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NASA NTRS1994

Orion: Design of a system for assured low-cost human access to space

In recent years, Congress and the American people have begun to seriously question the role and importance of future manned spaceflight. This is mainly due to two factors: a decline in technical competition caused by the collapse of communism, and the high costs associated with the Space Shuttle transportation system. With these factors in mind, the ORION system was designed to enable manned spaceflight at a low cost, while maintaining the ability to carry out diverse missions, each with a high degree of flexibility. It is capable of performing satellite servicing missions, supporting a space station via crew rotation and resupply, and delivering satellites into geosynchronous orbit. The components of the system are a primary launch module, an upper stage, and a manned spacecraft capable of dynamic reentry. For satellite servicing and space station resupply missions, the ORION system utilizes three primary modules, an upper stage, and the spacecraft, which is delivered to low earth orbit and used to rendezvous, transfer materials, and make repairs. For launching a geosynchronous satellite, one primary module and an upper stage are used to deliver the satellite, along with an apogee kick motor, into orbit. The system is designed with reusability and modularity in mind in an attempt to lower cost.

Elvander, Josh↗

NASA NTRS1995

ORION: A Supersynchronous Transfer Orbit mission

ORION F1 was launched on 29th November 1994 on an Atlas IIA launch vehicle. It was designed, built and delivered in-orbit by Matra Marconi Space Systems Plc and was handed over to ORION Satellite Corporation on 20th January 1995 at its on-station longitude of 37.5 deg W. The mission differed significantly from that of any other geostationary communications satellite in that the Transfer Orbit apogee altitude of 123,507 km was over three times geosynchronous (GEO) altitude and one third of the way to the moon. The SuperSynchronous Transfer Orbit (SSTO) mission is significantly different from the standard Geostationary Transfer Orbit (GTO)mission in a number of ways. This paper discusses the essential features of the mission design through its evolution since 1987 and the details of the highly successful mission itself including a detailed account of the attitude determination achieved using the Galileo Earth and Sun Sensor (ESS).

Walters, I. M.↗

NASA NTRS1993

The spectrum of Orion-KL at 2 millimeters (150-160 GHz)

A spectral survey of Orion-KL has been carried out in the 2 mm atmospheric window in the frequency range 149.6-159.6 GHz, using the FCRAO 14 m telescope. Typical sensitivities achieved were T(sub A sup *) approximately 0.03-0.1 K, peak-to-peak. Over 180 spectral lines were detected, including approximately 45 unidentified features. The spectra were measured with a single-sideband receiver and, even at levels of T(sub A sup *) approximately 30 mK, are far from being confusion-limited. Fifteen known species were conclusively identified in Orion in this spectral region, with the largest numbers of lines arising from methyl formate, ethyl cyanide, methanol, and dimethyl ether. These species have beam-averaged column densities of N(sub tot) approximately 0.5-8 x 10(exp 15)/sq cm. Several other species have been tentatively observed, including acetaldehyde, C2S, and possibly EtOH. The large organic species, however, appear to arise from different regions. For example, CH3CCH and (CH3)2O come primarily from the extended ridge, while EtCN and VyCN exclusively arise in the hot core. This survey clearly demonstrates that the 2 mm window is rich in spectral lines. It also suggests there is much chemical selectivity in the formation of large organic interstellar molecules.

Ziurys, L. M.↗

NASA NTRS1995

Gamma-ray lines from the Orion complex

We show that the 4.44 and 6.13 MeV line emission observed with the Compton Telescope (COMPTEL) from Orion is consistent with gamma-ray spectra consisting of a mixture of narrow and broad lines or spectra containing only broad lines. We employed several accelerated particle compositions and showed that the current COMPTEL data in the 3-7 MeV region alone cannot distinguish between the various possibilities. However, the COMPTEL upper limits in the 1-3 MeV band favor a composition similar to that of the winds of Wolf-Rayet stars of spectral type WC. The power dissipated by the accelerated particles at Orion is about 4 x 10(exp 38) ergs/s. These particles are not expected to produce significant amounts of Al-26.

Ramaty, Reuven↗

NASA NTRS1994

The abundance of interstellar oxygen toward Orion: Evidence for recent infall?

We present high S/N (greater than 800) Goddard High-Resolution Spectrograph (GHRS) observations of the weak interstellar O I lambda 1356 absorption in the low-density sight lines toward iota Ori and kappa Ori. By comparing these data with observations toward more reddened stars, we find no evidence of density-dependent depletion from the gas phase for oxygen. The derived total oxygen abundance (gas plus grains) towards iota Ori and kappa Ori is consistent with stellar and nebular determinations in Orion at a level that is one-half the solar value. We speculate that the O/H abundance ratio is lower in Orion compared to the Sun because the local Milky Way has suffered a recent infall of metal-poor material, perhaps from the Magellanic Stream.

