Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V16_3/V16NO364.TXT

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Date: Thu, 25 Mar 93 05:35:30
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V16 #364
To: Space Digest Readers
Precedence: bulk


Space Digest                Thu, 25 Mar 93       Volume 16 : Issue 364

Today's Topics:
       Ah, Ceesco! Ah, Pancho! (was Re: 20Khz Power supplies.)
                      plans, and absence thereof
                       Plans and Clueless -isms
                  Response to various attacks on SSF
                  Why use AC at 20kHz for SSF Power?

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----------------------------------------------------------------------

Date: Wed, 24 Mar 1993 17:05:05 GMT
From: fred j mccall 575-3539 <[e-mail]>
Subject: Ah, Ceesco! Ah, Pancho! (was Re: 20Khz Power supplies.)
Newsgroups: sci.space

In <[e-mail]> [e-mail] (Bill Higgins-- Beam Jockey) writes:

>In article <[e-mail]>, [e-mail] (fred j mccall 575-3539) writes:
>> In <[e-mail]> [e-mail]
>(Roland Dobbins)  [formerly The Zombie Who Would Not Die, but I think
>that software problem has been fixed] 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.

>Fred, or Roland, do you want to tell us the story?  Or should it
>remain a dark secret to which you guys will continually make
>mysterious allusions?

Well, you kind of have to understand how BIX was (is?) organized in
order to understand the problem.  In any case, the short version is
that several years ago when I had a BIX account, I upset one of the
Powers That Be (who is no longer there, I'm told) there by disagreeing
with a big chunk of his policy prescriptions.  Several of his Loyal
Minions (moderator cum censor) made an effort to get me thrown off the
system.  This eventually happened, but in the event they couldn't
point to anything I had done that was wrong (other than daring to
disagree and being publicly vocal about it), so they wound up
refunding my money and using the "30 day cancellation for no reason"
clause in the contract.  Nothing like an 'Information Exchange' system
that doesn't want users exchanging information about the system
itself.

There were half a dozen people (that I know of) who had their accounts
cancelled around the same time in an effort to quell the criticism or
intimidate people into at least keeping it in private.

[This is the short version.  You really kind of have to have been
there to see just how bad things were at the time, what with entire
newsgroups (the BIX analog to them, actually) being erased and
restarted because of criticism of the management.  This happened in

one group 3 times, after which they redefined its charter so that it
was no longer on topic to ask questions about BIX management but only
about how to use the software.  I don't know if things have improved
with the departure of the individual I saw as generating the problems
or not, as I haven't bothered to check back since.  I just recently
found out (within the last week) that the person responsible for
cancelling my account and for the policies that were creating all the
discussion is no longer there.  BIX has also changed ownership since
then, so there's no telling if that sort of policy is still their way
of dealing with disagreements with management policy or not.]

--
"Insisting on perfect safety is for people who don't have the balls to live
 in the real world."   -- Mary Shafer, NASA Ames Dryden
------------------------------------------------------------------------------
[e-mail] - I don't speak for others and they don't speak for me.

------------------------------

Date: Wed, 24 Mar 1993 17:25:23 GMT
From: fred j mccall 575-3539 <[e-mail]>
Subject: plans, and absence thereof
Newsgroups: sci.space,alt.sci.planetary

In <[e-mail]> [e-mail] (Nick Szabo) writes:

>I'm not very impressed by the old so-called "prospecting" work from
>LPI, it has almost all been geared towards industrially silly processes on
>the moon as an excuse to put astronauts there.   There isn't, from
>what I can tell reading their papers, any significant input on oil
>companies.  (It would be great, for example, to get oil company
>engineers designing comet volatile extraction equipment, but LPI
>hasn't done anything of the sort).

Translation:  It doesn't support the Nick Szabo Vision of the Future
to Which You MUST Subscribe.  It wants to do silly things like put
*people* in space, and on the moon yet, of all places.  And most
importantly to Nick, it seems, it doesn't give work to JPL.

>Here's where JPL can come in: take a fresh approach that encompasses
>the vast variety of solar system environments instead of the narrow
>Apollo-inspired, regolith-based studies that have been done so far.
>"Extract He-3 from regolith.  Get LOX from regolith.  Build solar
>power satellites from regolith."  The lack of imagination, comprehension
>for economics, and plain incompetence in the so-called "space
>resources" work to date is astounding.  There is _plenty_ of room for
>fresh minds here, and JPL with its planetary scientists, microgravity
>scientists etc. is in a good position to move in and revolutionize the
>field, and the entire face of space development, if it so wishes.

