Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT_ZIP/spacedig/V15_4/V15NO475.ZIP/V15NO475

Internet Message Format | 1993-07-13 | 27KB

Date: Tue,  1 Dec 92 05:00:06
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #475
To: Space Digest Readers
Precedence: bulk


Space Digest                Tue,  1 Dec 92       Volume 15 : Issue 475

Today's Topics:
                       air pressure at altitude
                           Hubble's mirror
                             Karl Guthre?
                       Nuclear Rocket Software
                         Shuttle replacement
                        Space Digest V15 #452
                           SSTO Information
           Terminal Velocity of DCX? (was Re: Shuttle ...)

    Welcome to the Space Digest!!  Please send your messages to
    "[e-mail]", and (un)subscription requests of the form
    "Subscribe Space <your name>" to one of these addresses: listserv@uga
    (BITNET), rice::boyle (SPAN/NSInet), utadnx::utspan::rice::boyle
    (THENET), or [e-mail] (Internet).
----------------------------------------------------------------------

Date: Thu, 26 Nov 92 21:00 GMT
From: Daniel Burstein <[e-mail]>
Subject: air pressure at altitude

Good day:

  There's been a bit of discussion about partial
pressures of air and oxygen at different altitude
equivalents.  Refernces have been made to Denver,
to Mexico City, Aspen, and some others.

   Just to make things nice and clear, attached
is a chart showing pressure at different altitudes.
Information is based on chart # F-151 in the
Chemical Rubber Company Handbook of Chemistry
and Physics, 65th edition (1984-1985).  I've
converted height in meters to feet, and the
Bar pressure to inches of mercury.

   Also, for good measure, I've calculated pressure
percentage  at altitude, with sea level
being 100%.

   Because of the numerous conversions, discrepencies
between tables, and rounding errors, please consider
these values as approximations.

   Quick relevant note:  Since oxygen is roughly
20 percent of air, the partial pressure of oxygen
in sea level O2 is about 3%.  This corresponds to
breathing pure O2 at an altitude of about 11,700
meters (38,000 feet).  Which confirms that the
pilots and other safety personnel in an HST would
have to be in pressurized suits, rather than being
able to rely on facemasks alone.

  -Danny Burstein  <[e-mail]>


height    height   mercury  mercury   press.   pressure
meters     feet     bars     inches   in psi   %sea lvl

  (1,000)  (3,300)    1.14    33.64    16.75   112.47
    (500)  (1,650)    1.07    31.74    15.80   106.09
       0        0     1.01    29.91    14.89   100.00
     500    1,650     0.95    28.19    14.03    94.24
   1,000    3,300     0.90    26.54    13.21    88.72
   1,500    4,950     0.85    24.97    12.43    83.47
   2,000    6,600     0.80    23.48    11.69    78.48
   2,500    8,250     0.75    22.06    10.98    73.73
   3,000    9,900     0.70    20.71    10.31    69.22
   3,500   11,550     0.66    19.42     9.67    64.94
   4,000   13,200     0.62    18.21     9.06    60.87
   4,500   14,850     0.58    17.05     8.49    57.01
   5,000   16,500     0.54    15.96     7.95    53.35
   5,500   18,150     0.51    14.92     7.43    49.89
   6,000   19,800     0.47    13.94     6.94    46.61
   6,500   21,450     0.44    13.02     6.48    43.51
   7,000   23,100     0.41    12.14     6.04    40.58
   7,500   24,750     0.38    11.31     5.63    37.81
   8,000   26,400     0.36    10.53     5.24    35.19
   8,500   28,050     0.33     9.79     4.87    32.73
   9,000   29,700     0.31     9.10     4.53    30.40
   9,500   31,350     0.29     8.44     4.20    28.22
  10,000   33,000     0.26     7.83     3.90    26.16
  10,500   34,650     0.25     7.25     3.61    24.23
  11,000   36,300     0.23     6.70     3.34    22.41
  11,500   37,950     0.21     6.20     3.08    20.71
  12,000   39,600     0.19     5.73     2.85    19.15
  12,500   41,250     0.18     5.30     2.64    17.70
  13,000   42,900     0.17     4.90     2.44    16.37
  13,500   44,550     0.15     4.53     2.25    15.13
  14,000   46,200     0.14     4.18     2.08    13.99
  14,500   47,850     0.13     3.87     1.93    12.93
  15,000   49,500     0.12     3.58     1.78    11.96
  16,000   52,800     0.10     3.06     1.52    10.22
  17,000   56,100     0.09     2.61     1.30     8.74
  18,000   59,400     0.08     2.23     1.11     7.47
  19,000   62,700     0.06     1.91     0.95     6.38
  20,000   66,000     0.06     1.63     0.81     5.46
  25,000   82,500     0.03     0.75     0.37     2.51

