The Planetary Report Volume 28 Issue 2

2008·1.6 MB·English

The
Volume XXVIII Number 2 March/April 2008
Visions of Exploration
From The Editor
We like to look back at the time of Apollo On the Cover:
and remember how, for a brief moment, This mosaic view of Mars’ north polar region is composed of wide-angle
the people of Earth pulled together to place a camera daily global mapping images taken byMars Global Surveyorin
man on the Moon. October 2006. The polar cap is visible at center right, and two annular
Memories can be faulty. Opinion polls taken (somewhat circular) clouds are visible at upper left. Annular clouds are
at that time repeatedly showed that the public common in midnorthern summer in Mars’ north polar region, and they
was never solidly behind the space program. may be from eddy currents in the lower atmosphere.
Among political leaders, scientists, and engi- Although most of Mars is dry, its polar regions are rich in water ice.
neers, there was never consensus on the right Phoenixis on its way to study the structure, composition, and chemistry
path to take. Books were written chronicling of soil and ice samples near the Red Planet’s north pole.
the decisions, from John F. Kennedy’s political Image: NASA/JPL/Malin Space Science Systems
resolve to land a man on the Moon to the engi-
Background:
neering choice to use lunar orbit rendezvous.
Nearly a half-century later, we are wrestling Opportunity’s Panoramic Camera took this image of the dunes inside
again with how to move humanity into space. Beagle crater on August 10, 2006 (Martian day, or sol, 905). Beagle,
Four years ago, U.S. President George W. Bush which is 35 meters in diameter, sits on the edge of the ejecta blanket
laid out his Vision for Space Exploration and surrounding the much larger Victoria crater (750 meters), located in
tasked NASA with finding the best path back Mars’ Meridiani Planum. Image: NASA/JPL/Cornell University
to the Moon and onward to Mars. This new
vision would be bigger than Apollo, be far
more expensive, and last many more years.
Figuring out how to do that—and get the
fractious community of scientists, engineers,
and policy makers to agree—has been, as they
say, like herding cats. The Planetary Society,
with Stanford University, brought together
representatives of the space community in a
workshop called “Re-examining the Vision.”
This spring, through a series of town hall meet-
ings, we are inviting the public to contribute
their views.
To explore space is difficult. We must choose
Contact Us
to do what is hard. Join us as we seek a way
Mailing Address: The Planetary Society,
back to the Moon—and on to Mars.
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—Charlene M. Anderson
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THE PLANETARY REPORT MARCH/APRIL 2008
Cofounder
CARLSAGAN
1934–1996
Board of Directors
Chairman of the Board
DAN GERACI
Chairman and CEO,
Club Achilles—The Iron Age
President
Contents NEIL deGRASSETYSON
Astrophysicist and Director, Hayden Planetarium,
American Museum of Natural History
Vice President
BILL NYE
science educator
4 Opinion—
Executive Director
LOUIS D.FRIEDMAN
On the Road to Mars: JAMES BELL
Professor of Astronomy, Cornell University
HEIDI HAMMEL
Three Stepping-Stones Senior Research Scientist and Co-Director,
Research, Space Science Institute
G. SCOTT HUBBARD
and a Stumbling Block professor, Stanford University
WESLEY T.HUNTRESS JR.
