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At least 163 records · Page 9
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NASA NTRS2011

Algorithm for Autonomous Landing

Because of their small size, high maneuverability, and easy deployment, micro aerial vehicles (MAVs) are used for a wide variety of both civilian and military missions. One of their current drawbacks is the vast array of sensors (such as GPS, altimeter, radar, and the like) required to make a landing. Due to the MAV s small payload size, this is a major concern. Replacing the imaging sensors with a single monocular camera is sufficient to land a MAV. By applying optical flow algorithms to images obtained from the camera, time-to-collision can be measured. This is a measurement of position and velocity (but not of absolute distance), and can avoid obstacles as well as facilitate a landing on a flat surface given a set of initial conditions. The key to this approach is to calculate time-to-collision based on some image on the ground. By holding the angular velocity constant, horizontal speed decreases linearly with the height, resulting in a smooth landing. Mathematical proofs show that even with actuator saturation or modeling/ measurement uncertainties, MAVs can land safely. Landings of this nature may have a higher velocity than is desirable, but this can be compensated for by a cushioning or dampening system, or by using a system of legs to grab onto a surface. Such a monocular camera system can increase vehicle payload size (or correspondingly reduce vehicle size), increase speed of descent, and guarantee a safe landing by directly correlating speed to height from the ground.

Kuwata, Yoshiaki↗
NASA NTRS2014

Advanced Compatibility Characterization Of AF-M315E With Spacecraft Propulsion System Materials Project

All spacecraft require propulsion systems for thrust and maneuvering. Propulsion systems can be chemical, nuclear, electrical, cold gas or combinations thereof. Chemical propulsion has proven to be the most reliable technology since the deployment of launch vehicles. Performance, storability, and handling are three important aspects of liquid chemical propulsion. Bipropellant systems require a fuel and an oxidizer for propulsion, but monopropellants only require a fuel and a catalyst for propulsion and are therefore simpler and lighter. Hydrazine is the state of the art propellant for monopropellant systems, but has drawbacks because it is highly hazardous to human health, which requires extensive care in handling, complex ground ops due to safety and environmental considerations, and lengthy turnaround times for reusable spacecraft. All users of hydrazine monopropellant must contend with these issues and their associated costs. The development of a new monopropellant, intended to replace hydrazine, has been in progress for years. This project will apply advanced techniques to characterize the engineering properties of materials used in AF-M315E propulsion systems after propellant exposure. AF-M315E monopropellant has been selected HQ's Green Propellant Infusion Mission (GPIM) to replace toxic hydrazine for improved performance and reduce safety and health issues that will shorten reusable spacecraft turn-around time. In addition, this project will fundamentally strengthen JSC's core competency to evaluate, use and infuse liquid propellant systems.

McClure, Mark B.↗
NASA NTRS2015

Lunar Flashlight

The Lunar Flashlight is a Jet Propulsion Laboratory project, with NASA Marshall Space Flight Center (MSFC) serving as the principal investigator and providing the solar sail propulsion system. The goal of Lunar Flashlight is to determine the presence and abundance of exposed lunar water ice within permanently shadowed regions (PSRs) at the lunar south pole, and to map its concentration at the 1-2 kilometer scale to support future exploration and use. After being ejected in cis-lunar space by the launch vehicle, Lunar Flashlight deploys solar panels and an 85-square-meter solar sail and maneuvers into a low-energy transfer to lunar orbit. The solar sail and attitude control system work to bring the satellite into an elliptical polar orbit, spiraling down over a period of 18 months to a perilune of 30-10 kilometers above the south pole for data collection. Lunar Flashlight uses its solar sail to shine reflected sunlight onto the lunar surface, measuring surface reflectance with a four-filter point spectrometer. The spectrometer measures water ice absorption features (1.5, 1.95 microns) and the continuum between them (1.1, 1.9 microns). The ratios of water ice bands to the continuum will provide a measure of the abundance of surface frost and its variability across PSRs. Water ice abundance will be correlated with other data from previous missions, such as the Lunar Reconnaissance Orbiter and Lunar Crater Observation and Sensing Satellite, to provide future human and robotic explorers with a map of potential resources. The mission is enabled by the use of an 85-square-meter solar sail being developed by MSFC.

