Engineering topics

Dipirro, Michael J.

Publications and source records attributed to Dipirro, Michael J..

12 records

NASA NTRS2006

The Suzaku High Resolution X-ray Spectrometer

The high resolution X-Ray Spectrometer (XRS) has been designed to provide the Suzaku Observatory with very high spectral resolution, non-dispersive spectroscopy from 0.3 to 12 keV. This energy range encompasses the most diagnostically-rich part of the x-ray band. The sensor consists of a 32 channel array of x-ray of microcalorimeters, each with an energy resolution of about 6 eV. The very low temperature required for operation of the array (60 mK) is provided by a four-stage cooling system containing a single stage ADR, superfluid He Cryostat, solid Ne Dewar, and a single-stage Stirling-cycle cooler. The Suzaku/XRS is the first orbiting x-ray microcalorimeter spectrometer and has been designed to last more than three years in orbit. The early verification phase of the mission demonstrated that the instrument was working properly and that the cryogen consumption rate was low enough to ensure a mission lifetime exceeding 3 years. However, the liquid He cryogen was completely vaporized two weeks after opening the dewar guard vacuum vent. The problem has been traced to inadequate venting of the dewar He and Ne gases out of the spacecraft into space. In this paper we present the design of the XRS instrument and describe the in-flight performance.

Kelley, Richard L.↗

NASA NTRS2004

A Rapid Turnaround Cryogenic Detector Characterization System

Upcoming major NASA missions such as the Einstein Inflation Probe and the Single Aperture Far-Infrared Observatory require arrays of detectors with thousands of elements, operating at temperatures near l00 mK and sensitive to wavelengths from approx. 100 microns to approx. 3 mm. Such detectors represent a substantial enabling technology for these missions, and must be demonstrated soon in order for them to proceed. In order to make rapid progress on detector development, the cryogenic testing cycle must be made convenient and quick. We have developed a cryogenic detector characterization system capable of testing superconducting detector arrays in formats up to 8 x 32, read out by SQUID multiplexers. The system relies on the cooling of a two-stage adiabatic demagnetization refrigerator immersed in a liquid helium bath. This approach permits a detector to be cooled from 300K to 50 mK in about 4 hours, so that a test cycle begun in the morning will be over by the end of the day. Tine system is modular, with two identical immersible units, so that while one unit is cooling, the second can be reconfigured for the next battery of tests. We describe the design, construction, and performance of this cryogenic detector testing facility.

Benford, Dominic j.↗

NASA NTRS1990

A calorimetric mass gauge system for the Cosmic Background Explorer (COBE)

A system for the COBE flight dewar to measure its liquid helium fill is presented. A small known amount of heat is applied to the helium tank and monitor the temperature rise in the liquid and the tank. Working with a detailed thermal model of the tank and liquid the amount of liquid present is determined. COBE uses a 117-mW, 7-mA heater to warm the helium. It is planned to use the mass gaging system only after the projected midpoint of the mission, after one full sky survey. The system is optimized for use with 50-75 liters of helium. Ground testing of the system in a one-gravity environment is difficult, but from tests conducted so far, an on-orbit temperature rise of about 2.5 mK/min is estimated. A similar system is planned for the Superfluid Helium On-Orbit Transfer (SHOOT), a Shuttle-based experiment. The SHOOT's specific requirements call for a high-power pulse heater, applying 40 W for approximately 20 seconds.

Volz, Stephen M.↗

NASA NTRS1990

Cryogenic on-orbit performance of the NASA Cosmic Background Explorer (COBE)

The initial thermal set-up and operation of the dewar for the COBE spacecraft are discussed, focusing on the helium vent system. During the initial cooldown of the dewar from 1.72 K to 1.41 K, short term temperature and pressure oscillations were observed in the porous plug and in the vent line. A detailed flow model describing these oscillations was developed. Attention is also given to the steady state operating mode for the instruments and the dewar, a comparison of the 'mission mode' temperature and power profile of the dewar with the predicted performance, the instrument and spacecraft events affecting the helium boil-off rate, and the methods for determining the helium flow rate and remaining mass measurements.

Volz, Stephen M.↗

NASA NTRS1990

The SHOOT cryogenic components - Testing and applicability to other flight programs

Cryogenic components and techniques for the superfluid helium on-orbit transfer (SHOOT) flight demonstration are described. Instrumentation for measuring liquid quantity, position, flow rate, temperature, and pressure has been developed using the data obtained from the IRAS, Cosmic Background Explorer, and Spacelab 2 helium dewars. Topics discussed include valves and burst disks, fluid management devices, structural/thermal components, instrumentation, and ground support equipment and performance test apparatus.

Dipirro, Michael J.↗

NASA NTRS1990

Superfluid helium needs and resupply on Space Station

Viewgraphs and discussion on superfluid helium needs and resupply on space station are presented. Topics covered include: uses of superfluid helium in space; space station He 2 technology issues; resupply - fluid management issues; liquid acquisition devices for on orbit transfer; and liquid acquisition devices for SHOOT.

