Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V16_3/V16NO343.TXT

Internet Message Format | 1993-07-13 | 36KB

Date: Sat, 20 Mar 93 05:20:01
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V16 #343
To: Space Digest Readers
Precedence: bulk


Space Digest                Sat, 20 Mar 93       Volume 16 : Issue 343

Today's Topics:
                                 DC-X
             Flight time comparison: Voyager vs. Gallileo
                              Grand Plan
               Just a little tap (was Re: Galileo HGA)
   LPI, UAz, and ET resources (was Re: plans, and absence thereof)
                     One Ticket To LEO, Please...
         Predicting gravity wave quantization & Cosmic Noise
                            Space markets
                 SSTO: A Spaceship for the rest of us
                         Veneraforming (sp?)
                       Very Large Mirror wanted
    Water Simulations (Was Re: Response to various attacks on SSF)
                  Why use AC at 20kHz for SSF Power?

    Welcome to the Space Digest!!  Please send your messages to
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----------------------------------------------------------------------

Date: 19 Mar 93 23:15:31 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: DC-X
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (FRANK NEY) writes:

>I just wish we could fund DC-X and DC-Y privately.  Unfortunately,
>CSLA makes this a near-impossibility.

How do you figure that?

Shuttle based Freedom logistics will cost about $80 billion. That's more
than enough to justify development of lots of cheaper alternatives. All
NASA need do is buy supply launches from the cheapest provider.

   Allen
--
+---------------------------------------------------------------------------+
| Allen W. Sherzer | "A great man is one who does nothing but leaves        |
|  [e-mail]     |  nothing undone"                                       |
+----------------------89 DAYS TO FIRST FLIGHT OF DCX-----------------------+

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

Date: Fri, 19 Mar 1993 21:50:43 GMT
From: Henry Spencer <[e-mail]>
Subject: Flight time comparison: Voyager vs. Gallileo
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Ron Baalke) writes:
>>No, the fundamental problem is that Galileo really could have used a
>>trip to the fat farm. ...
>>weight growth during development was nothing short of spectacular.
>
>Not true.  Galileo is a heavier spacecraft than Voyager, by design.
>Galileo is an orbiter, whereas a flyby spacecraft can be built much smaller.
>Also, Galileo had to be redesigned so many times because of
>problems with the Shuttle and the Centaur/IUS, and its mass was even
>reduced at one point.

Certainly Galileo is flying a more ambitious mission, and has had numerous
problems with its launcher changing underfoot.  However, I stand by my
original comment:  it's very overweight compared to the original concept,
and this is a major reason why it strained launcher capability so badly.
Just because it was meant to go up on Shuttle/Centaur didn't mean they
*had* to design it to the very limits of what that combination could
launch.  The other two S./C. payloads, Ulysses and Magellan, made the
transition back to IUS easily because they didn't push the limits.

There's nothing about the Jupiter Orbiter/Probe mission that required
such an elephant of a spacecraft.  But if you always resolve conflicts
between science return and weight control in favor of science, that's
what happens...
--
All work is one man's work.             | Henry Spencer @ U of Toronto Zoology
                    - Kipling           |  [e-mail]  utzoo!henry

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

Date: 19 Mar 1993 21:40 UT
From: Ron Baalke <[e-mail]>
Subject: Grand Plan
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Henry Spencer) writes...
>CRAF was cancelled because it had overrun its budget massively, and Congress
>was giving clear signals that this would not be tolerated.  This had nothing
>to do with the manned/unmanned wars.

CRAF/Cassini did not overrun its budget.  Congress cancelled CRAF because
they wanted to same some money in the short term.  In addition to cancelling
CRAF, they reduced Cassini's budget for that fiscal year.  This reduction
caused the postponement of the launch date and extended the overall mission
a couple of years.  Normally, abrupt changes to the mission like this drives up
the cost, but JPL has adjusted and made changes liking reducing the mass of
the spacecraft.  Cassini has and continues to be under budget.
     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | [e-mail]
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | Don't ever take a fence
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | down until you know the
|_____|/  |_|/       |_____|/                     | reason it was put up.