Baker, John↗
NASA NTRS1994

From Antarctica to space: Use of telepresence and virtual reality in control of remote vehicles

In the Fall of 1993, NASA Ames deployed a modified Phantom S2 Remotely-Operated underwater Vehicle (ROV) into an ice-covered sea environment near McMurdo Science Station, Antarctica. This deployment was part of the antarctic Space Analog Program, a joint program between NASA and the National Science Foundation to demonstrate technologies relevant for space exploration in realistic field setting in the Antarctic. The goal of the mission was to operationally test the use of telepresence and virtual reality technology in the operator interface to a remote vehicle, while performing a benthic ecology study. The vehicle was operated both locally, from above a dive hole in the ice through which it was launched, and remotely over a satellite communications link from a control room at NASA's Ames Research Center. Local control of the vehicle was accomplished using the standard Phantom control box containing joysticks and switches, with the operator viewing stereo video camera images on a stereo display monitor. Remote control of the vehicle over the satellite link was accomplished using the Virtual Environment Vehicle Interface (VEVI) control software developed at NASA Ames. The remote operator interface included either a stereo display monitor similar to that used locally or a stereo head-mounted head-tracked display. The compressed video signal from the vehicle was transmitted to NASA Ames over a 768 Kbps satellite channel. Another channel was used to provide a bi-directional Internet link to the vehicle control computer through which the command and telemetry signals traveled, along with a bi-directional telephone service. In addition to the live stereo video from the satellite link, the operator could view a computer-generated graphic representation of the underwater terrain, modeled from the vehicle's sensors. The virtual environment contained an animate graphic model of the vehicle which reflected the state of the actual vehicle, along with ancillary information such as the vehicle track, science markers, and locations of video snapshots. The actual vehicle was driven either from within the virtual environment or through a telepresence interface. All vehicle functions could be controlled remotely over the satellite link.

Stoker, Carol↗
NASA NTRS2004

A Water Vapor Differential Absorption LIDAR Design for Unpiloted Aerial Vehicles

This system study proposes the deployment of a water vapor Differential Absorption LIDAR (DIAL) system on an Altair unmanned aerial vehicle (UAV) platform. The Altair offers improved payload weight and volume performance, and longer total flight time as compared to other commercial UAV's. This study has generated a preliminary design for an Altair based water vapor DIAL system. The design includes a proposed DIAL schematic, a review of mechanical challenges such as temperature and humidity stresses on UAV deployed DIAL systems, an assessment of the available capacity for additional instrumentation (based on the proposed design), and an overview of possible weight and volume improvements associated with the use of customized electronic and computer hardware, and through the integration of advanced fiber-optic and laser products. The results of the study show that less than 17% of the available weight, less than 19% of the volume capacity, and approximately 11% of the electrical capacity is utilized by the proposed water vapor DIAL system on the Altair UAV.

DeYoung, Russell J.↗
NASA NTRS2009

Deployable Aeroshell Flexible Thermal Protection System Testing

Deployable aeroshells offer the promise of achieving larger aeroshell surface areas for entry vehicles than otherwise attainable without deployment. With the larger surface area comes the ability to decelerate high-mass entry vehicles at relatively low ballistic coefficients. However, for an aeroshell to perform even at the low ballistic coefficients attainable with deployable aeroshells, a flexible thermal protection system (TPS) is required that is capable of surviving reasonably high heat flux and durable enough to survive the rigors of construction handling, high density packing, deployment, aerodynamic loading and aerothermal heating. The Program for the Advancement of Inflatable Decelerators for Atmospheric Entry (PAIDAE) is tasked with developing the technologies required to increase the technology readiness level (TRL) of inflatable deployable aeroshells, and one of several of the technologies PAIDAE is developing for use on inflatable aeroshells is flexible TPS. Several flexible TPS layups were designed, based on commercially available materials, and tested in NASA Langley Research Center's 8 Foot High Temperature Tunnel (8ft HTT). The TPS layups were designed for, and tested at three different conditions that are representative of conditions seen in entry simulation analyses of inflatable aeroshell concepts. Two conditions were produced in a single run with a sting-mounted dual wedge test fixture. The dual wedge test fixture had one row of sample mounting locations (forward) at about half the running length of the top surface of the wedge. At about two thirds of the running length of the wedge, a second test surface drafted up at five degrees relative to the first test surface established the remaining running length of the wedge test fixture. A second row of sample mounting locations (aft) was positioned in the middle of the running length of the second test surface. Once the desired flow conditions were established in the test section the dual wedge test fixture, oriented at 5 degrees angle of attack down, was injected into the flow. In this configuration the aft sample mounting location was subjected to roughly twice the heat flux and surface pressure of the forward mounting location. The tunnel was run at two different conditions for the test series: 1) 'Low Pressure', and 2) 'High Pressure'. At 'Low Pressure' conditions the TPS layups were tested at 6W/cm2 and 11W/cm2 while at 'High Pressure' conditions the TPS layups were tested at 11W/cm2 and 20W/cm2. This paper details the test configuration of the TPS samples in the 8Ft HTT, the sample holder assembly, TPS sample layup construction, sample instrumentation, results from this testing, as well as lessons learned.