Yes, how unimaginative of them to have a plan different than the
Szabo-approved Vision of the Future to Which YOu MUST Subscribe.

--
"Insisting on perfect safety is for people who don't have the balls to live
 in the real world."   -- Mary Shafer, NASA Ames Dryden
------------------------------------------------------------------------------
[e-mail] - I don't speak for others and they don't speak for me.

------------------------------

Date: 24 Mar 93 17:04:43 GMT
From: Del Cotter <[e-mail]>
Subject: Plans and Clueless -isms
Newsgroups: sci.space

In article <1ol3mk$[e-mail]> [e-mail] (Pat) writes:

> If aluminum was noted during roman times,

It wasn't.  There is one claim of a mysterious metal, the producer of
which said he got from clay.

>then it indicates it needed even less of a technology base to extract
>then I guessed.

You guessed wrong.  There is no elizabethan (I) aluminium in the Tower
of London.

>I guess Bronze age technologies could reach it.

Ouch!  You have no idea how impossible this is.  Al is hellishly
difficult to extract from its oxides.

>Probably the Indians or Arabs also had identified aluminum.

No, no, no!

>It probably wasn't useful though given it's nearly difficulty to work.
>Plus other metals were much cheaper to extract and much
>better in their character.

I guess you didn't catch the smiley in my original post.  Here it is
again.

>Tell me more :-)

My point was, when bashing someone elses grasp of history, it's a good
idea to check your own facts.

Now, back to the "plan" flame.

--
 ',' ' ',','  |                                                  |  ',' ' ',','
   ', ,','    |       Del Cotter       [e-mail]      |    ', ,','
     ','      |                                                  |      ','

------------------------------

Date: 24 Mar 1993 13:27 EST
From: "David B. Mckissock" <[e-mail]>
Subject: Response to various attacks on SSF
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Pat) writes...
>Dave,  You mention that Level 2 is responsible for integrating
>the level three centers and contractors, but what I read in the
>trade press
>is that there is a feeling that there is a lack of integration,
>and that no contracts have been let to ensure all the work packages
>and systems  interface completely.
  << Example of Saudi engineering interface foulup deleted  >>
>
>Given the incredible diversity in centers contractors and
>work packages
>and flight packages,  it is possible for something small to
>get dropped on the floor, and be a large problem.
>
>Is there a single contract that specifies integration?  Reston doesn't
>have the man power to conduct integration, to the best of my
>knowledge.
>

First, I apologize for the delay in my response, our
"low bidder" machine with the feed to USENET is running
a week behind on postings.

A couple of years back, Level II got a Contractor to help
them do their job. This Contract was called the PSC
(Program Support Contractor), and Grumman got the job.
Later, recognizing that Level II needed to focus more
effort on SSF program integration, the name of this
Contract was changed to SSEIC (Space Station Engineering
Integration Contractor), to reflect the change in focus
of the Contract. Grumman has a small army of personnel
in Reston, and they have field offices at MSFC, JSC, & LeRC.

>I don't dispute that there are a lot of requirements and
>a detailed tracing system,  but oftentimes requirements
>run to two different contractors,  or two different systems.
>The only way to make sure it's really met is to have the
>parties working together,  and given the management structure,
>horizontal flow is restricted.

The parties *DO* work together. Let's take a specific
example. Currently, there is an issue between WP-2 and
WP-4 (JSC & LeRC) concerning a possible thermal
distortion problem. WP-4 is responsible for the structure
*outboard* of the alpha gimbal, and WP-2 is responsible
for the structure *inboard* of the alpha gimbal (the alpha
gimbal is the joint that rotates 360 degrees each orbit
to keep the array's sun-tracking). The WP-2 concern is
that the WP-4 struts that attach the *outboard*
structure to the alpha gimbal see a much different thermal
environment than the struts that attach the *inboard* truss
structure to the alpha gimbal, such that the alpha gimbal
might see thermally-induced stresses that it's not designed
for (the different thermal environment is because the stuff
outboard of the alpha gimbal is always pointed at the sun,
whereas the stuff inboard of the alpha gimbal is always
pointed at the earth).

