocarbons, with temperature
dependencies of <i>T</i><sup>–2</sup> to <i>T</i><sup>–3</sup>. FeO<sup>+</sup> reacts with C<sub>2</sub>H<sub>2</sub> and C<sub>2</sub>H<sub>4</sub> at the collision
rate over the temperature range, and their respective product branchings
show similar temperature dependences. In contrast, the reaction with
ethane is collisional at 170 K but varies as <i>T</i><sup>–0.5</sup>, while the product branching remains essentially
flat with temperature. These variations in reactivity are discussed
in terms of the published reactive potential surfaces. The effectiveness
of Fe<sup>+</sup> as an oxygen-transfer catalyst toward the three
hydrocarbons is also discussed
Comment on “Role of (NO)<sub>2</sub> Dimer in Reactions of Fe<sup>+</sup> with NO and NO<sub>2</sub> Studied by ICP-SIFT Mass Spectrometry”
Comment on “Role of (NO)<sub>2</sub> Dimer
in Reactions of Fe<sup>+</sup> with NO and NO<sub>2</sub> Studied
by ICP-SIFT Mass Spectrometry
Activation of Methane by FeO<sup>+</sup>: Determining Reaction Pathways through Temperature-Dependent Kinetics and Statistical Modeling
The temperature dependences of the
rate constants and product branching
ratios for the reactions of FeO<sup>+</sup> with CH<sub>4</sub> and
CD<sub>4</sub> have been measured from 123 to 700 K. The 300 K rate
constants are 9.5 × 10<sup>–11</sup> and 5.1 × 10<sup>–11</sup> cm<sup>3</sup> s<sup>–1</sup> for the CH<sub>4</sub> and CD<sub>4</sub> reactions, respectively. At low temperatures,
the Fe<sup>+</sup> + CH<sub>3</sub>OH/CD<sub>3</sub>OD product channel
dominates, while at higher temperatures, FeOH<sup>+</sup>/FeOD<sup>+</sup> + CH<sub>3</sub>/CD<sub>3</sub> becomes the majority channel.
The data were found to connect well with previous experiments at higher
translational energies. The kinetics were simulated using a statistical
adiabatic channel model (vibrations are adiabatic during approach
of the reactants), which reproduced the experimental data of both
reactions well over the extended temperature and energy ranges. Stationary
point energies along the reaction pathway determined by ab initio
calculations seemed to be only approximate and were allowed to vary
in the statistical model. The model shows a crossing from the ground-state
sextet surface to the excited quartet surface with large efficiency,
indicating that both states are involved. The reaction bottleneck
for the reaction is found to be the quartet barrier, for CH<sub>4</sub> modeled as −22 kJ mol<sup>–1</sup> relative to the
sextet reactants. Contrary to previous rationalizations, neither less
favorable spin-crossing at increased energies nor the opening of additional
reaction channels is needed to explain the temperature dependence
of the product branching fractions. It is found that a proper treatment
of state-specific rotations is crucial. The modeled energy for the
FeOH<sup>+</sup> + CH<sub>3</sub> channel (−1 kJ mol<sup>–1</sup>) agrees with the experimental thermochemical value, while the modeled
energy of the Fe<sup>+</sup> + CH<sub>3</sub>OH channel (−10
kJ mol<sup>–1</sup>) corresponds to the quartet iron product,
provided that spin-switching near the products is inefficient. Alternative
possibilities for spin switching during the reaction are considered.
The modeling provides unique insight into the reaction mechanisms
as well as energetic benchmarks for the reaction surface