Hughes, Stephen J.↗
NASA NTRS2003

Preliminary Design and Analysis of the ARES Atmospheric Flight Vehicle Thermal Control System

The Aerial Regional-scale Environmental Survey (ARES) is a proposed 2007 Mars Scout Mission that will be the first mission to deploy an atmospheric flight vehicle (AFV) on another planet. This paper will describe the preliminary design and analysis of the AFV thermal control system for its flight through the Martian atmosphere and also present other analyses broadening the scope of that design to include other phases of the ARES mission. Initial analyses are discussed and results of trade studies are presented which detail the design process for AFV thermal control. Finally, results of the most recent AFV thermal analysis are shown and the plans for future work are discussed.

Gasbarre, J. F.↗
NASA NTRS2012

Mission Sizing and Trade Studies for Low Ballistic Coefficient Entry Systems to Venus

The U.S and the U.S.S.R. have sent seventeen successful atmospheric entry missions to Venus. Past missions to Venus have utilized rigid aeroshell systems for entry. This rigid aeroshell paradigm sets performance limitations since the size of the entry vehicle is constrained by the fairing diameter of the launch vehicle. This has limited ballistic coefficients (beta) to well above 100 kg/m2 for the entry vehicles. In order to maximize the science payload and minimize the Thermal Protection System (TPS) mass, these missions have entered at very steep entry flight path angles (gamma). Due to Venus thick atmosphere and the steep-gamma, high- conditions, these entry vehicles have been exposed to very high heat flux, very high pressures and extreme decelerations (upwards of 100 g's). Deployable aeroshells avoid the launch vehicle fairing diameter constraint by expanding to a larger diameter after the launch. Due to the potentially larger wetted area, deployable aeroshells achieve lower ballistic coefficients (well below 100 kg/m2), and if they are flown at shallower flight path angles, the entry vehicle can access trajectories with far lower decelerations (~50-60 g's), peak heat fluxes (~400 W/cm2) and peak pressures. The structural and TPS mass of the shallow-gamma, low-beta deployables are lower than their steep-gamma, high-beta rigid aeroshell counterparts at larger diameters, contributing to lower areal densities and potentially higher payload mass fractions. For example, at large diameters, deployables may attain aeroshell areal densities of 10 kg/m2 as opposed to 50 kg/m2 for rigid aeroshells. However, the low-beta, shallow-gamma paradigm also raises issues, such as the possibility of skip-out during entry. The shallow-gamma could also increase the landing footprint of the vehicle. Furthermore, the deployable entry systems may be flexible, so there could be fluid-structure interaction, especially in the high altitude, low-density regimes. The need for precision in guidance, navigation and control during entry also has to be better understood. This paper investigates some of the challenges facing the design of a shallow-gamma, low-beta entry system.