The WP-2/4 Chief engineers discuss issues like this in
their periodic telecons. Also, this issue is on the
agenda for the next WP-2/4 bi-lateral scheduled for later
this month. Both the WP-2 and WP-4 Program Managers attend
these bi-laterals, and they put their "John Hancock" on
any agreements they reach. The results of these bi-laterals
get presented to a Level II group (called the IMR, Interface
Managers Review), so Level II management is cognizant of
what's happening (Level II minions also attend the bi-laterals
and report back to their management on what the work packages
are doing). Finally, if issues cannot be settled in a
bi-lateral, they get forwarded to Level II (like when your
children can't agree on something, they get Mom or Dad to
arbitrate).
>Engineering judgement specified two fault tolerance.
>SHouldn't it have been in there all the time?

Sure, it would have been darn nice to always have maintained
a two-fault tolerance requirement. However, as the fiscal
situation was a problem, the Turbo Team & Restructuring
activities had to do something to save money, ranging from
slipping schedule to reducing scope to removing some of the
"bells & whistles", and it was decided to relieve the two
fault tolerance requirement in some areas.

>What is your degree in?

I have a degree in Mechanical Engineering from Purdue University.

>    I would expect the systems people to go to experts, to get
>detailed evaluation,  and  then conduct the trade off studies and
>form criteria  for management.

In a nutshell, you have described the process we followed
in Phase B of this program.

>    My question, is that i never heard about any criticalities that
>drove an initial selection of 20Khz power.  ...

>Instead, 20 Khz was put on the table to start and only killed
>after it proved totally unworkable.

I have a different view on history. In Phase B of the program,
many power system options were studied. For power generation,
we looked at nuclear, solar dynamic, and photo-voltaic (PV).
For the PV option, for energy storage we investigated fly wheels,
Nickel Cadmium batteries, Nickel Hydrogen batteries, and Fuel Cells.
For power distribution, many DC systems (at various voltages) and
AC systems (primarily, as I recall, at 400 Hz, 1200 Hz, 2400 Hz,
and 20 kHz).

In all of these studies, we looked at weight, cost
(both development and life-cycle), safety, and risk. Out of
these Phase B studies NASA selected the "best" system, which
was a hybrid solar dynamic and photovoltaic power system
with Nickel Hydrogen batteries, with a 20 kHz distribtuion
frequency. Two quick points on this:
 1) Notice I said "NASA selected," *NOT* "Lewis Research Center"
    selected. Over the course of Phase B, Level II (which was
    called Level B at the time and was based in JSC, not in Reston)
    participated in the selection, as well as the other NASA centers.
    As an aside, these same folks, along with the International
    Partners, were also heavily involved in the later decision
    (during Phase C/D) to change from 20 kHz to DC.

 2) The decision was fairly controversial. There were strong
    advocates in the program for both DC and 400 Hz. Nothing like
    a spirited debate among EE's about the distribution frequency
    for a power system! It was kind of like an argument on
    abortion, with heated discussions and not much middle
    ground. In comparison, the Mechanical Engineers had calm,
    rational chats about the cycle that should be selected
    for the solar dynamic system (brayton versus organic
    rankine).

Finally, 20 kHz was *NOT* dumped due to any studies showing
the system wouldn't work, and we were not having any special
development problems with our 20 kHz hardware.

As I've already posted, in the final battle of the distribution
frequency "war", Level II, WP-4, and CSA voted for a 20 kHz
distribution frequency. NASDA, ESA, MSFC, & JSC all preferred DC.
The program manager decided on DC, ending the "war" that had
lasted several years.

>When somebody is outside, and needs to carry two toolkits, that's a
>problem.   When something breaks, and you can't cannibalize between
>systems,  that's a problem.   English, metric, Mayan numbers.  it
>should be standard between all modules.  fasteners should be standardized.
>connectors should be standard.

I believe fasteners & connectors are standardized, using english
units. For example, WP-4 is building a DC-DC Converter, to
convert the 160 primary DC power to 120 VDC secondary power.
The JEM, Columbus APM, and NASA Hab and Lab modules all have
these DC-DC Converters, and they all use the same input and
output connectors, as well as the same bolts to fasten the
hardware to the module. I don't believe two toolkits
are needed metric tools, one for the International modules,
and one for the NASA modules.

>>>    3)  Total failure to practice EVA until this year.
>>Another common fiction on sci.space. NASA has two facilities
>>for practising EVA's in water tanks, one at JSC, and another
>>at MSFC. WP-4 has tested many of our EVA procedures in these
>>facilities. For example, in December 1992, we tested 22
>>[stuff deleted]
>
>I didn't know Water counted:-)  seriously.  Water is just not
>the same thing as zero-g.  It's good for analyzing real manpower
>problems,  but still the real nitty gritty occurs in space.
>
>I haven't seen anyone testing small truss builds,  or docking excercises.
>AS allen pointed out.  Flying dummy segments,  and practicing docking
>with them, and mating manuevers.

