Almost three decades after landing on the moon, NASA is again seriously testing the idea of manned space flights beyond Earth's probable circumpolar orbit. This time, the most likely target is Mars
In his office at the Jet Propulsion Laboratory (J PL) in Pasadena, California, physicist Mark Adler holds a slide up to the light. He points to a timetable detailing NASA's ambitious plans for Mars exploration. The schedule shows missions that will be launched to study the Martian soil and its atmosphere, analyze rock samples, and even bring rocks back to Earth. Then Adler points to the year 2014, where the schedule ends with its amazing climax: a manned mission to Mars.
Almost three decades after landing on the moon, NASA is again seriously testing the idea of manned space flights beyond Earth's probable circumpolar orbit. This time, the most likely target is Mars. The cost of a manned mission to Mars that will last two and a half years, which was once estimated at hundreds of billions of dollars, is now estimated at only $20 billion, or about $2 billion per year for 10 years. This could fit within NASA's budget constraints, the agency currently spends a similar amount on the International Space Station.
And a recent feasibility study by NASA's Johnson Space Center in Houston argues that Adler's schedule is too pessimistic. Johnson engineers now say they can send astronauts to Mars in less than ten years. "We are building the infrastructure," says Adler, the architect of the program prepared by the Jet Propulsion Laboratory for exploring Mars using robots, before launching the manned mission. NASA, which waited 21 years after the Viking mission in 1976 to return to the Martian soil with Pathfinder, has now established an assembly line for spacecraft to Mars. As the Pathfinder rover raced across Mars, engineers were already planning the Mars 9 mission that launched a month ago. Missions are also planned for the next launch opportunities in 2001 and 2003 (fuel requirements are lowest when the spacecraft are launched when Earth and Mars are closest to each other, such a relative situation occurs approximately once every 26 months). Subsequent missions will collect data that will help NASA decide what technologies it needs to send humans to the icy red sands of Mars.
NASA's interest in Mars was rekindled in 1989, when President George Bush called during the celebrations marking the 20th anniversary of the moon landing to send a manned mission to Mars. NASA needed no further encouragement. She sprang into action, and ninety days later presented a stunning plan to send astronauts to Mars. The mission included assembly garages and docks in a peripheral orbit in space, huge bases on the moon and a fleet of means of transport, as well as spaceships for interstellar travel the size of "Galactica" from the well-known TV series.
NASA estimated that the industrialization of space predicted in its 90-day report would require 30 years to achieve and would cost a staggering 540 billion dollars. This was a completely unrealistic goal. This excessive proposal was soon dropped; And the Mars enthusiasts inside NASA and outside tried to come up with a proposal for an alternative mission, which could be accomplished at a reasonable price. The result, based on work done in the mid-XNUMXs in the Johnson Space Center's Research Operations Office, was something called the Mars Reference Mission.
When work on the mission was completed, Johnson Center engineers claimed they could complete it for about $50 billion. But they continued to change the initial draft, reexamining every assumption and doing as much as possible to cut costs without imposing unacceptable risks. Last summer, Johnson Space Center engineers reported that they had cut the cost of the reference mission in half.
They achieved this in part by redesigning the mission to eliminate the need for a huge new launch vehicle. This, in turn, eliminated the need to build a new and particularly expensive launch facility at Cape Canaveral. The engineers also adopted some of the ideas of a former Lockheed Martin engineer who did more than anyone else to spur creative thinking about planning a mission to Mars. The irrepressible Robert Zubrin, who now heads his own aerospace engineering company (Pioneer Astronautics, of Lakewood, Colorado), planned a mission to Mars that he claimed would be cheaper and faster than NASA's.
Zubrin has been striving for Mars with almost religious zeal since 1990. He is now raising money to establish a base at the Pole, where a prototype of a living module on Mars will be installed and tested. He intends to launch a privately funded multi-purpose payload to Mars in 2003.
And last summer he had his first meeting with a group he founded, called the "Mars Association", whose goal is to build public support for the idea of a manned mission to Mars. Zubrin's mission, which he calls "Direct to Mars," differs from NASA's reference mission in a number of ways, but NASA admits that it has latched onto some of Zubrin's ideas. In fact, NASA has now contracted with Zubrin to examine some of those ideas for possible incorporation into NASA's final plan.
Zubrin's most important contribution was to show that astronauts on Mars "could live there". This is an amazing idea, because the surface of Mars is colder, drier and much more barren than anywhere on Earth. Even so, there are many resources out there for the astronauts to tap into to meet their life support needs. Even more amazing, as Zubrin showed, is the fact that Mars can provide fuel for the astronauts' journey back to Earth.
NASA's reference mission to Mars relies as much as possible on existing technologies. The temptation to reduce costs in the latest version of the plan was to reduce the weight that must be lifted into space from 400 to 200 tons.
