Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V12_5/V12_508.TXT

Internet Message Format | 1991-06-28 | 18KB

Return-path: <[e-mail]>
X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson
Received: from beak.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr11/tm2b/space/[e-mail] (->+dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl) (->ota+space.digests)
          ID </afs/andrew.cmu.edu/usr1/ota/Mailbox/8bCXVTS00VcJ01w04u>;
          Fri,  9 Nov 1990 00:02:23 -0500 (EST)
Message-ID: <[e-mail]>
Precedence: junk
Reply-To: [e-mail]
From: [e-mail]
To: [e-mail]
Date: Fri,  9 Nov 1990 00:01:54 -0500 (EST)
Subject: SPACE Digest V12 #508

SPACE Digest                                     Volume 12 : Issue 508

Today's Topics:
                  SSME Specs
          Re: Some interesting SSME specifications.
               Re: FITS images
             Re: Theories needed on life
        Martian Canals - when did theory die?
               Re: FITS images
       Re: You Can't Expect a Space Station to be Cheap
       Re: You Can't Expect a Space Station to be Cheap

Administrivia:

    Submissions to the SPACE Digest/sci.space should be mailed to
  [e-mail].  Other mail, esp. [un]subscription notices,
  should be sent to [e-mail], or, if urgent, to
             [e-mail]

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

Date: 28 Oct 90 21:16:57 GMT
From: crash!pro-canaveral.cts.com![e-mail]  (Ken Hollis)
Subject: SSME Specs

Greetings and Salutations:

Because of enquiries (like that that follows), as the man sez, you asked for
it, you got it Toyota...

>From: [e-mail] (Russ Cage)
>Subject: Re: Some interesting SSME specifications.
>
>Anybody else notice that said propaganda sheet didn't have
>a single hard number in it?  It was all in battleship-powers
>or 747-thrusts or....
>--
>Russ Cage    Ford Powertrain Engineering Development Department

Shuttle Propulsion System

The space shuttle propulsion system consists of two large booster motors,
three space shuttle main engines (SSMEs), two orbital maneuvering system (OMS)
engines, and 44 reaction control system (RCS) thrusters.

Each booster motor measures 12 feet by 150 feet, weighs 1.3 million pounds,
and generates approximately 2.9 million pounds of thrust.  The booster also
serve as launch pad mounts for the entire vehicle and are ignited at launch
after all three SSMEs are producing at least 90% thrust (note : all three
engines are started at approximately 6.6 seconds in the order E3, E2, and E1,
and must be running correctly for the SRBs to ignite).  The solid propellant
consists of a cast mixture of ammonium perchlorate (oxidizer, 69.93% by
weight), aluminum (fuel, 16%) and iron oxide (0.07%), polymer (binder,
12.04%), and epoxy (curing agent, 1.96%).  After burnout at approximately
150,000 feet, the spent cases separate from the vehicle, arcing up to
approximately 220,000 feet before parachuting to the ocean for recovery and
reuse.

The three SSMEs burn liquid hydrogen and liquid oxygen from the external tank,
and are sequentially started at launch.  Engine thrust is throttleable.
Throttle down is necessary during initial ascent to prevent excessive
aerodynamic loading of vehicle structure and during final ascent to limit
vehicle to three g's.  Each engine is gimbaled through two planes for vehicle
pitch, yaw, and roll control.  The SSMEs steer and accelerate the vehicle to
the desired preorbit position, and shut down.  The external tank is then
jettisoned and falls into the ocean.  The OMS engines are then fired to
accelerate the orbiter to the velocity necessary to inject it into the desired
orbit.

The SSME is a liquid hydrogen / liquid oxygen engine that employs two-stage
combustion.  In the first stage, an extremely fuel-rich mixture is partially
burned in two preburners.  The resulting two gas streams are first used to
drive high-pressure turbopumps.  The fuel-rich streams are then injected into
a main combustion chamber along with coolant fuel and the required oxidizer.
There final burning occurs at a carefully controlled mixture ratio.

