Articles: Solving Flight Problems on MarsAs the rocket blasts the spacecraft carrying the Mars airplane out of the Earth's atmosphere, the Earth's gravity pushes back down on it. It takes a lot of power to work against the force of gravity, also called G-force. Even with powerful rockets, the spacecraft’s path is not straight, but gets curved because the G-forces pull the spacecraft towards the Earth.
The rocket has to fly very fast to escape the Earth’s G-forces. It is very important that the Mars airplane is carefully packed inside so it doesn’t bounce around. It must balance perfectly, or the whole spacecraft could start spinning out of control. When the spacecraft reaches Mars and the aeroshell is sent down, the gravity on Mars will cause it to fall fast and hard toward the planet’s surface. The Mars airplane has to be made from very strong materials or it will break easily under the strain of these G-forces.
Most of the surface of Mars is not protected from space radiation or the harmful rays given off by the Sun. Radiation from space is made of high-speed particles that can damage equipment and cause cancer in living things. That is why we — and the Mars airplane — need protection from the Sun and from space radiation. The Earth’s atmosphere has a global magnetic field and a thick atmosphere that protect us.
Space radiation on Mars can damage the instruments on the airplane. They might overheat and burn, or be totally destroyed. They have to be protected with some kind of shield. Scientists usually use a metal called aluminum. Aluminum is used here on Earth for making lots of things, such as soda cans and aluminum foil. This metal reflects the radiation away from the instruments, a bit like a mirror reflects light. Researchers are also testing new types of plastics and other materials to see if they would make good shields.
The Mars airplane also needs to be protected from the weather on Mars. The hottest it ever gets at Mars’ equator is about 27º Celsius (80º Fahrenheit), and that’s only for a very short time. That’s like a warm spring day on Earth. The rest of the planet is very cold all of the time. It gets well below freezing. In fact, the average temperature on Mars is –63º Celsius (-81º Fahrenheit). These cold temperatures could damage the electronics on the airplane. Then, the instruments might not work properly and the mechanical parts might freeze up. This can be avoided by wrapping parts of the airplane in warm, insulating material. There could also be a heating system on board to stop things from freezing. A heating system needs to have energy to make it work. This could require carrying more fuel, or using solar panels to make electricity.
Just like Earth, there is an atmosphere around Mars. In some ways, the atmosphere on Mars is similar to our atmosphere. In other ways it is very different. These differences will affect how well an airplane can fly on Mars.
The atmosphere on Mars is much thinner than on Earth. This means that there are less air molecules for the wings to create lift. The wings have to be bigger to make more lift. If the airplane uses propellers, the blades need to be bigger on a Mars airplane than they would be on an Earth airplane to make the same amount of thrust and lift as on Earth.
The force of gravity is lower on Mars. This means that the airplane won’t weigh as much on Mars as it does on Earth because there is less force pulling the airplane toward the planet. Still, if the airplane carries a lot of equipment, the wings will have to be larger to create enough lift.
There is also a lot less free oxygen in Mars’ atmosphere than there is on Earth. Most Earth airplanes use oxygen from the air to help them burn the fuel in their tanks. The Mars airplane needs to use another form of fuel, take oxygen with it, or carry technology that can separate oxygen from the carbon dioxide atmosphere. Oxygen tanks or other types of fuel, such as batteries or solar panels, add to the weight of the airplane.
Since Mars is at least 35 million miles away from Earth, the airplane
is going to have to fly by itself. Earth is too far away for radio signals
to control it like a remote-controlled car. If the airplane has a computer
onboard, flight moves can be programmed into the computer before it
leaves Earth. Then, the computer can guide the airplane, depending on
what problems it faces. This is called autonomous flight, or flying
without a pilot. If the airplane flies in bumpy air on Mars, the computer
can help it decide what to do. It can also help the airplane fly to
wherever the scientists want it to go.
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Editor: Brian Day
NASA Official: Liza Coe
Last Updated: September 2005
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