Space & Astronomy/Space and Astronomy (October 1993).iso/pc/text/spacedig/v10_3/v10_334.txt

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Subject: SPACE Digest V10 #334

SPACE Digest                                     Volume 10 : Issue 334

Today's Topics:
               Re: Mars rovers
        Re: Galileo Astronauts Honored at JPL
           Frequently asked SPACE questions
----------------------------------------------------------------------

Date: 10 Dec 89 23:04:43 GMT
From: daisy.learning.cs.cmu.edu![e-mail]  (Marc Ringuette)
Subject: Re: Mars rovers

The recent discussion of teleoperated Mars Rovers has been mostly on target.
Time delays are a big problem, especially since the rover wouldn't have access
to the Deep Space Network for anywhere near 100% of the time.  Other big
constraints are that Mars is very rough, and that the power budget for the
rover will be distressingly low (e.g. 300 watts for a 1-ton rover).

There's a research project here at Carnegie-Mellon which is trying to tackle
these problems, by constructing a prototype of a six-legged walking Mars
Rover which can move over rough terrain autonomously.  The machine will walk
at a speed of about 1 meter per minute, using a laser rangefinder to find
obstacles and footfall locations.  The first leg has been built and tested,
and a version the rangefinding software has been used to plant the foot in a
simulated terrain.  Within the next year, the entire walking prototype will
be finished and tested.  The research is supported by NASA.

I'll attach a more detailed summary of the Mars Rover project, which I wrote
up about a year ago.  Beware: it's out of date, and several major design
changes have happened since then.


There probably won't be a problem with dangers requiring a fast reaction
time; Mars is a pretty static place, as far as we can tell.  In the current
scenarios, if the rover gets caught in a landslide it dies, and that's just
the way it goes.


A final note:  remember, just because YOU can't think of a way to make a
vehicle motor around safely on Mars, doesn't mean it can't be done.  Given
a decent research team and a few years, people can do some really good stuff.


\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
 \\\ Marc Ringuette \\\ Carnegie Mellon University, Comp. Sci. Dept. \\\
  \\\ [e-mail] \\\ Pittsburgh, PA 15213.  Phone [phone](w) \\\
   \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\


Subject: space-tech excerpt: CMU Mars Rover [ 200 lines ]

The CMU Mars Rover Project
==========================

The next step in Mars exploration is to send a flexible, mobile robot to Mars
to collect and study samples from different areas.  The importance of the
mission is split between observation, on-site testing of samples, and return
of samples to Earth.  The requirements for this vehicle are pretty stiff if
we are to try one of the more ambitious and more useful of the possible
missions.  The trickiest part of the problem is to do autonomous motion and
sampling.  Light takes between 10 and 40 minutes to travel the round trip
between Earth and Mars, so a vehicle operated from Earth would be extremely
slow.  Even worse, NASA's Deep Space Network has other jobs to do, and the
rover will spend half its time on the far side of Mars.  This virtually
requires a vehicle which can move and take samples using on-board computers
and Artificial Intelligence techniques, with human intervention only once
every few hours.  The mechanical design of the vehicle is also difficult.
The design is most highly constrained by a very low power budget - a few
hundred watts to run a 1-ton vehicle.

The CMU rover project is a 3-year project to build a rover which will operate
on Earth terrains, and be the prototype for a rover which can
 1. travel several hundred kilometers, reliably, over the period of about
    a year, traversing 1 meter obstacles and ravines
 2. take core samples, aim instruments, and perform sampling and experiments
    as flexibly as possible
 3. collect about 5 kilograms of samples and transport them to a return
    vehicle for return to Earth
 4. weigh no more than about a ton
 5. operate on about 300 watts of continuous power, supplied by a Radioisotope
    Thermal Generator (RTG)
 6. operate efficiently even when not in communication with Earth

The project has three main research areas: Mechanical Design, Sensing, and
Control.  The first group is building the vehicle, and is headed by Red
Whittaker, a mechanical engineer who recently constructed a robotic vehicle
to clean up Three Mile Island.  The second group, sensing, is headed by Takeo
Kanade, a Computer Science professor who has been involved with the NAVLAB
autonomous truck.  They are using a laser rangefinder and computer vision
software to maintain a terrain map on board the rover.  The third group is
headed by Tom Mitchell and Reid Simmons, who do Artificial Intelligence work.
Their group is designing the software to do motion and sampling without human
intervention.


The Ambler
==========

The original proposal from the CMU group had been for a rover with large,
soft wheels which could ignore small obstacles.  However, the mechanical
design group determined that a walking rover could better satisfy the
reliability, stability, and power requirements of the mission.  A few hundred
watts is almost no power at all, so a wheeled vehicle loses because it puts
so much power into its ground interactions.  A legged vehicle is mechanically
more challenging, but is smoother in operation and very energy efficient.