I believe the NASA position is as follows:
 - The astronauts participate in the testing of the operations
   procedures in the water tanks.
 - If they astronauts say that based on the water tank tests,
   they can "sign-off" on the their ability to perform the
   task on-orbit, then WP-4 has sufficiently verified that
   our hardware meets the assembly and maintenance
   requirements.
 - Remember, some of the astronauts who are participating in
   these tank tests are "calibrated", in the sense that they
   have trained for previous missions in the tanks, and then
   performed the actual operations on-orbit, so they have a
   feel for the "applicability/useability" of the tank test
   data as it applies to on-orbit activities.

You specifically mention truss builds & docking exercises. By
"truss builds", I assume you mean the joining of two pieces
of truss pieces on-orbit (one of the changes in restructuring
was to use Pre-Integrated Truss, or PIT, segments, such that
the truss itself didn't have to be assembled on-orbit, instead
PIT segments are simply fastened together).
Our test in the MSFC tank this
past December included the installation of a short spacer
segment (a small piece of PIT between the two solar power
modules) onto the inboard PV module truss structure.
Two methods were tested. Method 1 involved
positioning the short spacer on V-guides on the Integrated
Equipment Assembly aft bulkhead and then using the crew to
rotate the truss into the 4 docking pads on the Integrated
Equipment Assembly. Method 2 involved positioning the
short spacer within arms reach of 2 crewmembers in
portable foot restraints, who then move the short spacer
toward their feet into the Integrated Equipment Assembly
docking pads. The preliminary report on these tests says,
and I quote "This method [#2] of a short spacer installation
was considered easy by test subjects from the standpoint
of EVA operations. Crew test subjects commented that the
deciding factor for using Method 1 or Method 2 should be
the RMS operations and the associated clearance requirements,
since the EVA operations for both methods appeared
feasible."

I think you'll agree these words don't inspire a manager
to run out and set-up an on-orbit test to practise
these EVA maneuvers.

I don't know what you mean by testing "docking." The docking and/or
berthing process doesn't involve EVA.

------------------------------

Date: Wed, 24 Mar 1993 17:50:55 GMT
From: fred j mccall 575-3539 <[e-mail]>
Subject: Why use AC at 20kHz for SSF Power?
Newsgroups: sci.space

In <[e-mail]> [e-mail] (Pat) writes:

>In article <[e-mail]> [e-mail] (David B. Mckissock) writes:
>|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

>I am Heartened to see some attempt at a technical response on
>20KHz power from someone who was involved in SSF design issues.
>Had Something of this nature popped up early in the thread,
>rather then Fred McCall venting his spleen,  a much higher level
>of discourse may have occured.

Well, Pat, perhaps the lesson you should learn from this is that when
you post bile you get spleen in return.  Frankly, the tone of your
postings (pretty much all of them) is such that 'spleen' seems to be
what you most deserve.  Go ahead, Pat.  Try posting like an adult for
a while without all the ad hominem attacks on people and insulting
tone that lards your notes whenever someone dares to disagree with you
or you don't happen to know what you're talking about.  I *dare* you.
I *double* dare you!

>I would note from the start, that I would be very skeptical of
>the motives of the author of this paper.  Being a staffer
>at GD,  they would have an interest in advocating a high cost
>solution, that pumps money into GD coffers,  as opposed to
>a soulution that only allows them to make a 15% markup on
>Off the shelf hardware purchase.

Was GD supposed to be the one producing the 20 kHz power system?

>|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."
>|

No, the paperwork was *not* good because the requirements were bad.

>Ah,  the but the paperwork was good, the requirements document
>had been flowed down into each sub-contract and a full tracability
>matrix had been done.   How could it not work.

Bad requirements.  Do you know *anything* about engineering, Pat?

>How did skylab cope with the DC problems?  Skylab was
>fairly big,  it had several arrays,  and various power demands.
>Anyone have the historical background?

Skylab was small and underpowered compared to what SSF was supposed to
be.

>Also, despite what GD may say about DC power complexity,  Somehow
>it does seem to power a large fraction of our industrial equipment,
>every vehicle in america,  and numerous LARGE transportation
>systems.   I would guess that the complexity of the power
>system of METRO is at least as large as that of SSF.