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

Date: Mon, 30 Nov 1992 14:57:00 GMT
From: "Robert S. Hill" <[e-mail]>
Subject: Hubble's mirror
Newsgroups: sci.astro,sci.space

In article <[e-mail]>, [e-mail] (Henry Spencer) writes...
>In article <[e-mail]> [e-mail] (David M. Palmer) writes:
>>How do you do an end-to-end imaging test?  The depth of field of
>>an instrument with Hubble's aperture is such that a point source
>>must be thousands of kilometers away in order to be in focus.
>
>I'm not an optics guru... but the test was considered feasible, if costly
>and somewhat risky.  My guess would be a bit of optics to move a real
>source out to a virtual infinity, as is done in head-up displays.

It's not that hard to set up a collimator:  it's just a big parabolic
the size of the telescope aperture, with a very small source of the
appropriate wavelength positioned at the focus.  This is good enough
for shimming the overall focus of a small instrument.  I don't work on
HST, I don't know what they would have done for it.


Robert S. Hill
[e-mail]

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

Date: 30 Nov 92 09:40:30 GMT
From: Amanda Baker <[e-mail]>
Subject: Karl Guthre?
Newsgroups: sci.astro,sci.space

Greetings,


        I am looking for published papers (in English, in major
journals) by someone who I believe is involved in the current NASA SETI
project, whose name is Karl Guthre, or something similar. I have tried
looking in Abstracts, but I think I must have the spelling, if not the
phonetics, of the surname wrong, as I haven't turned anything up.

    Please reply to me by email, as it is somewhat urgent, and I
will summarise to the net.

    Many thanks

    Amanda Baker



--
Amanda Baker
Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA UK
Tel: [phone] x 37505  E-mail: [e-mail]
Fax: [phone]            or    [e-mail]

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

Date: Mon, 30 Nov 92 09:00:42 PST
From: "UTADNX::UTDSSA::GREER"@utspan.span.nasa.gov
Subject: Nuclear Rocket Software

I just got my Winter editition of COSMIC, a quarterly publication of NASA's
COmputer Software Management and Information Center.  In it, two programs on
nuclear rockets are offered.

CAC - For predicting temperatures and pressures in a nuclear rocket engines.
      "One of the most important factors in the development of
       nulcear rocket engine designs is to be able to accurately
       predict temperatures and pressures throughout a fission
       nuclear reactor core with axial hydrogen flow through
       circular coolant passages."
      Developed originally in 1966; 1992 version written in FORTRAN 77.
      Price: Program $450 Documentation $36

NOP - Nuclear rocket engine optimization program.
      "NOP is a versatile digital computer program developed for
       the parametric analysis of beryllium-reflected, graphite-
       moderated rocket engines."
      Written in FORTRAN 77.
      Price: Program $750 Documentation $82

_____________
Dale M. Greer, whose opinions are not to be confused with those of the
Center for Space Sciences, U.T. at Dallas, UTSPAN::UTADNX::UTDSSA::GREER
"Pave Paradise, put up a parking lot." -- Joni Mitchell

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

Date: 30 Nov 92 13:48:03 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: Shuttle replacement
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Josh 'K' Hopkins) writes:

  >    Oh, PLEASE! Do you HONESTLY believe a crew would have survived the
  >    April, 1986 Titan 34-D launch failure?

