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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Recommendations for a 1979 Mariner Jupiter-Uranus mission are discussed with the possibility of launching the first outer planet atmospheric entry probe. Measurement categories considered for the mission include conducting imaging experiments, observations in both the IR and UV spectral range, experiments associated with magnetic fields, plasma, charged particles, and S- and X-band occultation measurements.
The feasibility of an outer planet common atmospheric probe is studied with emphasis on entry heating rates and improved ephemeris. It is concluded that a common probe design is possible except for Jupiter; the basic technology exists except for Jupiter heat shielding. A Mariner class bus provides for better bus science and probe bus communications than a Pioneer class bus.
The summary provides descriptions for a set of probes designed to explore an inner rather than an outer planet, and designed to survive to 100 bars rather than 10 bars. The probes carry a variety of scientific instruments and their supporting integrated subsystems are adjusted to Venus environmental conditions.
Factors influencing the design of an outer planet probe heat shield are discussed. Major factors included are: uncertainties in composition and scale height of the planet atmospheres; the augmentation/attenuation of entry heating by ablation products requires more computer study and testing; carbon heat shields, especially carbon phenolic, possessing improved resistance to spallation need developing; and white silica reflecting heat shields with improved resistance to bulk vitrification need further developing.
The performance of silica heat shields in the outer planet atmospheres is analyzed and described in a set of differential equations. Results are presented and discussed.
Atmospheric structure of outer planets as determined by pressure, temperature, and accelerometers is reviewed and results obtained from the PAET earth entry are given. In order to describe atmospheric structure, entry is divided into two regimes, high and low speed. Acceleration is then measured: from these measurements density is determined as a function of time. The equations of motion are integrated to determine velocity, flight path angle, and altitude as a function of time. Density is then determined as a function of altitude from the previous determinations of density and altitude as a function of time. Hydrostatic equilibrium was assumed to determine pressure as a function of altitude. Finally the equation of space applied to determine temperature as a function of altitude, if the mean molecular weight is known. The mean molecular weight is obtained independently from either the low speed experiment or from the composition experiments.
A digital simulation study is presented for a candidate modulator/demodulator design in an atmospheric scintillation environment with Doppler, Doppler rate, and signal attenuation typical of the conditions of an outer planet atmospheric probe. The simulation results indicate that the mean channel error rate with and without scintillation are similar to theoretical characterizations of the link. The simulation gives information for calculating other channel statistics and generates a quantized symbol stream on magnetic tape from which error correction decoding is analyzed. Results from the magnetic tape data analyses are also included. The receiver and bit synchronizer are modeled in the simulation at the level of hardware component parameters rather than at the loop equation level and individual hardware parameters are identified. The atmospheric scintillation amplitude and phase are modeled independently. Normal and log normal amplitude processes are studied. In each case the scintillations are low pass filtered. The receiver performance is given for a range of signal to noise ratios with and without the effects of scintillation. The performance is reviewed for critical reciever parameter variations.
The feasibility of a Jovian entry by a probe originally designed for Saturn and Uranus entries is examined. An entry probe is described which is capable of release near an outer planet's sphere of influence and descent to a predetermined target entry point in the planet's atmosphere. The probe is designed so as to survive the trapped particle radiation belts and an entry heating pulse. Data is gathered and relayed to an overflying spacecraft bus during descent. Probe variations for two similar missions are described. In the first flyby of Jupiter by a Pioneer spacecraft launched during the 1979 opportunity is examined parametrically. In the second mission an orbiter based on Pioneer and launched in 1980 is defined in specific terms. The differences rest in the science payloads and directly affected wiring and electronics packages.
The Planetary Mission Model, NASA's program of future solar system exploration for the years 1973-1990, is presented. The model is based on a continuation of the balanced exploration philosophy, tempered by a conception of the realities of technology availability and fiscal constraints. It envisions the continued use of existing spacecraft technology (i.e., Mariner, Viking, and Pioneer) with only evolutionary changes, but with the introduction of atmospheric probe technology in the late 70's. The Titan/Centaur vehicle would be in use through 1980, and solar-electric propulsion (SEP) capability would be introduced in about 1979. Beyond 1980, shuttle capability is assumed. A brief explanation of the rationale behind the sequences at the following targets is presented: Mercury, Venus, Mars, the outer planets, and comets and asteroids.
