Date: Fri, 19 Mar 93 05:15:33 From: Space Digest maintainer Reply-To: Space-request@isu.isunet.edu Subject: Space Digest V16 #337 To: Space Digest Readers Precedence: bulk Space Digest Fri, 19 Mar 93 Volume 16 : Issue 337 Today's Topics: 20Khz Power supplies. (2 msgs) Beyond 1000! moon's fate when removing gravitational influence of earth NASA and congress Need MIR packet Frequency's One Ticket To LEO, Please... Predicting gravity wave quantization & Cosmic Noise (2 msgs) SDIO VS NASA (was Re: Retraining at NASA) Solar Arrays Falling Off SR-71 Maiden Science Flight Why use AC at 20kHz for SSF Power? Welcome to the Space Digest!! Please send your messages to "space@isu.isunet.edu", and (un)subscription requests of the form "Subscribe Space " to one of these addresses: listserv@uga (BITNET), rice::boyle (SPAN/NSInet), utadnx::utspan::rice::boyle (THENET), or space-REQUEST@isu.isunet.edu (Internet). ---------------------------------------------------------------------- Date: 18 Mar 93 18:49:07 GMT From: fred j mccall 575-3539 Subject: 20Khz Power supplies. Newsgroups: sci.space In <15179.409.uupcb@the-matrix.com> roland.dobbins@the-matrix.com (Roland Dobbins) writes: >Ah, Fred, back to your old tricks again. Seems like old times on BIX. Yep, back to speaking my mind. Pity some of you apparently have such a problem with little things like 'Freedom of Speech', ain't it? >Too bad there's no moderator here to get you thrown off . . . Yeah. Fortunately, this pond is just a mite too big for the kind of petty politicking among people who are legends in their own minds that was going on on BIX when I was there. Frankly, despite the fact that the concentration of technical people gives it lots of potential, as long as it's the way it was when I was there you are more than welcome to keep it all to your little self. [Give Tony my love. ;-)] -- "Insisting on perfect safety is for people who don't have the balls to live in the real world." -- Mary Shafer, NASA Ames Dryden ------------------------------------------------------------------------------ Fred.McCall@dseg.ti.com - I don't speak for others and they don't speak for me. ------------------------------ Date: 18 Mar 93 18:50:16 GMT From: fred j mccall 575-3539 Subject: 20Khz Power supplies. Newsgroups: sci.space In <15180.409.uupcb@the-matrix.com> roland.dobbins@the-matrix.com (Roland Dobbins) writes: >Ah, Fred, up to your old tricks still. Reminds of of the old days, on BIX. >Too bad there isn't a moderator to throw you out _here_ . . . Saying it twice? Does your BBS have the hiccups, or what? -- "Insisting on perfect safety is for people who don't have the balls to live in the real world." -- Mary Shafer, NASA Ames Dryden ------------------------------------------------------------------------------ Fred.McCall@dseg.ti.com - I don't speak for others and they don't speak for me. ------------------------------ Date: 18 Mar 1993 12:48:47 -0500 From: Pat Subject: Beyond 1000! Newsgroups: sci.space References: <1o15ak$3e8@huon.itd.adelaide.edu.au> <1993Mar15.103255.1@fnalf.fnal.gov> Nntp-Posting-Host: access.digex.com Sender: news@CRABAPPLE.SRV.CS.CMU.EDU Source-Info: Sender is really isu@VACATION.VENARI.CS.CMU.EDU In article <1993Mar15.103255.1@fnalf.fnal.gov> higgins@fnalf.fnal.gov (Bill Higgins-- Beam Jockey) writes: >popularization. (However, it probably led directly to my addiction to >Tom Swift novels for a few years...) > QUick, bill, Just paint some tomasite over the meteor puncture in the inflatable module :-) >series *Horizon* are transported across the Atlantic, get their serial >numbers filed off, and appear on PBS as *Nova* episodes. In some >cases I suspect they even replace the British narration with a Bill, Lots of British Stuff now gets US underwriting directly or indirectly. Things like DrWHo pulls in so much license money, that for Years BBC took into account american tastes for writing the show. Also PBS will underwrite a serial production directly in return for US Rights, and oftentimes exert strong editorial control. Now what you describe is OEM tv, where I think they shoot segments witht he direct intention of re-narration for internationalization. OEM TV has been around for years, look at Commercials. FORD,GM will produce a commercial, and the local dealers association will hire a narraotor to do a voice over while a graphic comes up with