The Next Giant Leap
For nine years, former NASA administrator
Dan Goldin enthusiastically endorsed the idea of sending
humans to Mars, but couldn't deliver either a mandate
or funding for human exploration beyond Low Earth Orbit
(LEO). His successor, Sean O'Keefe, confronted with
a straightjacketed budget, has studiously avoided discussing
the "Where Next" topic, too. I came face-to-face
with NASA's ongoing struggle with "the vision thing"
a year ago, just thirty minutes before suiting up for
my launch to the Space Station aboard Atlantis. In the
Cape crew quarters, chief of human spaceflight Joe Rothenberg
told me flatly that he saw little chance that astronauts
would rocket out of Earth orbit for at least the next
ten to fifteen years.
I was shocked. About to strap on a rocket
and head for the Space Station, my boss had just told
me that NASA was essentially marking time. Wasn't it
his job - and the Administrator's -- to develop the
public and leadership support for stepping beyond LEO?
What I saw was that NASA was intent on not rocking the
boat; rather than propose bold new initiatives, it would
wait for direction from the top. With the President
and nation now preoccupied with an open-ended war, and
budget surpluses proving ephemeral, we need a practical,
affordable near-term exploration goal that can muster
administration, congressional, and public support. Thirty
years after the last lunar landing, what objective can
blast us out of Earth orbit again?
The answer came into focus for me on Feb.
12, 2001, during my second spacewalk outside the Space
Station. Falling around the planet at five miles per
second, my space-suited hand gripping a golden handrail
on ISS's Destiny module, I had one of those moments
that crystallize in space and time to become an indelible
memory. The event that grabbed my attention was happening
almost 200 million miles away, where the asteroid probe
NEAR Shoemaker was making history.
As Bob Curbeam and I worked on outfitting
Destiny's exterior, mission controllers eased NEAR Shoemaker
toward the surface of asteroid 433 Eros. The little
spacecraft had rendezvoused with Eros a year earlier.
Now it was ending its mission with a spectacular gamble
-- a landing on one of the oldest objects in the solar
Beamer and I had just uncovered the Destiny's
new research window when our radios crackled with the
astounding news that NEAR Shoemaker had bounced down
on Eros' dusty terrain -- and survived! In my space
suit, sweaty with exertion, I was nevertheless hit by
a shiver of excitement, imagining what it would be like
to be EVA, not in Earth orbit, but a million miles away,
drifting over the rubble-strewn surface of a near-Earth
asteroid (NEA). Today I believe these intriguing objects
are the perfect stepping stones to Mars. Unlike that
distant goal, however, or a return to the Moon, Near-Earth
Asteroids can get us back in the business of exploring
terra incognita in a way that's doable, affordable,
and that advances us toward the eventual exploration
of Mars and the Moon.
What makes NEA's especially attractive
now is the convergence of our capability with their
accessibility. Over the past ten years, astronomers
have discovered hundreds of new NEA's, some in orbits
that are easily reachable, with only modest improvements
in human spaceflight technology. Here are five key reasons
why these mountain-sized objects should be our next
Near-Earth Asteroids are easier
to get to from LEO than the Moon.
Figuratively speaking, they're just off the next
exit down the cosmic interstate. We can make a relatively
short round-trip to NEA's in Earth-like orbits for
very reasonable amounts of rocket power. Already we
know of a handful of NEA's that can be reached on
round trips lasting six months to a year -- for a
velocity change, or V, no greater than that required
for a round-trip from LEO to the lunar surface (about
9.4 km/sec). But the flight times are shrinking steadily.
Last year, Leon Gefert of NASA's Glenn Research Center
found that a round trip to 1991 VG, a small NEA only
tens of meters across, would take as little as 60
days (including a 30-day stay at the asteroid). The
total V would be just 6.1 km/sec, and just 4.9 km/sec
if we stretch the trip out to 90 days. We expect hundreds
of similar objects are out there, just waiting to
These "weekend getaways" minimize exposure
to micro-g, cosmic radiation and solar flare hazards
(and are shorter than current ISS expeditions). And
since the astronauts on such a mission never get farther
from home than about a million miles, they can deal
with a severe systems failure by executing an abort
directly back to Earth.
Asteroids offer a rich and untapped
store of knowledge about the early solar system.
Unlike the rocks on the Moon or Mars, these splintered
fragments from the main asteroid belt (between Mars
and Jupiter) represent ancient, well-preserved material
from the age of planet formation. An array of asteroid
samples - chosen intelligently by field explorers
- would tell us how this original stuff from the solar
nebula coalesced into the zoo of protoplanets that
gave rise to Earth and its rocky neighbors. The resulting
science bonanza would dwarf the return from robotic
explorers in both quantity and quality.