In 1977 NASA will launch two spacecraft to perform scientific investigations of the Jupiter and Saturn planetary systems. The science payload includes a total of ten instruments to support both the interplanetary-cruise and planetary-encounter phases. These will be the first launches of a new generation of Mariner-class spacecraft designed for outer-planet missions. The telemetry-system design for these missions was especially challenging because of extreme communication ranges (1.5 billion km), high data-rate requirements (up to 115.2 kbit/sec), and more stringent data-quality requirements than previous Mariner missions. The present paper discusses the evolution and design of the Mariner Jupiter/Saturn 1977 telemetry system and presents the performance anticipated therefrom.
It is planned to use the SEPS as the upper stage of a transportation system capable of delivering either a separable payload spacecraft or an attached science package to a host of planetary targets including inner and outer planets, asteroids, and comets. It may also be employed in earth orbit to deliver and retrieve payloads in geosynchronous orbit. An investigation is conducted regarding the use of the SEPS for a relatively high energy out-of-ecliptic mission planned for 1980. Parametric performance data for the mission are considered along with trajectory characteristics, launch vehicle performance, and SEPS performance.
A high purity slip cast silica material has been developed for use as a reflective heat shield for entries into the atmospheres of the outer planets. The several stages leading to the development of this material are described and details of raw material selection, preparation of the slip material and casting techniques are discussed. Optical (reflectance and transmittance), physical and chemical properties measurements were performed as a function of the important material and processing variables. Performance analysis of a reflective heat shield fabricated from the high purity silica slip shows that approximately 90 percent of the radiant bow shock energy incident on the heat shield during entry into the atmosphere of Jupiter will be reflected.
In order to prepare for the era of autonomous navigation, this paper first examines existing techniques for spacecraft navigation by describing the basic elements of the Mark-I and II navigation technologies. The remainder of the paper deals with identification of criteria which necessitate onboard navigation, and with promising solutions now under consideration. An attractive solution possibility is proposed which utilizes narrow-angle optics, a charge-coupled device area-array image sensor, a small advanced onboard flight computer, and a simplified set of software algorithms. Onboard commands would be derived and sent to the appropriate spacecraft attitude control, propulsion, and science platform pointing subsystems. The proposed autonomous navigation system does not address all mission options, but focuses primarily on precision approach trajectory control and adaptive science instrument pointing for asteroid, cometary, and outer planet satellite missions.
Planetary-orbit mission capabilities will be greatly improved by the advent of space-storable retropropulsion systems with liquid fluorine and hydrazine as bipropellants even when the Shuttle/Tug is used as launch vehicle. Having a specific impulse as large as 375 sec, a multimission propulsion module using space-storable propellants with Pioneer or Mariner spacecraft as payload can perform Mercury, Saturn, and Uranus orbiter missions, and even some comet rendezvous missions, more cost effectively and flexibly than one using earth-storable propellants. It also can reduce trip time to the outer planets significantly. This paper presents mission requirements, technology status, system design and performance, development schedules, and costs based on data derived in a recent design and feasibility study.
In addition to the outer planets, much interest is directed toward understanding the solar environment in which those planets and the earth have evolved. One means of obtaining some of the needed data is an out-of-the-ecliptic mission. Direct launch out of earth orbit does not allow acceptable solar latitudes to be achieved with existing launch vehicles. This paper presents the results of a study on using a Jupiter swingby to increase significantly the achievable solar latitudes. Latitudes above 60 deg can be achieved with an Atlas/Centaur/TE364-4 and a Pioneer-class spacecraft reduced in weight by about 50 kg. Jovian center-targeting contours have been generated, and a maximum achievable latitude has been determined as a function of launch year and spacecraft mass. Nominal trajectories are selected, and time histories of significant parameters are presented.
The feasibility of conducting Space Shuttle-launched earth entry flight tests to enhance the technology base for second generation planetary entry missions is examined. Outer planet entry environments are reviewed, translated into earth entry requirements and used to establish entry test system design and cost characteristics. Entry speeds up to those needed to simulate radiative heating levels of more than 30 kW/sq cm are shown to be possible. A standardized recoverable test bed concept is described that is capable of accommodating a wide range of entry technology experiments. The economic advantage of shared Shuttle launches are shown to be achievable through a test system configured to the volume constraints of a single Spacelab pallet using existing propulsion components.
This paper describes the NASA/ERDA research and technology program that was initiated in mid-FY 1974 with the objective of doubling the efficiency of thermionic power conversion with decreased emitter temperature. Also discussed are the potential uses of thermionic power conversion systems. Emphasis in this paper is placed on potential space applications, especially nuclear-electric propulsion (NEP). Possible development schedules are shown that would allow NEP systems to be ready for use in the 1990 time period for missions to the outer planets.
The impact of satisfying satellite quarantine on current outer planet mission and spacecraft designs was determined and the tools required to perform trajectory and navigation analyses for determining satellite impact probabilities were developed.