According to NASA’s Space.com, the 40th anniversary celebration of the first human moon landing has concluded, but whether NASA can send humans to Mars remains a mystery.
Bret Drake, a researcher at the Lunar and Mars Exploration Study Group at NASA’s Johnson Space Center in Houston, said: “We still view human exploration of Mars as the ultimate goal for the future. Stepping on another planet may involve the greatest risks, but it is also the most historically significant event.”
Current technological levels may have just reached, or may still fall far short of, the technical requirements for a manned mission to Mars. Therefore, a manned mission to this red planet remains a massive challenge. However, NASA remains committed to the Mars expedition, and new ideas regarding Mars exploration continue to emerge. Drake said: “Mars is a place we have long yearned for.”
How to Get There
It takes approximately 180 days to travel to Mars. To date, NASA has studied two propulsion options for the journey: nuclear thermal rockets and chemical engines. Nuclear thermal rockets are developed based on designs from the 1960s and 70s; they use a nuclear reactor to heat gas to very high temperatures, using the hot gas exhausted from a nozzle to generate thrust and launch the rocket.
Drake said: “This is a high-performance propulsion system. We believe it is very safe and will not produce radioactive materials during launch, but it is a nuclear system. Chemical engines are similar to those used by the Space Shuttle, using liquid oxygen and liquid hydrogen as fuel. This is a very familiar technology, but its efficiency is not as good as that of nuclear thermal rockets.”
To reach the Martian surface, NASA envisions using an aerodynamic lander and using thrusters to assist its descent. The ascent vehicle, which would return astronauts to space and send them back to Earth over a 6-month period, would use a mixture of methane and liquid oxygen as fuel. Drake said: “The oxygen in the Martian atmosphere exists in the form of carbon dioxide, so you can use Mars’s own resources to manufacture oxygen.” They plan to send as much cargo as possible to the red planet before the astronauts arrive. Drake said: “Before we send astronauts there, we must ensure everything is functioning properly. A Mars mission is not like a Moon mission; you cannot return to Earth at any time. Once they are sent there, they may have to stay for several years.”
According to NASA’s recent assessment results, a manned mission to Mars must be able to send a mass approximately twice that of the International Space Station into space, which is about 1.76 million pounds (800 tons). NASA intends to use the “Ares V” rocket to launch this equipment. The “Ares V” is the most powerful rocket ever designed, capable of sending approximately 414,000 pounds of payload into Low Earth Orbit in a single launch. Drake said: “We will try to minimize the number of assemblies. The Ares V’s ability to push very heavy payloads will make automated rendezvous and docking in orbit much simpler.” Before beginning the journey to Mars, astronauts will ascend into space aboard an “Ares I” rocket.
Drake said: “Humans entering space can gain a wealth of valuable experience; they can make timely decisions based on what they see and hear. This is very difficult to achieve with robots.” The space agency can send the items astronauts need on Mars in advance. Drake said: “You can also use existing resources on Mars to produce and store oxygen before the astronauts and propulsion systems arrive.”
More Crew, Longer Stay
NASA envisions a Mars mission being carried out by a crew of six. Drake said: “Technical arrangements dictate the need for this many people: a commander, a scientist, an engineer, a medical officer, etc., along with cross-training for role rotation. They must be knowledgeable but specialized.”
Recently, NASA has envisioned letting astronauts stay on Mars for about 500 days. Drake said: “It is very important for astronauts to act according to circumstances because, due to the vast distance between Earth and Mars, it takes about 40 minutes for a command to be transmitted from Earth to Mars. These astronauts cannot receive resupplies; they can only rely on things sent to Mars in advance or things they carry with them. Therefore, when something malfunctions, they must be able to fix it. They must have the capacity for self-sufficiency.”
To survive the flight, air and water must be fully recycled. Drake said: “Regarding air regeneration and water recycling, we are currently learning a lot from the International Space Station. A major advantage of Mars is that its atmosphere contains carbon dioxide, so we can use these resources to obtain the oxygen and water the astronauts need. Speaking of food, we are looking for smaller systems, such as ’salad machines’ that can produce food for the astronauts. Fresh food is not only nutritionally rich but also beneficial for psychological health. Fresh tomatoes can indeed improve one’s psychological state.”
Facing Massive Physical and Mental Challenges
For a few individuals to stay in a space environment with lethal risks for about two and a half years is indeed a significant psychological challenge for astronauts heading to Mars.
Drake said: “Russia is currently conducting experiments, hoping to gain a better understanding of the behavioral science aspects of a Mars mission. Studying other exploration activities in remote areas is also helpful, such as trips to Antarctica or underwater; all of these can provide feedback on human behavior for the selected astronauts.” Another aspect of concern for astronauts staying on Mars is the dangerous radiation produced by the sun and deep-space cosmic rays in the form of high-energy particle bursts. Drake said: “Hydrogen or water are the best radiation shielding materials because water is rich in hydrogen.”
NASA envisions that cargo sent to the red planet before the astronauts arrive could produce water, which can serve as a protective barrier after the astronauts arrive. During the journey to and from Mars, special devices should be installed on the spacecraft so that astronauts can spend most of their time in areas surrounded by water and food. However, a “high-energy particle burst shelter” on the spacecraft is a critical component for blocking lethal radiation.
To date, any possible date for a Mars mission has not been determined, but countries like the United States and China have always been very interested in landing on Mars. Drake said: “This is the next step for humanity to understand and expand our existing frontiers. We view human exploration of Mars as an international cooperative project. Exploring Mars is unlikely to be limited to a single country, as it is a goal for the collective effort of the entire world.” (Xiao Wen)
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