Director, Geophysical Laboratory,
Carnegie Institution of Washington
by Robert Farquhar
LON LEVIN
SkySevenVentures
Advisory Council Chair
CHRISTOPHER P.McKAY
10 A Message to the Future: planetary scientist
BRUCE MURRAY
Professor of Planetary Science and Geology,
Visions of Mars California Institute of Technology
ELON MUSK
Chairman and CEO, SpaceX
by Peter Hollingsworth Smith
JOSEPH RYAN
Ryan Investments, LLP
STEVEN SPIELBERG
director and producer
14 Annual Report
GEORGE YANCOPOULOS
President and Chief Scientific Officer,
Regeneron Research Laborabories
to Our Members
International Council
ROGER-MAURICE BONNET
Executive Director,
International Space Science Institute
17 World Watch
YASUNORI MATOGAWA
Associate Executive Director,
Japan Aerospace Exploration Agency
18 We Make It Happen! RISTO PELLINEN
Director of Science in Space Research,
Finnish Meteorological Institute
20 Questions and Answers
Advisory Council
22 Society News BUZZALDRIN
RICHARD BERENDZEN
22 Members’ Dialogue JACQUES BLAMONT
RAY BRADBURY
DAVID BRIN
FRANKLIN CHANG-DIAZ
FRANK DRAKE
OWEN GARRIOTT
GARRY E.HUNT
BRUCE JAKOSKY
THOMAS D.JONES
SERGEI KAPITSA
CHARLES E.KOHLHASE JR.
LAURIE LESHIN
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Although those interested in off-Earth human explo- by Robert Farquhar
ration generally agree that Mars is a key destination,
I
n its Vision for Space Exploration (VSE), NASA has
opinions differ regarding the steps for getting humans
focused on a Moon base as the next logical step on
to the Red Planet. Some advocate going directly to the road to Mars. As specific plans become more
defined, however, it is becoming painfully obvious that
Mars without any intermediate destinations, whereas
the Moon is not a stepping-stone to Mars but is instead
a stumbling block. The enormous cost of Moon base
others believe we need to practice at the Moon before
infrastructure will drastically reduce the funding available
taking on the big step of sending humans to our near- for science programs and related exploration. If NASA’s
lunar base strategy is allowed to proceed, human missions
est planetary neighbor. The interim technical steps
to Mars will be delayed by at least 50 years.
Proponents of the concept of a Moon base advertise
continue to be debated, and this article presents one
three main benefits. They cite the utility of a Moon base
4 aspect of the debate. —Editor as a hub for expanded human exploration of the lunar
THE PLANETARY REPORT MARCH/APRIL 2008
surface. They also say the Moon could serve as a platform
for large telescopes. Finally, the lunar aficionados claim Libration Points in the Vicinity of the Earth
the Moon would be an ideal place to test the technologies
and techniques that will be needed for human missions to
Mars. All three of these justifications are questionable at
best.
Exploration of the Moon’s surface, if it is a goal worth
pursuing, can be accomplished more efficiently by robotic
spacecraft, and at a much lower cost. Placing large tele-
scopes on the dusty Moon makes no sense either (with
the possible exception of a radio telescope on the Moon’s
far side); space-based telescopes offer a far better option
in terms of performance, accessibility, and cost—with no
lunar dust. Finally, the notion that the Moon could serve As shown by the eminent French mathematician Joseph Lagrange in 1772,
as a proving ground for Mars missions strains credulity. there are five positions of equilibrium in a rotating two-body gravity field. A
spacecraft placed at one of these points with the proper velocity would be in
Try to imagine the Lunar Surface Access Module
equilibrium because its centrifugal acceleration would be balanced by the
(LSAM), a vehicle designed for an airless environment,
combined gravitational attractions of the two bodies. There are seven of these
ever landing on Mars. “libration points” near Earth—five belonging to the Earth-Moon system, and
For these reasons and many others, the VSE needs two belonging to the Sun-Earth system. Diagrams: Courtesy of the author
a major course correction. The time has come for the
space interest community to speak up and tell NASA
management that its Moon base proposal “has no of milestones in space, each of which will literally bring
clothes.” Fortunately, there is an alternative focus for us closer to Mars.
VSE that avoids the lunar cul-de-sac.