dealership Addresses and phone numbers. Hollywood, when they film movies, now directly consider Internationalization and will co-ordinat ethe sound re-dubbing, it's why newer import movies have a better look then in the old days. pat ------------------------------ Date: 18 Mar 93 17:40:29 GMT From: Ed Faught Subject: moon's fate when removing gravitational influence of earth Newsgroups: sci.space In article HSTEINER%ESRIN.BITNET@bitnet.cc.cmu.edu ("Hans M. Steiner") writes: >If one could "take away" the earth in an instant (remove the influence >of the earth on the moon), what would happen to the moon's orbit around >the sun? Darn! I thought that pesky galactic bypass project had been abandoned. -- Ed Faught WA9WDM faught@berserk.ssc.gov DEFINITELY NOT a spokesman for the Superconducting Super Collider Laboratory ------------------------------ Date: 18 Mar 93 08:03:34 GMT From: Pat Subject: NASA and congress Newsgroups: sci.space Brian comments on a lack of experience making space engineering difficult. As henry has pointed out, since the end of the 60;s no-one has had programs related to building testing and exploring new technologies. The saturn was a success, because 10 years earlier, people in the air force and NACA started programs for Large rocket motor design. I've pointed out shortages in space qualified hardware. LDEF only flew once, why not again? or MINI LDEF, something that fits into a DELTA, you fly it up and have shuttle retrieve it after some other mission. SDIO puts a lot of effort into infrastructure needs. better sensors, better transport. I'm not saying NASA doesn't have challenging goals, but they might do better if they went with smaller programs, faster schedules, ongoing basis. Goldin seems to think so to. The discovery missions look real good, why not a Vanguard Program. WHere birds just fly to prove and test gear? about the same size as discovery, but solely for engineering. pat ------------------------------ Date: 18 Mar 93 17:48:54 GMT From: Don Woelz Subject: Need MIR packet Frequency's Newsgroups: sci.space,rec.ham-radio.packet,rec.radio.amateur.packet In article george@agora.rain.com (George Rachor) writes: >Anyone remember the frequency's used by the MIR space station packet radio system? > As I recall, they can be found on 145.550. What I don't recall is what callsign they use. Anybody help with that? -- Donald D. Woelz Office Phone: 414-644-8700 GENROCO, Inc. Toll Free: 800-243-6762 205 Kettle Moraine Drive North Office Fax: 414-644-6667 Slinger, WI 53086 U.S.A. 24 hr Voicemail: 414-322-3891 ------------------------------ Date: 18 Mar 93 18:59:08 GMT From: "Kieran A. Carroll" Subject: One Ticket To LEO, Please... Newsgroups: sci.space In article <1993Mar18.013020.1791@ke4zv.uucp> gary@ke4zv.UUCP (Gary Coffman) writes: > (discussion of relative costs for launching Shuttle, > hypothetical Delta Clipper, and trans-Pacific airliner, > leading to...) > ...If we take more >reasonable marginal costs of $110 million for a Shuttle flight, >the cost per pound is $2,750... > It should be remembered, however, >that projected Shuttle costs per pound were $300 at a similar stage >of it's development. While we're at it, it's important to remember that the $300/lb to LEO that the Shuttle was expected to achieve used 1973 dollars (or there-abouts...in any case, constant dollars fixed at the time that the original Shuttle systems designs were being done). I'm not sure what the inflation factor is between 1973 and 1993, but my fuzzy memory of the year-by-year inflation rates over that period lead me to an estimate that 1973$1 equals between 1993$4 and 1993$6. Thus, 1973$300/lb would be equivalent to between 1993$1200/lb and 1993$1800/lb. The marginal cost of operating the Shuttle appears to be not that far from the number that its designers were aiming for! (i.e. within a factor of two or three). The Shuttle's detractors like to use the $500M/flight price tag (ignoring the few outliers who insist that it really should $1B or $2B per flight, to fully account for all manned spaceflight development costs from 1960 onwards), in current dollars, and then pretend that the $300/lb cost estimate was also in current dollars, to "prove" that manned spaceflight projects always have cost over-runs of 3000%. Come to think of it, some of the same people like to argue that Space Station is hundreds or thousands