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At least 1,225 records · Page 68
All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Crew Exploration Vehicle Environmental Control and Life Support Development Status

The Crew Exploration Vehicle (CEV) is the first crew transport vehicle to be developed by the National Aeronautics and Space Administration (NASA) in the last thirty years. The CEV is being developed to transport the crew safely from the Earth to the Moon and back again. The mission is similar to the Apollo approach with expanded capabilities and extended durations to support a larger crew and a longer mission. The Environmental Control and Life Support (ECLS) system, which includes the life support and thermal control systems, will have to meet these new requirements, taking advantage of the latest in component development where necessary and applicable.

Lewis, John F.↗
NASA NTRS2004

An Acquisition Control for the Laser Interferometer Space Antenna

The Laser Interferometer Space Antenna (LISA) mission is a planned gravitational wave detector consisting of three spacecraft in heliocentric orbit. Laser interferometry is used to measure distance fluctuations between test masses aboard each spacecraft to the picometer level over a 5 million kilometer separation. Each spacecraft has two incoming and two outgoing laser beams for a total of six laser links. These links will have to be established sequentially at the start of the mission, and the spacecraft control systems must aim their lasers at each other with pointing motions less than 8 nanoradians per root Hertz in the frequency band 0.1-100 mHz. This paper presents a strategy for the laser acquisition process. The outgoing beam on one spacecraft is spoiled to provide a wide beam that encompasses the accuracy (noise and mounting bias) of the star tracker. The control system then takes advantage of an array of sensors with increasing sensitivity to quiet the receiving spacecraft and lock the laser. This process is carried out for each of the six links of LISA. A complete analysis and simulation of the acquisition process are presented.

Maghami, Peiman G.↗
NASA NTRS1984

Injection module thrust vector control

A three-axis controlled Injection Module propelled by a Star 48 solid rocket motor has been considered for use as a final 'kick' stage to supplement the Inertial Upper Stage in a proposed launch option for the Galileo and International Solar Polar missions. A flight control law for the Injection Module is developed. A position plus rate control law is considered, with integral, path guidance, and derived rate terms added for improved pointing accuracy and fuel efficiency. Selection of control gains is accomplished with the help of analytical limit cycle expressions and verified by computer simulation of the closed loop system. A computer simulation of the flight control system is built around a rigid spacecraft model with gyro dynamics and thruster delays included. Models for pitch/yaw/roll disturbance torques are included. Through simple gain changes the proposed flight control law is shown to accommodate the widely different mass properties of the Galileo and International Solar Polar spacecraft. Pointing accuracies of better than the desired 0.2 degrees are achieved.

Bell, C. E.↗
NASA NTRS1986

The mission configuration process for the Spartan attitude control system

The Spartan attitude control system (ACS) control electronics assembly cold plate has a standard connector interface to the rest of the Spartan payload and ground equipment. The connectors carry gyro signals, optical sensor signals, the experiment interface, the gas command decoder interface, and a pneumatics interface. Different flights can employ different optical sensor complements; the ACS engineer must accordingly connect the sensor error signals to the proper pins and connectors on the ACS electronics.

Stone, R. W.↗
NASA NTRS1989

Planetary protection and back contamination control for a Mars rover sample return mission

A commitment to avoid the harmful contamination of outer space and avoid adverse changes in the environment of the earth has been long reflected in NASA's Planetary Protection policy. Working under guidelines developed by the Committee on Space Research (COSPAR), NASA has implemented the policy in an interactive process that has included the recommendations of the U.S. National Academy of Sciences. Measures taken to prevent the contamination of earth during the Apollo missions were perhaps the most visible manifestations of this policy, and provided numerous lessons for future sample return opportunities. This paper presents the current status of planetary protection policy within NASA, and a prospectus on how planetary protection issues might be addressed in relation to a Mars Rover Sample Return mission.

Rummel, John D.↗
NASA NTRS1990

PFERD Mission: Pluto Flyby Exploration/Research Design

The Pluto Flyby Exploration/Research Design (PFERD) mission will consist of a flyby spacecraft to Pluto and its satellite, Charon. The mission lifetime is expected to be 18 years. The Titan 4 with a Centaur upper stage will be utilized to launch the craft into the transfer orbit. The proposal was divided into six main subsystems: (1) scientific instrumentation; (2) command, communications, and control: (3) altitude and articulation control; (4) power and propulsion; (5) structures and thermal control; and (6) mission management and costing. Tradeoff studies were performed to optimize all factors of design, including survivability, performance, cost, and weight. Problems encountered in the design are also presented.

Lemke, Gary↗
NASA NTRS2001

Task-Level Control for a Full Semi-Autonomous Mission: Test Platform Development and Demonstration

Pseudolites can extend the availability of GPS-type positioning systems to a wide range of applications not possible with satellite-only GPS, including indoor and deep-space applications. Conventional GPS pseudolite arrays require that the devices be pre-calibrated through a survey of their locations, typically to sub-centimeter accuracy. This can sometimes be a difficult task, especially in remote or hazardous environments. By using the GPS signals that the pseudolites broadcast, however, it is possible to have the array self-survey its own relative locations, creating a Self-Calibrating Pseudolite Array (SCPA). In order to provide the bi-directional ranging signals between devices necessary for array self-calibration, pseudolite transceivers must be used. The basic principles behind the use of transceivers to create an SCPA were first presented in paper presented to the Institute of Navigation GPS-98 Conference. This paper begins with a brief review of the transceiver architecture and the fundamental direct-ranging algorithm presented in that paper. This is followed by a description of a prototype self-differencing transceiver system that has been constructed, and a presentation of experimental code- and carrier-phase ranging data obtained using that system. A second algorithm is then described which uses these fundamental range measurements between transceiver pairs to self-calibrate a larger stationary array and to provide positioning information for a vehicle moving within that array. Simulation results validating the accuracy and effective convergence of this algorithm are also presented.

Rock, Stephen M.↗