Smart Use of Libration Points
The IAA’s Next Steps Study The L1 and L2 libration points of the Sun-Earth system
An alternative plan, based on a study done under the aus- have become increasingly popular for scientific space-
pices of the International Academy of Astronautics (IAA), craft. This is because libration points provide an opportu-
improves on the NASA Moon plan in several ways. The nity for a small body such as a space telescope to maintain
s most important is that it offers a credible path toward the a steady position almost for free. Orbits around libration
er
y goal of human presence on Mars. The IAA plan also gets points are inherently unstable, so some stationkeeping
M
er more science done along the way, it provides vehicles and maneuvers are required every three months or so, but the
Walt know-how that will be needed for Mars missions, and, associated costs are quite small. The delta-V (amount of
by crucially, it avoids burying the whole enterprise of explo- effort required to adjust orbital trajectory) is only about
s
o ration in Moon-specific costs. three meters per second per year.
b
o
h A significant cost-managing feature of the IAA plan is On November 20, 1978, the International Sun-Earth
P
nd its emphasis on reusable hardware. One of the reusable Explorer-3(ISEE-3) became the first libration point
a
s elements is a crew transfer vehicle stationed in low Earth spacecraft when it was inserted into a halo orbit around
ar
M orbit (LEO). Vehicles of this type would be used repeatedly the Sun-Earth L1 point. The highly successful flight of
for round trips to destinations at intermediate distances— ISEE-3demonstrated the utility of libration point orbits.
for example, servicing space-based telescopes at Sun- Between 1995 and 2001, five more spacecraft took advan-
Earth libration points. This LEO-based vehicle, or Deep tage of these locations.
Space Shuttle, would provide the basis for the develop- Others will soon follow. Beginning this year, halo orbits
ment of a similar, but much larger, crew transfer vehicle around the Sun-Earth L2 point will be the locations of
for longer hauls. The long-haul version, also reusable, choice for a number of large astronomical facilities, in-
would be parked at Sun-Earth L2 for trips to interplane- cluding the James Webb Space Telescope (JWST). The
tary destinations. L2 site offers a number of key advantages, including a
The IAA study proposes a three-step approach: spectacular view. With the Sun, Earth, and Moon behind
it, a space telescope at L2 can observe more than half of
1. establishment of a staging node near Sun-Earth L2 all space at all times. The short distance to Earth enables
for human missions beyond the Earth-Moon system, easy communications, and thermal control is simpler than
2. a human mission to a near-Earth asteroid, and it would be with lunar day/night cycles.
3. a human mission to one of the Martian moons.
Servicing Sun-Earth L2 Telescopes
Instead of sinking resources into a Moon base, the IAA One of the most significant achievements of the space
strategy is organized around a more cost-effective series shuttle program was servicing the Hubble Space Tele- 5
THE PLANETARY REPORT MARCH/APRIL 2008
The establishment of a staging node at the Sun-Earth L2
point would prepare human explorers to venture beyond
the Earth-Moon system to these nearby worlds. Above,
astronauts tend to a mining operation on Mars’ moon
Phobos. Illustration: Pat Rawlings
A colony with an observatory has been built inside a crater on an Eros-like
near-Earth asteroid. Illustration: Hannu Parviainen
scope. The JWST mission is not designed for human ser- the DSS would be somewhere between 5 and 6 kilometers
vicing, but the need for maintenance and repair capabili- per second. The delta-V requirement could be reduced,
ties is inevitable as L2 telescopes become larger, more however, by roughly 3.2 kilometers per second if an ex-
complex, and more expensive. With that in mind, the IAA pendable Earth departure stage is employed.
study team looked at servicing L2 telescopes as an initial The baseline mission profile for a DSS trip from LEO
step toward expanding human space activities beyond to L2 and back is summarized in the diagram on page 8.
