Engineering topics

Stearns, J. W.

Publications and source records attributed to Stearns, J. W..

17 records

NASA NTRS1986

Alkali metal/halide thermal energy storage systems performance evaluation

A pseudoheat-pipe heat transfer mechanism has been demonstrated effective in terms of both total heat removal efficiency and rate, on the one hand, and system isothermal characteristics, on the other, for solar thermal energy storage systems of the kind being contemplated for spacecraft. The selection of appropriate salt and alkali metal substances for the system renders it applicable to a wide temperature range. The rapid heat transfer rate obtainable makes possible the placing of the thermal energy storage system around the solar receiver canister, and the immersing of heat transfer fluid tubes in the phase change salt to obtain an isothermal heat source.

Phillips, W. M.↗

NASA NTRS1985

Advanced latent heat of fusion thermal energy storage for solar power systems

The use of solar thermal power systems coupled with thermal energy storage (TES) is being studied for both terrestrial and space applications. In the case of terrestrial applications, it was found that one or two hours of TES could shift the insolation peak (solar noon) to coincide with user peak loads. The use of a phase change material (PCM) is attractive because of the higher energy storage density which can be achieved. However, the use of PCM has also certain disadvantages which must be addressed. Proof of concept testing was undertaken to evaluate corrosive effects and thermal ratcheting effects in a slurry system. It is concluded that the considered alkali metal/alkali salt slurry approach to TES appears to be very viable, taking into account an elimination of thermal ratcheting in storage systems and the reduction of corrosive effects. The approach appears to be useful for an employment involving temperatures applicable to Brayton or Stirling cycles.

Phillips, W. M.↗

NASA NTRS1981

High performance solar Stirling system

A full-scale Dish-Stirling system experiment, at a power level of 25 kWe, has been tested during 1981 on the Test Bed Concentrator No. 2 at the Parabolic Dish Test Site, Edwards, CA. Test components, designed and developed primarily by industrial contractors for the Department of Energy, include an advanced Stirling engine driving an induction alternator, a directly-coupled solar receiver with a natural gas combustor for hybrid operation and a breadboard control system based on a programmable controller and standard utility substation components. The experiment demonstrated practicality of the solar Stirling application and high system performance into a utility grid. This paper describes the design and its functions, and the test results obtained.

Stearns, J. W.↗

NASA NTRS1980

An interstellar precursor mission

A mission out of the planetary system, launched about the year 2000, could provide valuable scientific data as well as test some of the technology for a later mission to another star. Primary scientific objectives for the precursor mission concern characteristics of the heliopause, the interstellar medium, stellar distances (by parallax measurements), low-energy cosmic rays, interplanetary gas distribution, and the mass of the solar system. Secondary objectives include investigation of Pluto. The mission should extend to 400-1000 AU from the sun. A heliocentric hyperbolic escape velocity of 50-100 km/sec or more is needed to attain this distance within a reasonable mission duration (20-50 years). The trajectory should be toward the incoming interstellar gas. For a year 2000 launch, a Pluto encounter and orbiter can be included. A second mission targeted parallel to the solar axis would also be worthwhile. The mission duration is 20 years, with an extended mission to a total of 50 years. A system using one or two stages of nuclear electric propulsion (NEP) was selected as a possible baseline. The most promising alternatives are ultralight solar sails or laser sailing, with the lasers in earth orbit, for example. The NEP baseline design allows the option of carrying a Pluto orbiter as a daughter spacecraft.

Jaffe, L. D.↗

NASA NTRS1979

Aerospace power systems - A building surge

Dramatic changes in both aircraft and space power systems are being projected. The primary driver is mission cost, although more stringent performance requirements are also being imposed. The order-of-magnitude reductions anticipated in space power, both in cost and specific mass, are partially related to the advent of the Shuttle and the continuing evolution of the STS over the next decade. Automation, microcircuitry, batteries, and structural materials are common aircraft and space technology needs.

Barthelemy, R. R.↗

NASA NTRS1978

Space power systems technology enablement study

The power system technologies which enable or enhance future space missions requiring a few kilowatts or less and using the space shuttle were assessed. The advances in space power systems necessary for supporting the capabilities of the space transportation system were systematically determined and benefit/cost/risk analyses were used to identify high payoff technologies and technological priorities. The missions that are enhanced by each development are discussed.