Meyer, David M.↗

NASA NTRS1995

Deep ROSAT HRI observations of the Orion nebula region

We present results from three deep ROSAT high-resolution imager observations of the Orion Nebula star-forming region. The X-ray images contain over 1500 cataloged stars in a roughly 0.8 sq deg region centered on the Trapezium. In all, 389 distinct X-ray sources have been detected, at least two-thirds of which are associated with a single proper-motion cluster member. X-ray emission is detected from stars of all spectral types, from massive O- and B-type components of the Trapezium to the coolest, low-mass pre-main-sequence (PMS) stars. In this paper we focus primarily on X-ray emission from the late-type PMS stars. Of the approximately 100 late-type cluster members with measured spectral types, approximately three-fourths have been detected; we have derived X-ray luminosity upper limits for the remaining stars. We found coronal X-ray emission turns on around spectral type F6, with the upper envelope of activity increasing with deceasing effective temperature. When plotted in an X-ray luminosity versus bolometric luminosity diagram, late-type PMS stars lie below a 'saturation' line corresponding to L(sub x)/L(sub bol) approximately 10(exp -3). For approximately solar-mass PMS stars, we find a median X-ray luminosity approximately 1 x 10(exp 30) ergs/s. The late G, K, and M stars exhibit nearly a two order of magnitude spread in X-ray luminosity and in L(sub x)/L(sub bol) at a given effective temperature. Plots of X-ray activity versus v sin i rotational velocity and rotational period appear to show no clear dependence of activity on rotation. However, because only a small fraction of late-type PMS stars in the Orion Nebula have measured v sin i or P(sub rot) and because of uncertainties in L(sub x) and L(sub x)/L(sub bol), we believe the data are not conclusive on this point. Light curves of the detected X-ray sources have revealed at least 10 strong X-ray flares with characteristic rise times greater than or approximately equal to 1 hr and decay times ranging from approximately 2 to 12 hr. All the flares have X-ray energies in excess of 3 x 10(exp 35) ergs. Many of the X-ray sources associated with late-type cluster members have been observed in more than one ROSAT HRI exposure, allowing us to look for variability on the approximately 1 yr timescale between HRI observations. A statistical analysis of the resulting count rate ratios suggests that at least one-fourth of the late-type cluster stars are significantly variable on this timescale.

Gagne, Marc↗

NASA NTRS1995

KWIC imaging of the Orion Nebula

We present the first results obtained with our new imaging Fabry-Perot spectrometer, KWIC. We obtained a fully sampled 9.8 sec. spatial resolution image of the inner 8 min. x 12 min. region of the Orion Nebula in the 37 micro m continuum and a somewhat smaller scale image in the (SiII) 35 micro m line. The continuum image traces out the structure of the interface region between the molecular cloud and the Orion A HII region, as well picking out embedded sources such as the BN-KL star cluster. The continuum directly yields the luminosity of the sources and is used to deduce dust mass and grain parameters. Our (SiII) image both reveals the clumpy structure of the interface region and signals the presence of a dissociative J-shock in the high velocity outflow from IRc2.

Stacey, G. J.↗

NASA NTRS1996

Physical Conditions in Low Ionization Regions of the Orion Nebula

We reexamine the spectroscopic underpinnings of recent claims that low ionization (O(I)) and (Fe(II)) lines from the Orion H(II) region are produced in a region where the iron-carrying grains have been destroyed and the electron density is surprisingly high. Our new HST and CTIO observations show that previous reported detections of(O(I)) lambda 5577 were strongly affected by telluric emission. Our line limits consistent with a moderate density (approx. 10(exp 4)/cu. cm photoionized gas. We show that a previously proposed model of the Orion H(II) region reproduces the observed (O(I)) and (Fe(II)) spectrum. These lines are fully consistent with formation in a moderate density dusty region.

Baldwin, J. A.↗

NASA NTRS1996

ORION Low Cost Laser Analysis

We show that laser-target interaction physics demands the shortest laser pulse of which hardware is capable (but not less than 100 ps) in the ORION ground-based laser concept. We compare two leading ways to achieve such pulses - SRS/SBS cascade compression and grating compression - with the standard MOPA approach, and conclude that the first of these is most robust. However, the state of the art in laser devices will require a year or two to implement these ideas. We present a pulse format and beam footprint protocol which will solve the conflict between relativistic lookahead and beam tilt and should permit all-laser active acquisition and tracking in ORION.