The Ambler has six legs, each of which has two joints which move in the
horizontal plane and a telescoping z-axis which stays vertical.  The
horizontal and vertical directions are totally decoupled - the machine
always stays level, and the two horizontal joints also stay level at all
times.  Each of the six legs is attached to a central pole at a different
height, so they can move 360 degrees without running into each other.
The bulk of the body hangs from the center pole, close to the ground.

Here is a picture:  [[ Note: the design has changed; this is out of date ]]

                              | |---------------------------------
                              | |                |              | |
                              | |---------------------------------
 -----------------------------| |^               ^               U
| |          |                | |Shoulder        Elbow           U
 -----------------------------| |                                U
 U                            | |                                U
 U                --------------------------                     U
 U               |                          |                    U
 U               | Body (with RTG, sampling,|                    U
 U               | computing, robot arm,    |                    U
 U               | instruments)             |                    U
 U               |                          |                    U
 |               |                          |                    |
 |               |                          |                    |
 |               |                          |                    |
 |                --------------------------                     |
 |                                                               |
 |                                                               |
/_\                                /_\

        (Side view of the body and the lower two of six legs)
        (the elbow and shoulder move in and out of the page)


=============================================================================

                                     _________
                     _              /---------
                 __--_\\_    ------//
             __--__--  \_\_/      //\   __-
           --__--        \_\_    //  __----\
           --            | \_\ -//__----   \\
                     ______--_|  |--- |     \\
                  _-- ____---  -- _-___      \\
                 / ---    \        --__-__
                / /        \        /  --||
               / /           ------       ||
              / /                         ||
             / /                           ||
                                           ||



            (Top view.  5 legs planted, 1 recovering.)
(The leg segments shown here are horizontal; the z-axis goes into the page)

=============================================================================


The machine has a reach of about 4 meters and a height of about 4 meters.
The laser rangefinder goes on top of the central pole.

The Ambler will walk a bit like a crab, with five legs on the ground at
all times.  When a leg is lifted from behind the vehicle, it is moved
all the way to the front of the vehicle to minimize the number of footfalls
required.  The body slides forward using the horizontal joints only, spending
energy only on friction losses and ground sinkage.  It moves almost like
floating on water.  The z-axis is used to hoist the body up and down, and
to lift each foot for recovery to the next position.

The machine moves very slowly (since the limiting factor is the ability
to control the motion reliably, not the motion itself).  The body averages
a few centimeters per second, which is plenty as long as the machine can
operate autonomously.


The Software
============

Building the Ambler is about half the project.  The other half is putting
together a software system to reliably (VERY reliably) move the robot from
place to place and perform sampling tasks.

A terrain map (more or less a contour map of the immediate vicinity of
the rover) is maintained by integrating data from the rangefinder.  Other
information, such as "this is a rock" or "this is black stuff that sticks
to your feet" may be attached to the basic map.  This allows motion planning
to be done accurately.

The rover will be controlled by commands from the control center on Earth,
such as

   "go north as long as it's safe"
   "go back and pick up rock 13 and look at its underside"
   "follow this path to rock 15 and drill a hole in it, at this angle"
   "pick up one of those gray pebbles, about half an inch wide"
   "put this dust in your mass spectrometer"
   "aim your infrared sensor at anything unusual"

The commands won't be in English, but rather will be specified in terms
of frames and slots in a knowledge representation system designed by the
control group.

Realistically, there will probably be a team of geologists fighting over
what is most important to do next.  Rather than forcing them to do the
optimization of exactly what to do, it will be necessary to have a planning
system which can do the best thing given a set of goals of varying importance
and difficulty.  For instance, if one goal is very easy, you might as well
do it first rather than a more desirable but much more difficult goal.  There
are also background goals best monitored by the machine, such as "Never go
too near a dropoff" and "Don't point your satellite dish away from Earth."

A flexible geometric reasoning system will be a component of the software.
It's important for the rover to have the ability to pick up a rock, and
also to be able to notice if the rock was dropped by accident.  This
involves creating a general purpose planner which can generate expectations
about what will be true in the world if all went as planned, and to check
if this really happened.

=============

As of now, January '89, the project has finished its first year.  A
single-leg testbed is being used to test the leg design and the footfall
planning software.

The project is funded by NASA, and there is interaction with groups from
JPL, TRW, and Martin Marietta.  JPL in particular has a parallel project,
designing a more conventional wheeled rover for the same mission.  Ours is
considered to be the more ambitious and high-risk of the two attempts.  The
results will be evaluated before the possible production of a Mars-ready
rover to be launched in approximately 1998.