Gee, and here all this time I thought my vehicle was powered by an
internal combustion engine, except for a very small electrical system.
What kind of car are *you* driving, Pat?

>|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
>stuff deleted, for a  bit....
>| o  Rotating machines - "want to operate" with AC. Alternators
>|
>Has anyone made catalog spec 20KHz rotating gear?

Well gee, Pat, you must live in a real chicken-and-egg dilemma for
your entire life.  It ain't gonna show up in the catalogs until it's
being used, and you don't want to use it until it shows up in the
catalogs.  Back to the caves, boys!

>| 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.
>|

>Actually, i would imagine that 20Khz transformers would not
>be terribly efficient,  the Reactance of these is proportional
>to frequency.  I'd imagine the impedance losses,  may make High Frequency
>Transformers actually imprcatical.   DSoes anyone have the idea
>of the Inductance of a 50 KW transformer coil?  assume 208/480 volts,
>three phase.

Somehow I suspect that the people doing the studies probably looked at
this issue, and I suspect they used a better tool than "Pat's
imagination".

>| 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

>I don't know much about zero current switching, i would assume
>these apply to Electronic switching equipment?

>|
>|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.

>I don't know why anyone is worrying about delivery costs,
>after all,  the shuttle flies up with dead head space, and
>that's free.  I mean if they have to haul up the module,
>why worry about some extra weight,  i mean it's marginal
>cost is only a little hydrogen.   :-)

If this were convincing logic, we'd be hauling whatever we pleased to
orbit, since it would always fit in the "deadhead space".  The point,
Pat, is that if you don't have to lift X pounds of one thing you can
lift X pounds of something else if you want to.

>|
>|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

>I really don't understand what he's trying to say here.  can anyone elucidate.

He's talking size/weight of the components.  The shrinkage is
exponential until roughly 10 kHz, at which point it flattens out.

>|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).
>|
>I've worked in lots of industrial plants with louder things then
>some power noise.  Seriouly, i can't believe this would ever be
>a major criteria.

Yes, but one would like not to have all that loud racket and vibration
on a space station.  Background noise *better* be a serious criteria,
since people are going to be stuck in that environment for months at a
time.

>|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.
>|

>Gee, I look in a lot of electrical industry magazines,  and I see
>a lot of articles on problems caused by DC power processing.
>A large number of PC's plugged into one room, generate enough
>non-linear current and harmonic noise to be destroying conductors,
>transformers and switch gear.

Gee, your point?

>Plus, i have to wonder what kind of body of design data exists at
>50 KW.
>|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

>So how does efficiency wise a DC-DC converter stack up against
>a motor/generator pair.  For large power generation i'd imagine
>it would be a lot more reliable, and able to handle transients a lot
>better.

One would like to reduce high-inertia rotating equipment to a minimum
on a space station, Pat.  Otherwise, you spend a lot of fuel
cancelling out spins imparted to the station by rotating equipment.
And solid state is always more reliable than anything involving moving
parts, as well as easier to repair/replace.  The equipment I used to
work on in the Navy took the 440 3-phase from ship's supply, used a
motor generator set to get DC (what we called 'quasi-DC', actually),
then used a solid state inverter set to convert it to high-current DC.
This was then reconverted to AC elsewhere in the system as needed.
Would you consider 1/4 Megawatt as 'high power'?

>|
>|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
>|
>|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
>|the PMC station), that means a savings on the PMC station of
>|about $25 million. If we also add total life cycle costs

>Does that mean we are looking at 50,000 dollars/watt
>costs deployed?

>|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.
>|
>Most of what?  the weight savings?

Are you following this thread at all, Pat?

>|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

>So how do these guys filter on lab surface applications?
>Dennis also has some good stories of Science criteria for
>micro-gravity that the experiment packages were violating.
>Somehow i wonder about the rigor of these criteria.

>|
>|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.
>>


>Interesting,  most of these papers are either NASA reports, or
>IECEC papers.  Kinda a small community.

Well, that sure invalidates everything, doesn't it, Pat?

--
"Insisting on perfect safety is for people who don't have the balls to live
 in the real world."   -- Mary Shafer, NASA Ames Dryden
------------------------------------------------------------------------------
[e-mail] - I don't speak for others and they don't speak for me.

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End of Space Digest Volume 16 : Issue 364
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