"Robotic missions are much cheaper and may provide more scientific information, but they don't catch the public imagination in the same way, and they don't spread the human race into space, which I'm arguing should be our long-term strategy," says Stephen Hawking. "If the human race is to continue for another million years, we will have to boldly go where no one has gone before."
The answer to this question is at the core of one of the greatest of the ongoing debates in space exploration: the question of man vs. unmanned robotic missions.
NASA currently operates more than 50 robotic spacecraft that are studying Earth and reaching throughout the solar system, from Mercury to Pluto and beyond. Another 40 unmanned NASA missions are in development, and space agencies in Europe, Russia, Japan, India and China are running or building their own robotic craft.
What is not commonly known however is that many of NASA's leading scientists also champion human exploration as a worthy goal in its own right and as a critically important part of space science in the 21st century. The Obama administration's new NASA strategy that strongly favors robotic exploration, has opened the debate anew.
"Tomorrow’s NASA space program will be different," says Wallace Fowler of the University of Texas, a renowned expert in modeling and design of spacecraft, and planetary exploration systems. "Human space flight beyond Low Earth Orbit (LEO), beyond Earth’s natural radiation shields (the Van Allen belts), is dangerous."
Currently, a human being outside the Van Allen belts could receive the NASA defined “lifetime dose” of galactic cosmic radiation within 200 days. If the Sun spews out a coronal jet of radiation in a solar storm in the direction of the spacecraft, a lethal dose can be received in a few hours. Mars does not have the equivalent of the shielding Van Allen belts, so a Mars base would also need shielding. Until we develop appropriate shielding, probably an intense magnetic field around the spacecraft, human travel, even to the moon, will likely be limited.
"Robotic missions, in the short term, will be limited to the inner solar system," added Fowler aruing the hard realities of manned space travel. "In the inner solar system (within the orbit of Mars), the solar cells can be used to power spacecraft. Beyond Mars, spacecraft power systems rely on radioactive means to create electricity, and we do not currently have a supply source for the needed material. There is a very short supply of Plutonium 238, the radioactive element used to provide electricity for spacecraft going to Jupiter and beyond. We have exhausted the U.S. supply and have been buying it from the Russians. Now they are in short supply and other sources are not currently available."
In a past issue of Scientific American Jim Bell, an astronomer and planetary scientist at Cornell University, and author of “Postcards from Mars,” notes that “…you might think that researchers like me who are involved in robotic space exploration would dismiss astronaut missions as costly and unnecessary.”
But he then he goes on, “Although astronaut missions are much more expensive and risky than robotic craft, they are absolutely critical to the success of our exploration program."
The heart of the debate is this: robotic machines will only do what they are programmed to do; they are not programmed to detect weirdness: the unimaginable, the unknown, the strange non-carbon life that we may have encountered on Mars, for example with the two Viking vehicles, in 1976. Each carried equipment for sampling the Martian soil and miniature chemistry laboratories to test the samples for signs of life.The results these automated labs radioed back to Earth were enigmatic: the chemical reactions from the Martian soil were strange, unlike anything seen on Earth. But they were also unlike any reactions that living organisms would produce.
Ben Bova, the science-fiction author of Titan and The Aftermath, his most recent novels in is his ongoing series about the expansion of the human race throughout the Solar System, points out in an interview that most scientists examining the Viking results, reluctantly concluded that was lifeless: "But the fact is that the landers were equipped only to detect signs of Earth-type life. The chemical reactions observed could have been the results of Martian life. They certainly were not ordinary inorganic chemistry."
The human vs.machine debate is a false construct: robotic unmanned spacecraft are directed by human beings on Earth. Unless disabled by fierce sandstorms, our rovers are in constant realtime communication with their masters at the Jet Propulsion Laboratory, as will the New Horizons spacecraft now heading for Pluto with human monitors watching over it.
Stephen Hawking, world-celebrated expert on the cosmological theories of gravity and black holes who held the Issac Newton's Lucasian Chair at Cambridge University, has strong views on the future of the human species and space trael. At last year's 50th anniversary for NASA. Hawking proposed that the world should devote about 10 times as much as NASA's current budget – or 0.25% of the world's financial resources – to space exploration. Hawking backed the space agency's goals of returning astronauts to the Moon by 2020 and sending humans to Mars shortly after that.
Hawking said that any long-term site for a human base should have a significant gravity field, because long missions in microgravity lead to health issues such as bone loss.
Hawking favors human space exploration, rather than just sending robots to explore space, a position taken by Nobel laureate Steven Weinberg, among others.
Eventually, Hawking said, humanity should try to expand to Earth-like planets around other stars. If only 1% of the 1000 or so stars within 30 light years of Earth has an Earth-size planet at the right distance from its star for liquid water to exist, that would make for 10 such planets in our solar system's neighbourhood, he said.