The SSME is rated at 470,000 pounds of thrust in a vacuum (375,000 pounds at
sea level).  The corresponds to 100% thrust and a chamber pressure of about
3,000 PSIA (Pounds Per Square Inch).  The thrust can be increased to 512,300
pounds (109%) and decreased to 305,000 pounds (65%) in about 4,700 pound (1%)
increments.  These thrust levels are referred to as Rated Power Level (RPL)
Full Power Level (FPL), Minimum Power Level (MPL) respectively (Standard power
is 104%..  Throttling is accomplished by varying the operating levels of the
preburners.  This varies the speed of the turbopumps and, therefore, the
propellant flowrates into the main combustion chamber.  To maintain the
desired propellant mixture ratio, the fuel flowrate is varied around the
oxidizer flowrate.

Specific Impulse Approximately 453.5 Seconds. Expansion Ratio 77.5 To 1
(Nozzle Exit Area VS Throat Area)

High Pressure Oxygen Turbopump (HPOTP) (100%, RPL)
                                 Main    Boost
Pump Inlet Flowrate (LB/Sec)   1072.1    109.1
Pump Inlet Press (PSIA)         379.1   3992.2
Pump Discharge Press (PSIA)    4118.4   7210.9
Pump Efficiency                   0.686    0.808
Turbine Flowrate (LB/Sec)            58.8
Turbine Inlet Press (PSIA)         5020.0
Turbine Inlet Temp (Degrees R)     1522.5
Turbine Efficiency                    0.759
Turbine Speed (RPM)               27263
Turbine Horsepower                23068


High Pressure Fuel Turbopump (HPFTP) (100%, RPL)

Pump Inlet Flowrate (LB/Sec)    149.1
Pump Inlet Press (PSIA)         222.4
Pump Discharge Press (PSIA)    6110.4
Pump Efficiency                   0.763
Turbine Flowrate (LB/Sec)        158.6
Turbine Pressure Ratio             1.411
Turbine Inlet Temp (Degrees R) 1794.5
Turbine Efficiency                0.839
Turbine Speed (RPM)           34386
Turbine Horsepower            61402

If that isn't enough numbers, I am sure that I can dig up more.  I also hope
that is technical enough, now for the "absolutely irrelevant but interesting
part"...  Both the HPOTP & the HPFTP are about the size of a keg of beer,
maybe a little larger.


ProLine:  gandalf@pro-canaveral
Internet: [e-mail]
UUCP:     crash!pro-canaveral!gandalf

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

Date: 27 Oct 90 22:00:40 GMT
From: mnetor!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Some interesting SSME specifications.

In article <[e-mail]> [e-mail] (S Schaper) writes:
>So, what would the velocity vector be after four hours of 100% thrust on the
>SSME's?

It would be whatever it was when the first one exploded, which would be
long before four hours.

The world's most durable rocket motor I know of, the RL-10, is rated to
fire for somewhat over one hour without maintenance.  This is a design
nearly 30 years old, with vast flight experience and no particular attempt
to push technology.  The SSME is nowhere near as dependable.

This sets aside the question of where you're going to find four hours of
fuel...
--
The type syntax for C is essentially   | Henry Spencer at U of Toronto Zoology
unparsable.             --Rob Pike     |  [e-mail]   utzoo!henry

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

Date: 28 Oct 90 19:45:20 GMT
From: amethyst!organpipe!argus.lpl.arizona.edu![e-mail]  (Ron Watkins)
Subject: Re: FITS images