Dutta, Soumyo↗
NASA NTRS1990

Body steered rover

A rough terrain vehicle is described which includes auxiliary wheels that can be deployed to avoid overturning the vehicle when turning while traversing a slope, to climb an embankment or the like, and to right the vehicle when it is overturned. The vehicle includes a pair of front and rear primary wheels, and a pair of auxiliary arms having inner ends pivotally mounted on the front wheel axes and outer ends that carry auxiliary wheels. A motor can turn the arms to move the auxiliary wheels from a stowed position about halfway between the front and rear wheels and above the ground, to a second position against the ground to stabilize the vehicle. The arms can be turned more than 180.degree. to move the auxiliary wheels in front of the front primary wheels to help climb an embankment. The primary wheels can be mounted at the end of primary arms, so when the primary arms are turned they not only move the primary front wheels but also the inner ends of the auxiliary arms.

Collins, Jr., Earl R.↗
NASA NTRS2014

CubeSat Material Limits For Design for Demise

The CubeSat form factor of nano‐satellite (a satellite with a mass between one and ten kilograms) has grown in popularity due to their ease of construction and low development and launch costs. In particular, their use as student led payload design projects has increased due to the growing number of launch opportunities. CubeSats are often deployed as secondary or tertiary payloads on most US launch vehicles or they may be deployed from the ISS. The focus of this study will be on CubeSats launched from the ISS. From a space safety standpoint, the development and deployment processes for CubeSats differ significantly from that of most satellites. For large satellites, extensive design reviews and documentation are completed, including assessing requirements associated with reentry survivability. Typical CubeSat missions selected for ISS deployment have a less rigorous review process that may not evaluate aspects beyond overall design feasibility. CubeSat design teams often do not have the resources to ensure their design is compliant with reentry risk requirements. A study was conducted to examine methods to easily identify the maximum amount of a given material that can be used in the construction of a CubeSats without posing harm to persons on the ground. The results demonstrate that there is not a general equation or relationship that can be used for all materials; instead a limiting value must be defined for each unique material. In addition, the specific limits found for a number of generic materials that have been previously used as benchmarking materials for reentry survivability analysis tool comparison will be discussed.

Kelley, R. L.↗
NASA NTRS2014

CubeSat Material Limits for Design for Demise

The CubeSat form factor of nano-satellite (a satellite with a mass between one and ten kilograms) has grown in popularity due to their ease of construction and low development and launch costs. In particular, their use as student led payload design projects has increased due to the growing number of launch opportunities. CubeSats are often deployed as secondary or tertiary payloads on most US launch vehicles or they may be deployed from the ISS. The focus of this study will be on CubeSats launched from the ISS. From a space safety standpoint, the development and deployment processes for CubeSats differ significantly from that of most satellites. For large satellites, extensive design reviews and documentation are completed, including assessing requirements associated with re-entry survivability. Typical CubeSat missions selected for ISS deployment have a less rigorous review process that may not evaluate aspects beyond overall design feasibility. CubeSat design teams often do not have the resources to ensure their design is compliant with re-entry risk requirements. A study was conducted to examine methods to easily identify the maximum amount of a given material that can be used in the construction of a CubeSats without posing harm to persons on the ground. The results demonstrate that there is not a general equation or relationship that can be used for all materials; instead a limiting value must be defined for each unique material. In addition, the specific limits found for a number of generic materials that have been previously used as benchmarking materials for re-entry survivability analysis tool comparison will be discussed.

Kelley, R. L.↗
NASA NTRS2013

Arcjet Testing of Woven Carbon Cloth for Use on Adaptive Deployable Entry Placement Technology

This paper describes arcjet testing and analysis that has successfully demonstrated the viability of three dimensional woven carbon cloth for dual use in the Adaptive Deployable Entry Placement Technology (ADEPT). ADEPT is an umbrella-like entry system that is folded for stowage in the launch vehicle s shroud and deployed in space prior to reaching the atmospheric interface. A key feature of the ADEPT concept is its lower ballistic coefficient for delivery of a given payload than those for conventional, rigid body entry systems. The benefits that accrue from the lower ballistic coefficient include factor of ten reductions of deceleration forces and entry heating. The former enables consideration of new classes of scientific instruments for solar system exploration while the latter enables the design of a more efficient thermal protection system. The carbon cloth now base lined for ADEPT has a dual use in that it serves as ADEPT s thermal protection system and as the "skin" that transfers aerodynamic deceleration loads to its umbrella-like substructure. The arcjet testing described in this paper was conducted for some of the higher heating conditions for a future Venus mission using the ADEPT concept, thereby showing that the carbon cloth can perform in a relevant entry environment. The ADEPT project considered the carbon cloth to be mission enabling and was carrying it as a major risk during Fiscal Year 2012. The testing and analysis reported here played a major role in retiring that risk and is highly significant to the success and possible adoption of ADEPT for future NASA missions. Finally, this paper also describes a preliminary engineering level code, based on the arcjet data, that can be used to estimate cloth thickness for future missions using ADEPT and to predict carbon cloth performance in future arcjet tests.