LEO. One way to acquire this capability would be to It is interesting to note that the delta-V requirement for
develop a reusable vehicle called the Deep Space Shuttle the transfer to L2 is virtually identical to the delta-V cost
(DSS). The primary components of the DSS would be for a transfer between LEO and a low lunar orbit. The
cost is the same, even though the transfer time for L2
• a service module with quarters to support a crew of is almost four times as long.
three or four people for flight times of up to 50 days; An interesting alternative strategy for servicing L2
• a detachable, Apollo-style reentry capsule (the Crew telescopes would, so to speak, bring the mountain to
Exploration Vehicle [CEV] under development by NASA Muhammad. That is, the L2 telescope would travel to
would be a logical candidate for this component); and an elliptical Earth orbit using a lunar gravity–assist
• a chemical propulsion system using storable propel- maneuver. A DSS crew would service the telescope in the
lants such as liquid oxygen/methane. elliptical Earth orbit, and then the telescope would return
to L2 with a second lunar gravity assist. The delta-V cost
As for its technical characteristics, the DSS is envi- for this lunar double-swingby scenario is very small (less
sioned as a one-and-a-half-stage vehicle (that is, a core than 25 meters per second). With this technique, the
6 stage with drop tanks). The total delta-V capability of round-trip flight for the DSS would be reduced to 14 days,
THE PLANETARY REPORT MARCH/APRIL 2008
The first human visitors to Mars face an environment nearly
as hostile as that of Earth’s Moon. Illustration: Walter Myers
and the delta-V savings would be at least 1 kilometer per • A propulsion module, which could be reusable or ex-
second. pendable depending on the flight rate and advances in
The development of a DSS will be a critical element in rocket engine technology. Use of a nuclear thermal rocket
the architecture, enabling human crews to reach more dis- could also be considered to achieve shorter transit times.
tant destinations. • A detachable and reusable Apollo-style reentry capsule.
Sun-Earth L2 Staging Node The general mission scenario for trips to interplanetary
Although the DSS would have the ability to transport astro- destinations using the L2 staging concept is outlined in the
nauts to destinations well beyond the Moon’s orbit, a larger diagram on page 9. The empty ITV, parked in a halo orbit
and more capable transfer vehicle will be needed for flights at Sun-Earth L2, is summoned to an ellliptical Earth orbit
to near-Earth asteroids, to Phobos or Deimos, and to Mars. to rendezvous with the crew. Small propulsive maneuvers
To satisfy this requirement, the IAA study calls for a re- (total delta-V less than 50 meters per second) and lunar
usable vehicle based in a halo orbit around the Sun-Earth gravity assists are used to target the final perigee delta-V
L2 point. This Interplanetary Transfer Vehicle (ITV) would maneuver. A DSS “taxi” transfers the crew from LEO to
carry astronauts to and from interplanetary destinations. the ITV in its elliptical Earth orbit.
The proposed components of the ITV are as follow: With the crew aboard and all systems checked out, the
ITV executes an Earth-escape maneuver and proceeds to
• A crew module that could support five or six people for its interplanetary destination. After completing the mis-
flight times up to three years. This module would be con- sion, the ITV brings the crew back to Earth’s vicinity, and
structed at L2 over a period of several years. Early versions the crew uses the reentry capsule to return to Earth. The
would be used for excursions to near-Earth asteroids. ITV, without crew, then uses a perigee maneuver for Earth 7
THE PLANETARY REPORT MARCH/APRIL 2008
Halo Orbit Around the LLiibbrraattiioonn--PPooiinntt MMiissssiioonnss
Sun-Earth Libration Point 11997788––22001155
Sun-Earth Date of Orbit
Mission Libration Point Insertion Mission Purpose
—————————————————————————————————————————————
ISEE-3 (NASA) L1, L2 1978, 1983 Solar wind, cosmic rays,
plasma studies
WIND (NASA) L1 1995, 1997 Solar wind monitor
SOHO (ESA/NASA) L1 1996 Solar observatory
ACE (NASA) L1 1997 Solar wind, energetic particles
MAP (NASA) L2 2001 Cosmic microwave background
Genesis (NASA) L1 2001 Solar wind composition
Herschel (ESA) L2 2008 Far-infrared telescope
Planck (ESA) L2 2008 Cosmic microwave background
GAIA (ESA) L2 2012 Galactic structure, astrometry
A halo orbit is unusual in that it has no planet or other massive body at its center.
