In order for a manned mission to Mars to be carried out, many preliminary steps will have to be taken. We will have to explore Mars. We can do this with probes amd robots. Next, we will have to build the ship that will to travel to Mars. The ship will have to be assembled in space. This will require the use of a Space Station, a Heavy Lift Vehicle (HLV) to carry supplies, and launch vehicles to send people into space. While the ship is being assembled, we will have to develop technology to protect the people traveling to Mars. We will have to find a way for the ship to get from earth orbit to Mars orbit, a way for the ship to slow down, and a way for the ship to return from Mars and get back to Earth. However, the biggest problem with Mars exploration is money. This will be an incredibly difficult problem to solve.
We must explore Mars in great detail. We can do this with probes and robots. Two Mars missions have already been scheduled. The Mars Pathfinder is the first of these two. The spacecraft is scheduled to arrive at Mars on July 4, 1997. The purpose of the new Pathfinder mission is to demonstrate an inexpensive system for cruise, entry, descent, and landing on Mars, this according to the project scientists. The Mars lander carries a microrover, scientific instruments, and cameras. The lander will function as a weather station on the surface. The rover will examine the rocks and soil nearby the lander. More information about the Mars Pathfinder can be found at The Jet Propulsion Laboratory's (JPL's) Mars Pathfinder Home Page. The Mars Global Surveyor (MGS) is the next Mars mission. The MGS is a small orbiter scheduled to be launched in November of 1996 to study the surface of Mars. The MGS is the first of a series of missions to Mars in a decade-long program of Mars exploration. The decade-long prgram calls for a new launch every two years, when Mars comes into alignment with Earth. This is scheduled through the year 2005. For more information on the Mars Global Surveyor, explore JPL's Mars Global Surveyor Home Page. Robotic missions are currently being planned for Mars. They should lead to a greater understanding of the Martian environment and the early history of Mars. Each Mission will give us more information about the atmosphere, the surface, and the subsurface of Mars. Current research for these robotic missions are being done by the International Mars Exploration Working Group (IMEWG). They plan to launch a total of 21 missions in the next decade.
We will need the repeated use of launch vehicles to build the Mars vessel in space. Currently the only launch vehicle we have is the Space Shuttle. The big problem with the space shuttle is that it takes hundreds of people and costs a lot of money to launch it. However, recently an alternative has been invented. The McDonnell Douglas Delta Clipper-Experimental (DC-X) is currently being tested. The special thing about the DC-X is that it is a reusable launch vehicle (RLV). A launching of the DC-X costs a lot less and takes a lot fewer people than a launching of the Space Shuttle. More information about the DC-X can be found at the McDonnell Douglas Home Page, "The RLV Home Page", and The DC-X Home Page (under construction)
We will need a Space Station to carry out the Mission. The only space station currently in orbit is the Russian's Mir. If we are to use Mir, the Mission will have to be done jointly with Russia, which will have to be done anyway because of money problems. Space Station Freedom is being planned by the United States. Money problems may prevent Space Station Freedom from happening. Another possibility is a lunar base.
A Heavy Lift Vehicle (HLV) will be required for the Mission. The HLV will have to lift 150 to 250 metric tons into low earth orbit. Right now there is a great lack of heavy-lift capability. Solutions to this problem are being researched. One solution is the Russian Energia vehicle. However, it is currently not operational. The Energia could be used in the construction of a lunar base and in transporting materials and crew to Mars. Another possibly is to revive the Saturn 5 booster that sent astronauts to Apollo. This was recommended by the White House Synthesis Group three years ago. The Titan booster, the next most powerful, is another possibility.
Problems which humans might encounter on a mission to Mars are radiation exposure, microgravity exposure, and a great deal of stress. Heavy ion impacts caused by solar activity and cosmic rays will cause a biological hazard. Experiments on radiation are currently being carried out. The radiation hazards aren't thought to be a major problem, but they need to be carefully considered when Mars transport vehicles are built. Microgravity exposure can cause physiological changes such as muscle atrophy, bone mineral loss, and heart problems. Research is being done on this problem at the Ames Research Center. A Mars Mission of two or more years will place the crew in a stressful situation, unlike any that a person has yet experienced. Extended stays in the Antartic and on Mir have offered insight into this problem. An eighteen month stay is being planned on Mir in the future. .
The chemical rocket has been the most-used propulsion technology in the history of space travel. The way that probes such as Viking were sent to Mars was to use a chemical rocket for instant thrust, and then to coast to Mars for the rest of the way. However, this way is very slow and takes about 200 days. Two new kinds of propulsion have been explored in the past. These are ion rockets and nuclear rockets. Nuclear rockets will not be around for decades, but the ion rocket might be available in the near future. The ion rocket only produces a small amount of thrust at a time, but it keeps producing thrust constantly, making it faster for long-distance travel than the chemical rocket. Another invention that has been explored is the Solar Sail. This works by employing the mechnical pressure of light for thrust. The main advantage of the sail is that it doesn't require any fuel to operate it. The ideal way to get to Mars would probably be to use a booster to get the spacecraft started, and then use a solar sail to travel to Mars.
Braking is another problem to deal with. One possible solution is aerobraking, the concept of using planetary atmosphere to slow down a spacecraft. Aerobraking has been demonstrated by the Magellan spacecraft on Venus, and has been proposed for the Global Surveyor and Pathfinder missions. The Pathfinder is supposed to aerobrake in the Martian atmosphere using an aeroshell and parachute, and then use airbags to cushion its landing. Aerobraking may not be practical with a large spacecraft such as the one that is needed for a manned Mars mission.Using ion or chemical engines to brake is another possibility. Coming back to Earth, a solar sail could be used to slow down.
Fuel is a costly problem for the Mars mission. Ideas to solve this problem have been presented. One idea, proposed by the Lawrence Livermore National Laboratory in California, is to make an orbiting electrolyzing plant which produces cryogenic fuel (liquid hydrogen and oxygen), and possibly a lunar gas station. Another idea, proposed by Martin Marietta, is to make rocket fuel by using carbon dioxide from the Martian atmosphere and hydrogen from earth using an unmanned vehicle with a miniature chemical plant inside its landing stage. A solar sail would cut down the amount of fuel needed.
The biggest problem with a Mars mission, by far, is money. The leading nations of the world are expressing great economic difficulties. NASA fundings is getting cut more and more each year. Many ways to save money are being researched. I have already mentioned some of them, such as making rocket fuel from Martian atmosphere and using two new cheaper inventions that haven't been fully tested yet, the DC-X and the solar sail. The NASA $300 billion 30-year plan costs too much money. A plan by Lawrence Livermore cost $10 billion dollars over 8 years. This plan however has taken much criticism from other organizations chiefly the "Johnson Space Center." The United States cannot afford to carry out a Mars mission alone. The Mars mission will have to be an international effort. The United States cannot possibly afford tens of billions of dollars for a Mars mission. Also, a Mars mission may require the use of Mir, if Space Station Freedom does not come through.
One last problem is that many people of the United States are opposed to the space program. People opposed to a Mars mission find it too costly and impractical. There are arguments to this however. When $24 billion was spent on the Apollo program, most of the money went to high-technology jobs that made the United States competitive in the world market. Since the Apollo program, our exports have declined. A manned mission to Mars will provide enhanced understanding of the Martian enivironment, refined planetary models, and a test bed for human expansion in the solar system. Space is all we have left to explore, except for the sea bottom possibly. A trip to Mars within the next few decades is still possible.