As the 40th anniversary
celebrations of the first manned moon landing end, a human voyage to Mars
remains a holy grail for NASA.
"We're still
looking at human exploration of Mars as one of the goals of the future at the
top level," said NASA researcher Bret Drake with Lunar and Mars
Integration at Johnson Space Center in Houston. "Having a human actually
set foot on another planet would be one of the greatest adventures possible,
one of the greatest monuments to history."
A crewed mission to the
red planet is a daunting challenge that lies at the edge of current
technological capabilities and possibly beyond. Still, NASA keeps a strategy to
go there and constantly keeps up to date with new ideas.
"Mars is one of
those targets of fascination that has been around a long time," Drake
said.
How to get there
A voyage to Mars would
take a crew about 180 days. So far NASA is exploring two options for propulsion
there ? a nuclear
thermal rocket and a chemical engine.
A nuclear thermal
rocket, based off designs from the '60s and '70s, would use a nuclear reactor
to super-heat a gas and blast it out the nozzle to generate thrust. "It's
a very high-performance vehicle, and we think it's very safe, not radioactive
at launch, but it is a nuclear system," Drake said. "The idea for the
chemical engine is similar to that used on the space shuttle, liquid oxygen and
liquid hydrogen. It's a fairly well-known technology, but it's not as efficient
as nuclear thermal."
To reach the Martian
surface, NASA envisions an aerodynamic lander that
flies down with thrusters to help it descend. The ascent vehicle that takes the
crew back into space for the six-month trip home will likely rely on a
combination of methane and liquid oxygen. "Oxygen is present in the
Martian atmosphere in the carbon dioxide, so you can use resources on Mars to
make it," Drake said.
Before the crew even
gets to Mars, the plan is to send as much cargo there ahead of time as possible.
"That way we can
know it's operating right before we ever commit the crew," Drake said.
"A Mars mission is not like a lunar mission where you can come home at any
time ? once they're committed, a crew is out there for years."
By current NASA
estimates, a crewed mission to Mars needs to lift about twice the mass of the
International Space Station into space ? roughly 1.76 million lbs. (800 metric
tons) of technology. To launch the equipment, NASA plans on using the Ares
V rocket, designed
to be the most powerful rocket ever built and capable of carrying about 414,000
lbs. (188 metric tons) to low Earth orbit at one time.
"We're going to try to minimize
the amount of assembly needed," Drake said. "The heavy lift capacity
we'll have with the Ares V will allow for simple automatic rendezvous in orbit
and docking of components."
The crew would ride up in one of the
upcoming Ares I
rockets before starting the voyage to Mars.
"Having humans in
place could bring a wealth of experience and training and the ability to put
into context what they see and to make real-time decisions, all things
difficult to do with robots," Drake said.
The very habitat the
crew stays at on the Martian surface would be sent ahead of time. "You can
also do things like produce and store oxygen from resources at Mars beforehand
for the crew and the ascent vehicle. You could generate water as well."
Big crew,
long stay
NASA envisions a crew of
six astronauts for a Mars mission. "That's about what's required for the
skills needed ? a commander, scientist, engineer, medical officer, things like
that, as well as cross-training," Drake said. "They'll need expertise
in a wide range of disciplines."
Currently NASA envisions
a long stay for a crew at Mars, about 500 days.
"Crew autonomy is
vital, because there's an up to 40 minute time delay in communication between
Earth and the crew because of the distance," Drake said. "And the
crew doesn't have a capability for re-supply ? they'll just have what they send
ahead or what they bring with them ? so when things fail, they'll have to be
able to repair them. They must be self-sufficient."
To survive the voyage,
air and water need to be completely recycled regularly.
"We're learning a
lot on the International Space Station right now on air revitalization and
water recovery," Drake said. "What's nice about Mars is that there's
carbon dioxide in the atmosphere, so that can help get us oxygen and water for
the crew. In terms of food, we're looking at smaller systems, 'salad machines,'
to grow food for the crew. Fresh food is not only good for nutrition, but good
for the mind as well. A fresh tomato can really boost psychology."
Mental and physical
challenges
The long hardship of
roughly two-and-a-half years in space with only a few people in a potentially
lethal environment will undoubtedly challenge the psyches of Mars explorers.
"The Russians are conducting
a test right now that hopefully will shed light on the behavioral sciences
aspect of a Mars mission," Drake said. "Looking at other remote
exploration endeavors is helpful as well ? Antarctica, or submarines
? all that feeds into the human behavioral aspects of crew
selection."
A key concern for
astronauts as well as during the stay on Mars is dangerous radiation in the
form of storms of high-energy particles from the sun as well as cosmic rays
from deep space. "The best radiation protection material is hydrogen, or
water, which is rich in hydrogen," Drake said.
On the surface of Mars,
NASA envisions that cargo deployed ahead of time can produce water before the
crew arrives to use as a shield during the crew's stay there. On the way to and
from Mars, the ship could be configured so that water and food surround areas
where crew spend most of their time, but "a 'storm shelter' aboard the
ship will be an integral part for short events of radiation that can be
lethal," Drake said.
No firm date has been
set for any potential Mars mission, but it remains of keen interest not just to
NASA, but also others, such as
China.
"It's humanity's
next step to understanding and expanding our presence outward," Drake
said. "We view human exploration of Mars as being an international
endeavor, most likely not limited to just one country, but probably of global
scale.
- Gallery:
Mars Base of the Future
- Top 10 Russian
Space Missions
- All About Mars