of percent over budget, using similar perniciously faulty reasoning. I wonder why...? Sure, the Shuttle didn't fully deliver on the goals that it aimed for. However, it came much closer to accomplishing them than many people are willing to admit. -- Kieran A. Carroll @ U of Toronto Aerospace Institute uunet!attcan!utzoo!kcarroll kcarroll@zoo.toronto.edu ------------------------------ Date: 18 Mar 93 18:24:06 GMT From: Cameron Randale Bass Subject: Predicting gravity wave quantization & Cosmic Noise Newsgroups: sci.space,sci.astro,sci.physics,alt.sci.planetary In article <1993Mar18.150800.29635@aio.jsc.nasa.gov> tes@motif.jsc.nasa.gov. (Thomas E. Smith) writes: >>In article <17MAR199323474326@kelvin.jpl.nasa.gov> baalke@kelvin.jpl.nasa.gov (R >>on Baalke) writes: >>> Three interplanetary spacecraft, now headed quietly toward Mars, >>>Jupiter and over the poles of the sun, soon may prove the >>>existence of elusive waves in the universe's gravitational field by >>>bobbing on ripples in space like corks bobbing on ripples in a pond. >> >>From: markh@csd4.csd.uwm.edu (Mark) >>I'm betting that the following will be observed: Cosmic Noise. A large number >>of components will be detected at around wavelengths of 1 AU and above with >>VERY low intensity, if the configuration is sufficiently tuned. The >>components will have wavelengths that occur at discrete jumps of about 1 >>millimeter at 1 AU. > >Ok, I give up. Why will wavelengths be detected at around 1 AU and up at low >intensity? > >As for the cosmic noise, it probably will be observed, but since gravity waves >are the only known phenonema that can wobble all three spacecraft at almost the >same time (I forget if gravity travels the speed of light, or is instantly >propagated) you can filter out the noise by only looking at events that affect >all three spacecraft. Okay, but how does one rule out ordinary environmental perturbations that happen to occur at the appropriate times? How does one distinguish between an ordinary dynamical triple-coincidence event and a gravitational one? dale bass ------------------------------ Date: 18 Mar 1993 11:25 PST From: SCOTT I CHASE Subject: Predicting gravity wave quantization & Cosmic Noise Newsgroups: sci.space,sci.astro,sci.physics,alt.sci.planetary In article <1993Mar18.151055.29787@aio.jsc.nasa.gov>, tes@motif.jsc.nasa.gov. (Thomas E. Smith) writes... > >How much more sensitive is the setup with the three spacecraft than the >ground-based interferometer antennas? It's not, so far as I understand. But LIGO is still vaporware, so you do what you can do. >I am glad to see that you have taken advantage of a fantastic opportunity! >A High 5 to the scientists who proposed this! Let's just hope that nature >cooperates and gives us something to listen to :) This is not the first time it's been proposed, or even done. See, for example. J.D. Anderson et.al, "Gravitation and Celestial Mechanics Investigations with Galileo," Space Science Reviews V60, no.1-4, pp 591-610, May 92. I suspect that the experiments contained in this paper won't be done because of the problems with Galileo... There was also a Phys. Rev. paper in the last six months or so reporting a measurement that actually *was* made, using one of the Voyager spacecraft, if I am not mistaken, which found no gravity waves. -Scott -------------------- Scott I. Chase "It is not a simple life to be a single cell, SICHASE@CSA2.LBL.GOV although I have no right to say so, having been a single cell so long ago myself that I have no memory at all of that stage of my life." - Lewis Thomas ------------------------------ Date: 18 Mar 93 19:33:35 GMT From: "Allen W. Sherzer" Subject: SDIO VS NASA (was Re: Retraining at NASA) Newsgroups: sci.space In article brian@galileo.jsc.nasa.gov (Brian Donnell) writes: >> Talk to SDIO. Their support infrastructure for SSRT represents less then >> 1/60 of the program cost. Yet they are doing more to support cheap routine >> access to space than NASA has ever done. >Good stuff, I agree. But SDIO's efforts are narrower in scope than the >overall goals of NASA, e.g., permanent manned presence, thorough >exploration of the solar system (manned and unmanned), etc. SDIO's scope isn't trivial but that is beside the point. NASA could run many or most of its projects a similar way. Besides, nothing would have so profound a positive impact on