Resources from NEA's can help us
reduce the cost of future space exploration.
These same ancient materials represent a rich
trove of natural resources that can replace some of
the bulk supplies we bring - at horrendous expense
- up from Earth. The shuttle hauls supplies to the
Station, for example, at a staggering $10,000 a pound,
with water and propellant making up much of each shipment.
But some NEA's, like their parent bodies in the main
belt, are composed of clay minerals that contain up
to 10% water. This easily liberated hydrogen and oxygen
could eventually satisfy our needs for rocket fuel
and life support fluids, and none of it will have
to be dragged laboriously out of a gravity field.
Asteroid exploration serves as
a practical hedge against the impact threat.
In January 2001, asteroid 2001 YB5, some 300 m
across, swung within 600,000 km of Earth, less than
twice the distance to the Moon. The impact of this
stadium-sized boulder would have devastated a region
stretching from New York to Virginia. Geologists exploring
a few NEA's could develop the asteroid structural
data needed to devise a practical diversion scheme,
an added payoff from our next venture out from LEO.
Sending astronauts to Near-Earth
Asteroids gets us moving towards Mars.
From my spacefarer's perspective, the most attractive
idea about "astronauts to asteroids" is
that all of the development costs are directly applicable
to an eventual Mars mission. The spacecraft will have
to do nearly everything required to go to Mars, save
for the landing itself. NEA voyages represent a natural
progression in difficulty, more challenging than the
dash-for-the-Moon Apollo missions, but less daunting
than a multi-year Mars expedition. So think of an
NEA mission as a shakedown cruise for a Mars trip:
the 21st-century equivalent of Apollo 8 or Apollo
10, invaluable rehearsals that greased the skids for
the first manned lunar landing. When it's time to
go to Mars, we'll scale up the propulsion and life
support capability for the landing mission - and we'll
already have invaluable deep space experience under
our belt. Asteroids get us moving in the right direction.
What would the encounter phase of an NEA
mission be like? The cruise vehicle would orbit from
a safe distance while sending field explorers down to
the surface. In the very low gravity field-measured
in thousandths of a g - these EVA's would be much more
like my delicate tiptoeing around the ISS than the hard-charging
marathons of the Apollo moonwalks. Tethering and delicate
control will be all-important, since an astronaut and
his tools could easily drift away from the surface.
More reminiscent of Apollo will be the dust problem.
Stirred up by sampling work or thruster firings, the
fine particles will take minutes to settle. Planetary
scientist Dan Durda of Southwest Research Institute
suggests that the astronaut experience will be analogous
to cave diving: near-weightless, with the slightest
wrong move stirring up a vision-obscuring cloud that
will dissipate only slowly. Instead of trying to stand
and walk on such a surface, an astronaut might be equipped
with a portable scaffold. The strong, light framework
could anchor him within arms' length of the work at
hand, yet prevent an embarrassing facedown drift into
the primordial dust. Imagine a souped-up MMU jetpack,
with adjustable struts to prop an astronaut in any desired
orientation. Each EVA would end at a central work platform,
where each spacesuit would get a thorough - and welcome
It's time for NASA to make a cogent case for moving
out of Earth orbit again. The reality is that Congress
is not going to hand over a hundred billion dollars
for a determined push to Mars anytime soon. Instead,
the agency must offer the President and nation a goal
that's new and exciting, technically doable, and affordable.
Using the lessons learned from ISS hardware, my guess
is that we could mount several manned NEA expeditions
for no more than about $30 billion, spread over ten
years - about the same as the Station's initial construction
costs. By way of comparison, that's about half of what
the government spent on agriculture - just last year.
We can afford this investment.
To get rolling, we should enhance existing
NEA search programs. That's how we'll find more attractive,
low- V mission targets. (NASA acted correctly in December
to restore funding for radar studies of NEA's.) The
agency should mount precursor missions to NEA's while
defining the scope and cost of human expeditions to
these bodies. Its decision to jump-start research into
nuclear power and propulsion is a good first move. And
focused research should continue on ISS to blunt the
hazards - micro-g deconditioning, radiation exposure,
and command and control - that will confront a crew
embarked on a months-long deep-space mission.
One challenge is already behind us - what
to name the asteroid expedition. The first venture beyond
Low Earth Orbit since Apollo should be called Virgo,
after the sixth constellation in the zodiac. Why Virgo?
Its name evokes a leap into virgin territory, yes. But
the clincher is to be found in the heavens: as the Sun
marches through the zodiac into Virgo, it leaves LEO
* * * * * *
Tom Jones is a planetary scientist,
writer, consultant, and former astronaut. On four space
shuttle flights he racked up three spacewalks and fifty-three
days in orbit.
© 2002 by Thomas D. Jones