Smith, L. D.↗

NASA NTRS1977

An interstellar precursor mission

A mission out of the planetary system, with launch about the year 2000, could provide valuable scientific data as well as test some of the technology for a later mission to another star. Primary scientific objectives for the precursor mission concern characteristics of the heliopause, the interstellar medium, stellar distances (by parallax measurements), low energy cosmic rays, interplanetary gas distribution, and mass of the solar system. Secondary objectives include investigation of Pluto. Candidate science instruments are suggested. Individual spacecraft systems for the mission were considered, technology requirements and problem areas noted, and a number of recommendations made for technology study and advanced development. The most critical technology needs include attainment of 50-yr spacecraft lifetime and development of a long-life NEP system.

Jaffe, L. D.↗

NASA NTRS1976

Large-payload earth-orbit transportation with electric propulsion

Economical unmanned earth orbit transportation for large payloads is evaluated. The high exhaust velocity achievable with electric propulsion is attractive because it minimizes the propellant that must be carried to low earth orbit. Propellant transport is a principal cost item. Electric propulsion subsystems utilizing advanced ion thrusters are compared to magnetoplasmadynamic (MPD) thrust subsystems. For very large payloads, a large lift vehicle is needed to low earth orbit, and argon propellant is required for electric propulsion. Under these circumstances, the MPD thruster is shown to be desirable over the ion thruster for earth orbit transportation.

Stearns, J. W.↗

NASA NTRS1975

Status report on nuclear electric propulsion systems

Progress in nuclear electric propulsion (NEP) systems for a multipayload multimission vehicle needed in both deep-space missions and a variety of geocentric missions is reviewed. The space system power level is a function of the initial launch vehicle mass, but developments in out-of-core nuclear thermionic direct conversion have broadened design options. Cost, design, and performance parameters are compared for reusable chemical space tugs and NEP reusable space tugs. Improvements in heat pipes, ion engines, and magnetoplasmadynamic arc jet thrust subsystems are discussed.

Stearns, J. W.↗

NASA NTRS1973

Multi-mission nuclear electric propulsion stage design.

Results of a mission engineering analysis of nuclear-thermionic electric propulsion spacecraft for unmanned interplanetary and geocentric missions. Critical technologies assessed are associated with the development of nuclear electric propulsion (NEP), and the impact of its availability on future space programs. Specific areas of investigation include outer planet and comet rendezvous mission analysis, NEP stage design for geocentric and interplanetary missions, and technology requirements for NEP stage development. A multimission NEP stage can be developed to perform both multiple geocentric and interplanetary missions for a 1983 launch. Identified pacing NEP technology requirements are the development of 20,000 full power hour ion thrustors and thermionic reactor and the development of related power conditioning. The resulting NEP stage design provides both inherent reliability and high payload mass capability.

Prickett, W. Z.↗

NASA NTRS1972

Elements of cost comparison for planetary missions with advanced propulsion

Cost and performance comparisons are made between chemical propulsion and nuclear electric propulsion for planetary missions at Jupiter and beyond. Nuclear rocket comparisons are made for performance only. Titan, Saturn, and space shuttle launch are evaluated, utilizing advanced propulsion upper stages. Appendixes include a performance analysis of multiple shuttle launches, with assembly in earth orbit, and a discussion of nonrecurring costs.

Stearns, J. W.↗

NASA NTRS1966

Solar-Powered Electric Propulsion Systems: Engineering and Applications

Lightweight, multikilowatt solar power arrays in conjunction with electric propulsion offer potential improvements to space exploration, extending the usefulness of existing launch vehicles to higher-energy missions. Characteristics of solar-powered electric propulsion missions are outlined, and preliminary performance estimates are shown. Spacecraft system engineering is discussed with respect to parametric trade-offs in power and propulsion system design. Relationships between mission performance and propulsion system performance are illustrated. The present state of the art of electric propulsion systems is reviewed and related to the mission requirements identified earlier. The propulsion system design and test requirements for a mission spacecraft are identified and discussed. Although only ion engine systems are currently available, certain plasma propulsion systems offer some advantages in over-all system design. These are identified, and goals are set for plasma-thrustor systems to make them competitive with ion-engine systems for mission applications.

Stearns, J. W.↗

NASA NTRS1965