Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V16_0/V16NO074.TXT

Internet Message Format | 1993-07-13 | 17KB

Date: Sun, 24 Jan 93 05:06:40
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V16 #074
To: Space Digest Readers
Precedence: bulk


Space Digest                Sun, 24 Jan 93       Volume 16 : Issue 074

Today's Topics:
                       *** BUSSARD RAMSCOOP ***
                    Galileo Laser Test Successful
                         Mir mission to Mars?
           ques about earlier "suicides" of SDI scientists
                             Solar sails
                 TAU Probe?(1000 Astronomical Units)

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Date: 23 Jan 93 06:52:45 GMT
From: Ron Baalke <[e-mail]>
Subject: *** BUSSARD RAMSCOOP ***
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Josh Hopkins) writes...
>[e-mail] (Lynne K Wahl) writes:
>
>>Hmmm... This sounds like an interstellar probe is needed to collect
>>information before a *really* fast spacecraft is launched.  How about
>>a .01c speed probe with a small "sail" that would be primarily used to
>>collect interstellar H (for testing) and with magnetic sensors to check
>>on the magnetic medium as it goes.  How far from the sun would this
>>"Pathfinder" type of probe need to go before getting outside the sun's
>>environment?

We have four spaceraft (Pioner 10 & 11 and Voyager 1 & 2) that have already
left the solar system and looking for the heliopause.  I'd say one of them
would reach the helipause within 10 years.

>>As an exercise, how fast would, say a refueled shuttle ET, one SSME,
>>and a 30 ton probe go if launched in a "generic" solar escape orbit?
>
>Really slowly.
>
>JPL proposed the TAU (Thousand AU) mission a number of years
>ago.  It would have used a nuclear reactor and an ion drive to boost out of
>the solar system in about fifty years and check out interstellar space.
>Unfortunately, since it required new power, engines and communications gear it
>never got very far.

The TAU mission would also use a light-wave communications system. It would
study low energy cosmic rays, low frequency radio waves, interstellar gases,
gravity waves and perform high precision astrometry.  The spacecraft would
also be targeted to flyby Pluto on its way out of the solar system.
     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | [e-mail]
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | Every once in a while,
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | try pushing your luck.
|_____|/  |_|/       |_____|/                     |

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

Date: 23 Jan 1993 06:33 UT
From: Ron Baalke <[e-mail]>
Subject: Galileo Laser Test Successful
Newsgroups: sci.space,sci.astro,alt.sci.planetary