The basic strategy, says Kent Josten, chief engineer in the Office of Research at the Johnson Space Center, is what's called a split approach. It's different from the Apollo moon mission, where a giant rocket launched everything to the moon at once. The attribution mission to Mars, on the other hand, is built on the template used by military commanders in war. "They call it frontal deployment," says Josten. "It means that before you send your forces, you make sure that your materials are placed as far forward as possible, so that you don't end up in a situation where the forces have already arrived and the materials are not there."
"We are looking at when we want the team to reach Mars," continues Josten. "Twenty-six months before, we send as many critical materials as possible, and make sure that they got there and that they are working properly, before we send the team."
The mission will begin with the launch, probably in 2011, of two rockets that will deliver purposeful payloads to Mars. One multi-purpose payload will be the vehicle that will allow a return to Earth, which will be put into a peripheral orbit around Mars. It will remain there until the astronauts are ready to use it for their journey home. The second multi-purpose payload will include the ground dwelling and its power systems, a fuel production system, rovers and other research equipment, and the vehicle for taking off from Mars. "After this thing lands, it will start producing fuel for the launch vehicles, fuel for the vehicles for loitering, as well as air and water, mainly from the atmosphere of Mars," says Josten.
It will take two years before the team gets there. At that time, the living pavilion – which may be inflatable, a recent innovation designed to save weight – will be erected on the surface.
The fuel production system will report when it has finished producing a sufficient amount for the launch vehicles. And they will also verify the readiness of the entire base on the surface of Mars before its intended inhabitants are sent on their way. If all goes well, a six-person team will be launched at the next opportunity of the appropriate launch window, in 2014. Their mission will last two and a half years - about six months on the way to Mars, about 500 days on its surface, and about six months back.
"It's a long mission - it's different from anything we've done before," says Josten. "But we are only in space for six months at a time. After that we are on Mars, where we have some shielding from radiation and access to resources. A six-month stay in space is something we already have experience with. What we need to do is learn how to live on Mars."
During their long stay, the astronauts will have to maintain an ambitious scientific agenda, which will probably also include a deep drilling project to search for life below the surface. But following the stunning success of the Pathfinder mission in 1997, some critics wonder why Mars cannot be sufficiently explored with unmanned instruments. "I think we're going to find out pretty quickly the limits of what robots can do on Mars," says Josten.
“Engineers can only pack a limited amount of intelligence into a lander the size of Pathfinder, and the great distance between Earth and Mars makes it impossible to send immediate commands to the robot. A thorough search for life on Mars, and a thorough examination of the geology of the planet, will require humans who can roam over a large area and follow clues and sensations in a way that machines cannot do," says Josten.
When the astronauts explore Mars, all the air and water they use will be recycled. The plant for the production of propellants, while not producing fuel, will be used to create water and oxygen for the various life support systems for the crew members. "You can't jump out and come home any moment you want, and you can't get supplies from Earth any moment you want," says Justin. "After you send them there, they will have to rely on themselves."
At the end of your stay, the astronauts will use liquid oxygen and methane produced on the surface of Mars to fuel their launch vehicles. The liquid oxygen will be taken from carbon dioxide, which is the main component of the Martian atmosphere. Methane requires the addition of a small amount of hydrogen, which is imported from the Earth. The launch vehicle will carry the crew members to rendezvous with the return vehicle to Earth, which was previously placed in a peripheral orbit around Mars. They will fly this spacecraft back to Earth.
To reduce the risks, NASA relies on a smart program that will launch several missions to Mars in a staggered manner. Before the first crew of astronauts went out there. The first two purpose-built payloads for a second manned mission will already arrive at Mars with a second return vehicle to Earth and a second surface habitat.
"Crew members will have two sets of everything, in case they run into problems," says Josten. It is possible to plan the second living pavilion in such a way that it can connect to the first, to increase the volume available to the staff. Another idea is to start growing food on Mars using the second pavilion as a greenhouse for growing plants.
While NASA was planning the reference mission, it was also working on the launch vehicle needed to launch the mission. Johnson Space Center engineers initially thought they would need a giant rocket capable of launching a 200-ton payload into Earth orbit. This is about twice the capacity of the Saturn 5 rocket used in the Apollo mission to the moon. In the latest version, the requirement was reduced to only 80 tons.
This means that NASA no longer faces the expensive and complicated challenge of designing a completely new launch vehicle. "We now have a launch vehicle that is capable of putting 80 tons into orbit, and we use it about once a month," says Josten. This is the space shuttle, of course. Its carrying capacity is only about 20 tons, but when it is loaded, the weight of the makpet reaches about 80 tons.
"You can think about replacing the scope with a multi-purpose charger that you need, and you actually have an existing system that can almost do what we want from it." This new launch vehicle is called Magnum. Like the Space Shuttle, the Magnum will have a large fuel tank to which two rocket boosters are attached. But instead of the circle of the space shuttle there will be a long cylinder that will be mounted on top of the fuel tank. This cylinder will store inside it the elements of the mission to Mars. The Magnum will put the components of the Mars mission into a low orbital orbit around the Earth, similar to the orbits flown by the Space Shuttle. There they will be connected in preparation for their journey to Mars.
