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How long does it take to get to mars?
In our solar system, Mars is the fourth planet from the sun. On a clear night sky, it is one of the most luminous objects and clearly visible to the naked eye as a brightly-lit red star. Earth and Mars come to their closest point, known as ‘opposition,’ every 2 years or so. At this time Mars is only 55 million km from Earth. This is also the time when varied space agencies send their spacecraft to Mars.
The total time taken to complete the journey from Earth to Mars ranges between 150 to 300 days. It is dependent on the alignment of Mars and Earth, the speed of spacecraft launch, and the total distance between the two planets at that point in time. However, the travel time is largely dependent on the amount of fuel that can be burnt to get to the Red Planet. More fuel means a shorter journey time.
History of trips to Mars
The first spacecraft to travel from Earth to Mars was the Mariner 4. It was launched in 1964 on November 28, and completed the journey in 228 days. Similarly, the total flight time for Mariner 6 was 131 days, while the Mariner 9 took 167 days.
Over the last fifty years involving Mars exploration expeditions, the above flight times, i.e., an estimated 150 to 300 days, have held steady with regularity.
The reasons for the lengthy travel time to Mars
Mars is only about 55 million km away from the Earth. The spacecraft to Mars travel at speeds of more than 20,000 km/hr. Thus, according to simple mathematical calculations, the entire journey should only take around 115 days. However, it is not so. This is due to the fact that Mars and Earth continuously orbit around the sun. It is not possible to just aim at the Red Planet and launch a spacecraft, because by the time it reaches that point, Mars would have made its way to some other point in its orbit around the sun. Hence, a spacecraft needs to be launched in the direction of a point where Mars will be after the passage of relevant time.
Availability of fuel is another factor. If unlimited quantities of fuel were available, then the spacecraft could be pointed at Mars, the rockets could be fired till the halfway mark, turned around, and later decelerated for the final half of the journey. In such a scenario, the total travel time would be a fraction of the time taken currently. This is however not possible due to the lack of unlimited fuel resources.
Getting to Mars with minimal quantities of fuel
The engineers at NASA use a travel maneuver called a Minimum Energy Transfer Orbit, or a Hohmann Transfer Orbit, to launch a spacecraft to Mars with as little fuel as possible. This method was first proposed and later published by Walter Hohmann in 1925.
Instead of directly pointing the rocket at Mars, this technique involves boosting of the spacecraft’s orbit in such a way that it follows a bigger orbit around the Sun than Earth. That orbit will ultimately intersect Mars’ orbit at the precise moment that Mars appears at that point. Thus, traveling to Mars with minimal fuel requires more time to increase the orbit, which raises the total travel time.
Varied ideas to reduce the total journey time to Mars
Some of the proposed methods to decrease travel time to Mars are listed below:
- Antimatter Rocket: It may be one of the most out-of-the world proposals for travelling to Mars. Antimatter is produced in particle accelerators and may possibly be the densest fuel available currently. The meeting of antimatter atoms and matter atoms cause them to become pure energy. Only 10 mg of antimatter is required for a Mars mission in just 45 days. However, the cost of creating even that tiny quantity of antimatter is around $250 million.
- VASIMR/Variable Specific Impulse Magnetoplasma Rocket: This technology involves an electromagnetic thruster that ionizes and heats up a propellant with the help of radio waves. This process produces an ionized gas known as plasma which can be thrust magnetically at high velocities from the back of a spacecraft. Franklin Chang-Diaz, a former astronaut is working to develop this technology and a prototype may soon be fitted on the International Space Station so that it can sustain its altitude over Earth. VASIMR rockets may lower the travel time from Earth to Mars to around five months.
- Nuclear Rockets: Nuclear rockets work on the principle of heating up a working fluid such as hydrogen to extreme temperatures within a nuclear reactor, and later blasting it out from the nozzle of a rocket at elevated velocities so as to produce thrust. As compared to chemical rickets nuclear fuels are intensely energy dense, thereby allowing a higher thrust velocity with lower amounts of fuel. Nuclear rockets may lower the travel time to around seven months.