>>Yes I think they would have had a 50/50 chance.

>I have trouble believing someone can make the very significant decision of
>seperating the hypothetical capsule (and thus canceling the mission) with 1/5
>of a second reaction time.

It has been done. Aside from the Gemini mission you mention below I'm sure
a brief survey of pilot ejections would find more.

>I recall at least one case (Apollo? Gemini?) where
>one of the astronauts was faced with data suggesting this decision might be
>required - it's not an easy one.

I believe it was Guss Grissom. The engines on their Titan launcher ignighted
and then shut down after the control panel indicated liftoff had occured. If
the panel was correct and they didn't punch out, they would be dead 1/10 of
a second later. Grissom however felt that "it felt solid beneath" and
made the correct decision not to eject.

>However, I do not debate that rockets with
>capsules are generally safer than side mounted configurations.

Which is the only claim being made. As has been pointed out, everybody
dies when the worse case happens.

  Allen

--
+---------------------------------------------------------------------------+
| Allen W. Sherzer | "A great man is one who does nothing but leaves        |
|  [e-mail]     |  nothing undone"                                       |
+----------------------145 DAYS TO FIRST FLIGHT OF DCX----------------------+

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

Date: Sat, 28 Nov 92 00:42:13 EST
From: "Zalbar Delphi, MAIL::GOD" <[e-mail]>
Subject: Space Digest V15 #452

>
>I would imagine that these are accessible by telnet, but I have
>not used all of them.  I hope this helps someone!
>
    Also, if you are using a vax system, you can try to
    Rlogin to the site...

    $ rlogin/user='username' somesite.someaddress.somewhere

Chris Sheldon
[e-mail]
[e-mail]

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

Date: 30 Nov 92 16:05:10 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: SSTO Information
Newsgroups: sci.space

The following is a position paper on SSTO for the Freshmen Orientation
project. Hope it is of interest...

  Allen
-------------------------------------------------------------




                            SSTO
               A Spaceship for the Rest of US

Introduction
Space is an important and growing segment of the U.S.
economy.  The U.S.   space market is currently over $5
billion per year, and growing.  U.S. satellites, and to a
lesser degree U.S. launch services, are used throughout the
world and are one of the bright stars in the U.S. balance of
trade.

The future is even brighter.  The space environment promises
new developments in materials, drugs, energy, and resources,
which will open up whole new industries for the United
States.  This will translate into new jobs and higher
standards of living not only for Americans but for the rest
of the world's people.

Standing between us  and these new industries is the
obstacle presented by the high cost of putting people and
payloads into space.  This paper addresses the reasons why
access to space is so expensive and how those costs might be
reduced by looking at the problem in a different way.

Finally, this paper will describe a radical new spacecraft
currently under development.  Called Single Stage to Orbit
(SSTO), it promises to greatly reduce costs and increase
flexibility.

Access to Space: Expensive and Dangerous
Access to space today is very expensive, complex, and
dangerous  With U.S.  expendable launchers like Atlas,
Delta, and Titan, it generally costs about $3,000  to $8,000
to put a pound of payload into low Earth orbit (LEO).  In
addition, U.S.  expendables require extensive ground
infrastructure to do final assembly and payload integration
and complex launch facilities to actually launch the rocket.
Finally, despite all the extra care and effort, they don't
work very well and even the best launchers fail about 3% of
the time (would you go to work tomorrow if there was a 3%
chance of your car exploding?).

Even the U.S. Space Shuttle, which was supposed to give the
U.S. routine low cost access to space, has failed.  A
Shuttle flight costs about $500 million (roughly $10,000 per
pound to LEO).  Even going full out, NASA can only launch
each  Shuttle about twice a year (for a total of eight
flights).