NOAO has a publication that describes the FITS format rather nicely. If you
find that you want this publicaion, let me know and ill try to send on to you.
The basics of the FITS format are:
1) A FITS file contains header records and data records following the header.
2) A header is made up of N blocks of 36 FITS header cards.
3) A FITS header card is a 80 character ASCII string with no nl, lf or null's.
4) A card contains:
    a) A case insensitive key substring of at most 8 characters (bytes).
    b) An '=' or a ' ' in the 9th psition of the card.
    c) A value field that extends from the 10th up to 80th column OR
    d) A value field that extends from the 10th up to the comment marker '/'.
    e) Anything may follow the comment marker (normal ASCII text chars)
Some simple arithmetic: 1 block == 36 cards == 2880 bytes.
While reading the header, one should check for some standard cards which
should exist and aid in decoding the data format. These cards are marked
by their key values (which are the first 8 chars of each card). Some examples
are given below:
KEY      MEANING
SIMPLE    - Is the data integer format (T == integer, F == other)
BITPIX    - Number of bits used to represent a pixel. 8, 16, 32 are typical.
NAXIS    - Number of dimensions in the image.
NAXIS1    - Length of the first dimension. use 2-M to read up to M dimensions.
END    - Signifies the last MEANINGFULL card in the header.
Note: When reading cards, if the END card is encountered, that means that
the current block is the last before the data begins. You must finish
reading all 36 cards of the current block. The data will immediately follow
(in binary of course) and can be read with the NAXIS1 dimension traversed
fastest.

Now, I know there are lots of other things to consider, but this is the basic
elements of a FITS file. Anyone may feel free to bash my description on some
technical detail, but for what we use FITS for, this seems to work well.
                Ron Watkins
                [e-mail]

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

Date: 28 Oct 90 18:11:02 GMT
From: uceng!minerva![e-mail]  (Daniel Mocsny)
Subject: Re: Theories needed on life

In article <[e-mail]> [e-mail] (Mike Van Pelt) writes:
>There was a fascinating article in Analog a year or so ago, which
>discussed the theory that humans are actually pretty well adapted as
>cursorial hunters.  American Indians used to hunt horses by the "chase
>'em 'till they drop" method.  A manager at Unisys was written up in the
>company newsletter for running a 100 mile ultramarathon course in under
>24 hours.  He did not come in first place.  There are *very* few
>animals that can do this.

To keep things fair, let us remember that very few humans could perform
such a feat under primitive conditions. To maintain high levels of
exertion for extended periods, endurance athletes must continually
supply themselves with replacement water, electrolytes, and
carbohydrates. This is not a problem during organized competitions
with support crews giving handups of scientifically-formulated
sports drinks, etc. If endurance athletes had to forage for food
and water during ultra-marathon competitions (instead of having a
technological culture provide it for them), their performance would be
vastly compromised.

Animals probably drop from exhaustion quicker than humans because
animals aren't smart enough to discover what their performance-
limiting factors are. Humans are this smart, and they learn to
supply themselves with the necessary fluids and fuel.

For example, I have completed a number of 100-mile bicycle rides
(roughly the energetic equivalent of about a 50-mile run, although
much less biomechanically challenging than running 50 miles, since
bicycling is non-impact and non-load-bearing). With reasonable
preparatory training and adequate food and water, a 100-mile bicycle
ride is not very tough for most people who are in good health.
Without enough food and water, however, a ride of this distance
becomes literally a death march for most people.


--
Dan Mocsny                Snail:
Internet: [e-mail]    Dept. of Chemical Engng. M.L. 171
      [e-mail]        University of Cincinnati
513/751-6824 (home) 513/556-2007 (lab)    Cincinnati, Ohio 45221-0171

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

Date: 28 Oct 90 12:10:20 GMT
From: eru!hagbard!sunic!mcsun!ukc!newcastle.ac.uk!lorien![e-mail]  (William Coyne)
Subject: Martian Canals - when did theory die?

A the start of this century an astronomer (Lowell I think) promoted
the theory of there being canals on Mars.  Was this accepted by many
other astronomers at that time?  When did this belief cease to be
head by any astonomers?

Replies can be sent by email to -

JANET: [e-mail]
UUCP : ...!ukc!newcastle.ac.uk!W.P.Coyne
ARPA : [e-mail]

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

Date: 29 Oct 90 05:07:51 GMT
From: agate!darkstar!helios![e-mail]  (Steve Allen)
Subject: Re: FITS images

In article <[e-mail]> [e-mail] (Ron Watkins) writes:
>NOAO has a publication that describes the FITS format rather nicely....
>The basics of the FITS format are:
            and he proceeds to give a basic description.

FITS is what FITS does, and the key problem here is that first F standing
for "flexible".