NASA's goals than cheap routine access to space. Their management structure has yet to accoplish it and the first effort by another agency using a radical (for government) approach seems to be pretty successful. There is a lesson to learn here. Even without SSTO, SDIO spends half to a third of what NASA does to send a pound to LEO. Yet they both use the very same launchers in many cases and launch similar payloads. >BTW - I disagree with the previous estimate of infrastructure costs being >50% of NASA's overall costs. Nither did I. However, the center wrap adds about 30% to the cost of anything NASA does. Many other examples exist of NASA paying an order of magnitude more than private companies for the same thing. >> Agreed that is a problem. Yet other parts of government deal with the >> same problems all the time. >Other govt agencies due not have to deal with unknown and volatile domains >to the extent that NASA does. We are talking about DoD and they do indeed deal with unknown and volatile domanis. Even more so than NASA: DoD systems must count on an enemy actively working to destroy your systems. NASA need only worry about the environment. >> Clementine, Delta Clipper, Timberwind... I'll stack SDIO's record for >> promoting space against NASA any day. Better, cheaper, faster is new >> to NASA but it was always SOP at SDIO. >For their focused domain, these are good. But I will bring us back to the >big-picture point again that NASA has to keep in mind. Focused domain? We are talking about lunar and asteroid space probes, experimental spacecraft, and nuclear engines for space applications. That's hardly a narrow focus and provides a record of inovation in space research superior to NASA. The most innovative ideas ideas for pushing out into space are coming from DoE and SDIO. Ditto for the most focused diciplined efforts to make it happen. The only inovative ideas coming from NASA recently are from the former SDIO people working there. Allen -- +---------------------------------------------------------------------------+ | Allen W. Sherzer | "A great man is one who does nothing but leaves | | aws@iti.org | nothing undone" | +----------------------90 DAYS TO FIRST FLIGHT OF DCX-----------------------+ ------------------------------ Date: 18 Mar 93 08:12:43 GMT From: Pat Subject: Solar Arrays Falling Off Newsgroups: sci.space Isn't it nice to see advanced technical argument and discussion from people involved in all sides of the work. pat who would still like to see something from someone who worked on Lewis's High frequency power proposals. ------------------------------ Date: Thu, 18 Mar 1993 19:01:21 GMT From: Mary Shafer Subject: SR-71 Maiden Science Flight Newsgroups: sci.space On Thu, 18 Mar 1993 16:05:22 GMT, neff@iaiowa.physics.uiowa.edu (John S. Neff) said: John> In article shafer@rigel.dfrf.nasa.gov (Mary Shafer) writes: >From: shafer@rigel.dfrf.nasa.gov (Mary Shafer) >Matthew> is NASA going to run the SR-71 through its paces and find out >Matthew> what exactly IS its top speed? > >Only if there's a research requirement to do so. > >I wouldn't hold my breath waiting for this to happen. John> Please explain the advantage of the SR-71 over a ballon for UV John> spectrophotometry. The maximum altitude of the SR-71 listed in a previous John> post was about the same, or a little lower, than the normal altitude of John> a ballon flight. Ask someone at JPL--it's their experiment. We're just flying it for them. I'm sure that they have a good reason. Availability, cost, instrument packaging, reusability; these come to my mind as possible factors. The only thing I know about UV dates back to '60's black lights. Come to think of it, so does some of what I know about SR-71s. -- Mary Shafer DoD #0362 KotFR NASA Dryden Flight Research Facility, Edwards, CA shafer@rigel.dfrf.nasa.gov Of course I don't speak for NASA "A MiG at your six is better than no MiG at all." Unknown US fighter pilot ------------------------------ Date: 18 Mar 93 19:25:00 GMT From: "David B. Mckissock" Subject: Why use AC at 20kHz for SSF Power? Newsgroups: sci.space Below are 400 some odd lines of detailed information on the topic of the initial selection of 20 kHz as the distribution frequency for the SSF power system. Most of what follows is directly from a paper "Space Station Power (Why use AC at 20-kHz?) by Jim Mildice, General