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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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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

A halo-orbit lunar station.

A relay satellite following a halo trajectory will always maintain line-of-sight contact with the earth and the moon's far side. The Integrated Program Plan for lunar exploration in the 1980s and beyond calls for a fully reusable earth-moon transportation system. The principal elements of the system are a Translunar Shuttle, a Lunar-Orbit Space Station or Halo-Orbit Space Station, and a Lunar Space Tug. It is shown that a halo-orbit space station could offer important operational and performance advantages compared to a lunar-orbit station in a second-generation lunar program.

Farquhar, R. W.↗
NASA NTRS1980

Potentialities of lunar laser range - Differencing for measuring the earth's orientation

An investigation of range differences for their capabilities in determining the orientation of the earth in an earth-moon reference system is presented. Each pair of two coobserving stations forms an observational unit which is preferably located along a meridian or parallel; for a time interval from the instant of the first simultaneous observation of the most eastern line to the last observation of the most western line, a variance analysis shows that the pole position and the earth rotation can be computed independently of errors in the adopted lunar ephemeris. It is concluded that if the stations are within 10 to 15 deg in north-south or east-west direction the standard deviations of the parameters do not increase significantly.

Leick, A.↗
NASA NTRS1962

Regenerative Environmental Control Systems for Manned-Lunar Spacecraft

The historic earth orbital flight of the Mercury space capsule on February 20, 1962 has illustrated that man has the capability of creating instrumentation and equipment which permit him to survive outside the protective earth atmosphere which, in time, has served both as a shield and a barrier. Because of this great achievement man need no longer restrict himself to earth-space but may direct his resources to expand his zone of operation to earth-moon space. However, in order to exploit this new frontier many problems must be solved which are not mere extensions or extrapolations of those already treated. The problem associated with providing man with an adequate environment for extended periods in the earth's atmosphere, earth-moon space and on the lunar surface is indeed extensive. Trapped radiation, solar flare activity, meteoroid bombardment, solar radiation and the hard vacuum of space are no longer merely phenomena. of scientific interest; they describe the operating environment of manned earth-lunar spacecraft. In order that man may effectively operate in the earth-moon space, myriads of systems and subsystems of varying types and functions must be devised and integrated into an efficient, reliable man-machine complex. This paper will consider only one small aspect of this problem--that is, the problem of providing man with an adequate gaseous and thermal environment in earth-lunar spacecraft. Control of atmospheric gases in manned sealed environments will be treated in Part I. Part II treats thermal regulation and atmosphere control requirements of mobile life support systems for lunar exploration.

Control↗
NASA NTRS1975

A uniformly valid solution for motion about the interior libration point of the perturbed elliptic-restricted problem

Bounded motion about Lagrange collinear libration points is considered for a perturbed elliptic-restricted problem. A practical application is the motion of a satellite near a libration point collinear with the sun and the earth-moon barycenter. Such a system is treated here as an earth-sun-satellite elliptic restricted problem with lunar perturbations. The method of dual time scales is utilized to develop a uniformly valid three-dimensional analytical solution to the satellite's equations of motion. The analytical development applies somewhat generally to that class of four-body problems where the second primary mass is much greater than the first, and the third primary mass is much greater than the second.

Richardson, D. L.↗
NASA NTRS1967

Systems analysis

Selenodesy experiment, data compression, Mars and Venus mass data, Earth-Moon mass ratio, orbits for three-body problem, and unbraked impact time for lunar landing mission - systems analyses

THREE-BODY PROBLEM↗
NASA NTRS1980

Doubly-periodic orbits in the Sun-Earth-Moon system

A series of periodic orbits in the Earth-Moon circular restricted problem of three bodies was found which is ideally suited for exploring the Earth's geomagnetic tail. The mean apsidal motion of the basic highly elliptical Earth orbit was maintained at about one degree per day by a sequence of lunar swingbys, keeping the apogees in the anti-Sun direction. The orbits were periodic in reference frames rotating at both lunar and solar rates. Apogee distances were alternately raised and lowered by the lunar swingby maneuvers. Several categories of these Sun-synchronous double lunar swingby orbits were identified. The strength and flexibility of this trajectory concept was demonstrated with real world simulations.

Farohar, R.↗
NASA NTRS1972

Comments on the figure of the moon from Apollo landmark tracking.

The selenographic positions of the observed lunar features are solved for, or estimated directly from, angular measurements made from the orbiting spacecraft (Apollo missions 8, 10, 11, 12, 14, and 15) to the landmark, using least-squares techniques. It appears that the radius values derived from the Apollo landmark data provide some proof of the existence of a displacement between the center of figure and center of mass of the moon along the earth-moon line. In addition, all three components of the estimated crater locations should be useful toward establishing a selenodetic reference system for interpreting or reducing earth-based observation data.

Wollenhaupt, W. R.↗
NASA NTRS1981

Electromagnetic-gravitational energy systems

Two methods are considered to 'tap' the earth's rotational energy. This ancient 'collapsed gravitational energy' exceeds the earth-lunar binding energy. One involves an orbiting 'electromagnetic-gravitational' coupling system whereby the earth's rotation, with its nonuniform mass distribution, first uses gravity to add orbital energy to a satellite, similar to a planetary 'flyby'. The second stage involves enhanced satellite 'drag' as current-carrying coils withdraw the added orbital energy as they pass through the earth's nonuniform magnetic field. A second more direct method couples the earth's rotational motion using conducting wires moving through the noncorotating part (ionospheric current systems) of the geomagnetic field. These methods, although not immediately feasible, are considerably more efficient than using pure gravitational coupling to earth-moon tides.

Schatten, K. H.↗
NASA NTRS1981

The influence of cosmological gravitational waves on a Newtonian binary system

The interaction of a continuous gravitational wave with a Newtonian binary system is discussed, and the possibility of using the orbital perturbations to detect cosmological gravitational waves is investigated. The response of the binary system is dominated at late times by secular terms that appear in the orbital perturbations. The dominant secular terms are calculated, and it is shown that they can be used to put interesting upper limits on the energy density of cosmological gravitational waves. In particular, the recent studies of the Earth-Moon and Earth-Mars distances tentatively limit the energy density of the waves, in units of the closure density, to be less than 10 and 0.05 for incoherent waves with periods of 1 month and 1 year, respectively. The possibility of existence of cosmological waves with these periods is discussed.

Mashhoon, B.↗
NASA NTRS1983

Modal control of an unstable periodic orbit

Floquet theory is applied to the problem of designing a control system for a satellite in an unstable periodic orbit. Expansion about a periodic orbit produces a time-periodic linear system, which is augmented by a time-periodic control term. It is shown that this can be done such that (1) the application of control produces only inertial accelerations, (2) positive real Poincareexponents are shifted into the left half-plane, and (3) the shift of the exponent is linear with control gain. These developments are applied to an unstable orbit near the earth-moon L(3) point pertubed by the sun. Finally, it is shown that the control theory can be extended to include first order perturbations about the periodic orbit without increase in control cost.

Wiesel, W.↗