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21.
Laser plasma thruster 总被引:5,自引:0,他引:5
Luke J.R. Phipps C.R. McDuff G.G. 《Applied Physics A: Materials Science & Processing》2003,77(2):343-348
The laser plasma thruster (LPT) is a new microthruster for small satellites. We report on development and testing of a prototype
LPT. Some advantages of the LPT are: thruster voltage 4 V, mass less than 1 kg, power-to-thrust ratio 10 kW/N, and Isp up to 1000 s. Typical thrust level is 250 μN with PVC fuel. Thrust of 1 mN is expected with energetic fuel. The pre-prototype
continuous-thrust experiment includes the laser mount and heat sink, lens mounts, and focusing mechanism, which are coupled
to the target-material transport mechanism. The target material is applied to a transparent plastic tape, and the laser is
focused on a series of tracks on the tape. The tape-drive hardware and laser-drive electronics are described. Design, construction,
and calibration of the thrust stand are described. During continuous operation, the exhaust plume is deflected in the direction
of the moving tape. When the laser is operated in pulsed mode, the exhaust plume is perpendicular to the tape (parallel to
the optical axis). This provides some thrust-vector control. Measured thrust is 70 μN with PVC fuel, and 550 μN with energetic
fuel, with a specific impulse of 350 s.
Received: 7 October 2002 / Accepted: 20 January 2003 / Published online: 28 May 2003
RID="*"
ID="*"Corresponding author. Fax: +1-505-272-7203, E-mail: luke@iera.nmt.edu 相似文献
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T. E. Phipps Jr. 《Foundations of Physics》1980,10(3-4):289-307
We address the question: By what class of force-application programs must a meter stick initially at rest in an inertial frame be moved in order to transfer it to a relatively moving inertial frame without altering the internal energy state of the structure in the process? Such stress-free transfer of a metric standard is essential for moving-axis calibration (a neglected art in established relativity theory). In order to deduce the answer by reasonings appropriate to kinematics, it proves necessary to make an extension of the relativity principle to rectilinear (irrotational) accelerated motions, and to enhance the kinematic motion group accordingly. Since the physical motion groups differ, the answers we obtain to this and to the title question differ from those of special relativity. Our alternative kinematics thus leads to discrepancies that should be measurable atO(v 2/c 2). 相似文献
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N. Graneau T. Phipps Jr D. Roscoe 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,15(1):87-97
According to the conventional views of electromagnetic theory, as these are expressed in the Lorentz force law, all the forces
which act on a current carrying metallic conductor are perpendicular to the current streamlines. However, over the years,
from Ampère through Maxwell until the present day, there have been persistent claims that when current flows in a metallic
conductor, there are mechanical forces acting along current streamlines which subject the conductor to tensile stress, and
which are therefore capable of performing work in the direction of current flow. The problem of substantiating these claims
has always lain in the difficulty of designing an experiment in which the effects are unambiguously demonstrated. The present
paper describes an experiment which to a large extent removes these ambiguities, and which provides a compelling novel demonstration
of forces acting along current streamlines. A force calculation based on Ampère's original electrodynamic force law is found
to be consistent with the observed behaviour.
Received 15 November 2000 and Received in final form 12 March 2001 相似文献
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Ahmed Z Akerib DS Arrenberg S Bailey CN Balakishiyeva D Baudis L Bauer DA Brink PL Bruch T Bunker R Cabrera B Caldwell DO Cooley J do Couto e Silva E Cushman P Daal M DeJongh F Di Stefano P Dragowsky MR Duong L Fallows S Figueroa-Feliciano E Filippini J Fox J Fritts M Golwala SR Hall J Hennings-Yeomans R Hertel SA Holmgren D Hsu L Huber ME Kamaev O Kiveni M Kos M Leman SW Liu S Mahapatra R Mandic V McCarthy KA Mirabolfathi N Moore D Nelson H Ogburn RW Phipps A Pyle M Qiu X Ramberg E Rau W 《Physical review letters》2011,106(13):131302
We report results from a reanalysis of data from the Cryogenic Dark Matter Search (CDMS II) experiment at the Soudan Underground Laboratory. Data taken between October 2006 and September 2008 using eight germanium detectors are reanalyzed with a lowered, 2 keV recoil-energy threshold, to give increased sensitivity to interactions from weakly interacting massive particles (WIMPs) with masses below ~10 GeV/c(2). This analysis provides stronger constraints than previous CDMS II results for WIMP masses below 9 GeV/c(2) and excludes parameter space associated with possible low-mass WIMP signals from the DAMA/LIBRA and CoGeNT experiments. 相似文献
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Saltiel J Krishna TR Laohhasurayotin K Ren Y Phipps K Davis PH Yee WA 《The journal of physical chemistry. A》2011,115(11):2120-2129
Quantum yields for the photoisomerization of trans,trans-1,4-diphenyl-1,3-butadiene (tt-DPB), determined in benzene, cyclohexane, methylcyclohexane, hexane, and perfluorohexane, confirm the low values reported earlier for benzene and cyclohexane and reveal even lower values in the last two solvents. In contrast to trans-stilbene (t-St), fluorescence and torsional relaxation leading to photoisomerization do not account exclusively for S(1)tt-DPB decay. Competing radiationless singlet excited-state decay pathways exist in tt-DPB, which do not lead to photoisomerization and may not involve large-amplitude torsional motions. Our results invalidate analyses of tt-DPB fluorescence quantum yields and lifetimes that assign all radiationless decay to the isomerization channel. Gas-phase chromatography analysis of tt-DPB photoisomerization in hexane shows the reaction to be concentration-independent and reveals, for the first time, a significant, two-bond photoisomerization pathway, φ(tt→tc) = 0.092 and φ(tt→cc) = 0.020. The dominant one-bond-twist (OBT) process is accompanied by a bicycle pedal (BP) process that accounts for almost 20% of tt-DPB photoisomerization. The OBT tt-DPB photoisomerization quantum yield is largest in benzene (Bz) and smallest in perfluorohexane (PFH). Contrary to expectations, reduction in medium friction in PFH is accompanied by a decrease in φ(tt→tc). The 1(1)B(u)/2(1)A(g) order and energy gap appear to control the contribution of torsional relaxation to radiationless decay. Lowering the 1(1)B(u) energy as in Bz favors photoisomerization. Reversal of the 1(1)B(u)/2(1)A(g) order in PFH is accompanied by short τ(f) and small φ(f) and φ(tt→tc) values that suggest the presence of competing 2(1)A(g) → 1(1)Ag relaxation paths that are unproductive with respect to photoisomerization. We conclude that the Birks extension to diphenylpolyenes of the Orlandi-Siebrand cis-trans photoisomerization mechanism is not valid. Photoisomerization appears to occur in the 1(I)B(u) state, and we argue that this applies to t-St as well. 相似文献