GOLDEN, Colo. – NASA's Constellation Program – including the
deployment of the Orion crew vehicle replacing the space shuttle – will first
be assigned to International Space Station flights, then propel humans and
cargo to the Moon. Expeditionary missions to Mars and beyond will follow.
But there's ongoing discussion of mounting a piloted mission
to an asteroid – a voyage by astronauts to a near-Earth object,
termed NEO for short. These proponents feel certain of the scientific payoff
from reaching, first-hand, an asteroid – perhaps even becoming able to exploit
these chunks of celestial flotsam to further humankind's plunge into the
cosmos.
Space technologists argue that a NEO trip could be a
valuable shakeout of people, equipment, and procedures prior to hurling
astronauts beyond the Moon to the distant dunes of Mars.
For others, NEOs are viewed as downright dangerous, in terms
of a head-on collision between Earth and a space rock. It's best to get to know
these incoming beasts ahead of time.
NASA's NEOphytes
Internal looks by a small group of NASA
"NEOphytes" have projected that a human trek to one of those
mini-worlds may involve two or three astronauts on a 90 to 120-day spaceflight,
including a week or two week stay at the appointed asteroid.
Dispatching astronauts to a NEO is a sensible idea, said
Harrison Schmitt, Apollo 17 astronaut, geologist and current chair of the NASA
Advisory Council (NAC).
In fact, the Exploration and Space Operations subcommittees
of the NAC were briefed July 18 by NEO study team members from the NASA Johnson Space Center, although there has been no Council action on the topic.
Schmitt told SPACE.com: "I think examination of a NEO
mission and the development of the stand-by monitoring systems, plans,
protocols and procedures for the diversion of a potentially Earth-impacting
asteroid would be very prudent activity for the U.S. to undertake."
Additionally, Schmitt said that a NEO mission would be a
potentially important demonstration of the versatility and capability of the
Constellation systems and a "gap-filler" before any Mars landing
mission.
"So far, the arguments for asteroid science and
resources are interesting, but not well-developed or potentially as
historically or politically persuasive as a demonstration of long-term Earth
defense," Schmitt said.
Extended flight
At this point in time, NASA has not issued any formal
requirements to augment the Orion
spacecraft to handle a piloted NEO mission, explained John Stevens,
Director of Business Development for the human spaceflight line of work at
Lockheed Martin Space Systems, near Denver, Colorado.
However, the company – builder of the crew-carrying Orion
spacecraft – internally funded two years worth of studies to flesh out
technologies to support a diversity of destinations, Stevens said. For sojourns
to a near-Earth asteroid, he said, future block upgrades to Orion are
necessary.
"It's not that difficult from an architecture point of
view to fly by an asteroid and then come back," Stevens said. But pulling
off a rendezvous and docking with such an object, then rocketing back to Earth,
requires more propulsion oomph, he noted, along with the need for larger living
quarters for transiting crews, as well as recycling hardware to handle oxygen
and water needs.
Also, any roundtrip – Earth-to-NEO-to Earth – is an extended
flight, way beyond that required for Moon travel. So that brings up crew
psychological-sociological issues. "It's a concern...but we don't know how
much of a concern," Stevens advised.
Stevens said that the near-Earth object human mission can be
viewed as an intermediate step between a Moon mission and a Mars mission.
"In terms of complexity and the length of time that you have to stay
out...it does represent a good stepping stone between the kinds of missions you
do at the Moon and the kinds of missions that you next bite off...which is the
Mars mission," he said.
Visualize this space
DigitalSpace, a privately held company based in Santa Cruz, California, has just released a design simulation of a notional crewed
mission to an as-yet identified asteroid.
"This visualization is DigitalSpace's design concept
for the mission, produced as an independent effort for the benefit of an
internal NASA feasibility study completed in 2007," said Bruce Damer, founder
of the company that provides leading edge Internet content and tools for
communication, collaboration, and visualization.
The NASA study was performed to show that such a mission is
possible with the new Constellation architecture, Damer said. DigitalSpace
received input from numerous experts inside and outside NASA to produce the NEO
mission visualization.
"It is important to note that this is not a NASA
concept, nor has NASA given it any kind of technical blessing...it is a design
created by the DigitalSpace team to stimulate discussion in the space
community," Damer emphasized.