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

Date: 19 Mar 1993 16:55:08 -0500
From: Pat <[e-mail]>
Subject: Just a little tap (was Re: Galileo HGA)
Newsgroups: sci.space

Um Nick,  How does a 1,000 fold loss of Data transmission capacity, that
was fully booked, condense to only a 30% loss of Mission?  by
PRing the loss.   They are saying, well, if we only
can get x of this, and y of that, it adds up to 70%.

it's remarkable how much will get saved,  but  it's not 70%.

pat

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

Date: 19 Mar 1993 16:48:46 -0500
From: Pat <[e-mail]>
Subject: LPI, UAz, and ET resources (was Re: plans, and absence thereof)
Newsgroups: sci.space,alt.sci.planetary

In article <[e-mail]> [e-mail] (Bill Higgins-- Beam Jockey) writes:
>
>Indeed LPI has been involved in "prospecting" for quite some time.

I am glad University of Arizona is producing a "Miners" encyclopedia,
but I'd think a place like LPI would be a good place to be
cranking out prospecting missions.  Lunar Observer should be their
program.
They should have been leading the lunar rover programs like ROcky
and pushing for continued applications for the LEM, etc.

JPL should push basic science, LPI should be looking at resource
mapping and exploitation developement.

pat

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

Date: 19 Mar 93 23:45:19 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: One Ticket To LEO, Please...
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Kieran A. Carroll) writes:

>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...
>Thus, 1973$300/lb would be equivalent to between 1993$1200/lb
>and 1993$1800/lb.

Quite right. BTW, a quanity purchase of existing expendables based on
40 year old technology would be pretty close to that.

>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).

Except that the $300/lb was intended to be shuttle's OPERATIONAL
cost, not its marginal cost. Measured apples to apples it missed
by an order of magnitude.

>The Shuttle's detractors like to use the $500M/flight
>price tag

Seems a reasonable compromise. Granted it assumes Shuttles are free
and didn't cost anything to develop (which I wish somebody would
explain to me) but it will do.

>(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),

Wait a second there. To get a cost of $1B you don't need to include
all manned space flight. All you need do is add the operational costs
to a reasonable amortized development and procurement cost and include
the interest on the bonds used to finance the whole thing.

Granted, NASA doesn't account for anything that way but they would
toss you or I in jail if we didn't.

>in current dollars,
>and then pretend that the $300/lb cost estimate was also in current

I haven't seen anybody do that in a long time. All you need do is
simply compare it to the competion which charges 75% less.

>dollars, to "prove" that manned spaceflight projects always have
>cost over-runs of 3000%.

Not manned space flight. Most NASA launches are just as expensive.

This isn't a manned vs unmanned space arguement.

>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...?

I would say that a space station costing $8B in 1984 and yet costs
$40B six years later (when the CPI was only up by about 20%) has
indeed exceeded its budget by a few hunderd percent. Even if you use
the numbers NASA was quoting a few years later it is still overrun
by well over 100%.

    Allen

--
+---------------------------------------------------------------------------+
| Allen W. Sherzer | "A great man is one who does nothing but leaves        |
|  [e-mail]     |  nothing undone"                                       |
+----------------------89 DAYS TO FIRST FLIGHT OF DCX-----------------------+

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

Date: Fri, 19 Mar 1993 20:39:20 GMT
From: Cameron Randale Bass <[e-mail]>
Subject: Predicting gravity wave quantization & Cosmic Noise
Newsgroups: sci.space,sci.astro,sci.physics,alt.sci.planetary

In article <[e-mail]> [e-mail]. (Thomas E. Smith) writes:
>
>>In article <[e-mail]>, [e-mail]. (Thomas E. Smith) writes:
>>> same time (I forget if gravity travels the speed of light, or is instantly
>>> propagated)
>
>Ok, you're right about gravity travelling the speed of light, but I don't see
>why that is required to produce the kind of gravity waves we're trying to
>detect. What I think they are trying to detect are things like an extreamly
>massive black hole being orbited by a neutron star, for example. If the black
>hole is so much more massive than the neutron star, it will hardly move. So
>this kind of thing happens:
>
>    __NS__        ______          ______
>   /      \      /      \        /      \
>  |   BH   |    NS  BH   |      |   BH   |
>   \      /      \      /        \      /
>     ----          ----            -NS-
>
>    Earth         Earth           Earth
>
>
>    Weak          Medium         Strong
>    Force         Force           Force
>


      I am not sure that this is exactly what we're looking for,
      but how does one measure the differential 'force'
      of the attraction?  In all cases, it is probably negligible anyway.
      Heck, the sun's quadrapole moment probably swamps the
      contribution of such orbital systems at any distance from us.
      (I think we may be looking for something quite a bit more
      violent).