At Lick Obs., we have often had to rewrite our FITS reading software to
handle somebody else's idea of what a FITS image is.  Furthermore,
other people have had to rewrite their FITS readers to handle some of the
early FITS files generated here at Lick.  Our early implementation was
very wrong, and there are still a number of such broken images at places
which either observed here or used early versions of our Vista image
processing software.

To complicate the issue more, FITS really only applies to images stored
on magnetic tape.  The format used for storage of images on disk has
varied wildly over place and time.  Some sites always stored images on
disk in the natural data format of their computer, others have weird
embedded record information on disk.  Only recently, as heterogeneous
networks have become more common, have we at Lick cleaned up our act
so as to always store an image as a byte-for-byte replica of what is
kept on the tape.

Early FITS files were restricted to being integers only, but recent
extensions have allowed IEEE floating-point numbers also.  There are
images that have 3 or more dimensions.  There are also "FITS Tables",
which are files which contain tables of numbers.  Add to this that
following the image data described by the header there may be any other
data.

Steve Allen
[e-mail]

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

Date: Sun, 28 Oct 90 10:51:14 -0500
From: "Allen W. Sherzer" <[e-mail]>
Subject: Re: You Can't Expect a Space Station to be Cheap
Newsgroups: sci.space
Cc:

In article <[e-mail]>:
>aws>At $500 to $900 a pop those [shuttle] assembly costs add up fast.

>One pet peeve: could we have standard units of measurment here?
>I can't find the _pop_to_metric_ button on my calculator. (I know I
>should have bought an HP)

Sorry. POP is the Payload to Orbit Price. It is the price to LEO
of a microshuttle of material. A microshuttle is 1/1,000,000 of the
weight the Shuttle can lift (.04 pounds or .018 kilos) :-).

>With regard to two alternatives to HL Delta:

>1, Space Van, was to use the engines from the Delta and the RL-10.
>Both are _very_ proven technology.

But major modifications will be needed to the RL-10. As such it cannot
be treated as off the shelf. Problems are likely to arrise in the
RL-10 modifications. In the HLV alternatives, the only modifications
are to lumps of metal with no moving parts. This makes if far less
risky.

>2. SSX is meant to rely very much on proven technology. Also, maybe
>we should put some faith in _people_. The person who is behind SSX,
>Max Hunter, is the man who built Delta...

I think SSX is a great idea. SDIO is funcing development work on it
and I am confident that eventually we will see good things from it.
In the outyears if they get it I'm sure it will be used. However because
of problems outlined, it is too risky for this program.

  Allen
--
+-------------------------------------------------------------------------+
| Allen W. Sherzer      |         What should man do but dare?            |
|   [e-mail]         |             - Sir Gawain                        |
+-------------------------------------------------------------------------+

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

Date: Mon, 29 Oct 90 09:34:03 -0500
From: "Allen W. Sherzer" <[e-mail]>
Subject: Re: You Can't Expect a Space Station to be Cheap
Newsgroups: sci.space
Cc:

In article <[e-mail]> Henry writes:
+++ This HLV will cost less than ONE shuttle flight to  develop.
+++It will lift twice what the Shuttle lifts for a quater to half
+++the launch costs.
++
++Sounds good.   Good enough to get private venture
++capital.....right ? ...

>Wrong.  Where's the market?  There is only one customer:  the government.
>No venture capitalist in his right mind will fund this without clear
>signals from the government that they will buy a bunch.

One interesting idea Dr. Wood mentions may well do just that. In the last
third of the program they are talking about buying water delivered to orbit
on a first come first bought basis. They would anounce that they will pay
$750 a pound for the first X pounds delivered to the LEO Gas Station.

A similar effort (the Kelly Act) got the airline industry off the ground.
If this effort becomes big enough, it could create a space market as well.

  Allen
--
+-------------------------------------------------------------------------+
| Allen W. Sherzer      |         What should man do but dare?            |
|   [e-mail]         |             - Sir Gawain                        |
+-------------------------------------------------------------------------+

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

End of SPACE Digest V12 #508
*******************