From the "JPL Universe"
December 30, 1992

GOPEX reaches Galileo via laser beam
By Mark Whalen

     JPL researchers took advantage of Galileo's recent pass by
Earth to achieve a major milestone in space communications, by
successfully transmitting laser beams fired from the ground to
the spacecraft at distances of up to 6 million kilometers (3.7
million miles).
     "This experiment is part of a program to show that future
deep space missions can use laser beams to send back to Earth
larger volumes of space-acquired data than is currently possible
using radio signals," said Dr. James Lesh, supervisor of the
Optical Communications Group and principal investigator for the
Galileo Optical Experiment (GOPEX).
     The experiment's objectives, said Lesh, were to show that an
uplink beacon laser -- required as a reference for pointing a
return beam back to Earth -- could be successfully pointed to a
distant spacecraft based only on the navigational predicts of the
spacecraft trajectory. To do this, the distortions produced by
Earth's atmosphere had to be predicted and accommodated.
     The GOPEX demonstration began on Dec. 9 (one day after
Galileo made its closest Earth approach on its way to Jupiter) at
600,000 kilometers (370,000 miles), and continued through Dec.
16. Laser beams were simultaneously transmitted to the spacecraft
from a 61-centimeter (24-inch-diameter) telescope at the Table
Mountain Observatory near Wrightwood, Calif. and from a 1.5-meter
(60-inch) telescope at the U.S. Air Force Phillips Laboratory's
Starfire Optical Range near Albuquerque, N.M.
     The transmissions, which were detected by Galileo's onboard
camera, established a record for the farthest known transmission
and reception of a laser beam, a final distance of 6 million
kilometers.
     "GOPEX was extremely successful," said Lesh. "A real
pleasant surprise in the experiment was that we conducted the
experiment so repeatedly. Each day we made transmissions, we had
extremely reliable detections on the spacecraft camera.
     "We would predict ahead of time, `on this frame, we're going
to see a series of pulses about so high on the picture,' and as
soon as we got the image back, sure enough, there they were," he
said.
     Spacecraft signals produced by current radio-frequency
systems are used for three purposes, according to Lesh --
communications, navigation and science investigations. "There are
completely analogous applications in the laser area," he said.
     "We can communicate at substantially higher rates while
occupying much less room on the spacecraft," said Lesh. "The
antenna is the main feature on the spacecraft with radio
frequencies, often reaching diameters in excess of four meters.
At laser frequencies, 10-50 centimeter telescopes are quite
adequate.
     "We can also use optical beams for navigation," Lesh
continued. "When viewed from Earth, the light beam from a
spacecraft will look like a blinking star. We can view it in the
context of the stellar grid, or relative to target bodies we are
approaching. That information can be used to derive angular
coordinates of the spacecraft.
     "Laser signals also can be used to determine the
spacecraft's range, which, together with the angle information,
can be used to locate the spacecraft," said Lesh.
     As far as science investigations are concerned, Lesh claims
that scientists could use optical signals to probe phenomena such
as planetary atmospheres, to measure scattering from the
interplanetary dust particle distribution, or to make spatially
selective measurements of planetary ring systems using very short
wavelengths (below one micron).
     "Also," Lesh added, "optical signals are not corrupted by
solar wind fluctuations, like radio frequencies are. Some past
investigations of gravitational bending of radio waves have been
limited by charged particle fluctuations in the solar wind."
     Lesh also said laser communications technology will yield a
data rate increase "of about one-to-two orders of magnitude" over
radio frequencies.
     The idea of testing a laser uplink is not a new one. Lesh
said that the GOPEX demonstration was originally proposed in June
1984, but was rejected at the time because there were no plans
for Galileo to view Earth on its way to Jupiter.
     But the 1986 Space Shuttle Challenger accident prompted
changes in Galileo's launch system and necessitated a new flight
path, which included two gravity-assisted flybys of Earth. "At
the same time," he said, "Earth viewing became part of Galileo's
priorities, and the climate became much more receptive to our
doing the experiment, subject to us demonstrating beyond any
doubt that we would not damage any instrument on board the
spacecraft."
     In that regard, preperations were made to conduct GOPEX
during the Earth-1 encounter in December 1990. But inconclusive
data turned up on a test to determine if the experiment might
harm the Galileo orbiter's Near-Infrared Mapping Spectrometer, so
"about three days before the experiment, we were waved off," said
Lesh. In the intervening two years, testing of the effects of
laser signals on the NIMS and Solid State Imaging Camera
detectors concluded that "we were safe to substantially higher
levels than we would ever produce at the spacecraft," said Lesh.
     What's next for the program? Lesh said proposed plans call

for a flight experimental terminal to be flown aboard a space
shuttle in the latter half of the 1990s. "We are developing the
base technology for this now," he said, "and are trying to
augment the base program with some new flight experiment monies
that will allow us to do the (shuttle) demonstration."
     Operational use of this technology is anticipated some time
after the year 2000, Lesh added.
     "We expect that the first deep space mission to fly optical
will fly it as a mission enhancement experiment," said Lesh,
"although this could change with the new emphasis on low-cost
microspacecraft.
     "I believe that there are missions that can be best served
by laser frequencies, and there are those that are best served by
radio frequencies," he said. "Laser beams do require a certain
amount of pointing, for example. If you have large uncertainty
about the spacecraft pointing direction, it may be better to use
radio waves. However, most missions currently flying or on the
drawing boards provide adequate attitude control to use laser
communications.
     "Nevertheless," said Lesh, "I don't see us de-implementing
any capabilities in the future; I see us providing an additional
capability that will allow future missions to plan for and make
best use of the available technologies."
                               ###
     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | [e-mail]
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | Every once in a while,
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | try pushing your luck.
|_____|/  |_|/       |_____|/                     |

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

Date: Sat, 23 Jan 1993 09:11:02 GMT
From: Marcus Lindroos INF <[e-mail]>
Subject: Mir mission to Mars?
Newsgroups: sci.space

...perhaps the Russians should have tried to boost interest in their space
program in the West by launching a manned flyby mission to Mars?! A fully
fuelled Energia should be powerful enough to launch a Mir space station with
supplies for a crew of two plus a Proton rocket for course corrections. In
addition, a Soyuz capsule for return to Earth would be needed, and probably an
additional module for storing supplies and equipment.
---
The entire mission would last one year, with a close Martian flyby + course
correction some six months after launch. As I see it, we would obtain a lot of
valuable information from doing it. For example, how do humans cope with the
psychological strains of an interplanetary mission, being totally cut-off
from Earth for months? We would also learn a lot about guiding a manned
spacecraft millions of kilometers from Earth and similar things necessary for
launching a full-scale Mars mission.
---
I can't see any technical problems. The Energia is relatively untested but the
crew would rendezvous with the Mir/Energia combination in orbit and not be
aboard during the launch. The Suyuz
was designed for lunar missions and should be able to withstand the higher
temperatures of an atmospheric re-entry from interplanetary space. The weakest
link? Perhaps the Mir station itself. Its systems have been unreliable for most
of the missions in Earth orbit.

