2001 Award Winners
Government Award Winner
Hollow Cathode Assembly for the ISS Plasma Contactor and Hollow Cathode Technology
Lead NASA Center:
Glenn Research Center (GRC)
The Hollow Cathode Assembly (HCA) is the primary component of the ISS Plasma Contactor System. Second NASA mission is Deep Space 1. HCA technology is in the NSTAR ion thruster on that spacecraft. The hollow cathodes on the ion thruster have operated flawlessly for over 16,000 hours. Ballistic Missile Defense Organizationís (BMDO) Russian Hall Effect Thruster Test (RHETT) is the first U.S. flight demonstration of Hall thruster technology. HCA was selected because of its superior performance and maturity over that of Russian technology. HCA for ISS required enormous technology development from what was state-of-the-art from 500 hours life, to 28,000 hours life, and from 10-ignitions to over 6000-ignition capability.
The HCA mitigates spacecraft charging by emitting electron current from a low density plasma to electrically ëgroundí ISS to near-space plasma potential. High voltages and exposed conducting surfaces across the ISS's solar arrays could cause the station structure to charge to a significant negative potential (> -100 V) relative to the ambient space plasma. Since the ISS structure is electrically tied to the solar arrays, this charging can lead to arcing, which would damage critical spacecraft surfaces. The HCA alleviates spacecraft charge build-up by emitting electrons collected by the solar arrays. A discharge is ignited between the hollow cathode and anode of the HCA. The resulting ionized gas, or plasma, is coupled to the spacecraft potential. When this plasma "sees" the ambient space plasma at a different potential, electrons stream between the two plasmas to equilibrate their potentials, thereby controlling spacecraft charging. The HCA is unique in that it controls spacecraft charging in a self-regulating manner.
Commercial Award Winner
Rotary Blood Pump (Ventricular Assist Device-VAD)
Lead NASA Center:
Johnson Space Center (JSC)
MSC-22424-1-2 and MSC-22822 (ARC-14087)
A ventricular assist device (VAD), includes a tubular housing which has an externally mounted motor stator, an internally fixed flow straightener within its upstream section, and a diffuser fixed within its downstream section. The only moving part, a one-piece rotor, is mounted on bearings between the flow straightener and the diffuser. The rotor includes an inducer portion and an impeller portion. Magnets embedded (sealed) in the vanes of the impeller form the motor rotor of the pump. A back EMF integrated circuit regulates rotor operation and a microcomputer may be used to control one or more back EMF integrated circuits. A magnet is embedded in each of a number of impeller blades with a minimum air gap between the blades and the housing bore. The implanted device is applied externally of the heart and connected to it by cannula. It assists in the pumping of blood from the lower left ventricle to the ascending aorta.
In operation, the pump is powered by batteries and has an external, patient-operated controller. The small turbine pump works in concert with the heart, to assist rather than to replace the heart's own natural pumping ability. Developed originally by NASA with private funding and assistance after a NASA employee heart patient spoke with Dr. Debakey about problems with VADs and suggested that he work with NASA designers. The LVAD came from that collaboration.
The VAD is used in three distinct modes:
- bridge to transplant — a temporary device used to help the patient survive while waiting for a suitable transplant organ to become available.
- bridge to recovery — surgeons have discovered that with some hearts, the assistance supplied by the VAD is sufficient to allow the natural heart to repair itself, in which case, the VAD can later be removed.
- a permanent implant.
The VAD uses NASA's most advanced 3D software design program (INS3D). It is literally the smallest and most viable (potentially permanent usage possible) implantable VAD in existence. The blades of the flow straightener, inducer, impeller, and diffuser are all optimized to function together to minimize blood hemolysis. Precisely shaped entrance and outlet angles, and the transitions between them, as well as the number of blades and their axial and radial positioning, blade pitch, degree of wrap and overlap, and axial and radial clearances, all contribute to the overall pumping efficiency and enhance the blood protecting character of the design. To preclude thrombosis (clotting) of the blood in the low flow rate areas around the bearings, the bearing areas are configured to allow cross-linked blood to fill and seal those areas.