Concepts
Cross-cutting material: a subject that is not one machine, one component, one facility or one destination, and that would otherwise be restated on every page it bears on.
Environment references collects the documents hardware is designed against rather than measured by. The Cross-Program Design Specification for Natural Environments converts environment models into the design values a US deep space program’s requirements inherit [1], and the page lists the Lunar Sourcebook, the Global Reference Atmospheric Model series for Mars, Venus, Titan and the giant planets, and the galactic cosmic ray and orbital debris models behind shielding mass alongside it. The destinations as measured are under Environments.
Tethers is here because a tether belongs to no single vehicle class: it carries the vehicle’s weight during a rappel, its power and its data at once, and what governs it is breaking force at the bend and temperature it is actually pulled over rather than a single rating. One lunar surface power tether broke at 7219 N over a gentle bend at -190 C and at 990 N over a 78 degree knife edge at +200 C [2].
A page belongs here when its subject spans destinations and vehicle classes. A part with a published flight or qualification result belongs on Avionics, something that runs on a processor on Software, a laboratory on test facilities, and a destination’s own properties on Environments.
References
- Roberts, B. C. (2017). SLS-SPEC-159 Cross-Program Design Specification for Natural Environments (DSNE) Revision E
. NASA Marshall Space Flight Center. Source
BibTeX
@techreport{nasa2017sls, title = {SLS-SPEC-159 Cross-Program Design Specification for Natural Environments (DSNE) Revision E}, author = {Roberts, Barry C.}, institution = {NASA Marshall Space Flight Center}, year = {2017}, url = {https://ntrs.nasa.gov/citations/20170008140}, abstract = {The DSNE completes environment-related specifications for architecture, system-level, and lower-tier documents by specifying the ranges of environmental conditions that must be accounted for by NASA ESD Programs. To assure clarity and consistency, and to prevent requirements documents from becoming cluttered with extensive amounts of technical material, natural environment specifications have been compiled into this document. The intent is to keep a unified specification for natural environments that each Program calls out for appropriate application. This document defines the natural environments parameter limits (maximum and minimum values, energy spectra, or precise model inputs, assumptions, model options, etc.), for all ESD Programs. These environments are developed by the NASA Marshall Space Flight Center (MSFC) Natural Environments Branch (MSFC organization code: EV44). Many of the parameter limits are based on experience with previous programs, such as the Space Shuttle Program. The parameter limits contain no margin and are meant to be evaluated individually to ensure they are reasonable (i.e., do not apply unrealistic extreme-on-extreme conditions). The natural environments specifications in this document should be accounted for by robust design of the flight vehicle and support systems. However, it is understood that in some cases the Programs will find it more effective to account for portions of the environment ranges by operational mitigation or acceptance of risk in accordance with an appropriate program risk management plan and/or hazard analysis process. The DSNE is not intended as a definition of operational models or operational constraints, nor is it adequate, alone, for ground facilities which may have additional requirements (for example, building codes and local environmental constraints). "Natural environments," as the term is used here, refers to the environments that are not the result of intended human activity or intervention. It consists of a variety of external environmental factors (most of natural origin and a few of human origin) which impose restrictions or otherwise impact the development or operation of flight vehicles and destination surface systems.} } - Goddu, A., Jin, C., Caballero, M., Botteon, K., Wright, M., Barchowsky, A. and Brown, T. (2024). TetherCAD: A Python library to aid in the design of Electromechanical Tethers and Tethered Systems for applications in Robotics and Spacecraft
. Mars Exploration Program Analysis Group. Source
BibTeX
@inproceedings{goddu2024tethercad, title = {TetherCAD: A Python library to aid in the design of Electromechanical Tethers and Tethered Systems for applications in Robotics and Spacecraft}, author = {Goddu, Austen and Jin, Curtis and Caballero, Matthew and Botteon, Kyle and Wright, M. and Barchowsky, Ansel and Brown, T.}, booktitle = {Mars Exploration Program Analysis Group}, publisher = {JPL Open Repository}, year = {2024}, doi = {10.48577/jpl.bfesih}, abstract = {Tethered robotics offer unique potential to access and operate in harsh terrain and provide power and communication for exploration and infrastructure on the Moon and Mars. The tether is the lifeline for these systems, allowing robots to access impassable terrain features, maintaining power and communication. Their criticality stipulates that they must be designed to survive the harsh environments, while enduring the mechanical and electrical constraints of the systems which deploy them. Designers must perform complex trades to create tethers for their missions, balancing system performance requirements against mass and volume to create viable tethered robotics systems. This paper discusses TetherCAD: a set of tools to aid in high-level design and performance analysis of tethers. TetherCAD helps users create tether solutions that meet their system's unique needs, incorporating length, voltage, losses, power transfer, communications, tensile strength and minimum bend radius to generate tethers that can be fabricated from standard products and are viable for the Lunar and Martian environments. It presents a tether designed using the tools, along with the results of tensile testing over various bend radii and abrasion testing in vacuum, both over a range of Lunar temperatures.} }