[ end of excerpt ]

[ To join the space-tech list, send mail to [e-mail] ]

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

Date: 8 Dec 89 21:17:58 GMT
From: timbuk![e-mail]  (Lou Adornato)
Subject: Re: Galileo Astronauts Honored at JPL

In article <[e-mail]> [e-mail] (Stephen R Fleming) writes:
>>Time was then set aside for the
>>JPL employees to chat with the astronauts and to get their autographs.
>
>...Just think about this sentence for a second...
>
>I'm not a basher of the individual astronauts; I'd love to be one.
>But the thought of people at JPL, the *real* space-science heroes
>of the last couple of decades, clustering around a bunch of
>Right-Stuffers like teenage groupies...
>

How do you define hero?  I consider a hero to be someone who is willing to make
the ultimate sacrifice for something he/she sees as bigger than him/herself.
Doing your job well isn't grounds for hero worship, it's grounds for a pay
raise.  The folks at JPL do a fantastic job, and are entitled to respect and
admiration (and _really_ nice pay raises), but their pesonal risk is limited
to VDT syndrome, or keyboard wrist.  Have we become so mired in the workaday
world that we truly feel that exceeding your job description and risking your
life are the same thing?

My father was one of the more than 300,000 people to work on the Apollo
program; he helped design and build the mobile launch pads for Apollo
(and now the shuttle).  I'm proud as hell of that, but I don't consider
him a hero for it.

I remember when the Apollo 1 fire happened.  It was like we had lost three
family members.  Same for every family I knew.  I remember my father, an
incredibly stoic man, fighting back the tears as the story unfolded of the
deaths of these three "Right-Stuffers" that he had never met.

Wait a minute...What the hell am I talking about?

This isn't an us/them issue.  The point is that the crew and the JPL staff are
on the same side, and if the JPL staff wants to idolize the people who actually
go where JPL can only observe, then I'm glad they got the chance.  I'm pretty
sure that there was no display of weapons involved; no one was forced to get an
autograph under threat of reprisals.  I hope some of the crew asked for
autographs from the JPL folks.  Maybe someone got a Voyager or Gallileo
signature.

Lou Adornato    |  Statements herein do not represent the opinions or attitudes
Cray Research   |  of Cray Research, Inc. or its subsidiaries.
[e-mail]    |       (...yet)

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

Date: Sun, 10 Dec 89 04:00:19 PST
From: Eugene Miya <[e-mail]>
Subject: Frequently asked SPACE questions

This list does change.

This is a list of frequently asked questions on SPACE (which goes back
before 1980).  It is in development.  Good summaries will be accepted
in place of the answers given here.  The point of this is to circulate
existing information, and avoid rehashing old answers.  Better to
build on top than start again.  Nothing more depressing than rehashing
old topics for the 100th time.  References are provided because they
give more complete information than any short generalization.

Questions fall into three basic types:
1) Where do I find some information about space?
Try you local public library first.  You do know how to use a library, don't
you?  Can't tell these days.  The net is not a good place to ask for
general information.  Ask individuals if you must.  There are other sources,
use them, too.  The net is a place for open ended discussion.

2) I have an idea which would improve space flight?
Hope you aren't surprised but 9,999 out of 10,000 have usually been
thought of before.  Again, contact a direct individual source for
evaluation.  NASA fields thousands of these each day.

3) Miscellanous queries.  Sorry, have to take them case by case.

Initially, this message will be automatically posted once per month
and hopefully, we can cut it back to quarterly.  In time questions and
good answers will be added (and maybe removed, nah).

1) What happen to Saturn V plans? What about reviving the Saturn V
as a heavy-lift launcher?

Possible but very expensive -- tools, subcontractors, plans, facilities
are gone or converted for the shuttle, and would need rebuilding,
re-testing, or even total redesign.

2) Where can I learn about space computers: shuttle, programming,
core memories?

%J Communications of the ACM
%V 27
%N 9
%D September 1984
%K Special issue on space [shuttle] computers

Other various AIAA and IEEE publications.

Computers in Spaceflight: The NASA Experience
James E.  Tomayko
1988?

3) SETI computation articles?

%A D. K. Cullers
%A Ivan R. Linscott
%A Bernard M. Oliver
%T Signal Processing in SETI
%J Communications of the ACM
%V 28
%N 11
%D November 1984
%P 1151-1163
%K CR Categories and Subject Descriptors: D.4.1 [Operating Systems]:
Process Management - concurrency; I.5.4 [Pattern Recognition]:
Applications - signal processing; J.2 [Phsyical Sciences and Engineering]:
astronomy
General Terms: Design
Additional Key Words and Phrases: digital Fourier transforms,
finite impulse-response filters, interstellar communications,
Search for Extra-terrestrial Intelligence, signal detection,
spectrum analysis

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

End of SPACE Digest V10 #334
*******************