JWST (NASA) L2 2013 Deep space observatory
The halo orbit around the Sun-Earth L1 libration point is illustrated here. This was
the mission orbit for NASA’s ISEE-3,and ESA’s SOHOspacecraft. XEUS (ESA) L2 2015 X-ray spectroscopy
Darwin (ESA) L2 2015 Infrared space interferometry
————————————————————————————————————————
Abbreviations:
ISEE (International Sun-Earth Explorer) GAIA (Global Astrometric Interferometer
Mission Scenario for Telescope Servicing
SOHO (Solar Heliosphere Observatory) for Astrophysics)
at Sun-Earth L2 Libration Point ACE (Advanced Composition Explorer) JWST (James Webb Space Telescope)
MAP (Microwave Anisotropy Probe) XEUS (X-ray Evolving Universe Spectrometer)
Left: This is a typical mission scenario for servicing telescopes located in
the vicinity of the Sun-Earth L2 libration point. Step 1: The Deep Space
Shuttle (DSS) leaves low Earth orbit (LEO) at delta-V of about 3,230 meters
per second. Here, the first set of drop tanks is discarded. Step 2: The DSS
enters L2 orbit at delta-V of about 900 meters per second. Step 3: The
crew services the L2 telescope. Step 4: The DSS leaves L2 orbit at delta-V
of about 900 meters per second. Step 5: Astronauts return to Earth in an
Apollo-style capsule, and the DSS returns to LEO using multiple aero-
braking maneuvers.
capture, followed by lunar gravity assists and small such as telescopes with apertures of 30 meters or more,
propulsive maneuvers, to return to its L2 base. components for ITV construction, and propellant for ITV
flights.)
Mission to a Near-Earth Asteroid The 2025 opportunity for a mission to asteroid 1999
It’s reasonable to ask why we should keep the ITV parked AO10 is appealing for a number of reasons:
at Sun-Earth L2 rather than in a low Earth orbit. To under-
stand the performance advantage of basing a reusable ITV • It would be a perfect rehearsal for a human mission to
at Sun-Earth L2, it is instructive to compare the delta-V Phobos or Deimos.
costs of the two staging locations for an example mission • The round-trip flight time is only five months, with a
to a near-Earth asteroid. A particularly good opportunity 30-day stay at the asteroid.
for an early piloted mission to a near-Earth asteroid is • The ITV would always remain within 0.08 AU of the
illustrated in the figure at the top left of page 9. Earth (AU = astronomical unit, the average distance be-
An ITV operating from L2 can perform this mission for tween Earth and the Sun, about 93 million miles or 150
a delta-V cost of only 4.9 kilometers per second, which is million kilometers).
less than half the cost for an ITV based in LEO. Savings
of this magnitude would be enough to preclude the need The mission would have the robust capability to turn
for a heavy-lift launch vehicle such as the Ares 5. (Acqui- around and come back if necessary. Even a week after
sition of an Ares 5 launcher may be desirable for other the Earth-escape maneuver, the ITV would have enough
8 reasons, including delivery of very large payloads to L2, remaining delta-V capability to return home in less than
THE PLANETARY REPORT MARCH/APRIL 2008
Five-Month Mission to
Near-Earth Asteroid 1999 AO10
Below: The basic steps for a reusable Interplanetary
Transfer Vehicle (ITV) to carry human explorers to
and from destinations beyond the Sun-Earth-Moon
system (near-Earth asteroids, Phobos and/or Deimos,
and Mars) are mapped out here.