Phipps, Claude R.↗

NASA NTRS1995

A Rapidly Moving Shell in the Orion Nebula

A well-resolved elliptical shell in the inner Orion Nebula has been investigated by monochromatic imaging plus high- and low-resolution spectroscopy. We find that it is of low ionization and the two bright ends are moving at -39 and -49 km/s with respect to OMC-1. There is no central object, even in the infrared J bandpass although H2 emission indicates a possible association with the nearby very young pre-main-sequence star J&W 352, which is one of the youngest pre-main-sequence stars in the inner Orion Nebula. Many of the characteristics of this object (low ionization, blue shift) are like those of the Herbig-Haro objects, although the symmetric form would make it an unusual member of that class.

Walter, Donald K.↗

NASA NTRS1996

ROSAT observations of the Orion-Eridanus superbubble

The Orion-Eridanus bubble is a superbubble created by the Orion OB1 stellar association. The X-ray emission from the interior of this bubble forms a prominent feature of the soft X-ray diffuse background extending across approximately 20 x 35 deg. The Rosat all sky survey maps of this object show various soft X-ray shadows cast by neutral foreground clouds against the bright emission of the superbubble interior. The velocities of some of these absorbing clouds were identified and distance limits were established, providing a 3D model of the bubble. The data are consistent with a model for the bubble in which the structure is formed by stellar winds and a recent supernova. Absorption features associated with the shell of the local bubble were identified which enable constraints to be placed on the distance and direction and to obtain measurement of the thermal pressure of the hot gas in this direction.

Burrows, David N.↗

NASA NTRS1993

Anatomy of the Photodissociation Region in the Orion Bar

Much of the interstellar gas resides in photodissociation regions whose chemistry and energy balance is controlled by the flux of far-ultraviolet radiation upon them. These photons can ionize and dissociate molecules and heat the gas through the photoelectric effect working on dust grains. These regions have been extensively modeled theoretically, but detailed observational studies are few. Mapping of the prominent Orion Bar photo-dissociation region at wavelengths corresponding to the carbon-hydrogen stretching mode of polycyclic aromatic hydrocarbons, the 1-0 S(l) line of molecular hydrogen, and the J = 1-0 rotational line of carbon monoxide allows the penetration of the far-ultraviolet radiation into the cloud to be traced. The results strongly support the theoretical models and show conclusively that the incident far-ultraviolet radiation field, not shocks as has sometimes been proposed, is responsible for the emission in the Orion Bar.

Tielens, A. G. G. M.↗

NASA NTRS1998

Midcourse Space Experiment Spectra of the Orion Nebula and the Implications for Abundances in the Interstellar Medium

Spectra of the Orion Nebula were obtained with the Midcourse Space Experiment Spirit 3 interferometer from 370 to 2000 cm(exp -1) with 2 cm(exp -1) resolution in a 6' x 9' field of view (FOV) in 1996 November. Lines were detected of [S III] 534.4 cm(exp -1), [Ne III] 642.9 cm(exp -1), [Ne II] 780.4 cm(exp -1), [S IV] 951.4 cm(exp -1), [Ar III] 1112.2 cm(exp -1), [Ar II] 1431.6 cm(exp -1), H (7-6) 808.3 cm(exp -1), H (8-6) 1332.9 cm(exp -1), H (6-5) 1340.5 cm(exp -1), H2(S1) 587.0 cm(exp -1), H2(S2) 814.4 cm(exp -1), H2(S3) 1034.7 cm(exp -1), H2(S4) 1246.1 cm(exp -1), and H2(S5) 1447.3 cm(exp -1). The following abundances were determined from these lines: Ne/H = 9.9 +/- 1.1 x 10(exp -5), S/H = 8.1 +/- 1.1 x 10(exp -6), and Ar/H = 2.5 +/- 0.2 x 10(exp -6). These abundances are all less than solar and confirm that the Sun is overabundant in heavy elements without the need for correction for the composition of interstellar dust. The low sulfur abundance compared with solar is an indication that a significant amount of the sulfur in Orion is in dust grains. The FOV-averaged molecular hydrogen column density is approximately 1.6 x 10(exp 20) cm(exp -2) for an excitation temperature of approximately 670 K and an extinction correction corresponding to an optical depth of 1.5 at 9.7 micrometers. The unidentified infrared emission features at 6.2, 7.7, 8.6, 11.3, and 12.7 micrometers, attributable to polycyclic aromatic hydrocarbons, were also detected. A prominent, broad silicate feature centered near 18 micrometer and additional weak features were detected and are discussed.

Simpson, J. P.↗

NASA NTRS1999

EGRET Observations of the Diffuse Gamma-Ray Emission in Orion: Analysis Through Cycle 6

We present a study of the high-energy diffuse emission observed toward Orion by the Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma-Ray Observatory. The total exposure by EGRET in this region has increased by more than a factor of two since a previous study. A simple model for the diffuse emission adequately fits the data; no significant point sources are detected in the region studied (1 = 195 deg to 220 deg and b = -25 deg to -10 deg) in either the composite dataset or in two separate groups of EGRET viewing periods considered. The gamma-ray emissivity in Orion is found to be (1.65 +/- 0.11) x 10(exp -26)/s.sr for E > 100 MeV, and the differential emissivity is well-described as a combination of contributions from cosmic-ray electrons and protons with approximately the local density. The molecular mass calibrating ratio is N(H2)/W(sub CO) = (1.35 +/- 0.15) x 10(exp 20)/sq cm.(K.km/s).

