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Record 82 of 2581
A Magnetic Bumper-Tether System Using ZFC Y123
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Author and Affiliation:
Weinstein, Roy(Houston Univ., Inst. for Beam Particle Dynamics, TX United States)
Parks, Drew(Houston Univ., Inst. for Beam Particle Dynamics, TX United States)
Sawh, Ravi-Persad(Houston Univ., Inst. for Beam Particle Dynamics, TX United States)
Obot, Victor(Texas Southern Univ., Dept. of Mathematics, Houston, TX United States)
Liu, Jianxiong(Texas Southern Univ., Dept. of Mathematics, Houston, TX United States)
Arndt, G. D.(NASA Johnson Space Center, Houston, TX United States)
Abstract: We consider the use of magnetic forces in a bumper system, to soften docking procedures. We investigate a system which exhibits no magnetic field except during the docking process, which, if desired, can automatically tether two craft together, and which provides lateral stability during docking. A system composed of zero field cooled Y(1.7)Ba2Cu3O(7-delta) (Y123) tiles and electromagnets is proposed. The Y123 high temperature superconductor (HTS) is mounted on one craft, and the electromagnet on the other. Results of small prototype laboratory experiments are reported. The electromagnet has, for convenience, been replaced by a permanent SmCo ferromagnet in these measurements. When the two craft approach, a mirror image of the ferromagnet is induced in the Y123, and a repulsive bumper force, F(sub B), results. F(sub B) is velocity dependent, and increases with v. For presently available HTS materials, bumper pressure of approx. 3.7 N/cm(exp 2) is achieved using SmCo. This extrapolates to approx. 18 N/cm(exp 2) for an electromagnet, or a force of up to 20 tons for a 1 m(exp 2) system. After reaching a minimum distance of approach, the two colliding craft begin to separate. However, the consequent change of SmCo magnetic field at the Y123 results in a reversal of current in the Y123 so that the Y123 is attractive to the SmCo. The attractive (tether) force, F(sub T), is a function of R = B(sub Fe)/B(sub t, max), where B(sub Fe) is the field at the surface of the ferromagnet, and B(sub t, max) is the maximum trapped field of the Y123, i.e., the trapped field in the so-called critical state. For R greater than or equal to 2, F(sub T) saturates at a value comparable to F(sub B). For a range of initial approach velocities the two craft are tethered following the bumper sequence. Most of the kinetic energy of the collision is first converted to magnetic field energy in the Y123, and then into heat via the creep mechanism. About 15% of the work done against magnetic forces during collision remains stored as magnetic energy after 1 hour. Experiments have also been conducted on the spatial range of the bumper force for arrays of HTS tiles. For a single HTS tile approx. 2 cm in diameter, the range of F(sub B) is approx. l cm. For a l m(exp 2) array the range of F(sub B) will be circa 50 cm.
Publication Date: Jul 01, 1996
Document ID:
(Acquired Dec 07, 1996)
Accession Number: 96N35912
Document Type: Conference Paper
Publication Information: Third International Symposium on Magnetic Suspension Technology; Part 1; 207-216; (NASA-CP-3336-Pt-1); (SEE 19960052904)
Financial Sponsor: NASA Langley Research Center; Hampton,VA United States
NASA; Washington, DC United States
NASA Johnson Space Center; Houston, TX United States
National Science Foundation; Washington, DC United States
Army Research Office; Washington, DC United States
State of Texas; TX United States
Organization Source: NASA Johnson Space Center; Houston, TX United States
Description: 10p; In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: No Copyright
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