Arnold, James O.↗
NASA NTRS2013

Viability of 3 D Woven Carbon Cloth and Advanced Carbon-Carbon Ribs for Adaptive Deployable Entry Placement Technology (ADEPT) for Future NASA Missions

This paper describes aerothermodynamic and thermal structural testing that demonstrate the viability of three dimensional woven carbon cloth and advanced carbon-carbon (ACC) ribs for use in the Adaptive Deployable Entry Placement Technology (ADEPT). ADEPT is an umbrella-like entry system that is folded for stowage in the launch vehicle's shroud and deployed prior to reaching the atmeopheric interface. A key feature of the ADEPT concept is a lower ballistic coefficient for delivery of a given payload than seen with conventional, rigid body entry systems. The benefits that accrue from the lower ballistic coefficient incllude factor-of-ten reductions of deceleration forces and entry heating. The former enables consideration of new classes of scientific instruments for solar system exploration while the latter enables the design of a more efficient thermal protection system. The carbon cloth base lined for ADEPT has a dual use in that it serves as the thermal protection system and as the "skin" that transfers aerdynamic deceleration loads to its umbrella-like substructure. Arcjet testing described in this paper was conducted for some of the higher heating conditions for a future Venus mission using the ADEPT concept, thereby showing that the carbon cloth can perform in a relevant entry environment. Recently completed the thermal structural testing of the cloth attached to a representative ACC rib design is also described. Finally, this paper describes a preliminary engineering level code, based on the arcjet data, that can be used to estimate cloth thickness for future ADEPT missions and to predict carbon cloth performance in future arcjet tests.

ADEPT↗
NASA NTRS1992

Tethers and their role in the Space Exploration Initiative

This paper addresses some potential applications for tethers in space, and describes a mission designed to deploy a satellite from a Delta II launch vehicle, by NASA's Small Expendable Deployer System, via a 46 km long tether. The mission, targeted for 1993, will contribute to the U.S. Space Exploration Initiative, and along with the shuttle flight of the tethered satellite system, TSS1, will be one of the first attempts to experimentally characterize the dynamics of a tethered system. Data taken from two experimental packages onboard the satellite will be analyzed to verify mathematical simulations related to tether dynamics.

Bankston, Cheryl D.↗
NASA NTRS1993

Evolving directions in NASA's planetary rover requirements and technology

This paper reviews the evolution of NASA's planning for planetary rovers (i.e. robotic vehicles which may be deployed on planetary bodies for exploration, science analysis, and construction) and some of the technology that has been developed to achieve the desired capabilities. The program is comprised of a variety of vehicle sizes and types in order to accommodate a range of potential user needs. This includes vehicles whose weight spans a few kilograms to several thousand kilograms; whose locomotion is implemented using wheels, tracks, and legs; and whose payloads vary from microinstruments to large scale assemblies for construction. We first describe robotic vehicles, and their associated control systems, developed by NASA in the late 1980's as part of a proposed Mars Rover Sample Return (MRSR) mission. Suggested goals at that time for such an MRSR mission included navigating for one to two years across hundreds of kilometers of Martian surface; traversing a diversity of rugged, unknown terrain; collecting and analyzing a variety of samples; and bringing back selected samples to the lander for return to Earth. Subsequently, we present the current plans (considerably more modest) which have evolved both from technological 'lessons learned' in the previous period, and modified aspirations of NASA missions. This paper describes some of the demonstrated capabilities of the developed machines and the technologies which made these capabilities possible.