The effects of these high costs go deeper than the price tag
for the launches themselves.  Space equipment is much more
expensive than comparable equipment meant for use on Earth,
even when tasks are similar and the Earthly environments are
harsh.  The difference is that space equipment must be as
lightweight as humanly possible and must be as close as
humanly possible to 100% reliability.  Both of these extra
requirements are ultimately problems of access to space: if
every extra pound costs thousands of dollars, and replacing
or repairing a failed satellite is impossibly expensive,
then efforts to reduce weight and improve reliability make
sense.  Unfortunately, they also greatly increase price.

With equipment so expensive, obviously building extra copies
is costly, and launching them is even worse.  This
encourages space projects to try to get by with as few
satellites as possible.  Alas, this can backfire: when
something does go wrong, there isn't any safety margin...as
witness the U.S.'s shortage of weather satellites at this
time.  Expensive access to space not only produces costly
projects, it produces fragile projects that assume no
failures, because safety margins are too expensive.
Lamentably, failures do happen.

Finally, although research in space holds great promise for
new scientific discoveries and new industries, it is
progressing at a snail's pace, and companies and researchers
often lose interest early.  Why?  Because effective research
requires better access to space.  Scientific discoveries
seldom come as the result of single experiments: even when a
single experiment is crucial, typically there is a long
series of experiments leading up to it and following through
on it.  And getting the "bugs" out of a new industrial
process almost always requires a lot of testing.  But how
can such work be done if you only get to fly one experiment
every five years?  Good researchers and innovative companies
often decide that it's better to avoid space research,
because it costs too much and takes too long.   The ones who
haven't abandoned space research are looking hard at buying
flights on Russian or Chinese spacecraft: despite technical
and political obstacles, they can fly their experiments more
often that way.

People excuse this because it has always been this way and
so probably always will be (after all, this is rocket
science).  But there are a lot of reasons to think that it
needn't be so complex and expensive.

Spacecraft are complex, expensive, and built to aerospace
tolerances but they are not the only products of that nature
we use.  A typical airliner costs about the same as a
typical launcher.  It has a similar number of parts and is
built to similar tolerances.  The amount of fuel a launcher
burns to reach orbit is about the same as an airliner burns
to go from North America to Ausralia.  Looked at this way,
it would seem that the cost of getting into orbit should be
much closer to the $1500 it takes to get to Australia than
to the $500 million dollars plus it takes to put an
astronaut up.

Why the differences in cost?  Largely they are due to
different solutions to the same problems.  Some of these
differences are:

1.  Throw away hardware.  A typical expendable launch
vehicle costs anywhere from $50 to $200 million to build
(about the cost of a typical airliner) yet it is used  one
time and then thrown away.  Even the 'reusable' Space
Shuttle throws away most of its weight in the form of an
expendable external tank and salvageable solid rocket
motors.  This is the single biggest factor in making access
to space   expensive.

Airlines use reusable hardware and fly their aircraft
several times every day.  This allows them to amortize the
cost of the aircraft over literally thousands of passenger
flights.  The entire Shuttle fleet flies only eight times a
year, while many airliners fly more than eight times per
day.

2.  Redundant Hardware and Checks.  Since expendable
launchers are used one time and then thrown away, they
cannot be test-flown; huge amounts of effort therefore go
into making sure they will work correctly.  Since the
payloads they launch are typically far more expensive than
the launcher (a typical communication satellite can cost
three times the cost of the launcher) millions can be and
are spent on every launch to obtain very small increases in
reliability.  This is well beyond the point of diminishing
returns and sometimes results in greater harm.  For example,
a couple of years ago a Shuttle Orbiter was almost damaged
when it was rotated from horizontal to vertical with a loose
work-platform support still in its engine compartment.  The
support should have been removed beforehand...and three
signatures said it had been.