Digel, S. W.↗

NASA NTRS1998

Thermal Water Vapor Emission from Shocked Regions in Orion

Using the Long Wavelength Spectrometer on board the Infrared Space Observatory, we have observed thermal water vapor emission from a roughly circular field of view approximately 75" in diameter centered on the Orion BN-KL region. The Fabry-Perot line strengths, line widths, and spectral line shifts observed in eight transitions between 71 and 125 micron show good agreement with models of thermal emission arising from a molecular cloud subjected to a magnetohydrodynamic C-type shock. Both the breadth and the relative strengths of the observed lines argue for emission from a shock rather than from warm quiescent gas in the Orion core. Although one of the eight transitions appears anomalously strong and may be subject to the effects of radiative pumping, the other seven indicate an H2O/H2 abundance ratio on the order of 5 x 10(exp -4) and a corresponding gas-phase oxygen-to-hydrogen abundance ratio on the order of 4 x 10(exp -4). Given current estimates of the interstellar, gas-phase, oxygen and carbon abundances in the solar vicinity, this value is consistent with theoretical shock models that predict the conversion into water of all the gas-phase oxygen that is not bound as CO. The overall cooling provided by rotational transitions of H2O in this region appears to be comparable to the cooling through rotational lines of CO but is an order of magnitude lower than cooling through H2 emission. However, the model that best fits our observations shows cooling by H2O and CO dominant in that portion of the postshock region where temperatures are below approximately 800 K and neither vibrational nor rotational radiative cooling by H2 is appreciable.

Harwitt, Martin↗

NASA NTRS2000

Nuclear Pulse Propulsion: Orion and Beyond

The race to the Moon dominated manned space Fight during the 1960's. and culminated in Project Apollo. which placed 12 humans on the Moon Unbeknownst to the public at that time, several U.S. Government agencies sponsored a project that could have conceivably, placed 150 people on the Moon and eventually sent crewed expeditions to Mars and the outer Planets. These feats could have possibly been accomplished during, the same period of time as Apollo. and for approximately the same cost. The project. code-named Orion. featured an extraordinary propulsion method known n as Nuclear Pulse The concept is probably as radical today as t was at the down of the space age. However its development appeared to he so promising that it was only by Political and non-technical considerations that it was not used to extend humanity reach throughout the solar system and quite possible to the stars. This paper discusses the rationale for nuclear pulse propulsion and presents a general history of the concept. focusing particularly on Project Orion. It describes some of the reexaminations being done in this area and discusses some of the new ideas that could mitigate many of the political and environmental issues associated with the concept.

Schmidt, George R.↗

NASA NTRS1994

Imaging of the PAH Emission Bands in the Orion Bar

The infrared spectrum of many planetary nebulae, HII regions, galactic nuclei, reflection nebulae, and WC stars are dominated by a set of narrow and broad features which for many years were called the "unidentified infrared bands". These bands have been attributed to several carbon-rich molecular species which all contain only carbon and hydrogen atoms, and fall into the class of PAH molecules or are conglomerates of PAH skeletons. If these bands are from PAHs, then PAHs contain 1-10% of the interstellar carbon, making them the most abundant molecular species in the interstellar medium after CO. From ground based telescopes, we have studied the emission bands assigned to C-H bond vibrations in PAHs (3.3, 11.3 microns) in the Orion Bar region, and showed that their distribution and intensities are consistent with a quantitative PAH model. We have recently obtained spectral images of the Orion Bar from the KAO at 6.2 and 7.7 microns using a 128 x 128 Si:Ga array camera in order to study the C-C modes of the PAH molecules. We will show these new data along with our existing C-H mode data set, and make a quantitative comparison of the data with the existing PAH model.

Bregman, Jesse↗

NASA NTRS2004

ORION-II: A True Formation Flying Mission in LEO

The final report for the Orion-II project is taken from Chapter 5 of "CDGPS-Based Relative Navigation for Multiple Spacecraft," a thesis by Megan Mitchell submitted to the MIT Department of Aeronautics and Astronautics, June 2004. This chapter begins with a comparison of the simulation architecture for the original and current simulation setups. Next, the changes made to the individual components of the navigation system are described. Finally, tests performed with a Spirent Simulator at NASA Goddard Space Flight Center (GSFC) are discussed. In addition to the development of the testbed components described, a new clean room facility was developed in the Orion Laboratory at MIT.

How, Jonathan P.↗