MARCU$

--------------------------------------------------------------------------
. . . Fififinlandssvensk

Marcus Lindroos                             Internet:     [e-mail]
Computer Science
Abo Akademi University
Finland

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

Date: Sat, 23 Jan 1993 23:10:38 GMT
From: Daniel Burstein <[e-mail]>
Subject: ques about earlier "suicides" of SDI scientists
Newsgroups: sci.physics,sci.misc,sci.space

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

>In article <[e-mail]>, [e-mail] (Daniel Burstein) writes...
>>down the results of any investigations.  The only stuff I've found has
>>been news articles simply describing the venets.["events", presumably]


>How about recalling where you saw the news articles, and when?
>Try real hard...

problem with the articles I've found is that they're only reporting the
deaths, or, at best, giving a "investgators are looking into it"

I haven't been able to find any coverage giving the results of the
enquiries.  The story just seemed to have died (no pun intended).

This is -kind of- reaching into ALT.CONSPIRACY stuff, but these deaths
certainly did occur, so I reached out to the SCI type nets because that's
where people who deal with scientists would hang out...

[e-mail]

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

Date: 23 Jan 93 08:39:41 GMT
From: Marcus Lindroos INF <[e-mail]>
Subject: Solar sails
Newsgroups: sci.space

In <[e-mail]> [e-mail] writes:

> [e-mail] (Tom) writes:
>
> >Josh Hopkins: >
>
> >Has anyone given any thought to sailing on something besides optical/IR
> >waves?  How about a giant radio antenna?  X-ray reflectors?
>
> The Starwisp uses microwaves if I recall correctly.  Make an impossibly huge
> mesh that's impossibly light and send impossible amounts of radio energy at it
> (say a good sized SPS worth) and you've got a starwisp.  I think Bob Forward's
> proposal used 10 GW to boost at 115 gravities for a few days.  It would then
> coast at .2 C for twenty years before zipping through Alpha Centauri.

There was another proposal as well. A small space probe suspended behind a
giant solar sail (2km across, total mass of one hundred kg(?)) would reach
Alpha Centauri in 250 years if we make a close flyby of the Sun - one solar
radius from the surface (0.7 million km). Is there a way to manufacture an
ultra-light sail able to withstand the temperature (4000-5000K at least)?
---
The we come up with the materials and nanotechnology to do it, it might be an
attractive alternative. 3-10 centuries is a long time, but the probe could
double as a deep space survey probe while moving outwards and building a
craft having a lifetime of a couple of hundred years will be possible in a
near future.

> --
> Josh Hopkins                                          [e-mail]
>
> Q:  How do you tell a novice from an expert.
> A:  A novice hesitates before doing something stupid.


MARCU$

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

Date: Sat, 23 Jan 1993 08:26:09 GMT
From: Marcus Lindroos INF <[e-mail]>
Subject: TAU Probe?(1000 Astronomical Units)
Newsgroups: sci.space

I recently saw a couple of pictures of the proposed Thousand Astronomical Units
probe in a book by Nicholas Booth. The craft itself looks like an enlargened
Cassini/Mariner mk.II, with a huge antenna dish [diameter of approx. 15
meters], an optical laser system for communications, an 1.5-meter telescope
for carrying out measurements of radial velocities for nearby stars(?) and the
customary particle and fields experiments equipment.
---
The second part, the ion engine, wasn't really dealt with in the text so I'd
appreaciate it someone could fill in the details. It's basically a long
cylinder with a small nuclear reactor in the rear end powering the engine. The
ion drive will accelerate the propellant [metals like Mercury or Cesium?] to
velocities of up to 70km/s and will fire continuously for ten years. After
that, the two parts would separate and the engine section would act as a relay
station between the probe itself and Earth. The spacecraft will reach  a
velocity of 100 km/s and a distance of 1000 AU (0.002 light-years)
in only fifty years. In addition, a Pluto orbiter could be released as the
probe leaves the solar system.
---
How would the probe be launched? It appears to be far too big and heavy to fit
inside a standard rocket booster. Will they use the shuttle for this, and will
the ion engine be used for accelerating the probe out of Earth orbit as well?
---
Jet Propulsion Laboratory came up with the mission plan. Perhaps Ron Baalke can
shed some light on this?

MARCU$

--------------------------------------------------------------------------
. . . Fififinlandssvensk

Marcus Lindroos                             Internet:     [e-mail]
Computer Science
Abo Akademi University
Finland

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

End of Space Digest Volume 16 : Issue 074
------------------------------