Dipirro, Michael J.↗

NASA NTRS1989

Superfluid helium orbital resupply - The status of the SHOOT flight experiment and preliminary user requirements

The Superfluid Helium On-Orbit Transfer (SHOOT) flight experiment is designed to demonstrate the components and techniques necessary to resupply superfluid helium to satellites or Space Station based facilities. A top level description as well as the development status of the critical components to be used in SHOOT are discussed. Some of these components include the thermomechanical pump, the fluid acquisition system, the normal helium and superfluid helium phase separators, Venturi flow meter, cryogenic valves, burst disks, and astronaut-compatible EVA coupler and transfer line. The requirements for the control electronics and software are given. A preliminary description of the requirements that must be met by a satellite requiring superfluid helium servicing is given. In particular, minimum and optimum plumbing arrangements are shown, transfer line flow impedance and heat input impacts are assessed, instrumentation is described, and performance parameters are considered.

Dipirro, Michael J.↗

NASA NTRS1988

Lab tests of a thermomechanical pump for shoot

Laboratory tests of a thermomechanical (TM) pump utilizing a commercially available porous disk have been conducted. Various size disks, heater configurations, and outlet flow impedances have been used to characterize scale models of the pump proposed for the Superfluid Helium On-Orbit Transfer (SHOOT) Flight Experiment. The results yield the scalability of the TM pump to larger diameters, and hence larger pumping rates, the dependence of flow rate on back pressure and heater power, and the limits of pumping speed due to internal losses within the porous disk due to mutual and superfluid friction. Analysis indicates that for low back pressures the flow rate is limited by the superfluid friction rather than the mutual friction. For the porous plug used in the early tests this amounts to a practical limit of 4.4 liters per hour per square centimeter. For a baselined flight plug area of 180 sq cm this yields 790 liters per hour.

Dipirro, Michael J.↗

NASA NTRS1988

Bayonet for superfluid helium transfer in space

A prototype superfluid helium bayonet for potential space applications has been developed and evaluated with a low heat leak test apparatus. Measured heat leak of the 13 mm (1/2 inch) bayonet pair is 0.21 W at 1.8 K with an uncertainty of +0.09/-0.05 W. Bayonets are fabricated with thin, electron beam (EB) welded tubes which are EB welded to machined nose and flange pieces. Low heat leak structural integrity is provided by a 0.9 mm thickness of filament wound fiberglass-epoxy. Superfluid creep is restricted by KEL-F nose seals which form vacuum-tight extensions to the bayonet cold end pieces.

Mcintosh, G. E.↗

NASA NTRS1988

The superfluid helium on-orbit transfer (SHOOT) flight experiment

The SHOOT flight demonstration is being undertaken to verify component and system level technology necessary to resupply large superfluid helium dewars in space. The baseline configuration uses two identical 210 liter dewars connected by a transfer line which contains a quick disconnect coupling. The helium will be transferred back and forth between the dewars under various conditions of flow rate, parasitic heat load, and temperature. An astronaut Extra-vehicular Activity (EVA) is also planned to manually demate and mate the coupling. A number of components necessary for the flight are being developed. These components are described here.

Dipirro, Michael J.↗

NASA NTRS1988

Acquisition system testing with superfluid helium

Minus one-g outflow tests were conducted with superfluid helium in conjunction with a thermomechanical pump setup in order to study the use of capillary acquisition systems for NASA's Superfluid Helium On-Orbit Transfer (SHOOT) flight experiment. Results show that both fine mesh screen and porous sponge systems are capable of supplying superfluid helium to the thermomechanical pump inlet against a one-g head up to 4 cm, fulfilling the SHOOT requirements. Sponge results were found to be reproducible, while the screen results were not.

Anderson, John E.↗

NASA NTRS1987

Superfluid helium on orbit transfer (SHOOT)

A number of space flight experiments and entire facilities require superfluid helium as a coolant. Among these are the Space Infrared Telescope Facility (SIRTF), the Large Deployable Reflector (LDR), the Advanced X-ray Astrophysics Facility (AXAF), the Particle Astrophysics Magnet Facility (PAMF or Astromag), and perhaps even a future Hubble Space Telescope (HST) instrument. Because these systems are required to have long operational lifetimes, a means to replenish the liquid helium, which is exhausted in the cooling process, is required. The most efficient method of replenishment is to refill the helium dewars on orbit with superfluid helium (liquid helium below 2.17 Kelvin). To develop and prove the technology required for this liquid helium refill, a program of ground and flight testing was begun. The flight demonstration is baselined as a two flight program. The first, described in this paper, will prove the concepts involved at both the component and system level. The second flight will demonstrate active astronaut involvement and semi-automated operation. The current target date for the first launch is early 1991.

Dipirro, Michael J.↗