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Cohen, L.

Publications and source records attributed to Cohen, L..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Side forces on a tangent ogive forebody with a fineness ratio of 3.5 at high angles of attack and Mach numbers from 0.1 to 0.7

An experimental investigation was conducted in the Ames 12-Foot Wind Tunnel to determine the subsonic aerodynamic characteristics, at high angles of attack, of a tangent ogive forebody with a fineness ratio of 3.5. The investigation included the effects of nose bluntness, nose strakes, nose booms, a simulated canopy, and boundary-layer trips. The forebody was also tested with a short afterbody attached. Static longitudinal and lateral-directional stability data were obtained at Reynolds numbers ranging from 0.3 mil. to 3.8 mil. (based on base diameter) at a Mach number of 0.25, and at a Reynolds number of 0.8 mil. at Mach numbers ranging from 0.1 to 0.7. Angle of attack was varied from 0 to 88 deg at zero sideslip, and the sideslip angle was varied from -10 to 30 deg at angles of attack of 40, 55, and 70 deg.

Keener, E. R.↗
NASA NTRS1977

Side forces on forebodies at high angles of attack and Mach numbers from 0.1 to 0.7: two tangent ogives, paraboloid and cone

An experimental investigation was conducted in the Ames 12-Foot Wind Tunnel to determine the subsonic aerodynamic characteristics of four forebodies at high angles of attack. The forebodies tested were a tangent ogive with fineness ratio of 5, a paraboloid with fineness ratio of 3.5, a 20 deg cone, and a tangent ogive with an elliptic cross section. The investigation included the effects of nose bluntness and boundary-layer trips. The tangent-ogive forebody was also tested in the presence of a short afterbody and with the afterbody attached. Static longitudinal and lateral/directional stability data were obtained. The investigation was conducted to investigate the existence of large side forces and yawing moments at high angles of attack and zero sideslip. It was found that all of the forebodies experience steady side forces that start at angles of attack of from 20 deg to 35 deg and exist to as high as 80 deg, depending on forebody shape. The side is as large as 1.6 times the normal force and is generally repeatable with increasing and decreasing angle of attack and, also, from test to test. The side force is very sensitive to the nature of the boundary layer, as indicated by large changes with boundary trips. The maximum side force caries considerably with Reynolds number and tends to decrease with increasing Mach number. The direction of the side force is sensitive to the body geometry near the nose. The angle of attack of onset of side force is not strongly influenced by Reynolds number or Mach number but varies with forebody shape. Maximum normal force often occurs at angles of attack near 60 deg. The effect of the elliptic cross section is to reduce the angle of onset by about 10 deg compared to that of an equivalent circular forebody with the same fineness ratio. The short afterbody reduces the angle of onset by about 5 deg.

Keener, E. R.↗
NASA NTRS1977

Chromospheric limb spectra from Skylab - 2000 to 3200 A

Chromospheric limb spectra of a quiet-sun region between 2000 and 3200 A recorded by the normal-incidence spectrograph on Skylab are discussed. The spectral resolution is 0.12 A, and the projected slit area on the sun is 2 by 60 arcsec. A list of lines with wavelengths, identifications, and absolute intensities is given for the spectrum recorded at +4 arcsec outside the white-light limb. The intensity behavior outside the limb is shown for lines of the ions C II, Si II, Cr II, Mn II, Fe II, Fe III, Co II, and Ni II. The widths of the intersystem lines of Si II and C II increase monotonically with height above the limb. The full width at half-maximum of the Si II lines increases from 0.034 A at the limb to 0.27 A at +12 arcsec above the limb. The widths of the C II lines increase from 0.17 A at +2 arcsec to 0.31 A at +12 arcsec.