>This would produce a weakening and strengthening of the gravitational
>wave from the black hole & neutron star system. I chose the large masses so
>that maybe they could be detected here. This is should produce the very weak,
>and very long waves that they are trying to detect. It seems to me that if
>they were trying to detect gravitons, those would be extreamly short. I do
>agree with you that gravity travels the speed of light, but in this case, why
>does it matter? In what case would it matter?

     Not really wishing to start another discussion on what the 'speed'
     of gravity means, if the waves travelled instantaneously, how
     does one define or detect a 'wave'?  Apart from the fact that I suspect
     propagation speed determines the detection through the doppler
     shift, it seems to be crucial in all cases.

     This points to another question that I had if my first two
     were answered.  I'll pose it anyway.  Let's say a gravitational
     wave comes through and whacks a spacecraft (ripples in space, and
     all that).  For simplicity, we'll think of wavefront normal to the
     line connecting the spacecraft and the earth.   Presumably the radio
     connection then sees a doppler shift due to the 'oscillation'.
     Why does the oscillation not identically nullify the doppler shift
     all the way back to the receiver owing to the effect of the wave
     on the radio signal?  Is that the case, and is that why they're
     using three craft?

                            dale bass

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

Date: 19 Mar 93 22:46:03 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: Space markets
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (INNES MATTHEW) writes:

>Actually, (not very reliable) rumor has it that NASA is selling ad
>space on the Shuttle's ET.  Rumor also has it that the first customer
>is to be Arnold Schwartzeneggar's new movie.

Close. It is going to be on the first Comet mission.

  Allen

--
+---------------------------------------------------------------------------+
| Allen W. Sherzer | "A great man is one who does nothing but leaves        |
|  [e-mail]     |  nothing undone"                                       |
+----------------------89 DAYS TO FIRST FLIGHT OF DCX-----------------------+

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

Date: Fri, 19 Mar 1993 23:11:32 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: SSTO: A Spaceship for the rest of us
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Gary Coffman) writes:

>Satellites are certainly a US dominated area, but commercial
>launch services show little indication of being profitable
>activities absent government

One provides is breaking even and another only lost a small amount of
money. All without government subsidies. Reduced costs would promote
more activity and increased sales.

The main problem with launch provider profitability is the government
policies you have supported so strongly.

>Bad numbers. The $1500 represents one first class ticket to
>Australia while the $500 million (an inflated number by many
>people's calculation)

Perhaps you could explain just how those people concluded that
price was inflated? Take the amount spent on Shuttle operations
every year and divide by the flight rate and you get a sum larger
than $500M. People who quote lower costs do so by picking and choosing
what costs they want to include.

If a contractor accounted costs the way Shuttle does they would
be thrown in jail. If NASA accounted its costs the way it insists
its suppliers account for costs, you would get a cost far in
excess of half a billion per flight.

>reasonable marginal costs of $110 million for a Shuttle flight,

Why should Shuttle only pay the marginal costs? how do you jsutify
the billions in Shuttle costs your ignoring?

>the cost per pound is $2,750. Advantage is still to the airliner,
>but it never tops 600 MPH and lets it's *wings* do most of the
>work of supporting it's weight.

Irrelevant. The airliner also is under power for far longer amounts
of time.

Both are at the same level of complexity and unit cost.

>It should be remembered, however,
>that projected Shuttle costs per pound were $300 at a similar stage
>of it's development.

Ah yes, the old "shuttle failed so everything will fail" arguement.
We have already covered this Gary.

  Allen
--
+---------------------------------------------------------------------------+
| Allen W. Sherzer | "A great man is one who does nothing but leaves        |
|  [e-mail]     |  nothing undone"                                       |
+----------------------89 DAYS TO FIRST FLIGHT OF DCX-----------------------+

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

Date: 19 Mar 1993 17:48:24 GMT
From: CLAUDIO OLIVEIRA EGALON <[e-mail]>
Subject: Veneraforming (sp?)
Newsgroups: sci.space

Let us Veneraform Earth!! Errr... did I say that right???

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

Date: Fri, 19 Mar 1993 21:48:44 GMT
From: [e-mail]
Subject: Very Large Mirror wanted
Newsgroups: sci.astro,sci.space

Astronomy Ireland is seeking any large mirrors that may be going "cheap"
anywhere in the world for a project to build a major public observatory.

Do you know of any 100-inch (+/- a factor of 2 say) mirrors not in use?