Dynamics, Space Systems Division. Following the detailed info is a bibliography listing 35 sources for additional detailed information on 20 kHz. {As an aside that nas nothing to do with 20 khz, some folks may be amused to know that during my research, I found out that the NASA Headquarters library subscribes to "Space Watch", with the "One Small Step for a Space Activist" column by our very own Allen Sherzer (and help from Tim Kyger)}. I asked one of the LeRC gentleman involved in the 20 kHz research about the problems MSFC had at their testbed with the 20 kHz components (which was raised by Dennis). The LeRC explanation is that the MSFC system was purchased by MSFC, based on requirements written by MSFC (i.e. Marshall was *NOT* using hardware from the LeRC testbed, they went out and bought their own hardware). The LeRC view is that the MSFC requirements were flawed, so the MSFC system was "built not to work." Why 20 kHz??? Aerospace power systems have historically been designed to distribute power over low voltage DC busses, commonly 28-vDC. This works fine when the power is low, the distances over which the power is delivered are short, and there are a few closely- controlled users. For SSF, the distances from source to load are not short (typically greater than 50 meters), and the power we can deliver (56 kW at PMC) is much greater than any current spacecraft. By design, there will be many different users on SSF. Therefore, this is an application where we need to investigate Power Management & Distribution alternatives. The DC Alternative The simplest system that we could conceive would extrapolate an ideal DC system concept used on a few small spacecraft. There is an appealing kind of engineering logic that makes this approach attractive, on the surface. Solar arrays and batteries are DC sources, so it seems natural to interface them directly. The batteries are connected directly to the output of the solar arrays. They load the arrays, thereby controlling the bus voltage, and automatically recharge when their terminal voltage is low (discharged). The charge rate decreases as the terminal voltage rises (toward fully charged), or as user loads demand power and decrease the solar array output voltage. With proper solar array and battery designs, the system regulates and controls itself. Of course, the loads have to operate over a voltage range equal to the battery voltage variation from charge to discharge. As the system grows, complexity increases rapidly. When we add another solar array, we have to control the arrays' respective output voltage so that they share the load. Even if we were to match them initially, they wouldn't stay matched after a few years in orbit. And if they're not matched, we can't get all the power they're capable of supplying. So we add an array regulator or controller. The same is true for multiple battery strings. If we try to eliminate a power processor and put a single regulator on the output of a solar array-battery combination, we lose some of the benefits of cross-strapped redundancy (often one of the reasons tooadd another string). And as the number of users increases, they usually want to be isolated from one another, and DC-DC converters are added at their inputs. If we keep the voltage low (say, at 28-vDC, a common user voltage), distribution bus currents and masses get out of hand as power requirements and transmission distances grow. Therefore, transmission voltage must be increased (typically to 150- or 270-vDC). Since few users can utilize the increased-voltage DC power directly, more DC-DC converters or other kinds of power processors are added. You can see that our simple, ideal DC system has grown to include a lot of power processing equipment. The AC Alternative Since we now have power processors at the solar array and battery interfaces, it is not much of an extrapolation to consider what happens if we change those processors to inverters, and distribute AC. Westinghouse's AC utility power distribution approach won out over Edison's DC a century ago, and terrestrial 50-60 Hz utility power has been with us ever since. Most of the reasons that applied then still apply, especially for a modern spacecraft that provides utility-type power for a wide variety of users and loads. Some of them are: o Rotating machines - "want to operate" with AC. Alternators are