Indeed, many in the space community see any pilgrimage to an
asteroid – by either robots or astronauts – as having multiple benefits.
Tooling up for NEOs
Learning about NEOs offers much in both scientific and
practical terms. That's the perspective offered by Clark Chapman, a planetary
scientist at the Southwest Research Institute's (SwRI) Department of Space
Studies in neighboring Boulder, Colorado.
The reasons are many, Chapman said: Because there are many
of them, because they are made of materials both common and exotic compared
with materials available near the Earth's surface, and because they have
negligible gravity...they are an obvious source of raw materials for future human
exploration of outer space.
Tooling up for NEOs is already being tackled by specialists
at Ball Aerospace & Technologies Corporation, also in Boulder. They have
been looking into a small, low-cost landing probe design that could
characterize both the surface and interior of small solar system objects, such
as an asteroid.
The device is about the size of a basketball and weighs just
a few pounds, said Dennis Ebbets, Senior Business Development Manager for Ball
Aerospace's Space Science division. He and staff consultant, Richard Reinert,
along with Rich Dissly, Ball's Deputy Director for Solar System Advanced
Systems, suggest that several of the probes could be hauled to a target object
and deployed individually.
Once released, these non-propulsive surface probes would
freefall onto an asteroid's surface and begin transmitting results from their
respective locales. The probes are outfitted with deployable panels to ensure
self-righting to begin their errands.
Each self-energized probe might employ tiny imagers,
accelerometers, x-ray spectrometers, sample collection and analysis gear –
perhaps even utilize small explosive charges to create seismic waves that help
gauge an asteroid's internal structure.
While asteroid surface probes could be deployed from an
automated spacecraft, they are also a "perfect candidate" to be toted
onboard a human expedition to a near-Earth object, Ebbets told SPACE.com.
Ebbets said asteroids deserve attention to help figure out
what they are, where they come from, why they are different, and why there are
families of these objects that are the same.
Additionally, "there's a non-zero chance of being hit
by one of these things," Ebbets noted. He said he was a big fan of
dropping a transponder onto an asteroid that's been branded as a potential
troublemaker.
"Putting a transponder on it would be an excellent
thing to do," Ebbets added. "You can get a very, very accurate
orbit...predict years into the future whether it's on a collision course with us
or not."
Long-delayed expectations
Along with the need to come to grips with scalawag asteroids
that could harm Earth, SwRI's Chapman senses other NEO exploration outcomes.
"Though I am a space scientist strongly oriented
toward the cost-effective robotic exploration of the solar system, I also grew
up on science-fictional accounts of human expansion into the cosmos, and I
endorse that more expensive – but ultimately inevitable – direction for human
exploration," Chapman said.
Chapman said that it makes sense to him that NEOs could be
used as "way-stations" to Mars. "Human visits to NEOs can go
part-way toward understanding the challenges of going to Mars, yet not invoke
the most serious challenges," he said.
Regarding concerns in some quarters that efforts to send
humans to NEOs may be a distraction from the main, early focus of sending
humans to the Moon, Chapman said: "In the current environment where the
'Vision' dominates NASA and the budget tends to restrict what we might do under
the umbrella of the 'Vision' to the narrowest aspect of the 'Vision'...the focus
must be on the Moon."
More than the Moon
But Chapman continued by noting that the dreams of people
worldwide who want to expand their long-delayed expectations of going into
interplanetary space, NASA – assisted by the budgetary processes in the
Congress – must find a way to do more than just return to the Moon.
"I happen to believe that scientific exploration of the
Moon...could be extremely significant. And the Moon is much more easily explored
and developed than Mars, which must remain a longer term challenge. But NEOs
offer a special, practical, and inspiring challenge that we should keep on the
table," Chapman explained to SPACE.com.
In the context of the hazard of
destructive impacts by NEOs on the Earth, Chapman said that
"everything we can learn about the physical nature of NEOs can
incrementally enhance our chances of dealing effectively with one, should one
be discovered that seriously affects us." He explained that robotic
exploration of such a NEO would be essentially as good as human exploration of
that threatening object.
"But the generic exploration of NEOs – even if solely
in the goal of getting to Mars – can have side benefits not only for
understanding the range of issues we might have in dealing with a threatening
NEO, but also in learning how we might mine the resources of NEOs for future
use in human exploration of the solar system," Chapman concluded.
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