Weisbin, C. R.↗
NASA NTRS1993

Evolving directions in NASA's planetary rover requirements and technology

The evolution of NASA's planning for planetary rovers (that is robotic vehicles which may be deployed on planetary bodies for exploration, science analysis, and construction) and some of the technology that was developed to achieve the desired capabilities is reviewed. The program is comprised of a variety of vehicle sizes and types in order to accommodate a range of potential user needs. This includes vehicles whose weight spans a few kilograms to several thousand kilograms; whose locomotion is implemented using wheels, tracks, and legs; and whose payloads vary from microinstruments to large scale assemblies for construction. Robotic vehicles and their associated control systems, developed in the late 1980's as part of a proposed Mars Rover Sample Return (MRSR) mission, are described. Goals suggested at the time for such a MRSR mission included navigating for one to two years across hundreds of kilometers of Martian surface; traversing a diversity of rugged, unknown terrain; collecting and analyzing a variety of samples; and bringing back selected samples to the lander for return to Earth. Current plans (considerably more modest) which have evolved both from technological 'lessons learned' in the previous period, and modified aspirations of NASA missions are presented. Some of the demonstrated capabilities of the developed machines and the technologies which made these capabilities possible are described.

Weisbin, C. R.↗
NASA NTRS1995

Human Exploration and Settlement of the Moon Using LUNOX-Augmented NTR Propulsion

An innovative trimodal nuclear thermal rocket (NTR) concept is described which combines conventional liquid hydrogen (LH2)-cooled NTR, Brayton cycle power generation and supersonic combustion ramjet (scramjet) technologies. Known as the liquid oxygen (LOX) augmented NTR (LANTR), this concept utilizes the large divergent section of the NTR nozzle as an 'afterburner' into which LOX is injected and supersonically combusted with nuclear preheated hydrogen emerging from the LANTR's choked sonic throat--'scramjet propulsion in reverse.' By varying the oxygen-to-hydrogen mixture ratio (MR), the LANTR can operate over a wide range of thrust and specific impulse (Isp) values while the reactor core power level remains relatively constant. As the MR varies from zero to seven, the thrust-to-weight ratio for a 15 thousand pound force (klbf) NTR increases by approximately 440%--from 3 to 13--while the Isp decreases by only approximately 45%--from 940 to 515 seconds. This thrust augmentation feature of the LANTR means that 'big engine' performance can be obtained using smaller more affordable, easier to test NTR engines. 'Reoxidizing' the bipropellant LANTR system in low lunar orbit (LLO) with high density 'lunar-derived' LOX (LUNOX) enables a reusable, reduced size and mass lunar transfer vehicle (LTV) which can be deployed and resupplied using two 66 t-class Shuttle-derived launch vehicles. The reusable LANTR can also transport 200 to 300% more payload on each piloted round trip mission than an expendable 'all LH2' NTR system. As initial outposts grow to eventual lunar settlements and LUNOX production capacity increases, the LANTR concept can also enable a rapid 'commuter' shuttle capable of 36 to 24 hour 'one way' trips to the Moon and back with reasonable size vehicles and initial mass in low Earth orbit (IMLEO) requirements.

Borowski, Stanley K.↗
NASA NTRS2023

On-Board Deployment Event Verification for GOES-R Spacecraft

As is common with many spacecraft designs, the GOES-R vehicles require a series of deployment events to transition from the launch configuration to the operational configuration. Rather than implementing additional sensors to verify various deployments, the GOES-R program developed an alternate approach that uses existing gyro rate sensing. The approach includes two pieces: the first is a new onboard shock detection capability to confirm initiation of individual deployment events, and the second is a ground-based dynamics verification step to confirm completion of deployment events. We first present the algorithm that detects shock events for various deployment devices along with the parameter tuning performed during ground tests. We then show inflight performance of the shock detection algorithm. While shock detection is useful for observing initiation of deployment events, completion of some deployment events cannot be determined by shock detection alone. For these events, such as solar panel latch-up and deployable boom extension, the program developed dynamics models for the deployment transient responses. High-rate gyro data were recorded for these events, which allow the ground team to verify that the appendages were fully deployed. We show the predictive models for these events and corresponding flight results.

GeoXO↗