smaller, quieter, and simpler than their DC-generator cousins. The same is true for AC induction motors, when compared to DC or universal motors. Even modern, electronically-computated, DC "brushless" motors generate significant amounts of high-frequency noise and interference, and must include an electrical power processor. A good, everyday example of the AC machine's desirability is in the DC power system in our cars, where AC alternators have replaced DC generators as the prime electrical energy source. o Transformers - are simple, efficient components to change voltage levels and/or provide power source isolation. And while DC-DC converters are sometimes considered to be the DC system equivalent of the transformer, they simply cannot match the AC devices for reliability, efficiency, and simplicity. o Power Supplies - Many users can utilize simple transformer- rectifier-filter supplies to get the many levels of AC and DC typicall required for modern electronic systems, rather than the more costly and complex DC-DC converters used to do the same job with DC input power. o Switching - The zero-crossings in an AC power source allow for all the power switching to occur at zero currents, thereby eliminating a major source of transient EMI and noise in space systems. Zero-current switching also simplifies switchgear design and improves reliability, since switches never have to interrupt large currents into loads, or even larger currents into faults. AC System Frequency Since it is now clear that AC has many advantages and is the probable choice for a large spacecraft with utility-type power distribution, the frequency we choose becomes the final consideration. Of course, our terrestrial systems are 60 or 50-Hz (depending on whether we are in the US or abroad). When aircraft became sophisticated enough to start worrying about shaving weight to improve payloads, their AC systems went to 400-Hz, primarily because of reduced size and weight. With space shuttle delivery costs very high (see Wales Larrison or Allen Sherzer posts), we need to at least think about higher frequencies again. The systems components which are most strongly effected by the frequency choice are field-generating devices, like inductors, capacitors, and transformers. They all seem to follow an exponential decrease, and the curve looks relatively flat above 10-kHz, if we consider high power equipment (at least 10 kW) and start the comparisons back near 60 Hz. So there isn't a strong size and weight driver, pushing us above that frequency region. If we're conserned about a manned vehicle, we should probably move to at least 20 khz to get the power line noise above the audio region. (That 400 Hz whine in my airliner stereo head-set is really annoying if I have to listen for very long). But how high can we comfortably go? The answer comes from the DC power processing folks. When we design DC to DC converters in this power range, readily-available component technologies for semiconductor switching devices, transformers, capacitors, etc. limit us to a maximum frequency of about 50kHz. So if we stay comfortably below that, and continue with our initial thought to chose something close to 20 kHz, we can expect to find a good selection of qualified power components and materials, and a good body of design data, with which to implement hardware designs. But one of the biggest drivers for a high frequency choice also comes from modern DC power processor technology. As discussed earlier, when we have to interface with a source having a voltage that is significantly different from that which we need, or when we need ground isolation, we insert a DC to DC converter. A typical modern DC to DC converter contains a switching (or chopper) stage which takes the input DC and converts it to high-frequency AC. A transformer then raises or lowers the voltage to the required value, usually in conventional AC power system fashion. This AC is then rectified and filtered to output the DC power to the load. So, in the actual DC system on a large general-purpose spacecraft (like SSF), including all the load and source power processing, it looks like the figure below. As you can see, several DC to AC to DC conversions are required (at the source interface, battery interface, and most load interfaces). It becomes an obvious extrapolation to take away some of the hardware, so the