In one scenario, the perfect package won't fly directly to Mars. Instead, NASA will use a spacecraft "tug" to slowly pull a purpose-built payload destined for Mars into a much higher orbital orbit around Earth. From there, just another small push is needed to launch the purpose-built payload on its way to Mars. The design details of the space tug are regularly updated. The latest plan talks about a spacecraft with a solar-electric ion engine, but NASA is also considering chemical, electric nuclear, thermal nuclear and plasma propulsion systems.
After the space tug brings the mission payload into high orbital orbit around the Earth, it will detach from it and descend back to connect with another payload.
The high orbital payloads will be launched on their way to Mars by briefly firing a conventional chemical rocket engine. The main advantage of ion engines is that they are very efficient, but they do not provide much thrust. The journey from low orbit to high orbit around the Earth takes about six months. That's fine for unmanned mission payloads, but what about the astronauts, after the mission payloads with the second habitable cabin reach high orbital orbit, "you quickly send the crew up in a smaller system," says Josten. "It's a bit like a small boat sailing back and forth to a large ship anchored far from the shore." Zubrin does not support the use of advanced propulsion systems such as ion-solar engines in the early missions to Mars, because he fears that the development of such systems could delay the entire mission. Columbus also did not wait for the development of transatlantic ships before he set out to discover the New World, says Zubrin. "After he did that - after people knew there was some place worth going to - then the development of three-masted ships, steamships, passenger ships for crossing the ocean and the Boeing 747 began. Destinations are what drive the development of means of transportation.
Zubrin's "Direct to Mars" mission is smaller and lighter than NASA's. He's talking about a team of four, not six. It will begin in 2005 with the launch of a tool similar to the Magnum. The launcher will carry a spacecraft for the purpose of returning to Earth, which will land directly on the Martian soil, without stopping in a peripheral orbit around the Earth. A direct flight, says Zubrin, would eliminate the need for a space tug or any other craft in orbit.
Zubrin's mission saves weight by using a smaller habitation cabin, which NASA thinks is too small. "You can't put them in a capsule the size of an Apollo spacecraft for six months," says Josten. NASA's mission talks about a large capsule, which is too heavy for direct flight.
According to Zubrin's plan, a second spacecraft to return to Earth will be sent to Mars two years after the first. As in NASA's plan, it will be used as a backup, or it can be used to bring back the second crew to be sent to Mars. A few weeks after the second return spacecraft is launched, a four-person crew will be sent to Mars, also on a direct flight from Earth to the Martian soil. After about 500 days on the surface of Mars, the crew will fly back directly to Earth, using fuel produced on Mars, without stopping in orbit around Mars.
Zubrin's mission requires only two launches, while NASA's requires three. This makes NASA's mission inherently more expensive. NASA's plan depends on having a rendezvous in orbit around Mars, which is critical to the success of the mission, as Zubrin points out. On the other hand, Zubrin's mission requires the production of much more fuel on Mars - in sufficient quantity to return the astronauts home, and not just to get them into orbit around Mars.
While most of the technology needed to reach Mars is already available, several important challenges remain. "We really want to get a lot of information back from the space station," says Brett Drake, who leads manned mission research in the Johnson Space Center's Office of Research. "One of the main things is how the body adapts to the absence of gravity." Life support systems and other technology can also be tested on the space station. However, NASA is not waiting for the completion of the space station to begin its research.
The plans for a manned mission to Mars will progress beyond the planning stage only in two years, after the launch of the 'Mars - '2001 mission, an unmanned spacecraft that will carry a scale model of the fuel production system. In the unmanned mission planned for 2003, NASA is considering conducting studies that will test the possibility of "trapping in the air". NASA wants to find out if it can put a spacecraft into orbit around Mars by using atmospheric friction to slow it down, instead of firing a rocket engine. Air capture will reduce the amount of fuel needed for the Mars mission. NASA may also use the 2003 mission to generate methane on the Martian soil and test methods for more precise landings. Pathfinder was designed to land somewhere within an "error ellipse" of 300 km. For a manned mission, the error ellipse would need to be about 3 km in size, Drake says.
Zubrin will also be busy preparing for the future. In his activity with the recently established "Mars Association", he hopes to collect a million dollars for the purpose of building a model of a living pavilion for Mars in the polar region in Canada. "We want it to be ready in 2000. If we manage to do that, we can raise maybe 5 to 10 million dollars to fly a multi-purpose payload to Mars as a hitchhiker in 2003," he says. It is possible that such a launch will be carried out by the European spacecraft planned to fly to Mars. One idea for the purpose-built payload is a camera mounted on a balloon, which would drift through the Martian atmosphere and send back bird's-eye pictures of the planet. Zubrin's group hopes to eventually raise enough money to fly its own robotic mission to Mars. Nearly 30 years after the first moon landing, it now seems that interstellar research has once again become a realistic possibility. "It's definitely going to happen," says Drake. "It's just a matter of time."
