Advanced onboard propulsion benefits and status

Future commercial space systems may include geosynchronous-orbit communication satellites; Earth-observing satellites in polar, sun-synchronous orbits; and tended low-earth-orbit platforms. All such space systems require onboard propulsion for a variety of functions, including stationkeeping and drag makeup, apogee motors, and delivery and return. In many cases, the onboard propulsion exerts a major influence on the overall mission performance, lifetime, and integration. NASA has established a Low Thrust Propulsion Program, which is developing chemical and electric propulsion concepts that offer potential for significant benefits for onboard propulsion for the various classes of commercial spacecraft. The onboard propulsion requirements of future commercial space systems are briefly discussed, followed by a summary of the characteristics and status of relevant elements of the NASA Low Thrust program

The long memory model of political support: some further results

This paper extends the results of Byers, Davidson and Peel (1997) on long memory in support for the Conservative and Labour Parties in the UK using longer samples and additional poll series. It finds continuing support for the ARFIMA(0,d,0) model though with somewhat smaller values of the long memory parameter. We find that the move to telephone polling in the mid-1990s has no apparent effect on the estimated value of d for either party. Finally, we find that we cannot reject the hypotheses that the parties share a common long memory parameter which we estimate at around 0.65.

International Rostrum of Composers 1983

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The NASA Electric Propulsion Program

The NASA OAST Propulsion, Power, and Energy Division supports an electric propulsion program aimed at providing benefits to a broad class of missions. Concepts which have the potential to enable or significantly benefit space exploration and exploitation are identified and advanced toward application in the near and far term. This paper summarizes recent program progress in mission/system analysis; in electrothermal, electrostatic, and electromagnetic propulsion technologies; and in propulsion/spacecraft integration

Homogenous Learning Styles Among Airport Management Professionals

Research on the career paths of airport management professionals included an assessment of learning styles to better understand the psychological profile of those in this career field. The Kolb Learning Styles Inventory, Version 3 (LSI-3) was used for the study for participants to self-assess their preferences for learning. General research on the validity and reliability of the (LSI-3) indicates that a roughly equal number of the general population categorize themselves in one out of four categories (Accommodators, Assimilators, Convergers, or Divergers). In the research involving airport management professionals, more than two-thirds of the respondents categorized themselves as Divergers. Another 22% categorized themselves as Accommodators. With almost 90% of the sample population represented within two of the four LSI groups, the evidence strongly suggests that airport management professionals prefer to learn by carefully evaluating definitive outcomes in a social environmental as opposed to action-based experimentation. Curiously, these results are diametrically opposite of similar research for another aviation related career path - military pilots, most of whom (44.2%) categorized themselves as Convergers (Kanske, 1999). This research may have implications in aviation education, particularly for recognizing that some students in collegiate aviation programs may have learning styles that are aligned with airport management professionals as opposed to other technically oriented aviation careers (e.g., commercial pilot). This understanding may be helpful in counseling students, particularly those struggling to find an aviation career path that better fits their preferred learning environment

Investigation of Ba, BaO, Sr and SrO Pulsed Laser-Induced Vapor Plumes in N2, O2, Microwave Discharged O2, and Vacuum at Low Laser Fluence

Ba, BaO, Sr and SrO were ablated by 248 nm laser pulses at fluences ranging from 270 mJ-/sq cm to 575 mJ-/sq cm in vacuum and in 25 mtorr atmospheres of N2, O2 and microwave-discharged O2. The spectral emissions of these plumes were compared for indications of ionization due to Ba or Sr collisions with each gas. The addition of a background gas increased the ion and neutral signature across the spectrum. SrO band emission was observed at 16,600-16,900/cm and possible BaO band emissions were observed in the 18,250-18,400/cm, 19,000-19700/cm and 19,800-20,000/cm regions. A screened plate ion probe was use to establish the ion content of the Ba plume. A time of flight study established low-pressure (1 to 35 mtorr) and low-fluence (40 to 160 mJ-/sq cm relationships on Ba(+) velocity and population. Observed ion velocities ranged from 3.1 km/sec. To 4.5 km/sec. Results indicate the addition of a background gas at pressures less than 25 mtorr quenches Ba(+) in the plume and retards the plume expansion

Support for Governments and Leaders: Fractional Cointegration Analysis of Poll Evidence from the UK, 1960-2004

Revised draft, July 2005Two versions of a fractionally cointegrating vector error correction model (FVECM) are presented. In the case of regular cointegration, linear combinations of fractionally integrated variables are integrated to lower order. Generalized cointegration is defined as the case where the cointegrating variables may be fractional differences of the observed series. The concepts are applied to a model of poll data on approval of the performance of prime ministers and governments in the UK