normal high frequency in the DC to DC converter intermediate stages is simply applied tooand taken from the distribution busses, and the power system is nothing more than a large, distributed DC to DC converter, which eliminates about half of the hardware in a conventional DC system. Here is my attempt at the Figure ... Source-IF-Chpr-Xfer-R-OF--Dist Bus--IF-Chpr-Xfer-R-OF-Load DC Source-IF-DC to AC--Distribution Bus-Xfr-R-OF-Load AC Where: IF - Input Filter Chpr - Choppper, DC to AC Xfer - Transformer R - Rectifier, AC to DC OF - Output Filter Because of the nature of space station users, the above reduction in equipment is even greater than we would forecast by inspection. Many factors (duty cycling, experiment down time, user change overs, etc.) influence the actual amount of loads that are actively powered at any one time. Since everyone forcasts that the SSF power system will always be loaded to near-capacity, there will always be load hardware "waiting its turn." Depending on the conservatism of the analysis, estimates have projected that the ration of "installed" to "active" loads will be between two and four. The reduction in hardware would then bet between 675 and 1575 pounds But even those large-sounding weight savings would not be enough to justify the adoption of a technology that was this new for space systems (even though it has been extensively used elsewhere). The most powerful reason for selecting systems like the one on SSF comes from improved efficiency. The direct use of high frequency allows us to use Resonant Inversion. The approach we selected for SSF excites a series resonant inductance-capacitance circuit which "rings" at its natural frequency. Using a principle proposed by Neville Mapham more than 30 years ago, the output power is taken from across the resonant capacitor, and is a low distortion, low impedance, sine wave voltage source that can be used to power a "utility" type system. However, the most important feature of this approach is that all the switching associated with the power conversion occurs when the current is zero, when the resonant network has forced it to go there. This eliminates a major source of losses in modern power processing equipment, and typically cuts inverter losses in half, from approximately 10% to approximately 5%. Since a percent is around 500 W (on the PMC station), that means a savings on the PMC station of about $25 million. If we also add total life cycle costs for the entire mission, that savings can grow to between $100 million and $150 million, depending on how conservative your analysis rules are. The last question the die-hards finally ask is, "Since it's so good, why not use resonant inversion to produce 400-Hz or 60 Hz? Then we can have the best of both worlds, a familiar frequency and all the benefits of the new technology." If you do the math, you find that a direct-generation resonant inverter for 60-Hz or 400-Hz has resonant network values that would yield to enormous (and impractical) inductors and capacitors. We could (and do) use resonant processors to change to an intermediate high-frequency and then synthesize the low frequency by steering the high frequency pulses. While this would design a superior inverter or DC to DC converter with higher efficiencies than the conventional approaches, it would look a lot like a standard Dc to DC converter, and we would lose most of what we gained. For the SSF application, the "Science Users" provided the final rejection of low-frequency AC. To properly perform some of their measurements, they require that the external fields from power processing and transmission be at least three orders of magnitude (actualy ~70 db) lower than the typical performance of today's 400-Hz aircraft systems. Most experts in the field believe that this would not be possible. If a high-enough AC frequency (such as 20 kHz) is used, shielding to provide the lower interference levels is easier, and even more important, the interference the system might generate is well-above the frequency response of their instrumentation, and therefore will not cause a measurement problem. -- end of article by Jim Mildice -- Bibliography of the 20 kHz Research 1967 (1) Mapham, N., "An SCR Inverter with Good Regulation and Sine-Wave Otuput," IEEE Trans. on Industr. Gen. Application, Vol. IGA-3, No. 2, 1967, pp. 176- 1983 (2) Renz, D., Finke, R., Steven N., Tringer, J. and Hansen, I. "Design Considerations for Large Space Electric Power Systems", NASA TM-83064 1985 (3) Hoffman, A.C., Hansen, I.G., Beach, R.F., Plencer R.M., Dengler R.P., Jefferies K.S. and Frye R.J., "Advanced Secondary Power System for Transport Aircraft," NASA TP-2463 1986 (4) Mildice, J. and Waapes, L. "Resonant AC Power System: Proof of Concept" NASA CR-175069 (5) Mildice, J., "AC Power System Test Bed" NASA CR-175068 (6) Mildice, J. "Bidirectional Power Converter Control Electronics," NASA CR-175070 (7) "High Frequency Power Distribution System" NASA CR-175071 (8) Hansen, I.G., "Description of a 20 Khz Power Distribution System" NASA TM-87346 (9) Hansen, I.G. and Wolf, F.J. "20 Khz Space Station Power System," NASA TM-88801, 1986. 19th Annual Electronics and Aerospace Systems Conference, Sept 8-10, 1986. (10)Hansen, I.G. and Sundberg, G.R. "Space Station 20 Khz Power Management and Distribution System." NASA TM-87314. 1986 IEEE Power Electronics Specialists Conference (11)Zelby, L.W., Mathes, J.B., and Shawver, J.W., "Transmission Line Design for a Power Distribution System at 20 Khz," NASA CR-3987, July 1986. NASA Contract NAG3-508 1987 (12) Tofigh, F., "208 VAC, 20 Khz Hybrid Remote Power Controller," Energy-New Frontiers, 22nd IECEC, AIAA, New York. (13) Temple, V.A.K. "MOS COntrolled Thyristors in Energy Conversion Systems," Energy-New Frontiers. 22nd IECEC, AIAA, New York (14) Mildice, J., Schreiner, K. and Woff, F., "Control Considerations for High Frequency, Resonant, Power Processing Equipment Used in Large Systems," NASA TM-89926. Energy-New Frontiers, 22nd IECEC, AIAA, New York (15) Lipo, T.A. and Sood, P.K. "Study of the Generator/Motor Operation of Induction Machines in High Frequency Link Space Power Systems," NASA CR-179600, 1987. 1988 (16) Sood, P.A., Lip, T.A., and Hansen, I.G. "A Versatile Power Converter for High Frequency Link Systems," IEEE Trans. on Power Electronics, Oct 1988 (17) Hansen, I.G. "Status of 20 kHz Space Station Power Distribution Technology," IEEE Applied Power Electronics Conference, APEC 88 (18) Renz, D. D., "Power Components for the Space Station Power Distribution System," IECEC 1988, July 31-Aug 5 (19) Hansen, I.G., "Power Distribution Technology for Aerospace Applications," Power Magazine, July 1988 (20) F, Sgebg Tsaum, F.C. Lee "Computer Modeling and Simulation of a 20 Khz AC Distribution System for Space Station," IECEC, 1988, pp 338-344. (21) O. Wasynczuk, PC Krause "Simulation and Control of a 20 Khz Spacecraft Power System" IECEC, 1988, pp 663-669. (22) F. Tsai, F.C. Lee "Effects of Load on the Performance of the Mapham Resonant Inverter," IECEC, 1988, pp. 655-661. (23) K. Schreiner, "AC Bidirectional Motor Controller," IECEC 1988 (24) O. Wasynczuk, PC. Krause "Dynamic Characteristics of a 20 Khz Resonant Power Systems: Fault Identification & Fault Recovery" IECEC, 1988, pp 663-669. 1989 (25) Mildice, J. "In Space, its 20 khz ac Power," Powertechnics Magazine, Feb 1989, pp 29-32 (26) Sundberg, R., Brush, A., Patterson, A. Button, R. "Distribution and regulation Characteristics of a Mapham Inverter," 24th IECEC, Aug. 6-11, 1989 (27) Brush A., Sundberg, R. and Button R., "Frequency Domain Model of Parallel Series Output-Connected Mapham Inverter," 24th IECEC, Aug. 6-11, 1989. (28) Hansen, I.G., "Variable Speed Induction Motor Operation from a 20 Khz Power Bus," 24th IECEC, Aug 1989 (29) Leskovich, R. and Hansen, I.G. "The Effects of Nonlinear Loading upon the SSF 20 Khz Power System," 24th IECEC, Aug 1989 (30) R. Sundberg, A. Brush, R. Button & A. Patterson "Distribution Regulation Characteristics of a Mapham Inverter." IECEC 1989 (31) R. Button, A. Brush, R . Sundberg "Development and Testing of a 20 Khz Component Test Bed" IECEC, 1989 (32) P. Jain, J. Bottril "An Improved Mapham's Inverter for High Frequency Space Power Conversion," IECEC, 1989, pp. 611-616 (33) K. Schreiner, "AC Bidirectionaly Motor Controller," IECEC, (34) S. K. Sul, I. Alan & T.A. Lipo "Performance Testing of a High Frequency Link for Space Power Distribution System" IECEC 1990 (35) O. Wasynczuk, PC. Krause "Steady-state and Dynamic Characteristics of a 20 Khz Space Craft Power Systems: Control of Harmonic Resonance" IECEC, 1990, pp. 471-476. ------------------------------ End of Space Digest Volume 16 : Issue 337 ------------------------------