Doschek, G. A.↗
NASA NTRS1976

Wavelengths and levels of the Na I isoelectronic sequence from K IX through Mn XV

The seven spectra K IX through Mn XV have been analyzed and the series limits determined. We present the adopted wavelengths and the derived energy levels and term splittings. The highly ionized atoms were produced in a spark source and recorded mainly on a 3 m grazing incidence spectrograph. Many new lines have been identified and many previously given wavelengths have been revised. All wavelengths have been examined for consistency by least-squares-fitting procedures and other tests. These procedures indicated misidentified lines and incorrect wavelengths which we corrected when possible. A discussion of the errors is given.

Cohen, L.↗
NASA NTRS1976

Transitions of Zn XXII, Zn XXIII, Zn XXIV, Ge XXIV, and Ge XXV observed in laser-produced plasmas

Wavelengths and wave numbers are presented for zinc lines in the F I, O I, and N I isoelectronic sequences as well as for germanium lines in the F I and O I sequences. The transitions are of the type 2s(2)2p(k)-2s2p(k+1), and the lines were observed near 100 A in the spectra of plasmas produced by focusing the pulse from a high-power glass laser on to solid targets of different elements and compounds. The results are compared with prediction based on extrapolations of semiempirical formulas derived by Edlen (1969). The wavelengths and wave numbers of some of the corresponding transitions in Cu XXI, Cu XXII, Cu XXIII, Ga XXIII, and Ga XXIV are interpolated with a probable wavelength accuracy of at least plus or minus 0.02 A.

Behring, W. E.↗
NASA NTRS1975

Observation of subordinate 2p/5/4d-2p/5/3p transitions in neon-like ions from Ca XI to Ni XIX

Subordinate 2p(5)4d-2p(5)3p transitions in the neon-like ions from Ca XI through Ni XIX are identified. Such transitions between excited levels have not previously been reported for ionization stages higher than Al IV, although the resonance lines are known through Zn XXI in the neon isoelectronic sequence. Measurement of the solar flux in such transitions may aid in establishing the relative importance of the several cascade processes giving rise to the observed Fe XVII resonance lines.

Kastner, S. O.↗
NASA NTRS1974

Transitions 2s/2/ 2p/k/ - 2s 2p/k+1/ of the F I, O I, and N I isoelectronic sequences

Transitions of the type 2s/2/ 2p/k/ - 2s 2p/k+1/ have been identified for the elements from titanium through nickel for ions of the fluorine, oxygen, and nitrogen isoelectronic sequences. Wavelengths, visual intensity estimates, and energies are given. The energy differences of levels of the ground configuration are compared with predictions based on semiempirical equations derived by Edlen. Some of the lines of these isoelectronic sequences should be strong lines in solar-flare spectra.

Doschek, G. A.↗
NASA NTRS1973

2s-2p transitions in the spectra of Ca XVII and Ti XIX.

Identifications of energy level transitions in the Ca XVII and Ti XIX spectra in the regions of 190-360 A and 160-300 A, respectively, are presented for the first time. Lines corresponding to the transition arrays concerned are identified and classified. Extrapolation procedures are described in detail.

Goldsmith, S.↗
NASA NTRS1972

The lithium-like spectra of K XVII through Mn XXIII in the extreme-ultraviolet region.

Identifications and classifications of spectral lines in the lithium-like spectra of the elements K through Mn is presented for the first time. The extrapolation procedures used to calculate these spectra are presented in detail. The excellent agreement between the predicted and measured lines establish the long-range extrapolation.

Goldsmith, S.↗
NASA NTRS1972

Carbon-like spectra of Sc XVI, Ti XVII, and V XVIII in the range 16-22 A.

The spectra reported are important for the analysis of the spectra of CaXV and FeXXI. The extreme UV solar spectrum should contain some lines of these two ions. The spectroscopic source consisted of a low-inductance vacuum spark with electrodes made of the elements under investigation. Altogether 44 new lines in the region from 16 to 22 A were classified. Some previously unidentified lines of ClXII and ArXIII were also classified. The extrapolation of the ground-configuration energy levels is discussed.

Goldsmith, S.↗