Engineering topics

Loftus, Joseph P., Jr.

Publications and source records attributed to Loftus, Joseph P., Jr..

13 records

NASA NTRS1999

Orbital Debris: A Chronology

This chronology covers the 37-year history of orbital debris concerns. It tracks orbital debris hazard creation, research, observation, experimentation, management, mitigation, protection, and policy. Included are debris-producing, events; U.N. orbital debris treaties, Space Shuttle and space station orbital debris issues; ASAT tests; milestones in theory and modeling; uncontrolled reentries; detection system development; shielding development; geosynchronous debris issues, including reboost policies: returned surfaces studies, seminar papers reports, conferences, and studies; the increasing effect of space activities on astronomy; and growing international awareness of the near-Earth environment.

Portree, Davis S. F.↗

NASA NTRS1993

Orbital debris and near-Earth environmental management: A chronology

This chronology covers the 32-year history of orbital debris and near-Earth environmental concerns. It tracks near-Earth environmental hazard creation, research, observation, experimentation, management, mitigation, protection, and policy-making, with emphasis on the orbital debris problem. Included are the Project West Ford experiments; Soviet ASAT tests and U.S. Delta upper stage explosions; the Ariane V16 explosion, U.N. treaties pertinent to near-Earth environmental problems, the PARCS tests; space nuclear power issues, the SPS/orbital debris link; Space Shuttle and space station orbital debris issues; the Solwind ASAT test; milestones in theory and modeling the Cosmos 954, Salyut 7, and Skylab reentries; the orbital debris/meteoroid research link; detection system development; orbital debris shielding development; popular culture and orbital debris; Solar Max results; LDEF results; orbital debris issues peculiar to geosynchronous orbit, including reboost policies and the stable plane; seminal papers, reports, and studies; the increasing effects of space activities on astronomy; and growing international awareness of the near-Earth environment.

Portree, David S. F.↗

NASA NTRS1992

Orbital debris minimization and mitigation techniques

Man's activity in space has generated significant amounts of debris that remain in orbit for periods of sufficient duration to become a hazard to future space activities. Upper stages and spacecraft that have ended their functional life are the largest objects. In the past, additional debris has been generated by inadvertent explosions of upper stages and spacecraft, by intentional explosions for military reasons, and possibly by a few breakups resulting from collisions. In the future, debris can be generated by collisions among spacecraft as the number of orbital objects continues to grow at rates greater than natural forces remove them from orbit. There are design and operations practices that can minimize the inadvertent generation of debris. There are other design and operations options for removing objects from space at the end of their useful service so they are not available as a source for the generation of future debris. Those studies are the primary concern of this paper. The most economic removal of objects is achieved when those objects have the capability to execute the necessary maneuvers with their own systems and resources. The most costly option is to have some other system remove the spacecraft after it has become a derelict. Numerous options are being studied to develop systems and techniques that can remove spacecraft from useful orbits at the end of their useful life and do so for the least mass penalty and economic cost.

Loftus, Joseph P., Jr.↗

NASA NTRS1991

Techniques for debris mitigation

Techniques for space debris abatement and removal are discussed. Characteristics of the total debris population and the low Earth orbit population are illustrated. Self disposal options that utilize propulsion maneuvers and drag augmentation devices are described. The active retrieval and disposition of large debris objects by collection with a maneuverable space vehicle are discussed. The removal of small debris by using a solar reflector to melt particles or by destruction with high energy laser devices is discussed.

Loftus, Joseph P., Jr.↗

NASA NTRS1991

An Outlook for the Twenty First Century as to Launch Operations, Facilities, and Systems

A discussion of launch systems for the 21st century is presented. The following launch systems are mentioned: the European Ariane family; the Japanese H-1 and H-2; the U.S.'s Titan, Delta, Atlas, and Space Shuttle; the Chinese Long March 4; and the USSR's Mir, Proton, and Zenit. Systems currently under investigation, including the Assured Crew Return Vehicle, Personnel Launch Systems, and Single Stage to Orbit (SSTO), are discussed. Automated operations, low Earth orbit, and reliability are addressed. Standards that were acceptable for ballistic missiles will not be acceptable for future launch vehicles. The achievement of significantly higher levels of reliability is seen as the challenge.