Perhaps such large mirrors might be available as a result of observatories
closing down or changing from one design to another. Or, perhaps more than one
primary was made in projects to build 'off the shelf' observatories (Univ. of
Australia had a 120-inch altaz designed to be copied at low cost) or as
replacements or back-up mirrors? We want to hear about anything at all.

Two projects we have heard about are the 72-inch mirrors of the MMT (what will
happen to them when the new single mirror replaces them?) and what has happened
to the old 98-inch mirror in the Isaac Newton Telescope which was moved to the
Canary Islands and had a new 100-inch mirror made for it in the process?

-Tony Ryan, "Astronomy & Space", new International magazine, available from:
Astronomy Ireland, P.O.Box 2888, Dublin 1, Ireland.
6 issues (one year sub.): UK 10.00 pounds, US$20 surface (add US$8 airmail).
ACCESS/VISA/MASTERCARD accepted (give number, expiration date, name&address).
Newslines (48p/36p per min): 0891-88-1950 (UK/N.Ireland) 1550-111-442 (Eire).

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

Date: Fri, 19 Mar 1993 22:44:34 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: Water Simulations (Was Re: Response to various attacks on SSF)
Newsgroups: sci.space

In article <1o8iu1$[e-mail]> Dave Akin <[e-mail]> writes:

>I think you are selling our EVA experience way too short here - if you
>think we've only done "the most simple EVA"

Sure we have done complex things but those tend not to go the way
the training said they would. None of the satelite repair/retrieval
EVAs went as planned.

The Intelset experience indicates that there will be lots of problems
assembling Freedom.

>There is absolutely nothing planned for the space station that
>couldn't be readily performed in EVA.

I suspect that is true but nobody knows: NASA has refused to do the
work needed to find out.

   Allen
--
+---------------------------------------------------------------------------+
| Allen W. Sherzer | "A great man is one who does nothing but leaves        |
|  [e-mail]     |  nothing undone"                                       |
+----------------------89 DAYS TO FIRST FLIGHT OF DCX-----------------------+

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

Date: 19 Mar 93 12:38:20 GMT
From: Pat <[e-mail]>
Subject: Why use AC at 20kHz for SSF Power?
Newsgroups: sci.space

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.

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.





|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 would hope so.  A library is no place for political correctness.
What kind of mindset, would exist where a libraryt would not
have outside opinions and sources of information.


|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."
|

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.

Of course the phrase "built not to work"  was my exact criticism
of SSF.  Funny to see LeRC making that claim against MSFC.

AS you see,  it's not the paperwork, it's the product that is the final
matter.

|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

This is of course the same environment used by DC-DC converters
in PC power supplies.

|
|The DC Alternative
|
|As the system grows, complexity increases rapidly. When we add
|and DC-DC converters are added at their inputs.
|You can see that our simple, ideal DC system has grown to include
|a lot of power processing equipment.
|

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?

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.

|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?

| 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.
| 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.   :-)

|
|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.

|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.

|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.

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.



|
|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?

|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.

pat

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

From: Steinn Sigurdsson <[e-mail]>

Newsgroups: sci.space
Subject: Re: SSTO: A Spaceship for the rest of us
Date: 19 Mar 93 12:14:43
Organization: Lick Observatory/UCO
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Message-Id: <[e-mail]>
References: <[e-mail]> <[e-mail]>
    <[e-mail]>
Nntp-Posting-Host: topaz.ucsc.edu
In-Reply-To: [e-mail]'s message of Fri, 19 Mar 1993 18:04:46 GMT
Sender: [e-mail]
Source-Info:  Sender is really [e-mail]

In article <[e-mail]> [e-mail] (Henry Spencer) writes:


   Second, and more serious, I quoted LOX at five **CENTS** a pound, not
   five dollars a pound.

Got a source for that number? You can't get drinking water for 5c/lb
in most places! Rule of thumb I remembered from few years ago was that
LN2 is somewhat cheaper then milk per gallon, delivered in hundred
gallon loads - LOX is obviously more expensive. Are the economies
of scale really that much better when you order 100,000 pounds at
a time?

|  Steinn Sigurdsson    |I saw two shooting stars last night        |
|  Lick Observatory    |I wished on them but they were only satellites    |
| [e-mail] |Is it wrong to wish on space hardware?        |
| "standard disclaimer"    |I wish, I wish, I wish you'd care - B.B. 1983    |

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End of Space Digest Volume 16 : Issue 343
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