Interplanetary Transfer
Vehicle Mission Scenario
Above: This is the trajectory profile for a five-month
interplanetary round-trip mission to the near-Earth
asteroid 1999 AO10. A reusable ITV parked in orbit
at Sun-Earth L2 is more than twice as efficient as
one based in LEO in terms of delta-V cost (energy
expenditure) because the L2 point is located at the
edge of Earth’s gravity well.
four days. If successful, the mission to this near-Earth beyond the Moon’s orbit for the first time. Emplacement
asteroid would take its crew farther into deep space than of large astronomical observatories near the Sun-Earth
humans have ever traveled. L2 libration point will be a proud achievement, flowing
from rather than competing with high-priority science,
A Future for Human Spaceflight and it will capture imaginations throughout the world,
No such flight can take place if the Moon base now on as Hubble did. Development of a substantial and capable
the drawing board sucks every budget dollar from NASA’s ITV, with shielding and living quarters for astronauts to
scientific programs. The Moon base, though promoted as travel to Mars in safety and comfort, will give the public
a return to space, therefore in fact represents a dead end. its first true interplanetary spaceship.
In contrast, the IAA strategy points the way toward practi- If plans for a Moon base don’t stop us in our tracks,
cal exploration, with a realistic possibility of human expe- the path ahead can lead human explorers to an asteroid,
ditions to Mars before 2050. to a Martian moon, and then to Mars.
Looking at the long term, it is vital to the future of hu-
man spaceflight that NASA plans and missions generate Space provocateur Robert Farquhar holds the Charles A.
public enthusiasm. We have to inspire people by planning Lindbergh Chair in Aerospace History at the Smithsonian
and doing things that have never been done before. The Air and Space Museum.
IAA plan identifies a series of new accomplishments,
each extending our reach into the solar system. Views expressed in this article are those of the author and do not
The Deep Space Shuttle will take human missions necessarily represent those of The Planetary Society. 9
THE PLANETARY REPORT MARCH/APRIL 2008
A Message to the Future: “Visions of Mars”
A Message to the Future: “Visions of Mars”
The Phoenixspacecraft is nearing its May 25,
2008 landing on Mars. On board is a silica
glass mini-DVD provided by The Planetary
Society that includes a quarter-million names
(including those of all Planetary Society mem-
bers) and a collection of Mars-related literature,
art, and audio called Visions of Mars.
Phoenix’s principal investigator, Peter Smith
from the University of Arizona, wrote a special
introduction toVisions of Mars. It is included
on the mini-DVD. In it, he sends a message to
the future explorers who may one day find the
mini-DVD, describes thePhoenixmission and its
goals, and also reflects on our hope of reaching
into the future with our message from Earth,
Visions of Mars.
Here, we share part of Peter’s essay. The
complete essay, as well as details about the mini-
DVD and Visions of Mars, is at the Society’s
website at planetary.org/phoenixdvd.
—Bruce Betts, Director of Projects
by Peter Hollingsworth Smith
T
his message precedes a collection of stories
and essays that are intended as a time cap-
sule. Most of these stories come from the
most famous science fiction writers of our day.
They springboard from the latest scientific knowl-
edge to weave visionary tales of the future. In
return, the stories inspire young readers to dream
of magical futures and, later as adults, to become
part of the leading edge of scientific discovery.
This cyclical exchange between fact and fiction
is the basis for the creative art of science.
Reading these stories offers us insight into the
hopes and fears of society. Edgar Rice Burroughs’
stories of conquering monsters and befriending
aliens remind us of the still-recent expeditions
into the savage and untamed Rockies in the early
nineteenth century. More recent novels lead to the
terraforming and colonization of Mars, ideas that
clearly come from humankind’s successful taming
of Nature on every continent.
The circular feature in this image, captured by Mars Global Surveyor’s Mars
Orbiter Camera, is a partially buried crater in the Martian arctic. It is surrounded, What brave soul might decode this mini-DVD
and partly overlain, by some of the many sand dunes in the area. In summer, after recovering it from the north polar region on
the dunes in this scene would appear darker than their surroundings, but in this Mars? Possibly a member of a future society that
northern springtime image, the dunes—and everything else in the area—are
10 covered with carbon dioxide frost. Image: NASA/JPL/MSSS has sent astronauts and pioneers to explore the
THE PLANETARY REPORT MARCH/APRIL 2008