Loftus, Joseph P., Jr.↗

NASA NTRS1991

Management of the orbital environment

Data regarding orbital debris are presented to shed light on the requirements of environmental management in space, and strategies are given for active intervention and operational strategies. Debris are generated by inadvertent explosions of upper stages, intentional military explosions, and collisional breakups. Design and operation practices are set forth for minimizing debris generation and removing useless debris from orbit in the low-earth and geosynchronous orbits. Self-disposal options include propulsive maneuvers, drag-augmentation devices, and tether systems, and the drag devices are described as simple and passive. Active retrieval and disposition are considered, and the difficulty is examined of removing small debris. Active intervention techniques are required since pollution prevention is more effective than remediation for the problems of both earth and space.

Loftus, Joseph P., Jr.↗

NASA NTRS1990

The evolution of the Space Shuttle

As the mission manifest develops in response to the needs of the users, new capabilities are being developed for the Shuttle. Other changes are being introduced in order to provide Assured Shuttle Availability (ASA), that is, safe efficient flight operations into the 21st century. These changes will provide simpler turnaround processing procedures, enhanced subsystem reliability, a reduction in critical failure modes, and enhanced operational flexibility.

Cohen, Aaron↗

NASA NTRS1990

United States studies in orbital debris - Prevention and mitigation

Debris in space has become an issue that has commanded considerable interest in recent years as society has become both more dependent upon space based systems, and more aware of its dependence. After many years of study the United States Space Policy of February 1988 directed that all sectors of the U.S. community minimize space debris. Other space organizations have adopted similar policies. Among the study activities leading to the policy and to subsequent implementing directives were discussions with the ESA, NASDA, and other space operating agencies. The policy derived from technical consensus on the nature of the issues and upon the courses of action available to mitigate the problem, but there remains the concern as to the adequacy of the data to define cost effective strategies. There are now in place mechanisms to continue technical discussions in more formal terms.

Loftus, Joseph P., Jr.↗

NASA NTRS1990

U.S. studies in orbital debris

The combined effect of the natural meteoroid flux and the man-made debris on future space operations is discussed. The radar and optical systems used to study orbital debris are examined with special attention given to the Haystack Debris Observation Project and the Haystack radar at Millstone Hill, which is being modified to enable it to observe the regions of interest to the Space Station. Consideration is also given to techniques designed to remove objects from space.

Loftus, Joseph P., Jr.↗

NASA NTRS1989

Future space transportation requirements for the management of orbital debris

Launch vehicle upper stages continue to contribute to future orbital debris scenarios whenever they undergo explosive propulsion system failures, as well as by remaining on orbit as potential collision targets for smaller orbiting bodies. No active measures have been instituted to date in order to remove nonfunctional satellites or spent rocket stages from earth orbit; they are nevertheless conceivable, and classifiable as (1) orbital-maneuvering retrieval; (2) self-disposal; and (3) propulsive deorbit or atmospheric drag augmentation. Illustrative cases and parametric assessments of these methods' feasibility and cost are presented.

Petro, Andrew J.↗

NASA NTRS1989

Reliability and cost considerations in launch vehicles

The inherent reliability of a space launch system, or lack thereof, is pointed out to often be a more significant determinant of access to orbit than the nominal cost. System improvements that enhance inherent reliability may accordingly represent the most economical approach to follow. At some point, the limitations of launch technologies currently in use must be acknowledged and novel methods developed. The dearth of systematic research efforts toward superior technology in launcher propulsion over the last 20 years is identified as a major limitation in the search for near-term options.

Loftus, Joseph P., Jr.↗

NASA NTRS1989

Orbital debris from upper-stage breakup

The present conference on the effects of launch vehicle upper-stage breakup on the orbital debris scenario discusses an analysis of the SPOT 1 Ariane third stage, the explosive fragmentation of orbiting propellant tanks, albedo estimates for debris, Ariane-related debris in deep-space orbit, and the relationship of hypervelocity impacts to upper-stage breakups. Also discussed are the prospects for and the economics of the future removal of orbital debris, collision probabilities in GEO, current operational practices for Delta second stage breakup prevention, breakup-precluding modifications to the Ariane third stage, and the safing of the H-1 second stage after spacecraft separation.

Loftus, Joseph P., Jr.↗

NASA NTRS1987

Space Station initiates permanent space facility development

The proposed development of the Space Station is examined. The functions and advantages of the Space Station are described. The use of a solar array system for power generation on the Station is studied; the capabilities of various other generation systems are also evaluated. The Space Station's development schedule is discussed.

Loftus, Joseph P., Jr.↗