Airliners, since they are reusable and can also be tested
before use, thus are able to be built to more relaxed
standards without sacrificing safety.  The exact same
aircraft flew to get to your airport and it is likely that
any failure would already have been noticed.  In addition,
aircraft are built with redundancy so they can survive
malfunctions; launchers usually are not.  Most in-flight
failures of airliners result, at most, in delays and
inconvenience for the passengers; most in-flight failures of
launchers result in complete loss of launcher and payload.

3.  Pushing the Envelope on Hardware.  Current launchers
tend to use hardware that is run all the time at the outside
limit of its capability.  This may be fine for expendable
launchers which are used one time and don't need to be
repaired for reuse.  But this has also tended to carry over
to the Shuttle which, for example, operates its main engines
at around 100% of its rated thrust (this is like driving
your car 55 MPH in first gear all the time).  Because the
hardware is used to its limit every time, it needs extensive
checkout after every flight and frequent repair.

Airliners tend to be much more conservative in their use of
hardware.  Engines are used at far less than their full
rated thrust and airframes are stressed for greater loads
then they ever see.  This results in less wear and tear
which means they work with greater reliability and fewer
repairs.

4.  Labor Requirements.  For all of the reasons given above,
existing launchers require vast amounts of human labor to
fly.  The efforts of about 6,000 people are needed to keep
the Shuttle flying.  This represents a huge expense and is
amortized only over eight or so Shuttle flights every year.

Airliners are far more streamlined and, for the reasons
given above, don't need nearly as many people.  A typical
airliner only has 150 people supporting it, including
baggage handlers, flight crews, ticketing people, and
administration.  Since the cost of those 150 people are
amortized over thousands of flights per year, the cost per
flight is very low.

Our current  launchers are expensive and complex vehicles.
Yet the fact that we routinely use vehicles with similar
cost and complexity for far less cost indicate that the
causes of high launch costs lie elsewhere.  If we looked at
the problem in a different way, we could try to build
launchers the same way Boeing builds airliners.  The next
section will describe just such a launcher and how it is
being built.

A Spaceship that Runs Like an Airliner: SSTO
For a long time, some launcher designers have realized that
designing launchers the way airliners are designed would
result in lower costs.  Several designs have been proposed
over the years and they are generally referred to as Single
Stage to Orbit (SSTO) launchers.

1.  Single Stage to Orbit (SSTO).  Unlike an existing
launcher which has multiple stages, a SSTO launcher has only
one stage.  This results in far lower operational costs and
are key to reusability.  Conventional launchers need
expensive assembly buildings to stack the stages together
before going to the launch pad.  An SSTO only has one stage,
so these facilities are not needed.  This means that the
only infrastructure needed to launch a SSTO is a concrete
pad and a fuel truck.

2.  Built for Ease of Use.  SSTO vehicles are built to be
operated like airliners.  They can fly multiple times with
no other maintenance needed other than refueling.  If a
problem is discovered, all components can be accessed with
ease (by design).  The defective Line Replaceable Unit (LRU)
is replaced and launch can occur with only a short delay.
If the problem is more complex or other maintenance is
needed, the SSTO is towed to a hanger where the easy
accessibility of parts insures rapid turnaround.

3.  Standard Payload Interface.  Payloads need access to
services like power, cooling, life support, etc., while
waiting for launch.  The interfaces which provide these
services are not standardized, adding cost and complexity to
existing launchers.  In effect, part of the launcher must be
redesigned for each and every launch.  SSTOs, however, would
be designed with standard payload interfaces.  This allows
payload integration to occur hours before launch instead of
weeks before launch.  (Although in all fairness, the makers
of expendable launchers are also slowly moving in this
direction).

4.  Built to be tested.  Unlike expendables, SSTO vehicles
do not have to be perfect the first time.  Like airliners,
they can survive most failures.  Like airliners, they can be
tested again and again to find and fix problems before real
payloads and passengers are entrusted to them.  Even when a
failure does occur with a real payload aboard, usually
neither the vehicle nor the payload will be lost.  The
reliability of SSTO vehicles should be close to that of
airliners -- a loss rate of essentially zero -- and far
better than the 3% loss rate of existing launchers.