"We cannot envision visiting them with current technology, but we should make interstellar travel a long-term aim," he said. "By long term, I mean over the next 200 to 500 years." Humanity can afford to battle earthly problems like climate change and still have plenty of resources left over for colonizing space, he said.
"Even if we were to increase the international [space exploration] budget 20 times to make a serious effort to go into space, it would only be a small fraction of world GDP," he said. GDP, or Gross Domestic Product, is a measure of a country's economic activity.
Hawking believes that traveling into space is the only way humans will be able to survive in the long-term. "Life on Earth," Hawking has said, "is at the ever-increasing risk of being wiped out by a disaster such as sudden global warming, nuclear war, a genetically engineered virus or other dangers ... I think the human race has no future if it doesn't go into space."
The problems with Hawking’s solution is that while it may save a “seed” of human life- a few lucky specimens- it won’t save Earth’s inhabitants. The majority of Earthlings would surely be left behind on a planet increasingly unfit for life.
Hawking argued that the world can afford 0.25% of its collective GDP to devote to space colonization. "Isn't our future worth a quarter of a percent?" he asked. The physicist also speculated on the reasons that SETI (Search for Extra-Terrestrial Intelligence) projects have not yet detected any alien civilizations, offering three possibilities: that life of any kind is very rare in the universe; that simple life forms are common, but intelligent life rare; or that intelligent life tends to quickly destroy itself.
"Personally, I favour the second possibility – that primitive life is relatively common, but that intelligent life is very rare," he said. "Some would say it has yet to occur on Earth."
About our new NASA space strategy, Robert Bishop, a specialist in the area of planetary exploration with emphasis on spacecraft guidance, navigation and control currently working with NASA Johnson Space Center and the Jet Propulsion Laboratory on techniques for achieving precision landing on Mars argues that:
"In most ways, humans are now more sophisticated than those that came before us. Unlike the early earth-bound explorers, we are capable of leaving the cradle of civilization and living in space. Yet, 50 years after the launch of Sputnik and the start of the Space Age, we seem to be interminably stuck going in circles around the Earth. Indeed, the second brightest object in our night sky — the International Space Station — has been traveling in a near-circular orbit for years. Why is America so timid? Where is our spirit to explore and create new opportunities?"
Autonomous, self-replicating robots — exobots — are the way to explore the universe, find and identify extraterrestrial life and perhaps clean up space debris in the process, according to a Penn State engineer, who noted that the search for extraterrestrial intelligence — SETI — is in its 50th year.
“The basic premise is that human space exploration must be highly efficient, cost effective, and autonomous as placing humans beyond low Earth orbit is fraught with political economic, and technical difficulties,” John D. Mathews, professor of electrical engineering, reported in the current issue of the Journal of the British Interplanetary Society.
If aliens are out there, they have the same problems we do, they need to conserve resources, are limited by the laws of physics and they may not even be eager to meet us, according to Mathews.He suggests that “only by developing and deploying self-replicating robotic spacecraft — and the incumbent communications systems — can the human race efficiently explore even the asteroid belt, let alone the vast reaches of the Kuiper Belt, Oort Cloud, and beyond.”
Mathews assumes that any extraterrestrial would need to follow a similar path to the stars, sending robots rather than living beings, which would explain why SETI has not succeeded to date.
“If they are like us, they too have a dysfunctional government and all the other problems plaguing us,” said Mathews. “They won’t want to spend a lot to communicate with us.”
It is extremely difficult to broadcast into the galaxy and requires vast resources. Radio signals need to emanate in every direction to fill the sky, and the energy requirement to broadcast throughout space is quite high.
“Current infrared lasers can communicate across our solar system,” said Mathews. “The problem in terms of SETI is they are highly directed beams.”
Point-to-point communications using infrared signaling requires less power, but the signals are extremely directional. If extra-terrestrial beings are using laser-generated infrared signaling, we would never notice their signals because they are so tightly targeted to their destinations.
Mathews suggests that if human exploration is not possible, robots could go where many people do not want to go and do what many do not want to do, not only on Earth, but also in space.To minimize the cost, he suggests that the initial robots be manufactured on the moon to take advantage of the resources and the one-sixth gravity. He notes that we have the technology to create these exobots now, except for a compact power source.
Ultimately, the network of exobots — self-replicating, autonomous and capable of learning — will spread through the solar system and into the galaxy, using the resources they find there to continue their mission. Communicating with infrared lasers is communicating at the speed of light, which is the fastest we can hope to achieve.
“Our assumption in the search for extraterrestrial intelligence is that ET wants to be found,” said Mathews. “But who has energy resources to spend trying to wave their metaphorical hand across the galaxy?”
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