SDIO Single Stage Rocket Technology Program
Recent advances in engine technology and materials have made
most critics believe that the technology is now available to
build a SSTO.  In 1989, SDIO recognized the potential of
this approach and commissioned a study to assess its risk.
The study concluded that a SSTO vehicle is possible today.
As a result of this study, SDIO initiated the Single Stage
Rocket Technology Program  (SSRT).  The goal of the three
phase SSRT program is to build a SSTO, thus providing
routine cheap access to space.

Phase I consisted of four study contracts to develop a
baseline design for a SSTO.  General Dynamics and McDonnell
Douglas proposed vehicles which both take off and land
vertically (like a helicopter).  Rockwell proposed a vehicle
which takes off vertically but lands horizontally (like the
Space Shuttle does today).  Finally, Boeing proposed a
vehicle which both takes off and lands horizontally (like a
conventional aircraft).

In August 1991, SDIO selected the McDonnell Douglas vehicle
(dubbed Delta Clipper) for Phase II development, and
contracted for the construction of a 1/3 scale prototype
vehicle called DC-X.  This prototype is currently under
development and should begin flying in April, 1993.

DC-X will provide little science data but a wealth of
engineering data.  It will validate the basic concepts of
SSTO vehicles and demonstrate the ground and maintenance
procedures critical to any successful orbital vehicle.

Phase III of the program will develop a full scale prototype
vehicle called DC-Y.  DC-Y will reach orbit with a
substantial payload, hoped to be close to 20,000 lbs,  and
demonstrate total reusability.  In addition, McDonnell
Douglas will begin working with the government to develop
procedures to certify Delta Clipper like an airliner so it
can be operated in a similar manner.

Phase III was scheduled to begin in September of 1993 but
SDIO will not be able to fund the Phase III vehicle.  There
is some interest in parts of the Air Force and it is hoped
that they will fund DC-Y development.  It will be a great
loss for America if they do not.

After Phase III, it will be time to develop an operational
Delta Clipper launcher based on the DC-Y.  At this point
government funding shouldn't be needed any longer and the
free market can be expected to fund final development.

Conclusion
If a functional Delta Clipper is ever produced it will have
a profound impact on all activities conducted in space.  It
will render all other launch vehicles in the world obsolete
and regain for the United States 100% of the western launch
market (half of which has been lost to competition from
Europe and China).  It will allow the United States to open
up a new era for mankind, and regain our once commanding
lead in space technology.

--
+---------------------------------------------------------------------------+
| Allen W. Sherzer | "A great man is one who does nothing but leaves        |
|  [e-mail]     |  nothing undone"                                       |
+----------------------145 DAYS TO FIRST FLIGHT OF DCX----------------------+

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

Date: 30 Nov 92 13:55:05 GMT
From: Thomas Clarke <[e-mail]>
Subject: Terminal Velocity of DCX? (was Re: Shuttle ...)
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Brian Stuart Thorn)
writes:
> However, if DCX *loses* power on it's way in, then it becomes a falling
> rock, with *no* control. The pilot or computer would be unable to veer
> away from said apartment complex. Look out below.
>
Does anyone know what the terminal velocity of the empty DCX is
supposed to be?  I heard a figure of 80,000 pounds empty.  If it
were 20 meters in diameter its weight/area would be about that of
a human with a terminal velocity circa 100 mph.  It seems that
with all that tankage to crush that you could walk away from a DCX
crash provided it were made by Volvo :-)  Decelerate from
100 mph (50 m/sec) in 30 meters distance would give about 4 g.

--
Thomas Clarke
Institute for Simulation and Training, University of Central FL
12424 Research Parkway, Suite 300, Orlando, FL 32826
[phone], FAX: [phone], [e-mail]

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

End of Space Digest Volume 15 : Issue 475
------------------------------